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	2022-11-16: Are there Undiscovered Elements Beyond The Periodic Table? 11:08: ... doing this using computational techniques like density functional theory, which we explained in a previous ...
	2022-11-09: What If Humanity Is Among The First Spacefaring Civilizations? 18:50: ... implied by this interpretation is equivalent to standard quantum field theory, with the time-reversed signals corresponding to negative frequency ...
	2022-10-26: Why Did Quantum Entanglement Win the Nobel Prize in Physics? 00:47: ... at a distance” as Einstein called it, is in seeming violation of his own theory of relativity, which tells us that no causal influence can travel faster ... 03:36: ... hidden information, and they’re collectively known as hidden variable theories. ... 04:10: It became dogma, and for a while it was career suicide to question the orthodoxy, for example by researching hidden variable theories. 04:21: David Bohm got the worst of that with his pilot wave theory, which we talk about in another video. 04:38: ... that information, or even testing a specific hidden variables theory. ... 07:18: Hidden variable theories, on the other hand,  allow the polarization to be set at the moment the photons are created. 10:22: The Bell inequalities were also violated in Alain Aspect’s experiment, dealing another blow to hidden variable theories. 13:53: Because science only moves forward when we try to push its theories to the breaking point. 18:42: ... could be eliminated with  a more elegant formulation of the theory. ... 19:16: ... in general a lot of problematic features appear in quantum field theory that have to be removed by hand - for example, various  infinities ...
	2022-10-19: The Equation That Explains (Nearly) Everything! 00:00: ... Standard Model of particle physics is arguably the most successful theory in the history of physics. It predicts the results of experiments with a ...
	2022-10-12: The REAL Possibility of Mapping Alien Planets! 04:12: ... first let’s review gravitational  lensing. Einstein’s general theory of relativity   tells us that gravity is due to curvature in ...
	2022-09-21: Science of the James Webb Telescope Explained! 13:29: Robin Saunders reminds us that there’s a relationship between gluon flux tubes and string theory. 13:37: ... string theory actually began as an attempt to understand QCD, before being abandoned ... 13:46: And asks whether the methods of string theory are being brought back to understanding gluons again? 13:56: The core mechanics of string theory were developed to describe the very stringy one-dimensional gluon bonds between quarks, particularly in mesons. 14:20: Quantum chromodynamics actually started to explain was going on, so it suplanted hadronic string theory. 14:28: ... modes of these strings looked like the graviton, so the entire theory was shrunk in size by about 20 orders of magnitude and developed into a ... 14:41: We explain everything in our string theory episodes. 14:45: ... now, decades later, with string theory still failing to produce a slam-dunk testable prediciton, people are ... 14:41: We explain everything in our string theory episodes.
	2022-09-14: Could the Higgs Boson Lead Us to Dark Matter? 07:34: ... is a whole family of potential theories of how the Higgs could interact with dark matter, these all fall under ...
	2022-08-24: What Makes The Strong Force Strong? 21:07: ... don't get caught in the same trap as the proponents of theories of quantum consciousness, or that aliens built the pyramids, or that ...
	2022-08-17: What If Dark Energy is a New Quantum Field? 13:27: ... on itself. But this flexibility makes it hard to actually falsify the theory - it’s just too easy to come up with a behavior of the field that fits ...
	2022-08-03: What Happens Inside a Proton? 00:22: ... how the universe should behave - that lets  us test our theories and basically become   wizards capable of predicting the ... 00:45: ... about the hack that lets us do it anyway - density functional theory. ... 02:06: ... with a gluon. Instead we need to figure out   what the theory predicts about properties of hadrons that are actually measureable. ... 07:07: ... for the behavior of   quarks, how can we even test the theory?  Well, we need to abandon Feynman diagrams.   In fact, we need ...
	2022-07-20: What If We Live in a Superdeterministic Universe? 01:12: Pilot wave theory, objective collapse models, and even the Many Worlds interpretation all seek to describe a reality that exists sans observers. 07:24: According to the Bell theorem, any local-realist theory must obey the Bell inequality. 07:40: ... a local realist theory, every point in space and time - every event - can only be influenced by ... 07:59: Things like pilot wave theory and objective collapse models try to do that. 09:52: In Bell’s theorem, his inequality is satisfied in local-realist theories - but there is another condition to the validity of the theorem. 01:12: Pilot wave theory, objective collapse models, and even the Many Worlds interpretation all seek to describe a reality that exists sans observers.
	2022-06-22: Is Interstellar Travel Impossible? 15:52: ... view that we will call model-dependent realism: the idea that a physical theory or world picture is a model and a set of rules that connect the elements ... 17:58: We have robust theories for the unification of the three quantum forces. 18:03: And we even have ideas for black holes in theories of quantum gravity - for example, the fuzzball of string theory, which we did an episode on. 18:26: Could this, for example, show us how black holes deviate from theory? 18:42: Actually, simply gaining information about the interior of the black hole this way is counter to the orthodox black hole theory. 15:43: In his book The Grand Design” Hawking says, and I quote, “There is no picture- or theory-independent concept of reality.
	2022-06-15: Can Wormholes Solve The Black Hole Information Paradox? 00:26: ... come when we noticed inconsequential seeming inconsistencies in our theories. The fact that   Maxwell’s electromagnetism didn’t square ... 05:20: ... radiation is our information escape route from the black hole. Any theory trying   to solve the black hole information paradox  has ... 06:01: ... advanced form of this is AdS/CFT correspondence, a branch of string theory that reveals that a   particular type of universe with three ... 06:54: ... relativity  and accepted quantum mechanics - no string   theories attached. To be fair, these US teams, dubbed the “east-coast” and ... 07:24: ... tidal wave of math in these papers  pulls ideas from string theory, holography,   quantum field theory, and  quantum ... 11:25: ... The researchers were surprised to find  that you don’t need string theory to   derive the island rule: all you need  is the ... 07:24: ... pulls ideas from string theory, holography,   quantum field theory, and  quantum computing to name a few fields.   We’re going to focus ... 11:25: ... The researchers were surprised to find  that you don’t need string theory to   derive the island rule: all you need  is the gravitational path ... 05:20: ... radiation is our information escape route from the black hole. Any theory trying   to solve the black hole information paradox  has to exactly ... 00:26: ... But there is another less well known  glitch between GR and quantum theory   that might provide a way forward. I’m talking about the black hole ... 11:25: ... this equation. The island rule had already been derived in string theory.   The researchers were surprised to find  that you don’t need string ...
	2022-06-01: What If Physics IS NOT Describing Reality? 00:25: ... work best. But actually, some of the   founders of quantum theory were convinced that  the role of physics was one step further ... 05:53: ... “quanta of information”,   we see the indeterminacy of quantum theory arises  naturally. Zeilinger even managed to derive the   ... 00:25: ... laws of nature which   we formulate mathematically in quantum theory deal  no longer with the particles themselves but with   our ... 08:49: ... idea leads us   naturally to some other staples of quantum theory  - like the Heisenberg uncertainty principle.   In a previous ... 11:24: ... one thing to use quantum information theory  as a mathematical tool, but quite another to claim   that ... 08:49: ... idea leads us   naturally to some other staples of quantum theory  - like the Heisenberg uncertainty principle.   In a previous ... 09:26: ... fact, by bringing to bear  the tools of information theory   we can derive an even tighter uncertainty relation  - something ...
	2022-05-04: Space DOES NOT Expand Everywhere 00:19: ... away from us, and interpreted through the lens of Einstein’s general theory of relativity, this only makes sense if all distances everywhere are ... 08:51: ... tough one - in fact an impossible one because we don’t have an accepted theory for what that the fabric of space is actually made out of, if anything. ...
	2022-04-27: How the Higgs Mechanism Give Things Mass 04:37: ... to each other.   To see if we can duplicate that in our theory  we need to combine the U(1) and SU(2) symmetries   so that ...
	2022-04-20: Does the Universe Create Itself? 00:59: ... himself. We’ve talked about this debate between the founders of quantum theory before, and of some of the supposed resolutions, which I’ll come back ... 01:59: ... in the behavior of the wavefunction, such as de Broglie-Bohm pilot wave theory or objective collapse interpretations. Still others sought to explain ...
	2022-03-30: Could The Universe Be Inside A Black Hole? 00:19: Einstein’s ridiculously successful general theory of relativity has never failed.
	2022-03-23: Where Is The Center of The Universe? 02:57: His general theory of relativity explains gravity as the warping of space and time due to the presence of mass and energy. 10:45: Stand by for our theory of quantum gravity to resolve that one.
	2022-03-16: What If Charge is NOT Fundamental? 03:14: In this theory the proton would be the “up” state with isospin 1/2, and the neutron would be the down state with isospin -1/2.
	2022-03-08: Is the Proxima System Our Best Hope For Another Earth? 16:39: ... doing comments on the last two episodes: the one on objective collapse theories, where wavefunction collapse is explained as a real, physical ... 17:58: ... quantum mechanics and quantum field theory assume a well-defined underlying framework, upon which all the quantum ... 18:22: Resolving that has been the major work of all of our searches for quantum gravity and theories of everything. 17:58: ... quantum mechanics and quantum field theory assume a well-defined underlying framework, upon which all the quantum ...
	2022-02-23: Are Cosmic Strings Cracks in the Universe? 12:19: ... a cosmic   superstring? You’ve probably heard of string  theory - we’ve certainly talked about it enough   on this show. It’s ...
	2022-02-16: Is The Wave Function The Building Block of Reality? 02:24: ... proposed by Werner Heisenberg, one of the principle founders of quantum theory. Heisenberg and his friend Neils Bohr were convinced that this wave ... 03:24: ... all of these ideas in the past. We also have de Broglie-Bohm pilot wave theory, where particles already have defined properties that are hidden within ... 03:59: ... function as the fundamental building block of reality, unlike pilot wave theory. And one which avoids multiple universes by insisting that collapse does ... 04:17: ... Weber published a paper that outlined what was to become known as GRW theory - the first in a new class of alternate quantum theories called ... 04:36: ... objective collapse theories, wave functions are real, physical entities that literally collapse when ... 04:54: To understand how objective collapse theories work, we need just a little more quantum mechanics. 08:02: ... was a revolutionary theory that inspired many subsequent models, like Continuous Spontaneous ... 09:25: ... into a classical object. Instead of gravity being quantized, Penrose’s theory predicts quantum mechanics will be “gravitized.” For example, consider a ... 10:19: ... are not mere interpretations of quantum mechanics — they are distinct theories with unique predictions. This means that, unlike other interpretations ... 04:17: ... Weber published a paper that outlined what was to become known as GRW theory - the first in a new class of alternate quantum theories called “objective ... 02:24: ... proposed by Werner Heisenberg, one of the principle founders of quantum theory. Heisenberg and his friend Neils Bohr were convinced that this wave function ... 09:25: ... into a classical object. Instead of gravity being quantized, Penrose’s theory predicts quantum mechanics will be “gravitized.” For example, consider a massive ...
	2022-02-10: The Nature of Space and Time AMA 00:03: ... brave efforts to try to figure it out the emerging generations of theories of quantum gravity theories of the theme some of them try to answer ...
	2022-01-27: How Does Gravity Escape A Black Hole? 00:35: ... 1915 Einstein presented to the world the equations behind his general theory of relativity, which describe gravity not as a traditional force, but ... 00:48: Einstein’s theory predicted the existence of the ultimate gravitational object: the black hole. 01:01: ... to Einstein’s theory, any object that reaches such a density has to collapse to a point-like ... 01:21: ... = \kappa T_{\mu\nu} so they would be consistent with his special theory of relativity, which describes how lengths and times and other ... 05:43: But we know that GR is not the final theory. 05:54: ... physicists believe that general relativity needs to be replaced by a theory of quantum gravity to explain the behavior of gravity in these ... 06:08: Now in quantum mechanics - or more specifically quantum field theory - forces are mediated by particles, not by the geometry of spacetime. 06:28: In theories of quantum gravity, the gravitational force should probably also have a mediating particle - usually called the graviton. 07:55: That’s easy - these are virtual particles, and in quantum field theory, virtual particles are not restricted by the speed of light. 08:39: ... we’re talking about the classical gravity of Einstein or some deeper theory of quantum ... 13:06: ... of information in the quantum wavefunction with density functional theory, and then went from the tiny to the enormous, exploring how we do ... 13:42: ... with our reality, is an indicator that there's a much simpler underlying theory on the order of complexity of that small ... 14:21: We said that in density function theory you start with a make-believe system of non-interacting electrons. 06:08: Now in quantum mechanics - or more specifically quantum field theory - forces are mediated by particles, not by the geometry of spacetime. 00:48: Einstein’s theory predicted the existence of the ultimate gravitational object: the black hole. 07:55: That’s easy - these are virtual particles, and in quantum field theory, virtual particles are not restricted by the speed of light.
	2022-01-12: How To Simulate The Universe With DFT 08:49: ... stands for density functional theory, and it’s perhaps the most successful approach to tackling the extreme ... 09:01: ... of atoms comprising the capsid of a virus done using density functional theory, and here’s resonant excitation in the many electrons of a ... 11:54: The secret sauce that makes this work is something called the energy functional - it’s the functional in density functional theory. 12:51: ... functional theory has now been used to model the intricate quantum-level behavior of ...
	2021-12-20: What Happens If A Black Hole Hits Earth? 10:44: ... made by regular old rocks is hard, but not impossible thanks to some new theory work. Recently, some scientists have calculated how the shape of a black ... 14:10: ... an explanation for dark matter, and the one on fuzzballs - the stringy theory version of the black ... 14:26: ... 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 respond: “It can scarcely ... 17:55: ... tested. Actually, this might be the most testable prediction of string theory. There are simulations that suggest that the gravitational waves created ... 14:26: ... 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 respond: “It can scarcely be ... 14:10: ... an explanation for dark matter, and the one on fuzzballs - the stringy theory version of the black ... 10:44: ... made by regular old rocks is hard, but not impossible thanks to some new theory work. Recently, some scientists have calculated how the shape of a black ...
	2021-12-10: 2021 End of Year AMA! 00:02: ... that massive bodies bend the paths of light according to einstein's theory of general relativity so when you look out there you see you know ...
	2021-11-17: Are Black Holes Actually Fuzzballs? 00:18: String theory, in fact. 00:20: ... in the black holes of string theory - fuzzballs - are perhaps even weirder than the regular type Einstein’s ... 04:23: The impossibility of the central singularity is the most obvious place where we need a theory of quantum gravity. 04:32: A theory of quantum gravity would have really helped Stephen Hawking in deriving his eponymous radiation. 04:39: But such a theory didn’t exist back then in the 70s and still doesn’t. 05:22: And it turns out that our most advanced theory of quantum gravity can do this quite neatly. 05:28: Black hole paradoxes may be solved by string theory. 05:32: In string theory, black holes are not hairless at all - in fact all of those strings make them positively fuzzy. 05:43: First a spot of string theory. 05:52: ... string theory, all elementary particles are oscillations in 1-dimensional strands that ... 06:01: ... theory immediately solves the problem of the black hole singularity, because ... 06:17: It turns out that though, that string theory can make sense of the black hole event horizon also. 06:22: ... when Andrew Strominger and Cumrun Vafa created a black hole using string theory - in theory-space, not ... 07:04: The infinitesimal strings and branes of string theory might be the analog of the molecules that store the entropy of our room full of air. 07:13: ... a decisive step and it gave us a compelling reason to think that string theory might explain where the microstates of black holes ... 08:00: This was another stunning match to theory, and also a way for stringy black holes to leak out their information. 08:39: This property of black holes is actually quite hard to reproduce in theories of quantum gravity. 09:52: The ability for strings to maintain structure in this extreme gravity comes down to an effect specific to string theory called fractionation. 10:10: ... in string theory, when you merge a large number of strings, the tension of the resulting ... 12:20: In string theory we have extra compact dimensions - spatial dimensions that are coiled up on the Planck scale so we can’t see them. 13:00: ... emergence of fuzzballs in string theory radically changed our vision of what a black hole could be and provided ... 00:20: ... in the black holes of string theory - fuzzballs - are perhaps even weirder than the regular type Einstein’s ... 06:22: ... when Andrew Strominger and Cumrun Vafa created a black hole using string theory - in theory-space, not ... 00:20: ... in the black holes of string theory - fuzzballs - are perhaps even weirder than the regular type Einstein’s general ... 05:32: In string theory, black holes are not hairless at all - in fact all of those strings make them positively fuzzy. 09:52: The ability for strings to maintain structure in this extreme gravity comes down to an effect specific to string theory called fractionation. 04:39: But such a theory didn’t exist back then in the 70s and still doesn’t. 13:00: ... emergence of fuzzballs in string theory radically changed our vision of what a black hole could be and provided a ... 06:22: ... Strominger and Cumrun Vafa created a black hole using string theory - in theory-space, not ...
