Quantum Anomalies with Lara Anderson

22:33Neil deGrasse Tyson:And they're fundamental to the Marvel universe, the tesseract. Yeah, no Marvel powers that I am aware of. But one of the elements of that question was, how can a string accomplish anything if it's not interacting with another string in a higher dimension? And indeed, we expect they do. So strings in string theory, they can break apart. You can have one string that could break into two pieces. They can merge into each other. I did not know that. Yeah, you can also have things like, as I mentioned, the endpoints of the strings are actually dynamical. So where the strings are, that's part of the theory too.

23:10And so things can kind of dissolve into their endpoints and come back out again. And there's all sorts of weird silly putty games you can play with these 1D objects.

23:19Neil deGrasse Tyson:And if you take two endpoints and join them, what happens? You can have, depending on the shape of the string, you can have things like closed strings where they form little loops and they can merge together and form bigger loops. You can have a single string that can be open and then become closed. You can join two strings together and get another string of a different configuration. So lots of possibilities. Okay. However, if you have an open string, you can vibrate it in whatever way you want. If you close the loop, you can't fit an arbitrary set of waves in a closed loop. That's right. It does change the vibrational modes.

23:58So just like things like the length and configuration of violin strings, as you mentioned, or the standing waves that can exist on them, all of those change for classical strings and they change for quantum mechanical strings too.

24:08Neil deGrasse Tyson:Okay, so they are effective. Okay. Yeah. Just making sure. Okay. So Jordan, what else you got? I got Ethan Brady here. Ethan Brady says, Hey, StarTalk, I'm currently a student at a community college. Recently, my entire class got sparked into a debate due to the following question. If a higher dimensional object intersected our space-time, could it appear to us as a black hole? That's such a cool question. I want to hang out in your community science class. That sounds really cool. So short answer is, yeah, sort of. So what we, first caveat is, we don't know what's happening inside a black hole.

24:44Neil deGrasse Tyson:Well, go find out. Yeah. You don't have a free weekend or something to just go sneak out there, check it out? Take an iPhone with you? Take some pics. I've seen the sci-fi films on this. If anybody is sending folks, I'm ready. But in general relativity, in Einstein's theory of gravity, one of the ways that we characterize black holes is through singularities. So where, you know, the sort of smooth trampoline surface of space time that we understand gravity to be, where that starts breaking or getting, you know, crisscrosses, you know, creases, spikes in it. And so one thing that is certainly true is that if you have a singularity in some subset of your dimension.

25:28So imagine that you have a singularity that we would see as something like a black hole in three dimensions. That can be, quote, resolved or smoothed out by having higher dimensions available. So one way of sort of visualizing that is if you imagine you had like two lines that cross in a plane, like if, you know, plane of a piece of paper, where those two lines cross is mathematically a singularity from the point of those curves. Because, you know, what happens right at that intersection point doesn't look like a smooth curve anymore. But if you had an extra dimension where you could pull those two apart, then it doesn't have to be singular anymore.

26:01Now you just have two separate smooth curves sitting there. So the same could be true for space-time in that things that look singular in our universe could actually be smoothed out by having extra dimensions available.

26:12Neil deGrasse Tyson:So the answer is yes. Yeah, great question and great conversation. But why not take an extra step? could most of the things we see, think of, and interact with in our three-dimensional universe be the shadows of higher dimensions cast into our world? In terms of the size of those dimensions, this gets tricky because we know that if there were big things, big extra directions for things to move in, that we would have seen those with the way that all sorts of experiments run. So, for example, in atom-smashing experiments like the Large Hadron Collider, you're smashing two protons together and you watch all these pieces fly out and you calculate their kinetic energy and how they're hitting all these detectors and if there were large extra dimensions that were the same size as the rest of our universe things would fly off into them and you'd watch all these pieces just disappear all the time you'd watch energy and mass disappear so we know that doesn't happen so we have bounds on how big those extra dimensions could be based on the fact that we see most of the mass and energy that we experience in our universe contained to our universe.

