The Complex Universe_ with Sean Carroll

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Something that's fascinated me for decades, ever since I could
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think about this question, and that's the arrow of time.
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I can have photographs of the past. I cannot have
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photographs that are truly representing what happens in the future.
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The early universe, 14 billion years ago, near the Big Bang,
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was in a very special, organized state. And it's becoming
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more disorganized and higher entropy, as we say, ever since then.
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That's where the arrow of time comes from.
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This is StarTalk Cosmic Queries Edition. Neil deGrasse Tyson, you're
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a personal astrophysicist. We got here, of course, Lord Chuck Nice.
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How you doing?
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What's happening, man? You all locked and loaded there? I'm
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locked and loaded because we got queries, man. And they're
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not just queries about anything to anyone.
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No.
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They're queries on cosmology to one of our cosmologists about town.
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Yes. One of our fave interviews. We've got Sean Carroll
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on the line. Sean.
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Sean.
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How you doing, man?
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Hey, how's it going? Lord Chuck, I didn't know you
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got a promotion.
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If you try hard like he does, you might get
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one too.
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Yeah, I mean, no kings, but lords are okay. The
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occasional lord.
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There you go. That's right.
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No, I'm down with the no kings, but I'm still
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Lord Nice.
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So let's catch people up on your trajectory through life.
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You spent a lot of your professional career at Caltech
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over in Pasadena, and now you joined us back on
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the East Coast in Baltimore. at the Johns Hopkins University.
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And I've got you as the homeward professor of natural philosophy.
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That's right. There aren't that many of those. I'm basically
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the only one. So it's nice.
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Right. This is a very retro title. It is. Okay.
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I think Newton had a title of natural philosophy. Right.
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Before the word physics was a thing. Yeah. Yeah.
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And you're one of my favorite people out there because
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not only do you bring science to the public, which
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is something we care deeply about here at StarTalk, but
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you have the For me, the best combination of astrophysics fluency,
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physics fluency, and philosophy fluency. You put all that together,
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and there's no boring conversation you will ever have, ever.
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True. But we're going to try to change that today.
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I'm going to take this as a challenge.
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Yeah, I bet I can do it.
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So, Sean, you had a couple of books recently. I mean,
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you're always out there, you know, talking- physics smack with
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an interested public. You have two in a row here, space, time,
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and motion. You know, that's what's left after that, right?
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That's a lot, yeah.
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That's pretty much everything, right? But no, not for Sean Carroll.
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He's got quanta and fields. Oh, wow.
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Look at that. Now it is everything. Space, time, and motion,
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and then quanta and fields. What's left?
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What's left will be volume three, which is complexity and emergence.
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That's what I'm nearly done with writing right now. So
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it's a whole three-part series called The Biggest Ideas in
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the Universe.
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Yeah. That's definitely what that is. That is. For sure.
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For sure.
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You know, fields is a thing that if I didn't
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study physics, I'd still think they were kind of imaginary.
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Go back to Faraday, right, who says there's magnetism there,
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but there's a field.
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Well, can I see it? No. No. But like the
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iron filings can see it, but I can't. Right. Okay.
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But if you take away the iron filings, is it
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still there? Yeah.
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And so just to– what did it take to get
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everybody comfortable with the idea of a field?
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That's a great question because it wasn't easy. It took
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a while. Isaac Newton worried about the fact that he
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didn't know about the concept of fields. He said that
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there was a gravitational force between the sun and the
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earth– And it depends on the distance, you know, the
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inverse square law, the bigger the distance, the less the force.
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But he didn't know how it got there. How does
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the Earth know where the sun is, how far away
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it is, how massive it is? And he said, you know,
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this is over my pay grade. I'm going to leave
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this for future generations to decide, which is not the
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kind of thing that Isaac Newton said very often. So
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it wasn't until the 1800s.
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So he knew something was up.
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He knew something was up.
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That needed further explanation. Wow.
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Action at a distance. Einstein famously said spooky action at
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a distance for quantum mechanics. But even in Newton's time,
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there was this weird thing. What is it that takes
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the gravitational force and moves it from the sun to
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the earth, et cetera?
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And vice versa. Yeah.
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And in some way, there was an answer there from Laplace.
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Pierre-Simon Laplace, but it wasn't until Faraday, like you said,
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that he starts moving magnets and watching electrical currents pop
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up in a wire next to it. Like not there,
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not touching it, right? Through empty space, something happened. And
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the great thing about Faraday was he was an absolutely
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genius engineer. intuitive physicist. He was not the math expert
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that you sometimes need to be. So Maxwell, James Clark
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Maxwell came along, was a huge admirer of Faraday and
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basically made it all mathematically respectable and said, yeah, there's
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these things called the electric field and the magnetic field
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and they fill all of space and you can't see them,
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but we can predict what they're going to do and
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they're super duper important for explaining everything.
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I think Faraday, if memory serves... In none of his
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published papers does an equation of any kind appear.
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That's possible. I didn't know quite that factoid, but it's
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absolutely in keeping. He was thinking about– in fact, it
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wasn't even fields that he primarily focused on. He imagined
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lines of force. So like out of an electron, there's
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an electric field we would say now, but he thought
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they were like literally lines of force filling all of space.
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Maxwell's first papers were about trying to make mathematical sense
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of lines of force. And he eventually said, no, it's
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better to think of fields with little vectors, so like
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little arrows at every point. And then the lines are
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sort of moving in the direction of the arrows.
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And that all happened in the 19th century.
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All happened in the 19th century. And the great thing was,
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you know, if you think of the number of different
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apparent phenomena in the world. that we now think of
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as electricity and magnetism in action, right? Heat, light, radio waves, x-rays,
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you know, the magnets, all this stuff, like very, very
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different things, all explained in just two fields talking to
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each other, electricity and magnetism.
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That's amazing. That's completely crazy.
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And I was just thinking, I go through this sort
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of existential moment maybe once a month. I'm sitting there
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and I press a button on my smartphone and it
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changes the channel on my TV. And then I press
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another button, it starts my car, which is three miles away.
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And I'm thinking, this is magic.
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Yeah, basically.
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Yeah, and this is why writing books is good because
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you write a book and you say like, You point
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your remote control at your TV and a radio wave
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comes out and turns it on. And you get many
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emails saying that's an infrared wave, not a radio wave.
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You don't know what you're talking about. But they're all
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different manifestations of electromagnetism.
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No, no. Wait, wait. But my cell phone is not infrared.
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Your cell phone is not, but your TV remote control is.
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Yeah, that's for sure. Yeah, exactly.
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Who knows these things? I can't keep track of these things.
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I'm just a theoretical physicist.
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It's funny, while you guys are talking, I'm sitting here
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with my iPad and I'm taking my finger and moving
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the screen.
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Up and down. Into this void above your... Right.
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And it's exactly the same thing. Isn't that the electromagnetic
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field on my finger?
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Basically, everything is the electromagnetic field. Other than gravity, it's
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all electromagnetism all the way down.
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We live it. We just live it.
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There's a hugely important philosophy of science lesson here, because
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like Neil said... You can't see the electric field or
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the magnetic field, but they're clearly everywhere. Like we have
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equations that describe them exactly and make predictions and fit
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all the data. Therefore, we accept that they are there.
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You don't need to see them with your eyes to
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have evidence that they're part of reality.
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I'd do a whole– stand-up bit about that.
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And I try to beat that into Chuck every time
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when I say the universe is under no obligation to
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make sense to you.
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Which, believe it or not, I can't accept!
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You must make sense to me because I am the
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center of all things!
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And so, Sean, what's this latest paper we have you
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publish here, co-authored, what Hawking radiation looks like as you
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fall into a black hole? Was that something that needed
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to be addressed?
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It's something that I've worried about for decades. And honestly.
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Really?
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Yeah. Well, so here's the question. There's two things that
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we think are true about a black hole. One is
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if you're standing very far away and you look at
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the black hole, Stephen Hawking says black holes give off radiations. Okay,
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not that much radiation, admittedly, especially for a big black hole.
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But he, again, has an equation that predicts exactly how
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much you should see. The second thing is we have
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this feeling, no one's ever done it, but we have
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this belief that if you fall into a black hole,
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you see nothing special when you cross the boundary, when
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you cross the event horizon, right? It just looks like
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ordinary empty space everywhere. But these two statements seem a
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little bit contradictory because if I'm standing far away and
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I see radiation coming out, and then I just fall in,
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I stop my rocket ship or whatever, I let myself
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fall in, you know, Neil, that you should see that redshift,
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that radiation blue shifted. It should look brighter and brighter
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and more and more energetic. So why does it turn
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off when you hit the event horizon? What actually happens?
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What is it that you see? And it turns out
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this is 100% implicit and in all the equations that
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we have, but it took a lot of work to
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actually pull it out. And the answer in a very short,
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slightly oversimplified form is there is high intensity radiation when
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you're crossing the event horizon, but you're moving so fast
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that you don't have time to observe it. So it
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looks to you like there's nothing there.
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Wow.
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Yes.
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Wow. I mean, in a Heisenberg uncertainty principle way, you
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don't have time to observe it.
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Yeah, exactly right. And by the way, before I forget,
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I got to give huge credit to Chris Shalhoub, my
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co-author on this.
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Your co-author, yes.
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He was a grad student at Harvard who just graduated,
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did all the heavy lifting on this and other projects,
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and he was fantastic. So he got the right answer
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after other people's got it wrong.
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Graduate students, they have to have an exception to the
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slave amendment in the Constitution for graduate students.
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Right.
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Just so you know. Why are they not? Are they
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only three fifths of a person?
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No.
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Three fifths of a scientist. Yeah.
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Three fifths of a scientist. Is that what they are?
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His graduate student did the heavy lifting. Right. There it is.
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But see, that's the whole. Sean is in the Bahamas
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and his graduate student. And that's the way it should be.
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Sean already did his work. Okay. That's the whole idea.
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I would have loved to do the heavy lifting, but
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for his sake, I needed to let him have that experience.
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You know how it is. Of course. Yes.
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I mean, listen, Leonardo da Vinci, when he painted, he
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had artisans that worked under him and they do a
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bunch of the work and then you come in and
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you sign your name.
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No, but I will tell you this, that in physics
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and astronomy, in our journals, It is not our tradition
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to put our degrees after our name, the way it
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is in the social sciences.
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And why is that?
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Well, I made up a reason why that's good, but
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I don't know if it had different origins. And Sean,
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you might have some insight here. If you didn't otherwise
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know the people, you have no idea who is senior,
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who is junior, because a brilliant idea can come out
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of anybody, even your students. And so there's no reason
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to segregate who's got title and who doesn't, because a
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brilliant idea is a brilliant idea no matter.
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The package, and a stupid idea is a stupid idea. True,
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no matter who comes up with it. Yeah, I like that.
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I like that system. It's very egalitarian.
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Yeah.
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I like that. Nope, that's lame. Mm-hmm. Ready? Do you
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harbor questions about the universe?
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Some long-held bit of cosmic curiosity lingering within you? or
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questions about anything at all, you can become a Patreon
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supporter of StarTalk. You have access to our exclusive question
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line on our website. Those are where we draw our
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questions for our Cosmics.
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Some of the most extreme objects in the universe.
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StarTalk is a work in progress where we, every month,
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come up with some new way, some new idea, some
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new understanding of how to bring the universe down to Earth.
