2022-12-14: How Can Matter Be BOTH Liquid AND Gas?
- 16:40: The answer is almost certainly unfortunately no. Quasiparticles require some sort of non-elementary field to exist in.
- 16:48: In other words, they exist in fields that arise from a volume being filled with matter.
- 16:53: Dark matter suffuses the near-vacuum of space, where we mostly just have the elementary quantum fields.
- 17:00: Excitations in those fields are proper elementary particles, not quasiparticles.
- 17:24: ... as quasiparticles by separating the poles of a regular dipole magnetic field, for example by careful manipulation of spins in a crystal ...
2022-12-08: How Are Quasiparticles Different From Particles?
- 09:05: ... zero, which in turn creates many cool interactions with electromagnetic fields, like levitating magnets, which you can use to make super fast ...
- 13:28: ... in that lattice, or skyrmions, which are localized, stable topological field configurations sort of like knots - all very important for the emerging ...
- 14:20: After all, the elementary particles like electrons, photons, and quarks are just excitations in the elementary quantum fields.
- 14:27: But a field is just some property that can vary over space.
- 14:32: Another field could be the number of electrons in the valence shell of a block of silicon.
- 14:39: And it turns out that any field, elementary or not, will give rise to particles as long as that field has quantized energy states.
- 14:47: A crystal lattice supports many fields - the quantized number of valence electrons, or the many quantized vibrational modes in its bonds.
- 15:11: All part of the magnificent complexity emergent from simple fields spanning space time.
2022-11-23: How To See Black Holes By Catching Neutrinos
- 01:03: They report seeing neutrinos produced in the colossal magnetic fields surrounding a black hole with the mass of 10 million Suns.
- 09:26: ... know that AGNs have powerful magnetic fields because in many of them we see jets of high energy particles blasted out ...
2022-11-09: What If Humanity Is Among The First Spacefaring Civilizations?
- 18:50: ... implied by this interpretation is equivalent to standard quantum field theory, with the time-reversed signals corresponding to negative ...
2022-10-26: Why Did Quantum Entanglement Win the Nobel Prize in Physics?
- 15:49: There was the one about using the Sun’s gravitational field as a lens to take pictures of distant planets.
- 19:16: ... in general a lot of problematic features appear in quantum field theory that have to be removed by hand - for example, various ...
2022-10-19: The Equation That Explains (Nearly) Everything!
- 01:33: ... to make that the case. That term turns out to be the electromagnetic field. ...
- 06:57: ... we have the photon field which is usually represented with a capital A, this is the field that ...
- 07:27: ... is where these mu/nu symbols come from. The kinetic energy of the field in one direction may depend on what is happening in the other direction, ...
- 07:51: ... particles, or things like that Next we do something similar for the fields of the other two forces, we also need their kinetic energy in every ...
- 09:24: ... in the Lagrangian represents. The psi is the wavefunction of the fermion fields. Strictly speaking there are 12 fields for the 12 kinds of fermions we ...
- 09:45: ... We have a derivative, which as we mentioned tells us the energy of the field as it changes, but we also have this part with the field of the bosons. ...
- 10:36: ... each field is preceded by a new symbol which represents the charge that field ...
- 11:57: ... by the Lagrangian so far are massless. To add mass we need the Higgs field - and that’s what the rest of the Lagrangian deals with. We have ...
- 12:14: This term is like the previous - fermions interacting with a bosonic field, but now that’s the Higgs field, represented by this Phi.
- 12:39: ... hermitian conjugate tells us how antimatter picks up mass from the Higgs field, and it's pretty much the same as regular matter, as far as we ...
- 12:52: ... We have another one of these derivatives - D, now applied to the Higgs field. It tells us how that field changes in space and time and how it ...
- 13:07: ... the last term refers to the potential of the Higgs field. This is like the kinetic terms for the other bosons, but now just for ...
2022-10-12: The REAL Possibility of Mapping Alien Planets!
- 01:25: ... the exoplanet are bent inwards by the Sun’s gravitational field to all come together. Forget about a New York sized telescope - at ...
- 04:12: ... know what also bends light? Lenses. So a gravitational field can also act like a lens, although admittedly a kind of crappy ...
- 04:36: ... like these stretched out galaxies seen through the gravitational field of a giant galaxy cluster. If the alignment is ...
- 06:05: ... to do it with the very clean, well-understood gravitational field of our Sun. All we need to do is get our telescope to ...
- 10:07: ... regular lens creates a focal point, the Sun’s gravitational field creates a focal line, starting at 550 astronomical ...
- 15:45: ... other detectors. These collect data a little off the field of the primary observation. Sometimes these happen to land on a ...
- 18:29: ... tiny patch of space, and that can change the way the quantum fields behave - including raising the fine structure constant. ...
2022-09-28: Why Is 1/137 One of the Greatest Unsolved Problems In Physics?
- 02:36: ... separated slightly by their interaction with their own orbital magnetic fields. ...
- 06:29: The more chance of interaction between the electron and electromagnetic fields, the more of an EM disturbance each electron will make.
- 07:16: ... energies right after the Big Bang, the coupling constant for the EM field - which was then joined with the other forces, would have been ...
2022-09-21: Science of the James Webb Telescope Explained!
- 08:49: ... classic example is the Hubble Ultra Deep Field, which is a million second exposure that Hubble took of one apparently ...
- 09:07: JWST will also do deep fields.
- 09:36: These arcs are much more distant galaxies whose light is warped by the gravitational field of the cluster.
2022-09-14: Could the Higgs Boson Lead Us to Dark Matter?
- 07:19: We know that the Higgs field is what gives most of the standard model particles their masses.
2022-08-24: What Makes The Strong Force Strong?
- 06:03: Electrically charged particles interact with each other via the electromagnetic field.
- 06:07: We can think of each charged particle as generating a constant buzz of virtual photons around it, forming what we think of as its EM field.
- 06:31: Assuming the strong force works roughly the same way, we need a field to mediate it, and that field should have its own particles.
- 06:42: A pair of quarks bound into, say, a pion, are connected by a gluon field, also describable as a constant exchange of virtual gluons.
- 06:53: But this field looks very different to the electromagnetic field around a nucleus.
- 07:02: Instead of forming a fading gradient of field strength, quark pairs are connected by a thread of gluon field called a flux tube.
- 07:12: As quarks are separated, the thread doesn’t weaken like the EM field does.
- 08:11: ... behavior of the gluon field explains why we only see quarks in groups, but we need one more puzzle ...
- 08:55: ... what electrical charges do, they attract each other until their electric fields cancel out, that's why everything around you is electrically ...
- 09:05: You would have to get really close to an atom to feel the positive electric field of the nucleus, or the negative electric field of the electrons.
- 11:32: That means photons can interact with objects without affecting their electric charge, and thus neutral objects can interact with magnetic fields.
- 17:53: ... but instead are a calculation tool to describe fluctuation quantum fields, what does that mean for Hawking ...
- 18:28: Hawking’s original derived his radiation by calculating the disturbances on the quantum fields due to the appearance of an event horizon.
- 18:36: Those fields have positive and negative frequency modes that cancel each other out to leave a vacuum.
- 19:44: Geoffry Gifari asks whether quintessence, being a scalar field, could allow it to interact with Higgs field and modify each other's expectation value.
- 19:54: The answer is absolutely, though they don’t need to be scalar fields to interact.
- 19:59: If you dig through the literature, you’ll find various studies about coupling the Higgs field to a quintessence-like field for various reasons.
- 20:07: For example, apparently you can do this eliminate the so-called Higgs instability, which blows up the Higgs field at high energies.
- 20:19: There are LOTS of ways these fields could behave.
- 20:27: Speaking of which, Marik Zilberman asked whether a particle of the quintessence field could account for Dark Matter?
- 20:38: ... would need to be coupled strongly with the Higgs field to give the particle enough mass, but it would still need to couple ...
2022-08-17: What If Dark Energy is a New Quantum Field?
- 05:50: ... energy density of dark energy. You can reduce that number if the quantum fields sort of cancel each other out. A perfectly symmetric canceling could get ...
- 07:31: ... the big bang. That expansion must have been due to one or more quantum fields being in a highly energetic state, rather than all quantum fields ...
- 08:36: ... filled the celestial spheres beyond the earth. It’s an apt because it's field fills all of space and also it can be thought of as another force on top ...
- 09:13: ... quintessence field would have to be a scalar field, like the Higgs field. So, it would take ...
- 10:55: ... quintessence actually gives us another explanation. The quintessence field could be coupled to the quantum fields responsible for radiation and ...
- 11:51: ... bit ambiguous, and all of these could result from a new scalar quantum field. ...
- 13:04: ... only way to get omega less than -1 is for the kinetic energy of the field to be negative. These sorts of negative energy scenarios break the rules ...
- 13:27: ... flexible theoretical mechanism. There’s even a scenario in which the field evolves in such a way to halt the expansion of the universe and cause it ...
- 14:41: ... with a quintessentially consistent dark energy, or scalar quantum fields shift in a quintessence-saturated space ...
2022-08-03: What Happens Inside a Proton?
- 04:17: ... pair of electrons interacting with the electromagnetic field - emitting and absorbing a virtual photon. And there’s a set ...
- 05:14: ... coupling strength between the electron and electromagnetic field. The smallness of the fine structure constant means the ...
- 05:31: ... force, which is mediated via virtual gluon of the gluon field rather than virtual photons of the electromagnetic ...
- 07:07: ... previously. Real particles are sustained oscillations in a quantum field that have real energy and consistent properties. Virtual particles ...
- 07:53: ... coupling between quark and gluon fields is so intense that the disturbances of those fields are way too ...
- 08:30: ... there’s an astronomical number of configurations that the field could pass through in the intervening time. No ...
- 08:58: ... to do here. We want the probability for some wiggly quantum field wiggles between two states. Let’s go back to electromagnetism just ...
- 09:50: ... through physical space we add up trajectories through the space of field configurations. And that is much harder to do, for three ...
- 10:18: ... even then, there’s still an astronomical number of ways that the field can move from the starting to final configuration. And ...
- 10:43: ... we randomly choose a selection of field configurations of a pixelated space that get us from the ...
- 11:28: ... quantum field is a 3-D pixelated lattice that evolves through time. As with the ...
- 12:15: ... our couple quark-gluon field looks like this: a lattice of points with connections. ...
- 13:36: ... trick of transforming quantum fields into a lattice was first discovered by Ken Wilson all the ...
- 14:08: ... even works gives us deep insights into the nature of the quantum fields. For one thing, because it doesn’t use virtual particles at all, but ...
2022-07-27: How Many States Of Matter Are There?
- 03:47: ... general the field of physics that studies the relationships between the statistical ...
2022-06-30: Could We Decode Alien Physics?
- 07:38: ... rule. Say you have an electron moving through a magnetic field. That field is going to apply a force in some direction to that ...
- 16:39: ... sails that decelerate in the light and wind and magnetic field of the destination star, or Bussard ramjets - vast scoops that ...
2022-06-22: Is Interstellar Travel Impossible?
- 10:38: There are more advanced options for the latter - for example, deflection of grains by magnetic fields or a shielding mass moving in front of the ship.
- 12:29: These things are accelerated in the monstrous magnetic fields of black holes and supernovae and of the galaxy itself.
2022-06-15: Can Wormholes Solve The Black Hole Information Paradox?
- 07:24: ... pulls ideas from string theory, holography, quantum field theory, and quantum computing to name a few fields. ...
2022-06-01: What If Physics IS NOT Describing Reality?
- 02:44: ... In quantum mechanics, we have things like particles and fields which can only take on discrete or quantized values. These ...
- 04:56: ... the magnetic moment of the particles interact with a magnetic field gradient to deflect the particles either up or down, depending on ...
2022-05-25: The Evolution of the Modern Milky Way Galaxy
- 17:21: ... asks “If space doesn't expand inside a gravitational field, then what happens at the boundary between this and ...
- 18:41: ... say that space is flowing inwards in a gravitational field. You may have heard me say that space flows across the event ...
2022-05-18: What If the Galactic Habitable Zone LIMITS Intelligent Life?
- 10:04: ... continued to pour into the Galaxy’s growing gravitational field. It was swept up into a widening whirlpool where it continued ...
2022-05-04: Space DOES NOT Expand Everywhere
- 06:04: ... it's attached to. But that’s not what’s happening. The gravitational field isn’t somethin,g that lies on top of the fabric of spacetime. The ...
- 06:51: ... build up tension in a way that can pull against these embedded static fields. It’s as though the balloon adds more rubber as it inflates, always ...
- 07:58: ... we see distant gridlines diverging, but nearby lines in a gravitational field remain ...
- 13:50: ... created in a particle collider it travels through the powerful magnetic fields of the detector. The amount by which its path is deflected by that field ...
2022-04-27: How the Higgs Mechanism Give Things Mass
- 01:35: ... a bit of a refresher on the episodes that led to this - fields and forces and symmetries and all that. Similar to how ...
- 01:48: ... wiggle, twist, oscillate in different ways. A quantum field just represents one of these modes. And these wiggles are ...
- 02:04: ... special type of field is the gauge field. These arise from the fact that ...
- 02:31: ... mechanics, such a “redundant degree of freedom” leads to a gauge field. We’ve seen an example of this. The exact phase of the ...
- 02:50: ... this requirement, we find that we have to add a new quantum field to the Schrodinger equation that lets the universe ...
- 03:36: ... for … reasons. That requirement gave us a new gauge field that has 3 force carriers that look awfully like the weak force ...
- 04:37: ... combined symmetry group U(1)xSU(2). The resulting gauge field still has bosons that look a bit like the photon and the three ...
- 07:01: ... similar way. The equivalent of the simple valley exists. A quantum field can oscillate around some “zero-point” value like a ball rolling ...
- 07:33: ... of this field are just oscillations of the field strength across the lowest ...
- 07:52: ... the kinetic energy and the potential energy in the field. Our plot was of the potential energy ...
- 08:09: ... particular Lagrangian describes a simple quantum field made of massive particles which interact with each other. ...
- 09:00: ... that means this isn’t a gauge field. The gauge field is a new thing that comes from the degrees of ...
- 09:16: If we complicate things by adding a second field compone nt - phi 1 and phi 2 - we get a parabolic bowl.
- 09:25: ... the current state of the field is at the bottom of the dip then it has a single ...
- 09:34: ... one point in space to the next. That means adding a new gauge field in the Lagrangian that allows the angle of this rotational ...
- 09:59: ... in that field would be a gauge boson. You can think about those oscillations ...
- 10:15: ... the other hand, the particle of the original field needs a rest mass energy to be able to oscillate up ...
- 10:23: ... just like the two valleys we saw earlier, but now with this extra field component to give us this shape. It’s called a mexican hat ...
- 11:02: ... field strength would find itself on top of this little hill, but then ...
- 11:28: ... is just like how the field of magnets can be in a state of broken symmetry even ...
- 11:37: ... least interesting thing about this process. Once the field has reached the base of this new minimum we have a new stable ...
- 11:56: ... energy state - the vacuum state - isn’t where the field strength is zero. This is called a non-zero vacuum ...
- 12:26: ... will just have chosen one state randomly. But the field can also oscillate along the base of the valley in what we’ll call ...
- 12:59: ... to demand local U(1) invariance and come up with a gauge field that shakes out shifts in our arbitrary choice of the zero point ...
- 13:44: ... now this gauge field finds itself in a much more complex Lagrangian with this Mexican ...
- 13:58: ... the theta angle, can be absorbed into this U(1) gauge field. Both are oscillations around the valley. In the Lagrangian ...
- 14:54: ... this happens because of the non-zero vacuum state of the Higgs field. That little bit of Higgsiness everywhere refuses to ...
- 15:06: ... the independent mediator of a part of the old electroweak field - what we now experience as electromagnetism, while the W and ...
- 16:02: ... that’s where we are today. This is the Higgs mechanism. The Higgs field also gives mass to the matter particles - the fermions ...
2022-04-20: Does the Universe Create Itself?
- 00:59: ... that the universe exists not so much in physical particles and quantum fields, nor solely in the mind of the observer, but rather in the interaction of ...
- 04:57: ... “it from bit.” In his words, “Every it — every particle, every field of force, even the spacetime continuum itself — derives its function, ...
- 16:10: ... will lead to a disconnection in the vibrational modes of the quantum fields in a way that looks like thermal radiation. That radiation has a ...
2022-03-23: Where Is The Center of The Universe?
- 03:11: It can also give us the gravitational field of the entire universe, which tells us the shape of all of spacetime.
2022-03-16: What If Charge is NOT Fundamental?
- 12:50: So we now know that electric charge is a sort of shadow of the ancient fields from the birth of the universe.
- 12:58: Very soon we’ll follow this thread deeper to fully understand why these fields separated, and how, in this process, the Higgs field was also created.
2022-03-08: Is the Proxima System Our Best Hope For Another Earth?
- 11:43: ... sufficiently thick atmosphere and strong planetary magnetic field could in principle protect any surface dwellers, who would then get to ...
- 16:52: ... the objective collapse episode we talked about some field “hitting” the wavefunction to cause it to collapse, and Kadag asks what ...
- 17:04: It has to be a field that has a non-linear influence on the wavefunction.
- 17:27: ... yes, one field that might be able to do this is gravity, in which case the wavefunction ...
- 17:58: ... quantum mechanics and quantum field theory assume a well-defined underlying framework, upon which all the ...
- 18:33: When those cosmic strings radiate gravitational waves, how is the Higgs field supposed to smooth itself out?
- 18:40: Two ways: if the loop shrinks itself down to zero size then the Higgs field phase angles can match up.
- 19:01: Rather than being a simple knot in the field, imagine something more like a shoelace knot - it can potentially untangle itself.
- 19:27: ... - just the the phase of the wavefunction - it’s a symmetry of the Higgs field and doesn’t affect the behavior of the ...
2022-02-23: Are Cosmic Strings Cracks in the Universe?
- 00:00: ... clear ice cube for your drinks, it’s important to consider quantum fields. First, boil to release dissolved gasses, then make sure the ...
- 00:58: ... exist, we need to understand phase transitions in quantum fields - we need to see how a whole universe can freeze like a badly-made ...
- 04:51: ... quite suddenly the Higgs field everywhere in the universe found itself sitting at a higher ...
- 05:59: ... bubbles met. Our ice cube forms sheets, but our Higgs field formed strings. Remember that the vacuum decayed in a ...
- 07:33: ... for another time. OK, so we’ve managed to freeze the quantum fields amidst the first bawlings of the baby universe and woven some ...
- 10:09: ... they slowly decay away. Eventually they vanish as the Higgs field smooths itself out across the filament. The smaller ...
- 12:19: ... about the origins of the universe, or the nature of quantum fields, or the validity of string theory. Many murky mysteries may ...
2022-02-16: Is The Wave Function The Building Block of Reality?
- 08:02: ... imagined that the localizing mechanism was a randomly jiggling field, like the frenetic Brownian motion of pollen grains floating on water. ...
- 08:32: ... the mechanism actually was. They just thought there was some mysterious field that interacted with all matter — almost like it was a fifth fundamental ...
- 11:09: ... be randomly tossed about and jostled by gravity or some other collapsing field. If the quantum object happens to be electrically charged, then the ...
- 14:52: ... are wiggles in that very fabric. So they get deflected by gravitational fields just like anything else. If that gravitational field is made by a black ...
2022-02-10: The Nature of Space and Time AMA
- 00:03: ... on how fast you're moving on whether you're in a gravitational field um but this depiction of space and time has both of these dimensions ...
2022-01-27: How Does Gravity Escape A Black Hole?
- 02:22: But this “speed of gravity” also tells us how quickly a regular gravitational field changes.
- 03:34: In GR, the gravitational field - the curvature of spacetime - has an independent existence to the mass that causes it.
- 03:42: ... itself, it’s interacting only with the local part of the gravitational field. ...
- 05:27: One patch of space doesn’t need to see the ultimate source of the field - it only needs to see the next patch along.
- 05:47: It breaks down at very small distances and in very high gravitational fields.