27:19Neil deGrasse Tyson:Oh. So if the extra dimensions were just sitting there available to the experiment, you would lose information into those dimensions. Yeah, or stuff. You could lose mass, energy, all sorts of stuff. You can lose stuff. I mean, that movie I want to see. We are the shadows of another dimension where we're constantly losing stuff. That's where the socks went in the dryer. Where are my keys? Well, how much time do you have? It's a long explanation. Yeah, keys and socks, I think. The dryer is the portal. That's what it is. Right, that's where you lose your stuff. Okay, so Jordan, next question. Next question is from William Warren.

28:03William says, hello, Dr. Anderson, Dr. Tyson. This is William Warren from Abington, Maryland. If extraspatial dimensions really exist but are curled up too small for us to see, Is there any realistic experiment that could reveal them within our lifetimes? Or are they likely to remain forever beyond our ability to test?

28:22Neil deGrasse Tyson:Thank you so much. Yeah, Laura, why don't you just uncurl them? I mean, come on now. What are you waiting for? So it may not be that they are actually all that small. So we were talking a minute ago about how we might lose matter and energy into extra dimensions if they were big. But physicists are actually doing experiments in our lifetime. who knows how they'll go, to try and probe what they call large extra dimensions. And the large is kind of funny to non-physicists because we don't mean large like the scale of this room. We still mean like 10 to the negative 19 meters. But there are actually experiments at things like the LHC where people are doing these atom smashing experiments and then trying to see are there any deficits in energy or outputs from these processes.

29:04So is it the case that you could really be seeping some things into extra dimensions? Another use of those extra dimensions that people have considered is, you know, if some forces in nature interact with the extra dimensions and some don't, that could explain why gravity is weaker than the other forces, for example. For example, if, you know, gravity could seep into those other directions, it's sort of diluted compared to the rest of the forces. So there are lots of potential experiments that could, in our lifetimes, shed light on those scales. In string theory, I'd say the best bet is actually going to be not that, but a more indirect argument either for or against string theory based on the predictions it makes.

29:43I think it's very possible that we could prove that string theory is just straight up wrong based on the fact that it just can't get things right about our universe that we already see.

29:52Neil deGrasse Tyson:So she just slipped something in there that I need some pause. You just said gravity is the weakest force. How weak is it? Very weak compared to the others. How weak is it? How weak? Many orders of magnitude weaker than the other forces. It is 40 orders of magnitude weaker. Yeah. Oh, that's like nothing. Than electromagnetic. I got one for you. Ready? And I think I verified this arithmetically. If you went to the top of a rocket that we launch into space and removed all the electrons from the top one cubic centimeter, and put them at the bottom of the launch pad, that leaves a net positive charge in that cubic centimeter.

30:40Neil deGrasse Tyson:And you have negative charges down there. What do negatives and positive charges want to do? What do they want to do? What do they want to do? I mean, they just want to hang out. Together. They want to be together. Together. They love to bond. Their force of attraction is large enough to prevent the rocket from launching. That's amazing. That is amazing. Yes. Yes. So gravity is really freaking weak. You guys are dogging gravity. I mean, come on, gravity's worked. It's been so long. Gravity's so weak, I can reach down. How weak is it? And I can just pick this up. I have the entire Earth pulling on this, and I can just pick it up just by bending over.

31:20It's actually a really good thing for all the stuff in our universe, right? Because you couldn't have things like tables and chairs and people that are all held up by electrical interactions, if that wasn't true, right? If gravity was stronger, we'd all just get pancaked.

31:32Neil deGrasse Tyson:Yeah, the table wouldn't hold. The table's held together by electromagnetic force. You're held together by electromagnetic force. The cup is held together by. And gravity does not collapse it into a pile of goo. Gravity is much stronger than you guys give it credit for. No, it's not. In high school, I wanted to dunk a basketball. And I will tell you, I tried my hardest over and over again. And gravity thwarted me every single day of high school. Is that right? How big are your hands? I have big hands. It has nothing to do with my physical. It's gravity. Those are big hands. Could you? Okay. Are you able to?

32:08Could you ever dunk a basketball?

32:09Neil deGrasse Tyson:When I was in ninth grade, I could palm a basketball and dunk the ball. Why couldn't you now? I didn't say I couldn't now, but I said that's when I first did it. I can't now. Neil. Because of gravity. I can't now either. Because of gravity, Neil. Because of gravity. Okay. So I'm curious about this, that you can lose strength leaking into other dimensions. and I'd heard, and I don't know why because I didn't take these graduate physics classes, I heard that electromagnetic forces are contained within our universe, but gravitational forces can leak out and be felt by an adjacent parallel universe.

