
20221116: Are there Undiscovered Elements Beyond The Periodic Table?
 10:56: It turns out there are no simple set of principles to determine nuclear stability.
 16:52: eliyah zayin has a thoughtful criticism of the use of the Copernican principle to argue that we can’t especially early in the universe.


20221109: What If Humanity Is Among The First Spacefaring Civilizations?
 01:14: ... we have this thing called the Copernican principle, which states that we shouldn’t expect to find ourselves in a ...
 01:34: But in principle you can extend this principle to time.
 01:46: ... course the Copernican principle has to compete with the Anthropic principle, which states that we can ...
 02:43: ... hear more about the anthropic and copernican principles, and how we can use them to calculate other surprising things about our ...


20221026: Why Did Quantum Entanglement Win the Nobel Prize in Physics?
 17:10: In principle you could look at planets in other galaxies.


20221019: The Equation That Explains (Nearly) Everything!
 03:07: ... all possible due to an extremely powerful concept in physics called the Principle of Least Action, which we’ve talked about in detail. It says that Nature ...
 04:05: ... then the Lagrangian will have that symmetry too. And by applying the principle of least action to a Lagrangian with a continuous symmetry will reveal ...


20221012: The REAL Possibility of Mapping Alien Planets!
 19:23: ... the Planck constant or the speed of light change? In principle, maybe, but the most natural thing to change is the ratio of ...


20220824: What Makes The Strong Force Strong?
 03:29: This restriction is known as the Pauli Exclusion Principle.
 03:58: ... be something different in order for them to comply with the Exclusion Principle. ...


20220622: Is Interstellar Travel Impossible?
 02:57: But there are proposed advanced forms of propulsion that could in principle accelerate a proper spacecraft to a fair fraction of the speed of light.
 13:42: But it turns out there’s nothing in principle stopping us from slowly limping from one planetary system to the next.
 18:11: ... that emerge from a black hole as Hawking radiation, could we in principle learn about the inside of the black hole, given that they are entangled ...
 18:31: ...  if hawking radiation really is entangled with the black hole then in principle we can learn about the black hole interior by measuring ...


20220615: Can Wormholes Solve The Black Hole Information Paradox?
 00:26: ... quantum information, and even to the holographic principle. Now, the latest attempt to solve the black hole ...
 06:01: ... mentioned that the information paradox inspired the holographic principle. The most advanced form of this is AdS/CFT ...


20220601: What If Physics IS NOT Describing Reality?
 04:05: ... quantum indeterminacy, entanglement, and the uncertainty principle turn out to be the expected behaviors of this sort of information ...
 08:49: ... other staples of quantum theory  like the Heisenberg uncertainty principle. In a previous episode we saw how the uncertainty principle arises ...


20220504: Space DOES NOT Expand Everywhere
 11:22: ... of a black hole. Its solution takes us to the realm of the holographic principle, and so we can’t go there today. But long story short  even with a ...


20220420: Does the Universe Create Itself?
 07:08: ... was called the delayed choice experiment because, in principle, the second beamsplitter could be put in place only after the photons ...
 09:48: ... Take this yet further and you have a version of the Strong Anthropic Principle: The only reality that can exist is one that can have observers whose ...


20220323: Where Is The Center of The Universe?
 00:37: Ever since then, astronomers have embraced the Copernican principle, which states that we are NOT in a special place in the universe.
 00:51: And the Copernican principle inspired another important idea  not only are we not the center of the universe, but the universe doesn’t have a center.
 01:04: This is called the Cosmological principle.
 01:06: ... neither the Copernican principle nor the Cosmological principle are actual laws of physics  they’re ...
 11:28: He assumed a homogeneous universe and assumed the cosmological principle.
 12:47: ... should point out that this doesn’t necessarily break the Cosmological principle because it could still be that our bubble is small on the most ...


20220308: Is the Proxima System Our Best Hope For Another Earth?
 11:43: ... thick atmosphere and strong planetary magnetic field could in principle protect any surface dwellers, who would then get to enjoy pretty ...
 19:37: ... the relative phase angle can in principle be measured  that is, we can see the difference in the phase ...


20220216: Is The Wave Function The Building Block of Reality?
 02:24: ... function collapse was first proposed by Werner Heisenberg, one of the principle founders of quantum theory. Heisenberg and his friend Neils Bohr were ...


20220127: How Does Gravity Escape A Black Hole?
 09:03: We have to be able to “see” that mass, at least in principle.


20220112: How To Simulate The Universe With DFT
 06:59: ... for the other particles, for example through the Pauli exclusion principle and through quantum ...
 17:05: ... for looking for impact evidence on the Moon  yes, in principle these impacts leave weirdshaped craters that we might be able to ...


20211220: What Happens If A Black Hole Hits Earth?
 14:26: ... made as simple as possible, but no simpler” Occam’s razor is a guiding principle, not a rule. If the current model can’t be made to fit observation then ...
 16:33: ... be taken seriously, fuzzballs need to satisfy the equivalence principle  the founding idea of general relativity that says that freefall in a ...
 17:30: ... is related to AdS/CFT correspondence and the holographic principle, which we covered previously. It, says that vibrations in a quantum field ...


20211210: 2021 End of Year AMA!
 00:02: ... defined momentum and as we know from the heisenberg uncertainty principle if a particle has perfectly defined position perfectly defined ...


20211117: Are Black Holes Actually Fuzzballs?
 02:45: But in the case of air, the hidden information still exists and is, in principle, still measurable.


20211110: What If Our Understanding of Gravity Is Wrong?
 08:15: ... we saw that the principle of least action allows equations of motion to be extracted in a ...
 15:36: Our last episode was all about the principle of least action, and how this one simple idea sort of leads to all of physics.
 17:26: That was right  but I then went on to call this a “principle of least proper time” by analogy to the principle of least action.
 17:39: ... consistent with the whole action thing because the proper name is the principle of stationary action  and the maximum is also a stationary point  of ...
 17:55: Many of you point out that you’re already adherents of the principle of least action.


