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	2022-12-08: How Are Quasiparticles Different From Particles? 08:29: ... or perhaps quasi-positrons, and we have phonons, which are analogous to photons. ... 08:40: ... a nucleus and electrons bound to that nucleus by the exchange of virtual photons. ... 10:44: Normally we think of electrons as repelling each other via the electromagnetic force - mediated by photons. 12:47: But this means they act like photons in that many Cooper pairs can occupy the same quantum state. 14:20: After all, the elementary particles like electrons, photons, and quarks are just excitations in the elementary quantum fields.
	2022-11-23: How To See Black Holes By Catching Neutrinos 01:16: ... - so particles of matter rather than force-carrying bosons like the photons of regular astronomy, and neutrino's fermion type is lepton, so they're ...
	2022-11-09: What If Humanity Is Among The First Spacefaring Civilizations? 19:21: ... RNG could be correlated with the event that produced the photons, leading to the violation of the Bell inequality even if the photon never ...
	2022-10-26: Why Did Quantum Entanglement Win the Nobel Prize in Physics? 06:33: ... would then drop down again, with the lost  energy carried away by photons. ... 06:42: ... zero quantum spin, and which also resulted in  the creation of two photons. ... 06:54: ... in this transition, in order to conserve angular momentum the pair of photons needed to have a total spin of zero, which translates to them ... 07:18: Hidden variable theories, on the other hand,  allow the polarization to be set at the moment the photons are created. 07:25: By measuring these polarizations by passing both photons through polarizers, Clauser and Freedman could perform a Bell test. 08:22: Their orientation was already decided  when the entangled photons were produced. 08:27: So what if that orientation has some influence on the polarization direction of the photons at the moment of their creation? 08:35: ... the photons might carry hidden information about the eventual measurement ... 08:47: To close this loophole it would be necessary to somehow set the measurement direction after the photons were produced. 08:55: That sounds incredibly difficult, because in case you didn’t know photons move pretty fast. 09:54: ... means our entangled photons could be sent to different polarizers depending on an electrical ... 10:10: ... of this means that the photons can’t know how they’re going to be measured at the moment of their ... 06:54: ... in this transition, in order to conserve angular momentum the pair of photons needed to have a total spin of zero, which translates to them having ...
	2022-10-19: The Equation That Explains (Nearly) Everything! 06:57: ... the U(1) symmetry of electromagnetism, and the kinetic term for photons is made of the derivatives of the A field. In other words, this is like ... 07:51: ... need their kinetic energy in every possible direction. Except if two photons come close they'll just pass through each other, but if two say gluons ...
	2022-10-12: The REAL Possibility of Mapping Alien Planets! 06:05: ... momentum of the wind, solar sails catch the momentum of light - of photons from   the Sun. More traditional propulsion methods that ...
	2022-09-28: Why Is 1/137 One of the Greatest Unsolved Problems In Physics? 01:43: ... process results in the emission of photons  of specific energies that we observe as spectral lines - sharp peaks in ...
	2022-09-21: Science of the James Webb Telescope Explained! 04:20: Energetic ultraviolet photons reach us as infrared, stretched and worn out by the journey.
	2022-09-14: Could the Higgs Boson Lead Us to Dark Matter? 04:06: ... particles somewhere in space could annihilate to produce gamma ray photons, which could be picked up by telescopes like the Alpha Magnetic ... 06:19: ... also exclude photons, because not interacting with light is the first defining characteristic ...
	2022-08-24: What Makes The Strong Force Strong? 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. 11:32: That means photons can interact with objects without affecting their electric charge, and thus neutral objects can interact with magnetic fields. 11:40: ... that's where the similarities end, because gluons are not neutral like photons. ...
	2022-08-17: What If Dark Energy is a New Quantum Field? 09:05: Alternatively, it can be thought of as a fifth energetic component of the universe on top of baryons, dark matter, neutrinos, and photons.
	2022-08-03: What Happens Inside a Proton? 01:31: ... electrons and any other charged particle   via photons. We’re going to come back  to a full description of QCD very ... 05:31: ... virtual gluon   of the gluon field rather than virtual  photons of the electromagnetic field.   We can draw Feynman diagrams ... 03:12: ... Or it could happen via two electrons or more, or one of those photons   could spontaneously form an electron-positron pair before becoming ...
	2022-07-20: What If We Live in a Superdeterministic Universe? 00:26: Photons passing through two slits at once, electrons being spin up and down, cats being both alive and dead. 12:35: ... “random” color of individual photons of that light was used in place of a random number generator to decide ... 12:46: Now, this experiment used the polarization direction of photons rather than the spin direction of electrons, but it’s the same deal. 00:26: Photons passing through two slits at once, electrons being spin up and down, cats being both alive and dead.
	2022-06-01: What If Physics IS NOT Describing Reality? 16:52: ... matter is shrinking because there’s no  stretching of the traveling photons. And finally,   in a universe where galaxies shrink you’d ...
	2022-04-20: Does the Universe Create Itself? 06:24: ... then the combination of phase shifts in the beamsplitters causes the photons wavefunction to perfectly line up in detector 1 - constructive ... 07:08: ... principle, the second beamsplitter could be put in place only after the photons passed through the first. After they’d made their decision of a path to ... 06:24: ... then the combination of phase shifts in the beamsplitters causes the photons wavefunction to perfectly line up in detector 1 - constructive interference, and to ...
	2022-02-16: Is The Wave Function The Building Block of Reality? 11:50: ... measurement, the scientists in Trieste were able to measure single photons emitted from the germanium ... 12:20: After watching the crystal for two months, they had detected a grand total of 576 photons. 11:50: ... measurement, the scientists in Trieste were able to measure single photons emitted from the germanium ...
	2022-01-27: How Does Gravity Escape A Black Hole? 06:16: ... force is communicated between charged particles by transferring virtual photons - ephemeral excitations in the electromagnetic ... 07:10: Or more precisely, they exchange the sum of all possible virtual photons. 07:16: But those photons don’t follow a well defined path between the interacting particles. 06:16: ... force is communicated between charged particles by transferring virtual photons - ephemeral excitations in the electromagnetic ... 07:16: But those photons don’t follow a well defined path between the interacting particles.
	2021-12-10: 2021 End of Year AMA! 00:02: ... do is you sum over you add over all the possible ways that virtual photons could be exchanged between the real particles the electron and the ...