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We could not do that without your support.
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Thank you.
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And as always, keep looking up. Sure, one other thing
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before we get to our Patreon questions. Something that's fascinated
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me for decades, ever since I could think about this question,
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and that's the arrow of time. Some of my earliest
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books in middle school were all about time and how
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it passes and why do we know time is going
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forward rather than backwards. And You have some emergent thinking
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on that? I absolutely do. You know, this is something
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that was hugely important for me in my career. The
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arrow of time is just the fact that the past
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and future are different from each other, right? Like I
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can have photographs of the past. I cannot have photographs
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that are truly representing what happens in the future.
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AI has got your future. Lord Chuck can do it,
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but I can't do it. So, you know, why is
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this true? And Aristotle wouldn't even have had the question. Like,
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they're just different things. Like, why is an elephant not
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an orange? Like, what are you even asking? But once
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Isaac Newton comes along with his theory of physics, suddenly
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the distinction between the past and future disappears. Like, these
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equations don't treat the past and future differently. So, it
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turns out, long story short, that it's a cosmology question.
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The early universe, 14 billion years ago, near the Big Bang...
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was in a very special organized state. It's becoming more
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disorganized and higher entropy, as we say, ever since then.
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That's where the arrow of time comes from. Okay, why
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was the early universe like that? We don't know. So
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I wrote a paper about this 20 years ago, and
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I'm revisiting that now to try to improve upon it.
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We still don't know, but I do think we're making
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progress in that direction.
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Well, I hope so after 20 years.
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That's not very long in the history of the universe.
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You know what I was going to say?
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Excuse me. Don't put universe on me. It's a fourth
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of your life, a fifth of your life.
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The universe will wait.
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We know which direction time moves because certain phenomena– we
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would never see in reverse. Like some famous ones are,
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you drop a blob of ink in water, the ink
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will disperse. You never see that happen in reverse. So
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if you're just eavesdropping on a scene, and no one
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told you which way time was pointing, just by phenomena
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that occur.
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You should be able to figure it out. Like you
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never see an orange fall up from the ground back
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onto a branch.
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Right.
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But these are, you know, you're picking good examples, but
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let's admit you're picking the easy examples. We understand those examples,
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but I can make a choice about what to do
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right now. Like I could make a choice right now.
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This is the most boring podcast ever. I'm going to
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storm off and not do it.
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You won't be the first.
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But I can't make a choice now. not to have
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come on the podcast in the first place. I can't
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make a choice that affects the past.
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Oh, look at that.
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And so that's right there at the boundary of physics
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and philosophy. Both the physicists and the philosophers need to
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think about this. And again, we have good ideas, but
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there's still work to be done.
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Wow.
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And now, now you got me thinking about the multiple
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timelines and parallel universes and every single, like if we
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are on a, call it a trajectory, every choice that
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we make, all those other possible trajectories from this point
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of decision.
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Still continue forward just without me.
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So what the hell is happening there?
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I'm not sure if I'm quite on board with your
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explanation there of what's going on.
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No, what I'm saying is I'm being way too literal, Sean.
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What I'm saying is the possibilities of all those trajectories.
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What are the many worlds hypothesis? Is that what that is?
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Is that what I'm talking about?
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Okay. Well, it's pretty close. I mean, many worlds is
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like really down to earth and equation based. There's The
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Schrodinger equation of quantum mechanics tells you what set of
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things happen in the future and which don't. And it's
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not because you're making a decision that creates a difference
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between one world and another. It's because of entanglement in
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the underlying quantum structure of reality. But we do have
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reason to believe that there are other copies of the
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universe where things turned out a little bit different. And
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you can all, if you have an iPhone, you can
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00:17:50.130 --> 00:17:54.180
download an app. called Universe Splitter. And I'm a big
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salesman for this app here. And I don't get any
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commission or anything, but I think everyone should get it
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because when you're torn between two decisions, should I take
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this job or should I just continue living a life
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of leisure? You can ask the phone and you can
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plug in these two options and it will send a
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00:18:12.990 --> 00:18:16.009
photon down a beam splitter that has a 50-50 chance
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of saying, you should take the job or you should
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just stay sitting around. And then there'll be, if you
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do it, if you obey the instructions, you know there
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will be a world in which you did the other thing.
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That brings me to my question. You got a question
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before we start. Before we even start. And specifically. Did
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you pay your $ 5 a month? I'm going to owe you.
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In another world, he did.
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In another world, I paid it. That's funny. All right, Sean,
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this is specifically for you. Okay. This question. That is
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your question.
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It's my question. First of all, you have to be
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familiar with this experiment. In the double slit delayed choice
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quantum eraser experiment.
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Okay.
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I know you've been worried about that one.
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00:19:04.190 --> 00:19:04.390
Yeah.
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No, I really am. Sean, I'm dead serious. I told Neil,
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this is keeping me up at night. Sean, that's a thing.
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00:19:10.380 --> 00:19:12.119
It's a thing. Yeah, it's a thing. Right.
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00:19:12.319 --> 00:19:15.700
It's the double-slip delayed choice quantum eraser experiment. Okay, I'd
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never heard of this. Okay, go. Okay. And maybe it's all,
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I don't know, maybe it's, I read about it and
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I'm just like, this is crazy. Maybe it's BS. I
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00:19:22.690 --> 00:19:23.730
don't know. Give it to me. All right.
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00:19:24.289 --> 00:19:27.029
So it appears that the photons know they're being measured.
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Like they actually know.
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All right.
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00:19:29.849 --> 00:19:33.079
So the signal photons and the Eidler photons- show a
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00:19:33.259 --> 00:19:37.440
constructive wave interference pattern when they're not measured by a detector.
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00:19:37.980 --> 00:19:44.049
But there's four detectors and they can't know because of
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the way the detectors are set up because the photons
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are split and some go on not to be be
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measured and some go on to be measured.
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Okay.
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00:19:55.240 --> 00:19:59.319
Now, here's the deal. There is no wave interference pattern
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when they are measured. This makes it look like they
400
00:20:03.869 --> 00:20:07.390
know when they're being observed. I can understand the whole
401
00:20:07.450 --> 00:20:08.869
explanation of entanglement.
402
00:20:09.039 --> 00:20:09.490
I don't know why.
403
00:20:09.539 --> 00:20:11.440
I should say I can accept it. I don't know
404
00:20:11.480 --> 00:20:13.440
why it's easy for me to accept that, but I
405
00:20:13.460 --> 00:20:18.519
can just accept it. What I can't know or understand
406
00:20:18.940 --> 00:20:24.990
is a particle knowing that it's being watched. So are
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00:20:25.029 --> 00:20:32.210
there any hypotheses that would explain why this thing would know?
408
00:20:33.000 --> 00:20:36.680
So that's just that your query there sounds like you
409
00:20:36.720 --> 00:20:40.480
just need the double-slit experiment. I'm still distracted by the
410
00:20:40.559 --> 00:20:42.759
rest of what it's called. No, this is beyond the
411
00:20:43.500 --> 00:20:46.839
double-slit experiment. Because, well, maybe I'll let Sean explain it.
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Because I could explain it, but I'm probably not going
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to explain it as eloquently as Sean, the way the
414
00:20:52.490 --> 00:20:53.500
experiment is set up.
415
00:20:54.029 --> 00:20:56.750
Yeah, the double-slit experiment is, of course, a famous thought
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00:20:56.789 --> 00:20:59.670
experiment originally. They wrote down what it should do long
417
00:20:59.690 --> 00:21:02.569
before they ever did it. to illustrate the magic of
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quantum mechanics. You have a single electron going through two slits.
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It's detected somewhere on the other side. And it's just
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a dot. You can't figure out that much from the dot.
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But you do that many, many, many times. And what
422
00:21:15.150 --> 00:21:19.329
you see is an interference pattern. It's like a wave
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went through the two slits. And waves go up and
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down depending on how far away they are from the target.
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And so, A wave going through one slit can interfere
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with the wave going through the other slit. That's what
427
00:21:30.019 --> 00:21:34.339
you see in the distribution of dots on the detector screen.
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The miracle occurs when you observe which slit the electron
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goes through. Because in the Copenhagen usual way of thinking
430
00:21:43.690 --> 00:21:48.950
about quantum mechanics, when you observe the electron, you collapse
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00:21:49.309 --> 00:21:52.089
its wave function. It's no longer going through both slits.
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00:21:52.109 --> 00:21:55.529
You saw it go through one or the other. And magically,
433
00:21:55.930 --> 00:21:59.970
the interference pattern goes away because indeed you changed the
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00:22:00.049 --> 00:22:03.450
electron dramatically by observing which one it goes through. So
435
00:22:03.490 --> 00:22:07.069
that's all standard stuff. Everyone, you know, and their mom
436
00:22:07.109 --> 00:22:09.349
learns that in kindergarten when they're learning about quantum mechanics.
437
00:22:10.069 --> 00:22:16.059
The delayed choice quantum eraser experiment is a hilariously convoluted
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00:22:16.470 --> 00:22:20.099
elaboration of that, which makes people feel bad for no
439
00:22:20.160 --> 00:22:21.119
good reason at all.
440
00:22:21.700 --> 00:22:22.960
Oh, thank God.
441
00:22:23.059 --> 00:22:27.130
I actually wrote... a blog post about it called The
442
00:22:27.190 --> 00:22:30.430
Notorious Delayed Choice Quantum Eraser, where I make fun of
443
00:22:30.490 --> 00:22:33.529
people who are trying to make you lose sleep because
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of this.
445
00:22:34.109 --> 00:22:34.930
Well, they got to me.
446
00:22:34.970 --> 00:22:35.490
They got it.
447
00:22:35.730 --> 00:22:35.970
I know.
448
00:22:35.990 --> 00:22:39.569
We're all victims here, I think. The way that works
449
00:22:39.890 --> 00:22:43.640
is rather than just observe, whether the electron goes to
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the left slit or the right slit. What do you
451
00:22:45.400 --> 00:22:47.380
mean by observe? You mean like maybe you with your
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00:22:47.500 --> 00:22:50.660
eyeball or with some measuring apparatus have detected it. But
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00:22:50.680 --> 00:22:53.140
what if you just entangle it a little bit? Like
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you entangle it with one little particle, okay? Then, unlike
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if you personally had observed it, you could imagine unentangling it.
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00:23:02.329 --> 00:23:07.720
You could imagine not letting it get the interference pattern destroyed,
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00:23:07.900 --> 00:23:10.500
or you could imagine having it be destroyed. And you
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00:23:10.519 --> 00:23:15.660
can make that decision after the electron's been detected. That's
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00:23:15.680 --> 00:23:17.180
the slightly spooky part, right?
460
00:23:17.779 --> 00:23:18.980
That's the spooky part, right.
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00:23:19.259 --> 00:23:22.180
If you were the kind of person who spoke a
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00:23:22.240 --> 00:23:26.450
language of the electron goes through one slit or the
463
00:23:26.529 --> 00:23:30.990
other slit and it's making a decision... Then what Chuck says,
464
00:23:31.130 --> 00:23:34.569
like it sounds like the electron's decision was affected by
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what I did after it was detected. Oh my God,
466
00:23:36.769 --> 00:23:40.190
how could that be? But if you just talk the
467
00:23:40.230 --> 00:23:44.410
language of a wave going through and becoming entangled and
468
00:23:44.450 --> 00:23:48.349
taking quantum mechanics seriously, all of this is 100% what
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00:23:48.410 --> 00:23:51.650
is predicted by the Schrodinger equation of quantum mechanics without
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anything knowing anything, anything making any choices or anything going
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backward in time.
