Cosmic Queries – Single Electron Universe with Charles Liu

Could the universe be composed of a single electron? Neil deGrasse Tyson and co-hosts Chuck Nice and Gary O’Reilly answer grab-bag questions about the multidimensionality of time, quantum chromodynamics, gluons, tachyons, and more with astrophysicist Charles Liu.

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:00Neil deGrasse Tyson?

  Coming up on StarTalk Special Edition, it's a cosmic queries. Oh, yeah. And I've got with me our geek in chief, Charles Liu, and we tackle really deep quantum questions of the cosmos, one of which might be, could the entire universe be composed of a single electron moving forward and backwards through time? All that and more coming up.

• 0:29Neil deGrasse Tyson?

  Welcome to StarTalk, your place in the universe where science and pop culture collide. StarTalk begins right now.

• 0:42Neil deGrasse Tyson?

  This is StarTalk Special Edition. I'm your host, Neil deGrasse Tyson. I got with me Chuck Nice, Chuck. Hey, hey, hey, Neil. All right, all right. And of course, Gary O'Reilly.

• 0:54Gary O'Reilly?

  Hi, Neil.

• 0:55Neil deGrasse Tyson?

  And Charles, welcome back to StarTalk.

• 0:57Charles Liu?

  Always a pleasure. Thank you so much.

• 0:59Neil deGrasse Tyson?

  Totally in the family, totally in the family.

• 1:01Charles Liu?

  I feel like I'm in the family. I'm honored. Thank you so much.

• 1:04Neil deGrasse Tyson?

  Excellent. Well, let's go. We solicited questions for this and we got like 140 questions.

• 1:10Charles Liu?

  Dang.

• 1:10Neil deGrasse Tyson?

  And we will, yeah, I know, right? So that would be a

• 1:12Gary O'Reilly?

  That's, that's, that's, that's the point. We stopped counting.

• 1:15Neil deGrasse Tyson?

  That's, that's a question every 12 seconds. So Charles, get your soundbite mode ready, but we don't want to lose depth and nuance. Charles and I have extraordinary overlap in our general scientific expertise.

• 1:28Charles Liu?

  Mm hmm.

• 1:29Neil deGrasse Tyson?

  But Charles extends beyond that in ways that render unique participation in cosmic queries. So

• 1:39Charles Liu?

  And you extend the other way, too.

• 1:41Neil deGrasse Tyson?

  What do you mean the other way? There's no other way. There's no way.

• 1:44Charles Liu?

  There are many ways to extend in the universe.

• 1:47Neil deGrasse Tyson?

  Gary, what you got?

• 1:48Gary O'Reilly?

  Let's start with Fabiola Horvath from Hungary. She does name the place which she's from, but I will not be attempting to mangle

• 1:57Charles Liu?

  Oh.

• 1:58Gary O'Reilly?

  the, the language.

• 1:59Neil deGrasse Tyson?

  Okay, give it to Chuck so he can mangle it.

• 2:01Charles Liu?

  Yeah, well.

• 2:02Gary O'Reilly?

  All right. There's an S, there's a Z, there's an E, there's a K, there's an E, there's an S and F, E, H, E, R, V, A, R. And there's lots of little ticks above.

• 2:11Charles Liu?

  Yeah, the, the ticks make all the difference in Hungarian. What a marvelous language it is, by the way. It's, it's the Magyar sort of origin is completely different from like Latin based languages and so forth.

• 2:24Neil deGrasse Tyson?

  We do that.

• 2:25Charles Liu?

  By the way, if you want to say "bless you" after somebody sneezes in Hungarian, this is probably the one word I can pronounce in Hungarian. It's "egyel szegere."

• 2:36Chuck Nice?

  That's too much.

• 2:38Charles Liu?

  No, five syllables. It's like "to your whole health."

• 2:42Chuck Nice?

  Yeah, we just say "bless you," and you know, but "egyel szegere," that sounds like the actual sneeze itself.

• 2:50Charles Liu?

  Instead of-

• 2:50Chuck Nice?

  That sounds like you sneezed and then I sneezed back. That's what that sounds like.

• 2:56Charles Liu?

  Yes, well, you have to be careful because if you mispronounce it, instead of saying "to your whole health," you wind up insulting the person's anatomical parts. When you said "egyel szegere" that way, you did great, but you gotta be careful because if you do it wrong, someone will like slap you.

• 3:10Chuck Nice?

  If you say it wrong, what exactly are you saying?

• 3:14Charles Liu?

  You are making comments about their posterior.

• 3:18Chuck Nice?

  Well, that could be a good thing sometimes, you know what I mean? I mean, like, sometimes, you know, making a comment about somebody's posterior is very positive.

• 3:31Gary O'Reilly?

  Next week on Scientific Babel, we'll be traveling to other countries to learn how to insult the locals.

• 3:40Gary O'Reilly?

  Fabiola, we are gonna get to your question because I think it's a great question. Is it true that every single electron in the universe is the same one? Can you explain this theory, please, even if not true? Many thanks.

• 3:55Neil deGrasse Tyson?

  Charles, this was once explained to me by Richard Gott,

• 4:00Neil deGrasse Tyson?

  back when I was at Princeton, and it blew my frickin' mind.

• 4:04Charles Liu?

  We have to give you this because the person who came up with this idea is another Princeton great in the field of science, John Wheeler.

• 4:12Neil deGrasse Tyson?

  John Wheeler?

• 4:12Charles Liu?

  Yeah, the story was that John Wheeler told this to Dick Feynman at Caltech, another giant.

• 4:18Neil deGrasse Tyson?

  Other people call him Richard Feynman, by the way.

• 4:20Charles Liu?

  Yeah.

• 4:21Neil deGrasse Tyson?

  Richard Lou, Dick.

• 4:22Charles Liu?

  Sorry.

• 4:23Neil deGrasse Tyson?

  Well, it's like Isaac Newton, I call him Ike, you know.

• 4:30Charles Liu?

  Richard Feynman tells the story in his work, he wrote a lot of course about physics, about this conversation that he had with John Wheeler about the one electron universe. But I need you to tell it because Rich Gott also...

• 4:44Neil deGrasse Tyson?

  No, no, no, I...

• 4:46Charles Liu?

  Rich Gott, one of the greatest, again tremendously interesting physicists, astrophysicists even specifically.

• 4:53Neil deGrasse Tyson?

  Okay, so here, I'll...

• 4:54Charles Liu?

  Go for it, go for it.

• 4:55Neil deGrasse Tyson?

  I'll attempt it and then you fill in the gaps, okay?

• 4:58Charles Liu?

  Okay, okay.

• 4:58Neil deGrasse Tyson?

  So, what we know for sure is that every electron we've ever measured is exactly the same.

• 5:08Charles Liu?

  The same, okay.

• 5:09Neil deGrasse Tyson?

  There is no property about one electron that is not precisely represented by other electrons. So, we have to ask, does that require an explanation? We might ask. Or do we just allow there to be all these electrons in the universe, made in whatever way they've got made, and all exactly identical? So, the question was posed, maybe they're look identical because they are the same single electron. How might that work?

• 5:44Charles Liu?

  Yes.

• 5:45Neil deGrasse Tyson?

  Please, yes, Al.

• 5:46Charles Liu?

  Okay, right, now we're getting to the good stuff. Yeah. Because right now, you sound like every person describing a black man leaving the scene of something.