32:46Neil deGrasse Tyson:Is that true? Or at least extra dimensions. Yeah, so the sort of theoretical framework we're describing isn't necessarily string theory. It could exist outside of string theory And that's a proposal for maybe why gravity is weaker, why the hierarchy problem, as it's called in particle physics, you know, that separation of scales between gravity and the other forces exists. Could what we call dark matter be ordinary matter in an adjacent universe, but its gravity is spilling out into our universe and we're saying, oh, we have a magical force here, it's dark matter, when it's just regular matter spilling into our universe?

33:23It's a fair question, and we don't know what dark matter is, so all bets are on the table at this point. I think there's a lot of proposals for this, but no one is sort of universally agreed upon in terms of what would be the definitive answer like, yes, for sure this works. So if you can see one of these large extra dimensions in an experiment, that would be for sure a great confirmation. The other way you can try and do it is to ask a question like you just did and say, is there some signature, either in terms of particles or forces or interactions that we would see if, you know, that explanation is right, right?

33:58Gravity is weak because it's leaking into another dimension. What else would we see in an experiment? What would be the consequences of that prediction? And if you could make, you know, concrete predictions that you can then go test, then you're up and running.

34:09Neil deGrasse Tyson:All right, I'll get right on that, okay? And yeah, spoiler alert, hasn't happened yet, so this is still an open question. All right, give me some more. This is what we got. We got from Jay Valiano. Now, dear Dr. Anderson, is it possible to explain the consistency test d minus 10 equals 0 in layman's terms? And how come some theories speak of 11 dimensions if the formula is 10? Thank you and kind regards from Holland. Oh, I like Holland. So, first off, nobody when they were first trying to understand string theory wanted extra dimensions. They would have been very happy if we could just keep our three spatial and one time-like dimension.

34:45But the origin, let's start with the d equals 10 in string theory. So string theory is this idea that you can, you know, you can put it on a t-shirt. It's very concise to say that all matter energy in the universe are these little vibrating strings, right? Sounds really great. But then you try and say quantum mechanically, what would that mean, right? Like if I have these little quantum mechanical strings, how would they move? How would they behave? Could they be consistent? And it turns out that theories, before you look at the sort of smallest quantum mechanical distance scales, they make promises.

35:15So some of those promises might be things like electric charge should be conserved, should not be created or destroyed in interactions. Quantum mechanically, now you have this probabilistic theory where all sorts of uncertainties and possibilities and quantum weirdness takes over. And those classical promises can get broken. So you could have the conservation of electric charge as being violated quantum mechanically. And it turns out that when that happens, it's called an anomaly in quantum field theory. These anomalies goof up the bookkeeping of your theory. So it's like a bank where you're having pluses and minuses, adding up all the tallies.

35:54And if you don't keep the math right, if all the numbers don't add up, then it's not just that the theory is going to make a bad prediction. It's that the theory just doesn't even make sense. It's not consistent. It's not a useful tool for the things that you wanted it to do. So when people started studying these string theories 40 years ago, they tried to consider these quantum anomalies and ask whether they were really fatal, whether they were going to, you know, sort of kill this whole line of research. And what they found is that all of this quantum uncertainty, this sort of wiggling and violation of these principles that we think should hold, magically cancels out when you have 10 dimensions.

36:29These quantum anomalies cancel exactly. So the theory becomes really robust and really rigid. It starts making all these theoretical structure and predictions at that point. And then you can ask questions. You can say, well, what does this predict? What does it mean? Can it work? And we're still trying to figure that out. But at least you have a mathematically internally consistent theory at that point. So that's where the D equals 10 comes from.

36:52Neil deGrasse Tyson:I love the phrase quantum anomaly. It just feels cool. It feels like a Kendrick Lamar line. It's just playful. It's fun. It's specific. Yeah, yeah, yeah. All of the above. I want to say on this side of the earth, near Holland. This is from northern Sweden. Okay. I think that's near Holland. You're American, so you have no clue. I'm going to say it's close. This is from Frederick Johansson. Why is it so difficult to access the higher dimensions? Do you think we'll ever get to see or manipulate them in any way? People really want to know. Yeah. People want to see. Are we actually going to see this effect?