472
00:23:57.200 --> 00:23:59.069
Okay. So there. So there you have it.
473
00:24:00.299 --> 00:24:02.880
It's hard to explain, but I encourage people to Google
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00:24:02.980 --> 00:24:05.789
notorious delayed choice quantum eraser and they will find my
475
00:24:05.829 --> 00:24:08.769
blog post and they will hear it all. And this
476
00:24:08.809 --> 00:24:12.029
is literally the chapter I wrote for my book, Something
477
00:24:12.069 --> 00:24:14.470
Deeply Hidden, which is all about quantum mechanics. And I
478
00:24:14.529 --> 00:24:16.930
read the chapter and said, this is too much. Like
479
00:24:16.970 --> 00:24:20.210
they don't need this. Like this is too complicated and specific.
480
00:24:20.230 --> 00:24:21.650
So I just made it a blog post instead.
481
00:24:22.630 --> 00:24:23.950
Excellent. And where do we find that blog post?
482
00:24:24.710 --> 00:24:28.359
On my blog, preposterousuniverse.com slash blog. But again, if you
483
00:24:28.380 --> 00:24:32.279
just Google delayed choice quantum eraser with the word notorious
484
00:24:32.339 --> 00:24:34.420
in front, my blog post will come up first, I
485
00:24:34.460 --> 00:24:34.960
promise you.
486
00:24:35.440 --> 00:24:40.630
Preposterous universe. Preposterous universe. That's preposterous. Exactly.
487
00:24:42.460 --> 00:24:42.660
All right.
488
00:24:42.720 --> 00:24:44.619
All right. Well, that was good, man. All right. Thanks
489
00:24:44.640 --> 00:24:46.539
for that. You got your zero dollars worth of it. Yeah,
490
00:24:46.619 --> 00:24:47.839
I got my zero dollars worth of it.
491
00:24:47.900 --> 00:24:52.609
It's a perfect example of rather than trying to demystify
492
00:24:52.690 --> 00:24:56.529
quantum mechanics, sometimes people try to mystify it. They try
493
00:24:56.549 --> 00:24:58.890
to make it sound even more confusing than it is.
494
00:24:58.990 --> 00:25:01.380
Quantum mechanics really is confusing. You don't need to make
495
00:25:01.410 --> 00:25:03.180
it sound more confusing than it is.
496
00:25:03.460 --> 00:25:06.980
And that's what this is doing. And you're absolutely right. Well,
497
00:25:07.000 --> 00:25:10.359
that's cool, man. Well, I appreciate that. Okay, here we go.
498
00:25:10.380 --> 00:25:16.200
This is from our buddy, Kevin, the sommelier. And he says, um,
499
00:25:16.619 --> 00:25:23.660
if dark matter were a wine varietal, would we be
500
00:25:23.900 --> 00:25:26.240
at the, I know it exists, but I can't quite
501
00:25:26.259 --> 00:25:30.900
describe it stage or the, I swear I taste something,
502
00:25:30.920 --> 00:25:33.619
but everyone thinks I'm making it upstage.
503
00:25:35.549 --> 00:25:36.049
That's funny.
504
00:25:36.730 --> 00:25:39.230
Uh, on a more grounded note for the holidays, uh,
505
00:25:40.180 --> 00:25:41.500
Gaia Promis.
506
00:25:42.319 --> 00:25:47.500
Gaia. Gaia. Gaia. Oh, Gaia. Like Gaia. No, G-A-J-A. Gaia.
507
00:25:47.640 --> 00:25:48.539
It's Italian. Okay.
508
00:25:48.920 --> 00:25:52.369
Gaia Promis, which is a beautiful Super Tuscan, will pair
509
00:25:52.400 --> 00:25:56.109
incredibly well with any roast that you are planning. Oh.
510
00:25:56.210 --> 00:25:59.289
And you're familiar with this Gaia Promis, aren't you? It's expensive,
511
00:25:59.329 --> 00:26:01.710
but it's good. Oh, okay. Yeah, yeah. All right. And
512
00:26:01.730 --> 00:26:04.769
you say that like... Chuck, you can't afford it. That's
513
00:26:04.789 --> 00:26:05.450
what you just said.
514
00:26:05.470 --> 00:26:06.289
That's what I was hearing.
515
00:26:06.329 --> 00:26:09.049
That's all I heard. You were like, got it. Yeah, Chuck,
516
00:26:09.089 --> 00:26:11.339
you cannot afford it. Okay. So maybe one day I'll
517
00:26:11.359 --> 00:26:14.299
pour it for you at my house. In the meantime,
518
00:26:14.339 --> 00:26:14.880
keep dreaming.
519
00:26:14.920 --> 00:26:16.240
But the yellowtail is good, Chuck.
520
00:26:16.259 --> 00:26:16.579
Don't worry.
521
00:26:16.599 --> 00:26:18.900
You'll love it.
522
00:26:18.920 --> 00:26:20.740
Two buck Chuck. It's two buck Chuck. I'm down.
523
00:26:21.859 --> 00:26:25.119
So in that question, I guess he's trying to, using
524
00:26:25.200 --> 00:26:29.769
his wine expertise, trying to probe What's really going on?
525
00:26:29.910 --> 00:26:33.380
Was it dark energy or both? No, he said dark matter.
526
00:26:33.400 --> 00:26:34.420
Just dark matter. Yeah.
527
00:26:34.619 --> 00:26:34.799
Yeah.
528
00:26:34.819 --> 00:26:40.039
Could you just put some anchoring onto, because a lot
529
00:26:40.079 --> 00:26:41.750
of people think we're just making it up.
530
00:26:41.789 --> 00:26:43.710
Yeah, make it up. Yeah. And does it have to.
531
00:26:43.670 --> 00:26:46.420
Be a particle? Ooh, ooh, that's a tougher one. You
532
00:26:46.440 --> 00:26:48.140
made it tough. I had an easy question. You threw
533
00:26:48.180 --> 00:26:49.160
me a softball there.
534
00:26:49.279 --> 00:26:50.859
See, this is what I do, man.
535
00:26:50.920 --> 00:26:53.400
You just saw what I did with that stupid delayed
536
00:26:53.460 --> 00:26:54.480
double slit thing.
537
00:26:55.119 --> 00:26:57.500
I can't help. And Neil, we just did this earlier.
538
00:26:57.519 --> 00:26:59.720
We were together earlier before you got on and he
539
00:26:59.740 --> 00:27:02.759
was just like, Chuck, you overthink everything.
540
00:27:03.880 --> 00:27:04.920
Just calm down, bro.
541
00:27:06.779 --> 00:27:08.880
Look, you know, back in my day, when Neil and
542
00:27:08.920 --> 00:27:11.359
I were young, it was perfectly okay to think that
543
00:27:11.440 --> 00:27:14.900
maybe dark matter didn't exist. In other words- There were
544
00:27:15.000 --> 00:27:18.829
absolutely things going on in galaxies and clusters of galaxies,
545
00:27:18.869 --> 00:27:21.410
things like that, that looked like dark matter. It looked
546
00:27:21.430 --> 00:27:24.789
like there's more matter in a galaxy than we could
547
00:27:24.950 --> 00:27:28.410
attribute– account for just by counting the stars and the
548
00:27:28.450 --> 00:27:31.170
gas and the dust. But maybe there was something weird
549
00:27:31.190 --> 00:27:34.839
going on with gravity. Maybe Isaac Newton and Albert Einstein
550
00:27:34.859 --> 00:27:38.579
didn't have the last word. We've long since passed that
551
00:27:38.740 --> 00:27:41.140
phase of the development of cosmology. And I think a
552
00:27:41.200 --> 00:27:43.700
lot of people haven't caught up because we've learned so
553
00:27:43.740 --> 00:27:47.440
much more from the leftover radiation from the Big Bang,
554
00:27:47.480 --> 00:27:52.220
the cosmic microwave background, from gravitational lensing with clusters of galaxies,
555
00:27:52.549 --> 00:27:55.789
from the growth of structure of galaxies and clusters and
556
00:27:55.809 --> 00:27:59.730
things like that. Dark matter exists. It's really there in
557
00:27:59.809 --> 00:28:03.410
some form or another. Now, maybe gravity is also modified.
558
00:28:03.490 --> 00:28:06.309
That's perfectly okay. But yeah, there's something called dark matter.
559
00:28:07.130 --> 00:28:09.390
Is it a particle? Well, we got to admit, we
560
00:28:09.430 --> 00:28:13.930
don't know what it is. The range of possibilities goes from,
561
00:28:13.950 --> 00:28:17.329
you know, some tiny fraction of the mass of an
562
00:28:17.390 --> 00:28:20.960
electron to the mass of the moon or something like that, right?
563
00:28:20.980 --> 00:28:23.380
I mean, there's a very, very large range of possible
564
00:28:23.420 --> 00:28:26.380
masses that dark matter could have if it's a particle.
565
00:28:26.859 --> 00:28:30.579
Could it be something beyond a particle? It always could
566
00:28:30.640 --> 00:28:33.420
be like this, you know, anything is possible, but boy–
567
00:28:33.619 --> 00:28:36.420
it really acts like particle-like. We know a lot about
568
00:28:36.500 --> 00:28:38.779
where the dark matter is, how much of it there is,
569
00:28:38.839 --> 00:28:43.720
how fast it's moving. It looks exactly like some massive,
570
00:28:43.819 --> 00:28:47.160
slowly moving particle that was sort of still stationary in
571
00:28:47.200 --> 00:28:50.569
the early universe and started moving ever since then. So
572
00:28:50.970 --> 00:28:53.450
it's our job to go actually find it, then we'll know.
573
00:28:54.390 --> 00:28:55.289
So two small points.
574
00:28:57.849 --> 00:29:01.750
Whenever given the occasion, I don't describe it as dark
575
00:29:01.789 --> 00:29:05.190
matter because- We don't know its matter, but it is
576
00:29:05.329 --> 00:29:06.519
definitely dark gravity.
577
00:29:07.240 --> 00:29:09.329
That's what it is. Right?
578
00:29:09.549 --> 00:29:12.380
Because we're tracking gravity at every turn that we say
579
00:29:12.410 --> 00:29:15.079
we're measuring the dark matter. So I think that's the
580
00:29:15.619 --> 00:29:21.799
most honest way to describe it. Because, Sean, you've seen this. Clickbait,
581
00:29:22.339 --> 00:29:25.519
there's a news article that says, you know, scientists may
582
00:29:25.539 --> 00:29:27.079
be wrong about dark matter.
583
00:29:27.180 --> 00:29:29.369
Of course. It might not be matter. Yeah.
584
00:29:29.460 --> 00:29:32.170
But we can't be wrong about dark gravity because we
585
00:29:32.190 --> 00:29:34.710
don't know what it is. I'm just trying to distinguish that.
586
00:29:34.750 --> 00:29:36.980
No, I think that's a perfectly good and fair distinction,
587
00:29:37.019 --> 00:29:40.589
but I think that I would just be more conclusive
588
00:29:40.700 --> 00:29:42.269
about what we do know.
