
20221214: How Can Matter Be BOTH Liquid AND Gas?
 16:40: The answer is almost certainly unfortunately no. Quasiparticles require some sort of nonelementary 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 nearvacuum 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 ...


20221208: 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.


20221123: 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 ...


20221109: What If Humanity Is Among The First Spacefaring Civilizations?
 18:50: ... implied by this interpretation is equivalent to standard quantum field theory, with the timereversed signals corresponding to negative ...


20221026: 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 ...


20221019: 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 ...


20221012: 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, wellunderstood 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. ...


20220928: 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 ...


20220921: 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.


20220914: 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.


20220824: 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 quintessencelike field for various reasons.
 20:07: For example, apparently you can do this eliminate the socalled 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 ...


20220817: 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 quintessencesaturated space ...


20220803: 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 3D pixelated lattice that evolves through time. As with the ...
 12:15: ... our couple quarkgluon 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 ...


20220727: How Many States Of Matter Are There?
 03:47: ... general the field of physics that studies the relationships between the statistical ...


20220630: 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 ...


20220622: 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.


20220615: 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. ...


20220601: 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 ...


20220525: 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 ...


20220518: 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 ...


20220504: 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 ...


20220427: 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 “zeropoint” 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 nonzero 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 nonzero 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 ...


20220420: 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 ...


20220323: 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.


20220316: 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.


20220308: 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 nonlinear 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 welldefined 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 ...


20220223: 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 badlymade ...
 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 ...


20220216: 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 ...


20220210: 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 ...


20220127: 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 ...


20220119: 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 ...


20220112: 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, ...


20211220: 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 4D hyperbolic space are equivalent to objects ...


20211210: 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 ...


20211117: 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.


20211110: 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 multicomponent 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 fasterthanlight 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 causalitybreaking 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.


20211102: 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 spin½ quantum field.
 13:23: ... there’s a Lagrangian for each quantum field which describes how that field and its particles tend to evolve. ...


20211020: 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.


20211013: 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.


20211005: 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. ...


20210915: Neutron Stars: The Most Extreme Objects in the Universe
 01:02: ... the radiation and pressure, and an antigravitational 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. ...


20210907: 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 preinflation 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 ...


20210818: 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 ...


20210810: 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 nonlinear 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 ...


20210803: 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 ...


20210721: 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: Largescale 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 cosmicscale 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. ...


20210707: 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 deHaas 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 ...


20210623: 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 ...


20210616: 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 ...


20210609: 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 ...


20210525: 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.


20210519: Breaking The Heisenberg Uncertainty Principle
 00:25: ... recent g2 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 ...


20210511: 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 ...


20210421: 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 sideeffect 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 type1 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 gfactor 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 ManyWorlds interpretation are there many, many ...


20210413: 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.


20210407: Why the Muon g2 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 gfactor 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.


20210323: Zeno's Paradox & The Quantum Zeno Effect
 06:00: A constant radiofrequency 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 ...


20210316: 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 ...


20210309: 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.


20210224: 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 4velocity 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 socalled inflaton field, or in the final decay of those inflatons at the end of ...


20210217: 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 ...


20210210: 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 1g 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 ...


20210126: 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 ...


20210119: Can We Break the Universe?
 15:23: ... changed depending on the direction and strength of a very weak magnetic field. ...


20210112: 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.


20201222: 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 whitehot 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  socalled spinspin 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.


20201215: The Supernova At The End of Time
 04:32: ... to stop them from collapsing under their own intense gravitational field. ...


20201208: 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. ...


20201118: 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 nonzero vacuum energy so could potentially decay to zero, or ...


20201104: 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 forcecarrying 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 lightspeed 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.


20201027: How The Penrose Singularity Theorem Predicts The End of Space Time
 01:17: ... point. At that socalled 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. ...


20200928: 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 ...


20200921: 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?


20200908: 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.


20200901: 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.


20200824: 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 ...


20200817: 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 Xray 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.


20200810: 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 ...


20200728: 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 ...


20200708: 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 antimatter to the center of the chamber. In this way ...
 10:56: ... states that the acceleration of an antiatom in Earth’s gravitational field should be exactly the same as for an atom, but scientists want to test ...


