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Speaker 1: Hey, Daniel, what are we doing today for the opening

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Speaker 1: of the podcast? You know, actually I thought maybe we

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Speaker 1: would invert the usual process. We have a usual process. Yeah,

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Speaker 1: first we have an idea and then we record it.

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Speaker 1: So you want to flip it today? So what does

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Speaker 1: that mean? We're gonna start recording and then hope we

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Speaker 1: get an idea. Isn't that like putting costs after effect? Yeah,

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Speaker 1: you know, just a little causality inversion to start your day?

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Speaker 1: What could go wrong? It's never a good sign when

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Speaker 1: the physicist says what could go wrong? Well, you know,

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Speaker 1: we haven't destroyed the universe yet, but what if we

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Speaker 1: blow up the universe with this inverted opening? Oh, and

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Speaker 1: that gives me an idea for a perfect opening. Hopefully

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Speaker 1: people laughed before they listen to that. Hi am Jorgemming,

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Speaker 1: cartoonists and the creator of PhD comics. Hi. I'm Daniel.

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Speaker 1: I'm a particle physicist and a physics professor at u

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Speaker 1: C Irvine, and I usually don't know what I'm going

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Speaker 1: to say before I say it. Isn't that part of

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Speaker 1: the job description for a professor not knowing what you're

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Speaker 1: talking about exactly, but making it sound like you do,

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Speaker 1: and that's where the PhD comes from. I guess years

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Speaker 1: of training. Welcome to our podcast, Daniel and Jorge Explain

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Speaker 1: the Universe, a production of My Heart Radio in which

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Speaker 1: we are not afraid to admit what we don't know

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Speaker 1: about the universe because we love to embrace that ignorance.

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Speaker 1: We dive deep into everything that we don't understand about

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Speaker 1: the universe, the very nature of space and time, the

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Speaker 1: context of the reality around us, all of the squishy

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Speaker 1: and beautiful and incredible matter that fills it and wiggles

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Speaker 1: around inside of it. We are desperate to understand the

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Speaker 1: deep nature of the universe, and we are here to

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Speaker 1: explore it and explain it to you. Yeah, because there

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Speaker 1: is a lot we don't know about the universe. And

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Speaker 1: I'm not just talking about myself a cartoonist, but there's

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Speaker 1: a lot that even physicists don't know about, not just

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Speaker 1: things hidden inside of black holes or neutron stars or

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Speaker 1: inside of particles. There's some very fundamental questions we still

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Speaker 1: have about this wild and wacky universe. Yeah, exactly, like

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Speaker 1: where did I put my phone? And how come I

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Speaker 1: can never find an even number of socks at the

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Speaker 1: same time, I think maybe you put the phone in

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Speaker 1: your socks. That would solve if I could just have

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Speaker 1: like digital socks so I could have them on my phone,

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Speaker 1: that would be so much more convenient. Well, I know

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Speaker 1: you like to wear sandals, so I'm pretty sure you

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Speaker 1: already have virtual socks. Yeah, exactly. That's why I could

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Speaker 1: just delete all the socks in one film. But it's

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Speaker 1: not really just sucks that we are curious about. We

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Speaker 1: really do want to understand the deep nature of reality

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Speaker 1: around us. What is this universe? How did it come

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Speaker 1: to me? Why is it this way and not another way?

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Speaker 1: And most importantly, are there things about it that we're

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Speaker 1: getting basically wrong? Yeah, because you know, I feel like

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Speaker 1: you can ask questions about the universe and the stuff

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Speaker 1: in the universe us, you know, like black holes and

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Speaker 1: stars and particles, but you can also kind of ask deep,

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Speaker 1: kind of philosophical questions about it. You know, it's sort

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Speaker 1: of like about the nature of it or what can

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Speaker 1: break the universe even Yeah, because we know that in

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Speaker 1: human history we've made a lot of basic mistakes about

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Speaker 1: the way we thought the universe worked, because we've only

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Speaker 1: seen it work in one particular way or in one

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Speaker 1: set of circumstances, and we imagined that must be true forever,

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Speaker 1: it must be a deep truth about the universe, and

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Speaker 1: it turns out not so much, which means that what

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Speaker 1: lies ahead of us is more discoveries that basic assumptions

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Speaker 1: about the nature of the universe are probably wrong, and

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Speaker 1: it might just be that we need to hammer at

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Speaker 1: these things forever, or wait till the aliens arrive and

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Speaker 1: give us some other context for looking at the nature

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Speaker 1: of the universe. But that's cheating, Daniel. Are they also

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Speaker 1: going to tell you where your socks are? Are you

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Speaker 1: gonna be that irresponsible? They're gonna email us socks. It's

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Speaker 1: gonna be nice digital socks. That's not cheating at all.