- 06:08: Now in quantum mechanics - or more specifically quantum field theory - forces are mediated by particles, not by the geometry of spacetime.
- 06:16: ... virtual photons - ephemeral excitations in the electromagnetic field. ...
- 07:21: ... sort of emerge from the electromagnetic field in the broader region occupied by both of the electrons, and their ...
- 07:44: The gravitational field around the black hole is already abuzz with virtual gravitons.
- 07:55: That’s easy - these are virtual particles, and in quantum field theory, virtual particles are not restricted by the speed of light.
- 08:25: But if we’re describing the gravitational field as being built up by virtual gravitons then the event horizon is no barrier at all.
- 10:06: ... a causal connection to the mass that generated that gravitational field. ...
- 10:19: ... their Penrose diagrams, just think about the source of the gravitational field as always being in your past lightcone - and that has to be outside the ...
- 10:37: If a black hole swallows electric charge, the electromagnetic field around the black hole grows.
- 11:27: ... poorly defined in general relativity in part because the gravitational field itself has energy, and so is a source of ...
2022-01-19: How To Build The Universe in a Computer
- 02:56: ... of a pair of massive bodies moving in each other’s gravitational fields. ...
- 03:59: ... is short enough that we can assume that the global gravitational field is constant - it only changes in the next step, after all the particles ...
- 09:34: ... don’t get me started about the complexity of including magnetic fields, or of Einstein’s general relativity when the gravitational field becomes ...
2022-01-12: How To Simulate The Universe With DFT
- 01:48: ... energies - that’s the V. V could result from the electromagnetic field inside the hydrogen atom, or the EM fields defining the walls of a box, ...
2021-12-20: What Happens If A Black Hole Hits Earth?
- 14:26: ... chasing our tail adding all this complexity. "Let's just add a few more fields to GR so that our theory fits the data.” Well to that I’ll let Einstein ...
- 16:33: ... idea of general relativity that says that freefall in a gravitational field is fundamentally the same as inertial motion in free space. That means ...
- 17:30: ... which we covered previously. It, says that vibrations in a quantum field on the surface of a 4-D hyperbolic space are equivalent to objects ...
2021-12-10: 2021 End of Year AMA!
- 00:02: ... me think maybe there's something wrong with the earth's gravitational field time seems to be passing more quickly actually it's been quite a long ...
2021-11-17: Are Black Holes Actually Fuzzballs?
- 04:49: ... relativity but then analyze its effect on the surrounding quantum fields, which only worked if the gravity at the horizon was relatively weak, in ...
- 09:25: ... as the neutron star’s gravitational field is so intense that atomic nuclei are crushed into a soup of neutrons, a ...
- 10:50: Light trying to escape would still be massively redshifted - sapped of energy by the gravitational field - rendering the object effectively black.
2021-11-10: What If Our Understanding of Gravity Is Wrong?
- 02:02: ... to Isaac Newton’s Law of Universal Gravitation, the gravitational field drops off with the square of distance from the mass producing that ...
- 02:32: ... evenly distributed through galaxies, strengthening the gravitational field in the outskirts to explain the high rotation ...
- 02:52: ... found that Newtonian gravity breaks down when the gravitational field gets too strong - there you need his general theory of relativity, ...
- 03:08: But Einsteinian gravity looks exactly like Newtonian gravity when gravitational fields get weak.
- 03:18: What if Newtonian gravity breaks down both for very strong AND very weak fields?
- 06:10: ... general relativity does not reproduce MOND in what we call the “weak field limit.” Instead it does what it was designed to do - it reproduces good ...
- 08:29: Bekenstein and Milgrom achieved this by adding a second field to gravity.
- 08:35: ... Einstein’s description, the gravitational field is what we call a tensor field - a multi-component object that ...
- 08:44: These guys added a new scalar field - a field that’s just a single numerical value everywhere in space.
- 09:15: AQuaL also had the unfortunate prediction of faster-than-light waves in this added scalar field, which broke causality.
- 09:29: If adding one field doesn’t work, why not add another?
- 09:32: ... Scalar gravity - based on the fact that it describes gravity with three fields - a tensor, a vector, and a ...
- 09:45: The introduction of the new field fixed the problem with gravitational lensing and also tamed the awkward causality-breaking nature of AQuaL.
- 11:38: Their big change was that they allowed the scalar field to change its behavior over time.
- 11:45: ... to tweak their equations so that in the early universe, that field behaved a bit like a type of matter, which Złosnik calls “dark ...
- 17:33: In fact, in general relativity objects in gravitational fields tend to maximize, not minimize their proper time.
2021-11-02: Is ACTION The Most Fundamental Property in Physics?
- 00:02: ... - like when it’s refracted by glass or traveling through a gravitational field. It took a millennium and a half following Heron for Pierre de Fermat to ...
- 06:47: ... depending on things like relative speed and position in a gravitational field. Proper time is the time that an object will perceive in its own ...
- 13:16: Well it turns out that this equation is just the Lagrangian for a spin-½ quantum field.
- 13:23: ... there’s a Lagrangian for each quantum field which describes how that field and its particles tend to evolve. ...
2021-10-20: Will Constructor Theory REWRITE Physics?
- 09:17: From the definitions of what an information medium is, Marletto argues that this chain of quantum elements is equivalent to a quantum field.
- 09:27: And she argues that only a "superinformation medium" - aka a quantum field - could mediate the entanglement of two spatially separated qubits.
2021-10-13: New Results in Quantum Tunneling vs. The Speed of Light
- 10:48: ... is called Larmor precession, in which a particle’s dipole magnetic field, which is defined by its spin axis, precesses like a top in an external ...
- 11:02: In this experiment, they fired ultracold rubidium atoms at a laser field that was spread out over a small area.
- 11:10: That field was strong enough to deflect the atoms completely, and so provided an insurmountable barrier.
- 11:20: ... those ones, their spins were altered by the magnetic field of the laser, and the longer they spent inside the barrier, the more ...
- 14:19: ... about the hedgehogs configurations - the radiating knots in the Higgs field that might lead to magnetic ...
- 14:43: ... answer is that at very high energies, the direction of the Higgs field becomes free to vary wildly and adjacent points in the field are less ...
- 14:53: Only when the field cools down to adjacent points become more tied to each other.
- 14:57: Any discontinuities that formed at high temperature can then be frozen into the field.
- 15:03: And Nate Underwood asks if the Higgs field can form so that there are no monopoles - no discontinuities.
- 15:48: ... behave like a monopole in that the black hole would radiate magnetic field ...
- 15:57: Same as if the black hole held electric charge; it would produce an electric field.
- 16:08: As it is, the magnetic fields we observe around black holes seem more consistent with regular dipole fields, with both north and south poles.
2021-10-05: Why Magnetic Monopoles SHOULD Exist
- 00:30: The electric field of the bar now looks like this - that’s a dipole field.
- 00:35: ... charges - one negative and one positive, both of which have electric fields that radiate straight ...
- 00:50: You get a dipole magnetic field that’s very similar to the dipole electric field.
- 01:04: The ends of the split magnet still have north and south poles, and still generate a dipole field.
- 01:43: In a ferromagnet, the field is the sum of the countless tiny aligned dipole fields of electrons in the magnet’s atoms.
- 01:51: ... other popular way to make a dipole magnetic field is the electromagnet - where were push electrons around in a circle In ...
- 02:06: And according to classical electrodynamics, moving electric charge is the source of the magnetic field.
- 02:32: It states that the divergence of a magnetic field is zero.
- 02:37: The divergence is just this mathy term for the amount that a field points inward toward a sink or outward toward a source.
- 02:51: Magnetic field lines can form loops or head out toward infinity, but they never end.
- 03:00: ... the other hand, Gauss’ law for electric fields tells us that the divergence of the electric field is not zero - it’s ...
- 03:09: That charge density is where the electric field lines can end - it forms their source or their sink.
- 03:26: E is the electric field and B is the magnetic field.
- 04:26: ... understanding of electromagnetism by explaining it in terms of quantum fields rather than charges and ...
- 04:54: ... - but in that version of electromagnetism, the electric and magnetic fields are VERY different from each other, and not at all interchangeable as ...
- 05:09: ... particular, the magnetic field emerging from the quantum theory must have zero divergence - its field ...
- 06:00: ... you start with a dipole magnetic field, you can approximate a monopole by moving the ends far enough apart and ...
- 06:14: ... a solenoid - just a coil carrying an electric current - you get a dipole field whose connecting field lines are constrained within the ...
- 06:49: So magnetic fields affect charged particles.
- 07:09: ... presence of the string, with its magnetic fields, should introduce different phase shifts depending on which side of the ...
- 09:00: We talked about that before - about how the breaking of the symmetry of the Higgs field separated the weak and electromagnetic forces.
- 09:25: Let me try to give you a sense of why - and we have to talk about the Higgs field to do this.
- 09:37: ... in electroweak theory, the Higgs field is a scalar field - it takes on a numerical value everywhere in the ...
- 09:55: In the simplest grand unified theory, the Higgs field has three degrees of freedom instead of two.
- 10:01: That means the field can sort of act like a vector, even though it really isn’t one.
- 10:13: ... physics shouldn’t care about the relative internal values of the Higgs field - what matters is the absolute length of that internal vector - not the ...
- 10:24: There should be no noticeable effect even if the direction of the Higgs field changes smoothly across space.
- 10:34: ... the direction of the Higgs field varies smoothly from one point to the next, it can still have these ...
- 10:55: And it turns out these knots in the Higgs field in GUT theories behave as massive particles with magnetic charge - magnetic monopoles.
- 13:24: ... using cosmic ray observatories - or contributing to the Earth’s magnetic field - and in a number of other ...
- 15:39: ... that spin can be described as a circular charge current in the Dirac field. ...
2021-09-15: Neutron Stars: The Most Extreme Objects in the Universe
- 01:02: ... the radiation and pressure, and an anti-gravitational field to resist the ridiculous gravitational ...
- 01:42: ... we encounter is its magnetosphere. This is the strongest magnetic field in the universe. Even the weakest neutron star fields are a ...
- 02:00: ... are created out of the extreme energy photons in the magnetic field. That field then becomes a particle accelerator, with electron ...
- 11:29: ... essential part of maintaining the neutron star’s enormous magnetic field. ...
2021-09-07: First Detection of Light from Behind a Black Hole
- 01:21: And the more recent version of this in polarized light shows the grain of the magnetic field right near the black hole’s edge.
- 04:37: ... gas is accelerated by a combination of the incredible gravitational field of the black hole and the continuous blaze of high energy radiation from ...
- 10:49: A portion of that light was then grabbed by the black hole’s gravitational field and slung right back around towards us, and magnified in the process.
- 13:05: ... warp fields are supposed to blast an intense beam of radiation ahead of them when ...
- 14:47: Some scalar field that may or may not have been the Higgs field, is thought to have dropped from a much higher value into a stable minimum.
- 14:54: The difference is that in the pre-inflation universe, space was expanding exponentially quickly due to the high value of that field.
- 15:54: ... that the bigger the energy difference, the less probability of the field tunneling to the true minimum, so maybe those cancel ...
2021-08-18: How Vacuum Decay Would Destroy The Universe
- 00:21: ... universe is largely defined by the properties of the quantum fields that pervade all space. The quantum fields give rise to the ...
- 01:15: ... expands at the speed of light, rewriting the nature of the quantum fields as it ...
- 01:24: To understand whether and when this might happen, we first need to understand the quantum fields that it threatens.
- 01:31: ... or deform or more complex ways. We can think of each quantum field as a set of these modes of oscillation. And each quantum ...
- 02:18: ... like the deformed ring, a quantum field wants to return to its equilibrium position. That position ...
- 02:52: ... most quantum fields, the minimum energy is where the field value is zero. ...
- 03:11: ... there’s one quantum field that breaks these rules. That’s the Higgs field. The minimum ...
- 04:00: ... would look like multiple dips in our graph of energy versus field strength. A quantum field with multiple minima like ...
- 04:42: ... pretty much everything, but certainly in the value of a quantum field. This results in fluctuations in the field strength ...
- 05:03: ... what does this mean for the Higgs field? Well some theorists do believe that the Higgs field has at least ...
- 05:43: ... catastrophic consequences of this. Firstly, if the Higgs field is in the true minimum then no big deal. Even if the ...
- 06:08: ... a universe filled with the Higgs field in a false vacuum. At a single point in space, a quantum ...
- 07:01: ... the bubble is unstoppable, and will drag the Higgs field through the entire universe down into the true vacuum. This ...
- 08:08: ... gets fried. The energy released in the decay of the Higgs field fills the expanding bubble with a hot soup of ...
- 08:30: ... that’s not the worst of it. As I mentioned, the Higgs field gives elementary particles their masses. Those masses depend ...
- 09:15: ... about whether that vacuum might decay. Assuming the Higgs field really does have multiple minima, the question becomes ...
- 09:38: ... can determine the shape of the Higgs field with precise measurements of the particles that gain ...
- 10:54: ... If enough energy can be pumped into a patch of space, the Higgs field can hop between minima without tunneling. This would ...
2021-08-10: How to Communicate Across the Quantum Multiverse
- 06:09: ... principle only holds to a point. Real pond surfaces or air density fields don’t behave like simple harmonic oscillators if you try to change them ...
- 11:11: ... that subjects both branches of the electron wavefunction to a non-linear field. That field sort of spreads the local information from each branch - each ...
- 16:27: ... Persona asks what happens to the star’s magnetic fields after it goes supernova. And then guesses the correct answer - it ...
- 16:58: ... see that field in many ways, including by watching the radio light emitted by electrons ...
2021-08-03: How An Extreme New Star Could Change All Cosmology
- 03:19: ... over the place in a way that suggests the presence of gigantic magnetic fields. Fields around a billion times stronger than the earth or sun’s magnetic ...
- 08:48: ... is that it’s rotating extremely quickly and has a crazy strong magnetic field. We just don’t see these extreme properties in the white dwarfs produced ...
- 09:51: ... of the parent stars. This process also explains the intense magnetic fields. Magnetic fields in stars and planets are generated by dynamos - ...
- 14:52: ... Charlie, and extend their white dwarf blessings: may your magnetic fields stay untangled, your electrons be ever degenerate, and may your mass ...
- 15:55: ... asks whether magnetic fields have any measurable effect on the orbits of stars around the galaxy. Not ...
- 16:19: So the locations that stars formed may be influenced by magnetic fields, which in turn affects their orbits. So the answer is yes, sort of.
- 16:29: ... Charlton and Brandon Munshaw ask whether magnetic field lines are really “lines” versus some sort of continuous thing. Well it's ...
- 17:08: ... number of you ask questions about the potential role of magnetic fields in the universe that all have the answer I just gave - can magnetic ...
2021-07-21: How Magnetism Shapes The Universe
- 00:07: Compass needles align with magnetic field lines, and on the precise spot of magnetic north, those field lines are vertical.
- 00:36: Imagine you can see gravitational fields.
- 00:50: But there’s really only one gravitational field in the universe - manifest as the fabric of spacetime itself.
- 01:08: The universal gravitation field is just a grid with some dips in it.
- 01:12: Personally, I’d rather be able to see magnetic fields.
- 01:43: Even if the substance is electrically neutral you’ll still get a magnetic field as long as the charges are moving in opposite directions.
- 01:51: That means magnetic fields can add up - and magnetism adds up to having enormous influence on the development of structure in our universe.
- 02:01: Understanding magnetic fields is of fundamental importance to astrophysicists.
- 02:12: Magnetic field lines form in concentric circles around moving charges.
- 02:16: ... that charge moves in a loop, that results in a dipole field - sort of a torus around the loop with the field threading the loop and ...
- 02:26: So those are magnetic field lines - but what do they do?
- 02:30: ... feel a force perpendicular to both its direction of motion and to the field lines - and the net result of that is that charged particles tend to ...
- 02:43: ... a ferromagnet, then that current will want to loop around the magnetic field. ...
- 02:56: ... the circular current produces its own dipole field, and the net result is that dipole fields always try to align themselves ...
- 03:15: Where exactly does that field line go?
- 03:17: As with the gravitational field, in a sense there’s only one universal magnetic field.
- 03:23: ... while most of the Earth’s dipole field loops back - but some of those field lines connect to this greater ...
- 03:34: So let’s hitch a ride on a field line and see how far it takes us.
- 03:44: But while we’re here, it’s worth following one of Earth’s field lines that connects directly to the surface of the Sun.
- 03:53: Here the field is generated by electrical currents flowing in the searing plasma near the Sun’s surface.
- 03:59: The Earth’s solid inner core and mantle regulate the flow in its liquid outer core, resulting in a clean dipole field.
- 04:12: That means the dipole field gets twisted up over time.
- 04:16: Magnetic field lines cross each other, and enormous magnetic energy densities pile up.
- 04:21: We can see those tangled field lines in ultraviolet light as charged particles spiral along them, up and down from the Sun’s surface.
- 04:29: ... the pressure gets too high, these field lines snap and then reconnect, and in the process spray that magnetic ...
- 04:49: This is still the Sun’s magnetic field, which connects here and there to the piddling little fields of the planets.
- 04:55: About 4x the distance to Pluto, the Sun’s magnetic field connects to the field of the galaxy itself.
- 05:46: Beyond the heliosphere, seeing magnetic fields gets trickier.
- 06:08: These specks tend to align with the local magnetic field of the Galaxy in exactly the same way as our iron filings align around a bar magnet.
- 06:29: The light gets polarized - which means the direction of its electric and magnetic fields pick up a preferred direction rather than being random.
- 06:37: By measuring this polarization we can map the direction of these tiny compass needles, and so map the magnetic field of the Milky Way.
- 07:01: KInda makes me wonder if van Gogh could see magnetic fields.
- 07:05: Actually there’s a more traditional way to map the magnetic fields of galaxies.
- 07:09: These fields drive the motion of lone electrons throughout the interstellar medium.
- 07:35: If the electric and magnetic fields of a collection of photons all tend to point in the same direction, we say the light is linearly polarized.
- 07:43: ... if those fields are not fixed but rather rotate in the same direction, we say the light ...
- 07:55: The electrons in their magnetic fields tend to slow one circular polarization direction more than the other.
- 08:12: So by measuring the Faraday rotation of distant radio sources we can also map magnetic fields.
- 08:21: We even have clear views of magnetic fields in many distant spiral galaxies.
- 08:26: We see that the field tends to be threaded along the spiral arms.
- 08:30: These are the densest regions of those galactic disks - places where magnetic fields have confined the charged particles of the interstellar plasma.
- 08:39: And that plasma in turn drags the magnetic fields in orbit around the galaxy.
- 08:44: OK, so galaxies have magnetic fields.
- 08:47: But where do those magnetic fields come from?
- 08:51: Large-scale magnetic fields can grow and reinforce themselves in very particular configurations called dynamos.
- 09:10: These amplify what starts out as a very weak and disordered field into the ordered and powerful field that surrounds the Earth.
- 09:38: Those supernovae may also give us the seeds of magnetic fields that can then be amplified by the galactic dynamo.
- 09:45: However it got there, the Milky Way has built itself a substantial magnetic field.
- 09:50: And that field helps build the Milky Way in return.
- 09:53: Magnetic fields generated by collapsing gas clouds help to slow the rotation of those clouds - expel angular momentum.
- 10:05: And magnetic fields also facilitate star formation after stars die.
- 10:27: But the galactic magnetic field constrains that flow, funneling some of it into vast galactic fountains erupting from the poles.
- 10:34: That’s right - if you follow a magnetic field line too far, you may accidentally leave the galaxy.
- 10:53: The other cool thing that galactic magnetic fields do is that they act as colossal particle accelerators.
- 11:08: Electrons and atomic nuclei can be accelerated in this magnetic field to high energies - into what we call cosmic rays.
- 11:20: But the most energetic cosmic rays are accelerated by the strongest magnetic fields.
- 11:40: Intense magnetic fields live just above the event horizon of some of thses black hole, and thread the infalling disk.
