Search PBS Space Time


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.
  • 14:41: 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 ...

2022-06-22: Is Interstellar Travel Impossible?

  • 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.

2022-06-15: Can Wormholes Solve The Black Hole Information Paradox?

  • 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 ...
  • 07:24: ... tidal wave of math in these papers  pulls ideas from string theory, holography,   quantum field theory, and  quantum ...
  • 11:25: ... had seen this equation. The island rule had already been derived in string theory.   The researchers were surprised to find  that you don’t need string ...

2022-02-23: Are Cosmic Strings Cracks in the Universe?

  • 12:19: ... 1-dimensional filaments called,  fittingly, strings. The strings of string theory   have nothing to do with the cosmic strings that I described. For ...

2022-02-10: The Nature of Space and Time AMA

  • 00:03: ... theories of the theme some of them try to answer this theory doesn't string theory assumes that this that the stage is there that the the space and ...

2021-12-20: What Happens If A Black Hole Hits Earth?

  • 17:55: ... could be tested. Actually, this might be the most testable prediction of string theory. There are simulations that suggest that the gravitational waves created ...

2021-12-10: 2021 End of Year AMA!

  • 00:02: ... open questions there and we talk about physics being stuck because string theory can't make progress in our giant particle colliders can't find new ...

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 ...
  • 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: ... String 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: ... 1996, 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: ... it was a decisive step and it gave us a compelling reason to think that string theory might explain where the microstates of black holes ...
  • 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 ...

2021-10-05: Why Magnetic Monopoles SHOULD Exist

  • 17:56: Physicists hope to understand these things someday, perhaps with twistor or string theory.

2021-05-11: How To Know If It's Aliens

  • 18:32: ... hurt 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 ...

2020-09-08: The Truth About Beauty in Physics

  • 00:37: ... it’s also been argued that modern theoretical physics, and in particular string theory, has been overly transfixed by the allure of beauty for decades, and that ...
  • 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.

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: ... physicist with really a hugely broad range of interests including string theory and loop quantum gravity in principle we could do this entire ...

2020-07-08: Does Antimatter Explain Why There's Something Rather Than Nothing?

  • 04:48: ... So, if there exists some underlying more fundamental theory, maybe string theory for example, then CPT symmetry may no longer be a foregone ...

2020-05-27: Does Gravity Require Extra Dimensions?

  • 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 ...
  • 11:32: ... near being able to probe the size-scale of the extra dimensions from string theory though, and so string theorists can keep on ...

2020-04-28: Space Time Livestream: Ask Matt Anything

  • 00:00: ... stuff as well I was certainly dreaming about quantum with gravity and string theory when we were writing those episodes so so it varies massively but you ...

2020-01-27: Hacking the Nature of Reality

  • 11:35: ... so string theory was born - at first as a description of strong nuclear force ...

2019-12-17: Do Black Holes Create New Universes?

  • 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 cosmological constant could take ...

2019-11-11: Does Life Need a Multiverse to Exist?

  • 11:24: ... example we have string theory: this candidate theory of everything suggests that the values of the ...

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.

2019-10-15: Loop Quantum Gravity Explained

  • 00:06: And can it really defeat string theory in our quest for a Theory of Everything?
  • 00:32: ... it quite a bit already, including what’s probably the lead contender - string theory. ...
  • 00:42: But string theory isn’t the only game in town - or so some physicists believe.
  • 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.
  • 13:16: Loop quantum gravity is an intriguing alternative to the more popular string theory.

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 ...

2019-08-19: What Happened Before the Big Bang?

  • 06:04: As well as theories which also unify gravity, like string theory.
  • 10:04: ... are also deep possible connections between inflation and string theory and with the holographic principle, as described in one of Stephen ...

2019-07-18: Did Time Start at the Big Bang?

  • 09:52: ... there 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 ...

2019-04-10: 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.
  • 05:53: We also see it in string theory, which I’ll come back to.
  • 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.
  • 08:44: This and other glitches led to string theory being abandoned as a model for the strong force.
  • 08:49: ... and the scale invariance of the strings becoming a central feature of string theory. ...
  • 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.
  • 09:52: Maldecena imagined a set of string theory objects called branes.
  • 11:38: As with the other dualities in string theory, this one was extremely useful for calculations.
  • 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 ...

