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	2022-10-12: The REAL Possibility of Mapping Alien Planets! 06:05: ... telescope is sent to do the work. The second   is the string of pearls option, in which many so-called small-sats are sent in a ... 10:07: ... the Sun.   Remember that the scientists called this  a string of pearls. That first cluster of   craft was the first pearl. ...
	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 ... 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: ... as Robin notes, one of the vibrational modes of these strings looked like the graviton, so the entire theory was shrunk in size by ... 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 ...
	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 ... 06:54: ... using only general relativity  and accepted quantum mechanics - no string   theories attached. To be fair, these US teams, dubbed the ... 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 ...
	2022-05-25: The Evolution of the Modern Milky Way Galaxy 11:10: ... it pulls it back down. Like  beating a drum or plucking a guitar string,   the stars oscillate up and down in the galactic  plane, making a ...
	2022-04-27: How the Higgs Mechanism Give Things Mass 11:37: ... and we saw how this can lead to the creation  of cosmic strings in a recent episode.   But cosmic strings are the perhaps ...
	2022-03-08: Is the Proxima System Our Best Hope For Another Earth? 13:02: Nonetheless, we’re focusing in on a relatively stringent set of requirements for this exoplanet to be able to support life. 16:48: And the one on cosmic strings - topological defects that may span the length of the universe. 18:27: OK, on to cosmic strings. 18:33: When those cosmic strings radiate gravitational waves, how is the Higgs field supposed to smooth itself out? 18:46: ... episode - the simple vortex of phase angles making a loop around the string - is the most simplistic version of this ... 19:20: Or are cosmic strings the only indication of a change in phase angle? 19:45: I don’t know how you’d do this besides observing a cosmic string, but I suspect there are ways. 19:51: ... Scoot asks whether cosmic strings could explain the filaments and voids in the large scale distribution of ... 20:03: So the answer is maybe to the first two - but only if cosmic strings influence the CMB. 20:12: ... strings may have had sufficient density at extremely early times to leave an ... 20:24: ... is defined by those density fluctuations, so in that sense cosmic strings could have influenced it - but not directly in the sense of cosmic ... 20:38: ... - extremely unlikely - in our most accepted understanding of cosmic strings there aren’t anywhere near enough of them to account for dark ...
	2022-02-23: Are Cosmic Strings Cracks in the Universe? 00:00: ... defects stretching across the sky. These are   cosmic strings, and many physicists think that they have to exist, and that we can ... 00:58: ... formed from topological defects in the quantum fields, aka cosmic strings. They have subatomic   thickness but prodigious mass and they ... 05:59: ... met. Our ice cube forms sheets, but our  Higgs field formed strings. Remember   that the vacuum decayed in a random  direction ... 07:33: ... around a central line.   And that central line is our cosmic string. Other topological defects may be possible.   For example, a ... 08:50: ... horizon,   potentially leading to dozens of cosmic  strings in a network across the universe.   Unlike the topological defects ... 10:09: ... occurs, a pair of “kinks” is formed in each of the newly formed strings speed   away from each other along the string at near ... 12:19: ... give us the data that we need to find these. Now if we do find a cosmic string, there’s one   other point of confusion we’d need to ...
	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 ...
	2021-12-20: What Happens If A Black Hole Hits Earth? 14:10: ... as an explanation for dark matter, and the one on fuzzballs - the stringy theory version of the black ... 16:33: ... the faller, it continues to exist - coded in the complexity of the string vibrations. It’s holographically projected into 2 spatial dimensions, ... 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 ...
	2021-12-10: 2021 End of Year AMA! 00:02: ... let's see how about this one from laz the creator if i held the purse strings to an unlimited science budget what wild experiments or projects ...