• 5:55Neil deGrasse Tyson?

  Oh. All the same.

• 6:00Charles Liu?

  Yeah, I'm just saying, I thought it was him.

• 6:05Neil deGrasse Tyson?

  So antimatter, which was predicted by Enrico Fermi, if memory serves, within a couple of years, it was discovered. We discovered the antimatter particle to the electron, which we call the positron. Okay. And that's weird, because all the properties are like the inverse of the normal particle. Is there any way to understand this? And it turns out, one can interpret antimatter in certain situations as ordinary matter moving backwards through time.

• 6:36Charles Liu?

  Whoa, wow.

• 6:38Neil deGrasse Tyson?

  Okay, it solves some equations regarding antimatter. So, if you allow that, then you can ask the question, if one electron goes forward in time and then reverses going backwards in time...

• 6:55Neil deGrasse Tyson?

  And it just keeps doing that. Then wherever you are in time, you will see this record of electrons moving forward and backward in time in the instant that you make the observation. No, no, you have to pick me up from

• 7:12Charles Liu?

  You did it.

• 7:12Neil deGrasse Tyson?

  Bail me out here. Where I'm a little fuzzy is, are some of the electrons we're looking at actually ones going backwards in time that we happen to catch in the moment we measure them, thinking they are ordinary electrons going forward in time?

• 7:26Charles Liu?

  Probably not. At this point, the reason we say probably not is, well, aside from the fact that we haven't been able to prove that experimentally.

• 7:36Neil deGrasse Tyson?

  Wait, wait, wait, wait, don't, don't disprove it yet.

• 7:38Charles Liu?

  Okay.

• 7:38Neil deGrasse Tyson?

  Just give me the full hammer of the explanation that accounted for every electron being identical, and then we can debunk it afterwards.

• 7:46Charles Liu?

  Right. Well, it has to do with relativity, right? Because you're moving forward and backward in time, being able to think of world lines in special relativity of particles. Now, if you imagine that things could just keep going past, present, past, present, back and forth, back and forth, back and forth, but you do it almost infinite number of times, then every time you measure an electron, it's the same one, but just at a different moment in time, it has a different part of its world line.

• 8:16Neil deGrasse Tyson?

  Oh.

• 8:18Charles Liu?

  So it's, it's always coming backward and forward in time, right?

• 8:21Neil deGrasse Tyson?

  Okay, but wait, but so there's the electron that's in my experiment, but now I look out the window and I see a tree. That tree has electrons in it. So the electron that's in the tree and the electron that's in my experiment is the same electron, just on a different world line that's crossing my present in a different location.

• 8:36Charles Liu?

  Yes. Beautifully said.

• 8:40Neil deGrasse Tyson?

  Ooh.

• 8:41Chuck Nice?

  That sounds crazy. I'm just gonna be honest. That sounds insane, okay?

• 8:49Charles Liu?

  Well, a lot of things that sound insane when they're originally proposed turn out to be indeed insane.

• 8:55Chuck Nice?

  Not that insane.

• 8:57Charles Liu?

  A lot of the stuff, though, you have grains of truth from which reality can then be further explained by it.

• 9:03Chuck Nice?

  You had me up until the electrons going back and forth in time on a different world line in different places at the same time.

• 9:11Neil deGrasse Tyson?

  Yeah.

• 9:12Chuck Nice?

  That

• 9:13Neil deGrasse Tyson?

  Because wait, wait, because Chuck, the whole point of a world line is

• 9:16Chuck Nice?

  Is it's yours. It's yours.

• 9:18Neil deGrasse Tyson?

  Wait, wait, wait, hold on.

• 9:19Chuck Nice?

  It's, okay, go ahead.

• 9:20Neil deGrasse Tyson?

  Time is just one coordinate.

• 9:21Chuck Nice?

  Right.

• 9:22Neil deGrasse Tyson?

  So. Two world lines can exist in the same time, but not in the same place. That's why you can cross the street.

• 9:30Chuck Nice?

  Right, exactly.

• 9:31Neil deGrasse Tyson?

  And not get hit by a truck. In that case, you're in the same place, but at different times. Okay?

• 9:37Chuck Nice?

  Okay.

• 9:38Neil deGrasse Tyson?

  And when world lines actually intersect, are you in the same place at the same time? And so, all these other world lines, there's a different world line in an infinite number of passages through our universe. So our universe would be the construct of, not an infinite, you can probably number them, but a hugely high number of passages of a single electron.

• 10:00Chuck Nice?

  Okay, so do any of those world lines ever intersect at any time?

• 10:05Neil deGrasse Tyson?

  Well, we can smash two electrons together.

• 10:08Chuck Nice?

  Okay, so then how's that the same electron?

• 10:12Chuck Nice?

  Nice, for the win!

• 10:16Chuck Nice?

  That's what I was saying, it's insane!

• 10:19Neil deGrasse Tyson?

  Charles, get me out of that one.

• 10:21Charles Liu?

  No, it's because you're traveling backwards and forwards in time. If Wheeler was correct in his hypothesis, because you're going forward and backward, you're literally collapsing, or crashing, some, one of them that's going forward with one that's going backward, creating an annihilation, antimatter basically, a positron kaboom kind of thing. So the electrons, if one electron hits the other, they're not actually hitting like we think of like two rocks hitting each other, but their wave functions are interacting in a specific way. So you see, it was an imperfect hypothesis or model to begin with, it's true, but you squirm your way out of it using quantum physics. And you, and the idea that time is this dimension that you can go backwards and forwards, it's

• 11:06Charles Liu?

  the melding of special relativity and quantum physics, electrodynamics.

• 11:14Chuck Nice?

  Is it the same electron with different reference points? Is that the deal?

• 11:20Charles Liu?

  You could think of it that way.

• 11:22Chuck Nice?

  Okay.

• 11:22Charles Liu?

  That's, it's not a, it's not a wrong way to think about it.

• 11:25Chuck Nice?

  Okay, all right, okay.

• 11:26Neil deGrasse Tyson?

  But the point is, Charles, the idea taking to its limits could not be... Verified. The idea that antimatter is regular matter moving backwards through time does have merit.

• 11:38Charles Liu?

  Yes. And it had so much merit that Richard Feynman wound up putting it in his way of thinking about particles and the whole quantum electrodynamics.

• 11:48Neil deGrasse Tyson?

  And his way of thinking is the way of thinking.

• 11:50Charles Liu?

  At the moment, that's right. Okay.

• 11:52Neil deGrasse Tyson?

  It's not just, oh, he's got his way and nobody's got their way.

• 11:54Charles Liu?

  We don't call them Feynman diagrams for nothing.

• 11:56Gary O'Reilly?

  So if I want to know more about this, because my head hurts right now, and once that's passed, I would want to know more about it, where do I go?

• 12:05Charles Liu?

  Dr. Richard Gott.

• 12:07Gary O'Reilly?

  Mm hmm. Will he tell me everything I need to know?

• 12:11Charles Liu?

  Not to say too much about this gentleman, but would you grieve, Neil, that Richard Gott might be the most interesting person to listen to for a long time? If you just had a lot of time to sit there.

• 12:25Neil deGrasse Tyson?

  I've already, I've already thought that through. So I say to myself, if I'm in some Spanish Inquisition prison, shackled to the wall, and there's one person next to me for years, just because I'm a prisoner there, who would I choose? I would choose Rich Gott.