37:31Are we going to be able to prove it in our lifetimes? What do you say to Frederick?

37:34Neil deGrasse Tyson:Let me give another lead into that. We're familiar with the story, the book Flatland by Edwin Abbott. I think that was published back at the turn of the previous century around there. And it chronicled the encounter between people who lived in a flat universe, these squares and triangles and other shapes, and then they encounter a three-dimensional shape. And they freak out and don't know how to explain it. And there's a hierarchy of how many sides you have as a measure of how aristocratic you are. Of course, you have to throw that in there as well. My question is, if you're a square in flatland, what's preventing you from finding that direction perpendicular to your flat universe to just get a peek at three dimensions?

38:25Neil deGrasse Tyson:what's stopping us in three dimensions from finding that portal to get a peak at fourth dimension why are you preventing us from doing that that's a really good question and you know you're exactly right so in the flatland analogy if you just had two dimensions and there's a third just sitting there yeah your little 2d you know flat people could just pop out of that universe up into a three-dimensional space and indeed if you let things go right you just let them you know move have kinetic energy, bounce into each other, have collisions. If you have large extra dimensions, you would do that. You would see them, you would move into them.

38:59You'd, you know, you can't prevent or, you know, force things into other restricted set of dimensions without a lot of effort. The catch with the extra dimensions as they're arising in string theory is this notion of scale again. So imagine that, you know, we are three-dimensional beings. Imagine that, you know, you're walking on a rope, right? And you can walk down the length of a rope, tight rope balancing. If I say, can you walk around, you know, the radial direction or the, you know, the circular direction of the rope, you know, rope compared to our feet, right, is really hard. We can't really resolve in terms of our motion, that extra two-dimensional surface of the rope.

39:37If you imagine zooming that even further, you know, if you look from very, very far away, that rope looks essentially one-dimensional. So the problem is just all the interactions that we're measuring are on such a big scale that they couldn't access these extra directions that we're talking about that would be wrapped up around our existing universe.

39:56Neil deGrasse Tyson:Okay. So she weaseled out of that one too. Did you hear that? You hear that weaseling? Yeah, yeah. You're saying we can't get to those other dimensions because they're so tiny. But if they were big, are you then allowing us to say that they would come into view and we can step into them? Yeah. And as I mentioned before, people actually think that maybe these extra dimensions are big enough that we could see them in particle physics experiments. So that's all it has to do with. How big the dimension is. Do we have certainty on the size of the dimensions? We know that they can't be bigger than certain energy scales.

40:32So the experiments at the LHC, for example, are probing around up to a few TeV of energy or roughly about 10 to the negative 19 meters. So we know that they're not bigger than that, or we would have seen them already.

40:45Neil deGrasse Tyson:So a TEV, just to catch us up here. So an EV is not an electric vehicle. It's not. No, no, not in this context. It's an electron volt, which is a unit of energy. And it's the energy. I haven't done this since like physics 102, but it's. I like that even as you're being humble about it, it's not physics 101. It's physics 102. Just to be clear. I skipped 101. So it's the energy it takes to move an electron, which has a charge, across a potential difference of one volt. That's an electron volt. Did I get that right? I think so. All right. Yeah, I remembered it. Okay. So that's helpful when you're talking about particles because it's native to their world, right?

41:34Neil deGrasse Tyson:And so a tera electron volt is 10 to the 12 of these things. That's a big number. That's a big number. And that's the energetics of our particle accelerators today. Again, thinking about these different wavelengths of light and what you can see, just using photons as an example, you think about radio waves. How big does a radio tower have to be in order to make radio waves? It has to be the size of a building, roughly like tens of meters. That's the length scale that you're probing if you were to bounce radio waves off things. And the grading on your microwave has to be millimeter size to keep all the microwaves inside your microwave box.

42:09and now we're talking about distance scales of less than 10 to the negative 19 those are really energetic things, photons, particles, whatever that you need to be able to probe that low. So it's hard. There are ways, as I mentioned though, indirectly to try and either prove or disprove the theory and lots of clever theorists are trying to conjecture or come up with sort of no-go results that could prove string theory wrong in other ways. So could we see extra dimensions in our lifetime? Maybe. and people are looking. That would be great if we do. And even if we don't, we might be able to decide some of the merits of this in other ways.