	2021-11-10: What If Our Understanding of Gravity Is Wrong? 01:34: After all, if your scientific theory doesn’t fit observations we should reject our theory, right? 01:39: ... for dark matter, others have been hunting for an alteration to our theory of gravity that can explain the effect of dark matter without the actual ... 08:50: ... laws were obeyed,   and because this was a relativistic theory it was possible to see if it gave the right result for the bending of ... 12:25: Modified gravity theories still can’t explain the Bullet Cluster - and I don’t have time to get into that and we’ve covered it before. 12:54: At this point the two theories are in a bloody theoretical knife fight, where the knife is Occam’s razor. 13:44: But Bekenstein was no slouch, nor are many of  the others who have supported MOND theories. 15:45: ... quantum mechanics and relativity, what's missing to make this  a theory of ... 01:34: After all, if your scientific theory doesn’t fit observations we should reject our theory, right? 02:52: ... the gravitational field gets too strong - there you need his general theory  of relativity, which explains gravity as the curvature in the fabric of ...
	2021-11-02: Is ACTION The Most Fundamental Property in Physics? 05:24: ... then it should apply well beyond classical mechanics and into our modern theories - in particular general relativity and quantum mechanics. And perhaps in ... 05:52: ... start with Einstein’s General Theory of Relativity, which, as we’ve discussed before, describes the force of ... 12:59: ... to the evolution through quantum states underpins modern quantum theory. Back to Paul Dirac just for a moment. His eponymous equation was derived ... 15:27: ... get into your comments on our recent episode on constructor theory. This was a contentious one. Many of you were dubious that constructor ... 15:51: Nestor de Buen asks: Isn’t this more of an epistemological framework than a theory? 15:58: ... of science collaborated more. So my sense is that constructor theory does try to bring a philosophical perspective shift, which in principle ... 16:26: ... of the math - Corbin Simpson and Skooks say that constructor theory sounds like category theory. I only learned about category theory while ... 17:15: This is all some pretty obtuse stuff, and some of you did better at explaining the point of constructor theory than I did, so let me just summarize. 17:24: ... Andy points out that constructor theory seeks to narrow down the space of all possible functions that might ... 17:54: ... spacetime, invariance, quantum etc.) then constructor theory gives us insights as to what math is possible, and what math should be ... 18:34: ... notes that constructor theory feels like alchemy. Relatedly, Cluebcke says “Rough shade on Newton with ... 18:52: ... lines of inquiry would be “fruitful” without exploring them? Constructor theory might be another alchemy, or it might be another Newtonian mechanics. ... 15:58: ... behind it also, which I understand is based on set theory and ergodic theory - and for a great resource on those I recommend … the ... 18:34: ... notes that constructor theory feels like alchemy. Relatedly, Cluebcke says “Rough shade on Newton with that ... 17:24: ... Andy points out that constructor theory seeks to narrow down the space of all possible functions that might represent ... 16:26: ... the internet. Chapter 7.4 I think. But as far as I understand, category theory, set theory, and presumably constructor theory, are all attempts at ...
	2021-10-20: Will Constructor Theory REWRITE Physics? 00:00: ... and from simple statements about reality they built up their incredible theories. ... 01:30: ... a set of equations for each separate aspect of the world - but if these theories are really true then they should ultimately come together into some ... 01:43: ... and Newtonian mechanics and electromagnetism and so on from two master theories: quantum mechanics and Einstein’s general ... 01:53: But the master theory that unifies those last two has so far eluded us. 01:58: ... come up with dynamical laws that describe all of nature - a mechanistic theory of ... 02:15: One such approach is constructor theory, developed by David Deustch and Chiara Marletto at Oxford University since 2012. 02:31: In constructor theory, the fundamentals are simpler - they are binary facts about whether or not a particular process is possible. 02:40: ... uses theories like general relativity and quantum mechanics, along with more ... 03:05: Constructor theory is inspired by information theory and the theory of quantum computation. 03:11: ... process in physics, then all of physics can be expressed in terms of the theory of quantum ... 03:54: ... constructor theory is about something called a counterfactual - which in constructor theory ... 04:21: The power of constructor theory is that it allows us to explore physics without having to solve the detailed equations of motion. 04:47: Before we get to how constructor theory is going to explain everything, let’s look at a simple example to define some of these concepts. 05:18: In the constructor theory view, we ask what tasks are possible and impossible for the apple given its input state. 05:57: This just serves to give  an idea of the perspective  shift in constructor theory. 07:38: An aim of constructor theory is to formalise our statements about what is possible and impossible into a sort of  “algebra of possibility”. 07:47: At its heart, constructor theory is based on information theory and uses related tools like set theory in its formalism. 07:58: ... means that constructor theory can be applied even when we don’t know the dynamical laws of a system - ... 08:07: For example Chiara Marletto has used constructor theory to describe a scenario for testing whether gravity is quantum in nature. 08:16: And we certainly don’t have a mechanistic theory for quantum gravity. 09:47: This is cool because it gives us an experimental test of quantum gravity that has absolutely no dependence on a particular theory of quantum gravity. 09:55: It doesn't need the dynamical laws of such a theory, or even of quantum mechanics or general relativity as they currently stand. 10:02: ... it pares down the facts that we need to assume about the mechanistic theory in order to make the argument - in this case, just the way informational ... 10:15: ... Deustch has said that constructor theory may be the most fundamental way to describe reality - in which case the ... 10:28: That’s a lofty claim, but consider how previous great theories emerged. 10:42: ... general theory of relativity came from asking what were the inevitable implications of ... 11:04: ... has called such efforts “antecedents” of constructor theory, which sounds presumptuous, but it gets to the spirit of the effort: to ... 01:30: ... really true then they should ultimately come together into some master theory - and they do, to an ... 02:15: One such approach is constructor theory, developed by David Deustch and Chiara Marletto at Oxford University since 2012. 05:18: In the constructor theory view, we ask what tasks are possible and impossible for the apple given its input state. 11:52: ... would be impossible,   which in the language of constructor theory  makes you a counterfactual. We are humbled   and grateful ...
	2021-10-13: New Results in Quantum Tunneling vs. The Speed of Light 00:10: ... efforts in quantum tunneling - both theory and experiment - show that superluminal motion may be possible, while ... 05:27: ... we’ve said before, his theory of special relativity explains that if you move faster than light, you ... 07:45: ... the Schrodinger equation, which doesn’t incorporate Einsteins’s special theory of relativity and so has no speed limit baked into ... 11:45: The spins were altered by pretty much the same amount that theory predicted they would be. 12:02: The point is that the theory and the experimental tools are now converging on a way to answer our questions once and for all. 11:45: The spins were altered by pretty much the same amount that theory predicted they would be.
	2021-10-05: Why Magnetic Monopoles SHOULD Exist 02:18: Well, according the classical theory we shouldn’t. 03:54: ... not forbidden is compulsory." meaning that if the math of our physical theory allows it, then it exists in ... 04:21: At least according to classical theory. 04:26: ... quantum theory first appeared it quickly revolutionized our understanding of ... 05:09: ... particular, the magnetic field emerging from the quantum theory must have zero divergence - its field lines can never end - so it can’t ... 09:08: With that squared away, physicists were working to bring the strong nuclear force into the fold with the so-called Grand Unified Theories. 09:37: ... in electroweak theory, the Higgs field is a scalar field - it takes on a numerical value ... 09:55: In the simplest grand unified theory, the Higgs field has three degrees of freedom instead of two. 10:55: And it turns out these knots in the Higgs field in GUT theories behave as massive particles with magnetic charge - magnetic monopoles. 11:12: ... turns out that GUT theories generically predict these magnetic monopoles, and that they should be A) ... 11:29: The fact that magnetic monopoles should exist in these theories was both exciting and problematic. 11:54: This conflict with reality might have ruled out both monopoles and the grand unified theories that predict them. 13:13: ... lower than is needed to produce the monopoles predicted by grand unified theories. ... 13:42: Their discovery would mean cracking open the grand unified theories and revealing mysteries far beyond. 17:56: Physicists hope to understand these things someday, perhaps with twistor or string theory. 18:01: Or maybe you could just use USBC - they’re spin-2 bosons like gravitons, so easily understood with a basic theory of quantum gravity.
	2021-09-07: First Detection of Light from Behind a Black Hole 11:33: ... of the black hole - 30 million Suns - to verifying Einstein’s general theory of ...
	2021-08-18: How Vacuum Decay Would Destroy The Universe 08:30: ... For example, there may be weird fields within string theory that exist in false vacuum states.   The decay of those could ...
	2021-08-10: How to Communicate Across the Quantum Multiverse 02:29: ... of measurement, leaving only one reality; or de Broglie-Bohm pilot wave theory, which says that particles are particles and waves are waves - and the ... 02:56: ... is perfectly consistent with the equation that lies at the heart of the theory - that’s the Schrodinger ...
	2021-08-03: How An Extreme New Star Could Change All Cosmology 17:08: ... with a brutal analysis of the psychology of pseudoscience conspiracy theories. I will just say this: if electromagnetism really does govern everything, ...
	2021-07-13: Where Are The Worlds In Many Worlds? 03:39: Quantum mechanics is a theory about waves.
	2021-07-07: Electrons DO NOT Spin 04:40: ... and has all the weirdness you’d expect from  the weirdest of theories. But before we dive into that weirdness, let me give you one more  ... 08:28: ... equation - in this case to make it work with Einstein’s special theory of relativity - something we’ve discussed  before. Dirac wasn’t ... 15:31: ... about quantum gravity and inflation and whatever  other crazy theory we haven’t figure out yet. But what we do know is that at some ... 17:29: ... named after Dr, Shannon, the founder of the  field of information theory. As with many of these things, the word has been corrupted  over ...
	2021-06-23: How Quantum Entanglement Creates Entropy 00:27: ... supreme  position among the laws of Nature...   if your theory is found to be against the Second Law of Thermodynamics I can give ... 03:45: ... It was Claude Shannon   who founded the field of Information theory, and also invented the entropy of information - Shannon   ... 04:50: ... he first came up with this theory, though, Shannon didn’t fully realize its importance.   As ... 03:45: ... It was Claude Shannon   who founded the field of Information theory, and also invented the entropy of information - Shannon   entropy. ... 04:50: ... he first came up with this theory, though, Shannon didn’t fully realize its importance.   As the (perhaps ... 05:55: ... least incredibly powerful. It’s at the heart of quantum information theory,   enabling us to calculate how much quantum information is contained ... 03:45: ... it took the invention of information theory to really see the connection between information and entropy. It was Claude ...
	2021-06-16: Can Space Be Infinitely Divided? 10:55: ... scale - but we just don’t know in what way. We need a theory of quantum gravity to answer this.   We’ll come back to what ...
	2021-05-25: What If (Tiny) Black Holes Are Everywhere? 00:41: At least, that’s the black hole as it appears in the mathematics of Einstein’s general theory of relativity. 01:57: Now to do this properly, you really need a theory of quantum gravity, which we don’t even have now and certainly didn’t in 1974. 04:49: At that point you need a proper theory of quantum gravity to describe the process. 04:53: ... that theory, we have no way to describe the final stage of black hole evaporation - ... 07:16: But assuming that they a[re allowed in the theory, are they also allowed in the real universe?
	2021-05-11: How To Know If It's Aliens 14:35: ... covering comments from the last two episodes: our update on warp drive theory, and the one about whether dark matter can be explained by enormous ... 14:48: ... pure general relativity, and we know for sure that GR is not our final theory of nature because it doesn’t perfectly gel with quantum mechanics. So ... 18:32: ... to check. I like this a lot. Looking for dark matter in, say, string theory, before you check whether it’s black holes is like looking for your keys ...
	2021-04-21: The NEW Warp Drive Possibilities 00:31: In 1915, Albert Einstein’s general theory of relativity revealed that the fabric of space and time is mutable and dynamic. 02:30: His special theory of relativity just says that it takes infinite energy to accelerate anything with positive mass all the way to light speed. 03:29: It’s a sp acetime geometry that is a valid solution to the equations general theory of relativity. The Einstein Field Equation. 08:54: OK, let’s move on to the second paper by Erik Lentz: “Breaking the Warp Barrier: Hyper-Fast Solitons in Einstein-Maxwell-Plasma Theory”. 10:53: ... assert for Alcubierre’s bubble - it can exist at superluminal speeds in theory, but there’s no known way to get it to those speeds in the first ... 11:36: ... warp fields exist in theory, and there’s a very tentative hints that the worst deal-breaker can be ... 12:37: They’ll continue to try to “make it so” by exploring Einstein’s theory - hoping to build starship, but in the process learning how our universe works.
	2021-04-13: What If Dark Matter Is Just Black Holes? 00:44: ... are trying to find holes in Einstein’s theory of gravity - the general theory of relativity - that might explain dark ...
	2021-04-07: Why the Muon g-2 Results Are So Exciting! 00:00: - When a theory makes a prediction that disagrees with an experimental test. 00:04: Sometimes it means we should throw that theory away. 00:07: But what if that theory has otherwise produced the most successful predictions in all of physics. 00:47: In fact, it doesn't play nice with Einstein's entire theory of gravity, which itself is clearly right in its own way. 00:54: Our search for a theory of everything which will bring these theories together is perhaps the next great question physics. 01:00: To find the path forward, we need to find glitches in these theories. 01:11: These theories are woven pretty tight but there is one glitch, one stray thread that is just begging to be tugged. 04:33: In this theory, electromagnetic interactions result from charge particles communicating by exchanging virtual photons. 09:05: Until now, it had been measured precisely enough to claim a 3.7 sigma difference, compared to theory. 04:33: In this theory, electromagnetic interactions result from charge particles communicating by exchanging virtual photons.
	2021-03-23: Zeno's Paradox & The Quantum Zeno Effect 05:07: ... can be halted if you continuously measure the state - again, in theory. ... 07:23: In theory, if these “measurements” are fast enough they should stop the wavefunction from evolving.
	2021-03-09: How Does Gravity Affect Light? 00:28: That fact is guaranteed by Einstein’s general theory of relativity. 01:17: ... assumed that Isaac Newton’s theory of gravity was the full picture, and that light behaves like any other ... 07:31: Huygens’ wave theory of light advanced the field of optics enormously. 09:41: As you might expect from a theory called “relativity”, stuff is relative.
	2021-02-24: Does Time Cause Gravity? 00:34: ... as surely as 1+1=2 if we accept the two axioms of Einstein’s relativity theory: that the speed of light is constant for all observers, and that the ...
	2021-02-17: Gravitational Wave Background Discovered? 00:00: ... particles well many maybe most physicists working in the area think a theory of quantum gravity will reveal that the gravity field space-time ...
	2021-02-10: How Does Gravity Warp the Flow of Time? 01:13: Einstein had his happy thought in 1907, a couple of years after he started his scientific revolution with the special theory of relativity. 01:22: It took him another 8 years and a lot of help to grow this simple idea into his full theory of gravity - the general theory of relativity.