589
00:29:42.630 --> 00:29:44.569
Like I said- And you sounded very good there. You
590
00:29:44.589 --> 00:29:45.289
sounded really good.
591
00:29:45.450 --> 00:29:49.259
In the 80s, what we were discovering was there's more
592
00:29:49.339 --> 00:29:52.579
gravity at the edges of galaxies than there is that
593
00:29:52.619 --> 00:29:55.859
you would predict from the stars, et cetera, inside. So, okay,
594
00:29:55.880 --> 00:30:00.960
maybe gravity is different, but nowadays we see gravity where
595
00:30:01.000 --> 00:30:04.940
there is no ordinary matter to cause it. So it's
596
00:30:04.980 --> 00:30:07.339
not just that the strength of gravity is different, but
597
00:30:07.380 --> 00:30:12.900
it's just pointing at something which we're not seeing. So
598
00:30:13.339 --> 00:30:14.299
that's dark matter.
599
00:30:14.700 --> 00:30:18.180
You said a moment ago that, We might one day
600
00:30:18.279 --> 00:30:21.940
need to modify gravity, but that's not what we need
601
00:30:21.980 --> 00:30:23.279
to do to explain dark matter.
602
00:30:23.359 --> 00:30:26.960
It is not sufficient to explain dark matter. We need
603
00:30:27.140 --> 00:30:30.680
extra stuff out there. And just to be super duper clear,
604
00:30:30.740 --> 00:30:34.900
because again, much like the notorious delayed choice quantum eraser experiments,
605
00:30:35.009 --> 00:30:39.190
sometimes people like to make things harder to understand rather
606
00:30:39.230 --> 00:30:41.970
than easier to understand. There are people who have theories
607
00:30:42.029 --> 00:30:45.750
of modified gravity. where they've changed Einstein's theory of gravity
608
00:30:45.769 --> 00:30:48.450
and they say, I can explain away the dark matter.
609
00:30:48.990 --> 00:30:51.549
But when you look at their theory of gravity, in
610
00:30:51.630 --> 00:30:55.180
addition to changing gravity, they've also put new sources of
611
00:30:55.220 --> 00:30:58.279
gravity in there, which are just dark matter. Right.
612
00:30:58.900 --> 00:31:01.079
They break the universe in the process. Right.
613
00:31:01.099 --> 00:31:01.180
Okay.
614
00:31:01.240 --> 00:31:03.539
All right. Well, that's– Okay.
615
00:31:03.720 --> 00:31:09.299
Kevin, kudos for the creative– posing of the question. This
616
00:31:09.359 --> 00:31:13.960
is Rachel Ambrose. And Rachel says, Hey, Rachel here from Austin, Texas.
617
00:31:14.319 --> 00:31:18.089
I'm a big fan of Sean and his Mindscape podcast.
618
00:31:18.230 --> 00:31:19.710
Thank you, Rachel. I've been thinking.
619
00:31:21.589 --> 00:31:22.970
Product placement.
620
00:31:23.130 --> 00:31:27.750
Rachel says, I've been thinking about the spinning universe hypothesis,
621
00:31:28.309 --> 00:31:32.930
which says the entire universe may be rotating very slowly
622
00:31:33.150 --> 00:31:36.539
as a whole and this was hypothesized to help resolve
623
00:31:36.599 --> 00:31:39.200
the Hubble tension. But I was thinking, if it's true,
624
00:31:39.420 --> 00:31:43.059
could this also help us explain dark energy as a
625
00:31:43.180 --> 00:31:48.269
kind of centrifugal force or centrifugal, depending upon how you
626
00:31:48.289 --> 00:31:48.900
want to say it?
627
00:31:50.170 --> 00:31:53.809
Yeah, look, I'll be super honest. And my honest answer is,
628
00:31:54.009 --> 00:31:58.099
I don't know. That sounds like a research program, Rachel
629
00:31:58.119 --> 00:32:00.460
should write a paper about this and submit it to
630
00:32:00.519 --> 00:32:05.789
the physical review. I doubt it is the slightly longer
631
00:32:05.890 --> 00:32:10.869
answer because If the universe is rotating, then that tends
632
00:32:10.950 --> 00:32:13.430
to break the isotropy of the universe.
633
00:32:13.599 --> 00:32:15.380
Okay. God bless you for that.
634
00:32:16.039 --> 00:32:20.220
I'm going to fill you in. Isotropy just means things
635
00:32:20.299 --> 00:32:22.500
look the same in every direction. Okay.
636
00:32:22.519 --> 00:32:25.140
Statistically the same. Statistically the same. Not exactly the same.
637
00:32:25.160 --> 00:32:26.160
Of course. That's right.
638
00:32:26.299 --> 00:32:28.880
So there's not like a big hot spot in one
639
00:32:28.940 --> 00:32:31.160
side of the universe and cold spot in the other side.
640
00:32:31.200 --> 00:32:34.299
It's more or less the same average everywhere with little
641
00:32:34.339 --> 00:32:35.539
fluctuations around it.
642
00:32:36.240 --> 00:32:37.140
And we have that right now.
643
00:32:37.160 --> 00:32:40.410
That's exactly what we have. And so once you start
644
00:32:40.670 --> 00:32:43.390
messing with that, can you mess with it like just
645
00:32:43.430 --> 00:32:45.490
a little bit and maybe no one has noticed yet?
646
00:32:45.910 --> 00:32:46.240
Sure.
647
00:32:46.339 --> 00:32:50.529
You absolutely always can. But It's hard to do that.
648
00:32:50.869 --> 00:32:53.630
And the theory that we have for dark energy with
649
00:32:53.730 --> 00:32:57.390
Einstein's cosmological constant just does a really good job at
650
00:32:57.430 --> 00:32:59.369
fitting the data in a sort of a simple, direct,
651
00:32:59.490 --> 00:33:02.990
blatant kind of here I go kind of way. So
652
00:33:03.009 --> 00:33:06.470
I'm absolutely open to creative new things like the rotation
653
00:33:06.509 --> 00:33:09.789
of the universe. But where would that come from? I'm
654
00:33:09.849 --> 00:33:12.829
not sure. And what other effects would it have on
655
00:33:12.869 --> 00:33:16.990
observable quantities? I'm also not sure. So that sounds like work.
656
00:33:18.019 --> 00:33:19.440
All right. Okay, very cool.
657
00:33:20.440 --> 00:33:24.000
I think we still need verification that that net angular
658
00:33:24.019 --> 00:33:27.640
momentum is Manifest everywhere. I think was just one pocket
659
00:33:27.680 --> 00:33:30.819
of the universe where they made this measurement and and
660
00:33:30.920 --> 00:33:33.579
so you would need to do more of the universe
661
00:33:33.640 --> 00:33:36.220
to Reveal this right if it's really true So it
662
00:33:36.240 --> 00:33:38.700
was just it was the it's which way that spiral
663
00:33:38.720 --> 00:33:41.940
galaxies are rotating, right? Yeah if there's a net rotation
664
00:33:41.980 --> 00:33:44.690
in one direction over here and That says there's something
665
00:33:44.710 --> 00:33:45.829
going on in the whole universe.
666
00:33:46.009 --> 00:33:49.410
Gotcha. Right. Because these galaxies wouldn't know about each other necessarily.
667
00:33:49.569 --> 00:33:51.829
Exactly. There's something in the birth sac. So they're responding
668
00:33:51.849 --> 00:33:53.309
to the same thing if that's the case.
669
00:33:53.410 --> 00:33:54.849
Correct. Gotcha. Correct. Okay.
670
00:33:54.930 --> 00:33:58.509
By the way, just so people know that you got
671
00:33:58.529 --> 00:34:00.839
to be careful about these things. There was one study
672
00:34:00.859 --> 00:34:03.400
that had the brilliant idea. It was a while back.
673
00:34:03.519 --> 00:34:05.579
So we didn't have, you know, the computers weren't there.
674
00:34:06.009 --> 00:34:09.150
They had volunteers. It was like citizen science. They said,
675
00:34:09.210 --> 00:34:13.010
here are some pictures of spiral galaxies. You go through them,
676
00:34:13.070 --> 00:34:17.489
you citizen scientists, and tell us, are they counterclockwise spirals
677
00:34:17.510 --> 00:34:21.110
or are they clockwise spirals? And you would expect it
678
00:34:21.159 --> 00:34:24.519
to be 50-50. But it was like 70-30. Like there
679
00:34:24.539 --> 00:34:27.840
were a lot more clockwise spirals than counterclockwise spirals. And
680
00:34:27.860 --> 00:34:29.619
astronomers were like, oh my God, what is going on?
681
00:34:29.760 --> 00:34:32.449
And someone had the brilliant idea of Okay, let's give
682
00:34:32.510 --> 00:34:35.949
the same galaxies to the same people, but let's take
683
00:34:35.989 --> 00:34:38.570
the mirror image of them. Let's flip them.
684
00:34:39.489 --> 00:34:41.000
Ah, what a smart idea.
685
00:34:41.239 --> 00:34:45.039
And guess what? It was still 70% clockwise galaxies. It
686
00:34:45.340 --> 00:34:49.780
was people were seeing things. People are not unobjective.
687
00:34:49.820 --> 00:34:52.719
Get people out of the equation.
688
00:34:53.389 --> 00:34:55.090
So you just got to be careful about all of
689
00:34:55.110 --> 00:34:55.570
these things.
690
00:34:55.869 --> 00:35:00.269
Sean Browning says, hello, this is Sean Browning from Hood River, Oregon.
691
00:35:01.380 --> 00:35:03.820
In a previous episode, Neil stated that if you were
692
00:35:03.880 --> 00:35:06.219
to fall into a black hole, that would see the
693
00:35:06.400 --> 00:35:10.010
future of the universe unfold.
694
00:35:10.159 --> 00:35:12.730
Or you would see the future of the universe unfold.
695
00:35:12.789 --> 00:35:13.210
Behind you.
696
00:35:13.610 --> 00:35:13.769
Right.
697
00:35:13.809 --> 00:35:14.210
Yeah, yeah.
698
00:35:15.369 --> 00:35:18.289
If that's true, then what would happen if the black
699
00:35:18.349 --> 00:35:23.559
hole finished evaporating before the universe ended?
700
00:35:24.360 --> 00:35:27.400
So I think that the details matter here. You know,
701
00:35:27.579 --> 00:35:29.579
there's a way that we have of thinking about black holes.
702
00:35:30.039 --> 00:35:32.280
That is sort of idealized. Like I wrote a textbook
703
00:35:32.400 --> 00:35:34.539
on general relativity and you can learn about black holes
704
00:35:34.599 --> 00:35:37.730
in there. But the real world black holes are messy
705
00:35:37.849 --> 00:35:40.170
and they're made of stuff and things like that. So
706
00:35:40.190 --> 00:35:43.309
I don't actually think it's true that you see an
707
00:35:43.369 --> 00:35:45.550
enormous amount of the past of the universe in a
708
00:35:45.590 --> 00:35:47.449
real black hole. In a real black hole, you would,
709
00:35:48.050 --> 00:35:51.760
as you know, get spaghettified and die. very quickly right
710
00:35:51.900 --> 00:35:55.519
so right if you're in a real evaporating black hole
711
00:35:55.639 --> 00:35:57.940
you would first get spaghettified and then you would be
712
00:35:58.000 --> 00:36:01.219
released as a stream of uh black body radiation and
713
00:36:01.300 --> 00:36:03.929
you're none of you is experiencing anything here so uh
714
00:36:04.829 --> 00:36:07.070
yeah i think that you don't need to worry like
715
00:36:07.090 --> 00:36:09.989
you would you would see more maybe than you would
716
00:36:10.050 --> 00:36:11.889
if you were outside the black hole but there's no
717
00:36:11.929 --> 00:36:14.110
apparent paradox that you're going to see the whole thing.