	2021-09-21: How Electron Spin Makes Matter Possible 01:13: ... particles are bosons, and they are the force carrying particles like photons with spin 1 or the Higgs particle with spin ... 01:44: ... you like. For example in a laser beam, there’s no limit to the number of photons you can add - all of them in the same quantum state. But not fermions - ... 05:59: ... through space. If you have two such wavefunctions overlapping - like two photons in a laser beam, a shift in one of them by half a wave cycle puts the ...
	2021-09-15: Neutron Stars: The Most Extreme Objects in the Universe 02:00: ... pairs are created out of the extreme  energy photons in the magnetic field.   That field then becomes a particle ...
	2021-07-21: How Magnetism Shapes The Universe 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.
	2021-07-13: Where Are The Worlds In Many Worlds? 06:37: ... through the detector, along wires, through computer circuitry, as photons from the screen, as action potentials down our optical nerves, and ...
	2021-07-07: Electrons DO NOT Spin 02:25: ... electrons. That came from looking  at the specific wavelengths of photons emitted when electrons jump between energy levels  in atoms. Peiter ...
	2021-06-16: Can Space Be Infinitely Divided? 04:30: ... photon’s momentum is the Planck  constant divided by its ... 06:02: ... to produce an observable   gravitational field. Even though photons are massless, if enclosed in a system a photon   creates ... 04:30: ... photon’s momentum is the Planck  constant divided by its wavelength.   So ... 06:02: ... - ultraviolet - X-ray -   gamma-ray - which also increases the photon’s energy and momentum. As we crank up the energy   even further we ... 01:16: ... Rather came in quanta - chunks of energy that we now call photons.   Planck’s discovery hinges on a single  number that appears in his ...
	2021-05-25: What If (Tiny) Black Holes Are Everywhere? 03:08: ... such black holes the Hawking radiation is just photons - electromagnetic waves with kilometers-long wavelengths, so really, ... 05:23: It jiggles in its little crystal lattice cage with very specific vibrational modes, producing photons of specific energies. 13:44: JG 46 wants to know how to build a divide to split photons to make them entangled. 14:09: In certain materials known as non-linear crystals, the incoming photon is absorbed and the energy is instantly emitted as two photons. 14:16: Those photons are entangled with each other because various properties are correlated - in particular phase, polarization, and momentum. 03:08: ... such black holes the Hawking radiation is just photons - electromagnetic waves with kilometers-long wavelengths, so really, ...
	2021-05-19: Breaking The Heisenberg Uncertainty Principle 07:03: By amplitude I meant the number of photons making up the beam. 08:35: The laser is sent through a special material called a non-linear crystal, which converts incoming photons into pairs of photons. 08:43: Those outgoing photons have entangled phases - the relative positions of their peaks and troughs are correlated. 09:26: ... for the improved phase precision with more uncertainty in the number of photons traveling in your laser ... 09:34: And that introduces its own type of noise - radiation pressure noise as these photons transfer energy to the mirrors in the interferometer. 07:03: By amplitude I meant the number of photons making up the beam. 09:34: And that introduces its own type of noise - radiation pressure noise as these photons transfer energy to the mirrors in the interferometer. 09:26: ... for the improved phase precision with more uncertainty in the number of photons traveling in your laser ...
	2021-04-07: Why the Muon g-2 Results Are So Exciting! 04:33: In this theory, electromagnetic interactions result from charge particles communicating by exchanging virtual photons. 04:47: For example, a pair of electrons could repel each other by exchanging one virtual photon, or two virtual photons, or three et cetera. 04:56: All those virtual photons could do something weird like momentarily becoming an electron-positron pair.
	2021-03-23: Zeno's Paradox & The Quantum Zeno Effect 09:21: ... quantum Zeno-like freezing you’d need to hit the atom with many, many photons - and that was certainly not a “subtle” ...
	2021-03-09: How Does Gravity Affect Light? 04:37: ... time dilation is so strong that clocks stop and the frequency of photons trying to escape is brought to ...
	2021-02-24: Does Time Cause Gravity? 05:50: On the other hand, light itself travels at the speed of light through space only, and not at all through time - a photon’s clock is frozen. 05:57: ... rotated out of the time direction into space - although technically photons and other massless particles don’t have a 4-velocity, which is defined ... 07:39: If photons are already fully rotated into the spatial direction, how is it that they’re also affected by gravitational fields? 05:50: On the other hand, light itself travels at the speed of light through space only, and not at all through time - a photon’s clock is frozen.
	2021-01-26: Is Dark Matter Made of Particles? 02:05: Any electrically charged particle experiences the electromagnetic force and can communicate with other charged particles by exchanging photons. 02:21: Neutrinos are unaffected by that force, and so they are quite literally invisible to photons.
	2021-01-19: Can We Break the Universe? 13:48: The energy levels are represented by a very small number of photons in a cavity - 0 to 5 - so quite quantum.
	2021-01-12: What Happens During a Quantum Jump? 01:22: ... that light is made up of irreducible packets of energy that we now call photons. ... 07:06: The individual photons emitted in this process couldn’t be seen - instead the single atom just glowed, or fluoresced.
	2020-11-04: Electroweak Theory and the Origin of the Fundamental Forces 08:16: The bosons of the version of SU(2) that I just described are simple light-speed oscillations in their fields, just like photons. 12:13: Back then, electromagnetism and photons and the weak force didn’t exist.
	2020-10-05: Venus May Have Life! 04:07: One possible biosignature in this range is phosphine, which absorbs photons of around 1.1mm wavelength.
	2020-09-08: The Truth About Beauty in Physics 14:58: In that case you'll see all of those photons produced when absorbed light is reemitted - emission lines.
	2020-09-01: How Do We Know What Stars Are Made Of? 03:06: ... amount of light we receive at different colors - or in other words, from photons of different energies of ... 03:44: Those are where photons of very specific energies have been plucked out of this thermal light. 04:39: But some photons encounter a new obstacle. 04:49: And if free electrons are good at stopping photons in their tracks, these atoms are even better. 05:07: So any photons trying to escape the Sun that happen to have one of these particular energies are going to get sucked up on its way out. 04:39: But some photons encounter a new obstacle.
	2020-07-28: What is a Theory of Everything: Livestream 00:00: ... you know um and the electro you can do this with light as well with photons and then what you see is that the electrons deposit themselves as ...
	2020-07-08: Does Antimatter Explain Why There's Something Rather Than Nothing? 00:22: ... canceling each other out completely, and leaving only two photons to carry away the energy. And it works in reverse too. Particle and ... 01:25: ... almost everything would have annihilated, leaving a universe full of photons and only very few particles that couldn’t find an annihilation partner. ...