- 11:47: Those fields grab particles of matter and accelerate them to incredible energies, flinging cosmic rays out into the universe.
- 11:54: ... even taken our first picture of the such a magnetic field - in the polarized light surrounding the M81 supermassive black hole ...
- 12:05: But there’s an even more spectacular result of these magnetic fields.
- 12:23: ... jets carry magnetic fields out into the cosmos, and we see them through the radio light emitted by ...
- 12:32: OK, we’ve ridden our magnetic field lines pretty far and into some strange places.
- 12:38: To summarize what we’ve learned: magnetic fields are ubiquitous, powerful, and extremely complicated.
- 12:53: But it turns out that without cosmic-scale magnetic fields we probably wouldn’t be here today.
- 12:59: ... spending more and more time learning how to map and to model magnetic fields, to better understand the mysteries of this magnetic space ...
- 13:29: ... in his personal magnetism when they calculate the Earth’s geomagnetic field. ...
2021-07-07: Electrons DO NOT Spin
- 00:47: ... a cylinder of iron from a thread and switch on a vertical magnetic field. The cylinder immediately starts rotating with a constant speed. At first ...
- 02:25: ... energy levels tend to split when atoms are put in an external magnetic field. This Zeeman effect was explained by Lorentz himself with the ideas of ...
- 03:20: ... then came the anomalous Zeeman effect. In some cases, the magnetic field causes energy levels to split even further - for reasons that ...
- 04:40: ... in the Einstein de-Haas effect, and it also gives electrons a magnetic field. An electron’s spin is an entirely quantum mechanical property, and ...
- 05:15: ... Gerlach a year later. In it silver atoms are fired through a magnetic field with a gradient - in this example stronger towards the north pole ...
- 05:37: ... means the external magnetic field induces a force on the atoms that depends on the direction that ...
- 06:36: ... oriented horizontally. Classical dipoles that are at 90 degrees to the field would experience no force whatsoever. But if we put our detector screen ...
- 11:34: ... looking at the energy and charge currents in the so called Dirac field. ...
- 11:44: ... the quantum field surrounding the Dirac spinor aka the electron, imply ...
- 17:29: ... Cloud” - is actually named after Dr, Shannon, the founder of the field of information theory. As with many of these things, the word has been ...
2021-06-23: How Quantum Entanglement Creates Entropy
- 03:45: ... and entropy. It was Claude Shannon who founded the field of Information theory, and also invented the entropy of information ...
2021-06-16: Can Space Be Infinitely Divided?
- 06:02: ... is starting to produce an observable gravitational field. Even though photons are massless, if enclosed in a system a ...
2021-06-09: Are We Running Out of Space Above Earth?
- 12:33: We’ll have to curb our appetite for global digital communication for at least several years while we wait for the junk field to fall back to Earth.
- 12:59: ... faster, or even electromagnetic tethers which push on earth’s magnetic field to deorbit a ...
- 16:05: ... everywhere perfectly explains one of the most vexing paradoxes in the field of domestic mechanics - as in it explains what happened to your lost ...
2021-05-25: What If (Tiny) Black Holes Are Everywhere?
- 01:51: It came from thinking about how black holes interact with the quantum fields from which all elementary particles arise.
- 02:06: ... event horizon forms in a vacuum, then the vacuum states of the quantum fields have to be ...
- 05:31: So a large black hole is like our entire poker - there are many ways that the quantum fields can fluctuate around it.
2021-05-19: Breaking The Heisenberg Uncertainty Principle
- 00:25: ... recent g-2 experiment for measuring the muon’s interaction with quantum fields is good to to one part in a billion And also pretty recently we have the ...
2021-05-11: How To Know If It's Aliens
- 16:32: ... - wormholes between adjacent dimensions threaded by electromagnetic fields. Turns out particles aren’t that, but it’s how the wormhole concept was ...
2021-04-21: The NEW Warp Drive Possibilities
- 01:34: ... Star Trek in the 60s - and Star Trek inspired the very first real warp field solution to the Einstein field ...
- 01:44: That’s the Alcubierre warp field, derived by Mexican physicist and star trek aficionado Miguel Alcubierre.
- 01:54: ... then the warp field solution looked like a very rigorous, carefully calculated work of pure ...
- 03:29: It’s a sp acetime geometry that is a valid solution to the equations general theory of relativity. The Einstein Field Equation.
- 03:54: The Alcubierre warp field may be a valid solution to the Einstein field equations, but that doesn’t mean it’s physically possible.
- 04:31: ... this, we have a set of energy conditions that go alongside the Einstein field equations that are meant to restrict the allowable energy distributions ...
- 05:11: ... other minor hiccup is that Alcubierre’s original field required more energy than is contained in all the matter in the visible ...
- 05:41: ... of the bubble is causally disconnected from parts of the front warp field. ...
- 06:28: So, yeah, warp fields became much better studied, but remained implausible - and probably impossible.
- 06:51: These guys propose a general definition for warp fields not tied to a particular solution to the Einstein field equations.
- 07:22: ... of space was only a side-effect of Alcubierre’s choice of warp field, and he constructed a warp field without that ...
- 07:38: Natario, and now Bobrick and Martire, define warp fields as bubbles that slide through space - potentially at superluminal speeds.
- 07:47: But all these guys agree that superluminal bubbles are only possible if the warp field uses exotic matter.
- 08:14: But this acceleration isn’t actually derived from his warp field solution.
- 08:20: The velocity of the bubble is baked into the equation for the field geometry, but it’s not clear how you change that velocity.
- 09:11: Lentz claims to have found an actual superluminal warp field solution that does NOT require the impossible negative energy densities.
- 09:19: He does this by exploring a broader family of solutions to the Einstein field equations than previous studies.
- 09:33: We can think of the warp field as a special type of isolated wave moving through space - what we call a soliton.
- 09:45: ... example in the Alcubierre field the warp is in front and behind the spaceship, while the exotic matter ...
- 11:36: ... warp fields exist in theory, and there’s a very tentative hints that the worst ...
- 12:04: So far there’s no known way to do this, and warp fields may suffer the same strict speed limit as does matter.
- 13:16: These guys define a type-1 warp field as a surface of positive energy density enclosing a flat metric.
- 13:23: Now the authors can correct me if I’m wrong, but I think that this means literally any enclosed surface can make a warp field.
- 14:41: ... makes it pretty hard to watch tau particles precess in magnetic fields, and so far the g-factor for the tau hasn’t even been measured to 1 ...
- 17:54: ... the Quantum Zeno Effect plays a role in birds' ability to see magnetic fields, then according to the Many-Worlds interpretation are there many, many ...
2021-04-13: What If Dark Matter Is Just Black Holes?
- 01:13: As we’ve discussed many times before, black holes are regions of gravitational field so intense that not even light can escape.
2021-04-07: Why the Muon g-2 Results Are So Exciting!
- 02:05: One of the interactions that QED describes is how a charge particle will tend to rotate to align with a magnetic field.
- 03:15: ... particles with quantum spin do generate a magnetic field, same as if you send an electric charge around a looped wire, or have ...
- 03:25: The result is a dipole magnetic field with a North and a South pole.
- 03:29: Place an object with such a field inside a second magnetic field, and the object will tend to rotate to align with that field.
- 04:00: An electron also has a dipole field and a dipole moment which depends on the electron spin charge and mass.
- 04:15: So the electron responds to a magnetic field twice as strongly compared to what you'd expect for an equivalent classical rotating charge.
- 05:23: We can represent an electron interacting with a magnetic field, with the simplest possible Feynman diagram.
- 05:31: We have an electron being deflected by a single photon from that field.
- 05:48: ... electron to emit a virtual photon just prior to absorbing the magnetic field photon, and then reabsorbing that virtual ...
- 07:29: They have a different g-factor because there are slowly different ways that the muon can interact with the quantum fields.
- 07:48: There can be very subtle interactions that involve the other forces, weak, strong, and even the Higgs field.
- 09:49: The muons interact with the magnetic field and their own magnetic dipole axis, rotate like a top just before it falls.
2021-03-23: Zeno's Paradox & The Quantum Zeno Effect
- 06:00: A constant radio-frequency field is tuned to cause electrons to oscillate smoothly between two energy levels - call them 1 and 2.
- 08:02: ... photochemical reactions that give birds their ability to see magnetic fields - something we’ve talked about ...
2021-03-16: The NEW Crisis in Cosmology
- 17:08: ... poor guys have to fight in so many different gravitational fields - star destroyers, the death star, forest moons, ice planets ...
2021-03-09: How Does Gravity Affect Light?
- 00:38: ... Michell proposed that a particle of light gripped by the gravitational field of a sufficiently massive star would slow down, stop, and fall back - ...
- 02:26: Or of the sense of weightlessness in freefall in a gravitational field versus the weightlessness felt in the absence of gravity.
- 03:29: ... we must experience all the same physics if at rest in a gravitational field - say, in a fake rocket ship in a Hollywood ...
- 03:42: Light emerging from a gravitational field is stretched out - it experiences gravitational redshift.
- 03:50: And we get exactly the same prediction if we use the fact that time runs slow in gravitational fields.
- 04:18: But from a great distance away, those clocks run slow, and so the frequency of light emerging from within a gravitational field is lower.
- 05:48: And the equivalence principle tells us we must see the same bending of the light ray in our stationary rocketship set in our gravitational field.
- 07:31: Huygens’ wave theory of light advanced the field of optics enormously.
- 09:09: But in a sense, light gets refracted by gravitational fields - or at least you can model it that way.
- 09:27: And also that the speed of light changes in gravitational fields, which sounds counter to everything I’ve told you.
- 10:19: ... effects: your clock is ticking faster than clocks in the gravitational field, and space within the gravitational field is ...
- 10:41: Of course for someone actually inside the gravitational field, the photon is still traveling at the speed of light as it whizzes past them.
- 10:54: At each location perpendicular to a gravitational field, the wavefront of light can be thought of as a vertical column of new wavelets.
- 11:43: ... due to their light rays being “refracted” in the Sun’s gravitational field. ...
- 12:32: Light is a wave and a particle; time slows or space flows in gravitational fields.
2021-02-24: Does Time Cause Gravity?
- 00:25: Clocks run slow in gravitational fields.
- 01:56: Absent a gravitational field or any forces, if the teapot starts motionless it stays that way.
- 04:26: ... It’s the same with the 4-velocity of an object in a gravitational field. ...
- 04:56: And it’s always rotated in the direction of decreasing flow - which in a gravitational field is downwards.
- 05:03: ... this is the motion of any object in a gravitational field - it gradually picks up velocity in the down direction - it accelerates ...
- 07:39: If photons are already fully rotated into the spatial direction, how is it that they’re also affected by gravitational fields?
- 07:48: But light DOES bend in a gravitational field - astronomers see it happening all the time in the effect we call gravitational lensing.
- 09:20: ... during the inflationary epoch - fluctuations in the so-called inflaton field, or in the final decay of those inflatons at the end of ...
2021-02-17: Gravitational Wave Background Discovered?
- 00:00: ... to channel jets of high energy particles due to their intense magnetic fields they also rotate rapidly with the rotational axis offset from the ...
2021-02-10: How Does Gravity Warp the Flow of Time?
- 00:25: ... an observer falling freely from the roof of a house, the gravitational field does not exist.” We now know this as the equivalence principle - it ...
- 01:00: ... weight you would feel accelerating at 1-g distant from any gravitational field - at least as far as the laws of physics are ...
- 02:30: There’s a deep connection between gravity and time - gravitational fields seem to slow the pace of time in what we call gravitational time dilation.
- 03:07: ... by me totally convincing you that time must run slow in a gravitational field - an effect we call gravitational time ...
- 05:52: It tells us that whatever we conclude about the passage of time in an accelerating frame must also be true in a gravitational field.
- 09:00: ... someone standing in a gravitational field must experience the same sense of weight AND the same time dilation that ...
- 09:16: ... of acceleration and gravity, then time must run slow in gravitational fields. ...
- 10:17: ... of caution: be aware that circular orbital motion in a gravitational field is very different from our rotating space station- then both ...
- 10:58: What really is it about the gravitational field that’s causing time to tick slow?
- 11:14: So that photon clocks and matter do evolve more slowly in gravitational fields.
- 11:19: ... is it that if you’re inside a gravitational field, your sense of “now” is continually sweeping forward compared to regions ...
2021-01-26: Is Dark Matter Made of Particles?
- 02:27: A more technical way to think about this stuff is in terms of quantum fields - where each particle and force is a vibration in its own field.
- 02:34: ... fields fill the universe, overlapping each other - and if a particle field is ...
- 02:51: But gravity is a little different to the other forces - it’s not part of the Standard Model, and we don’t even know if it has a quantum field.
- 12:03: ... by dark forces, all of them oscillations in their own dark quantum fields - perhaps with their own complexity and ...
2021-01-19: Can We Break the Universe?
- 15:23: ... changed depending on the direction and strength of a very weak magnetic field. ...
2021-01-12: What Happens During a Quantum Jump?
- 10:11: And that ability to predict also allowed them to reverse the quantum jumps midflight by adjusting the microwave field during the process.
2020-12-22: Navigating with Quantum Entanglement
- 02:22: ... have a “magnetoreception” that they navigate by the Earth’s magnetic field came from the Russian zoologist Alexander von Middendorf back in ...
- 02:32: ... biologists Wolfgang Wiltschko and Friedrich Merkel applied magnetic fields to enclosures with European robins, preventing them from navigating ...
- 02:48: How exactly birds detect magnetic fields remains an open question.
- 03:03: ... the idea that proposes birds can in a sense see the Earth’s magnetic field due to quantum weirdness happening inside their ...
- 03:19: Before we get into all the cool quantum stuff, a quick review on Earth’s magnetic field is in order.
- 03:25: For a more thorough explanation, we have an episode on how that field sometimes flips direction - which I guess drives birds crazy.
- 03:31: This “geomagnetic” field is generated by the convective motion in Earth’s outer core - which is a churning liquid mass of white-hot nickel and iron.
- 03:41: The result is a dipole field, similar to that of a bar magnet: two poles connected by force lines forming a sort of cage around the planet.
- 03:55: At any point on the surface of the earth, our geomagnetic field can be described with just a few properties.
- 04:27: And finally there’s an intensity of the field, represented by how close together the field lines are.
- 04:40: As far as we know, birds can sense the orientation of the field lines, but NOT their polarity arrows.
- 04:52: In principle it’s easy to come up with ways to sense a magnetic field.
- 04:56: Magnetic fields exert a force on a moving or rotating charged particle.
- 05:00: An electron, for example, can be thought of as a spinning charge, and magnetic fields can cause that spin to flip direction.
- 05:08: ... the one found in a compass needle aure ferromagnets, and their magnetic fields come from countless electrons with aligned ...
- 05:17: External magnetic fields tug on those electrons resulting in a force that can swivel the compass needle.
- 05:23: ... you need a lot of electrons to register Earth’s extremely weak field - far more than you could fit into the microscopic structures within a ...
- 07:10: ... to stay fixed until disturbed by its environment. And Earth's magnetic field isn't strong enough to influence spin in that ...
- 07:27: They do that evenly in the absence of a magnetic field - 75% of the time in the triplet state and 25% in the singlet.
- 07:35: But even a weak magnetic field like the Earth's can affect the amount of time the radical pair spends in these states.
- 07:41: ... that field has the correct orientation, the system will spend more time in the ...
- 07:53: ... entanglement need to last in order to be influenced by Earth's magnetic field, and how does the simple slipping of electron spins go on to give the ...
- 08:43: ... changes the orientation of its head relative to the Earth’s magnetic field. ...
- 08:59: That could lead to a true visual sense of magnetic field orientation.
- 09:15: ... shown that it’s possible to affect cryptochromes with a weak magnetic field and get that characteristic change of rate of chemical ...
- 10:12: ... reactions remember the quantum state, and so remember the magnetic field. ...
- 10:33: The team’s calculations showed that only a full quantum description of the process could produce the required sensitivity to magnetic fields.
- 10:40: ... the valence electrons were just interacting due to their magnetic fields - so-called spin-spin interactions - rather than true entangled states - ...
- 14:02: For more detail we would indeed need a whole episode Quantum fields asks what about neutron stars.
2020-12-15: The Supernova At The End of Time
- 04:32: ... to stop them from collapsing under their own intense gravitational field. ...
2020-12-08: Why Do You Remember The Past But Not The Future?
- 01:59: ... the neuroscience of memory is an incredibly deep and sophisticated field, and in the style of any good physicist, we’re going to ignore all of the ...
- 12:58: ... separately, but rather in the degrees of freedom of the gravitational field. ...
2020-11-18: The Arrow of Time and How to Reverse It
- 10:34: ... I think the answer has to be yes, at least to some degree. The Higgs field sits at a non-zero vacuum energy so could potentially decay to zero, or ...
2020-11-04: Electroweak Theory and the Origin of the Fundamental Forces
- 00:47: And this dive into electroweak unification will lead us inevitably to the Higgs field and an understanding of how particles gain mass.
- 01:36: While the brand new field of quantum mechanics could describe the behaviour of electrons, nuclear processes remained mysterious.
- 02:56: QED is what we call a gauge theory - its force-carrying fields and particles arise from the symmetries of the quantum equations of motion.
- 05:32: That stuff turns out to describe the electromagnetic field.
- 05:36: When we quantize that field - when we let it oscillate with discrete packets of energy - we get the photon.
- 05:50: That resulted in a new quantum field and a corresponding particle.
- 07:22: It had 1 degree of freedom - corresponding to a gauge field with a single mode - the electromagnetic field and its photon.
- 07:46: If we require our equations of motion to respect SU(2) we have to introduce a new field with 3 degrees of freedom.
- 07:56: Quantizing this field gives 3 bosons which are *almost* exactly what we need to make a gauge theory of the weak field work.
- 08:08: The fields and corresponding particles produced by the pure symmetries we described are fundamentally massless.
- 08:16: The bosons of the version of SU(2) that I just described are simple light-speed oscillations in their fields, just like photons.
- 08:30: Maybe, but the whole gauge field thing seemed so promising, so it's worth asking: how can we give mass to something that seems fundamentally massless?
- 08:40: The perfect masslessness of these gauge fields and bosons is a direct consequence of the perfect symmetries from which they come.
- 08:50: ... mass to a photon means adding an extra term to the electromagnetic field stuff in the Schrodinger equation so that it would no longer be ...
- 09:10: But wouldn't that mean we're throwing away the core idea that gave us our weak field?
- 10:43: So what if something similar is happening with the field that gives us the weak force?
- 10:48: ... of motion respect the symmetries that give us the necessary gauge field, but the physical system - the field itself - evolves into a state which ...
- 11:07: But what specifically is happening with the weak field?
- 11:36: The combined SU(2)xU(1) symmetry is the electroweak field, and it has 4 massless bosons, like a well behaved symmetry should.
- 11:48: ... symmetry is spontaneously broken - leaving an independent, massless s(1) field for the photon and a massive, broken SU(2) field that gives the massive ...
- 12:39: The very existence of those symmetries requires a family of fields and particles that we now observe in nature.
- 12:47: ... the weak force bosons their mass - we have to conclude that really these fields, these symmetries, are ultimately ...
- 12:58: As we’ll see soon, by the Higgs field.
2020-10-27: How The Penrose Singularity Theorem Predicts The End of Space Time
- 01:17: ... point. At that so-called singularity, the gravitational field becomes infinite. But physicists tend to be dubious about ...
- 05:01: ... are the paths traveled by an object in free fall in a gravitational field. The path traveled by a ray of light is called a null geodesic. ...
2020-09-28: Solving Quantum Cryptography
- 09:08: Algorithm applicants have been whittled down from a field of nearly 70 to only 7 finalists and a couple alternates, which were announced in June.
- 12:27: Suppose you have an enormous field dotted regularly with points.
- 14:52: ... a star than outside - cosmic necklaces can be locked into the magnetic fields within the solar plasma so they don’t fall apart ...
2020-09-21: Could Life Evolve Inside Stars?
