Untangling String Theory | Answers With Joe

this video supported by curiosity stream like many of you over the last few months I've been sheltering in place as much as possible in the past of time I've been watching a lot of documentaries and for some reason I keep going back to documentaries about the Black Plague because they're just such a just such a pick-me-up you know I don't know I'm just kind of fascinated by how humans have dealt with situations like this in the past and the Black Death just seems like the ultimate example of this and I'm also fascinated by how you know situations like this have changed the world going forward afterwards but one thing that I keep thinking about in terms of the Black Death is that you know as bad as everything is now at least we know what viruses are you know at least we understand germ theory and we know at least what we're dealing with but back then they had no idea they had no concept of germ theory whatsoever I mean just imagine how terrifying that must have been when just everybody's just dropping dead around you and you have no idea why I mean I seriously wonder what would happen if you went back in time to the Black Death and tried to explain to them that actually it's these tiny little bugs that are too small for your eye to see and they get into your bloodstream and they and they tear apart your cells and oh what are cells right well I feel like one of the great through lines of science over the years has been the constant breaking down of things into smaller and smaller components you know cells organelles molecules atoms protons quarks it just goes on and on whenever we think we found the smallest thing there's always something smaller so imagining that at the smallest scale is what you basically get is this sounds insane but not any crazier than trying to go back to the thirteenth century and explain to them what viruses are and yet there's an entire field of science that revolves around this idea it's the fabled string theory and just like everything else just when you think you've gotten to the bottom of the rabbit hole there's more rabbit hole who he remembers life before smartphones or before any kind of cell phone was common who here remembers before there were any exoplanets anyone Bueller anybody here get the Ferris Bueller reference the point is all of that stuff I just listed happened incredibly recently in the time that I've been on earth there have been some major sea changes in science and that happens from time to time and that happened in physics at the beginning of the 20th century in 1905 a young patent clerk named Albert Einstein had what they called his miracle year he published a series of papers that completely revolutionized our understanding of light and gravity and the universe itself in a tournament invitation to the first sauvé international conference on radiation in the quanta in 1911 and she probably guess from the name the conference was all about quantum mechanics which had just kind of been theorized and there were still a whole bunch of different competing theories out there was kind of it was kind of the Wild West of quantum mechanics at the time Einstein's photoelectric theory which explained how photons can eject electrons from material was quantum in nature so he was invited to speak on that but not everybody was on board with it yet and he wasn't really that big of a deal at the time I mean yeah he had some some cool papers that have been published but six months before that he was you know he was a patent clerk by 1927 when the fifth sold a conference was held in Stein was a mega star a lot had changed since then quantum mechanics had basically been stripped down to its core and rebuilt a lot of it based around Einstein's theories and he came into that one like a box even so this particular conference kind of became famous because of a bit of a squabble between him and Niels Bohr over the nature of quantum mechanics Bohr's Copenhagen interpretation hinged on the idea that quantum objects quantum particles were inherently random in nature but Einstein liked the idea of a monistic universe and he didn't like that so he said no dice actually what he said prompted one of my favorite physics exchanges of all time he told Bohr God does not play dice with the universe - which Bohr replied Einstein stopped telling god what to do o physicist drums unfortunately for Einstein and his deterministic view of the quantum world started to lose popularity over time especially after Enrico Fermi discovered the weak force in 1933 before that there was just electromagnetism and gravity and at that point Einstein's ideas made sense but the discovery of the weak nuclear force and later the strong nuclear force kind of upended everything and then Einstein's theory of gravity on the quantum scale just didn't make sense anymore now flash forward to the 80s in electromagnetism and the weak force were found to be expressions of a single electro weak force that would come together at extremely high temperatures and the strong force can be explained the same way theoretically the idea being that in the early hot universe there was one singular unified force that was acting on all particles all the time and then it eventually diversified into the forces that we see today imagine a snowflake as the water cools it forms symmetrical bonds that give the snowflake its shape melt the snow flake and refreeze it in the bonds might form in a different way similarly that single unified force froze long ago into electromagnetism and the strong and the weak force but gravity is the holdout gravity is that guy you know that just has to be different for example the electromagnetic weak and strong forces all work through force carriers called photons bosons and gluons respectively and Einstein was fine with this at least when I came to