20211102: Is ACTION The Most Fundamental Property in Physics?
 00:02: ... them, it follows the shortest one. He proposed what you might call a Principle of Least Distance to define the path of light. Of course we now know ...
 01:15: It seemed as if we’d stumbled on a powerful guiding pattern in nature  minimizing principles.
 01:59: ... systems. So maybe we were still in the market for a simple guiding principle after ...
 02:11: ... was JosephLouis Lagrange who found that principle. Consider again the ball flying through the air. We can describe that ...
 03:33: ... in such a way that Action is always minimized. And so was discovered the Principle of Least Action. A century later William Hamilton made the important ...
 04:29: ... the principle of Least Action is true, then it should be possible to figure out the ...
 05:24: ... Principle of Least Action is so powerful that it really seems like it must be ...
 05:52: ... you get the right answer. But you don’t even need to go that far. If the Principle of Least Action is really a fundamental law, then there should be a ...
 07:09: ... shows us that the Principle of Least Action holds up in GR  but it reveals a lot more. First, it ...
 08:06: ... that light always travels the path that minimizes its travel time  the principle of least time. Well it turns out that this is just a special case of a ...
 09:24: ... there seems to be a conflict here. The principle of least action says that a particle will always land where the action ...
 11:12: ... no coincidence, because the path integral is the quantum analog of the Principle of Least ...
 12:59: ... application of the quantum action principle to the evolution through quantum states underpins modern quantum theory. ...
 13:46: ... a path through the configuration space of ideas, guided by mysterious principles, not least of which is the Action  pointing the surest way to the ...
 14:57: ... a huge shoutout to our Quasar supporter Michael Schneider. Hamilton's principle tells us that action must always be minimized or maximized. Michael, ...
 15:58: ... theory does try to bring a philosophical perspective shift, which in principle can be incredibly useful. All great discoveries came from perspective ...


20211020: Will Constructor Theory REWRITE Physics?
 02:40: ... and quantum mechanics, along with more fundamental conservation laws, or principles, to rule out impossible output states given an input state of a ...
 03:11: ... David Deutsch says, if a quantum computer can, in principle, simulate any process in physics, then all of physics can be expressed in ...
 05:44: Again, this task is impossible, since it’s ruled out by the laws of quantum mechanics and the principle of conservation of energy.
 08:52: You have two qubits, which could in principle be entangled with each other.
 10:42: ... the inevitable implications of simple statements like the equivalence principle and the invariance of the speed of ...


20211005: Why Magnetic Monopoles SHOULD Exist
 04:18: But in principle it could exist, and so could magnetic monopoles.
 14:55: ... it  for example all the structure of solids, via the Pauli exclusion principle. ...
 16:22: ... the structural support against collapse produced by the Pauli exclusion principle  is ...
 16:42: So the answer is that the Pauli exclusion principle is never violated.


20210921: How Electron Spin Makes Matter Possible
 00:26: ... doesn’t immediately collapse. It’s the source of the Pauli exclusion principle, and today I’m going to show you exactly why this simple property makes ...
 02:18: ... nonoverlapability of fermions is called the Pauli exclusion principle. I’m going to show you why this is the inevitable behavior of groups of ...
 07:22: ... we need to get to the spinstatistics theorem, and the Pauli exclusion principle. Now all we need is to do is the ...
 13:03: ... spinors having antisymmetric wavefunctions, is the pauli exclusion principle. That is, particles with half integer spin have antisymmetric ...
 14:00: ... have an antisymmetric wavefunction and so must obey the Pauli exclusion principle  or you get ...


20210818: How Vacuum Decay Would Destroy The Universe
 04:42: ... Heisenberg uncertainty principle tells us that there’s a fundamental uncertainty in  ...


20210810: How to Communicate Across the Quantum Multiverse
 01:29: ... independently of each other due to something called the superposition principle. This principle also applies to the wavefunction in quantum ...
 01:46: ... wavefunction corresponding to our “world”, and due to the superposition principle our world can happily do its thing unperturbed by other parts of the ...
 04:30: ... through each other without being scrambled is due to the superposition principle. Let’s dig a little deeper. This principle says that you can determine ...
 05:54: ...  and a linear wave equation is what you need for the superposition principle to be ...
 06:09: ... in the physical world the superposition principle only holds to a point. Real pond surfaces or air density fields don’t ...
 06:28: ... mechanics it’s always assumed that linearity and the superposition principle hold. Stack wavefunctions on top of each other and they behave as though ...
 07:14: ...  they would exist across the entire wavefunction. And that, in principle, could give a way to explore what happens to the wavefunction after ...
 08:55: ... tell us how to do this  he only proves that it should be possible in principle. ...


20210803: How An Extreme New Star Could Change All Cosmology
 06:21: ... forbidden by quantum mechanics  specifically, by the Pauli exclusion principle, which tells us that particles in the fermion family, like elelectrons, ...
 15:19: ... just pass through the wall is something else  it’s the Pauli Exclusion principle, which says that electrons in atoms can’t be shoved into each other to ...


20210713: Where Are The Worlds In Many Worlds?
 01:44: Here, we’re seeing the principle of superposition in action.
 01:47: ... wave mechanics, this principle tells us that when two waves overlap, their amplitude  in this case the ...
 01:58: But the superposition principle also tells us something much cooler.
 02:43: The superposition principle only applies up to a point.
 02:46: If the amplitude of the waves is is too high, the principle can break down.
 02:58: At the risk of getting technical, the superposition principle holds for any linear system  and I’ll say more about that another time.
 03:13: But the superposition principle seems to always hold for the waves that drive quantum mechanics.


20210707: Electrons DO NOT Spin
 10:51: And by Heisenberg's uncertainty principle increasing your knowledge of one, means increasing the unknowability of the other.
 13:00: ... behavior of fermions manifested as the Pauli Exclusion Principle and is responsible for us having a periodic table, for electrons ...
 14:32: ... it represents the information contained in the system and extractable in principle, versus information that’s lost to the system by entanglement with ...