	2020-06-30: Dissolving an Event Horizon 05:33: That radiation cian be any type of elementary particle - but in the case of the most massive black holes, it’s mostly just photons. 05:45: In very massive black holes the Hawking radiation has trouble mustering the energy for anything but weak photons. 14:40: ... the case of a universe full of photons - I THINK the idea is that when you rescale both space and time by the ... 15:14: ... mentioned that in conformal cyclic cosmology, photons and gravitational waves can pass the boundary from universe end to new ... 14:40: ... the case of a universe full of photons - I THINK the idea is that when you rescale both space and time by the ...
	2020-06-15: What Happens After the Universe Ends? 02:54: Let’s say these universes contain no matter - only photons - light. 03:39: For those photons, the beginning of their journey is the same as their end, and these universes are equivalent. 07:16: ... but it may be the case that we’re left with only a universe of photons, electrons and positrons, and neutrinos, as well as gravitons - the ... 07:27: The photons and gravitons are massless - you can’t build clocks with them. 14:02: It turns out that, as well as photons, gravitational waves should be able to pass between aeons. 02:54: Let’s say these universes contain no matter - only photons - light. 07:16: ... but it may be the case that we’re left with only a universe of photons, electrons and positrons, and neutrinos, as well as gravitons - the quantum ... 14:02: It turns out that, as well as photons, gravitational waves should be able to pass between aeons.
	2020-05-11: How Luminiferous Aether Led to Relativity 16:14: ... same size as the local bubble of galaxies. Those poor cosmic background photons should have reached us billions of years ago - it's not that they had ...
	2020-05-04: How We Know The Universe is Ancient 00:55: ... are no rocks from the beginning of the universe. There aren’t even any photons from the time right after the Big Bang. So today we go deeper into deep ...
	2020-04-28: Space Time Livestream: Ask Matt Anything 00:00: ... Lopez also asks if we can explain how what happens to the energy of photons that are redshifted okay and the restrict of gravitational waves what ...
	2020-03-31: What’s On The Other Side Of A Black Hole? 08:22: ... do you see? Light can reach you from the universe behind - those are photons that overtake you heading towards the central singularity. Light can ...
	2020-03-24: How Black Holes Spin Space Time 10:27: ... black hole with mirrors. Then you just shine a flashlight at it and its photons pass through the ergosphere again and again, becoming exponentially ...
	2020-03-03: Does Quantum Immortality Save Schrödinger's Cat? 14:38: Well these days double-slit experiments are usually done with single photons or other particles. 14:54: ... actually, most visible-light photons will travel the length of a typical double-slit experiment without ...
	2020-02-24: How Decoherence Splits The Quantum Multiverse 04:04: This time we'll use particles of light - photons as our quantum particle. 05:52: The key in this experiment is that all photons exit the slits with the same phase relationship. 08:27: ... that shift would then change for each subsequent photon - new photons land in unpredictable places - so in the end we would just see a blur ... 11:00: Perhaps instead we could use that electrical current to generate a new pair of photons, which could then interfere. 05:52: The key in this experiment is that all photons exit the slits with the same phase relationship. 08:27: ... that shift would then change for each subsequent photon - new photons land in unpredictable places - so in the end we would just see a blur ...
	2020-02-18: Does Consciousness Influence Quantum Mechanics? 00:36: The rules governing the tiny quantum world of atoms and photons seem alien. 04:17: ... that information travels via photons to light-sensitive molecules in our retinas, which initiate electrical ...
	2020-02-11: Are Axions Dark Matter? 07:53: ... they can still interact with the electromagnetic field and produce photons via the strong ... 08:05: ... do this by generating pairs of virtual quarks which then decay into photons - the so-called Primakoff effect. This would look like an axion turning ... 08:23: ... a strong magnetic field and then blocked by a metal wall. But some photons get converted to axions in the field, and so pass directly through the ... 08:58: ... fields of its own to try to turn those axions back into detectable photons. No luck yet, but the range of possible properties of axions is being ... 09:45: ... that some gamma rays get converted back and forth between axions and photons by the magnetic fields of entire galaxies. That makes them invisible for ... 12:47: ... are indistinguishable from each other - swapping two electrons or two photons doesn't change anything, so that number might be an over estimate. But ... 08:05: ... do this by generating pairs of virtual quarks which then decay into photons - the so-called Primakoff effect. This would look like an axion turning ... 12:47: ... are indistinguishable from each other - swapping two electrons or two photons doesn't change anything, so that number might be an over estimate. But at any ...
	2020-01-06: How To Detect a Neutrino 07:38: ... have perfectly annihilated each other ♪ ♪ leaving a universe of only photons. ...
	2019-10-07: Black Hole Harmonics 09:53: ... doesn’t matter what fell in to make the black hole – atoms, photons, dark matter, monkeys – all that information should be lost, leaving only ...
	2019-08-19: What Happened Before the Big Bang? 12:02: That energy would then end up in the cosmic background radiation photons, but not for a while.
	2019-07-15: The Quantum Internet 03:19: We can already send photons of light very long distances using lasers or fiber optics - and those photons are pretty quantum. 03:27: The problem is that to transmit quantum information we have to pay attention to individual photons - quanta of light. 03:34: ... classical information using light, each bit is encoded with many photons, and many can be lost or altered en route without compromising the ... 03:44: If too many photons are lost you can just run the channel through a repeater, which reads the signal and boosts it with extra photons. 03:52: It’s much harder to transmit single photons in a way that perfectly maintains their quantum state. 03:59: And it’s fundamentally impossible to boost that signal by duplicating those photons. 06:50: Qubits A and B could be the polarization states of two photons. 10:14: These are great because they’re much, much faster than repeaters that have to transfer quantum states between photons and matter particles. 10:22: So the current state of the art is that entangled quantum states have been transmitted with photons using fibre optics and lasers. 10:29: Some researchers have even succeeded in bouncing entangled photons off a satellite. 10:34: ... photons can then transfer their entangled states into a variety of matter ... 03:27: The problem is that to transmit quantum information we have to pay attention to individual photons - quanta of light.
	2019-06-06: The Alchemy of Neutron Star Collisions 12:15: ... when electrons were free of their atoms and so could block the paths of photons then it was transparent during the dark ages because electrons bound in ... 13:02: ... was 100^3 times lower than at recombination and so the mean free path of photons was a million times larger in a related question, LobbySeatWarmer asks, ...