electromagnetism but he drew the line at gravity because Einstein gravity wasn't a force it was kind of a quirk of geometry that was sort of the whole idea behind general relativity was that mass curved space-time itself so objects curved through a gravity well but they're actually following a straight line there's just no neat way to fold gravity into a grand unified theory of forces it's just far too weak to have ever played on the same football team as the other forces you know unless there's some deep structure or quality of matter that explains the difference as gravity just just kind of has to be its own thing physicists are like preschool teachers you know they're just they're just trying to keep order in the classroom and all the other forces are over here drawing their own business and then there's gravity sticking gum in someone's hair gravity why can't you be normal it's out of all this some scientists and mathematicians began working on a deep structure kind of theory to explain all of this and their work eventually became string theory so before I dig into string theory let me just let me just back up a little bit somehow in five years of doing this channel I've never actually covered string theory considering all the topics I do on here that seems impossible and yet it's true and I'm wondering if I put it off because subconsciously I I don't feel like I fully understand it myself you know I mean don't get me wrong I've covered all kinds of theories that I don't fully understand but those are usually kind of fringy theories that haven't been really fully explored whereas string theory has been very explored in a lot of places and it's very mathematical which I am very not so I guess I always kept it at arm's length it wouldn't be the first time I'd push someone away just because I didn't understand them [Music] all right so the thing about string theory is that you have to think sort of extra dimensionally which is kind of impossible for the human brain to do we all of course know Sagan's flatland analogy which he actually took from Edwin Abbott the idea that if you had two dimensional creatures living in a completely 2-dimensional world with no up or down no third dimension it would be almost impossible to get them to conceptualize what that third dimension might be like similarly with string theory we had to think of a fourth dimension and higher dimensions and it's just kind of impossible for us to imagine but the thing is the math works so we start with four dimensions that we know three spatial dimensions in one time dimension and the first effort to apply another dimension on to that of fifth dimension is Colusa Klein Theory Theodor Kaluza was a mathematician who devised this original idea around 1919 he was trying to find a way to unify gravity and electromagnetism by basically making both of them a quirk of geometry so he applied a fourth spatial dimension to Einsteins field equations and what he found was that when doing that electromagnetism emerged alongside gravity more on that in a minute a student of his name oskar klein would later refine it a little bit by saying that electromagnetism was a result of motion through the fifth dimension I've heard this explained like imagine you're an ant walking on a power line and yes there are the regular three dimensions that we're all aware of but you can also go around the wire there's sort of a looping dimension there and similarly Colusa imagined his fifth dimension as a cylinder climb would later imagine it as an extremely small closed loop and it's that compactification that makes it invisible client proposes a fifth dimension so small that nothing in the macro world could experience it directly you know quantum objects might loop around and fly through it but anything as big as us would never directly observe it and Einstein was actually a fan of kahlúa klein theory but he did feel that it was incomplete in fact Colusa shared that opinion with him saying that it had physical and theoretical difficulties in his original paper one of the major objections was that there wasn't really a reason for the extra dimension to be so small and it also didn't account for all the subatomic particles that we suddenly began finding as we started to understand the role of force carrier particles the fifth-dimensional idea just sort of hit a dead end you know particle physics moved on and fifth dimensional physics kind of became a footnote in science history so in the 60s and 70s a whole bunch of particle accelerators came online and we started to find proof of theoretical particles that we'd never seen before and this led to what's known as quantum chromodynamics quantum chromodynamics are all about the quarks and the different varieties of quarks that make up the protons and the neutrons the red the blue the green the up and the down quarks and so on and it solved a lot of the issues around the strong force and it started to look like our full understanding of the quantum universe was gonna be just just right around the corner the thing was in the middle of these particle collisions they started to notice some vibrations especially in some particle/anti-particle pairs that were happening that seemed to resemble vibrating strings this was hard to explain unless they were interacting with some weird geometry from another dimension so the extra dimensional idea started getting dusted off a little bit several different versions of it started going around postulating that the universe was made up of vibrating strings tiny vibrating strings that vibrate in four spatial dimensions in one time dimension by the 80s string theory was a new hotness parts really led by Edward Witten of the Institute of Advanced Study at Princeton quantum chromodynamics was cool and all but it still didn't explain gravity so a lot of these physicists just