- 03:00: Quantum fields should also be able to develop topological defects.
- 03:16: But here, the quantum fields themselves changed state due to the rapidly dropping temperature.
- 07:18: ... plasma and magnetic fields may stretch and break necklaces, which could reconfigure them over and ...
- 10:14: So are the stars filled with thriving ecosystems of critters built from fractured quantum fields?
2020-09-08: The Truth About Beauty in Physics
- 03:02: ... who’ve studied the field equations deeply find it supremely elegant - but it’s not ...
- 03:39: Just as with beauty in any field, it’s fundamentally a subjective sense, and so difficult to define.
- 09:39: And then there’s Einstein’s field equations of general relativity.
- 10:46: The first compellingly beautiful aspect of string theory is that gravity, in the form of the Einstein field equations - automatically emerged from it.
- 11:38: The result was the same - the electromagnetic field popped out like magic.
2020-09-01: How Do We Know What Stars Are Made Of?
- 06:04: The brand new field of quantum mechanics was emerging in Europe, and a young astrophysicist named Cecilia Payne had just arrived at Harvard.
2020-08-24: Can Future Colliders Break the Standard Model?
- 01:22: ... was the linear accelerator, or linac, which uses oscillating electric fields to accelerate charged particles in a straight line, while the beam is ...
- 01:32: ... quickly followed - here the particles are still accelerated by electric fields, but now a constant magnetic field causes the beam to spiral outwards ...
- 05:25: ... the known particles and what we expect their masses to be from quantum field theory ...
- 06:02: ... out the interactions of the known particles with the elementary quantum fields on which those particles live, eliminating most of their mass in the ...
- 07:25: ... accelerators like the sun or supernovae or quasars or galactic magnetic fields, which continuously spray the earth with particles at higher energies ...
2020-08-17: How Stars Destroy Each Other
- 04:31: If the white dwarf has a strong magnetic field, the flow of gas from its companion is channeled by that field.
- 04:38: ... charged particles spiral along the magnetic field lines they emit synchrotron radiation, and bright X-ray light is emitted ...
- 05:47: ... because the gravitational field of the compact object is so strong, falling gas reaches incredible ...
- 06:16: ... powerful magnetic field channels high energy particles into a jet that traces a circle across ...
- 09:25: Finally that core is expected to break up in the neutron star’s tidal field and be scattered into the void.
2020-08-10: Theory of Everything Controversies: Livestream
- 00:00: ... of the theory of gravity with quantum theory and with quantum field theory and the rest of the elementary particles and that's the aspect ...
2020-07-28: What is a Theory of Everything: Livestream
- 00:00: ... physicist with an extremely broad background also so he's worked in fields from cosmology to the foundations of quantum mechanics and now ...
2020-07-08: Does Antimatter Explain Why There's Something Rather Than Nothing?
- 06:00: ... neutral and so are hard to even store using electric and magnetic fields. ...
- 08:00: ... where they are slowed down by pulses of radiofrequency electric fields as they travel around the ring. They can then be redirected to a number ...
- 08:50: ... moment - like a tiny bar magnet. ALPHA introduces a new magnetic field that forces the anti-matter to the center of the chamber. In this way ...
- 10:56: ... states that the acceleration of an anti-atom in Earth’s gravitational field should be exactly the same as for an atom, but scientists want to test ...
2020-06-30: Dissolving an Event Horizon
- 10:15: And there’s an enormous amount of energy in the electric field of all those electrons that you smooshed together into the black hole.
- 10:23: In fact the field itself will always generate enough mass to prevent the black hole from losing its event horizon.
2020-06-22: Building Black Holes in a Lab
- 05:25: ... involves the black hole scattering the vibrational modes of the quantum fields that have wavelengths similar to the black hole’s event ...
- 06:12: This perturbs the quantum fields in a way that look likes escaping particles if you’re very far away from the black hole.
- 06:20: ... an analog watery black hole you just replace “vibration in the quantum field” with “ripple on surface of water” and viola, same deal. ...
- 07:24: ... they’ve detected exactly the expected sapping of the “gravitational field” in a vortex black hole analog. In fact, both the analog of energy and ...
2020-06-15: What Happens After the Universe Ends?
- 07:53: ... - they come from the interactions of those particles with quantum fields - the Higgs field in the case of the ...
- 08:01: I’ll come back to why we might expect the mass granted by the Higgs field to change over time.
- 08:39: And that’s precisely true for things like quarks and electrons, which gain their masses from interactions with the Higgs field.
- 08:46: But that only works below a certain temperature - in the extreme temperatures of the Big Bang, the Higgs field could not grant mass.
- 08:57: ... the way, a change in the nature of the Higgs field - if it decayed to a lower energy - could eliminate elementary particle ...
- 12:01: ... entropy at the Big Bang is due to the tiny entropy in the gravitational field at the ...
- 12:20: In CCC, all of the energy - and, importantly, the gravitational field - is smoothed out over infinite time between aeons.
2020-06-08: Can Viruses Travel Between Planets?
- 07:26: ... to the very edge of an atmosphere with the help of the planet’s magnetic field and then swept into interplanetary or even interstellar space by the ...
2020-05-27: Does Gravity Require Extra Dimensions?
- 02:03: If we have a massive object, we can depict the gravitational force (field) from this object as little arrows pointing towards the object.
- 02:10: The density of the arrows at a given distance determines the strength of the gravitational field.
- 02:29: So the density and the strength of the gravitational field drop proportional the surface area of that sphere - that’s 4 pi r^2.
2020-05-18: Mapping the Multiverse
- 01:01: ... mass is concentrated in a small enough space that the gravitational field becomes too strong for even light to ...
- 05:53: ... nice way to map the gravitational field is according to the geodesics of objects in freefall that start ...
- 07:04: With a lot of speed - and I mean a LOT - it’s possible to overcome the anti-gravitational field in the middle of the ring and punch through.
- 13:13: ... charged, or Reissner-Nordström black holes the electromagnetic field within causes massive tension, or negative pressure that produces an ...
2020-05-11: How Luminiferous Aether Led to Relativity
- 12:25: ... talked about the “new aether” as the medium of the gravitational field, and which we now think of the fabric of spacetime. Paul Dirac suggested ...
2020-05-04: How We Know The Universe is Ancient
- 04:40: ... - they also have random motion as they’re tugged by the gravitational fields of nearby galaxies and clusters. We can deal with these “peculiar ...
- 15:09: ... of the fabric of spacetime - the strenght of the gravitational field, if you will. Same as with the rubber sheet analogy in which a massive ...
2020-04-28: Space Time Livestream: Ask Matt Anything
- 00:00: ... be possible starting a show with such a you know ostensibly narrow field of interest hardcore physics and astrophysics but it turns out that ...
2020-04-22: Will Wormholes Allow Fast Interstellar Travel?
- 00:00: ... across fictional universes. But they've also been a very serious field of study for some of the greatest minds over the last century. So what ...
- 01:09: ... with each other. And if you thread the funnels with electromagnetic field lines then they act like charged ...
2020-04-14: Was the Milky Way a Quasar?
- 01:49: ... researchers in the field believe that all supermassive black holes went through violent AGN ...
- 11:16: ... electrons, but in this case, the electrons are accelerated by magnetic fields and are emitting what’s known as synchrotron ...
2020-03-31: What’s On The Other Side Of A Black Hole?
- 01:53: ... us to calculate the path of an object moving in the insane gravitational field approaching a black hole. It even works inside the black hole - beneath ...
2020-03-24: How Black Holes Spin Space Time
- 04:11: ... horizon? In fact it sort of doesn’t actually. Both the gravitational field and its rotation can be thought of as properties of the spacetime ...
- 05:14: ... - the path taken by an object moving freely in the gravitational field - is dragged in the direction of the object’s spin. Gravity Probe B ...
- 10:51: ... It’s the Blandford-Znajek process. In this case you have a magnetic field produced by the flow of material around the black hole in an accretion ...
2020-03-16: How Do Quantum States Manifest In The Classical World?
- 08:44: ... Here’s more evidence, even with the vertically-aligned magnetic fields, which only affect the vertical component of the electron’s spin, we ...
- 11:48: ... the way you set up the experiment - whether you align your magnetic field vertically or horizontally. But ultimately they are states that can ...
2020-02-18: Does Consciousness Influence Quantum Mechanics?
- 15:01: ... and Francisco Martinez asked whether we would get new quantum fields and new particles if other fundamental constants turned out to vary over ...
- 15:14: Well a field is, by definition, anything that takes on a numerical value everywhere in space.
- 15:19: So by the mathematical definition, a spatially-farying constant would be a field.
- 15:25: Would it be a quantum field with particles?
- 15:28: ... theta field yields particles because it has a lowest energy state - a value for ...
- 15:37: ... it's a dip in energy, the field can oscillate within that dip - and that oscillation is our axion ...
- 15:49: ... lead to quantum particles - but perhaps other constants could give us a field. ...
2020-02-11: Are Axions Dark Matter?
- 03:02: ... CP violating, it’s predicted that the neutron should exhibit an electric field like you’d get from a pair of positive and negative charges - an ...
- 03:59: ... ask how can a vacuum, aka “nothing” have structure? Well, in quantum field theories, the vacuum isn’t really nothing. “Vacuum” is the word we use ...
- 04:33: ... way to describe it is that it’s a phase offset picked up by the quantum field as it moves between the different possible minimum energy states of the ...
- 05:16: ... both over space and over time. In other words, make theta a new type of field - a dynamic field rather than a fundamental constant. Theta will then ...
- 06:32: ... this solution is not generally accepted - turning theta into a quantum field is the most promising ...
- 06:54: ... you might recall that in quantum field theory a particle is just an oscillation in a quantum field. So with a ...
- 07:53: ... no electric charge, they can still interact with the electromagnetic field and produce photons via the strong ...
- 08:05: ... turning into a photon - typically in the presence of a strong magnetic field. And photons can turn into axions in a similar ...
- 08:23: ... wall. It goes like this: a light is passed through a strong magnetic field and then blocked by a metal wall. But some photons get converted to ...
- 08:53: One issue may be that we just can’t make sufficiently strong artificial magnetic fields.
- 08:58: ... off electrons and protons in the presence of strong electromagnetic fields. Perfect conditions for producing axions, among other things. So the ...
- 09:45: ... get converted back and forth between axions and photons by the magnetic fields of entire galaxies. That makes them invisible for part of their journey, ...
2020-02-03: Are there Infinite Versions of You?
- 06:08: It means that every particle, or chunk of quantum field, or whatever elementary pixel of reality - has matching properties between the two regions.
- 14:48: But in s-matrix theory and quantum field theory, time and space in the interaction region are fuzzy.
2020-01-27: Hacking the Nature of Reality
- 02:16: ... search for the underlying clockwork of reality led to quantum field theory, in which all particles are described by vibrations in elementary ...
- 02:55: ... electrodynamics, which describes the interactions of the electromagnetic field. ...
- 03:50: ... that space and time should break down at those scales, and our even best field theory hacks seemed to ...
- 04:10: ... the atomic nucleus - not by modeling all the cogs and wheels of the field theory of the internal nucleus, but rather by understanding the ...
- 06:47: Remember, that quantum field theory fastidiously adds together a complete set of virtual interactions that contribute to the real interaction.
- 08:28: In regular quantum field theory you’d need to add up all the different versions of both these two channels separately.
- 09:35: It presented severe challenges on par with those plaguing quantum field theory - and, as it happened, physicists solved the QFT challenges first.
- 09:45: ... approach infinite strength as was once feared, and so a full quantum field theoretic description of the strong nuclear force was possible after ...
- 10:10: ... the results was that S-matrix theory was sidelined, and quantum field theory reigns supreme to this day as our reductionist description of the ...
- 10:41: Quantum field theories like QCD surely gives us insights into the nature of the fundamental workings of the universe.
- 10:47: ... - but it turns out that it has led to deep insights that even quantum field theories could not ...
- 12:56: ... the amplituhedron doesn’t just eliminate the fiddly mechanics of quantum field theory, it removes the very concepts of space and ...
2020-01-13: How To Capture Black Holes
- 04:08: ... - an accretion disk - as it plummets into the insane gravitational field of the central monster. In the case of the largest, most well-fed black ...
- 04:50: ... gas is dragged out of the disk, tugged by the black hole’s gravitational field. Momentum is transferred from black hole to gas, slowing the black hole ...
- 09:31: ... suddenly finds itself moving too quickly for the reduced gravitational field of the final black hole. It creates an expanding expanding shock-front ...
- 12:17: ... large universe that multiplies the density of a high-energy quantum field powering inflation. Check out our episodes on cosmic inflation to expand ...
2020-01-06: How To Detect a Neutrino
- 03:09: ♪ ♪ More magnetic fields are used to sort the positively charged pion particles from the debris ♪ ♪ and focus *them* into a beam.
- 05:52: ♪ ♪ We charge the sides of the detector, so a giant electric field fills the entire tank.
2019-12-09: The Doomsday Argument
- 01:57: ... of magnitude higher according to the crudest predictions of quantum field ...
- 14:57: ... most obvious example is that regular gravitational fields around stars and galaxies can be positively curved patches in a flat or ...
2019-12-02: Is The Universe Finite?
- 06:02: ... galaxies and galaxy clusters - all of which have enormous gravitational fields that act as lenses, slightly deflecting the path of those rays of CMB ...
- 13:33: ... stuff over a beer, and some who are laser focused on their own field and don't really think far beyond ...
2019-11-11: Does Life Need a Multiverse to Exist?
- 08:05: ... are determined by the interaction of those particles with the Higgs field - but again, there’s no apparent pattern and we don’t know why they take ...
- 09:04: ... quantum fields, which fill all of space and whose oscillations produce the familiar ...
- 10:02: One possibility is that the zero-point energies of unknown quantum fields cancel out the known contributions.
- 13:28: ... core, which may help explain the strength of our protective magnetic field. ...
- 13:56: The result: more iron, less rock, more magnetic field.
2019-11-04: Why We Might Be Alone in the Universe
- 05:59: ... a molten metal outer core, and this motion generates a powerful magnetic field that protects Earth from dangerous space radiation and solar ...
- 06:56: By comparison, Mars is tectonically dead and Venus is at best tectonically weak - certainly neither have protective geomagnetic fields.
2019-10-15: Loop Quantum Gravity Explained
- 01:58: Like actors on a stage, where the actors are particles and wavefunctions and fields and the stage is the coordinates of space and time.
- 02:54: In string theory, a type of background independence emerges in an abstract space of moving strings and with that comes a gravitational field.
- 04:43: There are other ways to formulate quantum mechanics, like quantum field theory, but these ultimately have the same issue But it gets worse actually.
- 08:47: In this formalism, the “space of metrics” looks just like a space of fields in quantum field theory.
- 09:29: ... loops, with each loop like an elementary closed circuit of gravitational field. ...
- 10:10: Not with chunks of spacetime but with quantum circuits of gravitational field.
- 16:29: ... the answer lies in the Einstein field equation of general relativity That equation says that the amount ...
2019-09-30: How Many Universes Are There?
- 01:27: Energy locked into something called the inflaton field.
- 01:31: ... that inflating space, tiny patches stop inflating – the inflaton field in that patch loses its energy and so accelerating expansion stops ...
- 02:41: To fully answer these we’d need to know the true physics of the inflaton field.
- 05:59: Remember that it was the high energy density of the inflaton field that drove inflation, and the loss of that energy density that ended it.
- 06:09: But what if the inflaton field retained just a tiny bit of energy after its decay?
- 06:15: That residual field might be what we observe as dark energy.
- 12:42: And it might be very high – especially if the inflaton field is highly correlated from one point to the next, as in slow-roll inflation.
2019-09-23: Is Pluto a Planet?
- 15:45: ... for its inhabitants, but without an actual powerful gravitational field limiting our access to ...
- 16:44: Venus also has no geomagnetic field.
- 16:47: The magnetic field that it does have comes from the interaction of the solar wind with its super thick atmosphere.
- 16:52: But presumedly, we'd need to massively alter and even reduce that atmosphere, if we want to terraform it, which would probably kill the field.
2019-09-16: Could We Terraform Mars?
- 03:33: At 11% the mass of Earth, it has a weaker gravitational field that grips less tightly to an atmosphere.
- 03:39: ... Earth’s core, solidifying long ago and shutting down its global magnetic field. ...
- 03:49: Earth’s magnetic field protects us from the solar wind, as we saw in a recent episode.
- 13:10: We canNOT restart Mars’ magnetic field – to do that we’d have to re-melt the entire core.
- 13:19: The easiest would be to do that in space – an orbiting field generator placed between Mars and the Sun, like a giant space umbrella.
- 16:20: Wabi Sabi asks why the inflaton field is assumed to be a scalar field.
- 16:28: It's because a scalar field is all you need.
- 16:31: This is the simplest type of quantum field, consisting of only a single scalar value at all points in space.
- 16:37: Give such a field a constant energy density and you get exponential expansion.
- 16:42: ... more complex fields like vector fields and spinor fields can do the job too - and some ...
- 16:52: But many physicists argue that you shouldn't add unnecessary complexity, so a scalar field tends to be the default for inflaton.
- 16:59: Joshua Kahky asks whether the Inflaton Field could also explain Dark Energy.
- 17:08: Inflation supposedly happened because the inflaton field had a very high energy density, and it stopped when that energy dropped to a very low value.
- 17:20: ... the inflaton field was left with a very tiny but positive energy density, then it's ...
- 17:32: ... for that to happen, the inflaton field would have had to have transitioned between two stable or semi-stable ...
- 17:42: ... we can try to imagine a single field with that property, or we can imagine two separate fields - It's not ...
- 18:06: ... points out that while Venus lacks an Earth-type intrinsic magnetic field, the solar wind striking its atmosphere creates an induced magnetic field ...
- 18:23: Electrical currents are induced and these produce a magnetic field that pushes back against the Sun's magnetic field.
2019-09-03: Is Earth's Magnetic Field Reversing?
- 00:00: Earth’s magnetic field protects us from deadly space radiation.
- 00:22: A geomagnetic field.
- 00:24: ... poles, connecting to each other to wreath the planet in a dipole field, like a gigantic bar ...
- 00:38: Magnetic fields exert a force on moving charged particles, causing them to spiral around those force lines.
- 00:55: Our magnetic field deflects the worst of these.
- 01:10: So what would happen if Earth lost its field?
- 01:21: The magnetic field is currently undergoing rapid changes, possibly signaling the imminent flipping of its polarity.
- 01:56: Magnetic materials like iron often form with their natural fields aligned with Earth’s field.
- 02:02: We can track the direction of Earth’s magnetic field in sedimentary layers and in old volcanic flows.
- 02:09: ... out Earth’s field has completely flipped direction 183 times over the past 84 million ...
- 02:42: Except for the fact that the magnetic field DOES seem to be acting strangely lately.
- 02:54: And for that we need to understand the Earth’s magnetic field.
- 02:58: ... we think of magnetic fields being generated in two way: In magnetic materials like iron, the sum ...
- 03:15: Alternatively, flows of many charged particles like electrons – so electrical currents - can produce magnetic fields.
- 03:41: How, then, does the Earth generate such a gigantic and well-organized dipole magnetic field?
- 05:10: ... all of this motion that together produces Earth’s magnetic field through a process called the dynamo effect – or so most scientists ...
- 05:21: And dynamo theory not only explains geomagnetism, but also why Earth’s field sometimes reverses its polarity.
- 05:42: ... key is that the dynamo effect doesn’t really create a magnetic field from scratch – instead it amplifies, organizes, and sustains an existing ...
- 05:52: I’ll come back to where that initial magnetic field comes from.
- 05:55: For now, let’s say that we start with some weak dipole field.
- 06:00: That field passes through the liquid outer core, which is an electrical conductor.
- 06:05: Conductors have this cool property that they drag magnetic fields with them.
- 06:10: So if the entire core is rotating with the Earth then the magnetic field will also rotate.
- 06:21: As a result, the starting magnetic field gets wound up into rings around the axis of rotation – into a torus shape.