• 12:47Charles Liu?

  Yeah, it's a fun thing to think about.

• 12:50Neil deGrasse Tyson?

  And they say, who do you want in a foxhole with you? Would not be Rich Gott, because I'd be too distracted listening to his story. We would just get shot by any, I would say, hey, come listen to this. Before you shoot me, come listen to this story.

• 13:02Charles Liu?

  If I had just some time to sit around and just listen to someone talk about cool things and explain weird ideas in, in a really understandable and fun way, Richard Gott would be definitely one of them.

• 13:14Neil deGrasse Tyson?

  That's one of the reasons why one of my books titled Welcome to the Universe.

• 13:19Charles Liu?

  Ah, that's right.

• 13:21Neil deGrasse Tyson?

  It's basically. A textbook intended for you to read, not for you to use in a classroom. E I N N and Michael Strauss. Yes, another wonderful, wonderful. Intro astrophysics. Yeah. And we each have a third of the content of that book. And you get to see his contribution to cosmology and why it's weird, wacky and fun. Just in that. So I knew it when I was a prince and then we were co authors. Yeah, they're great.

• 13:50Chuck Nice?

  Well, I have spent an inordinate amount of time with Joel Gott. And I find that the more time that I spend with Joel Gott, the more interesting.

• 13:59Neil deGrasse Tyson?

  That is a wine, for those who don't know.

• 14:01Chuck Nice?

  Yeah, for those of you who don't know, Joel Gott is wine.

• 14:05Neil deGrasse Tyson?

  It's a California wine.

• 14:06Chuck Nice?

  Yes, it is.

• 14:08Neil deGrasse Tyson?

  Plus, Richard Gott has a book called Time Travel in Einstein's Universe. Oh. Which are all the ways that you can use relativity to engage not only forward, but also backwards time travel. So. I have a vague memory of him holding up a glass model. Oh, that was different. Yeah. That was a universe that creates itself, which removes the need to have an origin event. Wow. It looks like a fugal horn or something.

• 14:51Speaker 04

  Hello, I'm Vicky Barok Allen and I support StarTalk on Patreon. This is StarTalk with Neill Grass Tyson.

• 15:07Neil deGrasse Tyson?

  Well, let's get to the next question.

• 15:08Chuck Nice?

  All right.

• 15:09Neil deGrasse Tyson?

  That was not a fast answer. Now we're down 139 questions.

• 15:13Chuck Nice?

  All right, so let's move on. This is from Jay Swami, who says, hello, Dr. Tyson, Dr. Ludelord, nice, and Gary. Jay Swami from San Jose, California, here. Hey, Dr. Tyson, you always say we are prisoners of the present in perpetual transition from an inaccessible past to an unknowable future. The quote often resonates with me. Is time itself multidimensional? Could there be a higher dimension of a time beyond our single arrow of time that we experience? This concept left me puzzled, but curious about the possibility that time might not be one dimensional. Could there be more than one dimension of time, which is accessing

• 15:56Chuck Nice?

  the one dimension that is available to us? Is this a possibility according to current scientific understanding?

• 16:04Neil deGrasse Tyson?

  So I have a cop-out answer.

• 16:06Chuck Nice?

  Uh-oh.

• 16:08Neil deGrasse Tyson?

  I don't see anything preventing time existing in more than the single dimension that we experience. I would just have no understanding of what that would mean.

• 16:21Chuck Nice?

  Right.

• 16:23Neil deGrasse Tyson?

  Because when we think of coordinates of like X, Y, and Z, you can move in one, two, or all three coordinates at once, right? That's moving in the grid of the, you know, in the Cartesian grid. And if I had a time grid, it means I can go in time this way, but not that way. And would that take me out of my, I don't know. I don't know what that would mean.

• 16:47Gary O'Reilly?

  So how does this weave back into the single electron, going backwards and forwards?

• 16:52Charles Liu?

  You don't need more than one dimension of time to have the single electron to be true.

• 16:57Gary O'Reilly?

  I'm just wondering, does it all kind of find itself weaving itself together?

• 17:02Charles Liu?

  Well, time is a funny dimension, right? If you look at the way that general theory of relativity shows time, it is a dimension, just like length, width, and height. But the way the relativity is structured.

• 17:17Charles Liu?

  The element of time in the metric is negative, as opposed to the others which are positive.

• 17:25Neil deGrasse Tyson?

  Okay, what you're saying is time is not treated, yes, it is a dimension, but it's not treated the same way.

• 17:30Charles Liu?

  Right.

• 17:31Neil deGrasse Tyson?

  There's a negative sign where X, Y, and Z have a positive sign.

• 17:34Charles Liu?

  That's right.

• 17:35Neil deGrasse Tyson?

  So that already admits that there's something different going on there.

• 17:38Charles Liu?

  That's right. And so I would say that, Jay, your question might be most easily thought of in the concept of compactified dimensions. A lot of times, right now, we are thinking in string theory or in other ways of thinking about space and time, that maybe length, width, and height themselves have dimensions tied in with them, each of them much smaller than the Planck length or the detectable length, but they're kind of nestled within one another, right? I think Neil used-

• 18:10Neil deGrasse Tyson?

  Is there a way to unfold them?

• 18:12Charles Liu?

  Possibly.

• 18:13Neil deGrasse Tyson?

  Can they be unfolded?

• 18:15Charles Liu?

  Well, right now, we can't, right? But the example, I've heard Neil use this before, right? If you go right up against the Alaska Pipeline, then it looks like it has length, width, and height. But then if you drive like 10 miles away, then it just looks like a single line. The other dimensions are there, but we couldn't see them unless we zoomed in really close. So imagine if you were looking at the time dimension or trying to figure out something traveling in time, but you were able to focus to such a fine degree of time that you could actually see other time kind of curled in there, then you would have this extra-rich dimension. It might not affect causality in our universe at our size scales and time scales,

• 18:59Charles Liu?

  but it would still be another time dimension.

• 19:02Neil deGrasse Tyson?

  But what would it mean?

• 19:06Charles Liu?

  I don't know. Look, you know, that phrase of yours about being prisoners of the present is very true, but I prefer to think of it a little bit differently. Same concept, but with a different attitude going toward it, as expressed by Master Oogway in the classic movie Kung Fu Panda, which I will paraphrase, saying, "Yesterday is history. Tomorrow is a mystery." But today is a gift, and that's why it's called the present.

• 19:37Chuck Nice?

  Mm hmm. Oh, okay. That's, that's, I gotta tell you, that's very deep for a Pixar movie.

• 19:45Charles Liu?

  It wasn't Pixar, actually.

• 19:46Chuck Nice?

  Oh, I don't know.

• 19:47Charles Liu?

  It was an animated movie. Yeah.

• 19:49Chuck Nice?

  Yeah.

• 19:50Charles Liu?

  But, but it's the same idea, right, Neil? We experience the present at the moment simply because of the way time is structured.

• 19:57Chuck Nice?

  So, wait, is there a dimension, higher, higher dimension, where time is not experienced as a present, or a past, or a future? Maybe it's just experienced, so it just is. And at that point, you're able to see anywhere on that timeline, so you're no longer a prisoner.

• 20:21Neil deGrasse Tyson?

  Yeah, that's the theme in Kurt Vonnegut's novel Slaughterhouse Five, where the protagonist is in his backyard, and he's lifted up by aliens, which I always want to have happen to me. When I go to anybody's backyard at night, and I look up.