got tired of trying to make gravity fit into a four dimensional universe and we're like look at that crazy higher dimensional mass stuff works I mean mathematically anyway string theory was starting to look like the grand unified theory we'd all been waiting for going all the way back and explaining all the mysteries all the way to the Big Bang this is what Einstein wanted except for determinism Einstein's beef with randomness doesn't get solved by string theory it does allow for particle to have random values in their States now there is room for both randomness and determinism if you try hard enough there is sort of a side theory in string theory that proposes that there's 10 to the 500 universes making up a giant multiverse in each of these universes would have different physical laws or some of them maybe deterministic and some of them may be random that cheating feels like cheating but that that's that's a whole other rabbit hole let's let's get back to string theory so yeah according to string theorists the universe is made up of tiny vibrating strings very tiny possibly the most tiniest possible thing that could possibly exist in the possible universe yeah an actual measurement in meters would be something like a decimal point followed by 34 zeroes and then a one at that scale a string would be able to move through multiple invisible dimensions so Colusa klein is recommended there was only one extra dimension others had different numbers 10 and 26 were popular numbers for mathematical reasons but yeah once the foundation for string theory was laid down it quickly devolved into many other different types of theories including super string theory yeah super string theory accounts for all of the known particles in the standard model of particle physics that means the fermions that carry matter and the bosons that carry forces CF fermions and bosons are considered to be super symmetrical in super string theory so every Fermi on would have a boson partner and vice-versa the bad news is this means there are a lot of theoretical particles that have not been discovered in the standard model the good news is this means it's actually testable you can find those particles then you got some pretty good evidence for super string theory yeah string theory in general has been criticized for being untestable but in super string theory again you find those bosons yeah good and a super string theory evolve the number of dimensions kind of got whittled down I said earlier that 10 and 26 were popular numbers eventually 10 started to win out so of course just as the dust began to settle on that debate ed Witten and his team shook things up again in 1994 with a second superstring revolution this time they added one more dimension for 11 dimensions total and they called this one M theory the extra dimensions were compactified and folded in on top of each other to create what they call a khalaby Yau manifold which sounds like a part on a spaceship in a sci-fi movie that keeps breaking we're not going anywhere a cabin now without a new Columbia manifold become a member that powerline analogy that I used earlier with an ant well so it has that one dimension of looping so you can imagine if you if you cut that open and there were like a bundle of wires inside of it all of which loop in and around the Mantis go down and around it that's one way of making sense of it at least it's the best I can do without having a stroke so when standard quantum physics particles are assumed to not have any dimensions at all they're expected to be point like but in in theory the strings might be one-dimensional or they might be like a membrane all scrunched up and wrapped around inside multiple invisible other dimensions technically a membrane has only two dimensions so any similar construct that has multiple dimensions is known as a brane so now we are getting into brain theory and you can combine these invisible membranes into groupings and then give a prefix with the number of the groupings like say five brain or in my case melted brain I mean this is where I'm like I mean what for fans of the good place right now I'm cheney trying to figure out the dot over the I and the Jeremy Baer me this broke me the dot over the eye that broke me um I'm done but the math works there is math that shows that one dimensional strings and membranes five brains can all account for all the forces and particles that we see in our physical reality there is math that shows that vibrating strings can create the mass that charge the spin of all the particles of the standard model as well as all the predicted particles from supersymmetry the math makes all this work somehow but is that because we discovered some fundamental truth about reality or is that because we were so desperate to make the math work that we created several invisible dimensions just to make the math work I don't know I'm asking but what about gravity though that was the problem child that got us here in the first place how does brain theory and M theory account for that well each force has a carrier boson in in theory we have the three of the four bosons accounted for so according to in theory there should be a gravity boson now you might be asking what happened to Einstein's theory that gravity is just a quirk of the curvature of space-time well when Kaluza and Klein added another dimension that kind of changed the rules a bit see I remember what I said earlier about electromagnetism sort of emerging alongside gravity when you add a four spatial dimension what I meant by that is that movement through that fit the men in math anyway creates an electromagnetic force electromagnetism has the photon as its boson so with gravity it would have the graviton alright kids so today we learned string theory postulates that the fundamental units of our universe are vibrating strings