	2021-11-17: Are Black Holes Actually Fuzzballs? 00:13: But many physicists will tell you that the best way to fix broken physics is with string. 00:18: String theory, in fact. 00:20: ... in the black holes of string theory - fuzzballs - are perhaps even weirder than the regular type ... 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 ... 06:01: ... String theory immediately solves the problem of the black hole singularity, ... 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 ... 06:37: ... the microstates on the horizon- the number of possible configurations of stringy structures - the 1-D strings themselves and higher-dimensional ... 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 ... 07:53: For instance, the profile of the radiation emitted by the strings precisely matched that of traditional Hawking radiation. 08:00: This was another stunning match to theory, and also a way for stringy black holes to leak out their information. 08:06: ... pretty good, but I realize that I haven’t really told you what these stringy black holes look like, or how they form, or how structure can actually ... 08:45: ... while he was exploring stringy black holes, Samir Mathur found that the strings that formed the black ... 08:55: In fact, if you have a bunch of strings dense enough to form a black hole in general relativity, it wouldn’t actually collapse. 09:02: Rather it would grow to produce an agglomerate of strings with the same radius as a classical black hole. 09:09: ... at all, but rather a real surface that looks like a tangled nightmare of strings and branes, like the hairball coughed up from some hyperdimensional ... 09:25: ... a fuzzball will see its constituents crushed into a soup of elementary strings. ... 09:52: The ability for strings to maintain structure in this extreme gravity comes down to an effect specific to string theory called fractionation. 10:02: ... tension of a string is inversely proportional to its length: tight rubber bands are ... 10:10: ... in string theory, when you merge a large number of strings, the tension of the ... 10:22: That means by crushing an enormous number of strings together, the resulting monstrosity can be stretched to enormous scales. 10:30: The normally Planck-length strings can therefore pile up into fuzzballs with sizes ranging from kilometers to light years. 11:07: But if you approach the fuzzball you start to see this surface of stringy material with a thickness of about a Planck length. 11:35: ... a fuzzball is forming, all of the matter - now dissolved into stringy mess, is pushed up to the surface and the interior grid of spacetime is ... 12:17: Now let’s try a string-theoretic version. 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 ...
	2021-10-05: Why Magnetic Monopoles SHOULD Exist 06:30: ... construction is called the “Dirac string”, and Dirac’s argument is that if the string part of the Dirac string is ... 06:43: The second part of the argument is under what conditions that string is undetectable. 06:57: Imagine a charged particle - say an electron - passing by a Dirac string. 07:02: To plot that trajectory you add up all possible paths of the electron, including paths to the left and to the right at the string. 07:09: ... presence of the string, with its magnetic fields, should introduce different phase shifts ... 07:22: In other words, the string would be detectable. 07:24: But there’s one scenario where the string can never be detected. 07:34: ... that charge, the phase shift induced between the different sides of the string is exactly one wave cycle - which means no observable ... 07:42: ... for the Dirac string to be undetectable then electric charge can only exist in integer ... 07:56: ... the upshot is that the string connecting monopoles is fundamentally unobservable, and Dirac argued ... 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 ...
	2021-02-17: Gravitational Wave Background Discovered? 00:00: ... gravitational waves and there are theoretical sources also cosmic strings topological seams in the fabric of space would produce waves when their ...
	2021-01-12: What Happens During a Quantum Jump? 05:10: He argued that the same emission spectra could be got by thinking of these levels as fundamental vibrational modes, like on a drum or guitar string.
	2020-10-05: Venus May Have Life! 13:48: And, ultimately, to ally with them in war against the cosmic string entities in the heart of the Sun that we discussed recently.
	2020-09-28: Solving Quantum Cryptography 09:52: Suppose Alice wants to send a message to Bob—”CAT” which is represented by the binary string 1 1 0 1. 14:24: Last week we talked about a highly speculative idea - lifeforms inside stars, formed from cosmic strings and magnetic monopoles.