20210616: Can Space Be Infinitely Divided?
 03:47: ... going  we’re about to discover the Heisenberg uncertainty principle. Bare with me though with just a touch of ...
 04:49: ... the Heisenberg microscope. We now know that the uncertainty principle is far more fundamental than just the effect of disturbing ...
 05:08: ... point I want to focus on today is that through the uncertainty principle we see that the Planck constant represents the limit to ...
 08:37: ... down as much as possible. But the Heisenberg uncertainty principle says that when we do that we increase the uncertainty ...
 09:58: ... on the Planck scale. At that scale, Heisenberg’s principle tells us that the curvature of space is fundamentally ...


20210525: What If (Tiny) Black Holes Are Everywhere?
 11:17: ... yet, and then the one on how to mess with the limits of the uncertainty principle in detecting gravitational ...
 13:36: ... onto the episode where we looked at how the Heisenberg uncertainty principle can be gamed to improve measurements  in particular in gravitational ...
 15:08: ... our title from last week  we called it “Breaking the Uncertainty Principle”, but you rightly  if pedantically  pointed out that it should have been ...


20210519: Breaking The Heisenberg Uncertainty Principle
 00:07: And in some cases succeeding, by squeezing the Heisenberg uncertainty principle to its breaking point.
 00:47: ... absolute quantum limit  the limit defined by the Heisenberg Uncertainty Principle. ...
 01:05: Today we’re going to see how the uncertainty principle can be hacked to make measurements more precisely than should ever be possible.
 01:13: ... Heisenberg uncertainty principle tells us that there exists a fundamental unknowability to nature  an ...
 01:41: ... these pairs of properties complementary variables, and the uncertainty principle tells us that the uncertainties in our knowledge of such a pair, when ...
 01:58: Werner Heisenberg discovered the uncertainty principle when he was inventing his version of quantum mechanics back in the 1920s.
 02:05: That version is called matrix mechanics, but we get the same uncertainty principle using the wave mechanics of Schrodinger.
 02:13: ... it  so to get an idea of the fundamental source of the uncertainty principle, you can watch our episode on how it comes about from thinking about ...
 02:56: Basically, he thought the uncertainty principle arose as a result of the measurement disturbing the system.
 03:13: He thought the uncertainty principle was hinting at a far more fundamental law of the universe.
 03:18: ... viewed it as an example of a principle of reality that he called “complementarity.” Bohr developed this ...
 04:10: The Heisenberg uncertainty principle prevents us from being able to know everything about a quantum state all at once.
 04:23: Remember, the uncertainty principle places a lower limit on the product of the uncertainties of pairs of complementary properties.
 04:30: ... for example, if we only care about a particle’s position we can in principle measure it to extreme precision as long as we’re happy to have no ...
 04:47: ... us to manipulate quantum states to push the limits of the uncertainty principle. ...
 06:21: And this is where the uncertainty principle comes in.
 06:53: Unless we can hack the uncertainty principle.
 07:25: ... light from a laser beam obeys the Heisenberg uncertainty principle in a very specific way—it has equal amounts of uncertainty in its two ...
 07:35: ... circle is proportional to Planck’s constant, satisfying the uncertainty principle. ...
 10:03: ... have demonstrated this same principle in other systems like entangled atomic clocks, which may one day ...
 10:17: ... bend a few fundamental laws  in this case, the Heisenberg uncertainty principle  we can push the limit beyond what we thought possible to force ever ...


20210421: The NEW Warp Drive Possibilities
 17:32: ... now I see it’s an ancient viking metaphor for the Heisenberg uncertainty principle. ...


20210323: Zeno's Paradox & The Quantum Zeno Effect
 05:23: ... in principle this would also work for radioactive decay, even chemical reactions The ...


20210316: The NEW Crisis in Cosmology
 15:19: ... Smith Noted that the Huygen's Principle seems eerily similar to the double slit experiment if ...
 16:28: ... Feynman connection also  pointing out the Huygen's principle feels like Feynman's path integral formulation of quantum ...


20210309: How Does Gravity Affect Light?
 02:09: In general relativity, the best place to start is always the equivalence principle.
 03:29: ... equivalence principle tells us that we must experience all the same physics if at rest in a ...
 05:13: Let’s start with the goodold equivalence principle again, and a spaceship attacked by giant alien spiders.
 05:48: And the equivalence principle tells us we must see the same bending of the light ray in our stationary rocketship set in our gravitational field.
 07:35: A big part of that was his Huygens or HuygensFresnel Principle.
 09:17: ... a very classical, 17thcentury style plane wave so you can use Huygens' principle. ...
 10:47: And even if this change in velocity isn’t “real”, it’s enough to let us use Huygen’s principle.


20210224: Does Time Cause Gravity?
 00:34: ... the same as that induced by gravity  the socalled equivalence principle. ...


20210217: Gravitational Wave Background Discovered?
 00:00: ... and the ceiling right that's a subtlety that i skipped the equivalence principle is technically only true in a uniform gravitational field so if the ...


20210210: How Does Gravity Warp the Flow of Time?
 00:25: ... gravitational field does not exist.” We now know this as the equivalence principle  it states that there’s no experiment that you can do to distinguish a ...
 05:45: To get to gravitational time dilation all we need to do is add in the equivalence principle as our second axiom.
 08:54: The equivalence principle demands that there’s no experiment that can distinguish between acceleration and gravity.


20210126: Is Dark Matter Made of Particles?
 15:11: ... accelerate again to turn around, and according to Einstein’s equivalence principle, acceleration is fundamentally the same as gravitation as far as the laws ...


20201222: Navigating with Quantum Entanglement
 04:52: In principle it’s easy to come up with ways to sense a magnetic field.


20201208: Why Do You Remember The Past But Not The Future?
 05:01: ... you perfectly retrace its past.a In that idealized scenario, could in principle trace the jiggling of its internal quarks backwards to learn when the ...
 07:33: If the rock never interacts with any external influence and just decays over time, then in principle we could calculate that decay.


20201118: The Arrow of Time and How to Reverse It
 11:16: ... fuel for our choices.. Now if those random numbers are not even in principle learnable by some snooping entity, then it doesn’t matter whether they ...