	2021-01-26: Is Dark Matter Made of Particles? 05:52: ... a dark matter particle may be our best for finding a bigger, deeper theory than the standard ... 06:25: The other delves deep into theory - in speculative mathematics beyond the standard model for signs of new particles.
	2021-01-19: Can We Break the Universe? 00:09: ... was already rocking our understanding of the universe with his special theory of ... 00:17: ... theory started with the simple assumption that the speed of light was the ... 12:05: ... so we make sense of this deeply strange, but unfailingly self-consistent theory of Einstein’s ... 15:12: ... of Tokyo reported on a new experiment that helped validate this theory. ... 15:40: This is the first time the flourescence has been directly observed, so it lends credence to the theory. 00:17: ... theory started with the simple assumption that the speed of light was the fastest speed ...
	2021-01-12: What Happens During a Quantum Jump? 01:56: ... was the Bohr model of the atom - the very first attempt at a quantum theory, and it very neatly explained the specific frequencies of light observed ... 03:14: ... quantum jumps, I am sorry that I ever had anything to do with quantum theory.” Schrödinger became bed-ridden with an illness during that visit - ... 03:40: ... two-part essay titled “Are there quantum jumps?” wherein he compared the theory of quantum jumps to that of epicycles—the long dead theory about the ... 04:07: Simply put, they seemed unnatural and unphysical - a hack added to cover up a phenomenon that quantum theory could not yet properly explain. 09:47: And that transition appeared to be perfectly described by theory - in this case quantum trajectory theory. 03:14: ... quantum jumps, I am sorry that I ever had anything to do with quantum theory.” Schrödinger became bed-ridden with an illness during that visit - perhaps he was ...
	2020-12-22: Navigating with Quantum Entanglement 02:52: ... theories have suggested that birds have iron structures in their beaks which help ...
	2020-12-15: The Supernova At The End of Time 05:27: ... failed to incorporate the effects of Albert Einstein’s relativity theory, which predicted that the world looks very different to things traveling ...
	2020-12-08: Why Do You Remember The Past But Not The Future? 12:23: ... highlights a real mystery with the big bang theory The distribution of matter and energy in the early universe does appear ...
	2020-11-18: The Arrow of Time and How to Reverse It 09:39: ... not the future, we need to delve deeper. In fact it involves information theory and quantum entanglement, so we need another episode. Or more than one. ... 10:20: ... now we’re looking at comments from the last two episodes - electroweak theory and our discussion on free will in ... 10:34: ... electroweak theory Marik Zilberman has a really good comment. If the current fundamental ... 13:36: ... quantum electrodynamics, which comes from ontology: 1. A physics theory with a cool abbreviation is inherently better than a physics theory ... 13:58: therefore Quantum electrodynamics is better than other physics theories. 10:34: ... electroweak theory Marik Zilberman has a really good comment. If the current fundamental forces ...
	2020-11-11: Can Free Will be Saved in a Deterministic Universe? 10:42: You can get this sort of singular hard determinism with things like DeBroglie-Bohm pilot-wave theory.
	2020-11-04: Electroweak Theory and the Origin of the Fundamental Forces 02:56: QED is what we call a gauge theory - its force-carrying fields and particles arise from the symmetries of the quantum equations of motion. 04:02: Anyway, this new gauge theory of the weak interaction seemed to be okay with parity violation, and it wasn’t only accurate at low energies. 04:28: At least assuming that the symmetries of gauge theory remain intact. 04:44: To get all of this we need to do a quick recap of what a gauge theory actually is. 05:54: So that is gauge theory in a nutshell: it explains a force by imposing symmetries on the equations of motion. 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. 14:10: ... because it causes unreconciled conflicts with other physics - quantum theory in this ... 02:56: QED is what we call a gauge theory - its force-carrying fields and particles arise from the symmetries of the quantum equations of motion. 04:28: At least assuming that the symmetries of gauge theory remain intact.
	2020-10-27: How The Penrose Singularity Theorem Predicts The End of Space Time 00:00: ... is much deeper - it leads us to the limits Einstein’s  great theory and to the origin of the ... 00:34: ... holes have haunted our  theories of gravity since the 1700s.   When John Mitchell and ... 01:17: ... often than not they turn out to be a glitch   in the theory. Einstein himself doubted that  the black holes could form in the ... 03:18: ... out how to describe a rotating black   hole in Einstein’s theory. In it, the central point of infinite gravity is spun out into ... 03:38: ... new advances in general relativity, half  a century after the theory was ... 11:10: ... should be dubious when we see infinities and singularities in our theories. Penrose   showed us that singularities are unavoidable ... 13:38: ... function or the empty wavefunctions of   pilot wave theory - if we continue to try and fail to detect these required ... 01:17: ... often than not they turn out to be a glitch   in the theory. Einstein himself doubted that  the black holes could form in the real ... 13:38: ... equation. Other   interpretations - Copenhagen, pilot wave theory, etc. actually add things to the pure evolution   of the ...
	2020-10-20: Is The Future Predetermined By Quantum Mechanics? 00:00: - Einstein's Special Theory of Relativity combines space and time into one dynamic unified entity, spacetime. 11:10: ... should make an honorable mention de Broglie-Bohm pilot wave theory, This is an entirely deterministic interpretation that doesn't have ... 11:27: ... universe of pilot wave theory is really a block universe but unfortunately, no one has convincingly ... 11:51: So does the future already exist according to quantum theory?
	2020-10-13: Do the Past and Future Exist? 05:53: ... his special theory of relativity, Einstein showed that there’s no absolute way to define ...
	2020-09-28: Solving Quantum Cryptography 15:06: The theory just isn’t there. 15:35: Well, first let me say that magnetic monopoles may well exist - in fact mainstream grand unified theory candidates routinely predict them.
	2020-09-21: Could Life Evolve Inside Stars? 12:12: ... tor Sabine’s own words read the book and check out our Theories of Everything livestream from a month ago, also with Lee Smolin and Eric ... 13:43: ... the epicycles in Ptolemy’s theory, Ry706 says “adding epicycles upon epicycles can represent any motion is ... 12:21: ... the importance of mathematical beauty, by some, perhaps by many, in the theory-of-everything ...
	2020-09-08: The Truth About Beauty in Physics 00:37: ... been argued that modern theoretical physics, and in particular string theory, has been overly transfixed by the allure of beauty for decades, and that ... 06:45: ... a good time for a quote from Einstein himself: “The supreme goal of all theory is to make the irreducible basic elements as simple and as few as ... 08:58: Nobel laureate physicist Frank Wilcek talks about a form of mathematical beauty that he calls the exuberance of a theory - its productivity. 09:42: ... off a roof, or a photon bouncing between mirrors - but the resulting theory predicts black holes, gravitational waves, and even the big ... 10:01: ... couple of years after Einstein presented his general theory of relativity - Weyl found a simple, elegant way to unify Einsteinian ... 10:22: But Weyl’s theory made some predictions that simply did not reflect the real universe - ultimately it was just plain wrong. 10:29: ... had a hard time accepting that such a beautiful theory could be wrong, and he modified his idea to fix the issues - added some ... 10:44: So now we come to string theory. 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. 10:54: But there are other things too - for example, disparate versions of string theory seem to miraculously converge into one master theory. 11:15: So did string theory fall for the same sort of misguided obsession with beauty as did Weyl? 12:11: And so perhaps the mathematical wonders of string theory DO reflect something true about reality, but we’re struggling with how to interpret it all. 08:58: Nobel laureate physicist Frank Wilcek talks about a form of mathematical beauty that he calls the exuberance of a theory - its productivity. 11:15: So did string theory fall for the same sort of misguided obsession with beauty as did Weyl? 09:42: ... off a roof, or a photon bouncing between mirrors - but the resulting theory predicts black holes, gravitational waves, and even the big ...
	2020-09-01: How Do We Know What Stars Are Made Of? 00:39: A hundred years ago, we were starting to plumb the deepest mysteries of the universe with Einstein’s relativity and with quantum theory. 01:43: ... solar eclipse expedition in which he verified Einstein’s new general theory of ... 06:13: ... read and so she knew about some groundbreaking work in early quantum theory that she could use to decode the complex patterns of absorption lines in ... 07:00: ... Indian astrophysicist Meghdad Saha had used early ideas in quantum theory to crack the ionization ... 07:19: Saha and others began to apply this theory to stellar absorption lines. 09:29: ... real” - that it was likely the result of not understanding the atomic theory of hydrogen and helium well ... 10:20: ... what stars are made of, he and others were able to develop a detailed theory of stellar ...
	2020-08-24: Can Future Colliders Break the Standard Model? 00:02: ... by omelet I mean a theory of everything, and by eggs I mean a billion billion subatomic particles ... 00:47: The hope is that this will open the window to brand new physics - and perhaps break the current deadlock in our quest for a theory of everything. 05:25: ... known particles and what we expect their masses to be from quantum field theory ... 07:07: ... general, to get closer to a theory that unifies our understanding of the Standard Model’s motley zoo of ... 05:25: ... known particles and what we expect their masses to be from quantum field theory calculations. ...
	2020-08-17: How Stars Destroy Each Other 11:50: ... think a theory of quantum gravity probably prevents the singularity from really forming ...
	2020-08-10: Theory of Everything Controversies: Livestream 00:00: ... today from loop quantum gravity which is one of the founders to string theory to the foundations of quantum mechanics and the philosophy of physics ...
	2020-07-28: What is a Theory of Everything: Livestream 00:00: ... it still relevant this conjecture to pursue these fanciful ideas about theories of everything and whether they exist so part of the motivation is to ...
	2020-07-20: The Boundary Between Black Holes & Neutron Stars 01:04: ... waveform, and based on calculations using Einstein’s general theory of relativity, the masses of those bodies were ... 07:19: ... not because our theories are wrong - it’s because the calculations required to understand the ...
	2020-07-08: Does Antimatter Explain Why There's Something Rather Than Nothing? 04:48: ... asymmetry problem. So, if there exists some underlying more fundamental theory, maybe string theory for example, then CPT symmetry may no longer be a ...
	2020-06-22: Building Black Holes in a Lab 11:04: ... holes. True Hawking radiation need not necessarily depend on a specific theory of quantum gravity. Proponents of this line of thought have triumphantly ...
	2020-06-08: Can Viruses Travel Between Planets? 14:22: ... theory is modified newtonian dynamics - MONDS - in which gravity doesn’t drop ... 14:44: ... from the stars and therefore can’t be due to just having the wrong theory of ... 15:49: ... and for the most part that dependency agrees with so-called lifshitz theory, which is based on this altered vacuum energy ... 16:13: Well I’d accuse you of propogating quantum woowoo, except that this theory is actually supported right at the top.
	2020-05-27: Does Gravity Require Extra Dimensions? 01:18: ... the mysteries about why gravity works the way it does, our current theories still describe how gravity behaves remarkably ... 01:28: ... general theory of relativity has a perfect track record predicting the behavior of ... 01:37: But even Newton’s old theory works great in almost all situations. 05:57: ... most famous example of compactified extra dimensions is in string theory, and in modern superstring theory there are 6 additional spatial ... 06:10: ... the idea of compact extra dimensions is much older than string theory - first proposed by Oscar Klein in the 1920s as part of what became ... 11:23: And while that may seem anticlimactic, it’s actually extremely useful, ruling out some theories and constraining the space of possibility from others. 11:32: ... being able to probe the size-scale of the extra dimensions from string theory though, and so string theorists can keep on ... 06:10: ... the idea of compact extra dimensions is much older than string theory - first proposed by Oscar Klein in the 1920s as part of what became ... 01:37: But even Newton’s old theory works great in almost all situations.
	2020-05-11: How Luminiferous Aether Led to Relativity 00:00: ... satisfied with the state of their science. The great edifice of physical theory seemed complete. A few minor experiments remained to verify everything. ... 01:09: ... death of the aether helped open the way for the acceptance of Einstein’s theory of ... 02:33: ... The Dutch physicist Christiaan Huygens developed a detailed mathematical theory around this idea that gravity results from the fluid dynamics of the ... 04:06: ... was sitting in Cambridge making life difficult for Huygens. First his theory on universal gravitation conflicted with the predictions of Huygens’ ... 11:42: ... of light and the Lorentz transformation are fundamental to his special theory of relativity, which was published 8 years after the Michelson-Morley ... 13:18: ... that death helped spark the revolutions of relativity and then quantum theory that revealed a much weirder, but still totally luminiferous space ...
	2020-05-04: How We Know The Universe is Ancient 03:09: ... makes perfect sense in the context of Einstein’s then-new general theory of ... 04:40: ... Lemaître himself disagreed, stating: “As far as I can see, such a theory remains entirely outside any metaphysical or religious question.” So if ... 07:07: ... years old! So there was a problem - but it wasn’t a problem with the theory, it was a problem with the observations. Edwin Hubble had got the ... 16:59: ... loves crawling into boxes whenever possible, I assume to test quantum theory. Miraculously emerging definitely alive every time. She's become a pretty ... 04:40: ... Lemaître himself disagreed, stating: “As far as I can see, such a theory remains entirely outside any metaphysical or religious question.” So if we can ...
	2020-04-28: Space Time Livestream: Ask Matt Anything 00:00: ... know Astro 101 except for the fact that I dearly love these old wrong theories I think they're so colorful and cool you know the the one electron ...
	2020-04-22: Will Wormholes Allow Fast Interstellar Travel? 01:09: ... along with Nathan Rosen, expanded on Flamm’s idea - but not into a theory of wormholes - instead as a theory of particles. Einstein and Rosen ... 14:59: ... matter interactions with the black hole. I'm afraid I don't know of any theory of dark matter that would do that. But who knows - dark matter is weird. ...
	2020-04-14: Was the Milky Way a Quasar? 09:12: Unfortunately, there’s a problem with this theory too. 09:43: So what - two nice theories and neither of them work? 15:12: ... Current theories on the creation of the Universe state that, if it was created at all and ...
	2020-04-07: How We Know The Earth Is Ancient 03:30: ... can thank Hutton and his 1788 book the Theory of the Earth for opening scientific eyes to the possibility of an ... 05:38: ... ideas gave Darwin the millions of years he needed for his theory of evolution, and its painfully slow mechanism of natural selection. But ...
	2020-03-31: What’s On The Other Side Of A Black Hole? 01:53: ... just a couple of months after Einstein published his general theory of relativity. It allows us to calculate the path of an object moving in ...
	2020-03-24: How Black Holes Spin Space Time 00:21: ... months after Einstein presented his complete general theory of relativity in 1915, a young German physicist named Karl Schwarzschild ... 05:14: ... B measured the Earth’s frame dragging and it was exactly as Einstein’s theory predicted - incredibly weak in Earth’s case. But in the case of a Kerr ...
	2020-03-16: How Do Quantum States Manifest In The Classical World? 15:05: One exciting new course is the Theory of Everything hosted by our friend, Dr. Don Lincoln. 15:11: ... learn what cutting edge science is doing to reconcile these two great theories. ...
	2020-02-18: Does Consciousness Influence Quantum Mechanics? 00:08: No, but then why did some of the founders of the theory seem to think that consciousness and quantum mechanics were inextricably linked. 01:25: Today we’re going to see where this idea comes from, and whether quantum theory really supports it. 06:01: Another of the greats of early quantum theory agreed with him. 09:40: ... you don't understand quantum mechanics." The more you know about this theory, the less likely you are to pretend you fully understand its deepest ... 10:01: ... tend to be made by people who have never studied the theory deeply, but nonetheless have great surety in cherry-picking and ... 12:09: ... Measurement Problem - at least not with full consensus, modern quantum theory has come a very, very long way since its ... 06:01: Another of the greats of early quantum theory agreed with him. 10:01: ... tend to be made by people who have never studied the theory deeply, but nonetheless have great surety in cherry-picking and misinterpreting ...