	2020-09-21: Could Life Evolve Inside Stars? 00:16: Oh, and here’s an extra crazy one - life composed of cosmic strings and magnetic monopoles, evolving in the hearts of stars. 01:03: ... fundamental kinks and defects in the fabric of the universe - cosmic strings beaded with magnetic monopoles - may evolve into complex structures, and ... 01:28: What exactly are cosmic strings and magnetic monopoles? 01:38: Cosmic strings and magnetic monopoles are what we call topological defects. 03:56: A 1-D topological defect is a cosmic string - an extremely thin filament. 04:10: We’re interested in the strings and monopoles for now. 04:14: In certain theoretical scenarios, a monopole can be connected to the end of a string - or two strings, actually. 05:31: Can these string-monopole necklaces store information? 06:29: With semipoles, it’s possible to form string segments capped by NON-annihilating semipole pairs that actually repel each other. 06:36: In this way, it may be possible to develop complex string structures, analogous to chemistry. 07:00: Others have speculated that cosmic strings may get trapped inside stars in the process of star formation. 09:50: ... going to have to get a much better understanding of cosmic strings and monopoles - and, you know, actually verify that they exist in the ... 11:28: ... those who don't know, James is a higher being composed of cosmic strings and monopoles, visiting Earth from the core of the Sun to help spread ...
	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, ... 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. 11:05: String theorists find their math beautiful, even if it is far from being simple. 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 ...
	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 ... 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 ... 13:29: ... black hole - regions like the Carter time machine and the infinite string of parallel ... 15:33: ... the string of universes through the rotating Kerr black hole requires the ... 15:44: ... Polygondwanaland: in reality, impossible-seeming things like an infinite string of universes or a time machine indicate that the math may have led our ...
	2020-05-11: How Luminiferous Aether Led to Relativity 03:25: ... a wave on a string: each string segment moves up and down only, tugging on neighboring ...
	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 ...
	2020-02-03: Are there Infinite Versions of You? 11:39: ... duplicate region of the universe where Shakespeare’s plays are just long strings of S’s underscored with fecal smears - and where the infinite monkey ...
	2020-01-27: Hacking the Nature of Reality 11:24: Other physicists quickly realised that it was telling us that mesons could be described by a very particular type physical system: a vibrating string. 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 ... 12:57: ... a special thanks we pulled a few strings and got you moved over to the doom-never box . If anyone wishes to join ...
	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 ...
	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 ... 00:42: But string theory isn’t the only game in town - or so some physicists believe. 00:47: ... gravity that avoids a lot of conceptual baggage like tiny wiggling strings made of coiled up extra ... 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. 03:04: But for that to work first you need those strings to exist - and we don’t know if they do. 03:10: ... quantum gravity tries to quantize general relativity with no strings attached, while preserving the background independence already inherent ... 11:13: And without adding big assumptions – like the existence of strings or extra dimensions or supersymmetry. 13:16: Loop quantum gravity is an intriguing alternative to the more popular string theory.
	2019-10-07: Black Hole Harmonics 03:02: ... or a black hole – are analogous to the harmonics of a vibrating guitar string or piano ... 03:12: In the latter cases we can describe a vibrating string as a series of standing sine waves of different frequencies, all happening at the same time. 03:22: ... lowest frequency the string can support is called the fundamental mode – it’s usually the strongest ... 03:40: The full set of possible frequencies a string can support are called its harmonics.
	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 ... 07:46: The vast space of possible configurations of these compact dimensions is referred to as the string landscape. 08:01: We don’t know why our universe has the particular string vacuum state that it does. 08:14: Enter the anthropic principle once again: eternal inflation gives us enough universes to easily populate the entire string landscape.
	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 ...
	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 ...
	2019-05-09: Why Quantum Computing Requires Quantum Cryptography 07:43: ... generates a random string of bits, 0’s and 1’s and encodes these bits using photons polarized in a ...
	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 ... 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. 07:54: ... quarks – mesons – as this strand of gluons that behaves like a vibrating string. ... 08:15: That means you can pretend string length-slash-energy is a separate dimension as a calculation trick. 08:44: This and other glitches led to string theory being abandoned as a model for the strong force. 08:49: ... to make it a theory of quantum gravity, and the scale invariance of the strings becoming a central feature of string ... 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. 09:27: These arose from the way string size and energy scales could be rescaled. 09:34: But the strangest string duality was still to come with AdS/CFT correspondence, proposed by Argentinean physicist Juan Maldecena in 1997. 09:52: Maldecena imagined a set of string theory objects called branes. 09:57: These are like multidimensional strings that can serve as start and end points for strings, but also as spaces embedded within higher-dimensions. 10:15: The strings connected to these branes are scale invariant, so their length and energy can vary without changing the physics. 10:57: This quality fcame from the energy-scale-invariance of the strings embedded in the construction of this space. 11:04: In good string-theorist style, Maldacena defined incorporated that scale factor into be a new spatial dimension. 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 ...