	2019-05-16: The Cosmic Dark Ages 05:13: ... in the hydrogen atom was in danger of being absorbed. Two specific photons were in particular danger: in one case that absorption signaled the end ... 08:36: ... – a quasar shines out from the epoch of reionization. Lyman-alpha photons from that quasar can travel a short distance because the quasar has ... 09:21: ... towards us, but the universe keeps expanding. Wavelength by wavelength, photons get absorbed as they are shifted into the danger zone of Lyman-alpha ... 10:47: ... end of the trough is where reionization ended, so that photons to the left of it could potentially reach us. The jagged region is the ... 12:02: ... extremely sensitive radio telescope to catch more of those elusive 21cm photons. ...
	2019-05-09: Why Quantum Computing Requires Quantum Cryptography 07:43: ... a random string of bits, 0’s and 1’s and encodes these bits using photons polarized in a particular basis, and uses a randomly chosen basis, ... 08:22: Over that same public channel they randomly pick a subset of those bits and Albert reveals which basis was used for those photons, and what she sent. 09:06: That’s because Werner, like Niels, can only pick a random basis each time on which to project the photons. 10:06: But the chance is 1 in 2 to the power of the number of photons, which quickly gets close enough to impossible given that Werner only gets one shot. 11:04: ... between the two – for example, electrons with opposite spin axes or photons with 90-degree ... 07:43: ... a random string of bits, 0’s and 1’s and encodes these bits using photons polarized in a particular basis, and uses a randomly chosen basis, either ...
	2019-03-20: Is Dark Energy Getting Stronger? 07:58: ... works like this: when photons of ultraviolet light radiate from the accretion disk, they bump into ...
	2019-02-20: Secrets of the Cosmic Microwave Background 11:14: ... of years the Universe was in the radiation-dominated epoch Basically photons produced more gravity than matter Fluctuations that were small enough to ...
	2019-02-07: Sound Waves from the Beginning of Time 02:01: There's also light, in fact, around a billion photons for every electron. 02:26: We say that in this state, light was coupled with matter, And baryons and photons formed a single strange fluid: A Baryon-Photon plasma. 03:08: ... interaction between the charged particles of the plasma via the trapped photons meant that ripples in the plasma travelled at over half the speed of ... 03:16: Mixed in this soup of baryons and photons was dark matter. 03:38: Okay, so, the universe is filled with this hot ocean of baryons, photons, and dark matter. 04:24: But also at that density peak, the imprisoned photons exerted an enormous outward pressure. 04:52: ... matter became more diffused, and the photons themselves were stretched, redshifted to ower energies, themselves were ... 05:49: As the wave of plasma and photons decoupled, light began to stream freely through the universe as the cosmic background radiation. 04:24: But also at that density peak, the imprisoned photons exerted an enormous outward pressure. 02:26: We say that in this state, light was coupled with matter, And baryons and photons formed a single strange fluid: A Baryon-Photon plasma. 03:08: ... interaction between the charged particles of the plasma via the trapped photons meant that ripples in the plasma travelled at over half the speed of ...
	2018-12-12: Quantum Physics in a Mirror Universe 00:02: ... weak interaction into nickel by emitting an electron and some gamma ray photons and neutrinos the cobalt-60 nucleus also happens to have an unusually ...
	2018-11-14: Supersymmetric Particle Found? 04:50: When ultra high energy cosmic rays travel through space, they bump into the photons of the cosmic microwave background.
	2018-11-07: Why String Theory is Right 14:26: Uri Nation asks about the photons that mediate the magnetic field or the contact force between two bodies.
	2018-10-31: Are Virtual Particles A New Layer of Reality? 06:12: How can throwing photons between particles cause them to be drawn together? 06:32: Bizarrely, that includes photons that are pointing in the wrong direction to even make the journey. 06:45: And you also count photons emitted by the positron but pointing away from the electron. 06:50: These are the virtual photons that ultimately provide the attractive force. 08:22: In fact, you only see that force in the sum of all possible virtual photons over all possible Feynman diagrams. 12:18: ... in the case of Max Planck discovery of the quantum nature of photons, it turned out that a mathematical artifact represented new real ... 06:45: And you also count photons emitted by the positron but pointing away from the electron.
	2018-10-10: Computing a Universe Simulation 05:55: ... you want to include photons, neutrinos, dark matter, et cetera, and not just atoms, you need to scale ...
	2018-09-12: How Much Information is in the Universe? 06:17: Neutrinos and photons formed in the big bang are probably a billion times more abundant than protons. 06:24: That's verified experimentally in the case of photons. 06:27: The cosmic microwave background has around 10 to the power of 89 photons across the observable universe. 06:34: So almost all of the information, and for that matter, the entropy in particles is in neutrinos and in the cosmic microwave background photons. 06:17: Neutrinos and photons formed in the big bang are probably a billion times more abundant than protons.
	2018-08-23: How Will the Universe End? 06:18: But there are several beyond the standard-model mechanisms that would allow them to decay into positrons, neutrinos, and gamma ray photons. 06:58: The universe will contain only photons, electrons, and black holes.
	2018-08-15: Quantum Theory's Most Incredible Prediction 07:22: So one way to think about this quantum buzz is with virtual photons. 07:36: In the case of electromagnetism, those interactions are mediated by virtual photons, which are just a mathematical way to describe quantum buzz. 07:45: Every interaction with virtual photons that can happen, does, at least in a sense. 08:17: They represent the possible interactions of the quantum field by way of virtual photons.
	2018-06-20: The Black Hole Information Paradox 03:44: The black hole radiates particles, mostly photons, that contain no information. 13:41: ... electric charge given that the electromagnetic field is communicated by photons and photons can't escape the black ... 14:01: But quantum-field theory imagines the electromagnetic force as being transmitted by virtual photons. 14:07: Now it's important to note the distinction between virtual photons and real photons.
	2018-06-13: What Survives Inside A Black Hole? 02:28: ... could have formed from a collapsed star or entirely out of antimatter or photons or monkeys, but the only thing we can know about the material that went ... 12:47: It's encoded in the energy, phase, polarization, et cetera of the two gamma-ray photons that are created.
	2018-05-23: Why Quantum Information is Never Destroyed 12:05: The energy density of photons is much, much lower than the energy density of dark energy. 12:17: Radiation, including photons and neutrinos, dominated the energy density until around 50,000 years after the Big Bang.