	2020-02-11: Are Axions Dark Matter? 03:02: ... weaker than predicted by a CP-violating QCD. This discrepancy between theory and experiment is known as the strong CP problem and is currently ... 03:59: ... 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 to describe ... 06:54: ... you might recall that in quantum field theory a particle is just an oscillation in a quantum field. So with a new ... 08:45: At least in theory - so far several experiments have not confirmed axions this way, at least so far.
	2020-02-03: Are there Infinite Versions of You? 12:19: ... and then we'll do our episode on quantum hacking with the s-matrix theory. ... 12:29: Ilavenya rightly points out that no nice analytical solutions to the 3-body problem exist in general relativity - Einstein's modern theory of gravity. 14:48: But in s-matrix theory and quantum field theory, time and space in the interaction region are fuzzy. 16:21: ... in our depiction of the proton being made of lego bricks as a viable theory - quantum lego dynamics, as Steve Plegge puts ... 14:48: But in s-matrix theory and quantum field theory, time and space in the interaction region are fuzzy.
	2020-01-27: Hacking the Nature of Reality 00:54: ... insights, with the final result being the birth of modern quantum theory and first complete formulation of quantum mechanics - matrix ... 02:16: ... search for the underlying clockwork of reality led to quantum field theory, in which all particles are described by vibrations in elementary fields ... 02:41: Early quantum theory was plagued by problems - for example, how do you compute infinite interactions? 02:55: ... clever hacks - perturbation theory and renormalization - worked in many cases to tame the infinities and ... 03:50: ... and time should break down at those scales, and our even best field theory hacks seemed to ... 04:10: ... atomic nucleus - not by modeling all the cogs and wheels of the field theory of the internal nucleus, but rather by understanding the observables ... 05:52: ... the S-matrix and his anti-reductionist philosophy and developed S-matrix theory. ... 06:47: Remember, that quantum field theory fastidiously adds together a complete set of virtual interactions that contribute to the real interaction. 06:56: ... theory sought to avoid this, and instead tries to model a scattering experiment ... 07:23: But in order to avoid those sums of Feynman diagrams, S-matrix theory also relies on symmetries between those virtual interactions. 08:28: In regular quantum field theory you’d need to add up all the different versions of both these two channels separately. 09:30: So S-matrix theory looked extremely promising … until it didn’t. 09:35: It presented severe challenges on par with those plaguing quantum field theory - and, as it happened, physicists solved the QFT challenges first. 10:10: ... the results was that S-matrix theory was sidelined, and quantum field theory reigns supreme to this day as ... 10:41: Quantum field theories like QCD surely gives us insights into the nature of the fundamental workings of the universe. 10:47: ... their astounding predictive success, S-matrix theory now seems less fundamental - it seems like an emergent set of ... 11:05: So I said that S-matrix theory got sidelined - that’s not exactly true. 11:35: ... so string theory was born - at first as a description of strong nuclear force ... 11:48: So our leading, and perhaps only current contender for a theory of everything was first derived as a bootstrap model, an S-matrix theory. 12:56: ... doesn’t just eliminate the fiddly mechanics of quantum field theory, it removes the very concepts of space and ... 16:28: But you should take all of this with a grain of salt; as rjw elsinga notes: there are a lot of holes in this theory 09:35: It presented severe challenges on par with those plaguing quantum field theory - and, as it happened, physicists solved the QFT challenges first. 10:47: ... like an emergent set of relationships - what we call an “effective” theory - but it turns out that it has led to deep insights that even quantum ... 06:47: Remember, that quantum field theory fastidiously adds together a complete set of virtual interactions that contribute to the real interaction. 03:50: ... and time should break down at those scales, and our even best field theory hacks seemed to ... 09:30: So S-matrix theory looked extremely promising … until it didn’t. 10:10: ... the results was that S-matrix theory was sidelined, and quantum field theory reigns supreme to this day as our reductionist description of the subatomic ... 06:56: ... theory sought to avoid this, and instead tries to model a scattering experiment - to ...
	2019-12-17: Do Black Holes Create New Universes? 03:48: The details of how this happens is presumably buried in the as-yet-unknown theory of quantum gravity. 04:27: Perhaps the configuration of the geometry string theory’s extra dimensions gets shifted - this would do the job. 10:33: Now perhaps the extra .17 can be factored into the uncertainties of the theory... 04:27: Perhaps the configuration of the geometry string theory’s extra dimensions gets shifted - this would do the job.
	2019-12-09: The Doomsday Argument 01:57: ... number of theories in physics from string theory to eternal inflation predict that the ...
	2019-12-02: Is The Universe Finite? 02:59: Albert Einstein’s general theory of relativity allows for three simple geometries for our universe. 12:12: If you want to dive deeply into understanding the building blocks of space time then you need to study quantum theory. 12:25: Honestly, the best way to wrap your head around quantum theory is to play with it. 12:30: ... of physics, and systems of measurement based on the algebra of quantum theory. ...
	2019-11-18: Can You Observe a Typical Universe? 17:37: If it can't be solved then we should ultimately dismiss the theory.
	2019-11-11: Does Life Need a Multiverse to Exist? 00:43: We can’t determine the values of these constants from pure theory - we have to measure them in the real universe. 01:02: ... the general theory of relativity and the standard model of particle physics, there are ... 01:24: Or perhaps they’re connected and controlled by some master dial or dials - whose nature awaits discovery in the long-sought theory of everything. 09:29: ... is, when we try to calculate the strength of this vacuum energy from our theory we get an enormous number - 10^60 to 10^120 larger than actually seems ... 11:24: ... example we have string theory: this candidate theory of everything suggests that the values of the ... 00:43: We can’t determine the values of these constants from pure theory - we have to measure them in the real universe.
	2019-11-04: Why We Might Be Alone in the Universe 12:30: A few of you wondered if there's a connection between the loops of loop quantum gravity and the closed strings of string theory. 12:39: The strings of string theory have a somewhat physical interpretation - the fact that they can hold energy and vibrate and exist in space. 13:48: And this was NOT observed in the light from a distant gamma ray burst, which presents a challenge for the theory.
	2019-10-21: Is Time Travel Impossible? 00:41: ... special and general theories of relativity changed the way we think about time forever, and believe ... 03:00: This is an example where the equations of a theory technically allow something to be true, but there’s still no good reason to believe that it is. 03:16: ... we still have the general theory of relativity, which incorporates special relativity, but also explains ... 11:36: ... actual fact we can’t know until we have a full theory of quantum gravity – until then we’re working with the approximate ... 11:47: Approximate theories can make bad predictions – like the possibility of time travel. 03:00: This is an example where the equations of a theory technically allow something to be true, but there’s still no good reason to believe that it is.
	2019-10-15: Loop Quantum Gravity Explained 00:06: And can it really defeat string theory in our quest for a Theory of Everything? 00:28: To connect quantum physics with Einstein’s general theory of relativity. 00:32: ... search for a theory of quantum gravity is a century old, and we’ve talked about it quite a ... 00:42: But string theory isn’t the only game in town - or so some physicists believe. 00:47: ... to reconcile the physics of the tiny and the gigantic - another way to a theory of quantum gravity that avoids a lot of conceptual baggage like tiny ... 01:46: ... mechanics, and indeed most theories in physics, involve a set of equations describing how stuff moves ... 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. 03:24: The challenge really gets us to the fundamentals of what a quantum theory actually is. 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. 05:13: A quantum theory of gravity needs to fix both of these issues - but we’re going to focus on background independence for now. 06:52: A contender for a theory of quantum gravity. 08:47: In this formalism, the “space of metrics” looks just like a space of fields in quantum field theory. 10:03: It’s general relativity – our modern theory of gravity – cast in terms of very abstract building blocks. 11:20: ... theory has some other successes, for example, the theory seems to predict ... 11:31: However there are also many who identify serious, fundamental issues the theory. 11:54: ... generally, for this theory to be successful it needs give you the equations of good old general ... 13:16: Loop quantum gravity is an intriguing alternative to the more popular string theory. 00:42: But string theory isn’t the only game in town - or so some physicists believe.
	2019-09-30: How Many Universes Are There? 07:20: People have also invoked the anthropic principle plus eternal inflation to explain a conundrum in string theory. 07:27: ... we’ve talked about before, modern string theory is difficult to pin down because there are countless possible ...
	2019-09-03: Is Earth's Magnetic Field Reversing? 05:21: And dynamo theory not only explains geomagnetism, but also why Earth’s field sometimes reverses its polarity.
	2019-08-19: What Happened Before the Big Bang? 00:43: These days, the best accepted description of the time before the Big Bang is given by inflation theory. 01:07: ... further back in time and explore a stunning implication of inflationary theory. ... 05:49: Now, the behavior of this field depends on some unverified physics But a suitable inflaton field fits with some grand unified theories. 05:59: Those are theories that combine the strong nuclear force with electromagnetic and weak forces. 06:04: As well as theories which also unify gravity, like string theory. 06:09: These theories predict phase transitions in the behavior of fields as the temperature of the universe changes. 06:23: Very flat potential energy slopes are also possible in these theories, enabling slow roll inflation or a combination of both. 06:32: ... more episodes, so, for now take my word for it that inflation fits some theory even if that theory is also entirely ... 10:04: ... are also deep possible connections between inflation and string theory and with the holographic principle, as described in one of Stephen ... 12:15: ... the standard Big Bang Theory doesn't explain the initial expansion at all, it includes an expansion ...
	2019-08-06: What Caused the Big Bang? 02:26: First up, the equations of Einstein's general theory of relativity. 02:31: Our modern theory of gravity can be used to predict the behavior of the universe as a whole. 04:42: We need some quantum physics. In fact, we need some quantum field theory.
	2019-07-18: Did Time Start at the Big Bang? 00:25: ... and Vesto Slipher, combined with Einstein's - then - brand-new general theory of relativity, revealed that our universe is expanding and if we reverse ... 01:22: ... keep changing their minds - they don't know anything", or "the Big Bang Theory is just a theory" Let me be very clear, the evidence for a hot dense ... 01:56: ... growth spurt solves a couple of the big problems with the Big Bang Theory, but it doesn't change the fact that Rewinding the expansion of the ... 08:14: ... Any time you encounter a singularity in the mathematics of a physical theory you have good reason for skepticism It's probably telling you that your ... 09:52: ... isn't anywhere near enough matter to do that unless we bring in string theory the Steinhardt-Turok model suggests that our universe floats in a higher ...
	2019-07-15: The Quantum Internet 01:00: To understand what needs to be done we need to get to the foundations of quantum mechanics - we need to talk about quantum information theory. 01:09: ... plain-old non-quantum information theory - the study of the creation, storage, and transmission of information, ... 01:21: ... Shannon started it all with his 1948 paper “A Mathematical Theory of Communication”, which quantified the rate of digital information that ... 01:37: ... theory has since blossomed into a full science, ultimately connecting the ... 01:49: Quantum information theory parallels classical information theory, but instead of using classical bits, it deals bits of quantum information - qubits. 01:09: ... plain-old non-quantum information theory - the study of the creation, storage, and transmission of information, ... 01:49: Quantum information theory parallels classical information theory, but instead of using classical bits, it deals bits of quantum information - qubits.
	2019-05-09: Why Quantum Computing Requires Quantum Cryptography 00:22: Quantum theory may seem like an obscure subject of questionable relevance to the average person. 13:23: Then we’ll also need a quantum internet … which we know how to do in theory, but it’s a different matter to actually build one.
	2019-05-01: The Real Science of the EHT Black Hole 08:55: ... the addition of the warped spacetime of a black hole using Einstein’s theory of general ... 10:17: ... the black hole looks just like we predict based on Einstein’s general theory of ...
	2019-04-24: No Dark Matter = Proof of Dark Matter? 00:03: ... to an unknown source of gravity but due to a failure of gravitational theory itself the first such proposal was Mons modified Newtonian dynamics ...
	2019-04-10: The Holographic Universe Explained 01:02: We’ve moved from quantum field theory to black hole thermodynamics to string theory. 04:06: ... laid out the first steps towards how this could be achieved using string theory, but ultimately it was Juan Maldacena who figured out a concrete string ... 04:26: Let’s ignore string theory for the moment and just think about how to create an extra dimension. 04:45: Those rules are a field theory, the lattice itself is the field, and the cells are some elementary component of the field. 05:08: Probably the rules between cells – the field theory – depends on this scale. 05:33: We’re going to say our field theory is scale-invariant. 05:53: We also see it in string theory, which I’ll come back to. 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. 07:42: But for the details we need string theory. 07:47: Even from the beginning string theory had hints of this scale invariance and dimensional weirdness. 07:54: ... first iteration of the theory, around 1970, tried to model the strong force between pairs of quarks – ... 08:44: This and other glitches led to string theory being abandoned as a model for the strong force. 08:49: ... it was quickly rejigged to make it a theory of quantum gravity, and the scale invariance of the strings becoming a ... 09:02: We now have a several versions string theory that try to explain how vibrating strings can lead to the familiar particles of this universe. 09:10: These were tentatively united by Ed Witten’s M-theory, which showed that different types of string and string theories were all related by dualities. 09:19: A duality is when two seemingly different theories prove to represent the same underlying physical reality. 09:52: Maldecena imagined a set of string theory objects called branes. 10:23: ... 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 ones that ... 10:49: It was also a conformal field theory – a CFT - so it was invariant to the scaling of grid sizes. 11:24: The conformal field theory in the original space included no gravity, but in the higher-dimensional space it became a full quantum theory of gravity. 11:38: As with the other dualities in string theory, this one was extremely useful for calculations. 11:46: ... interactions in the lower dimensional field theory are extremely strong – we would say the fields are strongly coupled - ... 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. 13:28: But those rules translate to interactions in the volume – in the bulk – and there they are a theory of gravity. 15:28: ... AdS/CFT correspondence, the volume exhibits gravity via a type of string theory, while the surface exhibits no gravity - only a quantum field theory ... 16:20: That surface contains only a conformal field theory and no gravity. 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. 09:52: Maldecena imagined a set of string theory objects called branes. 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.
	2019-04-03: The Edge of an Infinite Universe 02:29: At least the three basic types described by Einstein’s general theory of relativity. 07:16: Only lightspeed paths – or in the language of quantum field theory “massless fields” can access these diagonal boundaries. 14:04: ... realized that if you define a conformal quantum field theory in a 3+1-dimensional Minkowski space, that corresponded to an ... 14:20: That structure looked exactly like a string theory with gravity and everything. 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. 07:16: Only lightspeed paths – or in the language of quantum field theory “massless fields” can access these diagonal boundaries.
	2019-03-28: Could the Universe End by Tearing Apart Every Atom? 00:25: ... with the cosmological constant in the equations of Einstein's general theory of relativity but what if dark energy is not constant what if the energy ... 14:16: Sounds cool, but be cautious of theories that seem crafted to give happy endings. 14:28: I'm guessing the save the universe theories are more numerous than their plausibility warrants.
	2019-02-20: Secrets of the Cosmic Microwave Background 07:42: ... and that gives us the exact physical size that we expect from our theory from our standard ruler then that's a good indication that our universe ...
	2019-02-07: Sound Waves from the Beginning of Time 14:12: ... isn't a hard rule, it's a good guiding principle to be dubious of new theories that contradict extremely well tested old ... 14:33: Remember that things like general relativity and much of quantum field theory are verified to stunning precision. 14:39: If a new theory says, "Nuh-uh, that all wrong", it better be able to also explain how those theories appear to be so right while being wrong. 14:49: ... scientists sort through the overwhelming flood of poorly thought-out "theories" that they get bombarded with all the ...
	2019-01-30: Perpetual Motion From Negative Mass? 03:48: ... 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 to ... 05:47: ... of a much more complete description of gravity: Einstein’s general theory of ... 10:10: With this sort of highly speculative science, you really have to dig down and look at the assumptions in ALL of the theory. 12:23: I’m pretty sure that breaks quantum field theory as well as general relativity. 03:48: ... 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 to fields with ...