718
00:36:15.289 --> 00:36:18.269
Gotcha okay you're uh very literal sean.
719
00:36:22.539 --> 00:36:24.960
But the point is, if your time is slowing down
720
00:36:25.340 --> 00:36:27.300
as you near the black hole, then the time for
721
00:36:27.320 --> 00:36:30.440
the rest of the universe is speeding up, right? I mean,
722
00:36:30.460 --> 00:36:32.780
you see, sorry, you're normal and the rest of the
723
00:36:32.820 --> 00:36:35.480
universe is speeding up. So I think that's the foundation
724
00:36:35.500 --> 00:36:36.139
of this question.
725
00:36:36.199 --> 00:36:36.590
That is.
726
00:36:36.679 --> 00:36:38.630
However long it takes you to fall into the black hole,
727
00:36:38.989 --> 00:36:41.909
will the universe or vice versa, will one of them
728
00:36:42.070 --> 00:36:44.789
live out their days before the other one finishes what
729
00:36:44.829 --> 00:36:45.230
it's doing?
730
00:36:45.409 --> 00:36:45.769
Mm-hmm.
731
00:36:46.099 --> 00:36:48.539
I think you should always think about– I mean what
732
00:36:48.559 --> 00:36:50.239
I would like is that everyone in the world thought
733
00:36:50.280 --> 00:36:56.010
about space-time diagrams and light cones. Your past light cone,
734
00:36:56.389 --> 00:36:58.730
which is the set of all things that can send
735
00:36:58.829 --> 00:37:01.690
light signals to you without moving faster than the speed
736
00:37:01.730 --> 00:37:04.769
of light, it never covers the whole universe. It never
737
00:37:04.829 --> 00:37:07.570
sees the future. It never sees things that are– further
738
00:37:07.610 --> 00:37:09.360
away from you than the speed of light can get.
739
00:37:09.699 --> 00:37:12.019
That's true whether you're inside a black hole or not.
740
00:37:12.260 --> 00:37:15.510
So there's some quantitative question about how much you see,
741
00:37:15.929 --> 00:37:18.170
but there's no worry you're seeing things that didn't happen
742
00:37:18.210 --> 00:37:19.789
yet before the black hole evaporated.
743
00:37:20.119 --> 00:37:23.000
Wow. That's a bummer.
744
00:37:23.679 --> 00:37:27.159
You're the one falling into a black hole. There's other
745
00:37:27.199 --> 00:37:28.880
bummers you have to worry about. Let me tell you.
746
00:37:28.900 --> 00:37:30.980
This is true. It's not your biggest bummer. It's not
747
00:37:31.019 --> 00:37:36.219
the biggest bummer. All right. This is Shadow Dominic. And
748
00:37:36.340 --> 00:37:39.219
he says, hello. Is his name Shadow Dominic? Yeah. All right.
749
00:37:39.480 --> 00:37:42.719
He says, hi, this is Dominic from Madison, Wisconsin. If
750
00:37:42.800 --> 00:37:46.519
you could instantly know the answer to one currently unsolved question,
751
00:37:46.760 --> 00:37:47.699
physics problem.
752
00:37:48.400 --> 00:37:52.940
No strings attached. Was that a pun? No! Yeah, stay
753
00:37:53.000 --> 00:37:55.179
away from string theory. Yeah, was that a pun? What
754
00:37:55.239 --> 00:37:56.079
are you doing, bro?
755
00:37:56.360 --> 00:37:59.050
He says, which one would you pick and why?
756
00:37:59.070 --> 00:38:02.190
I mean, the cheating answer is, yes, tell me the
757
00:38:02.210 --> 00:38:06.250
theory of everything. Then I could work out everything else
758
00:38:06.309 --> 00:38:06.690
from that.
759
00:38:06.789 --> 00:38:11.369
Let me double up behind you. What gives you the
760
00:38:11.429 --> 00:38:14.670
confidence to that a theory of everything even exists.
761
00:38:15.050 --> 00:38:16.289
Because the universe exists.
762
00:38:16.860 --> 00:38:19.559
No, no, no. I'm not accepting that. No, don't tell me.
763
00:38:19.719 --> 00:38:24.179
No, so- You should accept the universe, Neil.
764
00:38:25.139 --> 00:38:30.210
It could be that quantum physics and general relativity in
765
00:38:30.250 --> 00:38:35.280
this universe- never come together, and there's nothing that would
766
00:38:35.360 --> 00:38:37.840
ever bring them together. That's just how the universe is.
767
00:38:38.699 --> 00:38:43.849
We're invoking a philosophical bias of beauty to even assert
768
00:38:44.489 --> 00:38:46.210
That there is one theory of everything.
769
00:38:46.409 --> 00:38:50.730
No, that's not true. The universe exists. There is something
770
00:38:50.769 --> 00:38:55.760
that happens, right? We don't know the best way of
771
00:38:56.019 --> 00:38:59.139
summarizing what happens. The best way of summarizing what happens
772
00:38:59.159 --> 00:39:01.780
in the universe might just be to literally list everything
773
00:39:01.800 --> 00:39:04.340
that happens. That would be a terribly uninformative theory of
774
00:39:04.360 --> 00:39:06.800
the world. We think we can do much better than that.
775
00:39:06.920 --> 00:39:09.369
I'm not saying that the theory of everything is simple
776
00:39:09.489 --> 00:39:11.550
or elegant or fits on a napkin or a T-shirt
777
00:39:11.590 --> 00:39:14.090
or anything like that. but there is some full and
778
00:39:14.130 --> 00:39:16.030
complete description of the universe.
779
00:39:16.329 --> 00:39:19.059
The fact that you said it could be a very
780
00:39:19.480 --> 00:39:22.659
long account of everything that happens, but if it's everything
781
00:39:23.159 --> 00:39:27.420
that happens, then that's everything that happens. So that could
782
00:39:27.440 --> 00:39:31.400
be just a really messy, ugly, not philosophically beautiful theory
783
00:39:31.440 --> 00:39:31.860
of everything.
784
00:39:31.880 --> 00:39:34.019
Because there's a page in the book for everything that happens.
785
00:39:35.570 --> 00:39:38.429
Because I'm very much in agreement with the philosophy that
786
00:39:38.489 --> 00:39:40.469
we should not be going around telling the universe how
787
00:39:40.510 --> 00:39:43.230
to behave. We can't decide ahead of time what the
788
00:39:43.289 --> 00:39:47.280
universe is like. It's absolutely possible. that the ultimate explanations
789
00:39:47.340 --> 00:39:49.760
are not that simple. I actually don't believe that. I
790
00:39:49.780 --> 00:39:52.360
think the ultimate explanation probably will be really, really simple,
791
00:39:52.840 --> 00:39:54.460
but I don't know. Yeah.
792
00:39:54.900 --> 00:39:55.539
What if you.
793
00:39:55.480 --> 00:40:02.599
Can't access that information? Like it is non-accessible on this
794
00:40:03.059 --> 00:40:07.139
plane of existence. But the answer is there. Or you're saying,
795
00:40:07.199 --> 00:40:11.590
are we just too stupid as humans? That's another way
796
00:40:11.610 --> 00:40:12.849
to ask your question.
797
00:40:12.869 --> 00:40:15.309
Yeah, I guess it is. Sean, do you think that
798
00:40:15.869 --> 00:40:19.449
we have sufficient intellect to even get there? Yes. Okay.
799
00:40:19.630 --> 00:40:24.170
All right. That's encouraging. Loving him some Homo sapiens there. Okay.
800
00:40:24.309 --> 00:40:27.599
I mean, again, we don't know, but what I like
801
00:40:27.639 --> 00:40:31.619
to do is just think about how far we've already come.
802
00:40:31.960 --> 00:40:36.139
A hundred years ago, we had just finished getting quantum mechanics.
803
00:40:36.179 --> 00:40:38.619
We didn't know about the expansion of the universe. We
804
00:40:38.659 --> 00:40:41.510
certainly didn't know about quantum fields in the standard model
805
00:40:41.550 --> 00:40:42.429
and all these things.
806
00:40:42.849 --> 00:40:46.199
We didn't know about other galaxies yet that happened in 1926.
807
00:40:46.199 --> 00:40:47.360
Holy moly.
808
00:40:47.400 --> 00:40:47.840
Yeah.
809
00:40:48.340 --> 00:40:51.940
Of course, it's possible we'll never get there. But the
810
00:40:52.039 --> 00:40:54.519
rate at which we've been learning things, and this is
811
00:40:54.559 --> 00:40:57.989
just the past hundred years. Think about the past thousand years.
812
00:40:59.269 --> 00:41:01.469
And 10,000 years from now, we're going to know a lot.
813
00:41:03.309 --> 00:41:06.050
If we're here. Yeah. If we are here.
814
00:41:06.869 --> 00:41:10.099
One of the hypotheses that I thought was intriguing was
815
00:41:10.139 --> 00:41:12.920
that as we measure the limits of whatever the limits
816
00:41:13.019 --> 00:41:16.199
are of what we're measuring... we might reach a cutoff
817
00:41:17.219 --> 00:41:21.800
like in a Truman Show example where he goes to
818
00:41:21.820 --> 00:41:25.239
the horizon, but the horizon is a painted.
819
00:41:26.380 --> 00:41:26.739
Sky.
820
00:41:27.460 --> 00:41:31.019
So we look at like the energy levels of gamma
821
00:41:31.039 --> 00:41:35.860
rays or we find a cutoff that would have no
822
00:41:36.510 --> 00:41:40.789
natural explanation other than that somebody programmed this and they
823
00:41:40.829 --> 00:41:43.519
had to put in a limit. Because they couldn't put
824
00:41:43.559 --> 00:41:45.039
infinity into their software.
825
00:41:45.159 --> 00:41:45.300
Yeah.
826
00:41:45.960 --> 00:41:46.760
Yeah.
827
00:41:46.820 --> 00:41:50.300
So I think that's– it's fascinating to imagine at a
828
00:41:50.349 --> 00:41:54.389
slightly more detailed, careful level what are the ways that
829
00:41:54.429 --> 00:41:57.230
we could become convinced that we're not ever going to
830
00:41:57.269 --> 00:41:59.469
find a simple theory of everything.
831
00:41:59.809 --> 00:42:00.849
That's another way to think about it.
832
00:42:00.849 --> 00:42:00.929
Yeah.
833
00:42:00.949 --> 00:42:04.239
And things like that are– maybe we get evidence that
834
00:42:04.260 --> 00:42:08.079
we live in a simulation or that– The laws of
835
00:42:08.119 --> 00:42:10.820
physics are different from place to place and time to time.