• 20:35Chuck Nice?

  Right.

• 20:35Neil deGrasse Tyson?

  I want to be abducted by aliens.

• 20:37Chuck Nice?

  Yeah, but you, no, you know, I mean.

• 20:39Gary O'Reilly?

  No, I know where that, then you chuck.

• 20:40Chuck Nice?

  Yeah, you know where that's going. Yeah, we don't want to, you know the next step. That's important.

• 20:45Neil deGrasse Tyson?

  Minus the anal probe.

• 20:46Chuck Nice?

  Okay, all right, okay, okay, all right, okay.

• 20:52Neil deGrasse Tyson?

  We pre-agree, no anal probe.

• 20:55Charles Liu?

  Okay, that's another dimension to explore.

• 20:58Neil deGrasse Tyson?

  So, he gets put in this sort of hyper-prison, and, but it's outfitted with everything he likes and cares about, and he can see his entire timeline from birth to death.

• 21:09Chuck Nice?

  Oh.

• 21:10Neil deGrasse Tyson?

  And he can access any point in that timeline.

• 21:13Chuck Nice?

  Oh.

• 21:13Neil deGrasse Tyson?

  And, and so it explores how constricted our vocabulary is, because you can say, well, when were you born? And his answer becomes, I'm always.

• 21:22Chuck Nice?

  I'm born.

• 21:23Neil deGrasse Tyson?

  Yeah.

• 21:24Chuck Nice?

  Yeah.

• 21:24Neil deGrasse Tyson?

  And when you, I'm always dying.

• 21:26Chuck Nice?

  Right.

• 21:26Neil deGrasse Tyson?

  When were you, I was always there.

• 21:28Chuck Nice?

  I'm always, right.

• 21:29Neil deGrasse Tyson?

  And so he can re-enter the timeline and re-experience it with very limited memory of having been there before. That was just a plot point that they needed.

• 21:39Chuck Nice?

  Right.

• 21:39Neil deGrasse Tyson?

  But the point is, that was my first encounter, with time being a dimension that you can enter at any point, in the same way you walk into a room, and you can access any point. In the X, Y, Z, the height, the width, or the depth of the room at will. So if you can do that with time, I mean, that's quite a, you, you need a higher dimension to exit that and come back in. And come back in.

• 22:03Charles Liu?

  So imagine coming up from, here's your time dimension line, and you're watching it from way up here, kind of like you're miles away from the Alaska Pipeline time. And then you can sort of see it. Now, the pipeline is there, and it's always existing because that's the time dimension. But imagine if the oil in the pipeline had, was just starting to flow, and it hadn't filled up a further part of the pipeline. That's the future, where the dimension has not yet been completely filled, and that might explain causality. Whereas in the Slaughterhouse-Five idea, everything's already been filled. And you just don't know. And once you get closer, you can see it, and you can reinsert yourself.

• 22:40Neil deGrasse Tyson?

  So what you're saying is, a variant on this entire timeline in full view, is you have the full view of everything that's already happened.

• 22:47Charles Liu?

  Yes.

• 22:48Neil deGrasse Tyson?

  And so you are then moving forward in your timeline, creating the future as you go along.

• 22:55Charles Liu?

  Correct.

• 22:55Neil deGrasse Tyson?

  So that the future remains not only a mystery, it's indeterminate.

• 23:00Charles Liu?

  Yes.

• 23:01Neil deGrasse Tyson?

  That's right.

• 23:01Charles Liu?

  Interesting.

• 23:02Neil deGrasse Tyson?

  That'd be a variant on it.

• 23:03Gary O'Reilly?

  All right, I think we've just answered the next question.

• 23:06Neil deGrasse Tyson?

  Oh, okay.

• 23:07Gary O'Reilly?

  However, let me read it and see if this is actually factual. "G'day" by Jared. Jared's in Down Under.

• 23:13Neil deGrasse Tyson?

  You think?

• 23:14Gary O'Reilly?

  And he says, and he caveats that way, "Is there a down?"

• 23:19Neil deGrasse Tyson?

  He's at the center of the Earth, but going. Right.

• 23:22Gary O'Reilly?

  "My question is about the illusion of time. I often wonder if time is not a direction, but rather a ledger or book that records the state of everything. If nothing changed, time would not pass. If you could rearrange objects or particles, you could return to any state or moment in time, be it past or future. Is it possible that time doesn't speed up or slow down, being only a book, but rather objects have a variable rate of change based on gravity and speed? Thank you, Starlords," which I think applies to.

• 23:52Gary O'Reilly?

  So you three, certainly Starlords, that's definitely an up in the ranking. Yes. Have you answered that question already?

• 23:59Neil deGrasse Tyson?

  Well, no, no, but so, so, Charles, I like that question because it's asking. It's first admitting.

• 24:06Chuck Nice?

  Yeah.

• 24:06Neil deGrasse Tyson?

  Maybe it's not that there is no time if nothing changes. There's no measurement of time.

• 24:12Chuck Nice?

  Yeah, yeah.

• 24:13Neil deGrasse Tyson?

  Right? So if the whole universe were static and I bring in a clock that does have some periodicity, I can measure the flow of time, even though it won't matter to anything else in the universe, only to the clock itself.

• 24:24Chuck Nice?

  To the clock, that's it.

• 24:25Charles Liu?

  Yeah, if you have the structure there, regardless of what it does, right? It's true, not from the physics point of view, but from like the human experience point of view. There are plenty of people who advise that time is a resource, right? We as humans have only a certain number of hours in the day. How do we use that time most effectively?

• 24:45Neil deGrasse Tyson?

  Time is money.

• 24:46Charles Liu?

  Yeah, those kinds of things, right? So there's different ways to think about time in that sense. And then the idea of time as an illusion is if everything that humans invent or think about is an illusion compared with the actual physics of space and time, then what you can say is that the faster you move through space, the slower you might move through time. Your experience of time, the time is just there and your experience of it varies depending on your velocity through space.

• 25:18Chuck Nice?

  So in that case, time becomes like a lake and we're all just swimming in it.

• 25:23Charles Liu?

  Right.

• 25:23Chuck Nice?

  Yeah.

• 25:24Charles Liu?

  And how much do you wish to drink of it at a time? Do you sip from a straw or do you try to gulp from a fire hose?

• 25:30Chuck Nice?

  Well, look at you getting all damn.

• 25:34Neil deGrasse Tyson?

  Man, getting all poetic with stuff.

• 25:36Chuck Nice?

  Yeah.

• 25:37Charles Liu?

  I tried to drink from a fire hose once. It was fun.

• 25:39Neil deGrasse Tyson?

  It's hard.

• 25:40Charles Liu?

  Yeah, that's hard.

• 25:40Neil deGrasse Tyson?

  Knock your head off.

• 25:41Chuck Nice?

  I'm just gonna tell you, as a black man, I was something I've never had a problem with.

• 25:47Neil deGrasse Tyson?

  No, it's something you're not going to attempt.

• 25:49Chuck Nice?

  Exactly.

• 25:50Neil deGrasse Tyson?

  It's got bad vibes.

• 25:51Chuck Nice?

  That's what I mean when I said not a problem with, like, I've never been curious.

• 25:55Neil deGrasse Tyson?

  Well, yeah, you know, exactly.

• 25:56Charles Liu?