	2018-05-16: Noether's Theorem and The Symmetries of Reality 01:27: Where does the energy from red-shifted photons go?
	2018-05-02: The Star at the End of Time 03:09: The layer above the Sun's core is what we call "radiative." All of the energy travels in the form of photons bouncing their way upwards. 05:03: First, the hotter something is, the more thermal photons it produces. 05:08: So increasing the surface temperature allows a red dwarf to shed all of those excess photons produced by its rising fusion rate. 05:17: And rule two, the hotter something is, the more energetic its individual thermal photons. 05:23: The black-body spectrum of a hot object emits relatively more photons at short energetic wavelengths than a cooler object. 03:09: The layer above the Sun's core is what we call "radiative." All of the energy travels in the form of photons bouncing their way upwards. 05:08: So increasing the surface temperature allows a red dwarf to shed all of those excess photons produced by its rising fusion rate.
	2018-04-11: The Physics of Life (ft. It's Okay to be Smart & PBS Eons!) 08:01: The most random possible form for energy is thermal radiation, and the lower the energy of its component photons, the higher the entropy. 12:44: But the accelerating expansion of the universe will prevent any photons emitted today from galaxies at that distance or beyond from ever reaching us.
	2018-04-04: The Unruh Effect 02:38: ... because photons fired from anywhere in the past light cone can reach our observer either ... 02:59: If you wait long enough, photons from anywhere in the universe can catch up to you. 02:38: ... because photons fired from anywhere in the past light cone can reach our observer either at ...
	2018-03-21: Scientists Have Detected the First Stars 02:31: That change in equilibrium meant the gas was suddenly absorbing more 21 centimeter photons, than it was emitting. 02:38: ... gas and eventually, became too hot to emit, or absorb, 21 centimeter of photons at ... 02:51: [MUSIC PLAYING] The TLDR is that there should have been this brief period of time when the universe was eating up 21 centimeter photons from the CMB. 04:44: Colder gas is better at absorbing 21 centimeter photons.
	2018-03-15: Hawking Radiation 09:39: By the way, Hawking radiation is mostly going to be photons and other massless particles.
	2018-01-24: The End of the Habitable Zone 11:06: Are they photons or what? 11:41: Of course, you would always see photons because photons are massless. 11:45: Those photons would have a perfect black body spectrum.
	2018-01-17: Horizon Radiation 03:08: Imagine I fire a pair of photons, which annihilate to produce an electron, positron pair. 03:14: ... a black hole, should agree on the basic result of that interaction-- two photons in, one electron, one positron ... 08:28: ... old ones, for example, to describe a particle interaction like those two photons annihilating into an electron, positron ...
	2018-01-10: What Do Stars Sound Like? 12:48: Those particles can then fire photons in our direction in a couple of different possible ways. 12:56: The charged particles spiral around the axial magnetic fields and emit photons as they do. 13:05: ... in the jet bump into existing photons, perhaps synchrotron photons, and scatter them to higher energies, and ... 13:14: In both cases, photons are emitted in different directions.
	2017-12-13: The Origin of 'Oumuamua, Our First Interstellar Visitor 10:30: How can a photon's frequency be generalized as momentum? 10:47: But photons have constant speed and no mass. 10:56: That last fact explains the increasing spread in the direction of photons after they pass through a narrowing slit. 10:30: How can a photon's frequency be generalized as momentum?
	2017-12-06: Understanding the Uncertainty Principle with Quantum Fourier Series 06:49: In the early days of quantum mechanics, it was realized that photons are electromagnetic wave packets whose momentum is given by their frequency.
	2017-11-29: Citizen Science + Zero-Point Challenge Answer 06:57: ... the vacuum energy density comes from assuming that there are no virtual photons above a certain cut of ... 08:42: ... Photons with wavelengths shorter than 0.1 millimeters definitely exist, and we ... 09:06: That proves the existence of virtual photons with wavelengths smaller than the plate separation.
	2017-11-08: Zero-Point Energy Demystified 06:41: ... cavity, then they're giving it up again to real particles, probably photons, on the ...
	2017-11-02: The Vacuum Catastrophe 02:55: What if there's a maximum possible frequency for virtual photons? 03:24: Until we develop a theory of quantum gravity, we can't say whether the photons above this energy are possible. 03:31: ... if we add up the vacuum energy, including virtual photons, all the way up to the Planck energy, we get a finite number-- a very, ... 06:32: ... basic supersymmetry only allows us to cancel out photons down to the so-called electroweak energy, which brings the predicted ...
	2017-10-25: The Missing Mass Mystery 04:14: See, before the photons of the cosmic background radiation were released, they were trapped in the searing hot plasma of baryonic matter. 04:23: The interplay between baryonic and photons resulted in density oscillations. 08:32: As photons from the CMB pass through a giant filament, the hot plasma in the filament grants it a little energy boost. 08:41: In fact, the electrons in that plasma scatter CMB photons to higher energies.
	2017-10-19: The Nature of Nothing 02:15: ... energies, and those oscillations are the electrons, quarks, neutrinos, photons, gluons, et cetera, that comprise the stuff of our ... 04:33: For example, QFT describes the electromagnetic force as the exchange of virtual photons between charged particles. 05:55: And so virtual photons can exist for any amount of time, long enough to carry the electromagnetic force to any distance. 08:43: He imagined two conducting plates, brought so close together that only certain virtual photons could exist between the plates. 13:32: ... so electrons and quarks, while the force-carrying particles like photons, gluons, et cetera, are spin-1 ... 02:15: ... energies, and those oscillations are the electrons, quarks, neutrinos, photons, gluons, et cetera, that comprise the stuff of our ... 13:32: ... so electrons and quarks, while the force-carrying particles like photons, gluons, et cetera, are spin-1 ...
	2017-09-28: Are the Fundamental Constants Changing? 04:41: When electrons move between levels, they emit or absorb photons with energies equal to that lost or gained by the electron. 06:48: When a quasar's light passes through giant clouds of gas on its way to us, elements in those clouds absorb photons to produce spectral lines. 08:26: ... challenge here is that the measurement is really, really difficult. Photons from these extremely distant quasars and gas clouds are massively ...
	2017-08-16: Extraterrestrial Superstorms 13:17: There should be diagrams with photons connecting across the vertices of the two-vertex photon deflection diagram, like this.
	2017-08-10: The One-Electron Universe 02:50: The direction of an electron's worldline can shift as the electron is scattered by photons.