836
00:42:10.880 --> 00:42:12.559
And so even if we get them figured out here,
837
00:42:12.599 --> 00:42:15.619
we won't know them some other way. But again, what's
838
00:42:15.699 --> 00:42:20.650
amazing to me is how rock solid and reliable the
839
00:42:20.690 --> 00:42:24.090
laws of physics are. Like we're able to extrapolate them
840
00:42:24.809 --> 00:42:27.969
way past the environments in which we invent them and
841
00:42:27.989 --> 00:42:31.349
they still work. I just got to put one example
842
00:42:31.409 --> 00:42:35.309
on the table, which– is big bang nucleosynthesis. This is
843
00:42:35.349 --> 00:42:39.030
my favorite example of exactly this. A bunch of scientists,
844
00:42:39.150 --> 00:42:42.150
mostly in the 20th century, figured out the rules of
845
00:42:42.190 --> 00:42:45.380
nuclear physics, the rules of gravity, the rules of cosmology,
846
00:42:45.969 --> 00:42:49.059
and they realized the universe is 14 billion years old,
847
00:42:49.179 --> 00:42:52.840
and they extrapolate these rules back to when the universe
848
00:42:52.900 --> 00:42:56.659
was one minute old. And they make a prediction for
849
00:42:56.719 --> 00:42:59.079
how much hydrogen and helium they should be, and they
850
00:42:59.139 --> 00:43:02.760
got it right. Like, what in the world? That's the
851
00:43:02.800 --> 00:43:05.960
impressive thing to me. Like, we can figure this stuff out.
852
00:43:06.219 --> 00:43:10.349
Fantastic. Well, that's very encouraging.
853
00:43:10.369 --> 00:43:14.190
And there's another example I got from Rich Gott. George
854
00:43:14.230 --> 00:43:20.730
Gamow makes a prediction based on this early nucleosynthesis of
855
00:43:20.769 --> 00:43:26.260
the universe that there should be a residual– temperature of
856
00:43:26.320 --> 00:43:26.909
the universe.
857
00:43:27.389 --> 00:43:30.010
And that would be the temperature pretty much, not pretty much,
858
00:43:30.030 --> 00:43:31.070
that would be the temperature everywhere.
859
00:43:31.110 --> 00:43:31.750
Everywhere, everywhere.
860
00:43:32.409 --> 00:43:36.869
So think of the level of extrapolation this required. And
861
00:43:37.179 --> 00:43:40.179
he said the temperature would be 10 degrees.
862
00:43:41.000 --> 00:43:41.659
Okay? Okay.
863
00:43:41.920 --> 00:43:45.130
So then we finally measure it. It's three degrees.
864
00:43:45.969 --> 00:43:46.289
Wow.
865
00:43:46.469 --> 00:43:47.639
Okay, so you could say.
866
00:43:47.739 --> 00:43:53.500
He was an idiot. He really trapped the bed.
867
00:43:53.519 --> 00:43:56.760
The standards were lower back then, Chuck. It was a
868
00:43:56.780 --> 00:43:57.780
very different time.
869
00:43:58.860 --> 00:44:03.670
But Rich Gott said, that's like predicting that a 10-foot
870
00:44:03.929 --> 00:44:07.889
flying saucer would land on the lawn of the White House,
871
00:44:08.510 --> 00:44:10.090
but it was a three-foot flying saucer.
872
00:44:10.309 --> 00:44:12.860
Right, yeah. That's pretty wild. Oh, my gosh. There's a
873
00:44:12.860 --> 00:44:17.510
flying saucer. No, that's super impressive. Yeah. Yeah. All right.
874
00:44:17.550 --> 00:44:17.949
Very cool.
875
00:44:18.250 --> 00:44:20.849
So you helped me talk me off the ledge there.
876
00:44:21.210 --> 00:44:22.510
You know, every now and then I just wake up
877
00:44:22.550 --> 00:44:25.710
skeptical that we're going to ever figure anything out. And
878
00:44:26.409 --> 00:44:27.750
what we have figured out, I need to be more
879
00:44:27.789 --> 00:44:28.389
impressed with that.
880
00:44:28.429 --> 00:44:29.210
People are impatient.
881
00:44:29.250 --> 00:44:29.789
Yeah, I know.
882
00:44:29.829 --> 00:44:30.929
Like, it'll take some time.
883
00:44:31.639 --> 00:44:35.039
Thank you. So what else you got? All right. This
884
00:44:35.139 --> 00:44:42.250
is Shota, I'll say, Zidzi Gurri. I'm betting that is
885
00:44:42.289 --> 00:44:43.380
so not right, but go on.
886
00:44:43.610 --> 00:44:44.320
Easy for you to say.
887
00:44:46.630 --> 00:44:48.349
All right, Shota Ziziguri.
888
00:44:48.510 --> 00:44:50.969
Anyway, hello, this is Shota from Georgia.
889
00:44:51.050 --> 00:44:52.539
With a name like that? Anyway.
890
00:44:53.260 --> 00:45:00.880
Maybe it's Soviet Georgia. I mean, Georgia, it's not Soviet anymore.
891
00:45:00.900 --> 00:45:03.579
But yeah, I know what you're saying.
892
00:45:04.119 --> 00:45:07.949
Shota says, regarding the many worlds interpretation, is it simply
893
00:45:08.050 --> 00:45:11.429
a mathematical framework we use to describe quantum behavior and
894
00:45:11.469 --> 00:45:15.090
apparent wave function collapse? Or do you think it represents
895
00:45:15.130 --> 00:45:19.079
an actual physical process in which the universe truly branches
896
00:45:19.199 --> 00:45:22.610
into separate real worlds?
897
00:45:22.639 --> 00:45:25.800
How real are these worlds? these other worlds?
898
00:45:26.019 --> 00:45:27.960
Yeah, it's a great question. So the way I like
899
00:45:27.980 --> 00:45:30.480
to think about it is we have an equation, the
900
00:45:30.559 --> 00:45:34.079
Schrodinger equation. You can read about it in my book,
901
00:45:34.199 --> 00:45:38.340
Quanta and Fields, by the way. And the equation makes
902
00:45:38.409 --> 00:45:42.449
predictions for what's going to happen. And the simplest reading
903
00:45:42.510 --> 00:45:45.989
of the prediction is that the universe branches into these
904
00:45:46.050 --> 00:45:50.110
many copies, slightly changed because in one, the electron is
905
00:45:50.130 --> 00:45:53.150
spinning clockwise, in the other, it's counterclockwise, but otherwise the
906
00:45:53.170 --> 00:45:56.090
universe is the same. And we live in one of
907
00:45:56.110 --> 00:45:58.889
those possibilities. We don't see the other ones and it
908
00:45:58.949 --> 00:46:01.210
seems to fit the data. So then you say, okay,
909
00:46:01.230 --> 00:46:03.659
what about all those other possibilities? Should we take them
910
00:46:03.719 --> 00:46:07.059
seriously as real? And the answer is if you take
911
00:46:07.639 --> 00:46:12.099
our possibility as real, then you have two choices. Number one,
912
00:46:12.239 --> 00:46:14.820
either you take the other possibilities as also real. You
913
00:46:14.860 --> 00:46:16.789
treat them equal. They're all there in the equation. I'm
914
00:46:16.809 --> 00:46:20.550
going to take them seriously. Or you tell me why
915
00:46:20.809 --> 00:46:23.909
I shouldn't treat the other ones as real. And there's
916
00:46:23.929 --> 00:46:26.400
a long history of people trying to come up with
917
00:46:26.440 --> 00:46:30.480
reasons why the other worlds aren't there. Disappearing worlds, theories
918
00:46:30.519 --> 00:46:33.260
of quantum mechanics, as Ted Bunn has called them. It
919
00:46:33.320 --> 00:46:35.980
turns out to be hard. It turns out to be awkward.
920
00:46:36.019 --> 00:46:38.199
It doesn't fit in well with modern physics. You can
921
00:46:38.260 --> 00:46:41.000
try to do it. It's a free country. Go nuts.
922
00:46:41.139 --> 00:46:43.780
Invent all the theories of quantum mechanics you want. Or
923
00:46:43.940 --> 00:46:46.820
you can just say, yeah, they're there. I don't care.
924
00:46:46.840 --> 00:46:49.170
They don't bother me. They don't They don't, you know,
925
00:46:49.190 --> 00:46:52.170
like take up the resources we have in our world
926
00:46:52.210 --> 00:46:52.809
or anything.
927
00:46:56.030 --> 00:46:57.610
It's not grabbing a beer in the middle of the
928
00:46:57.639 --> 00:47:04.579
night from your fridge. And just correct me if I'm wrong.
929
00:47:04.960 --> 00:47:07.659
When we think of what's called the Copenhagen interpretation, that's
930
00:47:07.699 --> 00:47:09.179
the many worlds hypothesis, correct?
931
00:47:09.219 --> 00:47:10.050
No, that's the opposite.
932
00:47:10.849 --> 00:47:12.650
The opposite. So describe the opposite.
933
00:47:12.670 --> 00:47:15.269
Copenhagen is the one that was invented by Bohr and
934
00:47:15.289 --> 00:47:16.469
Heisenberg back in the day.
935
00:47:16.829 --> 00:47:19.460
And Bohr is the only one who's Danish. In that pair. Yes,
936
00:47:19.719 --> 00:47:20.179
that is correct.
937
00:47:20.199 --> 00:47:22.139
So why does he get the name– why does his
938
00:47:22.489 --> 00:47:24.289
hometown get the name of the idea?
939
00:47:24.369 --> 00:47:26.530
He was slightly older than everybody else and he founded
940
00:47:26.570 --> 00:47:29.969
the Institute for Theoretical Physics in Copenhagen where all this
941
00:47:30.030 --> 00:47:32.309
work was done. Well, there you go.
942
00:47:32.369 --> 00:47:33.530
He had the money.
943
00:47:34.530 --> 00:47:38.260
Heisenberg was a postdoc at this time and Bohr was
944
00:47:38.300 --> 00:47:46.280
a famous physicist. So Copenhagen puts in the laws of
945
00:47:46.360 --> 00:47:50.280
physics– The notion of measurement. It says that when you
946
00:47:50.300 --> 00:47:54.119
make a measurement of something, a dramatic effect occurs where
947
00:47:54.139 --> 00:47:58.809
the wave function that describes the system completely changes. The
948
00:47:58.909 --> 00:48:03.550
real hardcore Copenhagen philosophy is that there is no such
949
00:48:03.650 --> 00:48:07.010
thing as what the system is doing before you measure it.
950
00:48:07.739 --> 00:48:12.639
The whole of reality consists of nothing but measurement outcomes.
951
00:48:12.699 --> 00:48:14.480
That's what Copenhagen actually says.
952
00:48:15.119 --> 00:48:16.099
Okay.
953
00:48:17.000 --> 00:48:19.920
I remembered learning that, but I didn't connect it with
954
00:48:20.119 --> 00:48:24.059
the Copenhagen interpretation. And if we were divided into camps,
955
00:48:24.079 --> 00:48:27.480
that's my camp. It took me a while to grow accustomed.
956
00:48:27.980 --> 00:48:31.429
Let me restate what you just said. It doesn't even
957
00:48:31.969 --> 00:48:36.369
make sense to talk about it unless there's a measurement
958
00:48:36.429 --> 00:48:39.050
of it. to talk about a state of a system,
959
00:48:39.170 --> 00:48:41.670
unless you can measure it. And then the measurement is
960
00:48:41.710 --> 00:48:45.639
the reality of what things are. Did I oversimplify that?