  To be fair, it wasn't aimed at me, it was sideways.

• 25:58Chuck Nice?

  Oh, okay, cool.

• 25:59Neil deGrasse Tyson?

  Still.

• 26:00Charles Liu?

  Still.

• 26:01Neil deGrasse Tyson?

  I'm not sticking my head in front of a fire hose. It's not got bad vibes. So let me make two factual statements, I think. In a universe where nothing. Is periodic. There can be no measurement of time. All you can reckon is a sequence of events from your own perspective. You can have a before and an after, but you can have no measurement of what occurs between them.

• 26:26Charles Liu?

  You can figure out entropy. If you knew what the total entropy of the universe was.

• 26:31Neil deGrasse Tyson?

  You have an entropy clock.

• 26:33Charles Liu?

  Yeah, yeah. As a function of how disordered the universe is. If you believe the historical arrow of time goes from low entropy to high entropy.

• 26:41Chuck Nice?

  High entropy.

• 26:42Neil deGrasse Tyson?

  It's not a belief, it just is.

• 26:44Chuck Nice?

  Yeah, we have a clock like that. It's the countdown to the end of the world through climate change.

• 26:51Neil deGrasse Tyson?

  How's that coming along, Jack?

• 26:54Chuck Nice?

  Quickly. Not looking good.

• 26:56Neil deGrasse Tyson?

  So, all right, we got more here. Gary, what do you have?

• 26:59Gary O'Reilly?

  All right, let's go with Isaac Kinsey. Hello, Dr. Tyson, Dr. Lou, and Lord Nice. My name is Isaac from Indianapolis. My question is about quantum wave fields. All right. Is it possible to detect quantum particles or quantum wave fields that don't interact with gravity or the electromagnetic wave field? Up to you. Here we go.

• 27:22Neil deGrasse Tyson?

  And Charles, you've just written a book about the quantum. What a nicely timed question for that. Why don't you look at your book just in time for this question?

• 27:33Chuck Nice?

  How much did you pay Isaac to slip this question in at this very opportune moment?

• 27:38Charles Liu?

  Well, you know, I was able to observe the timeline from a distance and saw that this was happening. And so I've inserted myself into the time.

• 27:45Neil deGrasse Tyson?

  To remind our audience, you're author of a couple of books in this series. Like explainer books, very accessible, very dip in-able, if I remember correctly. The title of this one is what?

• 27:57Charles Liu?

  This one is called The Handy Quantum Physics Answer Book.

• 28:00Chuck Nice?

  Ooh.

• 28:01Neil deGrasse Tyson?

  Handy Quantum Physics. Said no one ever before.

• 28:06Chuck Nice?

  Yeah, you know, I liked your other one, too, The Handy Heart Surgeon Book.

• 28:11Charles Liu?

  No, no, the first one in the series was the Handy Astronomy Answer Book that I wrote, and then the second one was the Handy Physics Answer Book. And this one is focusing in on quantum physics, because the physics book, we could only glance at the surface of any specific area. But quantum physics itself is so much fun. Now, everyone should know that I do not do research on quantum physics itself, although I use it in all of my science all the time. And I wanted to, for myself and for anybody else, be able to explain basic ideas of quantum physics, which feels so mysterious and unknown, but actually is all around us on a daily basis.

• 28:50Charles Liu?

  And so it's not an attempt to sort of decipher the deepest mysteries of quantum physics, but the idea of just talking about how cool it is and what we know already and what we're still thinking about.

• 29:01Neil deGrasse Tyson?

  Yeah, in our field, we are formally trained in quantum physics, because it shows up and it's like a necessary thing you gotta deal with. But we don't spend our living days questioning the philosophical foundations of it. Does it work? Give it to me, I'm gonna use it.

• 29:17Charles Liu?

  Right, but it's fun, right? As we've had many of these questions in this particular episode, you know, that's very much deeply involved in our imaginations and our questions. And so talking about, giving the framework of the normalcy of quantum physics gives us the opportunity to think more deeply about the abnormalities, shall we say, of quantum physics. So yeah, it's kind of fun. It's a neat book, I enjoyed writing it.

• 29:42Neil deGrasse Tyson?

  Okay, so how about that question? Can you measure the wave field without it interacting with electromagnetic energy?

• 29:50Charles Liu?

  Or gravity. Yes, and we already have. There is a force field called the strong nuclear force, right? Which is neither gravity nor electromagnetism. The particles in there are gluons, right? They are massless, and their kind of charge is known as color charge. And they are the particles, called bosons, that do not interact directly with the electromagnetic field or the gravity field.

• 30:24Charles Liu?

  It has its own field. It's the strong nuclear field. Or quantum chromodynamics is the sort of semi-formal way of talking about its theory. So the answer is yes, great question, and there's a lot of cool work going on about gluons.

• 30:42Chuck Nice?

  And why a color field with the word chromo in there as well? So why color field?

• 30:51Neil deGrasse Tyson?

  It's physicists are racist and they...

• 30:57Charles Liu?

  Well, the colors are red, green, and blue.

• 31:01Neil deGrasse Tyson?

  The yellow particle, the red particle, and the black particle.

• 31:06Charles Liu?

  No, we wanted to express as physicists that there was a thing that was like charge, but wanted to make sure that no one confused it with electric charge being positive or negative.

• 31:18Chuck Nice?

  Gotcha.

• 31:19Charles Liu?

  This kind of charge, color charge, right, as three, right? Red, green, and blue, by coincidence, RGB. Yeah, and so there are eight types of gluons. All right, you might think that there are nine because three times three is nine, but it turns out that one of them is degenerate with another. So, yes, insert your own joke here. Physical degeneracy and all that, right?

• 31:43Chuck Nice?

  Hey, little gluon!

• 31:49Charles Liu?

  So I called it quantum chromodynamics to distinguish it from quantum electrodynamics. And it's a neat field. It's only contained within this little tiny environment within subatomic particles. But it's so important because, for example, we know that if you add up the mass of the quarks that make up a proton, you get much less than 100% of the mass of a proton. So all the rest of that mass is in the form of the energy that the gluons holding this thing together has.

• 32:26Neil deGrasse Tyson?

  And gluons are massless. So the mass you're measuring is contributed by their energy.

• 32:32Charles Liu?

  The E equals mc squared conversion. And it may well be, although this has not yet been confirmed yet in an experimental way, that... The gluons and the quarks may be moving back and forth in an electron, changing their existence and their states. It's almost like there are valence quarks and then there are dynamical quarks, I don't remember the exact name, that kind of slide back and forth and become gluons and non gluons and quarks and anti quarks. A proton, as stable as it is, as much as it is the bedrock of all matter that we understand it, is still very possibly a dynamic and fascinating object.

• 33:12Charles Liu?

  And this quantum chromodynamics and this kind of interaction with the neither the gravitational nor the electromagnetic fields is what produces this fascinating physics.

• 33:23Neil deGrasse Tyson?

  All right, let me back up here.

• 33:24Charles Liu?

  Damn.

• 33:25Neil deGrasse Tyson?

  So if you

• 33:26Charles Liu?

  That's wild.

• 33:28Neil deGrasse Tyson?

  You just went outside of his list.

• 33:31Charles Liu?

  Yeah.

• 33:32Neil deGrasse Tyson?

  To find something that could interact with a quantum wave field. Okay. But if you subtract away our four known forces.

• 33:41Charles Liu?