	2019-01-24: The Crisis in Cosmology 14:57: When a theory leads to these - sort of - pathological predictions, it's a big red flag. 17:42: Mr. Nation [?] has his own unified theory of the Dark Sector. 14:57: When a theory leads to these - sort of - pathological predictions, it's a big red flag.
	2019-01-16: Our Antimatter, Mirrored, Time-Reversed Universe 00:03: ... foundations of quantum theory rest on its symmetries for example it should be impossible to ... 02:02: ... 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 not ... 03:02: ... the 1950s was also the decade of the foundations of quantum field theory an SQFT emerged it became clear that there is a certain symmetry that's ... 13:52: ... version of Canada. The last episode before the break was, "Why string theory is Wrong". Today, I want to address the comments to that episode or ... 15:29: ... it provides an answer to the hierarchy problem and gives us super string theory it will be odd if supersymmetry existed as part of super string theory ... 16:06: ... other point is that the large undefined parameter space of string theory - the so called 'String landscape' is no more of a problem for string ... 16:49: ... FieldStrength's final point is that the untestability of string theory is connected to the extreme energy scale of quantum gravity and that ... 17:15: ... yeah string theory is apparently not yet testable, but I disagree with those who say that ... 16:06: ... other point is that the large undefined parameter space of string theory - the so called 'String landscape' is no more of a problem for string ... 03:02: ... theorem" in 1951 it became increasingly clear that quantum field theory demands symmetry under the combined action of charge conjugation parity ... 13:52: ... a neat resolution to the standard models hierarchy problem but string theory doesn't require supersymmetry to be at that scale at all for the purpose of ... 02:02: ... 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 not physics as ... 13:52: ... than very reasonable criticisms. In the video we note that string theory pretty much requires supersymmetry in order to be right and that supersymmetry ... 00:03: ... foundations of quantum theory rest on its symmetries for example it should be impossible to distinguish our ... 13:52: ... supersymmetry to be at that scale at all for the purpose of string theory supersymmetric particles could be far beyond the energies detected by the Large Hadron ... 03:02: ... is right at least as far as it goes it's just about the motor right theory we've ever come up with I'll get back to what this new time reversal symmetry ...
	2019-01-09: Are Dark Matter And Dark Energy The Same? 00:10: But perhaps one astronomer has just fixed it, with a theory that says perhaps actually they are they same stuff. 00:58: Farnes 2018, “A unifying theory of dark energy and dark matter: Negative masses and matter creation within a modified Lambda-CDM framework”. 01:08: As with any new theory combining dark matter and dark energy, probably it helps to know what they are first. 02:25: According to Einstein’s general theory of relativity, any such positive energy produces an inward-pulling gravity. 01:08: As with any new theory combining dark matter and dark energy, probably it helps to know what they are first.
	2018-12-20: Why String Theory is Wrong 00:07: There's this idea that beauty is a powerful guide to truth in the mathematics of physical theory. 00:13: String theory is certainly beautiful in the eyes of many physicists, but is it beautiful enough to pursue even if it's wrong? 00:35: Weyl had tried to explain electromagnetism by imposing on Einstein's general theory of relativity. 00:57: But sometimes it can be hard to let go of the sense that a beautiful theory must be right. 01:03: Could this also be the case with string theory? 01:06: ... particular case of a quantum string, which is part of what got string theory going in the first ... 01:18: We talked about this in detail in our episode on why string theory is right. 01:23: Which itself was a sequel to our primer on the basics of string theory. 01:27: In those episodes, we saw some of the remarkable ways that string theory promised to converge on a theory of everything. 01:35: ... umbrella, and there's also the convergence of many versions of string theory into a single picture with a very specific number of extra dimensions. ... 01:55: ... promise of being so right do more and more physicists think that string theory is after all either woefully incomplete or just plain ... 02:07: Modern string theory is the convergence of many beautiful ideas in physics, each of which feel right in their own way. 02:14: ... see where string theory ultimately fails, we need to rewind to look at some of these a bit ... 02:27: In 1919, not long after Einstein published his great theory of gravity, Theodor Kaluza discovered something strange. 03:37: Klein realized that you can get a sensible quantum theory if you compactify that extra dimension. 03:52: In the resulting in Kaluza–Klein theory, the fifth dimension is looped into a tiny circle. 04:36: Probably wrong, and it's not the only problem with the first version of Kaluza–Klein theory. 04:57: These may have seemed like fatal flaws, but we can thank this wrongness for the later development of string theory. 05:12: There are many Kaluza-Klein inspired theories out there. 05:16: String theory is just the most famous. 05:18: So, start with Kaluza-Klein, add vibrating strings and exactly the right extra special dimensions, and you have string theory. 05:40: It also introduces fermions to the boson only version of string theory to give super string theory. 06:03: Superstring started out with incredible promise, and so there was a proliferation of different versions of super string theory. 06:59: The various superstring theories exhibited what we call dualities. 07:04: A duality in physics is when two apparently different mathematical theories proved to represent the same physical process. 07:12: These dualities reveal that certain classes of string theory were actually the different ways of expressing exactly the same theory. 07:20: Perhaps there was a glimmer of hope for these divergent versions of string theory after all. 07:25: ... looks like, let's go back to the good old simplicity of Kaluza–Klein theory, or at least at the simplicity of just one extra circular spatial ... 09:07: ... you can construct a theory in which momentum increases with the size of the compact dimension, or ... 09:19: ... sounds weird but this may just have saved string theory. I just described a type of duality, in this case t-duality, short for ... 09:48: T-dualities prove that some of these different versions of string theory are actually different expressions of the same theory. 09:54: The other main type of duality in string theory is s-duality, strong-weak duality. 10:18: S-duality provided the final linchpin that demonstrated that the five different types of string theory were all manifestations of the same theory. 10:31: ... a string conference in '95, Witten showed that the disparate string theories were all just different perspectives, different limits or special cases ... 10:42: This was m-theory, where M stands for really what have you want it to: membrane, magic, mother theory. 10:51: ... to Witten is to be decided when the full nature of the theory is understood. We'll come back to M-theory in real detail, but the ... 11:08: So whereas the original superstring theories were ten dimensional with six compactified, M-theory is 11D, with seven hidden dimensions. 11:24: Whoa Well, that all sounds a bit arbitrary. Your theory not working? Just add an extra dimension. 11:32: Actually, the realization that superstring theory could be 11 dimensional was a revolution. It sparked the second superstring revolution. 11:41: See, in parallel to the development of super string theory, other physicists have been working on super gravity. 11:49: ... gravity should be the low energy, large-scale limit to super string theory. So it was incredibly exciting that string theory appeared to have an 11 ... 12:14: ... convergence of the superstring theories with each other and with super gravity restored the sense of beauty to ... 12:36: It's not solvable using perturbation theory, which doesn't leave much room to explore its implications. 12:43: In all superstring theories the extra spatial dimensions are wrapped, not in simple loops, but in complicated geometries called Calabi-Yau manifolds. 13:00: For example, sections of these manifolds that can be approximated as simple tubes, like in Kaluza-Klein line theory. 14:00: Essentially all string theories require supersymmetry in order to work. 14:16: But string theories are still rightly concerned. Their elegant theory which was converging so beautifully has stalled. 14:34: ... general relativity was wrong, but it inspired the entire field of gauge theory upon which much of our understanding of the quantum world ... 15:00: ... wrong or incomplete as current string theory may be, it may also be the inevitable early step as we seek an even more ... 15:14: ... the physics required to understand string theory is tough thankfully there are online tools that can help like brilliance ... 11:49: ... limit to super string theory. So it was incredibly exciting that string theory appeared to have an 11 dimensional version, M-theory, to correspond to everyone's ... 01:27: In those episodes, we saw some of the remarkable ways that string theory promised to converge on a theory of everything. 10:51: ... adds a single extra dimension, to connect all of the five super string theory types via ... 02:14: ... see where string theory ultimately fails, we need to rewind to look at some of these a bit closer, to start ...
	2018-12-12: Quantum Physics in a Mirror Universe 00:02: ... to seem heavily and yeah we'll be covering that after we do why string theory is wrong because you guys haven't stopped complaining that it isn't up ...
	2018-11-21: 'Oumuamua Is Not Aliens 15:28: Well, actually, modern string theory relies on supersymmetry so it's already included. 15:34: Was it called Ting theory before that? 15:37: Actually, the name string theory originally applied to what we call bosonic string theory. 15:51: The result is superstring theory. 15:53: And these days some form of superstring theory is implied when people talk about string theory. 15:37: Actually, the name string theory originally applied to what we call bosonic string theory. 15:28: Well, actually, modern string theory relies on supersymmetry so it's already included.
	2018-11-14: Supersymmetric Particle Found? 00:03: ... Hadron Collider running out of places to look for clues to a deeper theory of physics, we're going to need a bigger particle ... 00:28: Historically, no matter how crazy our theories got, there were always new ways to test them. 00:34: Your theory predicts a new particle. 01:02: There must be a more fundamental theory that explains the origin of this rich family of particles. 01:08: Proposals for such grand unified theories proliferate unconstrained by even the tiniest hint of new physics from the LHC. 01:17: One potentially very important ingredient for grand unification theories is supersymmetry. 01:30: ... extension to the standard model, designed to fix certain issues with the theory, the most serious issue being that the standard model can't explain the ... 02:08: It's a key feature in some grand unified theories as well as modern string theory, leveling it up to superstring theory. 12:33: ... below to subscribe to "Two Cents." Last week, we talked about why string theory is so compelling to so many ... 12:51: Many of you have some interestingly passionate hate for string theory on the grounds that it's so far proved unfalsifiable. 13:04: String theory may be wrong, but it's not testable due to the limits of current facilities. 13:25: The thing that makes string theory less sciencey is that its modern version, M-theory, is not particularly well-defined. 13:39: String theory is not precise enough yet to be confirmed wrong, which means it might be right or not. 14:24: So how can you get world sheets?" Yes, it is a pain keeping the number of dimensions straight in string theory. 14:47: So yeah, the math of string theory only works for 1D objects because these trace 2D world sheets. 15:32: But this has no bearing on the compactified extra dimensions of string theory. 16:06: And to end on a funny, Dash to the Max points out that string theory is literally like playing a sad song on the world's smallest violin. 16:16: And if it proves wrong in the end, at least we have the perfect instrument for a requiem to string theory. 02:08: It's a key feature in some grand unified theories as well as modern string theory, leveling it up to superstring theory. 00:34: Your theory predicts a new particle.
	2018-11-07: Why String Theory is Right 00:06: ... see string theory as the one great hope for a theory of everything that will unify quantum ... 00:20: Others see string theory as a catastrophic dead end, one that has consumed a generation of geniuses with nothing to show for it. 00:29: So why are some of the most brilliant physicists of the past 30-plus years so sure that string theory is right? 00:37: [MUSIC PLAYING] Why has string theory been the obsession of a generation of theoretical physicists? 00:59: ... short, the strings of string theory are literal strands and loops that vibrate with standing waves simply by ... 01:21: In this episode, I'm going tell you why string theory is right, at least why so many of those geniuses think it is. 01:52: I also want to give you a teaser on why string theory is actually wrong. 02:01: The greatest criticism of string theory is that it's never made a testable prediction. 02:06: ... space of possible versions of string theory is so vast that nothing can be calculated with certainty, so string ... 02:22: They might say, maybe half jokingly, that string theory does make one great prediction. 02:41: But the fact is when you start to work out the math of string theory, gravity appears like magic. 02:47: You don't need to try to fight gravity into string theory. 02:50: ... it will be difficult to remove it, and the quantum gravity of string theory is immune to the main difficulty in uniting general relativity with ... 03:07: ... did talk about this and other problems with developing a quantum theory of gravity in a recent episode, but before we get to the nuts and bolts ... 03:40: In quantum theories of gravity, the gravitational force is communicated by the graviton particle. 04:22: OK, let's switch to string theory where particles are not points. 05:06: ... illustrate why quantum gravity isn't hopelessly broken in string theory, and that's a huge point in favor of string theory, but these world ... 05:20: And this is the second point in string theory's favor. 05:22: ... out that tiny vibrating quantum strings automatically reproduce the theory of general relativity and, in the same mechanism, seem to promise to ... 05:39: This stuff appears a little too naturally in the math of string theory to be a coincidence, or so a string theorist might tell you. 06:36: A while ago, we talked about Paul Dirac developed a wave equation for the electron that took into account Einstein's special theory of relativity. 08:11: So, we expect the phase of the quantum wave function to be a gauge symmetry of any quantum theory. 09:02: ... turns out that exploring a very different symmetry of string theory both makes it possible to quantize the theory and gives us a very ... 09:14: So, like I was saying, when we try to quantize string theory, of course it's a huge mess. 09:43: Hermann Weyl actually came up with this symmetry right after Einstein proposed his general theory of relativity. 11:44: ... you use string theory to write down the gravitational field in what we call the low-energy ... 11:57: ... right particles, including the graviton and the photon, out of string theory for a very specific number of spatial dimensions, nine to be ... 12:11: In fact, if string theory makes any predictions, it's the existence of exactly this number of extra dimensions. 12:18: And this is where string theory starts to look less attractive. 12:25: ... that seems like a hell of an extra thing to add in order to make your theory ... 12:43: And that's just the first of many problems of string theory. 12:49: ... were lead to string theory by the elegance of the math and the fact that it appeared, at least in ... 12:58: ... convergence is also seen in the union of different string theories by M theory and in the discovery of AdS/CFT correspondence-- again, for ... 13:26: Perhaps we're now overly distracted by the elegance of string theory. 02:41: But the fact is when you start to work out the math of string theory, gravity appears like magic. 03:07: ... a recent episode, but before we get to the nuts and bolts of how string theory predicts gravity, it's worth taking a moment to see how stringy gravity avoids ... 05:06: ... string theory, but these world sheets will also help us see why string theory predicts gravity in the first ... 03:07: ... a recent episode, but before we get to the nuts and bolts of how string theory predicts gravity, it's worth taking a moment to see how stringy gravity avoids the problem ... 05:06: ... string theory, but these world sheets will also help us see why string theory predicts gravity in the first ... 12:18: And this is where string theory starts to look less attractive. 12:25: ... that seems like a hell of an extra thing to add in order to make your theory work. ... 05:20: And this is the second point in string theory's favor.
	2018-10-31: Are Virtual Particles A New Layer of Reality? 01:30: ... started out as a trick to make impossible calculations in quantum field theory possible-- possible, at least, for the sort of people who can do quantum ... 02:01: So quantum field theory is the machinery behind the standard model of particle physics. 02:57: That's where perturbation theory comes in. 04:58: ... diagrams are an absolutely essential tool in most modern quantum field theory calculations, but they also add to the misconception about virtual ... 12:08: ... of virtual particles came about as a calculation tool in perturbation theory as we tried to approximate the behavior of quantum ... 12:45: If they represent a physical reality, then there should be no way to do quantum field theory calculations without them. 12:53: It turns out there is a version of quantum field theory that doesn't use virtual particles at all. 12:59: That will be the family of lattice field theories in which space-time itself is defined on discrete grid. 13:05: It doesn't rely on perturbation theory, and so it doesn't use virtual particles while ultimately giving the same results. 04:58: ... diagrams are an absolutely essential tool in most modern quantum field theory calculations, but they also add to the misconception about virtual ... 12:45: If they represent a physical reality, then there should be no way to do quantum field theory calculations without them.