961
00:48:45.699 --> 00:48:48.760
No, that's actually quite good. And I'm all about, like,
962
00:48:48.780 --> 00:48:51.079
the universe doesn't care about you and your measurements. The
963
00:48:51.119 --> 00:48:53.400
universe is just out there. And I'm just going to
964
00:48:53.440 --> 00:48:57.400
believe in it. Why not? The universe is impersonal, and
965
00:48:57.420 --> 00:48:59.679
the word measurement should not appear in the fundamental laws
966
00:48:59.719 --> 00:49:00.260
of physics.
967
00:49:00.800 --> 00:49:04.449
Wow, that's cool. I like that. I like that. All right.
968
00:49:04.510 --> 00:49:09.969
This is Rory L., who says... Hello, Dr. Tyson, Lord Nice, Dr. Carol.
969
00:49:10.010 --> 00:49:15.309
Rory from Colorado here. The happy recipient of a gift subscription. Wow,
970
00:49:15.329 --> 00:49:18.349
somebody gave him a Patreon gift subscription.
971
00:49:18.429 --> 00:49:21.059
Hey, guess what? You guys can do that. too. Give
972
00:49:21.079 --> 00:49:22.860
a gift subscription to somebody else. Buy him a year
973
00:49:22.880 --> 00:49:26.389
of Patreon. That's a cheap-ass subscription. It really is.
974
00:49:27.110 --> 00:49:29.809
But you can make somebody really happy for not so
975
00:49:29.829 --> 00:49:31.909
much money.
976
00:49:32.170 --> 00:49:32.550
Dr.
977
00:49:32.610 --> 00:49:36.309
Carroll, which science discipline do you rely upon the most
978
00:49:36.409 --> 00:49:41.059
when studying a possible multiverse or is it a combination?
979
00:49:41.719 --> 00:49:42.050
Thanks.
980
00:49:42.360 --> 00:49:45.449
And throw philosophy in there as well as a branch
981
00:49:45.489 --> 00:49:46.610
of thought. Why not? Yes.
982
00:49:47.190 --> 00:49:49.170
I presume that the question is referring to like, is
983
00:49:49.210 --> 00:49:51.510
it mostly a philosophical question or is it mostly a
984
00:49:51.550 --> 00:49:52.590
physics question?
985
00:49:52.730 --> 00:49:56.949
Or is it mostly quantum physics or relativity physics? How
986
00:49:56.969 --> 00:49:58.590
about that? Add that in there.
987
00:49:58.710 --> 00:49:58.889
Right.
988
00:49:58.929 --> 00:50:01.699
Different parts of physics are also very relevant here. But
989
00:50:01.719 --> 00:50:05.039
this is exactly why I chose to title myself Professor
990
00:50:05.059 --> 00:50:07.420
of Natural Philosophy because I don't think that there's a
991
00:50:07.659 --> 00:50:10.719
boundary or a dividing line between the philosophy of it
992
00:50:10.820 --> 00:50:13.380
all and the physics of it all. You are never
993
00:50:13.440 --> 00:50:16.360
going to invent quantum mechanics by sitting around in your
994
00:50:16.530 --> 00:50:19.469
armchair thinking about how the universe would be, right? You
995
00:50:19.510 --> 00:50:23.230
needed experiments that gave you– giving you data that you
996
00:50:23.250 --> 00:50:25.769
couldn't otherwise account for and that's what led us to
997
00:50:25.829 --> 00:50:29.389
quantum mechanics. But then quantum mechanics leads us to this
998
00:50:29.469 --> 00:50:32.070
idea of many worlds happening every time you make a
999
00:50:32.090 --> 00:50:37.099
quantum measurement. And philosophy becomes super important for accounting for that,
1000
00:50:37.119 --> 00:50:40.860
for understanding that. The physicists, bless their hearts, have done
1001
00:50:40.880 --> 00:50:43.940
a terrible job. Most of them just live in denial
1002
00:50:44.059 --> 00:50:46.539
and don't even want to think about this. And it's
1003
00:50:46.599 --> 00:50:49.420
kind of an embarrassment, but The philosophers have at least
1004
00:50:49.440 --> 00:50:51.800
taken up the challenge. I don't think that we're done yet.
1005
00:50:51.820 --> 00:50:54.190
I don't think we have a perfect understanding of everything.
1006
00:50:54.230 --> 00:50:56.809
That's good. That's good for me. Full employment for me
1007
00:50:56.849 --> 00:50:59.090
and my graduate students. We still have things left to do.
1008
00:50:59.469 --> 00:51:01.250
But I think you need them all. There's no one
1009
00:51:01.309 --> 00:51:01.789
answer there.
1010
00:51:02.269 --> 00:51:05.139
As everyone from the South knows. If you say bless
1011
00:51:05.179 --> 00:51:07.559
his heart, the next thing is going to be a
1012
00:51:08.000 --> 00:51:08.780
nasty insult.
1013
00:51:08.860 --> 00:51:09.360
Well, yeah.
1014
00:51:09.440 --> 00:51:15.369
In the South, bless his heart means F you. They
1015
00:51:15.409 --> 00:51:18.349
got it down to a science. The most polite F
1016
00:51:18.369 --> 00:51:19.349
you possible.
1017
00:51:19.570 --> 00:51:20.130
Bless his heart.
1018
00:51:20.170 --> 00:51:22.469
Bless his heart. This is John Mayer. He says, hi,
1019
00:51:22.489 --> 00:51:26.070
I'm John from San Diego. And listen, every episode I
1020
00:51:26.110 --> 00:51:29.780
listen to, it's my jam. Thank you, dear Dr. Tyson
1021
00:51:29.940 --> 00:51:30.460
and Dr.
1022
00:51:30.519 --> 00:51:35.179
Carroll. Can we, can we, can we? Advertise that? StarTalk,
1023
00:51:35.440 --> 00:51:41.380
it's your jam. He says, Dr. Tyson, Dr.
1024
00:51:41.420 --> 00:51:44.239
Carol, and the energetic Lord Nice, please help me understand
1025
00:51:44.300 --> 00:51:47.710
how a photon traveling between stars experiences no time, yet
1026
00:51:47.809 --> 00:51:51.409
also has a wavelength pattern and changes over space and time.
1027
00:51:51.789 --> 00:51:54.829
Is the wavelength a function of the photon or is
1028
00:51:54.889 --> 00:51:59.360
it a display function of the space-time medium within which
1029
00:51:59.420 --> 00:52:00.900
it is traveling within?
1030
00:52:01.300 --> 00:52:05.590
Or is it even something else? What a great question.
1031
00:52:06.239 --> 00:52:09.159
People love this question. I get this question. And they
1032
00:52:09.179 --> 00:52:12.050
don't like the answer, which is that photons don't experience things.
1033
00:52:12.070 --> 00:52:15.610
They're just single particles. Electrons don't experience things either. I
1034
00:52:16.389 --> 00:52:21.639
think that we get in trouble because we are complicated creatures, right,
1035
00:52:21.719 --> 00:52:24.900
with senses and memories and things like that. We have
1036
00:52:24.940 --> 00:52:28.159
a feeling for what it is like for time to pass.
1037
00:52:28.659 --> 00:52:30.900
And that wouldn't apply if we were moving at the
1038
00:52:30.940 --> 00:52:34.820
speed of light because then no time would pass. But
1039
00:52:35.179 --> 00:52:37.530
when we talk about the wavelength of a photon or
1040
00:52:37.570 --> 00:52:40.409
its path through the universe, we're not talking about its
1041
00:52:40.690 --> 00:52:44.050
inner experience. We're not talking about its first-person point of view.
1042
00:52:44.070 --> 00:52:46.349
We're talking about what it looks like to us. The
1043
00:52:46.409 --> 00:52:49.429
photon passes us by. It has a wavelength. It has
1044
00:52:49.469 --> 00:52:50.210
a path. Mm-hmm.
1045
00:52:50.710 --> 00:52:52.610
So it's all about us.
1046
00:52:52.710 --> 00:52:55.849
It's all about us. It's all about us. Well, even better,
1047
00:52:55.909 --> 00:52:59.239
it's all relative, as Einstein would have said. It's relative
1048
00:52:59.260 --> 00:53:00.800
from what the observer sees.
1049
00:53:01.320 --> 00:53:03.099
It's relative to the observer. Yeah.
1050
00:53:03.159 --> 00:53:05.440
And it's also about the math, because that's the thing
1051
00:53:05.480 --> 00:53:07.920
that people do. The photon is a particle, but the
1052
00:53:08.079 --> 00:53:11.420
math is why it doesn't experience time. It has no
1053
00:53:11.500 --> 00:53:14.099
mass and it's traveling at the speed of light. So
1054
00:53:14.280 --> 00:53:16.369
there is no time. There just isn't.
1055
00:53:16.550 --> 00:53:20.090
That's right. It travels through a path in space time
1056
00:53:20.349 --> 00:53:22.949
that takes it no time from its point of view.
1057
00:53:22.969 --> 00:53:23.909
Right. Okay.
1058
00:53:24.510 --> 00:53:30.280
However, if you look at muons, a muon... knows when
1059
00:53:30.340 --> 00:53:30.940
to decay.
1060
00:53:31.519 --> 00:53:32.400
Ooh, that's right.
1061
00:53:32.460 --> 00:53:34.699
So it must have an internal clock. For you to
1062
00:53:34.739 --> 00:53:37.500
just say a particle, and you even mentioned electrons, doesn't
1063
00:53:37.579 --> 00:53:40.400
care about time. If I'm a decaying particle, I do
1064
00:53:40.440 --> 00:53:42.159
care about time. Ooh!
1065
00:53:42.500 --> 00:53:44.059
So there. Ooh!
1066
00:53:44.099 --> 00:53:49.989
You guys got to stop anthropomorphizing elementary particles.
1067
00:53:51.090 --> 00:53:53.030
You want to say, you ready to go? You ready
1068
00:53:53.050 --> 00:53:55.710
to jump out of this one? That's right. Let's go together.
1069
00:53:55.750 --> 00:54:00.429
Hold hands. That's great. That's great. Yeah.
1070
00:54:00.469 --> 00:54:03.869
There is time that the extent of a muon's path
1071
00:54:03.889 --> 00:54:07.789
through the universe does include a passage of time. But
1072
00:54:07.809 --> 00:54:10.670
the muon as an elementary particle has no hopes or desires.
1073
00:54:10.969 --> 00:54:14.159
Sorry. Poor muon.
1074
00:54:16.239 --> 00:54:16.429
All right.
1075
00:54:16.449 --> 00:54:18.719
Time for one last question. All right. This is Ben
1076
00:54:18.920 --> 00:54:22.639
Grund or Grund. He says, hello, smart people.
1077
00:54:22.739 --> 00:54:25.880
Ben from Novi, Michigan says, I think Sean helped me
1078
00:54:25.969 --> 00:54:29.199
understand entropy best in his books and lectures. Charles Liu
1079
00:54:29.239 --> 00:54:33.219
made an interesting comment recently that time can be measured
1080
00:54:33.300 --> 00:54:39.699
by entropy. I was wondering, is entropy creating time in
1081
00:54:39.820 --> 00:54:43.780
some strange way? Thanks for all the blown gaskets.