  Mm hmm.

• 33:41Neil deGrasse Tyson?

  Okay, the strong, the weak, the electromagnetic and gravity. Does the wave function go unperturbed at all? Is there, can dark matter, dark energy, collapse the wave function? Or is it immune from that? Do we know?

• 33:58Charles Liu?

  I don't think we know yet. Dark matter, as you know, Neil, is one of the most unusual ideas that has been experimentally confirmed, but has no theoretical explanation.

• 34:12Neil deGrasse Tyson?

  That's why I'm asking.

• 34:13Charles Liu?

  Yeah.

• 34:14Neil deGrasse Tyson?

  Is there something that the wave function can elude? I guess that's really what I think that question was after.

• 34:20Charles Liu?

  Yeah. At the moment, we don't know. It may be a dark matter particle, but remember, dark matter interacts with a gravitational field.

• 34:28Neil deGrasse Tyson?

  Yes.

• 34:28Charles Liu?

  That's why we know of its existence.

• 34:30Chuck Nice?

  Right. So, okay. But say that again, because I'm really trying to grasp that.

• 34:35Charles Liu?

  Right. Dark matter has been, has been observed.

• 34:38Chuck Nice?

  Like, so we've

• 34:39Charles Liu?

  We know it exists.

• 34:40Chuck Nice?

  Well, okay, right.

• 34:41Charles Liu?

  All right.

• 34:41Chuck Nice?

  We know it. Because we've, we've seen the effects, is what you're saying. We've seen the effects.

• 34:46Charles Liu?

  That's right.

• 34:46Neil deGrasse Tyson?

  Chuck, you are more correct in that moment than Charles implied. Okay. So it's not that we have measured dark matter. We have measured a source of gravity whose origin we do not know.

• 35:00Chuck Nice?

  Okay.

• 35:01Neil deGrasse Tyson?

  And we call that source of gravity dark matter. But to say we've measured dark matter implies that there's a thing called matter that we have measured. We've measured no such thing.

• 35:11Chuck Nice?

  Right.

• 35:12Neil deGrasse Tyson?

  We've only measured the gravity, and whatever dark matter is, it has gravity. And that's why we can say it interacts with us gravitationally.

• 35:20Chuck Nice?

  Wow.

• 35:21Neil deGrasse Tyson?

  But it doesn't interact with us electromagnetic.

• 35:22Chuck Nice?

  Electromagnetic.

• 35:23Neil deGrasse Tyson?

  It might just pass us straight through.

• 35:24Chuck Nice?

  Right, right.

• 35:25Neil deGrasse Tyson?

  We have molecules in our body that are held together by the electromagnetic force. There's no such counterpart in whatever's going on with dark matter.

• 35:34Charles Liu?

  And what we've done is tried over and over and again to posit the existence of particles that could behave the way that we've observed them, but no experiment has yet been able to detect any such particle.

• 35:47Gary O'Reilly?

  Things we don't know.

• 35:49Chuck Nice?

  That's.

• 35:49Gary O'Reilly?

  Put it on the list.

• 35:51Chuck Nice?

  That's.

• 35:53Chuck Nice?

  God, what an exciting frontier, though, when you think about it.

• 35:57Charles Liu?

  That's neat.

• 35:57Chuck Nice?

  That's really, really cool.

• 36:18Gary O'Reilly?

  All right, let's throw another question in there. Let's come away a little bit from quantum for a moment. David Flingbeal. Hello, Dr. Lou, Dr. Tyson, Lord Nice. Dave's in Palmer Heights, Ohio, and all I can think about now is Palmerham. Um, sorry, thinking with my belly again. Orange looks like a mixture of red and yellow because its wavelengths lie between them on the spectrum. Green looks like a mix of yellow and blue because it lies between them. Why does violet? Look like a mix of red and blue when it does not lie between.

• 36:50Charles Liu?

  Oh, that's a great question.

• 36:52Chuck Nice?

  Look at that.

• 36:53Charles Liu?

  It has to do with quantum biology.

• 36:55Chuck Nice?

  Ah.

• 36:56Charles Liu?

  Our eyes, we have those rods and cones in our eyes, right?

• 37:00Neil deGrasse Tyson?

  Charles, I want you to finish, but I want to preface it by saying we need to separate here the physics of what's going on from the biology of what's going on.

• 37:06Charles Liu?

  Yes.

• 37:07Neil deGrasse Tyson?

  The physics of what's going on is there exists pure orange light that is not a combination of anything, right? There exists pure green that is not a combination of anything. It's a wavelength of light that can be specified unambiguously. That's why in our field, we don't really, we make pretty pictures, colorful pictures, but we don't talk about colors in the way everyone else does. We talk about the bands of light and where they are on the spectrum. Okay, so now let's bring in some physiology.

• 37:35Charles Liu?

  No, that's fair. The way that Neil is describing is 100% correct. And violet light actually has a wavelength range where it's actually unambiguously violet. But our eyes don't actually detect that very well. Our eyes process color when photons hit and activate our cone cells, right? Whether they're the red or the green or the blue sensory cone cells. And so what we perceive as purple or violet, or more accurately, magenta, right? Comes from the interaction of the red and the blue cone cells processing in our brain

• 38:15Charles Liu?

  to create a thing, which is not the same as the violet wavelength color that comes off of, say, a physical process or hot object or something like that.

• 38:25Chuck Nice?

  Okay, so when those photons are hitting our cone cells, are we actually seeing the wavelength or our eyes creating that color? Because they would be two totally different things.

• 38:38Neil deGrasse Tyson?

  That's a good question.

• 38:39Charles Liu?

  The best way to think about it is that our brains create that color based on something that is not exactly straight physical. Like, if you look through a filter that specifically channels violet light on the spectrum, you can actually see stuff coming through it. But that violet production, that once it gets into our eyes, those violet photons come in and they do things and they produce like the same kind of violet that we would process with our brains when we see a purple t-shirt, but it's not been produced by the same physical process.

• 39:13Chuck Nice?

  Wow.

• 39:14Gary O'Reilly?

  Wow.

• 39:14Chuck Nice?

  Yeah, it's cool.

• 39:15Gary O'Reilly?

  You made coloring exciting. You made coloring exciting, Chuck.

• 39:19Charles Liu?

  Color is exciting. Vision and so forth, right? Is very often most easily explained by thinking quantum mechanically. You have photons coming in and hitting us as opposed to all these weird electromagnetic waves that kind of excite this and that. But a lot of biology is right at that intersection. We thought we knew that, oh, this human smell by this or human sea by this. But there's physics right between that layer of the organ, the eye or the nose.

• 39:50Chuck Nice?

  One last quick question. So when we make sensors that actually look out into the universe, are those sensors specifically tuned to the wavelength?

• 40:01Neil deGrasse Tyson?

  Yes.

• 40:01Chuck Nice?

  Okay.

• 40:02Charles Liu?

  Excellent question. Yes, it is.

• 40:05Neil deGrasse Tyson?

  Right. We can take three sensors to different, three different wavelength bands. And after we obtain those data, we can slap on a red, green and blue filter on them and create a color picture that you would see if you were out there in space and our cones were sensitive in those three bands.

• 40:22Charles Liu?

  Right.

• 40:22Neil deGrasse Tyson?

  That's how we can make color pictures outside of the visible part of the spectrum.

• 40:25Charles Liu?