20201111: Can Free Will be Saved in a Deterministic Universe?
 02:46: One of the most important rules of quantum mechanics is the principle of conservation of quantum information.
 04:23: ... new thread of quantum information, in violation with the conservation principle, or two, that this information just not be predictable even in principle ...
 07:52: It's also impossible in principle.
 08:05: ... is a direct consequence of the Heisenberg uncertainty principle, which tells us that measuring one property perfectly leaves a ...
 08:16: ... brain or of the information threads that go into making it, either in principle or in practice, because unknown random processes are at work, and/or ...
 12:06: ... it's not even in principle possible to perfectly predict a brain's choices, and that brain feels ...


20201020: Is The Future Predetermined By Quantum Mechanics?
 04:15: At least as far as the Heisenberg Uncertainty Principle allows.


20200928: Solving Quantum Cryptography
 09:40: The principle behind McEliece is that it’s really difficult to repair errors in large messages.


20200908: The Truth About Beauty in Physics
 05:07: This is connected to the principle of parsimony, also known as Occam’s Razor.


20200824: Can Future Colliders Break the Standard Model?
 15:40: In principle there should be a point right at the center where there is no flow  if you were a pointlike particle you could just hang there.


20200810: Theory of Everything Controversies: Livestream
 00:00: ... towards the big bang or in the center of black holes but also in principle every time we bring a particle into a superposition of two locations ...


20200728: What is a Theory of Everything: Livestream
 00:00: ... of interests including string theory and loop quantum gravity in principle we could do this entire conversation just with stefan he's worked in ...


20200708: Does Antimatter Explain Why There's Something Rather Than Nothing?
 04:05: ... could actually counteract CP violation, preserving CPT symmetry. In principle, at least. If CPT symmetry really IS violated however it may explain why ...


20200511: How Luminiferous Aether Led to Relativity
 00:31: ... science like this “it seems probable that most of the grand underlying principles have been firmly established and that further advances are to be sought ...


20200428: Space Time Livestream: Ask Matt Anything
 00:00: ... the exterior of the black hole is what started the whole holographic principle which leonard susskind then came in and gave a full sort of string ...


20200422: Will Wormholes Allow Fast Interstellar Travel?
 12:51: ... may fluctuate wildly, its form shifting due to Heisenberg’s uncertainty principle. The result is what we call the spacetime foam, and it may imply that ...


20200407: How We Know The Earth Is Ancient
 04:32: ... several in our solar system. Astronomers now swear by the Copernican principle  Earth is not in a privileged position in the universe, and so the laws ...
 07:17: ... it takes for half of a large number of radioactive nuclei to decay. In principle, if you know how much of the stuff there was to start with you can figure ...


20200331: What’s On The Other Side Of A Black Hole?
 12:02: ... only occur between two particles. What you're thinking about is the principle of monogamy of entanglement, which states that a given quantum state can ...


20200324: How Black Holes Spin Space Time
 10:27: ... way the rotational energy can be extracted with, in principle, 100% efficiency. Oh, and you can also build a black hole bomb this way  ...


20200224: How Decoherence Splits The Quantum Multiverse
 06:28: In principle we can bring those parts of the wavefunction back together to cause interference.


20200203: Are there Infinite Versions of You?
 06:39: ... in principle there is an allowable level of ridiculously tiny deviation in the ...


20200120: Solving the Three Body Problem
 00:20: ... of the bodies of the solar system, Newton’s equations could be used in principle be used to calculate their locations at any distant time, future or ...
 12:21: ... which successive terms diminished to effectively nothing, so in principle the equation could be written out on paper. However the convergence of ...


20200106: How To Detect a Neutrino
 04:46: ... energy conservation by taking advantage of the Heisenberg uncertainty principle, ♪ ♪ which tells us that there's a fundamental uncertainty ♪ ♪ between ...


20191217: Do Black Holes Create New Universes?
 00:42: In recent episodes we explored one possible explanation for this  the anthropic principle and the idea of the multiverse.
 01:02: But if you don’t like the anthropic principle  and many scientists don’t  then rest assured, there’s an alternative.
 08:37: But, whoopsie, I just invoked the anthropic principle, which is exactly what were trying to avoid with this whole idea.
 10:59: ... tries to avoid the anthropic principle by proposing a natural selection that favours black hole production, and ...


20191209: The Doomsday Argument
 00:25: ... some recent episodes we’ve explored the anthropic principle and seen how it can be used to explain the fact that both our planet and ...
 00:47: We touched on both the potential power and potential misuse of this principle.
 01:03: To use the anthropic principle properly we need to use it carefully.
 01:07: ... talked about weaving in the Copernican principle which tells us that, all else being equal, we should expect to be in a ...
 01:16: This is seemingly the opposite notion to the Anthropic principle.
 02:33: ... is a good candidate for the anthropic principle  perhaps we’re just in one of the lucky universes with a low ...
 04:15: ... refinement of the anthropic principle to talk about observers rather than environments is essentially using ...
 05:07: And that’s the same guy who brought to popular attention and in fact named the anthropic principle to start with.
 08:17: ... can go into  but it’s worth covering some that get at how the anthropic principle is interpreted, in particular through the selfsampling assumption and ...


20191202: Is The Universe Finite?
 12:50: OK, so in the last episode we explored the scientific and philosophical implications of the anthropic principle.
 13:53: Scott Barnkow asks what are some testable predictions of the refined anthropic principle?