42:44Neil deGrasse Tyson:I just like the idea you can make a dimension big enough to then just say, I want to visit that. I mean, you'd want to. You'd want to. And that's got to be completely mind-blowing. Like a square looking at a cube for the first time, that's got to be mind-blowing. Oh, God, yes. And how disappointing from the other direction. Is that all I am, a square? Yeah, a cube looking at a square is like, oh, okay. Well, you do that all the time, looking at your shadow. You're right. I'm always, and I'm always disappointed. There are great animations online, by the way, of three-dimensional shadows of four-dimensional stuff.

43:15Definitely worth checking out.

43:17Neil deGrasse Tyson:Oh, I've got to find those. Oh. All right.

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45:38Give me a couple more here. Okay, Trip Me Salo says, Hi there, Neil and the gang. This is Salo from the Philippines. String Theory says there are hidden extra dimensions curled up all around us, But holography? Holography? Holography? That's right. Is the holographic universe? Is that the... That's... Yeah, well, but holography? It's not holography. Holography? Yeah. Yeah. We'll fix it and edit. Edit around this. Make me look smart. Fix it in post. All right, yes. It suggests our entire universe is just a projection from a flat 2D boundary. Is it possible that both of these theories are actually right?

46:15Are those extra dimensions just part of that projection? More power to the show, and I hope you can visit your Filipino fans soon.

46:22Neil deGrasse Tyson:Oh, very nice. I've actually never been to the Philippines, but I'll put that on the list. You got a friend there. Yeah, yeah. So I don't know that we are sure about whether we're living in a holographic universe or on the surface of a black hole, but the underlying physical idea that I think is really exciting is that things like gravity or things like gauge theories, which describe things like electromagnetism, seem to be very deeply related in their structure in ways that no one had anticipated, you know, many decades ago. And so one utility in a physical theory is that if you can simplify things, if you can come up with a really simple framework that could make a lot of cool predictions, that's useful.

47:02So one of the things that's really neat about the holographic principle is if you take, for example, our, you know, three-dimensional universe or four-dimensional space-time, if you said that all the dynamics or things that are moving in our core universe, if that could be simplified to something that's happening on the boundary of our universe, if we could describe it that way, that'd be really powerful. And there are in fact people that are trying to answer exactly that question independent from string theory. There's a whole program known as celestial holography, which sounds really cool, talking about the celestial sphere at infinity in our universe and how all the information of things like gravitation in our universe might be encoded on that boundary.

47:39So it's a theoretical tool, but it might be a very useful one long-term.

47:43Neil deGrasse Tyson:Yeah, but you're saying I'm alive on the boundary of my own universe. Or I guess the angle I was pushing it on is we can get information about everything in the universe from its boundary. And that might be simpler. It might show us a sort of hidden core of things or an organizing principle that might help us solve problems we couldn't have solved otherwise. That's wacky stuff. I was going to say, it sounds philosophical and poetic that it's on the boundaries are the only ways in which to see sort of what we are existing within. That does sound good. Also a Kendrick Lamar line. It's very zen of you.

48:19It is. Maybe it's more Alan Watts. Yeah. This is from Farouk. Greetings. This is Farouk from Queens, New York. The question has been on my mind for the past couple of years regarding the nature of time. If time is measured by the displacement of atoms, but those atoms stop moving, does time still exist as a fundamental property?

48:39Neil deGrasse Tyson:Can I take a stab at this? Please. And you clean up my mess? So I think there are two ways you can reckon time. Maybe many, but two that I think of when I think about that question. One of them is in your own sort of world, you can sequence events. Now, this is not for every observer, but for you, you can sequence events to know what happened before what. Okay? So that's, in a sense, a time. You have a before and an after. But I can tell you this. If you have no thing that repeats itself, then you have no way to measure the passage of time. Wait, explain that to me. Earth rotates once a day, and it keeps doing it.

49:25Neil deGrasse Tyson:Earth goes around the sun once a year, and it keeps doing it. We have a day and a year. Okay? We got a clock. We got atoms that vibrate. Everything is repeating. The measurement of time is embedded in repeated phenomenon. So if you go to a world where nothing repeats, there would be no measurement of time. It doesn't mean there isn't time still existing, but you couldn't measure it in any meaningful way. Are we good with that, Laura? Yeah. No, I think you're saying that you agree with the questioner, which I think I would too. Yeah. In a totally static universe, that isn't a really meaningful question, right?