	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 ... 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 ... 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 ... 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 ... 17:15: ... yeah string theory is apparently not yet testable, but I disagree with those who say ...
	2019-01-09: Are Dark Matter And Dark Energy The Same? 12:07: Which is good for string theorists, as Farnes notes, but not for observers because that’s not consistent with what we see.
	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: ... idea did work when translated to 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 ... 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 ... 04:57: These may have seemed like fatal flaws, but we can thank this wrongness for the later development of string theory. 05:07: For example, adding more compact dimensions of various shapes and, of course, strings. 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. 06:20: Five different approaches to getting all of the desired particles out of the basic premise of strings wiggling in ten dimensions. 06:32: What differs is the detailed geometries and symmetries of those spaces, and the way strings vibrate within them. 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. 07:50: Our tiny quantum strings can roam that small dimension. 08:01: ... number of times a string winds around this compactified dimension is called its winding number. ... 08:17: These strings are vibrating with standing waves like guitar strings, and their energy also depends on the frequency of that vibration. 08:25: That frequency depends on the density of wave cycles on the string. 08:30: ... divided by the radius. So, there are two ways to get a high-energy string: have a large winding number along with a large radius that gives you a ... 08:55: ... radius can be used to define the momentum of a particle produced by this string. ... 09:19: ... sounds weird but this may just have saved string theory. I just described a type of duality, in this case t-duality, ... 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. 09:59: In this case it's a duality between strongly versus weakly interacting strings. This seems even more contradictory, but it's incredibly powerful. 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 ... 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 ... 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 ... 12:53: The behavior of strings in these hyper dimensional surfaces is only understood in idealized cases. 13:08: ... 500 different topologies, the actual number is a lot higher. This is the string landscape. Each geometry for the compactified dimensions implies a ... 13:44: ... principle the standard model lives somewhere in the string landscape, but without knowing the geometry of the extra dimensions, ... 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. 14:55: So perhaps string theorists should also stick to their guns. 15:00: ... wrong or incomplete as current string theory may be, it may also be the inevitable early step as we seek an ... 15:14: ... the physics required to understand string theory is tough thankfully there are online tools that can help like ...
	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 ...
	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. 14:17: To quote, "I thought one of the fundamental properties of the strings was that the maths only works if they are one dimensional. 14:24: So how can you get world sheets?" Yes, it is a pain keeping the number of dimensions straight in string theory. 14:32: ... dimension of space and one of time, this is the shape traced out by a string moving through ... 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 ... 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? 00:48: What exactly is so compelling about tiny vibrating strings? 00:53: In our last string-theory episode, I talked about what these things really are and covered some history. 00:59: ... short, the strings of string theory are literal strands and loops that vibrate with ... 01:14: And, by the way, these strings exist in six compact spatial dimensions on top of the familiar three. 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 ... 02:19: But string theorists might disagree. 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 ... 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 ... 04:22: OK, let's switch to string theory where particles are not points. 04:32: When strings move on a spacetime diagram, they trace out sheets or columns. 04:37: In fact, you can think of a string not as a 1D surface but as a 2D sheet called a world sheet. 04:45: Now let's look at the interaction of two strings. 04:53: Even the most energetic interactions are smeared out over the string, so you avoid the danger of black hole creating infinities. 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 ... 05:20: And this is the second point in string theory's favor. 05:22: ... see, it turns out that tiny vibrating quantum strings automatically reproduce the theory of general relativity and, in the ... 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. 05:48: For some reason, vibrating strings are bizarrely well suited to quantization. 07:17: Quantizing the motion of strings also starts out ugly, but there are also some math tricks to make it work. 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. 09:36: It says that changing the scale of space itself shouldn't affect the physics of strings. 10:25: That's on the 2D dimensional world sheet of a quantum string. 10:30: ... the 2D sheet traced out in spacetime by a vibrating 1D string has this symmetry that lets us redefine the scale on its surface however ... 10:41: ... quantum wave equation from the equations of motion, but only for 1D strings making a 2D world sheet, not for any other dimensional ... 10:57: This is part of what makes strings so compelling. 11:28: So, with our quantized equations of motion in hand, you can predict the quantum oscillations of our string. 11:44: ... you use string theory to write down the gravitational field in what we call the ... 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. 12:25: ... String theorists hypothesize that the extra dimensions are coiled on themselves ... 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 ... 12:58: ... convergence is also seen in the union of different string theories by M theory and in the discovery of AdS/CFT correspondence-- ... 13:26: Perhaps we're now overly distracted by the elegance of string theory.