- 06:40: Those flows grab hold of our toroidal magnetic field and twist it up further - into many little loops.
- 06:56: Now we have exactly the conditions of an electromagnet – organized rings of current, which produce our giant dipole field.
- 07:05: OK, so start with a weak dipole field and you get a strong one.
- 07:09: But where does that initial magnetic field come from in the first place.
- 07:13: Well, actually ANY weak field – even random bits of field – for example thermal fluctuations - are enough to initiate this runaway effect.
- 07:23: Once started, the field builds to maximum strength.
- 07:27: ... fact any rotating body with a fluid conductor can produce such a field – the Earth, but also the Sun with its flowing hydrogen plasma, or the ...
- 07:42: The field produced by this effect looks pretty organized, but it’s not as clean as a bar magnet.
- 07:50: In fact Earth’s magnetic field is a highly dynamic beast.
- 08:18: The strength of the field across the surface also changes, and all of these shifts are due to changing flows within the outer core.
- 08:27: OK, so what’s all this about the magnetic field flipping over?
- 08:30: In fact, HOW can it flip? – surely the direction of the magnetic field depends on the direction Earth is spinning.
- 08:50: ... fact, we expect that if the magnetic field were switched off entirely, it would reestablish itself randomly, with ...
- 09:03: In the geological record there seems to be no pattern to when the field flips, nor to which alignment is preferred.
- 09:12: Earth’s magnetic field isn’t necessarily switched off, but it’s scrambled in some way.
- 09:21: ... it does a full flip we call it a geomagnetic reversal, and when the field just glitches but ends up in the same direction it started we call it a ...
- 09:51: ... the chaotic motion of outer-core fluid causes a tangling of magnetic field lines and a global drop in field ...
- 10:18: ... show that the dynamo effect should indeed produce a large-scale dipole field that spontaneously reverses, although the details are still a little ...
- 10:57: ... international World Magnetic Model is a global maps of Earth’s magnetic field updated every 5 years – in the past that’s been frequent enough to ...
- 11:24: But, does this mean the field is preparing to flip?
- 11:29: I mean, maybe - but we know that the field must fluctuate quite a bit even when it’s not about to reverse.
- 11:50: Like I said, the field weakens but doesn’t switch off completely.
- 12:06: The field also becomes very messy – with mini north and south magnetic poles popping up across the surface of the planet.
- 12:24: ... scientists have a pretty good idea, and think that Earth’s magnetic field is likely to hold out for our lifetimes – and those of some generations ...
- 13:04: ... millions of refrigerator magnets to protect us once the Earth’s magnetic field ...
2019-08-26: How To Become an Astrophysicist + Challenge Question!
- 00:00: ... the information science of genetics turns out many many other fields science and otherwise Want the analytical skills of all brands of ...
- 08:00: ... once you have that PhD your options open up massively both in the field and out of it Okay, this gets me to the big question Should you pursue a ...
2019-08-19: What Happened Before the Big Bang?
- 00:50: The idea is that the energy trapped in the so-called "Inflaton field" caused exponential expansion of space.
- 01:36: ... inflation, if it actually happened, was driven by the inflaton field, which had the bizarre property of containing a ton of energy even in the ...
- 01:50: Now, in a recent episode we talked about how such a field could drive exponential expansion.
- 01:56: But we stopped short of discussing what the field actually is and what the real implications are of its existence.
- 02:03: ... of an inflating universe, we probably should know more about the field that drives it. To start with, you need a particular type of field to ...
- 02:17: This is actually the simplest type of quantum field because it's described by a single number, a scalar everywhere in space.
- 02:24: Other fields like the particle field or the electromagnetic field are described by multiple components and vectors instead of single numbers.
- 02:33: We know that scalar fields exist, or at least one does.
- 02:37: That's the Higgs field which gives elementary particles their mass.
- 02:41: The inflaton field would be another such scalar field, or it might even be the Higgs field.
- 02:50: I mentioned last time that quantum fields can hold energy without actually having particles.
- 02:58: You can think of a field with a high field strength as being full of virtual particles.
- 03:03: These are ephemeral vibrations in the field that are constantly tugging at the field as the field tugs at them.
- 03:11: This self interaction gives the field some potential energy.
- 03:15: ... potential energy because the field would much rather reconfigure itself into a lower energy state. In which ...
- 03:27: Although scalar fields are the simplest, they can exhibit complicated relationships between this potential energy and the field strength.
- 03:43: Guth's idea is that there's a local minimum in potential energy that allows the inflaton field to get stuck in a false vacuum state.
- 04:35: ... idea of slow roll inflation is that the inflaton field isn't stuck at a local minimum in the potential but rather it's on a ...
- 05:41: Before we get to that, I want a quick word on why the Inflaton field should have one potential energy curve over any other.
- 05:49: Now, the behavior of this field depends on some unverified physics But a suitable inflaton field fits with some grand unified theories.
- 06:09: These theories predict phase transitions in the behavior of fields as the temperature of the universe changes.
- 06:17: As the universe cools, different vacuum states can appear possibly trapping the inflaton field.
- 06:49: I mentioned that quantum fields fluctuate due to the intrinsic randomness of the quantum world.
- 06:54: As the inflaton field rolls down the potential energy hill, the field strength should fluctuate slightly.
- 08:06: ... expansion should grind to a halt over large regions as the inflaton field decays As I mentioned, small fluctuations in the Inflaton field would ...
- 08:45: To further up the slope, the inflaton field gets pushed the faster that expansion.
- 09:34: Assuming a quantum field of the right type and that speck will start inflating.
- 09:52: How plausible is this mysterious inflaton field?
- 11:46: Then an ocean of inflaton particles released by the decaying inflaton field turned into extremely energetic particles and radiation.
2019-08-12: Exploring Arecibo in VR 180
- 00:55: We're right near the edge of the dish In a second, Arecibo is gonna fool your entire field of view.
- 01:02: ... it's over 300 meters in diameter That's a surface area of 26 football fields And no you can't play football on the dish or skateboard. I asked next. ...
2019-08-06: What Caused the Big Bang?
- 04:42: We need some quantum physics. In fact, we need some quantum field theory.
- 04:55: There's some more homework for you. For now, a review: the universe is filled with quantum fields.
- 05:02: Now, a field is just some property that takes on a numerical value at every point in space.
- 05:07: We call that the "field strength".
- 05:09: The field strength determines how much force a quantum field exerts on other fields and particles.
- 05:16: A familiar example is the magnetic field. The stronger the field, the more it pulls or pushes.
- 05:22: ... the way, an elementary particle is just an oscillation in this field strength - a little packet of energy held by the field. If a quantum ...
- 05:45: ... quantum field can contain an intrinsic energy even without particles. In that case, it ...
- 06:05: Now, a field doesn't just jump to the lowest energy state, it makes its way there by changing the field strength one step at a time.
- 06:14: ... we graph a quantum field potential energy versus field strength, it might look something like ...
- 06:29: And by the way, the lowest energy state of a field is called its vacuum state.
- 06:35: But sometimes, the energy contained by a field has a more complex relationship with the field strength.
- 06:47: For now, let's just go with it. One possibility is that the field could have what we call a local energy minimum.
- 06:55: If such a quantum field found itself near that local minimum then it would roll to the bottom and get stuck there.
- 07:13: There are other ways for a field to end up with a positive vacuum energy density and I'll come back to these.
- 07:19: But for now, let's just assume that such a field exists and give it a name: "the inflaton field".
- 07:26: ... something like this: In the early universe this mysterious in flattened field has a high field strength due to the extreme temperatures of that time. ...
- 07:50: The universe keeps cooling, but the inflaton field can't lose more strength.
- 07:59: ... and cools it to a low temperature. In fact, it super cools the inflaton field. ...
- 08:16: ... field remains in a vacuum state that doesn't matches temperature - in the same ...
- 08:29: ... and the corresponding super cooling would go on forever if the inflaton field stays stuck. But quantum fields have a tendency to randomly fluctuate to ...
- 08:43: Somewhere in the inflating universe, the inflaton field is going to fluctuate to the other side of this local minimum barrier.
- 09:07: ... of the local minimum towards the true vacuum and so the entire inflaton field would cascade down in ...
- 09:30: The inflaton field also undergoes a phase transition towards the new vacuum state.
- 10:04: The energy that existed in the inflaton field doesn't just go away, it remains in that field very briefly, but now in the form of inflaton particles.
- 10:14: ... like the entire floor of the field is shifted down at every point in space; what was once pure inflaton ...
- 10:26: ... and they very quickly disperse their energy into the other quantum fields. The inflatons decay into the familiar particles of the standard model - ...
- 12:12: ... even better solutions, mostly by changing the nature of the in flattened field so that allows a smooth exit from inflation across the universe rather ...
2019-07-25: Deciphering The Vast Scale of the Universe
- 02:05: ... so quickly that they would surely escape the Milky Way’s gravitational field. ...
2019-06-17: How Black Holes Kill Galaxies
- 06:33: ... the surrounding galaxy or its channeled into jets by powerful magnetic fields. ...
2019-06-06: The Alchemy of Neutron Star Collisions
- 02:47: ... collision itself but most remain trapped in the intense gravitational field of the newly formed black hole presumably doomed to fall into the event ...
2019-05-09: Why Quantum Computing Requires Quantum Cryptography
- 04:58: Polarization defines the direction that its electric and magnetic fields … wave.
- 14:23: It’s an exciting narrative that explores the importance of collaboration in the field of scientific discovery.
2019-05-01: The Real Science of the EHT Black Hole
- 05:39: It’s also blasting out a jet of energetic particles, channeled by the intense magnetic fields around the black hole.
- 07:59: Synchrotron results from electrons spiraling in magnetic fields.
- 08:55: ... simulation that weaves in all of the physics of fluid flow and magnetic fields, in this case with the addition of the warped spacetime of a black hole ...
2019-04-24: No Dark Matter = Proof of Dark Matter?
- 00:03: ... we'd see the warping of of more distant stars in their gravitational fields in other words we'd see their gravitational lensing all known particles ...
2019-04-10: The Holographic Universe Explained
- 01:02: We’ve moved from quantum field theory to black hole thermodynamics to string theory.
- 04:45: Those rules are a field theory, the lattice itself is the field, and the cells are some elementary component of the field.
- 05:08: Probably the rules between cells – the field theory – depends on this scale.
- 05:33: We’re going to say our field theory is scale-invariant.
- 05:57: A field theory with this property is called a conformal field theory.
- 06:09: A conformal field theory has this property.
- 06:25: By making this a conformal field theory we’ve added a symmetry –invariance under local changes in scale – also known as Weyl invariance.
- 10:23: ... just like a Minkowski spacetime of 3+1 dimensions on which their lived a field theory that arose from interactions between ...
- 10:37: ... itself that field theory wasn’t stringy– rather it was a quantum field theory like the ...
- 10:49: It was also a conformal field theory – a CFT - so it was invariant to the scaling of grid sizes.
- 11:24: The conformal field theory in the original space included no gravity, but in the higher-dimensional space it became a full quantum theory of gravity.
- 11:46: ... interactions in the lower dimensional field theory are extremely strong – we would say the fields are strongly ...
- 11:58: ... strong gravitational fields in the higher dimensional space – like in black holes – look like a ...
- 12:21: The techniques of AdS/CFT correspondence are even extended to disparate fields like nuclear and condensed matter physics.
- 12:37: The lower dimensional CFT space is the surface of the AdS space because the field theory exists where the new dimension becomes infinite.
- 13:23: The rules of interactions between cells on the surface is a quantum field theory.
- 15:28: ... of string theory, while the surface exhibits no gravity - only a quantum field theory similar to the field theory behind the standard ...
- 16:20: That surface contains only a conformal field theory and no gravity.
2019-04-03: The Edge of an Infinite Universe
- 07:16: Only lightspeed paths – or in the language of quantum field theory “massless fields” can access these diagonal boundaries.
- 07:25: ... we write the equations of these fields in Penrose’s compactified coordinates then we can do something that ...
- 08:15: ... connected a quantum field between two points at infinite distance – past and future - where he ...
- 08:26: Then he placed a black hole in between these points and calculated how it perturbed the balance of a quantum field traced between them.
- 14:04: ... realized that if you define a conformal quantum field theory in a 3+1-dimensional Minkowski space, that corresponded to an ...
- 14:31: Quantum mechanics in the form of a conformal field theory in one space is a theory of quantum gravity in a space with one higher dimension.
- 14:49: Every particle, every gravitational effect in the bulk is represented by quantum fields on an infinitely distant surface.
- 17:01: ... the increasing negative potential energy of the cosmic gravitational field, but I think at that level this is all just different interpretations of ...
2019-03-28: Could the Universe End by Tearing Apart Every Atom?
- 00:25: ... in nice galaxies like the Milky Way here the galaxy's gravitational field is plenty strong enough to resist the minuscule effect of dark energy ...
2019-03-13: Will You Travel to Space?
- 12:46: Hey everyone, before we get to comments I want to let you know about the new PBS Digital Studios show, Sound Field.
- 12:52: ... Field is a music show that gives a complete breakdown of songs and artists in ...
2019-03-06: The Impossibility of Perpetual Motion Machines
- 09:37: ... are at directing you to their donate button or selling you a telluric field wellness ...
- 10:45: Alex Taylor has an especially cool dynamo device in which the masses are contained in a magnetic field.
- 13:47: ... either bumping into other charged particles or circling in magnetic fields Fortunately we can model that stuff pretty ...
2019-02-20: Secrets of the Cosmic Microwave Background
- 02:05: ... to flow in reverberate out and then get captured by the gravitational field once more falling back to the centre and that could happen multiple ...
2019-02-07: Sound Waves from the Beginning of Time
- 00:29: [PBS Space Time intro] The field of cosmology and the study of the universe on its larger scales was once the least precise in all of astrophysics.
- 14:33: Remember that things like general relativity and much of quantum field theory are verified to stunning precision.
- 16:08: In so-called bimetric gravity, you can have positive and negative masses, but each is described by its own set of Einstein field equations.
2019-01-30: Perpetual Motion From Negative Mass?
- 00:41: ... curve space in the right way to hold open wormholes and construct warp fields. ...
- 02:12: ... active gravitational mass – that’s the mass that causes a gravitational field, and passive gravitational mass – that’s the mass that responds to a ...
- 02:46: ... you calculate the acceleration of an object in a gravitational field, inertial and passive gravitational mass cancel each other out - as long ...
- 03:48: ... and at the risk of getting way too technical, this is also what quantum field theory predicts: fields with even spin have to work in the opposite way ...
- 04:00: ... time to get into why this is the case, or what the spin of a field even means, but the gravitational field is spin 2 – even - so like ...
- 06:04: ... acceleration in empty space and the feeling of weight in a gravitational field. ...
- 06:17: ... if all masses experience the same acceleration in a given gravitational field, so passive gravitational mass and inertial mass have to be ...
- 06:48: A so-called geodesic path is the trajectory of an object in a gravitational field assuming no additional forces.
- 07:13: That should mean that a negative mass behaves the same in a gravitational field as a positive mass.
- 07:50: This suggests that a positive gravitational field attracts everything, including negative masses.
- 07:57: So what about negative gravitational fields?
- 08:33: All of this assumes the simplistic case of what we call test particles – small objects moving in a much larger gravitational field.
- 10:18: In this case, the basic nature of the positive versus negative gravitational fields – the way the fabric of spacetime gets stretched has to be right.
- 12:15: It also implies that ALL fundamental forces have their directions flipped by the action of the charge of the gravitational field.
- 12:23: I’m pretty sure that breaks quantum field theory as well as general relativity.
2019-01-24: The Crisis in Cosmology
- 14:18: Gravitational lensing is the bending of light by a gravitational field.
- 14:26: ...due to the gravitational fields of more nearby galaxies.
2019-01-16: Our Antimatter, Mirrored, Time-Reversed Universe
- 01:48: ... an array of cobalt-60 atoms in a magnetic field, the cobalt nuclei have angular momenta that will align with a magnetic ...
- 02:02: ... parity and time and this symmetry lies at the foundations of quantum field theory physics must work the same if we flip all of these properties if ...
- 03:02: ... atoms have negatively charged nuclei which means their nuclear magnetic fields point in the opposite direction to regular matter relative to their ...
- 13:52: ... next time - in fact, I really want to address a few points made by FieldStrength on the PBS Space Time subreddit: they covered all the most important ...
- 16:06: ... FieldStrength's other point is that the large undefined parameter space of string theory ...
- 16:49: ... wrong there's not yet a way to properly test his rightness or wrongness. FieldStrength's final point is that the untestability of string theory is connected to ...
- 17:15: ... with those who say that this type of untestability means that the field is not science. String theory may be currently untestable due to the ...
2019-01-09: Are Dark Matter And Dark Energy The Same?
- 05:03: Mass determines the strength and direction of the gravitational field – that’s gravitational mass.
- 10:00: You can build traversable wormholes, Alcubierre warp fields, time-machines, anti-unicorns.
2018-12-20: Why String Theory is Wrong
- 04:42: It also predicted an unknown field, the dilaton field, and a corresponding particle that had never been seen.
- 14:34: ... symmetry to general relativity was wrong, but it inspired the entire field of gauge theory upon which much of our understanding of the quantum ...
2018-12-12: Quantum Physics in a Mirror Universe
- 00:02: ... means it's possible to align the spin of the nucleus using a magnetic field so Wuan team applied a magnetic field to our layer of cobalt-60 and ...
2018-12-06: Did Life on Earth Come from Space?
- 00:37: ... microbes have survived that ejection to escape Earth's gravitational field a chunk of impact debris has to be kicked to a minimum of eleven point ...
2018-11-21: 'Oumuamua Is Not Aliens
- 14:35: ... passing through matter, interactions with the electromagnetic field change the effect of mass of the neutrino by a process analogous to the ...
2018-11-14: Supersymmetric Particle Found?
- 03:52: ... explosions, gamma ray bursts, black hole magnetic fields are all expected to blast high energy particles like electrons and ...
2018-11-07: Why String Theory is Right
- 04:06: More technically, you start to get runaway self-interactions, infinite feedback effects between the graviton and its own field.
- 08:47: That term looks like what you would get if you added the electromagnetic field to the Schrodinger equation.
- 09:02: ... makes it possible to quantize the theory and gives us a very different field, the gravitational ...
- 11:07: ... as local phase invariance required us to add the electromagnetic field to the Schrodinger equation, adding Weyl invariance means we need to add ...
- 11:19: That field looks like a 2D gravity on the world sheet.
- 11:23: It's a projection of the 3D gravitational field.
- 11:35: These are particles, and the first mode looks like the graviton, a quantum particle in the aforementioned gravitational field.
- 11:44: ... you use string theory to write down the gravitational field in what we call the low-energy limit, which just means not in places ...
- 14:26: Uri Nation asks about the photons that mediate the magnetic field or the contact force between two bodies.
- 14:37: These fundamental forces are mediated by fluctuations in the quantum fields of the relevant forces.
- 14:44: ... mathematical building blocks to describe a messy disturbance in the field. ...
2018-10-31: Are Virtual Particles A New Layer of Reality?
- 01:30: ... started out as a trick to make impossible calculations in quantum field theory possible-- possible, at least, for the sort of people who can do ...
- 02:01: So quantum field theory is the machinery behind the standard model of particle physics.
- 02:05: In it, particles are excitations in fundamental fields that exist everywhere in space.
- 02:12: In particle interactions, packets of energy are exchanged between these fields.
- 02:18: For example, two electrons-- excitations in the electron field-- will repel each other by exchanging energy through the electromagnetic field.
- 02:30: ... electron jiggles the electromagnetic field, and those jiggles have a back reaction that jiggles each electron, which ...
- 03:16: In that sense, virtual particles are the building blocks of our approximation of the behavior of quantum fields.
- 03:25: ... electrons, you start by saying each electron interacts once with the EM field, transferring between them energy momentum and one photon worth of ...
- 03:43: Then you add the effects of doing this transfer in two, three, four packets, as well as every other idealized field interaction that you can imagine.