20191118: Can You Observe a Typical Universe?
 00:07: The anthropic principle guarantees that you are NOT seeing the universe in its most typical state.
 00:19: So, how do you correctly use the anthropic principle?
 01:00: ... central nor privileged position in the universe is called the Copernican principle after the guy who started it ...
 01:28: The Copernican principle became such a powerful tool that it took centuries for us to realize that it’s wrong  or at least flawed.
 02:08: This is the anthropic principle, and it seems to contradict the sacred Copernican principle.
 02:13: ... of the universe, and how these feed into two versions of the anthropic principle. ...
 02:25: ... we’re going to bring these ideas together with the Copernican principle to see just how powerful  and how misleading  the anthropic principle ...
 02:35: ... to the original definitions by Brandon Carter, the weak anthropic principle states that we must live in a place and time in the universe capable of ...
 03:10: ... just call it the anthropic principle: we necessarily observe from an environment capable of producing ...
 03:44: ... anthropic principle permits a new explanation for this finetuning besides blind luck or ...
 04:13: This use of the anthropic principle is highly contentious.
 04:31: Some of the bad rap of the anthropic principle comes from a distortion of the idea.
 04:37: ... the 1986 book the Anthropic Cosmological Principle, John Barrow and Frank Tipler misinterpret the strong anthropic principle ...
 04:54: But this commits the same flaw in reasoning that the anthropic principle may solve.
 05:00: The principle is NOT causal  it just tells us to account for an observer selection bias when interpreting the nature of our environment.
 05:17: ... other common misuse is to assume that the anthropic principle allows for any degree of extreme fine tuning of the properties of our ...
 06:32: We certainly don’t observe the universe in a typical, observerhostile state, and and so it’s tempting to use the anthropic principle here.
 06:57: The anthropic principle appears to fail here,  but to understand why we need to go all the way back to the Copernican principle.
 07:05: In fact we need to bring these two seemingly conflicting principles together.
 07:10: And in doing so we’ll end up with a much more powerful version of the anthropic principle  one that will even make testable predictions.
 07:19: By the Copernican principle, we are most likely to observe a very typical environment  this is just a statement of probability.
 07:32: ... anthropic principle tells us we must account for our status as observers when we interpret ...
 07:42: ... let’s formulate a refined anthropic principle: we should find ourselves in a typical region of the cosmos that is ...
 08:15: This refined anthropic principle gets really interesting when applied to our low entropy big bang.
 08:59: Our refined anthropic principle appears to fail here  but actually it doesn’t.
 09:03: We’ve just witnessed the potential power of this principle.
 09:08: ... random fluctuation in an otherwise highentropy cosmos, the anthropic principle predicts that we should be in the smallest such fluctuation that could ...
 09:55: For the anthropic principle to be useful and not misleading, we need to be careful.
 10:41: The anthropic principle and the selfsampling assumption encourage Bayesian thinking.
 11:15: Anything capable of thinking about the anthropic principle?
 11:41: The anthropic principle in its proper form is without question an important thing to take into account whenever we observe the universe.
 12:46: Used well the anthropic principle gives us a deep perspective on our place in the cosmos, and can also be a powerful, albeit slippery scientific tool.
 15:44: ... right  that's possible  but the point is that UNLESS that principle is somehow connected to the universe's later developing life and ...
 15:59: ... just as easy to imagine a physical principle that gives you only one universe with an unavoidable combination of ...


20191111: Does Life Need a Multiverse to Exist?
 02:34: This last possibility draws on something called the anthropic principle.
 02:37: ... the last episode we talked about the anthropic principle as it related to where we find ourselves in this universe  necessarily ...
 02:56: This is the socalled “weak” anthropic principle, as defined by astrophysicist Brandon Carter in 1973.
 03:13: ... themselves, neither version of the anthropic principle explain why lifefriendly planets or universes exist; they just say that ...
 03:27: ... strong anthropic principle tells us that there’s an observer selection bias that may help us ...
 10:48: Leaving aside the blind luck or intentional knobfiddling for now, let’s get back to the anthropic principle.
 12:34: ... albeit speculative ideas about multiverses, the strong anthropic principle seems to make sense of the incredible fine tuning of our own ...
 13:09: ... life may be extremely rare, and how this relates to the weak anthropic principle. ...
 15:24: ...  the fine tuning of our planet is less clear, but the weak anthropic principle makes it a totally plausible ...


20191104: Why We Might Be Alone in the Universe
 00:38: The anthropic principle tells us that we shouldn’t expect to find ourselves in some random corner of the multiverse  there’s an observer bias.
 00:47: In upcoming episodes we’ll be exploring this principle and its two main versions  the strong and the weak anthropic principles.
 00:57: ... strong anthropic principle tells us that an observed universe must be able to produce observers  ...
 01:11: But today we’re going to focus on the weak anthropic principle, although it’s anything but weak.
 01:41: And the weak anthropic principle is much more useful than that.
 02:26: The weak anthropic principle places no limit on how rare those yousupporting environments are.
 05:28: ... on Earth then it could be hugely uncommon  and the weak anthropic principle says it’s still not surprising for us to find ourselves on one of the ...
 11:40: ... weak anthropic principle allows that these singular events were phenomenally unlikely  we simply ...


20191021: Is Time Travel Impossible?
 10:17: One way for a closed timelike curve to exist without causing a paradox is expressed in the Novikov SelfConsistency Principle.


20191015: Loop Quantum Gravity Explained
 11:01: ... accepted forms, without taking away their most important foundational principles. ...


20190930: How Many Universes Are There?
 07:06: ... is an example of using the Anthropic Principle  we must exist in a universe capable of producing us, so if there are ...
 07:20: People have also invoked the anthropic principle plus eternal inflation to explain a conundrum in string theory.
 08:14: Enter the anthropic principle once again: eternal inflation gives us enough universes to easily populate the entire string landscape.
 08:36: Some people aren’t comfortable with the anthropic principle.


20190819: What Happened Before the Big Bang?
 10:04: ... connections between inflation and string theory and with the holographic principle, as described in one of Stephen Hawking's last ...


20190806: What Caused the Big Bang?
 08:29: ... fluctuate to different values, thanks to the Heisenberg uncertainty principle. ...


20190718: Did Time Start at the Big Bang?
 11:36: ... interpretation of internal inflation that draws on the holographic principle all things we'll discuss in the future as we travel beyond the beginning ...


20190715: The Quantum Internet
 08:33: ... we reach Ted – who should still get a copy of the original qubit C. In principle this can be done without the quantum channel ever becoming ...


20190701: Thorium and the Future of Nuclear Energy
 02:49: ... or via a secondary loop of water I just described very very crudely. The principles behind the light water thermal reactor These are the most common because ...


20190509: Why Quantum Computing Requires Quantum Cryptography
 04:21: Each highlights a different fundamental weirdness of quantum mechanics – the Heisenberg uncertainty principle and quantum entanglement.
 04:38: ... uncertainty principle tells us that we cannot simultaneously know the values of certain pairs ...
 06:37: You just switched between different quantum representations of reality and then back again, and so invoked the uncertainty principle.
 10:21: Maninthemiddle attacks are in principle still possible because Werner could impersonate Albert and Niels from the very start.