	2018-10-25: Will We Ever Find Alien Life? 08:46: ... Anchordoqui and collaborators found a less stringent limit on this likelihood by assuming that a lot of life gets wiped out ... 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 ... 14:04: ... he's referring to the number of calibrial manifolds that string theorists need to search through to find the geometry of our universe's ... 14:30: Now, some string theorists would say that there are zero free parameters. 14:43: Korbus Barkly and some others ask whether, if string theory makes no testable predictions, shouldn't it be just called string hypothesis? 16:20: Does not the idea of "shut up and calculate" and "we don't care what strings are made of" sound a lot like the flaws that science finds in religion? 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. 00:10: There are these tiny vibrating strings, and that's where all the force's particles, including gravity, in the entire universe come from. 00:18: This raises more questions than it answers, like why strings? 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. 01:38: I mean, why tiny vibrating strings versus literally any other tiny vibrating anything? 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. 02:09: ... suggested that the quarks in mesons are connected by-- you guessed it-- strings. ... 02:23: In this case, the strings are stretched out tubes of strong nuclear force, vibrating elastic bands made of gluons. 02:32: A lot of work went into figuring out a quantum theory for the strong interaction based on the physics of strings. 02:46: ... of the reasons this strong force version of string theory got stuck is that it predicted the existence of unexpected and ... 03:16: ... the type of particle produced by this little investigation into hadronic strings except that there's no way anything like the graviton should appear in ... 03:51: In fact, what if all force-carrying particles result from oscillations in tiny strings? 03:58: ... we needed was to make the strings a bit smaller, like 20 orders of magnitude smaller, shrinking from the ... 04:20: This was so-called Bosonic string theory. 04:31: If wiggly strings can explain force-carrying bosons, why not also the fermions that comprise matter? 05:22: Let's talk strings. 05:24: So wiggly strings could explain the whole universe. 05:29: To understand quantum strings, first we need to look at regular strings. 05:35: The key is that strings can carry waves. 05:38: And if the string has ends or is tied in a loop, then a wave will end up overlapping with itself. 05:57: Constructive interference only happens if the wavelength of the wave fits a neat number of times along the length of the string. 06:14: The result is that for a given string, only certain frequencies corresponding to certain energies are possible. 06:22: These resonant frequencies depend on the length of the string, also its tension, which defines wave velocity and so relates frequency to wavelength. 06:31: For example, this leads to the specific frequencies of vibration on a guitar string. 06:45: String theorists weren't the first to notice this. 06:57: But quantum strings are much more ambitious than boring electron orbits. 07:10: Particle mass just comes from the length of the string and its tension. 07:17: String length defines mass, but also defines which complex vibrational modes are possible. 07:29: So this is the great promise of string theory. 07:32: ... defining a single parameter, the string tension, or equivalently, string length scale, all of the possible ... 08:05: The strings are real physical strands, and the waves are wiggles in actual space. 08:36: Most string theorists are more interested in what strings do, not what they're made of. 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. 09:37: Its interactions are smeared around that string, handily avoiding the explosion of mathematical infinities you get below the Planck length. 09:45: All this stuff sounds great, and by the way, doesn't work for any other geometrical structure other than a 1-D string. 09:54: So vibrating guitar strings, yes. 10:01: ... the strings themselves are 1-D, but to even start to produce the properties of known ... 10:41: But this sort of thing doesn't deter string theorists. 11:16: Very tiny objects like quantum strings could explore that extra dimension, and importantly, oscillate in it. 11:30: Three large dimensions of space and six tiny Pac-Man dimensions that only strings experience. 11:37: Voila, string theory is saved. 11:54: ... theory unites different string theories because it demonstrates some philosophically fascinating ... 12:13: The exact behavior of strings depends on the shape of their compact dimensions. 12:19: In fact, the single free parameter in string theory becomes the configuration of the extra dimensions. 12:25: Find the right location in this string landscape, and you perfectly describe the universe. 12:43: Right now string theory appears to be at an impasse. 12:53: Tuning that string landscape to match our universe is daunting and perhaps impossible. 13:08: In coming episodes, we'll look deeper into both the successes, the failures, and the profound weirdnesses of string theory. 13:17: And you can decide for yourself whether you accept the fundamental stringy nature of space time.