	2017-08-02: Dark Flow 03:55: As the photons of the CMB pass through that plasma, they steal a little bit of its energy. 04:24: ... Hubble flow, then the SZ effect adds an extra Doppler shift to the CMB photons that pass through that ... 10:35: For example, in order to conserve momentum, an annihilating electron and positron must produce two photons, not one.
	2017-07-26: The Secrets of Feynman Diagrams 02:12: That means interactions between electrons; their anti-matter counterparts, the positron; and photons. 07:13: Simple examples are the exchange of a single photon to transfer momentum between electrons, or the exchange of two or more photons. 07:21: ... as many of these vertices as we like, including the electrons exchanging photons with themselves at different stages in the process, or photons ...
	2017-07-12: Solving the Impossible in Quantum Field Theory 02:13: Vibrations in the EM field are called photons, what we experience as light. 05:39: Or any of those photons might do something crazy, like momentarily split into a virtual anti-particle-particle pair. 07:43: ... include exchanging two virtual photons, or one electron emitting and reabsorbing a virtual photon, or the ... 08:41: Electrons are constantly interacting with virtual photons. 09:21: In reality, something must limit the maximum energy of these photons.
	2017-07-07: Feynman's Infinite Quantum Paths 10:10: ... of the photon, but it also includes the probability amplitude of a photon's energy moving from the electromagnetic field into, say, the electron ... 14:16: Up to around a millionth of a second after the Big Bang, the universe was hot enough for photons to be continuously forming matter-antimatter pairs. 10:10: ... of the photon, but it also includes the probability amplitude of a photon's energy moving from the electromagnetic field into, say, the electron field, ...
	2017-06-28: The First Quantum Field Theory 06:08: If you take a pair of electrons or photons in two quantum states and make them swap places, then nothing changes. 07:06: Paul Dirac's solution was to not try to track the changing states of individual photons. 07:31: ... a number of minimum amplitude quantum oscillations, which is to say, photons. ... 08:00: ... the math doesn't even try to keep track of the movement of individual photons-- only the shifting number in each quantum ... 09:10: An electron and a positron can annihilate each other and create two photons. 10:48: Remember, this approach began with thinking of photons as oscillations in the electromagnetic field. 11:28: ... pair, for every type of force-carrying particle-- so-called bosons, like photons and gluons-- and of course for the famous Higgs boson, which is just an ...
	2017-06-07: Supervoids vs Colliding Universes! 05:25: So if there are giant voids in the direction of the cold spot, then these could have sapped energy from the CMB photons as they passed through.
	2017-05-31: The Fate of the First Stars 06:29: Those electrons then lose that energy by emitting light at specific wavelengths-- signature photons that are different for every element or molecule. 06:39: Those photons quickly escape the cloud, taking energy with them, and helping to cool things down.
	2017-04-19: The Oh My God Particle 06:58: Empty space isn't really empty, it's full of low-energy microwave photons leftover from the heat glow of the very earliest of times. 07:11: ... volts, about 8 joules, can't travel far before smacking into these photons and giving up some of their ... 06:58: Empty space isn't really empty, it's full of low-energy microwave photons leftover from the heat glow of the very earliest of times.
	2017-03-29: How Time Becomes Space Inside a Black Hole 07:45: We also begin to encounter a new set of photons from the past.
	2017-03-22: Superluminal Time Travel + Time Warp Challenge Answer 07:06: Well, you just trace the photon paths, assuming for a moment that an FTL ship doesn't produce infinitely red or blue shifted photons. 07:14: The Paradox outraces its own photons as it catches up to the Annihilator, and then it continues to emit light backwards behind it after it passes. 07:24: So the Annihilator sees a series of photons coming from both directions that arrive simultaneously. 08:30: To do that, we first need to outrace photons that were admitted at the space time point that we want to perceive. 07:24: So the Annihilator sees a series of photons coming from both directions that arrive simultaneously.
	2017-01-25: Why Quasars are so Awesome 03:05: For one thing, its spectrum was redshifted, the wavelength of its light stretched out as those photons traveled through the expanding universe.
	2017-01-11: The EM Drive: Fact or Fantasy? 03:01: ... those photons actually escape the cavity, then any momentum exchange between the ... 03:12: And if photons do escape, then you've just built a photon thruster. 07:36: Photons would need to give up their energy, producing particle anti-particle pairs.
	2016-12-21: Have They Seen Us? 08:06: To spot these radio photons, we need a truly gigantic interferometer, both for extreme sensitivity and to eliminate our own radio buzz. 14:32: So a distant immortal observer, with a ridiculously good telescope, will detect photons from the falling monkey at all future times. 14:42: Eventually, those photons will come billions, even trillions, of years apart from each other and be hugely redshifted.
	2016-10-26: The Many Worlds of the Quantum Multiverse 01:09: But to summarize, a stream of photons or electrons, or even molecules, travels from some point to a detector screen via pair of slits. 06:50: For example, many histories lead to photons landing on the bright bands of the interference pattern, and very few to the dark bands.
	2016-09-21: Quantum Entanglement and the Great Bohr-Einstein Debate 08:05: Polarization is just the alignment of a photon's electric and magnetic fields. 08:25: The experiment was even set up so that the influence had to travel between the photons at faster than the speed of light. 08:05: Polarization is just the alignment of a photon's electric and magnetic fields.
	2016-09-07: Is There a Fifth Fundamental Force? + Quantum Eraser Answer 00:45: And when they settle down again, they give off that energy as photons, but also sometimes as a particle or a particle-antiparticle pair. 01:19: The same sort of excess in the photons emitted after proton collisions in the Large Hadron Collider led to the discovery of the Higgs boson. 04:14: ... seem to be influenced by a decision that is made regarding each of those photon's entangled partners in the ... 05:06: In fact, the distribution of photons at the screen always looks like a single blurred distribution. 05:15: It's only when you flag which photons had twins arriving at detectors A, B, C, or D that you see patterns arise. 05:23: In fact, even if you remove all of the A and B photons, you still don't see an interference pattern until you distinguish C versus D. 05:33: And this is because those photons have interference bands that are exactly out of phase. 05:55: Those embedded patterns are set by the eventual destination of the entangled partners of those photons. 06:09: Yet, we can't extract the patterns of the photons that landed at the screen until we get the information of which detectors their entangled twins hit. 07:41: And so it's way less out there than photons somehow knowing that in the future some conscious mind will know its path. 01:19: The same sort of excess in the photons emitted after proton collisions in the Large Hadron Collider led to the discovery of the Higgs boson. 04:14: ... seem to be influenced by a decision that is made regarding each of those photon's entangled partners in the ...