	2018-10-25: Will We Ever Find Alien Life? 13:18: Last week we dipped our toes into string theory. 13:38: Add it to string theory and you get superstring theory. 13:47: Now, the details are way beyond a comment response, but look into superstring theory and supersymmetry. 13:54: ... response to me saying that string theory has only one tunable parameter, Michael Murphy sarcastically points out ... 14:43: Korbus Barkly and some others ask whether, if string theory makes no testable predictions, shouldn't it be just called string hypothesis? 15:05: ... scientific theory is an explanation of an aspect of the natural world that can be ... 15:20: ... actually we've always used the word theory to mean-- again, quoting Dr. Diagrams-- some framework that, loosely ... 15:41: ... to put another way, in colloquial science speak, a scientific theory is a well-developed suite of ideas, laws, models, and predictive tools ... 16:01: ... no separate word for a theory that's not well-accepted, but there's still a huge difference between ... 16:13: A scientific theory is self-consistent and well-developed. 17:13: [INAUDIBLE] wonders why M theory is represented by five interlocking Pringles. 17:18: Well, rumor has it that Ed Witten came up with M theory while he was eating Pringles late one night. 17:25: He was struck by the potential of multi-dimensional Pringles to unify string theory.
	2018-10-18: What are the Strings in String Theory? 00:07: You may have heard the usual pop psy description of string theory. 01:10: So surely there exists a deeper set of cogs and wheels, a theory that brings all observable phenomena into the same mechanical framework. 01:20: That would be a theory of everything, and this is the great hope of string theory. 01:26: In the following episodes, we're going to explore the gory details of string theory. 01:32: But today it's String Theory 101. 01:45: What exactly are the strings of string theory? 01:48: First let's do a quick primer on the origins of string theory. 02:32: A lot of work went into figuring out a quantum theory for the strong interaction based on the physics of strings. 02:39: The theory had some success but kind of got stuck and was ultimately replaced by quantum chromodynamics. 02:46: ... of the reasons this strong force version of string theory got stuck is that it predicted the existence of unexpected and unwanted ... 03:45: What if the math of this theory could be used in a theory of quantum gravity? 04:20: This was so-called Bosonic string theory. 04:23: If it worked, it would have been a candidate for a grand unified theory combining all known forces. 04:48: ... resulting superstring theory sought to become an all-encompassing mechanism to explain the underlying ... 05:05: ... in 1995, Ed Witten brought the many forms of superstring theory together into the single framework of m-theory, all for the low price of ... 07:29: So this is the great promise of string theory. 07:47: It sure sounds closer to a fundamental theory. 08:51: These last properties are important because it gives a mechanism for the particles of string theory to interact and to decay into other particles. 09:00: This picture of strings coming together jointly and splitting apart is a huge strength of the theory. 09:31: String theory fixes this because the graviton is a loop, not a point particle. 10:13: In fact, the theory only works in precisely nine spatial dimensions, plus one for time, plus one for M theory, which we'll come back to. 10:34: It's a theory that works in a universe that is clearly not our own with its measly three dimensions of space. 11:37: Voila, string theory is saved. 11:40: Modern M theory proposes an additional large spatial dimension. 11:54: ... theory unites different string theories because it demonstrates some ... 12:19: In fact, the single free parameter in string theory becomes the configuration of the extra dimensions. 12:43: Right now string theory appears to be at an impasse. 13:08: In coming episodes, we'll look deeper into both the successes, the failures, and the profound weirdnesses of string theory. 01:32: But today it's String Theory 101. 12:43: Right now string theory appears to be at an impasse. 04:23: If it worked, it would have been a candidate for a grand unified theory combining all known forces. 09:31: String theory fixes this because the graviton is a loop, not a point particle. 11:40: Modern M theory proposes an additional large spatial dimension. 04:48: ... resulting superstring theory sought to become an all-encompassing mechanism to explain the underlying ... 11:54: ... theory unites different string theories because it demonstrates some philosophically ...
	2018-10-10: Computing a Universe Simulation 02:01: That includes most formulations of quantum mechanics and proposals for theories of everything. 13:57: Science works by forcification, and null results rule out huge chunks of theory space, greatly advancing our certainty.
	2018-10-03: How to Detect Extra Dimensions 05:15: Many would like to find a "theory of everything" which merges the forces of nature into the same über force. 06:15: They're used in string theory, where they typically have a large number of dimensions. 06:20: But in string theory, all but three spatial dimensions of the brane are inaccessible. 06:55: ... your theory just right, and you get normal physics for matter and radiation in three ... 07:59: ... on how you tweak the theory, gravity can obey an inverse square law on galactic scales, where it's ... 11:16: This ruled out or constrained various alternative theories to general relativity. 12:23: ... physics, exploring the conflicts between general relativity and quantum theory towards the development of a theory of quantum ... 12:47: Theories of quantum gravity go in both directions. 12:50: ... theories of everything try to quantize gravity by placing it within the same ... 13:00: These are grand unified theories. 13:02: And string theories are an example. 13:05: Other theories treat gravity very differently to the other forces. 13:22: If space-time is indefinitely divisible, then you get hopeless conflicts with quantum theory. 13:45: So when you use perturbation theory to calculate an interaction in field theories, feedback effects give infinite loops of interactions. 07:59: ... on how you tweak the theory, gravity can obey an inverse square law on galactic scales, where it's sort of ...
	2018-09-20: Quantum Gravity and the Hardest Problem in Physics 00:13: They must be united in a deeper, yet undiscovered, theory. 01:00: And yet these two theories contradict each other in fundamental ways. 01:12: ... begin our discussion of the great quest for this union, the quest for a theory of quantum gravity and for a theory of ... 01:41: General relativity, GR, is Einstein's great theory of gravity. 03:06: Nowadays, modern quantum field theories fully incorporate the melding of space and time predicted by special relativity. 03:44: That's a big conflict with quantum theory right there, which tells us that quantum information should never be destroyed. 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. 04:50: For that, you need a true quantum theory of gravity. 07:41: ... tells us that something is missing in our description of either quantum theory or general relativity, or both, at the smaller ... 07:54: Standard quantum theories treat the fabric of space-time as the underlying arena on which all the weird quantum stuff happens. 08:38: That leaves no clean coordinate system on which to ground your theory. 09:26: This type of self-interaction or self-energy is seen in other quantum field theories and is hard to deal with, even there. 09:42: In QED, the mess is fixed with something called perturbation theory. 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. 11:54: ... fabric of space-time itself are emergent phenomena from a quantum theory deeper than our currently accepted ... 12:08: That's exactly what string theory seeks to do. 12:11: ... to crack the greatest problem in modern physics, the quest for a theory of quantum ... 13:06: It'll really help us constrain some black hole 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. 11:54: ... fabric of space-time itself are emergent phenomena from a quantum theory deeper than our currently accepted ... 12:08: That's exactly what string theory seeks to do.
	2018-09-05: The Black Hole Entropy Enigma 00:40: At least they are inevitable according to the equations of Einstein's general theory of relativity. 00:46: That theory is one of the most thoroughly tested in all of physics, which means we should probably believe in black holes. 01:01: And yet if black holes exist, which apparently they do, they contradict other theories in physics that are as sacred as general relativity. 01:09: They cause all sorts of problems with quantum theory, which we've talked about before and we'll review in a sec. 01:30: ... an entire new way of thinking about the universe in terms of information theory and ultimately led to the holographic principle, which I promise we're ... 11:24: You just need to add a little bit of string theory. 11:34: It might also be true, and obviously we'll be back before too long to talk about string theory and the holographic nature of spacetime.
	2018-08-30: Is There Life on Mars? 05:10: Lowell wrote three books on the subject, the last presenting his full theory on the subject of life on Mars.
	2018-08-23: How Will the Universe End? 06:37: Theory says that if protons decay at all, this half-life could be up to 10 to the power of 37 years. 14:39: Dirac's theory, however, predicts exactly twice that value, g equals 2. 14:59: That's the classical theory, which is wrong-- and also suggested that electrons should spin faster than light. 16:36: We try to pull theory out or our-- out of nowhere to try to match to our observations, and we keep those theories that work. 16:44: But the key here is that we don't keep the theories if they only fit one observation.
	2018-08-15: Quantum Theory's Most Incredible Prediction 00:07: Let's talk about the best evidence we have to the theories of quantum physics truly represent the underlying workings of reality. 00:17: [MUSIC PLAYING] Quantum field theory is notoriously complicated, built from mind-bendingly abstract mathematics. 00:43: We know this because the predictions of quantum field theory stand up to experimental test time and time again. 00:50: Quantum field theory describes a universe filled with different quantum fields in which particles are excitations, quantized vibrations. 00:59: We've talked about QFT many times before, starting with the very first quantum field theory, quantum electrodynamics. 01:41: Well, because it makes some predictions that clash with the classical theory. 01:53: ... we're going to talk about the theory and experiments behind one of these tests, measuring the G factor, or in ... 03:32: As we'll see, their nature is predicted by quantum theory, measure electromagnetic moments, and you verify your quantum picture of reality. 06:23: Only the fully developed quantum electrodynamics, the first true quantum field theory, does this. 07:13: But in fact, we can calculate its effect extremely precisely and test this through experiments, showing the underlying truth of quantum theory. 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. 10:34: However, the ultimate arbiter of any physical theory is experiment. 12:04: ... those theories are good, they're able to predict things beyond the observations on ... 12:16: The theory of quantum electrodynamics has been pushed to the experimental limit and come out unscathed. 12:31: We have to conclude that we are getting closer and closer to the truth in our search for theories to explain the underlying mechanics of space time. 00:50: Quantum field theory describes a universe filled with different quantum fields in which particles are excitations, quantized vibrations. 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. 03:32: As we'll see, their nature is predicted by quantum theory, measure electromagnetic moments, and you verify your quantum picture of reality. 00:59: We've talked about QFT many times before, starting with the very first quantum field theory, quantum electrodynamics. 00:43: We know this because the predictions of quantum field theory stand up to experimental test time and time again.
	2018-07-25: Reversing Entropy with Maxwell's Demon 09:42: Claude Shannon, the father of information theory, was deeply inspired by the close connection between entropy and information.
	2018-07-18: The Misunderstood Nature of Entropy 00:54: ... thermodynamics that encapsulates the second law is the only physical theory of universal content which I am convinced will never be overthrown." And ... 01:45: In 1824, Sadi Carnot published his "Reflections on the Motive Power of Fire," in which he revealed the theory for perfect engine efficiency. 03:46: ... mechanics, founded by the great Ludwig Boltzmann with his kinetic theory of ... 03:57: This theory explained thermodynamic behavior as the summed result of the individual motion of tiny particles under Newton's laws of motion. 11:11: Stunningly, its foundations are in probability theory. 03:57: This theory explained thermodynamic behavior as the summed result of the individual motion of tiny particles under Newton's laws of motion.
	2018-07-11: Quantum Invariance & The Origin of The Standard Model 00:03: ... model of particle physics is the most successful, most accurate physical theory ever developed, describing with stunning accuracy the fundamental ... 01:07: To appreciate the theoretical whirlwind that is the standard model, we need to introduce the idea of a gauge theory. 01:14: ... simple terms, a gauge theory is one that has mathematical parameters or degrees of freedom that can ... 01:57: But it turns out that these gauge symmetries are an important feature of most of our physical theories describing the universe. 02:16: A theory that has these gauge symmetries is called a gauge theory. 02:24: The standard model is ultimately based on quantum field theory, but we're going to use the Schrodinger equation. 10:49: And following those mathematical labyrinths reveals physical theory with stunning predictive power, like the standard model of particle physics.
	2018-07-04: Will A New Neutrino Change The Standard Model? 10:17: ... in our understanding of physics, and glitches between experiment and theory are exactly how new physics gets ...
	2018-06-20: The Black Hole Information Paradox 00:17: It may very well be the loose thread that leads to a theory of everything. 03:59: ... is in severe violation of one of the foundational tenets of quantum theory. ... 04:18: After all, without a theory of quantum gravity, Hawking had to hack both general relativity and quantum-field theory to do the calculation. 04:41: ... turns out that if we assume that both general activity and quantum-field theory are correct as we currently understand them, then Hawking radiation must ... 05:08: A deeper understanding of general relativity or of quantum-field theory must resolve this. 05:27: ... a slight modification of general relativity called Einstein-Cartan theory, it's predicted that the formation of a rotating black hole gives birth ... 09:39: Leonard Susskind formalized this idea in the context of string theory in what we now know as the holographic principle. 11:11: ... me how one little loose thread, a seemingly insignificant quirk in the theory, can lead to massive discoveries and complete reframing of ... 11:22: ... the nature of information and entropy, exploded the field of string theory, and hinted at the possible holographic nature of ... 11:44: Einstein's general theory of relativity reveals them to be regions of frozen time and cascading space. 12:45: Last week we talked about the no-hair theory of black holes, and you all had some hairy questions. 14:01: But quantum-field theory imagines the electromagnetic force as being transmitted by virtual photons.
	2018-06-13: What Survives Inside A Black Hole? 03:24: In Einstein's general theory of relativity, we think of the gravitational field as curvature in the fabric of spacetime. 12:18: ... particle creation and annihilation is described by quantum-field theory, and unitary evolution and the conservation of probability and ...
	2018-05-23: Why Quantum Information is Never Destroyed 05:51: ... of quantum mechanics, like the Dirac equation and quantum field theories. ... 06:02: That guarantee arises from a really fundamental foundational quality of these theories. 06:49: And this unitarity is a foundational assumption in all formulations of quantum mechanics and quantum field theories. 09:14: ... for example, Everett's many-worlds or the de Broglie-Bohm pilot wave theory preserve this time ... 09:35: And in the case of pilot wave theory, the wave function contains hidden information that is carried with the final measured particle. 09:14: ... for example, Everett's many-worlds or the de Broglie-Bohm pilot wave theory preserve this time ...
	2018-05-16: Noether's Theorem and The Symmetries of Reality 01:03: When it was published in 1915, Einstein's general theory of relativity opened as many questions as it answered. 08:22: The entire standard model of particle physics is what we call a gauge theory.
	2018-04-25: Black Hole Swarms 11:11: Well, to answer that, I'd need a theory of quantum gravity so let me get back to you.
	2018-04-18: Using Stars to See Gravitational Waves 08:40: ... Einstein was able to derive his general theory of relativity, which predicted the existence of gravitational waves, he ... 08:51: He needed to understand Newton's theory of gravity well enough to see where it failed.
	2018-04-04: The Unruh Effect 08:36: ... they perform the relativistic field theory calculation to understand the coupling between the detector particle and ...
	2018-03-15: Hawking Radiation 00:20: He made profound contributions across physics from quantum theory to cosmology. 00:34: ... PLAYING] Soon after Einstein revealed his great general theory of relativity in 1915, physicists realized that it allowed for the ... 01:07: Once formed, there was nothing in theory or imagination that could bring material consumed back to the outside universe. 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 ... 04:35: To answer that properly, he would need a full union of general relativity and quantum mechanics, a theory of quantum gravity, a theory of everything. 06:14: In the absence of a theory of quantum gravity, Hawking needed a hack. 11:13: Without a full quantum theory of gravity, the origin of Hawking radiation will remain mysterious.
	2018-02-14: What is Energy? 08:50: ... to complex interactions of particles and fields in quantum field theories. ... 09:26: And the Lagrangian quantum field theory is the basis for high-energy particle physics. 10:53: ... of energy is generally invalid in the context of Einstein's general theory of relativity due to the potential time evolution of ...
	2018-01-24: The End of the Habitable Zone 13:03: ... when we're covering topics from topology to cryptography to number theory. ...
	2018-01-17: Horizon Radiation 00:00: ... PLAYING] The most successful theory in physics combines the weirdness of quantum mechanics with, well, the ... 00:12: This theory tells us that particles can be created and destroyed during interactions. 00:26: [MUSIC PLAYING] Both theories of relativity, special and general, tell us that many things are observer dependent. 02:22: ... 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 ... 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. 06:59: Now it starts out with no oscillations, analogous to the vacuum state in quantum field theory. 08:42: There's a nice mechanism in quantum field theory for doing this. 00:12: This theory tells us that particles can be created and destroyed during interactions.