20190501: The Real Science of the EHT Black Hole
 08:24: In principle this could be a very narrow ring.


20190410: The Holographic Universe Explained
 00:44: The holographic principle emerged from many subtle clues – clues discovered over decades of theoretical exploration of the universe.
 00:51: ... a the foundations needed to glimpse the true meaning of the holographic principle. ...
 04:06: ... figured out a concrete string theoretic realization of the holographic principle with AdS/CFT ...
 15:16: ... that's actually the opposite of the proposition behind the holographic principle, which suggests that our percieved universe is the volume, but it can be ...


20190403: The Edge of an Infinite Universe
 02:15: ... and this will set us up finally for laying open the holographic principle. ...
 08:49: ... by the way, was a key discovery on the path to the holographic principle, as we’ve discussed before and which I’ll . review again  but not ...
 09:16: For the holographic principle we need the infinite boundary of a negativelycurved universe – an antide Sitter, AdS universe.
 15:06: Stay tuned for the final installment of the holographic principle in notsoinfinitelydistant future of spacetime.


20190306: The Impossibility of Perpetual Motion Machines
 01:36: Other types of overbalance wheels followed through to the Renaissance and worked on the same principle.
 05:30: ... principle a Carnot engine could extract energy from a temperature gradient and ...
 05:52: The Carnot cycle is, in principle, a perpetual motion process.
 06:30: Indeed there are ideal systems that, from pure classical principles should run forever.
 06:55: Due to the intrinsic quantum randomness of all particles, as expressed by the Heisenberg uncertainty principle, everything moves.


20190207: Sound Waves from the Beginning of Time
 14:12: ... Now, while I agree that this isn't a hard rule, it's a good guiding principle to be dubious of new theories that contradict extremely well tested old ...
 14:49: ... claims require extraordinary evidence." Again, this is a guiding principle, and it helps scientists sort through the overwhelming flood of poorly ...


20190130: Perpetual Motion From Negative Mass?
 05:25: That sounds crazy, and so we must invoke the ageold guiding principle of science, on par with Occam’s razor: the crackpot conjecture.
 06:04: ... founding postulate of GR is the equivalence principle, which states that there’s no experiment that can distinguish between the ...
 06:17: ... equivalence principle only works if all masses experience the same acceleration in a given ...
 10:32: We assumed that passive gravitational mass and inertial mass are the same thing – and that’s required by the equivalence principle.
 11:10: ... the geodesic equation, which itself arises directly from the equivalence principle, or from Lagrangian mechanics – a more modern version of Newton’s laws of ...
 11:31: So do we have to throw away the equivalence principle to avoid the worst craziness?
 12:28: ... negative inertial mass can’t exist and we want to save the equivalence principle and the rest of physics, we need to conclude that negative mass of any ...


20190109: Are Dark Matter And Dark Energy The Same?
 05:18: It should be the same as gravitational mass for the equivalence principle to hold.


20181220: Why String Theory is Wrong
 13:44: ... principle the standard model lives somewhere in the string landscape, but without ...


20181107: Why String Theory is Right
 13:17: There's plenty of historical precedent for mathematical beauty leading to truth, but there's no fundamental principle that says it has to.


20181031: Are Virtual Particles A New Layer of Reality?
 07:29: The Heisenberg uncertainty principle tells us that the perfectly defined momenta of virtual particles means completely undefined position.
 09:20: ... nothing can be so exact thanks, again, to the Heisenberg uncertainty principle. ...


20181025: Will We Ever Find Alien Life?
 11:26: But the principle applies to a doomsday tech, nuclear weapons, genocidal nanobots, willful or negligent environmental destruction, you name it.
 13:32: Now, this is a type of gauge symmetry that, in principle, unifies fermions and bosons.


20181018: What are the Strings in String Theory?
 12:05: Ultimately, it also leads to the ultimate duality that is the holographic principle.


20180920: Quantum Gravity and the Hardest Problem in Physics
 05:50: The Heisenberg uncertainty principle tells us the minimum energy of our beam for a given precision.
 06:28: Steady viewers will remember that the uncertainty principle talks about the tradeoff between position and momentum.
 06:37: The uncertainty principle also defines the precision tradeoff between time and energy.
 06:54: For those of you who already watched our episode on the Heisenberg uncertainty principle, here's another way to think about this.
 08:01: Given that sensible underlying structure, it's relatively routine to apply quantum principles, or quantize, most of the forces of nature.


20180912: How Much Information is in the Universe?
 01:25: That's the holographic principle, and we've talked a lot about some ideas leading up to it.
 01:30: ... worry, the full holographic principle episode is still coming, but our recent episode on black hole entropy ...
 05:35: In fact, in a sense, the holographic principle is a compression algorithm.


20180905: The Black Hole Entropy Enigma
 01:30: ... in terms of information theory and ultimately led to the holographic principle, which I promise we're getting to and are almost ...
 11:10: ... hinted once or twice that this simple idea led to the holographic principle, the idea that the entire 3D volume of the universe is just a projection ...


20180823: How Will the Universe End?
 16:09: In practice, the Heisenberg uncertainty principle makes this impossible.
 16:12: But really, in principle, there's no minimum precision with which we can know the electron's location, so there's no minimum size.


20180815: Quantum Theory's Most Incredible Prediction
 12:23: That means that it and the quantum mechanical principles on which it is founded are good representations of reality.


20180725: Reversing Entropy with Maxwell's Demon
 06:46: ... to detect approaching particles and open the door, mechanisms which, in principle, don't increase ...
 08:23: ... principle states that "any logically irreversible manipulation of information, ...


20180718: The Misunderstood Nature of Entropy
 02:14: In principle, that work can then be converted back into heat and so the temperature differential can be reestablished.


20180711: Quantum Invariance & The Origin of The Standard Model
 09:13: ... we need to apply quantum principles to our field, like considering its internal or self energy and allowing ...