20200630: 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.


20200622: 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 ...


20200615: 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.


20200608: 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 ...


20200527: 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.


20200518: 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 antigravitational field in the middle of the ring and punch through.
 13:13: ... charged, or ReissnerNordström black holes the electromagnetic field within causes massive tension, or negative pressure that produces an ...


20200511: 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 ...


20200504: 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 ...


20200428: 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 ...


20200422: 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 ...


20200414: 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 ...


20200331: 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 ...


20200324: 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 BlandfordZnajek process. In this case you have a magnetic field produced by the flow of material around the black hole in an accretion ...


20200316: How Do Quantum States Manifest In The Classical World?
 08:44: ... Here’s more evidence, even with the verticallyaligned 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 ...


20200218: 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 spatiallyfarying 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. ...


20200211: 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, ...


20200203: 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 smatrix theory and quantum field theory, time and space in the interaction region are fuzzy.


20200127: 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 Smatrix 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 ...


20200113: 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 wellfed 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 shockfront ...
 12:17: ... large universe that multiplies the density of a highenergy quantum field powering inflation. Check out our episodes on cosmic inflation to expand ...


20200106: 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.


20191209: 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 ...


20191202: 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 ...


20191111: 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 zeropoint 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.


20191104: 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.


20191015: 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 ...


20190930: 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 slowroll inflation.


20190923: 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.


20190916: 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 remelt 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 semistable ...
 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 Earthtype 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.


20190903: 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 wellorganized 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 outercore 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 largescale 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 ...


20190826: 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 ...


20190819: What Happened Before the Big Bang?
 00:50: The idea is that the energy trapped in the socalled "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.


20190812: 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. ...


20190806: 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 ...


20190725: Deciphering The Vast Scale of the Universe
 02:05: ... so quickly that they would surely escape the Milky Way’s gravitational field. ...


20190617: How Black Holes Kill Galaxies
 06:33: ... the surrounding galaxy or its channeled into jets by powerful magnetic fields. ...


20190606: 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 ...


20190509: 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.


20190501: 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 ...


20190424: 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 ...


20190410: 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 scaleinvariant.
 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 higherdimensional 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.


20190403: 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+1dimensional 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 ...


20190328: 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 ...


20190313: 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 ...


20190306: 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 ...


20190220: 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 ...


20190207: 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 socalled bimetric gravity, you can have positive and negative masses, but each is described by its own set of Einstein field equations.


20190130: 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 socalled 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.


20190124: 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.


20190116: Our Antimatter, Mirrored, TimeReversed Universe
 01:48: ... an array of cobalt60 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 ...


20190109: 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, timemachines, antiunicorns.


20181220: 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 ...


20181212: 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 cobalt60 and ...


20181206: 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 ...


20181121: '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 ...


20181114: Supersymmetric Particle Found?
 03:52: ... explosions, gamma ray bursts, black hole magnetic fields are all expected to blast high energy particles like electrons and ...


20181107: Why String Theory is Right
 04:06: More technically, you start to get runaway selfinteractions, 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 lowenergy 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. ...


20181031: 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 spacetime 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.


20181025: 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.


20181018: 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 spin2 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.


20181010: 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 ...


20181003: 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.


20180920: 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 spacetime.
 08:52: In general relativity, the presence of mass or energy warps the gravitational field.
 09:26: This type of selfinteraction or selfenergy 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.


20180912: 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 ...


20180830: 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 ...


20180815: Quantum Theory's Most Incredible Prediction
 00:17: [MUSIC PLAYING] Quantum field theory is notoriously complicated, built from mindbendingly 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, antimatter ...
 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.


20180801: 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.


20180718: 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 ...


20180711: 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 ...


20180704: 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 ...


20180620: 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.


20180613: 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 inversesquare 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.


20180523: 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.


20180516: 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 sphericallysymmetric 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 socalled 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.


20180509: How Gaia Changed Astronomy Forever
 06:00: For example, this is the field of stars of the planet hunting, Kepler telescope.


20180425: Black Hole Swarms
 06:32: Polars are a bit like Xray 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.


20180418: 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 ...


20180411: 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 ...


20180404: 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.


20180315: 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.