1082
00:54:43.800 --> 00:54:48.119
Brain gaskets. Exactly.
1083
00:54:48.440 --> 00:54:52.019
Let me add some extra punctuation in that question. If
1084
00:54:53.159 --> 00:54:58.590
entropy goes up with the passage of time, allowing us
1085
00:54:58.670 --> 00:55:02.800
to deduce the arrow of time by seeing systems left
1086
00:55:02.840 --> 00:55:06.880
to themselves as we watch entropy rise within them. Could
1087
00:55:06.920 --> 00:55:09.360
it be that entropy goes up no matter what the
1088
00:55:09.440 --> 00:55:14.860
universe is doing, even if it were re-collapsing? Or is
1089
00:55:14.960 --> 00:55:19.679
the entropy intricately connected to an expanding universe? So that
1090
00:55:19.909 --> 00:55:23.989
even if we, so even if we re-collapsed, the entropy
1091
00:55:24.010 --> 00:55:25.019
would continue to go up.
1092
00:55:25.889 --> 00:55:28.590
As far as we know, there's no connection between whether
1093
00:55:28.610 --> 00:55:30.610
entropy goes up and down and whether the universe is
1094
00:55:30.650 --> 00:55:33.380
expanding or contracting. You could have it any way. There's
1095
00:55:33.440 --> 00:55:36.719
an empirical fact about our universe that entropy was low
1096
00:55:36.840 --> 00:55:39.119
when the universe was relatively tiny and has been growing
1097
00:55:39.159 --> 00:55:42.619
ever since. But if it started collapsing, we expect that
1098
00:55:42.699 --> 00:55:46.469
entropy would still be going up toward the future. And
1099
00:55:46.489 --> 00:55:49.510
that's part of the actual answer to the question, which
1100
00:55:49.590 --> 00:55:53.269
is that you have to distinguish between time– And the
1101
00:55:53.570 --> 00:55:56.880
arrow of time, time could exist without an arrow. And
1102
00:55:56.900 --> 00:56:00.590
the fact that entropy provides time with an arrow doesn't
1103
00:56:00.610 --> 00:56:03.969
mean that it explains or accounts for time itself. Like
1104
00:56:04.289 --> 00:56:06.610
here in this room where I am, If I take
1105
00:56:07.070 --> 00:56:09.570
my coffee mug and I let it go, it falls
1106
00:56:09.670 --> 00:56:11.619
to the ground. It falls down. It doesn't fall up.
1107
00:56:12.110 --> 00:56:14.809
There's an arrow of space here in the room. There's
1108
00:56:14.829 --> 00:56:18.440
a clear distinction between up and down. But it's because
1109
00:56:18.460 --> 00:56:21.579
the earth is beneath my feet. It's not because the
1110
00:56:21.619 --> 00:56:25.960
earth is creating space. The earth is just distinguishing between
1111
00:56:26.039 --> 00:56:28.960
two different directions in space up and down. That's what
1112
00:56:29.079 --> 00:56:30.420
entropy does for the universe.
1113
00:56:31.420 --> 00:56:33.820
I like that. That's great. That was really good, man.
1114
00:56:34.039 --> 00:56:36.440
But wait, but if we re-collapse and the whole universe
1115
00:56:36.519 --> 00:56:41.010
then occupies a small volume, isn't that necessarily a lower
1116
00:56:41.110 --> 00:56:41.909
entropy universe?
1117
00:56:42.429 --> 00:56:42.570
Nope.
1118
00:56:43.570 --> 00:56:43.869
What?
1119
00:56:45.570 --> 00:56:45.829
What?
1120
00:56:46.630 --> 00:56:49.550
Don't leave me hanging. We have to end now. You
1121
00:56:49.570 --> 00:56:51.170
can't leave me hanging like with a nope.
1122
00:56:51.210 --> 00:56:53.469
We got to go. All right. Bye, everyone.
1123
00:56:54.380 --> 00:56:56.400
It was like, take it easy.
1124
00:56:56.539 --> 00:56:57.059
Bye.
1125
00:56:57.119 --> 00:57:01.019
Have a beautiful time.
1126
00:57:01.800 --> 00:57:04.199
We learned from statistical mechanics where you have this like
1127
00:57:04.239 --> 00:57:07.110
blob of gas. and you just let it go and
1128
00:57:07.130 --> 00:57:12.389
then it will expand and its entropy will go up
1129
00:57:12.639 --> 00:57:17.360
because there's more places the particles can occupy and it's
1130
00:57:17.380 --> 00:57:20.739
not contained within a volume. If the universe is shrinking,
1131
00:57:21.780 --> 00:57:23.719
the whole universe is in a smaller and smaller and
1132
00:57:23.760 --> 00:57:26.420
smaller volume. How could you tell me that that universe
1133
00:57:26.440 --> 00:57:27.840
can also have an increase in entropy?
1134
00:57:28.539 --> 00:57:30.480
Do you think eggs are going to start unscrambling just
1135
00:57:30.500 --> 00:57:31.739
because the universe starts shrinking?
1136
00:57:32.599 --> 00:57:32.940
Yes!
1137
00:57:36.019 --> 00:57:37.809
Please don't think that, Neil deGrasse Tyson.
1138
00:57:37.949 --> 00:57:38.349
Okay.
1139
00:57:38.750 --> 00:57:40.070
No, that makes sense. All right.
1140
00:57:40.090 --> 00:57:40.190
Okay.
1141
00:57:40.829 --> 00:57:42.369
Yeah. The eggs are broken.
1142
00:57:42.429 --> 00:57:46.130
They're in the bain marie and that's it. You've scrambled
1143
00:57:46.150 --> 00:57:46.829
them up. All right.
1144
00:57:46.969 --> 00:57:49.650
Just in case there's anyone who really wants it out there.
1145
00:57:49.670 --> 00:57:52.210
I mean, Neil's given a very good reason to think
1146
00:57:52.289 --> 00:57:56.250
that entropy should go down. And the secret to, you know,
1147
00:57:56.289 --> 00:57:58.090
for a little bit more technicality, because it's the end
1148
00:57:58.110 --> 00:58:02.909
of the podcast, we should care about phase space, not space.
1149
00:58:03.030 --> 00:58:04.510
That is to say, we should think about both the
1150
00:58:04.590 --> 00:58:09.469
positions of particles and also their velocities. So the positions
1151
00:58:09.510 --> 00:58:12.280
of particles are indeed going to get squeezed together if
1152
00:58:12.320 --> 00:58:15.980
the universe collapses. But the velocities are going to spread
1153
00:58:16.019 --> 00:58:18.719
all out and do crazy things and increase the entropy
1154
00:58:18.989 --> 00:58:21.309
of the whole configuration. And in fact, it's going to
1155
00:58:21.349 --> 00:58:24.849
look wildly inhomogeneous with black holes and empty regions. And
1156
00:58:24.889 --> 00:58:28.429
it's going to look nothing like our early universe looked.
1157
00:58:29.239 --> 00:58:34.940
Wow. Man, you're good. I'm old.
1158
00:58:34.960 --> 00:58:36.760
I've done this before. Not my first rodeo.
1159
00:58:36.800 --> 00:58:40.239
What can I tell you? So, Sean, Quantum and Fields,
1160
00:58:40.280 --> 00:58:40.780
that was 2024?
1161
00:58:40.780 --> 00:58:44.030
That was 2024. And the one I'm supposed to be
1162
00:58:44.050 --> 00:58:48.750
finishing up right now is called Complexity and Emergence 2026.
1163
00:58:48.960 --> 00:58:50.340
Nice. All right. Nice.
1164
00:58:50.380 --> 00:58:50.800
Look at that.
1165
00:58:50.980 --> 00:58:54.599
And after that, that's the trinity of the universe. You're done. Yeah.
1166
00:58:54.739 --> 00:58:55.539
You go to Bahamas.
1167
00:58:55.579 --> 00:58:58.570
I figure like the trilogy format worked well for J.R.R.
1168
00:58:58.739 --> 00:58:59.139
Tolkien.
1169
00:58:59.179 --> 00:59:03.630
It should work well for me too. I'm waiting for
1170
00:59:03.650 --> 00:59:06.590
the adaptation. And then you escape to Middle Earth and
1171
00:59:06.610 --> 00:59:07.329
all as well.
1172
00:59:07.349 --> 00:59:11.659
Right. We find you online with. the Preposterous Universe. That's right.
1173
00:59:11.840 --> 00:59:13.719
And a lot of my work these days, you know,
1174
00:59:13.739 --> 00:59:16.059
talking out there is in the podcast format with the
1175
00:59:16.099 --> 00:59:17.340
Mindscape podcast.
1176
00:59:17.860 --> 00:59:20.440
Yeah. Mindscape. And how often do you drop those?
1177
00:59:20.840 --> 00:59:21.590
Every single week.
1178
00:59:22.090 --> 00:59:22.690
Wow. All right.
1179
00:59:22.710 --> 00:59:23.250
Very nice.
1180
00:59:23.289 --> 00:59:26.369
Very nice. And at least some of your fans came
1181
00:59:26.409 --> 00:59:27.889
through us to get back to you again.
1182
00:59:28.090 --> 00:59:28.650
Absolutely.
1183
00:59:28.730 --> 00:59:29.869
We're delighted by that.
1184
00:59:29.889 --> 00:59:30.630
Podcast pros.
1185
00:59:30.750 --> 00:59:30.969
Yeah.
1186
00:59:31.170 --> 00:59:33.889
Well, Sean, delighted to see you again. Next time I'm
1187
00:59:34.110 --> 00:59:35.750
in Baltimore, I'll give you a call. I was there
1188
00:59:35.769 --> 00:59:37.610
actually a few months ago. I just forgot to call you.
1189
00:59:38.429 --> 00:59:41.179
It's going in your permanent record.
1190
00:59:41.719 --> 00:59:44.260
You don't really have to tell me that. That's true.
1191
00:59:45.739 --> 00:59:48.300
That's something you can keep to yourself. You know what
1192
00:59:48.420 --> 00:59:49.820
I mean? Yeah. Yeah.
1193
00:59:49.940 --> 00:59:52.320
A hundred percent. Next time we're on the podcast, he's
1194
00:59:52.340 --> 00:59:54.059
going to be saying, yeah, I went back to Baltimore again.
1195
00:59:54.099 --> 00:59:54.559
I forgot.
1196
00:59:57.440 --> 00:59:58.949
Strange how I forget every single time.
1197
00:59:59.639 --> 01:00:01.269
Sean, delight to see you once again.
1198
01:00:01.289 --> 01:00:01.690
All right.
1199
01:00:01.769 --> 01:00:02.010
Yeah.
1200
01:00:02.050 --> 01:00:02.909
All right. Good stuff.
1201
01:00:02.969 --> 01:00:08.110
This has been StarTalk Cosmic Queries. Yet another cosmology edition.
1202
01:00:08.130 --> 01:00:10.889
I love these. No end of people's curiosity.
1203
01:00:11.570 --> 01:00:14.269
Chuck, you doing good? Always a pleasure, man. This was
1204
01:00:14.309 --> 01:00:15.250
so much fun. All right.
1205
01:00:15.309 --> 01:00:19.969
Neil deGrasse Tyson, your personal astrophysicist. Until next time, keep
1206
01:00:20.010 --> 01:00:20.400
looking up.