	2017-12-06: Understanding the Uncertainty Principle with Quantum Fourier Series 10:12: So what does this old-school quantum mechanics have to do with quantum field theory and Hawking radiation?
	2017-11-22: Suicide Space Robots 12:00: You say that quantum field theory makes no prediction about the energy of the vacuum. 12:20: ... current, beyond standard model theory, has a lot of trouble explaining why it produces the tiny energy density ...
	2017-11-08: Zero-Point Energy Demystified 00:32: ... is the prediction of quantum field theory, that there exists an energy of the vacuum resulting from the non-zero ... 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. 01:26: This means we should take the idea of zero-point energy seriously and are justifiably perplexed at the mismatch between theory and measurements.
	2017-11-02: The Vacuum Catastrophe 00:03: The most successful theory in all of physics is arguably quantum field theory. 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. 03:24: Until we develop a theory of quantum gravity, we can't say whether the photons above this energy are possible. 03:49: ... if it were infinite-- we may not notice, at least according to quantum theory. ... 04:39: Long story short-- a crazily high, even infinite, vacuum energy doesn't affect the predictions of quantum field theory. 04:57: Einstein's theory tells us that any form of energy produces gravity, and what matters is the absolute amount of energy, not relative deviations. 05:37: ... that, if vacuum energy really did have the enormous value predicted by theory, then our gently expanding geometrically flat universe would not ... 05:53: ... realization of this fact in the early days of quantum field theory was the beginning of what would become the vacuum catastrophe, but it ... 06:46: But perhaps a yet deeper theory allows perfect canceling down to 0. 07:39: Compare that to the number predicted by quantum field theory. 08:56: But of course, it may be that advances in theory will resolve this catastrophe without requiring us to invoke the anthropic principle. 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. 04:57: Einstein's theory tells us that any form of energy produces gravity, and what matters is the absolute amount of energy, not relative deviations.
	2017-10-25: The Missing Mass Mystery 02:56: There's a huge discrepancy between the amount of baryonic matter our surveys find and the amount that our theories say should be out there. 03:06: And those theories are pretty solid. 05:50: And yet, when we add up the mass from those galaxies, most of the baryonic matter predicted by a theory is missing. 12:55: Eliran Cohen suggests that, instead of presenting lame theories, we should travel 1,000 years into the future and bring back exact answers. 13:08: Unfortunately, there's still no theory of everything in 1,000 years and still not flying cars, would you believe? 13:17: Maybe we'll at least get some evidence for the string theory or something.
	2017-10-19: The Nature of Nothing 01:55: Our modern understanding of the quantum nature of space is described by quantum field theory. 02:57: In fact, the math of quantum field theory is all about going up and down this particle ladder, using so-called creation and annihilation operators. 04:20: ... interactions in the universe, at least as described by quantum field theory. ... 07:26: According to the best existing theory of the time, those orbitals should have had exactly the same energy. 09:32: ... drawn together by a force that matched the predictions of quantum field theory. ... 10:44: This crazy discrepancy between theory and observation is considered by some to be one of the greatest unsolved mysteries in physics. 10:53: ... field theory, with its dependence on virtual particles and vacuum fluctuations, is one ... 11:18: ... episode, we'll look deeper into this perplexing mismatch between our theory and our observation of the behavior of nothing and what it might tell us ...
	2017-10-11: Absolute Cold 04:40: In theory, absolute zero temperature means no thermal energy so no internal motion of particles whatsoever.
	2017-10-04: When Quasars Collide STJC 11:17: These are like the tunable knobs of the theory. 11:24: And presumably a deeper theory explains this, and may connect to them. 11:29: In this theory, the value of some constants may prove to be tied to the values of other constants. 11:24: And presumably a deeper theory explains this, and may connect to them.
	2017-09-28: Are the Fundamental Constants Changing? 01:21: The answer lies in a deeper underlying theory, a so-called grand unified theory. 01:28: But some proposed grand unified theories predict something unsettling. 01:41: Now, we're not going to get into the nitty gritty of the theory today. 02:13: It's been suggested that a changing speed of light might be an alternative to inflation theory, or even to the apparent expansion of the universe. 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. 09:38: Well, any measurement of a change in Alpha may provide evidence to constrain the grand unified theories that predict such changes. 11:45: ... speaking of grand unified theories, I wanted to give a special shout out to Don Lincoln's excellent series, ... 01:41: Now, we're not going to get into the nitty gritty of the theory today.
	2017-09-13: Neutron Stars Collide in New LIGO Signal? 15:42: And Hot Fuzz is obviously a reference to black hole singularities in string theory.
	2017-08-30: White Holes 00:37: ... the idea first emerged from Einstein's general theory of relativity, physicists wondered how seriously to take this ... 02:31: ... a few months after Einstein published his general theory of relativity, Karl Schwarzschild solved its equations for a very ...
	2017-08-10: The One-Electron Universe 04:58: In a quantum field theory that's consistent with Einstein's special relativity, all particles must be symmetric under what we call CPT transformation. 06:22: ... as time-reversed matter is extremely useful in simplifying quantum field theory calculations, because it massively cuts down the number of Feynman ...
	2017-07-26: The Secrets of Feynman Diagrams 01:51: Then, you are going to apply them to do some quantum field theory yourself. 02:02: The first and most predictively powerful quantum field theory, QED, talks about the interaction of the electron field with the electromagnetic field. 10:02: ... diagrams an incredibly powerful tool in simplifying quantum field theory calculations, vastly reducing the number of contributing interactions ... 02:02: The first and most predictively powerful quantum field theory, QED, talks about the interaction of the electron field with the electromagnetic field.
	2017-07-19: The Real Star Wars 14:40: ... about tricks for solving the impossible equations of quantum field theory. ...
	2017-07-12: Solving the Impossible in Quantum Field Theory 00:06: Quantum field theory is stunningly successful at describing the smallest scales of reality, but its equations are also stunningly complex. 00:27: ... PLAYING] The equations of quantum field theory allow us to calculate the behavior of subatomic particles by expressing ... 00:42: ... even the most elegant and complete formulations of quantum field theory, like the Dirac equation or Feynman's path integral, become impossibly ... 01:26: ... give you an idea of how messy quantum field theory can be, let's look at what should be a simple phenomenon-- electron ... 01:58: But in quantum field theory, specifically quantum electrodynamics, or QED, the story is very different. 03:08: ... pictorial tools to organize the painful mathematics of quantum field theory, but they also serve to give a general idea of what these interactions ... 06:07: This is the philosophy behind perturbation theory, an absolutely essential tool to solving quantum field theory problems. 08:09: Perturbation theory, with the help of Feynman diagrams, make the calculation possible, but that doesn't mean we're done. 09:27: The answer probably lies within a theory of quantum gravity which we don't yet have. 09:33: But just as with perturbation theory, physicists found a cunning trick to get around this mathematical inconvenience. 10:27: ... be used to eliminate many of the infinities that arise in quantum field theory-- for example, the infinite shielding of electric charge due to virtual ... 10:51: That means the theory can't predict that particular property from scratch. 11:01: Nonetheless, renormalization saved quantum field theory from this plague of infinities. 11:26: ... Feynman's doodles an incredibly powerful tool for using quantum field theory to predict the behavior of the subatomic ... 12:07: The two-episode documentary "The Ultimate Formula" gives a really nice history of the development of quantum field theory. 13:12: Last week, we talked about Richard Feynman's brilliant contribution to the development of quantum field theory with his path integral formulation. 09:33: But just as with perturbation theory, physicists found a cunning trick to get around this mathematical inconvenience. 06:07: This is the philosophy behind perturbation theory, an absolutely essential tool to solving quantum field theory problems.
	2017-07-07: Feynman's Infinite Quantum Paths 01:03: You might also want to catch up on the first two in our quantum field theory playlist because we are going to be building on that. 02:53: But it led to the most elegant formulation of quantum mechanics ever devised and became a key to quantum field theory. 08:16: That means it treats space and time symmetrically and so works very naturally with Einstein's theory of special relativity. 08:42: But perhaps the greatest power of the path integral is that it very naturally converts into a true quantum field theory. 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? 15:00: A few of you asked whether quantum field theory and string theory are the same thing. 15:07: Quantum field theory describes particles as a field vibration in 4D space-time. 15:16: String theory states that all particles are different vibrational modes in one-dimensional objects called strings. 15:30: ... stunning success and is the foundation of the standard model, string theory is untested and may have nothing to do with ... 15:07: Quantum field theory describes particles as a field vibration in 4D space-time. 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. 15:16: String theory states that all particles are different vibrational modes in one-dimensional objects called strings.
	2017-06-28: The First Quantum Field Theory 00:17: I'm talking about quantum electrodynamics-- the first true quantum field theory. 00:24: [MUSIC PLAYING] Quantum mechanics is perhaps the most unintuitive theory ever devised. 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 ... 08:21: He named the resulting theory quantum electrodynamics. 09:37: It is one of the most carefully tested theories in all of physics. 10:10: No other theory in physics has done so well. 11:10: This is the postulate of quantum field theory. 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. 12:45: ... between quantum mechanics and relativity, check out the course, The Theory of Everything, by Professor Don Lincoln from Fermi ... 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. 14:26: ... special and general relativistic corrections tend to introduce into the theory. ... 01:18: ... Field Theory, QFT, describes all elementary particles as vibrational modes in fundamental ... 08:21: He named the resulting theory quantum electrodynamics.
	2017-06-21: Anti-Matter and Quantum Relativity 00:16: Einstein's theory of special and general relativity had changed forever the way we think about motion, space, and time. 00:31: Yet, this year, 1928, one brilliant insight would bring these theories together and unveil the quantum fabric of reality. 05:27: Instead of having a two-component spinor, up and down, as in Pauli's theory, he needed four components. 09:02: Now, quantum field theory is a very deep topic. 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 particle physics, which ...
	2017-06-07: Supervoids vs Colliding Universes! 08:44: A popular version of inflation theory is that of eternal inflation. 09:30: And it could happen frequently or rarely, depending on the completely unknown details of the string theory parameter space.
	2017-05-31: The Fate of the First Stars 03:40: And this brings us to the leading theory as to the mysterious disappearance of population three.
	2017-04-26: Are You a Boltzmann Brain? 00:40: His most incredible insight was the kinetic theory of gases.
	2017-02-02: The Geometry of Causality 00:05: The special theory of relativity tells us that one person's past may be another's future. 00:15: ... we peer deeper into Einstein's theory to find that the immutable ordering of cause and effect emerges when we ... 01:04: First, let's recap a little bit of Einstein's special theory of relativity. 12:07: ... the mathematical singularity at the center of black holes is with string theory, which proposes that particles that we see in regular 4D spacetime result ... 12:47: Mathematician Georg Cantor invented set theory, the mathematics we use to study different types of infinity.
	2017-01-19: The Phantom Singularity 03:20: But the reality of the black hole singularity may give reason to doubt the theory that predicts such a thing. 03:29: ... physical singularity, and we've been forced to reject the corresponding theory. ... 04:16: ... Newton's law gives the wrong answers, and we need Einstein's general theory of relativity, which is the far more complete theory of ... 11:19: Actually, Einstein's theory and the Schwarzschild solution that is derived from it suggests it must exist. 11:34: ... better understand why the central infinity is unavoidable in Einstein's theory, we have to go back to that coordinate shift at the event ...
	2017-01-11: The EM Drive: Fact or Fantasy? 06:49: So the last part of the paper talks about a connection between the EmDrive and pilot wave theory. 06:56: This isn't something we can get into properly without first doing some quantum field theory, so I'll keep it brief. 07:02: The paper invokes pilot wave theory as a way to justify treating the quantum vacuum as a sort of plasma with which it can exchange momentum. 07:12: However, it's highly speculative and isn't necessarily even an obvious outcome of pilot wave theory. 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. 07:59: Instead, they invoke pilot wave theory to justify treating the quantum vacuum as a deformable medium. 08:29: ... than described by the otherwise amazingly successful quantum field theory. ... 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.
	2017-01-04: How to See Black Holes + Kugelblitz Challenge Answer 00:07: We tend to be pretty theoretical in how we think of them, partly because the theory predicts some fun stuff that no human will likely ever experience. 04:41: ... powerful tests of whether they behave as predicted by Einstein's general theory of relativity or whether there are tantalizing ... 00:07: We tend to be pretty theoretical in how we think of them, partly because the theory predicts some fun stuff that no human will likely ever experience.
	2016-12-08: What Happens at the Event Horizon? 01:07: ... hole rotational growth, the simplest black hole of Einstein's general theory of relativity-- purely gravitational, static, and eternal-- is a subtle ... 13:47: Onto the comments from last week's episode on De Broglie-Bohm theory. 14:02: Now, a lot of you wondered why I never mentioned the EM drive when talking about pilot wave theory. 14:14: ... produced by their EM drive and then go on to talk about how pilot wave theory might explain the apparent conservation of momentum-breaking ... 14:30: I might get into the details in an upcoming episode, but for the sake of explaining pilot wave theory this paper isn't relevant. 14:38: ... is extremely speculative, and honestly I wondered whether pilot wave theory was chosen partly because the internet happens to love it at the ... 14:50: ... asks how it can be that pilot wave theory predicts different particle trajectories, given that the particles ... 15:11: ... pilot wave theory states that the particle riding the wave does have a definite position ... 15:51: More generally, it allows pilot wave theory to agree with Heisenberg's uncertainty principle. 16:05: ... Broglie-Bohm pilot wave theory states that this uncertainty just arises from our imperfect knowledge ... 17:15: ... entirely accurate when I said that De Broglie, the founder of pilot wave theory, remained convinced by Niels Bohr and his Copenhagen camp, even after ... 18:08: ... version of what was to be a much more intricate double solution theory in which the so-called particle was actually a matter wave itself ... 18:34: ... Broglie never completed his full double solution theory, but did work on it intermittently throughout his life and was inspired ... 18:57: ... De Broglie-Bohm pilot wave theory is a great example of how a deterministic theory can at least go some ... 19:17: I like the idea of a deterministic theory, but the universe has often demonstrated that it couldn't care less about our pet theories. 19:36: We'll figure this out, and until then it's OK to like one theory over another but belief should wait on the evidence. 14:50: ... asks how it can be that pilot wave theory predicts different particle trajectories, given that the particles supposedly all ... 17:15: ... entirely accurate when I said that De Broglie, the founder of pilot wave theory, remained convinced by Niels Bohr and his Copenhagen camp, even after Bohm's ... 15:11: ... pilot wave theory states that the particle riding the wave does have a definite position at all ... 16:05: ... Broglie-Bohm pilot wave theory states that this uncertainty just arises from our imperfect knowledge and that ...