20180214: 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 highenergy 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.


20180124: 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.


20180117: 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.


20180110: What Do Stars Sound Like?
 01:54: The fastgrowing 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.


20171220: Extinction by GammaRay Burst
 03:08: In that case, the powerful magnetic fields can channel the explosion into narrow jets that massively focus and amplify the blast.


20171213: 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. ...


20171206: 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 oldschool 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 ...


20171122: 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.


20171108: ZeroPoint 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 ...


20171102: 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 nonzero 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 nonzero 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.


20171019: 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 socalled 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 particleantiparticle 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 ...


20171011: 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 nonzero zero point before even bringing Heisenberg into it.


20171004: 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 highenergy 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, socalled synchrotron radiation.
 13:15: ... suggests that the threecomponent SU2 boson field in the electroweak Lagrangian should have had mu as a superscript ...


20170928: 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.


20170913: 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 ...


20170816: Extraterrestrial Superstorms
 08:10: ... cloud chemistry, a magnetometer for measuring Jupiter's intense magnetic field, and a fourcolor widefield ...


20170810: The OneElectron 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 timereversed 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.


20170802: Dark Flow
 00:30: Galaxies whirl within the gravitational fields of giant clusters.


20170726: 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 ...


20170719: The Real Star Wars
 14:40: ... we talked about tricks for solving the impossible equations of quantum field ...
 15:30: The socalled 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 ...


20170712: 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 oldfashioned 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 twoepisode 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.


20170707: 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 spacetime.
 15:13: And each elementary particle has its own field.


20170628: 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 socalled 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 quarkantiquark pair, for every type of forcecarrying ...
 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.


20170621: AntiMatter 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 antimatter 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 ...


20170607: 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.


20170517: 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. ...


20170503: 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.


20170419: 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.


20170405: 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 ...


20170329: 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 ...


20170315: 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.


20170215: Telescopes of Tomorrow
 08:07: This is possible because of the giant field of view of its carsized 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.


20170125: 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.


20170119: 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 ...


20170111: 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.


20170104: 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 ...


20161130: Pilot Wave Theory and Quantum Realism
 10:56: While regular mechanics has quantum field theory as its relativistic version, pilotwave 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.


20161116: Strange Stars
 02:23: Its immense magnetic field drives jets of material at extreme speeds.


20161102: 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 ...


20161019: The First Humans on Mars
 03:13: Mars's thin atmosphere and lack of magnetic field make shielding critical, especially for a permanent settlement.


20160929: 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.


20160921: Quantum Entanglement and the Great BohrEinstein Debate
 08:05: Polarization is just the alignment of a photon's electric and magnetic fields.


20160824: 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.


20160727: 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.


20160706: 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.


20160615: 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.


20160608: New Fundamental Particle Discovered?? + Challenge Winners!
 03:40: So, a higher energy vibration in the Higgs field.


20160518: Antigravity 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.


20160511: The Cosmic Conspiracy of Dark Energy Challenge Question
 02:16: ... the Einstein field equations and in the Friedmann equations that are derived from those, ...


20160504: Will Starshot's Insterstellar Journey Succeed?
 07:50: ... several other very prominent leaders in their scientific and technical fields. ...


20160420: 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 ...


20160413: 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.


20160406: 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.


20160323: 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.


20160316: 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.


20160302: 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.


20160203: 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 ...


20160127: 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 ...


20160113: 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 ...


20160106: 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 righthand 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.


20151216: 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, multicomponent field not only carries the weak hypercharge, but manages to take on all ...
 05:29: This makes the Higgs field an infinite source and sink of weak hypercharge.
 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 hypercharge 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 massgiving 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?


20151028: 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. ...


20151022: 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 ...


20151015: 5 REAL Possibilities for Interstellar Travel
 05:34: Channeled with magnetic fields, these pions provide our thrust.


20151007: 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 velocitydependent tradeoff between the electric and magnetic fields.
 04:55: But the fields are a mess.


20150923: 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.


20150805: 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 ...


20150617: 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 ...


20150603: 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 ...


20150527: Habitable Exoplanets Debunked!
 05:59: We have to narrow the field.


20150520: 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 ...


20150311: 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.