fermions and bosons are the fourth dimensional result of those vibrations superstring theories are string theories that include a partner boson for each Fermi on in theory is a modern super string theory it says space-time has 11 total dimensions tennis space and one of time and the strings and M theory may be one-dimensional like a line on paper or they may be brains with multiple dimensions that look like strings when more dimensions are considered all fundamental forces including gravity are mediated by bosons and superstring theories including in theory if you stare too long at the abyss the abyss stares back at you that was said by Batman I think he may have been quoting somebody else I don't care the mental gymnastics required to imagine a columbia manifold are just just it's it's a it's a lot and this is of course a video that just scratches the surface of string theory there's way way deeper and mind-melting or that you can go string theory is kind of an umbrella concept at this point like I said there's an entire field of study around it so it's hard to just kind of dismiss it at this point but is this actually leaving anywhere or is it just magic math well I mentioned a couple of testable conclusions from string theory that there would be some undiscovered bosons out there that people have been looking for in particle accelerators ever since then and that was actually one of the many high hopes for the Large Hadron Collider when it went online that it would find some of these bosons it didn't at least not so far anyway yeah these particles exist on a range of heaviness where they're expected to be found and the experiments that LHC have actually pushed up the level of heaviness that these things would have to be turns out they're kind of chunky in fact some of these particles are heavier than some other particles that we've found at the LHC including the Higgs boson so it's starting to feel like if these particles exist we probably would have found them by now which means that the most testable prediction about string theory so far hasn't really yielded any results in another problem when it comes to the test stirring theories that hole 10 to the 500th universes and a multiverse thing because anything that doesn't actually get found here in this universe of physicists could just say well that's because it exists in another universe I mean imagine trying to pick the one marble out of a jar filled with 10 to the 500th number of marbles and as for all those invisible curled up dimensions there's no experiment that's come anywhere near proving that now there was an experiment conducted recently using the Chandra x-ray telescope that had some promise for string theorists the results of that actually were just announced in March so yeah Chandra was looking for accion's which are particles that are predicted in super string theory and they were looking for it around a black hole in the Perseus cluster the idea is that accion's would convert two photons in a high and strong enough electromagnetic field so it was looking at a black hole looking for some of those accion photon conversions and another swing and a Miss now it is possible that the conversion level that these accion's go through was actually just out of the range of what Chandra was looking for but it's also just as possible that they're just not there now this doesn't rule out string theory but it is yet another setback in a long string of setbacks oh come on so that is everything I know or think I know about string theory please feel free to correct anything I got wrong down in the comments like I need to ask like I said at the beginning there's a ton of great content out there on string theory by people who know a thousand times more about it than I do I will link to some of that down the description for you and it really is more of a math theory like if you were to ask me if I think it's real all I could say is I can't say that there's been any real evidence out there of it outside of the math which is so complex that I would never understand it even in a million years but that doesn't mean much I mean the same could be said for the algorithms and the the engineering and the math behind the pixels that you're looking at on your screen right now and yet there they are so yeah so I will reserve judgment and just keep trying to understand it a little bit better and I hope if nothing else this video served as a jumping-off point for you to do the same thing thanks for watching yeah quantum physics just kind of messed up everything you know we pretty good handle on the world and then they just the whole reason string theory even exists is to try to make up for all the weirdness of the quantum world so if you want to understand all that a little bit better and see how we got to where we are right now I can highly recommend secrets of quantum physics on curiosity string post about Jim al-khalili this series tells a story of quantum physics of how we learn what we know the surprises we found along the way and how it's changed our understanding of the universe this is of course just one of hundreds of documentaries on curiosity stream on everything from science and history to technology and a nature curiosity stream is the streaming service for 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Channel: Joe Scott

Views: 1,259,979

Keywords: answers with joe, joe scott, string theory, theory of everything, albert einstein, neils bohr, solvay conference, quantum physics, M-theory, brane theory, calabi-yau manifold, 11 dimensions, kaluza-klein

Id: NtG0nv8TNE8

Length: 23min 21sec (1401 seconds)

Published: Mon May 18 2020

Reddit Comments

[u/Jazzynupe]

Crossposting as requested on twitter. Very interesting/entertaining discussion of the overview of String Theory
https://twitter.com/VisualPhysicsIQ/status/1262398939363512326