2019-04-03: The Edge of an Infinite Universe

  • 14:20: That structure looked exactly like a string theory with gravity and everything.

2019-01-16: Our Antimatter, Mirrored, Time-Reversed Universe

  • 13:52: ... inverted 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: ... if 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: ... or wrongness. 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 ...

2018-12-20: Why String Theory is Wrong

  • 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?
  • 01:03: Could this also be the case with string theory?
  • 01:06: ... the very 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: ... under one 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: ... of this 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 ...
  • 04:57: These may have seemed like fatal flaws, but we can thank this wrongness for the later development of string theory.
  • 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.
  • 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.
  • 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.
  • 10:51: ... that it adds a single extra dimension, to connect all of the five super string theory types via ...
  • 11:41: See, in parallel to the development of super string theory, other physicists have been working on super gravity.
  • 11:49: ... Super 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: ... with each other and with super gravity restored the sense of beauty to string theory. It appeared to be on the track to rightness once again, so So where did ...
  • 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 ...

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.
  • 15:37: Actually, the name string theory originally applied to what we call bosonic string theory.
  • 15:53: And these days some form of superstring theory is implied when people talk about string theory.

2018-11-14: Supersymmetric Particle Found?

  • 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.

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: ... fact, 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: ... in 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 ...
  • 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.
  • 05:39: 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.
  • 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.
  • 11:44: ... you use string theory to write down the gravitational field in what we call the low-energy ...
  • 11:57: ... get the 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.
  • 12:43: 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 ...
  • 13:26: Perhaps we're now overly distracted by the elegance of string theory.

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.
  • 13:54: ... 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?
  • 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.
  • 01:20: 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.
  • 02:46: ... of the reasons this strong force version of string theory got stuck is that it predicted the existence of unexpected and unwanted ...
  • 04:20: This was so-called Bosonic string theory.
  • 07:29: So this is the great promise of string 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.
  • 09:31: String theory fixes this because the graviton is a loop, not a point particle.
  • 11:37: Voila, string theory is saved.
  • 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.

2018-10-03: How to Detect Extra Dimensions

  • 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.

2018-09-20: Quantum Gravity and the Hardest Problem in Physics

  • 12:08: That's exactly what string theory seeks to do.

2018-09-05: The Black Hole Entropy Enigma

  • 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.

2018-06-20: The Black Hole Information Paradox

  • 09:39: Leonard Susskind formalized this idea in the context of string theory in what we now know as the holographic principle.
  • 11:22: ... ideas about the nature of information and entropy, exploded the field of string theory, and hinted at the possible holographic nature of ...

2017-10-25: The Missing Mass Mystery

  • 13:17: Maybe we'll at least get some evidence for the string theory or something.

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.

2017-07-07: Feynman's Infinite Quantum Paths

  • 15:00: A few of you asked whether quantum field theory and string theory are the same thing.
  • 15:16: String theory states that all particles are different vibrational modes in one-dimensional objects called strings.
  • 15:30: ... with stunning success and is the foundation of the standard model, string theory is untested and may have nothing to do with ...

2017-06-07: Supervoids vs Colliding Universes!

  • 09:30: And it could happen frequently or rarely, depending on the completely unknown details of the string theory parameter space.

2017-02-02: The Geometry of Causality

  • 12:07: ... out of 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 ...

2016-11-16: Strange Stars

  • 13:09: ... go through the black hole information paradox, Hawking radiation, some string theory, the holographic principle, other ...

2016-06-01: Is Quantum Tunneling Faster than Light?

  • 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.

2016-03-02: What’s Wrong With the Big Bang Theory?

  • 04:31: ... together and what some of the resolutions might be-- [CLEARS THROAT] string theory-- another ...

2015-09-23: Does Dark Matter BREAK Physics?

  • 06:58: Sinking down into the depths of quantum field and string theory, you can find all sorts of strange fish, WIMPs, axions, neutralinos.

2015-08-19: Do Events Inside Black Holes Happen?

  • 00:24: That means no Hawking radiation, no string theory, and no quantum anything-- baby steps.

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 ...
50 result(s) shown.