	2016-08-24: Should We Build a Dyson Sphere? 11:57: ... you need to know which detector was triggered by every one of those photon's entangled ... 12:11: ... the screen and a hit at one of the detectors, that means that those two photons were an entangled ... 12:21: ... the experiment is done, we can pick out off the screen all of the photons that had twins hitting, say, detector A. Those photons turn out to show ... 12:33: But the photons associated with C or D do have an interference pattern. 12:38: ... there is no way to figure out which photons correspond to which detectors until the arrival times at the screen are ... 13:24: ... at detectors A, B, C, and D. Well, the screen just looks like a blur of photons. ... 13:37: You see, it's not just that the blur of photons connected to detectors A and B are overlaid with an interference pattern from C and D, no. 14:06: It adds up to a flat distribution, and it's only when you look at the photons connected to C and D separately that you see the bands. 13:37: You see, it's not just that the blur of photons connected to detectors A and B are overlaid with an interference pattern from C and D, no. 14:06: It adds up to a flat distribution, and it's only when you look at the photons connected to C and D separately that you see the bands. 12:38: ... there is no way to figure out which photons correspond to which detectors until the arrival times at the screen are compared to ... 11:57: ... you need to know which detector was triggered by every one of those photon's entangled ... 12:21: ... screen all of the photons that had twins hitting, say, detector A. Those photons turn out to show no interference ...
	2016-08-17: Quantum Eraser Lottery Challenge 00:45: Photons are fired one at a time through the two slits. 00:49: On the opposite side, each photon is split into an entangled pair of photons. 01:31: And the result is the photons whose entangled twins land at A produce no interference pattern. 02:05: But you see the clear patterns when you separate those C and D photons. 02:25: ... those photons land according to an interference distribution, or a single pile ... 03:11: ... it was executed, photons can travel to the "which way" section-- so detectors A and B-- or to the ... 03:34: With the mirrors in place, photons are reflected to the which way detectors, and no interference pattern is formed. 03:44: Photons travel through to the eraser section, resulting in an interference pattern at the screen. 04:17: Before the photons get to the which way end, we freeze them for a day. 04:25: Actually, you can't really freeze photons. 04:35: Photons start hitting the screen, building up some pattern. 02:25: ... those photons land according to an interference distribution, or a single pile ... 04:35: Photons start hitting the screen, building up some pattern. 03:44: Photons travel through to the eraser section, resulting in an interference pattern at the screen.
	2016-08-10: How the Quantum Eraser Rewrites the Past 04:32: ... type of crystal that absorbs an incoming photon, and creates two new photons, each with half the energy of the ... 04:43: These new photons are twins of each other. 04:54: Place this crystal in front of the double slit to make coherent entangled pairs of any photons passing through. 05:21: If we run this for a bunch of photons, we see that whenever detectors A or B light up, we get a simple pile of photons here at the screen. 05:41: And crazier, this experiment was set up so that photons reach A or B after their twins reach the screen. 06:32: Its job is to destroy any information about the path of the photons. 06:42: They work by allowing 50% of the photons through, while reflecting the other 50%. 06:50: Instead of being reflected to detectors A or B, half of the photons end up in detectors C or D. 07:06: If we only look at the photons whose twins end up at detector C or D, we do see an interference pattern. 04:54: Place this crystal in front of the double slit to make coherent entangled pairs of any photons passing through. 05:41: And crazier, this experiment was set up so that photons reach A or B after their twins reach the screen.
	2016-07-27: The Quantum Experiment that Broke Reality 02:13: ... comes in indivisible little bundles of electromagnetic energy called "photons." Einstein demonstrated this through the photoelectric effect but his clue ... 02:53: That shouldn't be a problem as long as you have at least two photons. 02:58: One photon passes through each slit and then the two photons interact with each other on the other side and produce our interference pattern. 03:11: The interference pattern is seen even if you fire those photons one at a time. 03:25: ... second, third, and fourth photons, also-- they deliver their energy at a single spot and so they appear to ... 03:37: If you keep firing those single photons, you start to see our interference pattern emerge once again. 03:56: This pattern has nothing to do with how each photon's energy gets spread out, as was the case with the water wave. 04:07: No, the pattern emerges in the distribution of final positions of many completely unrelated photons. 04:16: ... photon has no idea where previous photons landed or where future photons will land yet each photon reaches the ... 02:13: ... comes in indivisible little bundles of electromagnetic energy called "photons." Einstein demonstrated this through the photoelectric effect but his clue came ... 03:56: This pattern has nothing to do with how each photon's energy gets spread out, as was the case with the water wave. 02:58: One photon passes through each slit and then the two photons interact with each other on the other side and produce our interference pattern. 04:16: ... photon has no idea where previous photons landed or where future photons will land yet each photon reaches the screen ...
	2016-06-22: Planck's Constant and The Origin of Quantum Mechanics 03:30: And so the average frequency of the resulting particles of light, of photons, increases with temperature. 03:42: The sun is yellow because its 6000 Kelvin surface produces more photons in the green yellow part of the electromagnetic spectrum than anywhere else. 04:04: Your temperature is around 310 Kelvin, so your heat glow is mostly in low frequency infrared photons. 05:28: This simple idea allowed our good Englishmen to figure out the frequencies of the photons produced by all of this thermal motion. 03:30: And so the average frequency of the resulting particles of light, of photons, increases with temperature. 05:28: This simple idea allowed our good Englishmen to figure out the frequencies of the photons produced by all of this thermal motion.
	2016-06-15: The Strange Universe of Gravitational Lensing 00:39: We just catch photons with our eyes and trace their paths backwards. 08:29: This is a region where light paths are so strongly curved that photons can actually orbit the black hole, forming a shell of light. 08:41: So photons will inevitably spiral inwards or outwards.
	2016-06-01: Is Quantum Tunneling Faster than Light? 06:00: We want to send individual photons instead of lasers. 06:39: ... those rare tunneling photons really do travel instantaneously through the width of the barrier, then ... 08:07: So scale up from photons to people and we have transporter beams, right?
	2016-05-25: Is an Ice Age Coming? 12:46: ... have wondered whether the energy lost in the cosmological redshift of photons could account for the energy gained by dark ... 13:09: But photons also get spread out and they get red shifted, so they do lose energy inversely proportional to the increasing scale factor. 13:28: ... Photons make up only a tiny energetic contribution to the modern universe-- far ... 13:42: These days, photons just don't have enough energy left to contribute.