- 04:02: The hope is that by adding together the contributions of enough of these, you can approximate the messy state of the field in the true interaction.
- 04:12: We call these idealized interactions intermediate states or virtual states of the field.
- 04:18: But in reality, the field never exists in these states.
- 04:25: Instead, virtual particles are the mathematical building blocks we use to approximate the complex states of interacting fields.
- 04:58: ... diagrams are an absolutely essential tool in most modern quantum field theory calculations, but they also add to the misconception about ...
- 05:45: Virtual particles are our mathematical representation of the quantum mechanical behavior of fields, and that behavior is weird.
- 07:09: ... energy in a single possible vibrational mode of the underlying quantum field. ...
- 07:20: In a way, a virtual particle represents a pure excitation of the field, an idealized case of perfectly defined momentum.
- 09:06: So the quantum fields are composed of these vibrational modes of all different frequencies/momenta that can be excited to become particles.
- 12:00: So to recap, virtual particles are best thought of as a mathematical device to represent the behavior of quantum fields.
- 12:08: ... perturbation theory as we tried to approximate the behavior of quantum fields. ...
- 12:45: If they represent a physical reality, then there should be no way to do quantum field theory calculations without them.
- 12:53: It turns out there is a version of quantum field theory that doesn't use virtual particles at all.
- 12:59: That will be the family of lattice field theories in which space-time itself is defined on discrete grid.
- 13:17: There is no good reason to believe that virtual particles exist outside the math we use to approximate the behavior of quantum fields.
- 13:25: At best, they can be interpreted as a small component of possibility space for a quantum field doing something real.
2018-10-25: Will We Ever Find Alien Life?
- 04:01: You might remember Tabby's Star, the strange star in the Kepler field that showed these bizarre dips in brightness.
2018-10-18: What are the Strings in String Theory?
- 02:46: ... the existence of unexpected and unwanted vibrational modes in the gluon field of these ...
- 02:58: What's a vibrational mode in a quantum field?
- 03:08: But the only hypothetical massless spin-2 particle is the graviton, the conjectured quantum particle of the gravitational field.
- 03:16: ... the gravitational field is made of quantum particles, which it might be-- we really don't know, ...
- 09:23: There's no way to even think about the shape of the gravitational field on the Planck scale that doesn't produce a hopeless conflict.
2018-10-10: Computing a Universe Simulation
- 00:44: ... like if the tiniest chunks of space time or chunks of quantum field or elements in the abstract space of quantum mechanical states can ...
2018-10-03: How to Detect Extra Dimensions
- 04:03: This relationship also applies to the force felt in a gravitational field.
- 04:16: We do see slight deviations in very strong gravitational fields, like close to the sun.
- 06:07: ... structures of potentially any number of dimensions on which the quantum field and their corresponding particles can ...
- 08:41: ... the gravitational field can extend into this hypothetical extra spatial dimension, then ...
- 12:36: Devin Faux asks whether gravity is maybe the exception to the rule that the forces arise from quantizing [INAUDIBLE] fields.
- 13:32: But it may not be the same sort of changes you get when you quantize, say, the electromagnetic field.
- 13:45: So when you use perturbation theory to calculate an interaction in field theories, feedback effects give infinite loops of interactions.
2018-09-20: Quantum Gravity and the Hardest Problem in Physics
- 03:06: Nowadays, modern quantum field theories fully incorporate the melding of space and time predicted by special relativity.
- 04:14: Hawking, actually, derived the latter by finding a way to unite general relativity and-- in quantum field theory.
- 04:30: In fact, it's very possible to shoehorn the curved geometry of general relativity into the way quantum field theory deals with space and time.
- 05:08: ... by thinking about what it means to define a location in a gravitational field with perfect precision or, in other words, what it means to talk about ...
- 08:10: For example, classical electromagnetism becomes quantum electrodynamics when you quantize the electron field and the electromagnetic field.
- 08:19: But in the resulting math, the new quantum fields still lie on top of a smooth, continuous grid of space and time.
- 08:28: The gravitational field doesn't lie on top of space-time.
- 08:52: In general relativity, the presence of mass or energy warps the gravitational field.
- 09:26: This type of self-interaction or self-energy is seen in other quantum field theories and is hard to deal with, even there.
- 09:33: ... due to its electric charge messing with the surrounding electromagnetic field. ...
- 09:48: ... to calculate a complex interaction, like the buzzing electromagnetic field around an electron, with a series of corrections to a simple, ...
- 10:05: So perturbation theory is applied throughout quantum field theories of the standard model.
- 10:53: But unlike other quantum field theories, there are no simple measurements you can do to renormalize those corrections.
2018-09-12: How Much Information is in the Universe?
- 00:25: ... and galaxies, not to mention space itself, with its fluctuating quantum fields, dark energy, blah blah, stuff ...
2018-08-30: Is There Life on Mars?
- 07:08: ... from the surface of Mars, probably ejected from Mars's gravitational field after another space rock smashed into the ...
2018-08-15: Quantum Theory's Most Incredible Prediction
- 00:17: [MUSIC PLAYING] Quantum field theory is notoriously complicated, built from mind-bendingly abstract mathematics.
- 00:43: We know this because the predictions of quantum field theory stand up to experimental test time and time again.
- 00:50: Quantum field theory describes a universe filled with different quantum fields in which particles are excitations, quantized vibrations.
- 00:59: We've talked about QFT many times before, starting with the very first quantum field theory, quantum electrodynamics.
- 01:07: QED talks about the electromagnetic field whose excitations give us the photon.
- 01:13: ... calculations of QED describe how this field interacts with charged particles to give us the electromagnetic force, ...
- 02:25: It has a dipole magnetic field, basically meaning it has a north and south pole.
- 02:33: If we put a bar magnet in a second external magnetic field, it'll feel a torque, a force causing it to rotate to align with that field.
- 02:42: The tendency of a dipole magnet to rotate in an external magnetic field is its magnetic dipole moment.
- 02:50: ... with a dipole magnetic field has a magnetic dipole moment is basically a measure of how much it would ...
- 03:03: Magnetic fields are produced by moving electric charges.
- 03:06: ... perfect dipole field is produced by charges moving in circles, for example, a loop of wire ...
- 03:16: But in the case of a bar magnet, the source of its magnetic field is a bit weirder.
- 03:21: It mostly comes from the summed dipole magnetic fields of individual electrons in the outer shells of its atoms.
- 03:29: And those electron dipole fields are, indeed, very weird.
- 03:41: ... fields seem intuitive if you think of them as tiny balls of rotating electric ...
- 04:12: Despite not being the same as classical rotation, this quantum spin does grant electrons a dipole magnetic field.
- 04:20: So electrons have a magnetic dipole moment, meaning they feel magnetic fields and act as little bar magnets.
- 04:27: Electrons in atoms feel the magnetic fields produced by their own orbits around the atom.
- 06:09: ... us how a relativistic electron would interact with an electromagnetic field, it still treats this EM field ...
- 06:19: It doesn't consider the quantum nature of the field.
- 06:23: Only the fully developed quantum electrodynamics, the first true quantum field theory, does this.
- 06:29: And QED tells us that the quantum electromagnetic field is a messy, messy place.
- 06:45: This messiness messes with the interaction of the electron and the magnetic field to shift the G factor slightly.
- 07:06: It's really incredible that we can even begin to calculate the effect of the messy buzzing electromagnetic field.
- 07:27: Quantum field theory describes the interactions between particles as the sum total of all possible interactions that can lead to the same result.
- 08:02: So yeah, quantum field theory is a type of madness.
- 08:08: In particular, we've been at Feynman diagrams, which are our best tool for dealing with the absurd complexity of quantum fields.
- 08:17: They represent the possible interactions of the quantum field by way of virtual photons.
- 08:30: A basic interaction of an electron with an EM field is illustrated by this partial Feynman diagram.
- 08:36: An electron encounters a real photon that could represent an external magnetic field.
- 08:54: ... electron undergoes an additional interaction with the buzzing quantum field. ...
- 09:04: ... say, the overall strength of an electron's interaction with the magnetic field when we calculate the electrons magnetic dipole moment and it's G ...
- 09:50: ... there really are infinite ways the electron can interact with the EM field, with crazy networks of virtual particles and virtual matter, anti-matter ...
- 10:45: One way to do it is to watch the way electrons process in the constant magnetic field of a cyclotron, a type of particle accelerator.
- 10:54: Electron spin axes are always slightly misaligned with an external magnetic field, due to quantum uncertainty in the spin direction.
- 11:02: As a result, they feel a torque from that field and persist like a top.
- 14:48: It's pretty firmly established that energy must be pumped into the corona by magnetic fields.
- 14:59: Magnetic fields can do the job in two ways.
- 15:13: Another possible mechanism is through turbulence in waves generated by the rapid motion of magnetic fields.
2018-08-01: How Close To The Sun Can Humanity Get?
- 02:29: ... electric shocks from currents induced by Earth's compressed magnetic field. ...
- 03:47: There's the field experiment, which is essentially, a magnetometer and voltage detector.
- 03:51: It'll directly probe the sun's electromagnetic field and will connect the sun's magnetic activity with the sources of the solar wind.
- 04:00: It will also measure the outward flow of the magnetic field through the pointing flux, as well as the plasma density and electron temperature.
2018-07-18: The Misunderstood Nature of Entropy
- 10:45: ... macrostate that is you, until I see you next week on "Space Time." The field of statistical mechanics has given us some of the most profound insights ...
2018-07-11: Quantum Invariance & The Origin of The Standard Model
- 00:59: Today, I'm going to open the first portal of the standard model and show you the origin of the electromagnetic field.
- 02:24: The standard model is ultimately based on quantum field theory, but we're going to use the Schrodinger equation.
- 07:27: It looks exactly like the type of vector potential that you would have in the presence of an electromagnetic field.
- 07:34: ... to have local phase invariance is for us to introduce a new fundamental field that pervades all of ...
- 07:45: And it turns out that field already exists, and it's the electromagnetic field.
- 08:01: But we didn't just rediscover the EM field, we learned a ton about it.
- 08:24: Any particle that has this kind of charge will interact with and be affected by the electromagnetic field and be granted local phase invariance.
- 09:13: ... we need to apply quantum principles to our field, like considering its internal or self energy and allowing quantized ...
- 09:23: Those oscillations in our new electromagnetic field turn out to be the photon.
- 09:49: ... symmetries are obtusely named, U1, SU2 and SU3, and they predict the fields that give rise to electromagnetism, the weak and the strong nuclear ...
- 10:02: ... fields that arise from these gauge symmetries are called gauge fields, and they ...
- 10:29: ... the greatest mystery here is not the nature of the quantum field nor the connection between symmetry and the fundamental forces, perhaps ...
2018-07-04: Will A New Neutrino Change The Standard Model?
- 04:42: ... and forth between those particles through interactions with the Higgs field. ...
- 12:53: ... off the Moon, you have to contend with its admittedly low gravitational field compared to essentially no such field in the case of ...
2018-06-20: The Black Hole Information Paradox
- 02:57: The gravitational field of a black hole is expected to distort the surrounding quantum fields.
- 11:22: ... new ideas about the nature of information and entropy, exploded the field of string theory, and hinted at the possible holographic nature of ...
- 12:07: ... that will take you from Newton's law all the way through gravitational field and celestial ...
- 13:41: ... a black hole can feel its electric charge given that the electromagnetic field is communicated by photons and photons can't escape the black ...
- 13:53: ... a black hole's electric charge in terms of the classical electromagnetic field which has an existence independent of electric ...
- 14:11: Virtual particles in general are just a way to mathematically account for the infinite ways a quantum field can communicate its influence.
- 14:44: The electromagnetic field outside the black hole knows about the charge inside the black hole.
- 14:49: ... interaction with the interior or just the persistence of the field at the event horizon is a matter of ...
- 14:58: HebaruSan noticed that, in our graphic, the Earth completed 1.75 orbits in the supposed 8 minutes it took the Sun's gravitational field to vanish.
2018-06-13: What Survives Inside A Black Hole?
- 03:13: Let's think about this in terms of fields, and we'll stop with the gravitational field.
- 03:18: Gravity may be caused by mass, but a gravitational field is a very real thing all on its own.
- 03:24: In Einstein's general theory of relativity, we think of the gravitational field as curvature in the fabric of spacetime.
- 03:38: We can think of the gravitational field at any point as being caused by the gravitational field at surrounding points.
- 03:45: Each point on the rubber sheet doesn't actually see the source of the gravitational field.
- 03:54: The Earth orbits the Sun, but more directly it orbits the Sun's gravitational field.
- 04:06: If the Sun were to suddenly vanish, Earth would continue to orbit the existing gravitational field for 8 minutes.
- 04:20: ... inside the black hole, but that mass is remembered in the gravitational field, the curvature of spacetime above the event ...
- 04:53: It's Gauss's law, which applies to both gravitational and electric fields.
- 04:58: ... law of gravity states that the total gravitational field added up over an enclosed surface is proportional to the amount of mass ...
- 05:19: The resulting sum of the gravitational field would be the same.
- 05:36: Now, the original Gauss's law actually applies to the electric field.
- 05:47: ... law for the electric field says that the total electric flux passing through a closed surface ...
- 06:04: This means that the electric field above the event horizon of a black hole remembers all of the electric charge that fell through that surface.
- 06:16: If you've studied some introductory physics, you might remember that the gravitational and electric fields have something in common.
- 06:26: ... for electrostatics say that the strength of the force produced by these fields drops off with the square of the distance from the source of that ...
- 06:37: ... the fact that if you draw increasingly large spheres around a pointlike field source, the intensity of those forces gets spread out over an ...
- 07:08: But both Gauss's law and the inverse-square law work because of a key similarity between gravity and the electric field.
- 07:34: ... of any region of space are remembered in the gravitational and electric fields on the surface surrounding that ...
- 07:59: ... will adjust the black hole's external gravitational and electric fields on its way ...
- 08:38: A changing electric field produces a magnetic field.
- 08:40: And so if the black hole is spinning or racing past you, you'll see that magnetic field.
- 08:46: In a similar way, you can see a black hole's rotation in its gravitational field.
- 09:50: As a result, they are remembered by the fields surrounding the black hole.
- 12:28: QFT describes the evolution of quantum fields in which particles are excited states.
- 12:34: Now it's the evolution of the fields, not the particles, that conserves probability.
2018-05-23: Why Quantum Information is Never Destroyed
- 05:36: ... could mean the wave function of an electron moving in an atom's electric field, or it could mean the wave function of the entire universe in its own ...
- 05:51: ... formulations of quantum mechanics, like the Dirac equation and quantum field ...
- 06:49: And this unitarity is a foundational assumption in all formulations of quantum mechanics and quantum field theories.
2018-05-16: Noether's Theorem and The Symmetries of Reality
- 03:36: It can be lost or gained to the gravitational field.
- 03:39: This is because the direction of the gravitational field changes with respect to the road.
- 03:47: On the other hand, the gravitational field across the whole stretch of road doesn't change from one point in time to the next.
- 04:07: ... under rotation-- for example, the spherically-symmetric gravitational field experienced by a satellite orbiting the earth-- then, Noether's theorem ...
- 07:42: That symmetry is the phase of the quantum field.
- 07:45: ... can rotate the complex phase of an oscillation in a quantum field by any amount, and the observable properties of that field, like its ...
- 07:59: This quantum symmetry is just the simplest of a large number of symmetries exhibited by quantum fields, the so-called gauge symmetries.
- 08:26: It's founded on the fundamental symmetries of quantum fields.
- 09:21: Her contributions to mathematics, particularly abstract algebra, redefined entire fields.
- 11:58: But its extreme precision is possible because it comes back to every field many times over the five years of its operation.
2018-05-09: How Gaia Changed Astronomy Forever
- 06:00: For example, this is the field of stars of the planet hunting, Kepler telescope.
2018-04-25: Black Hole Swarms
- 06:32: Polars are a bit like X-ray binaries, except instead of a black hole or a neutron star, you have a white dwarf with a powerful magnetic field.
- 06:39: ... magnetic fields act like a dam, allowing gas from the companion star to build up and ...
- 07:48: Besides being very cool and kind of freaky, this result is especially important for the new field of gravitational wave astronomy.
2018-04-18: Using Stars to See Gravitational Waves
- 02:19: ... gravitational waves should also be warped by intervening gravitational fields which can amplify the signal and stretch out the ...
- 07:52: ... it may be possible to observe this effect in the dense star fields of galactic cores if those galaxies also contain binary supermassive ...
2018-04-11: The Physics of Life (ft. It's Okay to be Smart & PBS Eons!)
- 11:49: ... a type of friction between the accelerating observer and the quantum field which should inhibit that acceleration by creating a type of ...
2018-04-04: The Unruh Effect
- 00:44: They were independently studying how the nature of quantum fields appears to change depending on whether or not an observer is accelerating.
- 08:02: This particle is coupled to the quantum field of interest, meaning it can exchange energy with that field.
- 08:08: That means the particle can be excited into a higher energy quantum state when it encounters a particle associated with that field.
- 08:36: ... they perform the relativistic field theory calculation to understand the coupling between the detector ...
- 09:06: A charged particle accelerating in a magnetic field emits radiation, bremsstrahlung radiation.
- 09:13: An inertial observer sees the charged particle itself radiating, its energy extracted from the magnetic field.
- 09:58: According to Einstein's equivalence principle, remaining stationary in a gravitational field is equivalent to acceleration in free space.
2018-03-15: Hawking Radiation
- 02:40: ... if you think you're ready, let's take a deep dive into the quantum field theory of curved space time to glimpse the true nature of Hawking ...
- 02:52: Space is filled with quantum fields.
- 03:25: They're really just a tool for calculating the infinite ways in which a fluctuating quantum field can behave.
- 03:32: One way that quantum fields are very different to guitar strings is they can have both positive and negative frequencies.
- 03:51: ... a quantum field is in a vacuum state, there's a balance between positive and negative ...
- 04:11: But spatial curvature can mess with the balance of the underlying quantum field modes by introducing horizons.
- 04:18: Horizons cut off access to certain modes of the quantum fields, disturbing the balance that defines the vacuum.
- 04:25: Stephen Hawking knew that black holes with their insane spacetime curvature would wreak havoc on quantum fields in their vicinity.
- 05:21: Hawking imagined a simple quantum field tracing this path, a field that is in a perfect vacuum state before the formation of the black hole.
- 05:54: ... far from the black hole, regions where the nature of vacuums, quantum fields, and particles are perfectly well ...
- 06:23: These can be used to approximate the effect of curved spacetime on quantum fields by smoothly connecting regions of flat space.
- 06:49: Certain modes of the quantum field are scattered or deflected by the gravitational field of the forming black hole.
- 07:23: The quantum field that emerges is distorted in the same wavelength range.
2018-02-14: What is Energy?
- 04:12: But even a complex path through a gravitational field can be broken down into little, perfectly reversible steps.
- 04:24: The key is that the field doesn't change over time.
- 04:28: ... if the ball follows some path through the field and then retraces its path, the conversion between kinetic and potential ...
- 04:53: ... an object travels between two different points in a gravitational field, it will always experience the same conversion between potential and ...
- 05:07: ... path taken between two points within a conservative force field takes the same amount of work, the same shift between kinetic and ...
- 06:02: If we account for every particle and field involved, then the transaction between kinetic and potential energy is a zero sum game.
- 06:25: ... energy, because that energy is stored in the Earth's gravitational field. ...
- 08:50: ... in Schrodinger's equation to complex interactions of particles and fields in quantum field ...
- 09:26: And the Lagrangian quantum field theory is the basis for high-energy particle physics.
- 09:53: Energy is conserved if the physics of a system, for example, the nature of a force field, stays the same over time.
2018-01-24: The End of the Habitable Zone
- 11:09: Actually, all quantum fields are affected by the presence of a space time horizon.
- 11:14: The vacuum state of all fields are redefined in the vicinity of a black hole or for an accelerating observer.