50:01If nothing's moving, if nothing's evolving, then yeah, you don't really talk about time. Well, okay, so let's get, take it another layer in.

50:10Neil deGrasse Tyson:If nothing's moving, everything is static. All I said was that you can't measure time. But you said time won't matter, which is surely true, because everything is the same at all times. If nothing changes, what do you care what time it is? But you still experience time. That's what I'm asking. So, is there still a reckoning of time if there's nothing to measure it? I mean, I think if nothing is changing literally, then even the measurement or perception of time doesn't mean much, right? One thing that we do know for our universe about time is that time, as you were alluding to in your answer, you were saying, you know, an individual person experiences time, we have a before and after.

50:51But there is no universal clock for our universe. We know that in special relativity, all across the universe, in gravitational fields, in different parts of the universe, people are going to measure time differently. Time is going to tick differently. So then you can say, yeah, like, what does that mean if this is a thing that's changing everywhere, right? What do we mean by, you know, this sort of fundamental notion of time? And there, what we know is that it's not just time, but it's particular combinations of space and time that the entire universe has to agree on. So it may not be pure time, but there is something that everybody has to agree on for universes that do have things moving.

51:28And that's given to us by special relativity. I love that. I do. Time ticks differently.

51:36Neil deGrasse Tyson:What? I know. And if nothing changes, you'd really have to ask, why do you give a shit about time at all? I mean, think about it. It's like maybe work on changing some shit. Okay. Oh, you're worried about time? I don't know. Why don't you clean up your mess? It's been like this forever. And then you break the symmetry of the universe, and then time begins. Now you've got your time. Because you cleaned your room. This is from David DeLeon. Greetings and salutations, Dr. Tyson and Dr. Anderson. David DeLeon, raised in Florida, writing out of Indiana. It may just be my own ignorance, but we as humans talk about dimensions in multiple ways.

52:17More often than not, I assume it is the physical. The physical three, length, width, height. Essentially representing up, down, left, right, forward, and back. Would it not be the most logical that the fourth dimension would be out and in, or quantum and cosmic? I often like imagining zooming out or in at unprecedented distances and winding up in a scene similar to that where the zooming started like a universe in quarks. Any thoughts? Again, thank you for all that you do. Big fan of all knowledge and interpretations of life. That's a good question. I would say it's a little different. But the sort of zooming out picture that the question is alluding to is a real thing in physics, and it matters a lot.

53:01And this has to do with several things. So the first is whether you expect all of the physics, let's be broad about it, to be the same at every distance scale or not. So if you were to say, you know, I measure something here in my little part of the universe to be this big. And now if we just, you know, scaled it up arbitrarily small or big, should all the laws of physics be the same? And we think that that isn't actually a symmetry of the laws of physics as we understand it. We think that the structure is different at different energy scales. That symmetry, if you had a scale where like length didn't matter like that, you could zoom in and out, up and down, and everything was the same.

53:37That's called a conformal symmetry in theoretical physics. And some things do use it in a really powerful way. So actually these string world sheets that we mentioned before, these little one-dimensional strings that are vibrating through space, those have a conformal symmetry. You should be able to scale that world sheet up and down, and it doesn't change how that world sheet behaves, which is really neat. But other physics, like the physics of the strong interactions and quarks, really does seem to be behaving on a different energy scale than gravitation. And this gets studied in things like quantum field theory a lot, where you try and say, if I'm writing down a physical theory, what regime of scales and sizes and energies should it be valid for?

54:15Neil deGrasse Tyson:So just to be clear, it's not that the laws of physics are different. It's that they manifest in different ways. Or the way that you describe them. The systems of equations and the descriptions that you have do change with those different scales. Okay, so we're not just zoomable. Yeah. Although, as we mentioned, string world sheets are, which is kind of cool. So some stuff is, some stuff isn't. We still like to be. It's still a fun idea. Yeah, thank you for putting it out there. Dear Dr. Tyson and Laura, this is Jonas William from NYC, just down the road. My question for you is, since string theory dualities are so hard to calculate in smooth space, could we use the sine vectors of oriented matroids to build a pixelated discrete model of space-time?