  Right. Many of these infrared images, for example, from JWST, right? They have been RGB'd up in such a way that we see them. So when we see the purple or the violet colors there, that's not the violet. That's a color that was generated and then processed in our brains to make these pretty pictures. It's pretty cool.

• 40:44Chuck Nice?

  Hmm.

• 40:45Gary O'Reilly?

  Wow. Super cool. All right, let's kind of fall back into some things we've just discussed with another question, this time from Sarah, who is currently in Kansas. Um, what is your train driver? What is, um, what is so special about?

• 41:02Neil deGrasse Tyson?

  In this moment.

• 41:02Chuck Nice?

  Kansas is a great place. No, Kansas, home of the Runza.

• 41:05Gary O'Reilly?

  All right, what is so special about photons that they go exactly the maximum speed and any faster, they'd be moving backward in time? Is that speed, the speed of light, a barrier to them? That if it weren't, they'd be going even faster? Do photons set the maximum speed objects can travel in our universe?

• 41:26Charles Liu?

  This is a great question. And I'll first start by making a clarification that if photons exceed the speed of light, they would not be moving backwards in time. We, photons cannot exceed the speed of light because that's the definition of the speed of light, is how fast a photon goes.

• 41:42Neil deGrasse Tyson?

  I thought you said photons there for a second.

• 41:43Charles Liu?

  Photons.

• 41:44Gary O'Reilly?

  Photons can, yeah. Yes. Flying sofa.

• 41:48Neil deGrasse Tyson?

  I swear I heard flying sofa.

• 41:50Gary O'Reilly?

  That's a photon. It's kind of a flying sofa bed.

• 41:55Charles Liu?

  But, yes, the speed of light is a barrier of sorts, although it's a barrier that has come about for reasons we don't understand. The speed of light is the speed that light travels through vacuum. But that is a limit. The moment you have mass, you can't reach that speed.

• 42:18Charles Liu?

  If you have mass and you reach that speed, you have become energy. You have lost your mass. You have become a photon.

• 42:24Gary O'Reilly?

  Right.

• 42:24Charles Liu?

  So that's kind of the dynamic of how mass and energy intersect when you're approaching speeds up to the speed of light.

• 42:34Neil deGrasse Tyson?

  Yeah, but Charles, but let me, let me open up that question a little more broadly.

• 42:39Charles Liu?

  Sure.

• 42:39Neil deGrasse Tyson?

  You're being a little tautological. Is that the right term? When you say

• 42:43Charles Liu?

  Yeah.

• 42:44Neil deGrasse Tyson?

  the speed of light is the speed photons go. And if they, if they went faster, then that would be the speed of light.

• 42:49Charles Liu?

  Yeah.

• 42:50Neil deGrasse Tyson?

  And I'm saying, there is this number that we all measure.

• 42:55Neil deGrasse Tyson?

  Why can't you just nudge the photon to go a little faster?

• 42:58Charles Liu?

  We don't know. We don't know yet.

• 43:00Neil deGrasse Tyson?

  Again, like that.

• 43:01Charles Liu?

  We don't know yet.

• 43:02Neil deGrasse Tyson?

  And what then of the entire physics math description of particles that exist faster than light that we call tachyons? Because they go backwards in time.

• 43:13Charles Liu?

  Yeah.

• 43:14Neil deGrasse Tyson?

  So why can't a photon? Just step across the boundary, become a tachyon, and then go backwards in time. Why are you preventing that?

• 43:22Charles Liu?

  The existence of tachyons is, has never been shown. Theoretically, they are possible. There was one professor visiting once I was listening to, and I asked a question about tachyons, and he cut me off right after the word "tachyons." He said, "There was a fevered imagination, dream state invention of people in the 60s who were high on something. They don't exist."

• 43:48Neil deGrasse Tyson?

  That's about when it came in.

• 43:49Charles Liu?

  Yeah, yeah. So I do not comment on this tachyon concept because I have not seen any papers or read anything that suggests that they actually exist. And that is the mystery. That's the what we don't know part, right? We know how to slow down light. We can bring light down, and in fact, we have even stopped light. Lena Howe at Harvard has stopped light.

• 44:12Neil deGrasse Tyson?

  Frozen light.

• 44:13Charles Liu?

  Frozen it for a brief moment in the lab, right? It's really quite amazing.

• 44:18Neil deGrasse Tyson?

  Yeah, just the idea that, and when you think about it, I mean, why not? Because every time you go, light goes through a medium, a transparent medium, it goes slower and slower and slower. Couldn't there be a medium where it speeds it up?

• 44:30Charles Liu?

  The most empty medium we have in the universe is vacuum. And so that is the maximum speed, right? You can think about, think about it the other way. Say, say we have light going through air and we want to speed it up. We pump the air out, and now that speed has been increased. But that's as far as we can get, right? Absolute vacuum is as empty as we can get, just as absolute zero is the coldest that we can get.

• 44:55Neil deGrasse Tyson?

  But suppose you don't even have space. Maybe it goes infinitely fast.

• 45:01Charles Liu?

  Through what?

• 45:02Neil deGrasse Tyson?

  Maybe space is creating a limit for light.

• 45:04Charles Liu?

  Yeah, but what is the light traveling through? If there's no space.

• 45:11Charles Liu?

  If not light is traveling through not space, then it does not speed, right? And so it could be anything you want. That's a great question, though. No, these are fun questions to think about. I mean, there's really need to think about.

• 45:23Neil deGrasse Tyson?

  You can pass some shade on tachyons. I want to just resurrect them briefly before we get to our last question.

• 45:28Charles Liu?

  Sure.

• 45:28Neil deGrasse Tyson?

  The, the point there is, all of Einstein's equations show you cannot accept, just like you said, Charles, you cannot accelerate matter to the speed of light at all. Because everything blows up. The equations all blow up. However, if you grant something's existence at faster than the speed of light, not crossing the boundary, then you can derive a whole set of properties on the other side of that equation.

• 45:55Charles Liu?

  Yes.

• 45:56Neil deGrasse Tyson?

  Where time goes backwards.

• 45:57Charles Liu?

  Right.

• 45:58Neil deGrasse Tyson?

  And so that's, they didn't just pull it out of their ass.

• 46:01Charles Liu?

  No, that's really cool, though, because that means there could be an entire universe that is running backwards, that we can't, that we can't even see.

• 46:10Neil deGrasse Tyson?

  And the slowest they can move is the speed of light.

• 46:12Charles Liu?

  Is the speed of light.

• 46:13Neil deGrasse Tyson?

  It would take an infinite amount of energy to slow it down to the speed of light. It's, it's, it's like opposite land, you know?

• 46:19Charles Liu?

  That's the nature of what tachyons are, which are really great. And mathematically, it is consistent to an extent. Many things are mathematically consistent to an extent, which do not reflect reality. Right? Many of them, which were invented a long time ago, turned out to reflect reality, at least partially, in such a way. But in this instance, nothing has yet suggested that the tachyon structure, or the existence of such things, has any kind of intersection with our universe, where everything travels at the speed of light or slower.

• 46:56Charles Liu?

  Great, great point, though.

• 46:57Neil deGrasse Tyson?

  I was thinking one more in.

• 46:58Gary O'Reilly?

  One more, yeah. So this is from Leon Rivera. Leon hails from Jupiter, Florida, in Florida.

• 47:05Charles Liu?