2018-01-17: Horizon Radiation
- 00:00: ... with, well, the weirdness of special relativity, to give quantum field ...
- 02:22: ... observer dependent particles and vacua, we're going to need some quantum field theory, and we're going to need to draw heavily on this recent ...
- 02:33: In QFT, we think about each particle type as having its own quantum field that exists at all locations in space.
- 02:40: If the field vibrates with a single quantum of energy, we see a particle.
- 02:51: The properties of the particles are encoded in the properties of the fields.
- 03:00: For the laws of physics to be consistent, the fundamental properties of these fields must be the same for all observers.
- 03:26: That means everyone has to agree on the fundamental nature of the quantum fields that describe these particles and the way they interact.
- 03:37: In fact, quantum field theory is what we call Lorentz invariant.
- 04:08: To see how this happens, we need to think about how particles, interactions, and vacuums are described in quantum field theory.
- 04:17: Imagine the simplest type of quantum field.
- 04:52: Now every point in this field, this drum skin is connected to neighboring points.
- 05:35: Quantum wave functions and quantum fields can be described in terms of variation with position or variations with momentum.
- 05:44: So instead of writing the field as having a value at every possible position in space, we can write it as having a value for every possible momentum.
- 05:56: So let's take our spatial quantum field-- our drum skin, with its single, localized particle, and transform to momentum space.
- 06:04: That momentum field also has infinite oscillators, but now each one represents a different possible momentum for the particle.
- 06:59: Now it starts out with no oscillations, analogous to the vacuum state in quantum field theory.
- 08:00: The field at each momentum spot oscillates independently from its neighboring momenta.
- 08:42: There's a nice mechanism in quantum field theory for doing this.
- 08:46: It's called the field operator, and it is our infinite drumstick.
- 09:04: Here, the field operator represents the field properties or the laws of physics.
- 09:46: OK, so what happens when we add a horizon to our infinite quantum field?
- 10:26: ... means we have to reconfigure our old field operator, our infinite drumstick, in order to create and annihilate the ...
- 10:38: We need to rejig the field operator for the laws of physics to be consistent.
- 10:51: Now when you use the new, rejigged field operator to describe the vacuum, some momentum modes that once canceled out no longer cancel out.
2018-01-10: What Do Stars Sound Like?
- 01:54: The fast-growing field of asteroseismology uses these oscillations to probe the interiors of the distant stars.
- 06:11: This differential rotation powers the sun's magnetic field and is also responsible for twisting that magnetic field to drive the sunspot cycle.
- 08:12: ... helioseismic holography, the visible wave field-- so the distribution of Doppler velocities across the visible surface of ...
- 12:26: Felix Schneider asks how electromagnetic radiation can be focused by a magnetic field.
- 12:33: As Felix realizes, light is not electrically charged, and so it isn't affected by EM fields.
- 12:39: In fact, the magnetic field of a gamma ray burst focuses charged particles-- electrons and the nuclei of the exploding star.
- 12:56: The charged particles spiral around the axial magnetic fields and emit photons as they do.
2017-12-20: Extinction by Gamma-Ray Burst
- 03:08: In that case, the powerful magnetic fields can channel the explosion into narrow jets that massively focus and amplify the blast.
2017-12-13: The Origin of 'Oumuamua, Our First Interstellar Visitor
- 04:03: That's the velocity an object would need to have to escape a gravitational field.
- 06:46: Our sun, as it moves around the galaxy, passes through this field of debris.
- 07:11: ... by Pan Starrs, PZ 17 extrapolate to estimate the density of the debris field. ...
2017-12-06: Understanding the Uncertainty Principle with Quantum Fourier Series
- 00:16: ... Heisenberg's uncertainty principle, and ultimately, quantum fields and Hawking ...
- 06:04: Well, before we get back to quantum fields, let's think about the wave function.
- 10:12: So what does this old-school quantum mechanics have to do with quantum field theory and Hawking radiation?
- 10:18: Well, the key to understanding these things is to be able to switch between thinking about quantum fields in terms of position versus momentum.
- 10:26: ... a single particle, a quantum field vibration, perfectly localized at one spot in space, can so be described ...
- 11:01: ... only by manipulating quantum fields in this strange momentum space, by adding and removing these spatially ...
2017-11-22: Suicide Space Robots
- 08:44: ... 2012, it passed the heliopause-- the boundary where the sun's magnetic field and solar wind give way to the ambient environment of the Milky ...
- 11:44: You're clearly a professional in the field.
- 12:00: You say that quantum field theory makes no prediction about the energy of the vacuum.
2017-11-08: Zero-Point Energy Demystified
- 00:32: ... is the prediction of quantum field theory, that there exists an energy of the vacuum resulting from the ...
- 00:43: ... the electromagnetic field alone, this energy density has been estimated to be up to a crazily high ...
- 01:17: Despite this minor glitch, quantum field theory is arguably the most successful theory in all of physics in terms of sheer predictive power.
- 01:35: ... this energy as a free power source to manipulating it to generate warp fields or pushing against the vacuum energy in propulsionalist space ship ...
- 05:02: ... energy can do, like opening wormholes or creating an Alcubierre warp field. ...
- 08:35: ... the theoretical density of the vacuum energy due to the electromagnetic field is estimated by integrating the energy in all possible frequency modes ...
2017-11-02: The Vacuum Catastrophe
- 00:03: The most successful theory in all of physics is arguably quantum field theory.
- 00:51: ... at every point in space-- a non-zero zero point energy in the quantum fields that can briefly manifest as ...
- 01:13: Quantum field theory predicts that the energy of the vacuum should be up to 120 orders of magnitude greater than the measured value.
- 01:30: From the perspective of quantum field theory, every point in space is represented by a quantum oscillator, one for each elementary particle type.
- 02:23: To calculate the density of energy of the vacuum, we should add this tiny energy over an infinite range of frequency modes for all fields.
- 02:51: Let's think in terms of the electromagnetic field.
- 04:39: Long story short-- a crazily high, even infinite, vacuum energy doesn't affect the predictions of quantum field theory.
- 05:53: ... realization of this fact in the early days of quantum field theory was the beginning of what would become the vacuum catastrophe, ...
- 06:07: ... some fields can have extremely large positive zero point energies, then perhaps ...
- 07:39: Compare that to the number predicted by quantum field theory.
- 07:59: ... assume symmetry of positive and negative zero points between different fields, but a very small non-zero vacuum ...
- 08:38: ... exist in an extremely rare universe whose fundamental fields canceled out their zero point energies, at least enough of them to allow ...
- 10:36: That energy comes from shocks that develop as the material flows in the gravitational field of surrounding clusters.
2017-10-19: The Nature of Nothing
- 01:55: Our modern understanding of the quantum nature of space is described by quantum field theory.
- 02:08: In short, space itself is comprised of fundamental quantum fields, one for each elementary particle.
- 02:15: ... fields oscillate, vibrate with different energies, and those oscillations are ...
- 02:28: Now these fields are quantum fields, which means their oscillations can't just have any old energy.
- 02:57: In fact, the math of quantum field theory is all about going up and down this particle ladder, using so-called creation and annihilation operators.
- 03:21: We call this the vacuum state of the field.
- 03:25: Inside a perfect vacuum, all of the field at all locations should be in the vacuum state, exactly zero energy at all times.
- 04:00: On extremely short time scales, a quantum field exists as a blur of many energy states.
- 04:13: But sometimes the field finds itself with enough energy to create a particle, seemingly out of nothing.
- 04:20: ... particle interactions in the universe, at least as described by quantum field ...
- 07:50: Virtual particle-antiparticle pairs in the space between the orbitals and the nucleus align themselves with the electric field.
- 08:20: ... if quantum fields are abuzz with particles popping into and out of existence, then the ...
- 09:32: ... to be drawn together by a force that matched the predictions of quantum field ...
- 10:53: ... field theory, with its dependence on virtual particles and vacuum ...
2017-10-11: Absolute Cold
- 01:00: Using lasers and magnetic fields, we've now managed to cool certain substances to less than a billionth of a Kelvin.
- 06:21: For example, the quantum fields that fill our universe also fluctuate due to the Uncertainty Principle resulting in what we know as vacuum energy.
- 06:31: And some quantum fields have an intrinsic non-zero zero point before even bringing Heisenberg into it.
2017-10-04: When Quasars Collide STJC
- 04:54: When a black hole feeds, the vortex of infalling plasma-- the accretion disk-- can produce a powerful magnetic field.
- 05:02: That field can accelerate narrow streams of high-energy particles away from the black hole.
- 05:08: Those jets can blast through the surrounding galaxy and beyond, carrying their magnetic fields with them.
- 05:15: The radio light seen here is from electrons spiraling in those magnetic fields, so-called synchrotron radiation.
- 13:15: ... suggests that the three-component SU2 boson field in the electroweak Lagrangian should have had mu as a superscript ...
2017-09-28: Are the Fundamental Constants Changing?
- 00:30: [MUSIC PLAYING] The laws of physics are the relationships we observe between space and time, and the fields and particles that occupy it.
- 03:42: In the language of quantum field theory, it's the coupling strength between the electromagnetic field and a charged field like the electron field.
- 05:22: They have magnetic fields, just like a little bar magnet, or electric currents rotating in a ring even though there is no actual rotation.
- 05:31: These same electrons are also orbiting the atomic nucleus, and that motion generates its own magnetic field.
- 05:38: ... magnetic fields produced by an electron's spin and by its orbital motion actually ...
- 05:48: There are two stable configurations for this interaction-- the little bar magnet may be aligned with the orbital field, or opposite to it.
- 05:55: Alignment with the field is the more stable state.
- 13:17: It would then look back at light lensed in the sun's gravitational field.
2017-09-13: Neutron Stars Collide in New LIGO Signal?
- 02:39: ... rotate up to thousands of times per second and have enormous magnetic fields that result in jets of near light speed particles that sweep through ...
2017-08-16: Extraterrestrial Superstorms
- 08:10: ... cloud chemistry, a magnetometer for measuring Jupiter's intense magnetic field, and a four-color wide-field ...
2017-08-10: The One-Electron Universe
- 04:58: In a quantum field theory that's consistent with Einstein's special relativity, all particles must be symmetric under what we call CPT transformation.
- 06:22: ... as time-reversed matter is extremely useful in simplifying quantum field theory calculations, because it massively cuts down the number of ...
- 08:23: We now think of electrons as oscillations, as waves, in the more fundamental electron field.
2017-08-02: Dark Flow
- 00:30: Galaxies whirl within the gravitational fields of giant clusters.
2017-07-26: The Secrets of Feynman Diagrams
- 01:51: Then, you are going to apply them to do some quantum field theory yourself.
- 02:02: The first and most predictively powerful quantum field theory, QED, talks about the interaction of the electron field with the electromagnetic field.
- 02:50: For this to be interesting, the electric and electromagnetic fields need to interact.
- 04:24: That's all the ways that the electromagnetic and electron fields can interact.
- 10:02: ... Feynman diagrams an incredibly powerful tool in simplifying quantum field theory calculations, vastly reducing the number of contributing ...
2017-07-19: The Real Star Wars
- 14:40: ... we talked about tricks for solving the impossible equations of quantum field ...
- 15:30: The so-called bare mass of an electron comes from its interaction with the Higgs field.
- 15:36: ... the self energy interaction, but it's analogous in some ways the Higgs field exchange is weak hypercharged with the electron via W bosons, causing ...
- 15:56: ... mass comes from its interaction with other fields, be it the Higgs field for the bare mass, or the electromagnetic field ...
- 16:51: Every one of those vertices represents an interaction between the electron and the electromagnetic fields.
- 16:57: The probability of that interaction is governed by the coupling constant between those fields.
- 17:28: ... every additional interaction between the EM and the electron field, so every additional vertex, another one of these 1% probability events ...
2017-07-12: Solving the Impossible in Quantum Field Theory
- 00:06: Quantum field theory is stunningly successful at describing the smallest scales of reality, but its equations are also stunningly complex.
- 00:27: ... PLAYING] The equations of quantum field theory allow us to calculate the behavior of subatomic particles by ...
- 00:42: ... even the most elegant and complete formulations of quantum field theory, like the Dirac equation or Feynman's path integral, become ...
- 01:26: ... give you an idea of how messy quantum field theory can be, let's look at what should be a simple phenomenon-- ...
- 01:38: In old-fashioned classical electrodynamics, we think of each electron as producing an electromagnetic field.
- 01:46: That field then exerts a repulsive force on the other electron.
- 01:58: But in quantum field theory, specifically quantum electrodynamics, or QED, the story is very different.
- 02:06: We think of the electromagnetic field as existing everywhere in space, whether or not there's an electron present.
- 02:13: Vibrations in the EM field are called photons, what we experience as light.
- 02:18: The electron itself is just an excitation, a vibration in a different field-- the electron field.
- 02:25: And the electron and EM fields are connected.
- 03:08: ... these pictorial tools to organize the painful mathematics of quantum field theory, but they also serve to give a general idea of what these ...
- 05:53: With infinite possible interactions behind this one simple process, a perfectly complete quantum field theoretic solution is impossible.
- 06:07: This is the philosophy behind perturbation theory, an absolutely essential tool to solving quantum field theory problems.
- 08:36: This latter case can be thought of as the electron causing a constant disturbance in EM field.
- 10:27: ... can be used to eliminate many of the infinities that arise in quantum field theory-- for example, the infinite shielding of electric charge due to ...
- 11:01: Nonetheless, renormalization saved quantum field theory from this plague of infinities.
- 11:26: ... make Feynman's doodles an incredibly powerful tool for using quantum field theory to predict the behavior of the subatomic ...
- 12:07: The two-episode documentary "The Ultimate Formula" gives a really nice history of the development of quantum field theory.
- 13:12: Last week, we talked about Richard Feynman's brilliant contribution to the development of quantum field theory with his path integral formulation.
2017-07-07: Feynman's Infinite Quantum Paths
- 01:03: You might also want to catch up on the first two in our quantum field theory playlist because we are going to be building on that.
- 02:53: But it led to the most elegant formulation of quantum mechanics ever devised and became a key to quantum field theory.
- 08:42: But perhaps the greatest power of the path integral is that it very naturally converts into a true quantum field theory.
- 09:31: ... this weirdness because it's able to describe a universe of oscillating fields just as well as it can describe a universe of moving ...
- 09:44: Instead of adding up all possible paths that particles can take, you instead add up all possible histories of quantum fields.
- 09:54: So a photon is an excitation of vibration in the electromagnetic field.
- 10:04: The quantum action principle gives the probability amplitude of changes in the state of the field.
- 10:10: ... amplitude of a photon's energy moving from the electromagnetic field into, say, the electron field, where it might become an ...
- 10:25: ... the quantum field version of path integrals, we can describe all possible paths and all ...
- 12:56: OK, now let's get to your comments on our episode on quantum electrodynamics, the first quantum field theory.
- 13:04: Jakub asks, what is the difference between the electromagnetic field of quantum field theory and the aether?
- 13:53: But the EM field does.
- 13:56: The crucial difference is that this field has no preferred reference frame.
- 13:59: No matter what speed you're traveling, it's as though the field is stationary with respect to you.
- 15:00: A few of you asked whether quantum field theory and string theory are the same thing.
- 15:07: Quantum field theory describes particles as a field vibration in 4D space-time.
- 15:13: And each elementary particle has its own field.
2017-06-28: The First Quantum Field Theory
- 00:17: I'm talking about quantum electrodynamics-- the first true quantum field theory.
- 00:55: And by far the most successful, most predictive formulation of quantum mechanics is quantum field theory.
- 01:07: And the first part of quantum field theory that was derived, quantum electrodynamics, is the most precise, most accurate of all.
- 01:18: ... Field Theory, QFT, describes all elementary particles as vibrational modes in ...
- 01:30: Quantum ElectroDynamics, QED, provides this description for one such field, the ElectroMagnetic field.
- 01:38: The pillars of QED are the description of the behavior of the EM field and the description of the behavior of the electron via the Dirac equation.
- 01:55: Now before we start thinking about vibrating quantum fields or even fields at all, let's talk about vibrations.
- 03:29: We describe air density as a field because it has some value everywhere in the space of the room.
- 03:36: And that's all a field is-- some property that has some value throughout a space.
- 04:16: Light is a wave in the electromagnetic field.
- 04:19: The electromagnetic field is similar to the density field in a room full of air.
- 04:24: It has a value-- a field strength.
- 04:26: Everywhere in the universe, that value is usually zero, but just like the string or the air density field, it could oscillate.
- 04:36: The electromagnetic field is a quantum field and so these oscillations have a minimum amplitude.
- 07:12: Instead of quantizing particles' physical properties like position and momentum, as did Schrodinger, Dirac quantized the electromagnetic field itself.
- 09:40: ... energy levels due to electron spins-- spins interacting with magnetic fields in the so-called hyperfine splitting or spins interacting with vacuum ...
- 10:23: It required different rules for the fields.
- 10:48: Remember, this approach began with thinking of photons as oscillations in the electromagnetic field.
- 10:55: So does this mean that all particles are also oscillations in fields?
- 11:02: In fact, every base elementary particle has its own field.
- 11:07: It is its own field.
- 11:10: This is the postulate of quantum field theory.
- 11:13: Fields are fundamental and particles and their antimatter counterparts are just ways in which that field vibrates.
- 11:22: There's an electron field whose oscillations are what we know as the electron and the antielectron.
- 11:28: ... are fields for every type of quark-antiquark pair, for every type of force-carrying ...
- 11:43: The calculations of QED and of all quantum field theory are about counting the number of ways a quantum phenomenon can occur.
- 11:58: In fact, a huge part of quantum field theory is about taming the infinities that arise in any calculation.
- 13:21: Last week, we began our discussion of quantum field theory by looking at the amazing Dirac equation and how it predicts the existence of antimatter.
2017-06-21: Anti-Matter and Quantum Relativity
- 00:24: And the emerging field of quantum mechanics had radically altered our understanding of the fundamental building blocks of the universe.
- 02:47: For example, an electron's spin causes them to align themselves with magnetic fields, just like a rotating electric charge would.
- 04:26: But when a magnetic field is present, spin direction becomes very important.
- 04:31: So for fast moving electrons and for electrons in electromagnetic fields, the Schrodinger equation gives the wrong answers.
- 06:02: The Dirac equation perfectly predicts the motion of electrons at any speed, even in an electromagnetic field.
- 06:38: ... example, a lone electron moving in an electromagnetic field could keep releasing energy as light infinitely, and sink lower and ...
- 08:31: But it was one of the first attempts to describe something very real, the idea of a quantum field.
- 08:38: We now know that every elementary particle has an associated field, that fills all of space.
- 08:44: These fields are more like membranes than infinitely deep oceans.
- 08:53: And the elementary particles that we know and love are just regions where a field has a bit more energy.
- 08:59: That energy manifests as vibrations in the field.
- 09:02: Now, quantum field theory is a very deep topic.
- 09:34: Well, it's a vibration in the same quantum field as its regular matter counterpart.
- 10:06: They are two sides of the same coin, positive and negative energy solutions of the same type of vibration in the electron field.
- 10:20: So all elementary particles have a quantum field and all have an anti-matter counterpart.
- 11:03: ... was also a key step in the discovery of quantum field and quantum field theory and the development of the standard model of ...
- 14:02: ... vacuum field can have one or more local minima, where the vacuum energy can come to a ...
2017-06-07: Supervoids vs Colliding Universes!
- 08:10: Also, the control field gave roughly the right answer, which it shouldn't have if our understanding of gravity was so far off.
2017-05-17: Martian Evolution
- 04:17: A mother's pelvis needs to be able to withstand significant pressure that has nothing to do with the gravitational field.
- 07:20: These bombard the surface due to the sparse atmosphere and the absence of a protective magnetic field.
- 13:15: ... sun due to the powers of their light bending in the suns gravitational field. ...
2017-05-03: Are We Living in an Ancestor Simulation? ft. Neil deGrasse Tyson
- 03:43: Let's avoid the idea that the entire universe is simulated, right down to every atom, electron, or vibrating quantum field.