54:59Would stripping away the smooth geometry naturally solve the infinite singularities of quantum gravity? that's a great question and lots of people are actually thinking about that so people have hoped that there was some sort of fundamental little unit or building block like building up a big tiled floor by having lots of little tiles that you fit together maybe you could tile your way to a complete picture of space-time and there are several different types of physics that are exploring that so things like loop quantum gravity or something called causal dynamical triangulations try and do exactly that.

55:36They try and build quantum gravity through discretizing space time. And I'm not an expert on either one of these fields. These are not string theory, but they're different things that people are exploring. And I think it's a perfectly fair question. Does that solve the problem of quantum gravity? I would say the jury's still out. We haven't decided, but more power to people for asking the idea. And who knows, maybe Jonas, you can figure that out too. Even Neil's like, I don't know. This is... Let's see if we have one final big question that we can sink our teeth into here. All right? Keith from New York City.

56:10Dr. Anderson, is it necessarily true that dimensions are something that objectively exist in nature or are dimensions simply an organizing principle that we puny humans use to make sense of the universe? Are they features of reality or could they be emergent useful descriptions that arise from something deeper? Is it even possible that dimensions are not real in any sense, but are instead conceptual tools, much as we use imaginary constructs, orbital model of the atom, imaginary numbers, in physics and math? Thanks. That's a great question. I would say, yeah. I mean, most of the way that we describe the universe is a construct.

56:46So could dimensions just be a construct? Yeah. Certainly things move, and we can see the degrees of freedom of how things move in our universe. And so that's where you see that you can move forward, backwards, side to side, up and down, and those are different. But labeling them as dimensions, labeling them as different, that's just a tool for how we try and describe physics and make predictions. Just like things like a force, when you say something pushes on something else. That's a construct, too. Turns out a very useful one. But we don't measure forces, we just measure acceleration. So, yeah, I would say it could be viewed as a construct, but one that we think we can get a lot of mileage from.

57:25Neil deGrasse Tyson:Mm. Because that reminds me in some branches of quantum physics that we don't understand, we just like the hidden variables hypothesis. It's like they just assert it because it allows you to think classically about the problem, whether or not it's actually true. But there have been occasions in the past where people just, it pulled something out of their ass to just kind of account for it, and it turned out to be true. There are a couple of occasions such as that. And some things where no matter how many hidden variables you have, you still can't get it right, like in quantum mechanics. There's theorems that say no matter how many extra degrees of freedom you have, could you erase that quantum weirdness, that uncertainty, the probabilistic nature of quantum mechanics?

58:12And the answer is no. You could have an infinite number of hidden variables, degrees of freedom, doesn't help.

58:17Neil deGrasse Tyson:Fundamental to it. Well. I think we learned some stuff here today. These were great questions. Your audience is really cool. No, they're my people. We got good people here. And global. This is an international crew here. People want to know, you know? Inquiring minds want to know. They do. Absolutely. Inquiring Patreon members want to know. So where can we keep in touch with your work? Do you have a website? I have a website. I am not on social media, which is a bit embarrassing. I'm a little bit of a Luddite. That is a dimension you don't need to explore. I think you have enough on your plate.

58:54I'm a little bit occupied otherwise right now. Yeah.

58:57Neil deGrasse Tyson:Okay, it's not social media, but you have a website. Which is it? I'm Virginia Tech. If you just search my name and physics, you'll probably find me. All right. Well, Laura, thank you. Thank you. For sharing your cosmic expertise with us, living completely in the gaps of my knowledge. Well, thank you so much for having me. This was a great pleasure. And yeah, I think your audience members are awesome. I'm delighted to have a chance to chat. And we think so, too. All right, dude. Neil, thank you. Good to have you always. Always good. This has been another episode of StarTalk. I'm Neil deGrasse Tyson, as always, bidding you to keep looking up.

59:49Hey, this is Jeff Lewis from Radio Andy. Live and uncensored, catch me talking with my friends about my latest obsessions, relationship issues, and bodily ailments. With that kind of drama that seems to follow me, you never know what's going to happen. You can listen to Jeff Lewis live at home or anywhere you are. Download the SiriusXM app for over 425 channels of ad-free music, sports, entertainment, and more. Subscribe now and get three months free. Offer details apply.

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