20180620: The Black Hole Information Paradox
 04:41: ... believe more and more, only 15 years behind Hawking, that the accepted principles lead to a truly paradoxical conclusion." So it turns out that if we ...
 06:21: It's essentially invisible, but in principle the information is still there.
 09:03: And, in principle, those distortions could potentially influence outgoing Hawking radiation, allowing them to carry away their information.
 09:39: Leonard Susskind formalized this idea in the context of string theory in what we now know as the holographic principle.
 11:01: This violates the principle of monogamy of entanglement.


20180613: What Survives Inside A Black Hole?
 01:32: ... and also the gateway to blackhole thermodynamics and the holographic principle. ...


20180523: Why Quantum Information is Never Destroyed
 05:36: ... principle, a given wave function in a given potential could mean the wave function ...
 07:58: But all of this talk of quantum mechanics being deterministic seems a bit at odds with the idea of quantum randomness and the uncertainty principle.
 08:18: And the precision of the knowability of that value is defined by the uncertainty principle.
 08:35: And in principle, make enough measurements and you can extract all of the information from a wave function.


20180516: Noether's Theorem and The Symmetries of Reality
 00:17: These laws are consequences of a much deeper, more fundamental principle.
 06:02: ... falls like magic out of another deep lore of the universe the principle of least action, which states that the universe will always choose the ...
 06:24: It's a generalization of Fermat's principle, which states that light will always take the path between two points that minimizes the travel time.
 06:32: ... principle of least action extends Fermat's principal to any object moving on any ...
 06:43: ... principle of least action can be used to derive the laws of motion from the ...
 06:52: In a sense, the principle is axiomatic.
 07:07: Noether's allows us to figure out the true conserved quantities for any system that's evolving according to the principle of least action.


20180425: Black Hole Swarms
 10:52: And the twoslit experiment well, in principle, yes.


20180404: The Unruh Effect
 09:58: According to Einstein's equivalence principle, remaining stationary in a gravitational field is equivalent to acceleration in free space.


20180221: The Death of the Sun
 04:08: ... run up against the Pauli exclusion principle, the rule that says is that fermions, like electrons, can't occupy the ...


20180117: Horizon Radiation
 07:21: ... could, in principle, make the same oscillation by simultaneously hitting the drum everywhere ...


20180110: What Do Stars Sound Like?
 05:05: We've spoken in depth about Fourier analysis in a recent episode on understanding the uncertainty principle, so I won't go to too much detail here.


20171213: The Origin of 'Oumuamua, Our First Interstellar Visitor
 10:36: Well we generalize frequency as momentum because the Heisenberg uncertainty principle applies to momentum in general.


20171206: Understanding the Uncertainty Principle with Quantum Fourier Series
 00:16: ... going to open the door to really understanding Heisenberg's uncertainty principle, and ultimately, quantum fields and Hawking ...
 00:28: [MUSIC PLAYING] One of the most difficult ideas to swallow in quantum mechanics is Werner Heisenberg's famous uncertainty principle.
 00:49: See, the apparent weirdness of the uncertainty principle hints at an even weirder underlying reality that gives rise to it.
 01:31: But as you'll see today, in that unraveling, we are led unavoidably to Heisenberg's uncertainty principle.
 01:40: The uncertainty principle is most often expressed in terms of position and momentum.
 02:06: The uncertainty principle exists alongside this observer effect.
 02:16: To understand the origin of the uncertainty principle, we don't need to know any quantum mechanics, at least not to start with.
 02:29: However, it turns out that something like the uncertainty principle arises in any wave mechanics.
 05:41: That sounds an awful lot like a frequencytime uncertainty principle for sound waves.
 05:47: ... fundamental knowability of a sound wave, as is Heisenberg's uncertainty principle, it's more a statement about the sampling of frequencies needed to ...
 09:40: So that's exactly the uncertainty principle.
 10:45: The uncertainty principle, therefore, tells us that they must be completely unconstrained in position.
 11:59: ... "Quantum Mechanics," which includes a great episode on the uncertainty principle. ...


20171102: The Vacuum Catastrophe
 00:44: We saw in our recent episode that we can thank the Heisenberg uncertainty principle for this bizarre behavior.
 01:55: ... satisfy the Heisenberg uncertainty principle, the vacuum state of any fuel oscillation must be half of the tiny Planck ...
 08:56: But of course, it may be that advances in theory will resolve this catastrophe without requiring us to invoke the anthropic principle.


20171025: The Missing Mass Mystery
 12:09: The energy is borrowed from the energy of the vacuum for the minuscule time allowed by the uncertainty principle.


20171019: The Nature of Nothing
 01:09: ... defined, and this is impossible according to the Heisenberg uncertainty principle. ...
 03:34: But here we run up against that pesky Heisenberg's uncertainty principle once again.
 05:33: But the ultimate price is that virtual particles can exist only for the instant allowed by the Heisenberg uncertainty principle.


20171011: Absolute Cold
 05:04: The Heisenberg Uncertainty Principle tells us that there is an absolute limit in the knowability of particular combinations of properties.
 06:21: For example, the quantum fields that fill our universe also fluctuate due to the Uncertainty Principle resulting in what we know as vacuum energy.
 07:24: For example, Brian Greene's Exploring Quantum History delves much more deeply into the Heisenberg Uncertainty Principle.


20171004: When Quasars Collide STJC
 11:41: ... the finetuning problem isn't actually a mystery, or that the anthropic principle solves the problem without even changing the fundamental ...


20170712: Solving the Impossible in Quantum Field Theory
 15:06: ... applying the principle of least action in the determination of probability amplitudes, it turns ...


20170707: Feynman's Infinite Quantum Paths
 00:36: The Heisenberg uncertainty principle tells us that the more precisely we try to define one property, the less definable is its counterpart.
 04:35: That piece of physics was the principle of least action.
 08:06: That power comes from the principle of least action.
 10:04: The quantum action principle gives the probability amplitude of changes in the state of the field.
 11:50: The universe may obey the principle of least action, but Mr. Levine is more of a maximum action guy.


20170628: The First Quantum Field Theory
 10:26: ... example, the Pauli exclusion principle tells you that you can only have one fermion, or electron quark, et ...