	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. 11:02: So string theorists are OK for now. 13:02: And string theories are an example.
	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 ...
	2018-04-18: Using Stars to See Gravitational Waves 05:00: ... in which binary supermassive black holes were common, or from cosmic strings, if they ...
	2018-03-15: Hawking Radiation 02:55: They can oscillate with different frequencies, much like the many possible vibrational modes on a guitar string. 03:01: A particle is like a note on the string. 03:32: One way that quantum fields are very different to guitar strings is they can have both positive and negative frequencies.
	2017-10-25: The Missing Mass Mystery 13:17: Maybe we'll at least get some evidence for the string theory or something.
	2017-10-19: The Nature of Nothing 08:51: ... the same way that an organ pipe or a guitar string of a particular length only resonates with waves of certain frequencies, ...
	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.
	2017-07-12: Solving the Impossible in Quantum Field Theory 04:09: ... equation you string together from this one diagram represents all of the ways that two ...
	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 ...
	2017-06-28: The First Quantum Field Theory 02:03: Anyone who's ever strummed or shredded knows that a stretched string vibrates with a certain frequency when plucked. 02:22: ... any point in time, every point on a vibrating string is displaced by some distance from its relaxed or equilibrium position, ... 02:38: Guitar strings are one-dimensional, but we can expand the analogy to any number of dimensions. 03:45: And let's go back to the string. 03:47: If this were a quantum mechanical guitar string, then there'd be a minimum amplitude for the vibration that depended on its frequency. 04:26: Everywhere in the universe, that value is usually zero, but just like the string or the air density field, it could oscillate.
	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.
	2017-03-15: Time Crystals! 04:28: So you prepare a string of ions where the line spins.
	2017-02-02: The Geometry of Causality 05:15: ... from my stationary point of view, I define my x-axis as a long string of spacetime events at different distances, but that all occur ... 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 ... 12:22: One idea is that the inside of an event horizon is composed of a ball of raw strings, a so-called fuzzball, and that no infinite density exists.
	2016-11-16: Strange Stars 13:09: ... go through the black hole information paradox, Hawking radiation, some string theory, the holographic principle, other ...
	2016-10-12: Black Holes from the Dawn of Time 03:21: For example, the collapse of cosmic string moves and the collision of bubble universes?
	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 ...
	2015-12-16: The Higgs Mechanism Explained 01:32: But now, add some energy to that field at a particular spot, and it's like plucking a guitar string.
	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 ...
	2015-06-17: How to Signal Aliens 09:13: ... has a balloon in it filled with helium that's attached to the floor by a string and I simultaneously drop the van off a cliff and cut the string ...
	2015-06-10: What Happens to a Helium Balloon in Freefall? 00:26: Now, in that balloon video, there's a helium-filled balloon attached by a string to the floor of a minivan. 00:39: And at the same moment that I let go, I want to cut the string that holds the helium balloon to the floor.
	2015-06-03: Is Gravity An Illusion? 04:51: That is the new vertical and the pendulum string and the balloon string are just aligning with the vertical the way they always do.

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