2017-04-19: The Oh My God Particle
- 06:00: We build artificial ones on Earth using giant rings and powerful magnetic fields.
- 06:18: When a star explodes, the expanding shock wave carries a strong magnetic field.
- 08:29: Part of the challenge in understanding cosmic rays is that our atmosphere and magnetic field shield the surface of the earth so well.
2017-04-05: Telescopes on the Moon
- 06:23: ... a cylindrical container of liquid is rotated into a gravitational field, the liquid assumes a smooth parabolic shape, exactly the shape needed to ...
- 11:03: Hydroelectric power plants on earth do it with the flow of space time that we experience as Earth's gravitational field.
- 11:33: ... electric field in a charged black hole at the singularity is expected to produce an ...
2017-03-29: How Time Becomes Space Inside a Black Hole
- 02:56: This comes from Karl Schwarzschild's solution to the Einstein field equations, the very first accurate description of a black hole.
- 06:04: Send out a burst of future defining light rays, and they won't spread out evenly because they bend towards the gravitational field.
- 12:28: Colin Brown asks if the spin flip oscillation is only dependent on the electromagnetic field oscillation.
- 12:36: Firstly yeah, these time crystals oscillate at an integer multiple of the electromagnetic field frequency.
- 12:43: So the time crystal oscillation and the EM field oscillation are in resonance.
- 12:49: For every one, two, three, et cetera cycles of the time crystal, the EM field gives a little push.
- 12:55: ... has to be an integer factor, because if the EM field were pushing halfway through the time crystal period, it would be ...
- 13:38: That would be special and weird, even if the original period was defined by an external EM field frequency.
- 13:54: ... internal oscillations that resisted changes from the outside forcing EM field ...
2017-03-15: Time Crystals!
- 04:13: Spins in nearby atoms like to line up with each other due to interacting magnetic fields.
- 05:09: ... laser, or continue oscillating at least for a while if the input EM field is ...
- 05:29: So two, three, four, et cetera spin oscillations for every EM field oscillation in the laser.
2017-02-15: Telescopes of Tomorrow
- 08:07: This is possible because of the giant field of view of its car-sized 3.2 gigapixel camera.
- 10:19: Alex Filippenko's course, "Understanding the Universe," is a pretty incredible survey of pretty much the entire field of astronomy.
2017-01-25: Why Quasars are so Awesome
- 05:07: This may be due to the magnetic field of a rapidly rotating black hole, but the jury is still out.
2017-01-19: The Phantom Singularity
- 04:16: ... the gravitational field is too strong-- say, near a star or a black hole-- Newton's law gives ...
- 04:45: ... what you get when you solve the delightfully complicated Einstein field equations for the simple case of a spherically symmetric mass in an ...
- 14:45: But these sorts of, huh, that's odd, moments are exactly what burst open new fields of study.
- 16:22: ... expect when you generate temperature differentials and large magnetic fields around a very sensitive position measuring ...
2017-01-11: The EM Drive: Fact or Fantasy?
- 01:44: A resonant radiation field is induced inside, so microwave standing waves reflecting between the ends.
- 02:06: ... can be achieved by extracting momentum from the internal radiation field, but with no ...
- 03:01: ... the cavity, then any momentum exchange between the cavity and radiation field gets redistributed again, because the system is ...
- 06:15: ... simple test would be to heat the device without a radiation field to see if that heating produces a similar false positive signal, but ...
- 06:56: This isn't something we can get into properly without first doing some quantum field theory, so I'll keep it brief.
- 07:19: Our understanding of the quantum vacuum in standard quantum field theory doesn't allow you to push off it, like you might row a boat on a lake.
- 08:29: ... different than described by the otherwise amazingly successful quantum field ...
- 11:02: And yeah, extra dishes will both increase the field of view and improve sensitivity.
2017-01-04: How to See Black Holes + Kugelblitz Challenge Answer
- 03:29: This has enabled EHT to map the strange magnetic field structures around the Sag A star black hole.
- 04:15: ... into two or four images as its light passes around the gravitational field of the black ...
2016-11-30: Pilot Wave Theory and Quantum Realism
- 10:56: While regular mechanics has quantum field theory as its relativistic version, pilot-wave theory hasn't quite got there yet.
- 11:05: Quantum field theory pretty explicitly requires that all possible particle trajectories be considered equally real.
- 11:21: This is not consistent with quantum field theory, and so there isn't a complete relativistic formulation of Bohmian mechanics yet.
- 14:25: Sebastian Lopez asks how are the magnetic fields of neutron stars created.
- 14:30: Well, to create and sustain a magnetic field, you need some charge that's moving or spinning in some way.
- 15:06: With their extreme rotation rates, neutron stars support electric currents sufficient for magnetic fields of up to 100 million tesla.
- 15:23: These fields are supported by superconduction of protons beneath the surface.
2016-11-16: Strange Stars
- 02:23: Its immense magnetic field drives jets of material at extreme speeds.
2016-11-02: Quantum Vortices and Superconductivity + Drake Equation Challenge Answers
- 02:11: ... in topology were the culprit behind a strange quantized magnetic field observed in the mysterious "quantum hole effect." These findings will ...
2016-10-19: The First Humans on Mars
- 03:13: Mars's thin atmosphere and lack of magnetic field make shielding critical, especially for a permanent settlement.
2016-09-29: Life on Europa?
- 01:51: ... produce those plumes and then discolored by Jupiter's intense magnetic field. ...
- 02:42: We know that the tidal squeezing from Jupiter's gravitational field provides the energy that keeps Europa's ocean liquid.
2016-09-21: Quantum Entanglement and the Great Bohr-Einstein Debate
- 08:05: Polarization is just the alignment of a photon's electric and magnetic fields.
2016-08-24: Should We Build a Dyson Sphere?
- 05:09: Within 70 years, we have a partial Dyson swarm, and Mercury is nothing more than a debris field.
2016-07-27: The Quantum Experiment that Broke Reality
- 02:01: Of course, we now know that light is a wave in the electromagnetic field thanks to the work of James Clerk Maxwell a century later.
- 02:33: So each photon is a little bundle of waves, waves of electromagnetic field, and each bundle can't be broken into smaller parts.
- 09:54: ... we know that light is a wave in the electromagnetic field and quantum field theory tells us that all fundamental particles are ...
- 12:25: Juno will figure that out by carefully mapping Jupiter's gravitational and magnetic fields.
2016-07-06: Juno to Reveal Jupiter's Violent Past
- 01:52: The conductivity of metallic hydrogen is thought to result in the enormous electric currents that produce Jupiter's prodigious magnetic field.
- 02:02: It's 20,000 times the strength of Earth's field, giving Jupiter the brightest auroras in the solar system.
- 02:23: In the wake of its intense gravitational field, it drags with it its own mini solar system of at least 67 moons and a faint ring system.
- 08:42: As the three outer gas giants plowed through the great field of planetesimals, they scattered this material through the solar system.
2016-06-15: The Strange Universe of Gravitational Lensing
- 02:11: ... stars due to the deflection of their light by the sun's gravitational field. ...
- 02:57: The gravitational field of any massive object converges passing light rays, like a badly designed lens.
- 04:19: Find that configuration, and we've mapped the gravitational field, the distribution of mass of the lens.
- 05:07: You can see the nearby spiral galaxy, whose gravitational field bends spacetime to create these paths.
- 06:13: ... the starry lens galaxy brightens and dims due to the gravitational fields of individual stars in that lens in a process called ...
- 10:48: Same with trying to tunnel out of a gravitational field.
2016-06-08: New Fundamental Particle Discovered?? + Challenge Winners!
- 03:40: So, a higher energy vibration in the Higgs field.
2016-05-18: Anti-gravity and the True Nature of Dark Energy
- 06:34: So he added to his field equations that would give a positive outward acceleration in the second Friedmann equation.
2016-05-11: The Cosmic Conspiracy of Dark Energy Challenge Question
- 02:16: ... the Einstein field equations and in the Friedmann equations that are derived from those, ...
2016-05-04: Will Starshot's Insterstellar Journey Succeed?
- 07:50: ... several other very prominent leaders in their scientific and technical fields. ...
2016-04-20: Why the Universe Needs Dark Energy
- 06:26: But when we tried to describe the universe by reducing the Einstein field equations into the Friedmann equations, we missed something.
- 06:40: ... very same addition to the Einstein field equations that can describe cosmic inflation can also fix this little ...
- 09:43: Within these regions, the shape of spacetime is dominated by the gravitational field of the densely packed matter.
- 09:53: ... to get millions of light years from the Milky Way for the gravitational field of the Milky Way and Andromeda to not dominate the shape of local ...
- 11:05: ... tech fields have a high demand for bachelor's or masters physicists, like medical ...
2016-04-13: Will the Universe Expand Forever?
- 01:33: At the heart of general relativity are the Einstein field equations, which look like this.
- 02:05: ... have 10 independent components, giving 10 independent field equations to describe the response of the fabric of the universe to ...
- 03:14: As the apple rises, its kinetic energy, its energy of motion, is sapped by the gravitational field and converted into potential energy.
- 04:09: By solving the Einstein field equations for the whole universe, of course.
2016-04-06: We Are Star Stuff
- 00:39: ... the building blocks of matter, the elementary fields that fill our universe, and the particles that they manifest through ...
- 11:57: That stuff isn't necessarily true on a curved 2D surface like a ball, nor in curved 3D space, like within a gravitational field.
2016-03-23: How Cosmic Inflation Flattened the Universe
- 06:57: ... the field equations of his general theory of relativity, he added this as a way to ...
- 08:05: And we'll explore exactly what could cause such a weird sort of energetic vacuum real soon-- inflatons, scalar fields, forced vacuums, all of that.
- 13:00: Although the magnetic field of a spinning black hole can also play a part here.
2016-03-16: Why is the Earth Round and the Milky Way Flat?
- 02:34: ... and there's nothing else around, a surface of constant gravitational field is a ...
- 03:15: It's held together by its own gravitational field, which conveniently also keeps me stuck to the surface.
- 06:39: So a relatively solid, rocky planet will fracture and reshape itself into a sphere as long as its own gravitational field is strong enough.
2016-03-02: What’s Wrong With the Big Bang Theory?
- 01:40: In a previous episode, we talked about how the Higgs field gives particles mass.
- 10:51: For example, the solar system is better described with the Schwarzschild metric, dominated by the sun's gravitational field.
2016-02-03: Will Mars or Venus Kill You First?
- 01:23: ... spinning iron core to a halt and essentially turning off its magnetic field. ...
- 04:35: Both thick atmosphere and strong magnetic field are excellent protection against this stuff.
- 08:00: Venus does not generate its own magnetic field.
- 08:03: ... the interaction of the sun's magnetic field with Venus's think atmosphere actually induces something of a protective ...
2016-01-27: The Origin of Matter and Time
- 06:17: ... by mirrored walls, but by interactions with other particles and force fields. ...
- 09:38: However, quarks and electrons gain their intrinsic mass by interacting with the Higgs field.
- 10:04: ... basic vibrations of their quantum fields-- the time that the electron or quark feels-- is felt by the composite ...
2016-01-13: When Time Breaks Down
- 05:20: But Einstein's equivalence principle tells us that a frame suspended in a gravitational field is indistinguishable from an accelerating frame.
- 05:29: And so clocks must also tick slower the deeper they are in their gravitational field.
- 06:22: Quarks and electrons confined first by their coupling with the Higgs field, and then by the forces binding them into atoms.
- 06:38: ... ticking corresponds to interactions between its component particles and fields, in which the internal parts exchange energy, momentum, and other ...
2016-01-06: The True Nature of Matter and Mass
- 04:55: 99% of the mass of the proton is in the vibrational energy of the quarks plus the binding energy of the gluon field.
- 05:08: ... compressed spring-- quarks, bouncing off the walls in the binding gluon field, which itself acts like a compressed spring, holding potential ...
- 05:22: And as we saw recently, even those quarks, as well as electrons, gain their tiny masses from a type of confinement via the Higgs field.
- 05:31: Take away the Higgs field, and they are massless speed of light particles.
- 05:36: ... are prevented from streaming freely through the universe, as well as the fields that confine those ...
- 05:52: Is it just the result of massless particles and fields bumping and sloshing around inside things resisting acceleration?
- 06:33: ... fundamentally the same thing as the feeling of weight in a gravitational field. ...
- 06:55: Same with the compressed spring-- it's harder to accelerate than a relaxed one, and it also feels heavier in a gravitational field.
- 07:11: But mass doesn't just respond to a gravitational field.
- 07:39: So confined massless particles generate a very real gravitational field.
- 08:18: ... In the last episode of "Space Time," we talked about how the Higgs field gives elementary particles ...
- 08:34: Caleb Limb asks, does this mean the Higgs field makes a little friction in space?
- 08:44: The Higgs field isn't like molasses or like a crowd full of physicists.
- 08:53: The Higgs field doesn't slow particles down.
- 09:14: The right-hand electron can interact with the Higgs field by picking up some weak hypercharge.
- 09:44: ... whether there could be a point in space somewhere where the Higgs field takes on the value of zero, and what the ramifications would ...
- 09:55: At extremely high temperatures, the Higgs field takes on a value of 0 everywhere.
- 10:17: Only when the universe cooled down did the Higgs field gain a nonzero value in a phenomenon called spontaneous symmetry breaking.
- 10:33: The ramifications-- we wouldn't have atoms without a nonzero Higgs field.
2015-12-16: The Higgs Mechanism Explained
- 00:53: In the case of the constituents of the atom, it comes from the Higgs field.
- 01:01: To understand how all this works, we're going to need to learn a bit of quantum field theory.
- 01:08: Now, QFT describes the fundamental particles as excitations in fields, fields that fill our entire universe.
- 01:16: For example, the electron is an excitation in the electron field.
- 01:28: But even in a vacuum, the electron field is there.
- 01:32: But now, add some energy to that field at a particular spot, and it's like plucking a guitar string.
- 01:38: The field vibrates, and that vibration is our electron.
- 01:43: ... elementary particle is a vibration in its own field, and these vibrations and fields interact with each other, transferring ...
- 02:02: ... its incredible success, it was strange that quantum field theory, as it stood in the 1950s, gave a perfect description of the ...
- 03:30: But the photon and the electron are both just excitations in their own fields, so why does the electron have mass and the photon not?
- 03:58: It's the Higgs field.
- 05:01: You probably guessed, the Higgs field.
- 05:04: The Higgs field is really weird.
- 05:06: While most quantum fields hover around zero in empty space, the Higgs field has a positive strength at all points in the universe.
- 05:17: ... some stunning quantum weirdness, this complex, multi-component field not only carries the weak hyper-charge, but manages to take on all ...
- 05:29: This makes the Higgs field an infinite source and sink of weak hyper-charge.
- 05:34: ... electron is bombarded by a flow of particles into and out of the Higgs field from all directions, giving and taking away the weak hyper-charge on ...
- 05:44: On its own, the electron would travel at light speed, but trapped in this Higgs field buzz, the electron feels mass.
- 06:04: Well, something like this must be true, because all of the rest of quantum field theory hangs together too well.
- 06:11: We conclude that QFT is essentially correct, but it's an incomplete theory without a mass-giving field.
- 06:19: The Higgs field is the best, least silly option to do this.
- 06:26: Just like the other fields, the Higgs field can vibrate around its baseline value, which gives us the boson.
- 06:36: However, if we observe the particle, then it means the field also exists.
- 07:02: It seems very likely that the LHC did produce the Higgs boson, which in turn would mean that the field exists.
- 07:24: Could the Higgs field also explain things like dark energy, inflation?
2015-10-28: Is The Alcubierre Warp Drive Possible?
- 00:45: ... Roddenberry's choice of the word "warp." Alcubierre constructed a warp field in the mathematical language of Einstein's theory of general relativity, ...
- 01:08: It's Eagleworks Laboratories is actually trying to produce and detect warp fields.
- 02:03: ... around and within a black hole is predicted by solving Einstein's field equations around a point of extreme positive energy ...
- 03:24: ... fact, when you try to do this for the warp field, you find that you need to produce a ring of negative energy density in a ...
- 04:37: ... that you can even make negative mass matter, to make a warp field, some of it would need to go outside the warp bubble, which means it gets ...
- 05:25: Thicken the walls of the warp field, and you get the negative mass/energy requirement down to the equivalent of maybe the moon or even an asteroid.
- 05:33: ... oscillate the warp field, and you hypothetically soften the fabric of space via higher dimensional ...
- 06:10: Now, this sort of wild optimism has inspired NASA's Eagleworks Laboratory to try an experiment to create and detect a warp field.
- 06:18: Now, this would be a field created by positive, not negative, energy density.
- 06:23: ... waves, To measure the tiny changes in path length created by a warp field. ...
2015-10-22: Have Gravitational Waves Been Discovered?!?
- 00:45: There's the slowing of time in gravitational fields.
- 02:25: ... comes from the fact that the speed of light is built into Einstein's field equation, which is necessary for it to be invariant to the Lorentz ...
2015-10-15: 5 REAL Possibilities for Interstellar Travel
- 05:34: Channeled with magnetic fields, these pions provide our thrust.
2015-10-07: The Speed of Light is NOT About Light
- 03:03: So an electric skater monkey on a rollerblading pony generates a magnetic field, obviously.
- 03:08: And I can figure out the field strength from Maxwell's equations based on what I see is the monkey's total velocity.
- 03:27: She sees the monkey moving at only monkey skate speed, and so gets a totally different magnetic field.
- 03:37: We don't measure magnetic field.
- 03:45: See, there's a velocity-dependent trade-off between the electric and magnetic fields.
- 04:55: But the fields are a mess.
2015-09-23: Does Dark Matter BREAK Physics?
- 00:56: Thanks to general relativity, we know that light fall is the curved geodesics of a gravitational field.
- 01:01: Place a strong gravitational field on an axis between a light source and an observer and voila, you basically have a lens.
- 02:02: The standard model of particle physics is basically the periodic table of known fundamental particles and fields.
- 06:58: Sinking down into the depths of quantum field and string theory, you can find all sorts of strange fish, WIMPs, axions, neutralinos.
2015-08-05: What Physics Teachers Get Wrong About Tides!
- 10:09: ... may have heard that in quantum field theory, forces are described as being mediated by some kind of particle ...
- 10:33: ... just instead of quantizing a sort of standard field, you're-- that you think of as a force field, you're quantization ...
- 11:07: But from the philosophical perspective of quantum field theory, you should be able to quantize anything.
- 11:41: ... the other is to try to take field-- classical field theory versions of something and then add to them the ...
2015-06-17: How to Signal Aliens
- 09:57: Yeah, but buoyancy only exists in the presence of a supposed gravitational field.
- 10:02: ... get less dense as you rise in the opposite direction of a gravitational field, because the fluid that's lowered down has to hold up the weight of all ...
2015-06-03: Is Gravity An Illusion?
- 03:36: So in the train car's frame, which is accelerating forward, it's as if there's an additional gravitational field that points backward.
- 03:44: So accelerated frames of reference mimic a gravitational field in the opposite direction of the frames acceleration.
- 03:51: ... you combine that extra fake gravitational field with the actual gravitational field of the Earth, which points down, it ...
- 04:43: ... that with Earth's real gravitational field and it's as though the total gravity inside the car points down and back ...
- 06:35: ... the downward acceleration acts like a fake extra upward gravitational field that, from the perspective of the box, just happens to exactly cancel ...
2015-05-27: Habitable Exoplanets Debunked!
- 05:59: We have to narrow the field.
2015-05-20: The Real Meaning of E=mc²
- 07:12: For instance, there's the potential energy associated with the interactions of electrons and quarks with the Higgs field.
- 07:17: ... energy that electrons and quarks have from interacting with the electric fields that they themselves produce, or in the case of quarks, also with the ...
2015-03-11: What Will Destroy Planet Earth?
- 02:44: Well, Earth and Mars' field gravitational pulls not just from the sun, but also from the other plants-- and from big asteroids too.
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