  Oh. Which is its own planet in a way, too.

• 47:10Gary O'Reilly?

  So disappointing, so disappointing. So in the timing.

• 47:14Charles Liu?

  No, no.

• 47:14Gary O'Reilly?

  Um, he's a big fan of the show. I'll cut his whole question down. He says, "I would love to know what the both doctors think is the greatest achievement in astrophysics of all time." And then he puts in brackets, "so far."

• 47:28Charles Liu?

  Dang.

• 47:31Chuck Nice?

  You go first.

• 47:32Charles Liu?

  Okay. If we're talking about in my lifetime, the greatest achievement that has enabled other achievements on a way that nothing else has been able to, it is the successful design, construction, launch, and operation of the Hubble Space Telescope.

• 47:47Chuck Nice?

  Okay.

• 47:48Charles Liu?

  It is the thing that has enabled more discovery in astrophysics than anything else in my lifetime. If we need to talk about just the ultimate discovery, the thing that sort of is the most fundamental thing in astrophysics, period, I think it is the confirmation of the existence of the Big Bang. A thing where the universe was once small and is now large, that there was a moment where you could extrapolate to a time equals zero, from which everything we see and know has evolved to this point. How, the specifics of the Big Bang, we still don't know. There's still a lot of things that are like in there.

• 48:29Charles Liu?

  It could be a cyclical Big Bang, could be an inflationary Big Bang, but there was a Big Bang.

• 48:36Chuck Nice?

  And the reason there was is because we can see it, right?

• 48:39Charles Liu?

  Yep. The cosmic microwave background detection, the expansion rate of the universe accelerating, the nucleosynthetic relationships of how much hydrogen, helium, and other elements there in the universe, all of that conclusively, beyond a reasonable doubt.

• 48:56Chuck Nice?

  And the reason why I said that is because there's a lot of people who say that that is the religious leap of faith that you guys as astrophysicists make, which is juxtaposed against the leap of faith that people make when they say, well, there was a creation or a creator.

• 49:18Charles Liu?

  Right.

• 49:18Neil deGrasse Tyson?

  The difference is, the Big Bang is supported by data.

• 49:21Charles Liu?

  That's right. We did not take a leap of faith. Right. We did not take a leap of faith that was not evidence-based. That's the fundamental line.

• 49:30Chuck Nice?

  Well, that's what I'm saying. You can see it. You can see it.

• 49:32Charles Liu?

  In fact, in the middle of the 20th century, a pope actually said, you know what? The Big Bang has been shown scientifically to be true, therefore God exists. Now that is a leap of faith. Right? Right. Mm-hmm. Right. The leap of faith that that religious leader made is not the same kind of conclusions to which Neil and I and our colleagues have come to is because we are evidence-based.

• 50:03Chuck Nice?

  And that's why y'all going to hell. That's why you're going to hell.

• 50:07Charles Liu?

  If, if hell exists.

• 50:11Chuck Nice?

  How dare you, Sal.

• 50:15Neil deGrasse Tyson?

  I, I, I don't know that I could add to that. I, but those are, those are really good, important discoveries.

• 50:22Charles Liu?

  They're just off the top of my head, Neil. You know that we can think of a hundred different awesome things. I mean, this is just off the top of your head.

• 50:28Neil deGrasse Tyson?

  The Hubble telescope is objectively the most productive scientific instrument ever built.

• 50:34Charles Liu?

  Yes.

• 50:34Neil deGrasse Tyson?

  If you measure how many research papers, how many different collaborators, how many different nations participated in research results that derived from that telescope.

• 50:44Charles Liu?

  So. Yes.

• 50:44Neil deGrasse Tyson?

  So that's not just your opinion there. You've got a, there's, there's metrics to back it up. Um, I would mention two things. Number one, for the 20th century, I would say the discovery that the heavy elements in the universe owe their origin to heavy stars, massive stars, that have manufactured them in the crucibles of their nuclei.

• 51:11Charles Liu?

  Yeah. Burbidge, Burbidge, Fowler and Hoyle. Yeah.

• 51:14Neil deGrasse Tyson?

  And.

• 51:14Charles Liu?

  Marvelous work.

• 51:15Neil deGrasse Tyson?

  Scattered that enrichment across the galaxy, allowing complex molecules, and in the limit of complex molecules, you get what we call life. That that discovery was in 1957, just right mid-century by the, the Burbidge couple, Jeff Burbidge and Margaret Burgess.

• 51:36Charles Liu?

  And Fowler and Hoyle.

• 51:37Neil deGrasse Tyson?

  Fowler and Hoyle. Fowler would ultimately get a Nobel Prize.

• 51:42Chuck Nice?

  Damn.

• 51:42Neil deGrasse Tyson?

  That, that discovery borders on the spiritual, enabling us to recognize that we are not simply alive in this universe. The universe is alive within us.

• 51:57Neil deGrasse Tyson?

  We contain the ingredients of the stars. That is a kinship that some people use it to feel small, but I use it to feel large. When I look up at the night sky, I feel a sense of participation in the great. Y'all not so special. Y'all not so special. All that, all that stuff is inside me too. Okay. We are as amazing and as ordinary as every star in the sky. Wow, that's so cool. That's great. Except there are more stars than there are people. Yeah. So. Right now.

• 52:38Neil deGrasse Tyson?

  Right now. We've only gotten started, right? And lastly, if I go through all of time, I would say it is not just the supposition, but the evidence that the universe is knowable. Oh, super philosophical. Awesome. No, because if everything in the rest of the universe were completely different from what happened in your laboratory, the universe would not be knowable. If different laws of physics applied on every planet and every galaxy and every, we, we just have our own little world here.

• 53:18Neil deGrasse Tyson?

  But the fact that we measure things, objective things on earth and find them playing out elsewhere in the universe is an extraordinary fact. Yeah. And I, and it wasn't that long, it's 300 years ago where it was, we found that the orbit of Uranus did not follow Newton's laws. And people suspected, well, because Uranus was a newly discovered planet in the era of Newton's laws of gravity. And people said, I wonder if we found the edge of the applicability of Newton's law of gravitation. You go out that to Uranus, it doesn't apply anymore. And someone said, well, maybe it does. And there's another planet out there who, gravity we have not reckoned.

• 54:02Neil deGrasse Tyson?

  And they searched and they found Neptune. They found Neptune. Oh my gosh. And after that, we would find binary stars orbiting, following Newton's laws of gravity. Binary galaxies, all of this. And so the fact that the universe is noble. Oh my gosh. That's gotta be the most profound fact of science of any scientific discovery there is. You sound like you should marry the universe.

• 54:34Neil deGrasse Tyson?

  What, you're middle school?

• 54:40Neil deGrasse Tyson?

  So I hope that those two points of view. And I agree, Charles, we could have gone on for another hour. Oh, yeah. Listing these achievements. So Gary, thanks for putting this together.

• 54:51Gary O'Reilly?

  You're welcome. Thanks to our Patreon members. Their curiosity is fascinating.

• 54:57Neil deGrasse Tyson?

  And Charles, good luck on the release of your book. Thank you so much. Yeah. Give me the name and title again. It's called The Handy Quantum Physics Answer Book. Excellent, excellent. And it's at better bookstores near you.

• 55:12Neil deGrasse Tyson?

  All right, Chuck, always good to have you, man. Always a pleasure. Neil deGrasse Tyson here. Keep looking up.