	2016-11-30: Pilot Wave Theory and Quantum Realism 00:16: It's the de Broglie-Bohm pilot-wave theory. 00:19: And despite its alluringly intuitive nature, for some reason it remains a fringe theory. 00:26: ... hoo-ha and unfounded mystical storytelling of any scientific theory. ... 01:26: That's de Broglie-Bohm pilot-wave theory. 01:30: ... theory, also known as Bohmian mechanics, stands in striking contrast to the much ... 01:47: Pilot-wave theory is perhaps the most solidly physical, even mundane, of the complete and self-consistent interpretations of quantum mechanics. 02:16: ... quantum theory was coming together in the '20s, they were fervent about the need to ... 03:11: ... to counter Bohr and Heisenberg there needed to be a full theory that described how a quantum object could show both wave and ... 03:25: ... theory came from Louis de Broglie, the guy who originally proposed the idea ... 03:36: De Broglie's theory reasoned that there was no need for quantum objects to transition in a mystical way between non-real waves and real particles. 03:51: This is pilot-wave theory. 04:05: Importantly, the wave function in pilot-wave theory evolves exactly according to the Schrodinger equation. 04:21: This means that pilot-wave theory makes the same basic predictions as any other breed of quantum mechanics. 05:18: When de Broglie presented his still-incomplete theory at the famous Solvay Conference of 1927, it didn't go down so well. 05:56: Bohm took up where de Broglie left off and completed the theory. 06:00: The result was Bohmian mechanics, also known as de Broglie-Bohm pilot-wave theory. 06:21: See, although pilot-wave theory makes all of the usual predictions of quantum mechanics, it has some really fundamental differences. 06:54: So what uncomfortable thinking does pilot-wave theory require? 07:51: According to pilot-wave theory, the wave function just describes the possible distribution of those variables given our lack of perfect knowledge. 08:18: That proclamation contributed to the long shelving of pilot-wave theory. 08:57: This helped the resuscitation of pilot-wave theory, because Bohmian mechanics doesn't use local hidden variables-- its hidden variables are global. 10:40: I should probably also add that de Broglie-Bohm pilot-wave theory is certainly wrong. 10:56: While regular mechanics has quantum field theory as its relativistic version, pilot-wave theory hasn't quite got there yet. 11:05: Quantum field theory pretty explicitly requires that all possible particle trajectories be considered equally real. 11:13: Pilot-wave theory postulates that the particle really takes a single actual trajectory, the Bohm trajectory. 11:21: This is not consistent with quantum field theory, and so there isn't a complete relativistic formulation of Bohmian mechanics yet. 11:41: Also, we can't ignore the fact that the initial motivation behind pilot-wave theory was to preserve the idea of real particles. 11:55: ... that said, pilot-wave theory does do something remarkable-- it shows us that it's possible to have a ... 04:05: Importantly, the wave function in pilot-wave theory evolves exactly according to the Schrodinger equation. 11:13: Pilot-wave theory postulates that the particle really takes a single actual trajectory, the Bohm trajectory. 11:05: Quantum field theory pretty explicitly requires that all possible particle trajectories be considered equally real. 03:36: De Broglie's theory reasoned that there was no need for quantum objects to transition in a mystical way between non-real waves and real particles. 06:54: So what uncomfortable thinking does pilot-wave theory require?
	2016-11-16: Strange Stars 00:55: Einstein's general theory of relativity tells us that the core of a dead star must collapse under its own incredible weight. 01:02: What happens to the resulting ultra-dense material depends on quantum theory. 12:50: A lot of you asked for a video on De Brogile-Bohm pilot wave theory. 13:09: ... the black hole information paradox, Hawking radiation, some string theory, the holographic principle, other ...
	2016-10-26: The Many Worlds of the Quantum Multiverse 06:00: ... was proposed by Hugh Everett in his 1957 PhD thesis entitled "The Theory of the Universal Wave Function." It's come to be known as the many ...
	2016-09-29: Life on Europa? 09:57: ... observable difference between the predictions of a local hidden variable theory versus pure quantum mechanics is if you measure the spins of both ... 10:17: ... the local hidden variable theory, you'd expect to sometimes measure spins in the same direction, depending ... 09:57: ... observable difference between the predictions of a local hidden variable theory versus pure quantum mechanics is if you measure the spins of both particles ...
	2016-09-21: Quantum Entanglement and the Great Bohr-Einstein Debate 09:40: That sounds blasphemous to anyone who accepts Einstein's theory of relativity. 10:53: Also, the De Broglie-Bohm Pilot Wave Theory works by assuming real and non-local hidden variables.
	2016-08-10: How the Quantum Eraser Rewrites the Past 08:27: ... interpretation of the wave function, like the De Broglie-Bohm Pilot Wave Theory, requires an underlying physicality, a set of defined properties that ...
	2016-07-27: The Quantum Experiment that Broke Reality 09:36: ... theory of quantum mechanics produces stunningly accurate predictions of reality ... 09:54: ... know that light is a wave in the electromagnetic field and quantum field theory tells us that all fundamental particles are waves in their own ...
	2016-07-20: The Future of Gravitational Waves 04:07: Beyond the detection of gravitational waves, this is another awesome validation of the theory.
	2016-07-06: Juno to Reveal Jupiter's Violent Past 10:28: We recently talked about the origin of quantum theory with Max Planck's derivation of an equation to describe the black body spectrum.
	2016-06-15: The Strange Universe of Gravitational Lensing 01:27: ... general theory of relativity describes the real universe as a flexible, dynamic ... 02:33: The deflection angle was exactly what Einstein's theory predicted. 12:02: ... de Broglie-Bohm pilot wave theory, the many-worlds interpretation, and others, allow a deterministic ... 02:33: The deflection angle was exactly what Einstein's theory predicted.
	2016-06-01: Is Quantum Tunneling Faster than Light? 00:12: [THEME MUSIC] Quantum mechanics is a spectacularly weird theory. 01:26: This is one of the early realizations in the development of quantum theory. 10:15: Throw in some string theory and black holes and a really unique writing style and it's a very insightful Pop Sci book.
	2016-05-18: Anti-gravity and the True Nature of Dark Energy 00:19: ... you to take a wild ride with me into the heart of Einstein's general theory of relativity and its description of the vaster of scales of our ...
	2016-04-27: What Does Dark Energy Really Do? 00:16: ... how the fate of the universe can be described using Einstein's general theory of relativity via the Friedmann ... 11:45: ... when the theory-- general relativity, in this case-- is so thoroughly verified in so many ...
	2016-04-20: Why the Universe Needs Dark Energy 00:08: ... strange influence called "dark energy." [THEME MUSIC] Einstein's general theory of relativity allows us to describe the behavior of the cosmos on the ... 00:35: ... attempts to constrain the predictions of this theory with real astronomical observations tell us that the fate of the ...
	2016-04-13: Will the Universe Expand Forever? 00:12: Yet the fact that Einstein's theory allows us to learn the answer to this question is incredible. 00:19: ... MUSIC] Soon after Albert Einstein proposed his general theory of relativity, industrious physicists-- and, in particular, a brilliant ...
	2016-03-23: How Cosmic Inflation Flattened the Universe 00:15: [MUSIC PLAYING] The Big Bang theory describes the earliest epochs of our universe amazingly well. 06:57: ... the field equations of his general theory of relativity, he added this as a way to allow his theory to describe a ... 09:13: With inflation, the Big Bang theory takes on new meaning. 00:15: [MUSIC PLAYING] The Big Bang theory describes the earliest epochs of our universe amazingly well. 09:13: With inflation, the Big Bang theory takes on new meaning.
	2016-03-16: Why is the Earth Round and the Milky Way Flat? 11:04: In our recent episode, we talked about some of the outstanding issues in the Big Bang Theory.
	2016-03-09: Cosmic Microwave Background Challenge 00:05: ... been talking about the Big Bang theory a lot recently, and the most important piece of evidence for this theory ...
	2016-03-02: What’s Wrong With the Big Bang Theory? 00:10: The Big Bang Theory suggests that once the entire universe was compacted into an infinitely small speck at the beginning of time. 00:22: What parts of this theory are still under serious question? 00:26: [MUSIC PLAYING] In the last episode, I showed you why the Big Bang Theory is right, or at least, what parts of it pretty much definitely happened. 01:06: ... of physics, and in particular running the math of Einstein's general theory of relativity ... 02:46: Our theories look really good to that point. 03:11: ... we call these grand unified theories, except they aren't theories in the same sense as relativity or evolution ... 04:26: And we need a theory of quantum gravity, a so-called theory of everything, to go further. 04:31: ... can talk about why these theories don't play nice together and what some of the resolutions might be-- ... 07:47: The theory that describes this pow is called inflation. 08:31: ... fact, inflation solves a number of vexing problems with the Big Bang Theory so well, in fact that most cosmologists accept that something like this ... 08:56: ... this sense, it may be more accurate to think of the Big Bang Theory not as a theory of the origin of the universe, but instead as a theory ... 09:09: Aspects of this theory have such hard evidence that we know that the basic picture is right. 09:15: However, as with every really well-established theory, there are boundaries to what the Big Bang Theory currently explains. 09:28: Perhaps the theory will eventually encompass a true origin for this universe. 12:16: So it's unfortunate that this statement is used to deride the Big Bang Theory. 12:36: Perhaps our understanding of this state will eventually lead to a theory of the origin of the universe. 12:42: But the Big Bang Theory as it stands does not claim to explain such an origin. 08:56: ... Theory not as a theory of the origin of the universe, but instead as a theory describing the period of expansion from a subatomic to a cosmic ... 00:10: The Big Bang Theory suggests that once the entire universe was compacted into an infinitely small speck at the beginning of time.
	2016-02-24: Why the Big Bang Definitely Happened 00:11: ... PLAYING] The Big Bang theory was pretty contentious when it was first proposed, as is any picture of ... 00:27: ... these days, there's really no doubt that at some level, the Big Bang theory gives an accurate description of the earliest epochs of this ... 00:43: Today, we're going to talk about the evidence that gives us so much certainty for parts of the theory. 00:55: I'm not going to spend a lot of time describing the theory. 01:04: ... Big Bang theory is a set of descriptions detailing the expansion of the universe from a ... 01:28: Some of these experiments have verified certain parts of the theory beyond reasonable doubt, while other parts remain untested. 01:50: ... the context of Einstein's theory of general relativity, the only sensible interpretation for this fact is ... 04:49: So at least that far back in time, the Big Bang theory is right. 06:29: ... the Big Bang theory is right, then those ripples should have been frozen into the ... 07:15: ... Big Bang theory tells us how long these elements were baked and at what temperature, and ... 07:31: The Big Bang theory has powerful, direct evidence, almost down to the first second. 08:55: Brendon Binns asks, given this detection, is the "theory" of general relativity still just a theory? 09:02: Well, actually, it's even more solidly a theory than ever. 09:06: In science, when we say theory, we mean a description of reality that has stood up to many, many experiments. 09:15: We only call it a theory if we're pretty much certain that the basic picture is correct. 09:21: Theories actually contain laws, and those laws are often the most well-established parts of a theory. 09:28: A theory may still have parts that aren't so well established, but such uncertainties don't invalidate the overall picture. 09:38: If they did, then we wouldn't be calling it a theory. 07:15: ... Big Bang theory tells us how long these elements were baked and at what temperature, and so ...
	2016-02-11: LIGO's First Detection of Gravitational Waves! 00:17: ... existence of these waves is the last major prediction of Einstein's theory of general relativity to be directly verified a century after the theory ... 04:57: See, gravitational waves are inevitable if the theory is correct. 05:22: ... significantly from the expected signal, then it may be a clue that the theory is incomplete, or even point to a new, deeper ... 05:37: However, physicists will be all over this data, looking for holes in the theory for some time.
	2016-02-03: Will Mars or Venus Kill You First? 10:11: For one thing, we don't have a theory of quantum gravity to get us into the Planck era.
	2016-01-27: The Origin of Matter and Time 00:00: [MUSIC PLAYING] Einstein's theory of special relativity has shown us mass and time are not the concrete things we imagine them to be.
	2016-01-20: The Photon Clock Challenge 00:35: And the resulting slowing of clock ticks due to motion is the time dilation of Einstein's theory of special relativity.
	2015-12-16: The Higgs Mechanism Explained 01:01: To understand how all this works, we're going to need to learn a bit of quantum field theory. 01:54: Now, this is a very simplistic explanation of a theory that has produced an astoundingly accurate description of the subatomic universe. 02:02: ... its incredible success, it was strange that quantum field theory, as it stood in the 1950s, gave a perfect description of the electron, ... 06:04: Well, something like this must be true, because all of the rest of quantum field theory hangs together too well. 06:11: We conclude that QFT is essentially correct, but it's an incomplete theory without a mass-giving field. 06:04: Well, something like this must be true, because all of the rest of quantum field theory hangs together too well.
	2015-12-09: How to Build a Black Hole 03:15: ... 6D quantum phase space depends on two important principles of quantum theory, the Pauli exclusion principle and the Heisenberg uncertainty ... 10:34: Of course, a real black hole is not the static creature that we sometimes describe in theory.
	2015-11-25: 100 Years of Relativity + Challenge Winners! 00:24: ... this day in 1915, Albert Einstein first presented his complete theory of general relativity to the Prussian Academy of Sciences in Berlin, ... 00:36: ... we cover a lot of material on this show, but Einstein's beautiful theory is an essential part of what inspires us here at "Space Time." General ... 01:01: The elegance of this theory has inspired so many students of physics to follow in Einstein's path exploring the mysteries of the universe.
	2015-11-18: 5 Ways to Stop a Killer Asteroid 10:19: Well first let me note that Panspermia is far from being an accepted theory.
	2015-10-28: Is The Alcubierre Warp Drive Possible? 00:45: ... constructed a warp field in the mathematical language of Einstein's theory of general relativity, a real solution to the equations of GR that would ... 04:13: It suggests that there's something in the deeper union of GR and quantum mechanics, the theory of everything, that prohibits the warp drive. 08:36: ... doubt that Max Planck and Schrodinger and Bohr imagined that this crazy theory would lead to the invention of the transistor, a quantum mechanical ...
	2015-10-22: Have Gravitational Waves Been Discovered?!? 00:03: Gravitational waves are the last prediction of Einstein's Theory of General Relativity. 00:22: It has a lot to do with his revolutionary Theory of General Relativity, in which he showed us that the force of gravity is an illusion.
	2015-10-07: The Speed of Light is NOT About Light 02:11: By the late 1800s, we have Maxwell's equations, Newton's mechanics, various other awesome theories. 09:19: ... of the meaning of the Lorentz transformation gives us the special theory of relativity-- time dilation, length contraction, and, of course, mass ...
	2015-09-30: What Happens At The Edge Of The Universe? 07:07: In addition, although general relativity is pretty cool, it's not a theory of everything. 07:36: ... and others ask whether it's contradictory or circular to use Einstein's theory of general relativity to prove ... 07:47: Well, the only way to test a theory is to use it. 07:54: A model has to make multiple independent and accurate predictions to be accepted as a theory. 07:58: And there are few theories with as many independent and accurate predictions as general relativity.
	2015-09-23: Does Dark Matter BREAK Physics? 04:21: Any replacement theory has to reproduce all, and I mean all, of the verified predictions of Einstein's theory and be able to explain dark matter. 06:46: ... in short, versions of this theory predict the existence of a set of counterparts to the familiar standard ... 06:58: Sinking down into the depths of quantum field and string theory, you can find all sorts of strange fish, WIMPs, axions, neutralinos. 06:46: ... in short, versions of this theory predict the existence of a set of counterparts to the familiar standard model ...
	2015-08-19: Do Events Inside Black Holes Happen? 00:24: That means no Hawking radiation, no string theory, and no quantum anything-- baby steps.
	2015-08-05: What Physics Teachers Get Wrong About Tides! 10:09: ... may have heard that in quantum field theory, forces are described as being mediated by some kind of particle like ... 10:44: ... can quantize any classical theory, as long as you are restricting yourself to looking at macroscopic ... 10:53: ... or very high energies, that a lot of infinities start popping up in the theory that you can't get rid of, which is what we don't have a fully ... 11:07: But from the philosophical perspective of quantum field theory, you should be able to quantize anything. 11:26: You can look up something called Kaluza-Klein theory, which is a way of trying to get a geometric version of electromagnetism plus general relativity. 11:41: ... the other is to try to take field-- classical field theory versions of something and then add to them the machinery of quantum ... 10:09: ... may have heard that in quantum field theory, forces are described as being mediated by some kind of particle like ... 11:41: ... the other is to try to take field-- classical field theory versions of something and then add to them the machinery of quantum mechanics to ...
	2015-07-29: General Relativity & Curved Spacetime Explained! 08:32: ... even when people are referring to relativity or string theory or whatever, it's just a lot easier to say the word gravity than say ...
	2015-06-03: Is Gravity An Illusion? 09:19: It makes several predictions that Newton's theory of gravity does not, and so far, it has passed all its experimental tests.

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