	2016-04-27: What Does Dark Energy Really Do? 02:26: Redshift is the amount the universe expanded during a photon's journey, and distance is the amount of physical space it travelled through.
	2016-03-30: Pulsar Starquakes Make Fast Radio Bursts? + Challenge Winners! 02:28: How far did the cosmic microwave background photons that we see now have to travel in order to reach us? 03:27: You see, free electrons are really, really good at getting in the way of photons. 03:33: ... that even though the electrons themselves are infinitesimally small, photons don't have to get too close before they interact via the electromagnetic ... 03:54: Photons passing inside the circle interact and are scattered. 06:52: There's a distance forward, at which the photon's view ahead is completely blocked. 07:24: ... area and we have the number of these 1-meter segments before all the photon's possible paths forward are ... 07:44: Some photons travel further, some not so far. 03:33: ... that even though the electrons themselves are infinitesimally small, photons don't have to get too close before they interact via the electromagnetic ... 03:54: Photons passing inside the circle interact and are scattered. 07:44: Some photons travel further, some not so far. 06:52: There's a distance forward, at which the photon's view ahead is completely blocked.
	2016-03-09: Cosmic Microwave Background Challenge 00:23: ... photons of the cosmic background radiation were released when the universe was ... 01:12: Today, I have two questions for you about how far those CMB photons actually traveled. 02:53: That plasma was effectively opaque because photons couldn't travel far without bouncing off all those free electrons.
	2016-02-17: Planet X Discovered?? + Challenge Winners! 05:14: ... way of saying that the approaching clock sort of chases after its own photons, condensing the distance between the light signals that carry those ... 05:25: ... the receding clock is backing away from the photons traveling in your direction, stretching out the distance, and hence the ... 05:14: ... way of saying that the approaching clock sort of chases after its own photons, condensing the distance between the light signals that carry those ... 05:25: ... the receding clock is backing away from the photons traveling in your direction, stretching out the distance, and hence the time, ...
	2016-01-27: The Origin of Matter and Time 03:59: However, the internal photon still has to travel those 45 degree light like paths, because photons can only travel at the speed of light. 04:20: Regardless of the speed of that clock, the internal photons always do those 45 degree paths back and forth.
	2016-01-13: When Time Breaks Down 08:18: In that case, the box's mass increases by the amount equal to the energy of the contained photons, divided by the speed of light squared.
	2016-01-06: The True Nature of Matter and Mass 01:45: Now fill it with photons, also massless, that bounce around inside the box in all directions. 02:01: Now the back wall of the box moves into the incoming photons. 02:08: In the meantime, the front of the box, moving away from the incoming photons, feels less pressure. 02:20: The photons exert a force on the box, the box also exerts a force on the photons-- Newton's Third Law, which gives us the conservation of momentum. 02:29: Momentum lost by the box is transferred to the photons. 02:33: Now, if the box stops accelerating, then everything jiggles around and momentum gets shared out evenly between the box and the photons again. 02:54: The photon box is massive, even though none of its components-- not the photons, not the walls-- have any mass. 03:10: It's the energy of the photons divided by the square of the speed of those photons. 03:14: And you can derive the famous E equals Mc squared just by looking at how momentum transfers between the photons in the box under acceleration. 03:23: But E equals Mc squared describes the universal relationship between mass and confined energy, not just confined photons. 04:16: ... seemingly very different physical effects-- the box of photons and the compressed spring-- both give the same translation between mass ... 04:36: Photons in the photon box, but even in the spring, the density wave is ultimately communicated by electromagnetic interactions between the atoms. 07:31: Individual photons affect space-time. 08:05: The individual photons don't have it when they travel from one side of the box to the other. 08:13: Does the ensemble of photons somehow feel time that individual photons do not? 07:31: Individual photons affect space-time. 03:10: It's the energy of the photons divided by the square of the speed of those photons. 08:05: The individual photons don't have it when they travel from one side of the box to the other. 02:20: The photons exert a force on the box, the box also exerts a force on the photons-- Newton's Third Law, which gives us the conservation of momentum. 02:08: In the meantime, the front of the box, moving away from the incoming photons, feels less pressure. 02:20: The photons exert a force on the box, the box also exerts a force on the photons-- Newton's Third Law, which gives us the conservation of momentum.
	2015-11-05: Why Haven't We Found Alien Life? 11:14: ... the bubble, you'd see nothing unless it stopped, in which case all the photons and particles that are captured on its journey would blast you into ...
	2015-10-07: The Speed of Light is NOT About Light 00:14: ... does the universe seem to conspire to, one, keep photons from traveling at any speed but 300,000 kilometers per second in a ... 08:57: So lights or photons, also gravitational waves and gluons all have no mass.
	2015-09-23: Does Dark Matter BREAK Physics? 08:30: ... anyway, the photons from the future universe will never catch up to the monkey because that ... 10:13: And with that radiation comes all of the remaining photons that the monkey emitted before crossing the horizon.
	2015-08-19: Do Events Inside Black Holes Happen? 07:54: Remember, from our point of view, there are no photons inside.
	2015-08-05: What Physics Teachers Get Wrong About Tides! 10:09: ... as being mediated by some kind of particle like electromagnetism by the photons, strong nuclear forces by the gluon, and so ...
	2015-07-29: General Relativity & Curved Spacetime Explained! 05:44: On a flat spacetime diagram the world lines of those photons should be parallel and congruent. 05:49: ... light, that would be true even if it turned out that gravity slowed photons down and bent their world lines, since both photons would be affected ... 06:09: But if you actually do this experiment you find the photons arrive on the roof slightly more than five seconds apart.
	2015-07-15: Can You Trust Your Eyes in Spacetime? 04:18: ... would have to be moving faster than light, which normal objects and photons cannot ...
	2015-05-27: Habitable Exoplanets Debunked! 09:04: Natalia B, Pablo Herrero, and Gorro Rojo all asked whether photons actually have mass if they have energy. 09:24: Gareth Dean asked, if all the photons in the universe have been red shifting as the universe expands, that means they're losing energy. 10:17: ... total amount of effective mass you'd have from putting some number of photons in a mirrored box, more or ...
	2015-04-01: Is the Moon in Majora’s Mask a Black Hole? 08:49: With each passing moment of time, any observer sitting anywhere will see photons that were emitted from progressively more distant locations.

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