20170621: AntiMatter and Quantum Relativity
 03:06: Pauli realized that to explain electron energy levels in atoms, those electrons must obey a rule that we call the Pauli exclusion principle.
 03:53: ... the same quantum state and therefore violating the Pauli exclusion principle. ...
 07:23: This is where the Pauli exclusion principle comes back.


20170503: Are We Living in an Ancestor Simulation? ft. Neil deGrasse Tyson
 03:51: That is a much deeper rabbit hole, one we'll need the holographic principle to explore.
 08:19: But both ancestor simulations and Boltzmann brains require us to invoke something like the Copernican principle.
 08:43: That last addendum is an application of the anthropic principle.
 08:51: ... reasoning with a dash of the anthropic principle tells us that we should be the most typical, the most common type of ...
 15:06: ... principle, if you were to take such an expanded cloud of particles and exactly ...
 15:57: ... principle, a perfect set of particle positions and velocities could be found such ...


20170426: Are You a Boltzmann Brain?
 05:59: This is an application of the anthropic principle.
 06:25: The anthropic principle may explain why we exist in monstrously improbable or rare circumstances.
 06:32: But the principle doesn't allow us to assume a circumstance for our existence that is any more improbable than is absolutely necessary.
 06:55: But it can also be thought of as an extension of the Copernican principle.


20170419: The Oh My God Particle
 10:42: So in principle, no one can regulate landing on it.
 10:57: ... United Nations developed the Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer ...


20170111: The EM Drive: Fact or Fantasy?
 10:13: ... principle, yes, as long as the timing between the antennae can be kept precise ...


20170104: How to See Black Holes + Kugelblitz Challenge Answer
 09:48: But it's not quite a black hole, and so in principle, the sphere doesn't have to collapse.


20161221: Have They Seen Us?
 15:32: In principle, you can do that with a warp drive.


20161208: What Happens at the Event Horizon?
 15:51: More generally, it allows pilot wave theory to agree with Heisenberg's uncertainty principle.
 15:57: In the Copenhagen interpretation, the uncertainty principle describes the intrinsic randomness of the quantum world.


20161116: Strange Stars
 03:27: The Pauli exclusion principle states that this is forbidden for fermions, the family of particles that neutrons belong to.
 05:49: It's as though the quarks trick their way around the Pauli exclusion principle by having some of them put on silly disguises.
 13:09: ... paradox, Hawking radiation, some string theory, the holographic principle, other ...


20161019: The First Humans on Mars
 10:07: They could in principle be any mass.


20160921: Quantum Entanglement and the Great BohrEinstein Debate
 08:09: But the principle is the same.


20160914: SelfReplicating Robots and Galactic Domination
 09:31: Perhaps a variation of the Anthropic Principle needs to be invoked.


20160622: Planck's Constant and The Origin of Quantum Mechanics
 01:35: ... and more formally, the Heisenberg uncertainty principle, describes the smallest distance for which an object's location can be ...
 02:12: ... Heisenberg uncertainty principle and the de Broglie wavelength, but also the Schrodinger equation, the ...


20160601: Is Quantum Tunneling Faster than Light?
 09:07: ... it's within the uncertainty range defined by the Heisenberg uncertainty principle, which is perhaps the deeper principle from which the de Broglie ...


20160316: Why is the Earth Round and the Milky Way Flat?
 00:44: Two key principles, equilibrium and symmetry.


20160127: The Origin of Matter and Time
 04:40: ... besides the invariance of the speed of light, the other fundamental principle of Einstein's special relativity at play here is the Galilean relativity ...


20160113: When Time Breaks Down
 05:20: But Einstein's equivalence principle tells us that a frame suspended in a gravitational field is indistinguishable from an accelerating frame.


20160106: The True Nature of Matter and Mass
 06:33: ... equivalence principle tells us that the feeling of being accelerated out in space is ...
 07:04: In fact, the equivalence principle tells us that the gravitational mass of an object and the inertial mass are the same thing.


20151209: How to Build a Black Hole
 03:15: ... neutron star fills this 6D quantum phase space depends on two important principles of quantum theory, the Pauli exclusion principle and the Heisenberg ...
 03:34: The Pauli exclusion principle basically just says that two things can't occupy the same place at the same time.
 05:04: Fortunately, there's another quantum phenomenon that let's us get around the Pauli exclusion principle.
 05:10: The Heisenberg uncertainty principle tells us that the properties of a quantum entity are fundamentally uncertain.
 06:04: ... Heisenberg uncertainty principle tells us that particular pairs of quantities, position and momentum or ...
 06:32: Therefore, the Heisenberg uncertainty principle tells us that they must have highly undefined momenta.


20151105: Why Haven't We Found Alien Life?
 02:01: ... we're touching on the anthropic principle, which states that an observer will always observe a universe that can ...


20151028: Is The Alcubierre Warp Drive Possible?
 01:23: First, it's important to note that this idea does not contradict the principle of a cosmic speed limit.
 03:59: Any FTL device can, in principle, be used to make a time machine.


20151007: The Speed of Light is NOT About Light
 01:21: But in his book, there's another, less well known idea his Principle of Relativity.


20150715: Can You Trust Your Eyes in Spacetime?
 01:22: Our principle tool for exploring flat spacetime geometry will be something called a spacetime diagram for representing physical events.


20150617: How to Signal Aliens
 06:55: ... give you a general flavor of the seeming tension between the equivalence principle and common sense that can only be resolved once we change our concept of ...
 09:28: I think the easiest is to invoke the equivalence principle.


20150603: Is Gravity An Illusion?
 07:21: Einstein called it the equivalence principle, and if you buy it, then maybe the falling frames really are inertial.


20150325: Cosmic Microwave Background Explained
 06:13: The short YouTube video here shows a demo of this principle in action.


20150304: Should We Colonize Venus Instead of Mars?
 01:59: It also means more available carbon dioxide from which, in principle, you might extract oxygen.


20150225: How Do You Measure the Size of the Universe?
 00:55: That's the part that we, in principle, can see with light or gravitational waves.


20150218: Is It Irrational to Believe in Aliens?
 03:18: It's that the alternative is so contrary to a closely held scientific principle, that it's quite difficult to swallow.