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Speaker 1: I think the first Galactic physics conference will be, you know,

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Speaker 1: a great melding of lines. If you think that's cheating,

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Speaker 1: then you know physicist shouldn't work together at all. We

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Speaker 1: should all be trying to figure out the universe on

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Speaker 1: our own. Well, but do you think it'd be the

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Speaker 1: two way conference with us and the aliens? Do you

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Speaker 1: think we have anything to teach them? Are we joking

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Speaker 1: over being serious? I don't know. I mean, if they

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Speaker 1: can travel through the stars, and you know, invent warp drives.

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Speaker 1: Do you think we have anything to teach them or

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Speaker 1: do you think we know something they don't? At this point,

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Speaker 1: I think it's very likely that everything we've learned in

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Speaker 1: our human sciences is probably corrupted by human bias and

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Speaker 1: totally useless to aliens, not just because we haven't made

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Speaker 1: advances far enough, but probably just the questions we ask

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Speaker 1: in the nature of the way we answer them is

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Speaker 1: probably deeply inherently human in ways we can't even imagine.

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Speaker 1: You know, we don't even really know where the edge

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Speaker 1: of the box is. We just know that we're in

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Speaker 1: this sort of like human constructed box about ways to

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Speaker 1: think about the universe. And it isn't until the aliens

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Speaker 1: come that will even figure out like where the edge

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Speaker 1: of that box is. Yeah, I guess because we we've

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Speaker 1: been trying to figure everything out with the human brain.

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Speaker 1: And you know what if you have a totally different

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Speaker 1: maybe you get to see things in a very different way, yeah,

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Speaker 1: or different sensory organs. Right, what if you can see

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Speaker 1: X rays, or you can smell photons, or you can

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Speaker 1: taste electrons or something like that, Right, you might have

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Speaker 1: figured out totally different ways to think about the universe

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Speaker 1: in a completely different order. Maybe quantum mechanics is intuitive

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Speaker 1: to them because you know, they've seen this stuff happening

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Speaker 1: in front of them every single day. Or maybe they

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Speaker 1: can see neutrinos and so the universe is like totally

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Speaker 1: opaque and very weird to them. It's going to be

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Speaker 1: a challenge to map from human brains to alien brains.

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Speaker 1: Sometimes it's hard to even map from human brain to

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Speaker 1: human brain. Yeah, So I think what you're saying is

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Speaker 1: that sometimes there are revolutions and human thought where we

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Speaker 1: thought that the universe worked one way and then it

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Speaker 1: turns out it worked another way, right, Like maybe quantum

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Speaker 1: physics is one of those big revolutions, or relativity exactly.

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Speaker 1: Those two are the best examples of moments when we

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Speaker 1: realized that fundamentally the universe is very different from the

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Speaker 1: way we imagined. And I think we put those on

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Speaker 1: the scale of other kinds of realizations, like discovering that

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Speaker 1: the Earth is not the center of the Solar System

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Speaker 1: or even the cosmos, or discovering that our galaxy is

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Speaker 1: one of trillions of galaxies instead of the entire cosmos.

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Speaker 1: You know, these kinds of things help us understand not

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Speaker 1: just the nature of the universe around us, but our

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Speaker 1: place in it, in the context of our very existence.

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Speaker 1: So these are pretty deep potential revolutions in our understanding

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Speaker 1: of the nature of the universe. Yeah, and do you

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Speaker 1: think that has made fits This is a little bit

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Speaker 1: paranoid almost in a way like now you doubt everything,

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Speaker 1: like even the basics, you know, logic of the universe. Right. No,

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Speaker 1: it makes this excited because it means that around every

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Speaker 1: corner is a potential explosion of ideas. You can tug

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Speaker 1: on any random thread and pull the whole thing apart.

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Speaker 1: Paranoid makes it sound like we're afraid to pull the

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Speaker 1: whole thing apart. We are desperate to pull it apart

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Speaker 1: because it will reveal something else, something new that we

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Speaker 1: can chew on, where we can make new progress and

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Speaker 1: ask new questions. That's the dream come true. I think

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Speaker 1: being afraid of explosions at every corner is sort of

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Speaker 1: the definition of making being paranoid. But you're saying, and

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Speaker 1: you're paranoid in a good way. You're like a good paranoid,

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Speaker 1: a good kind of parentig is somehow you walk me

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Speaker 1: into that corner. But yes, I am now admitting I'm

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Speaker 1: a good kind of paranoid. But yeah, you can ask

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Speaker 1: pretty deep questions about the universe, and so today we're

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Speaker 1: asking a pretty challenging question. I mean in the sense

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Speaker 1: that it challenges something very deep and sort of I

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Speaker 1: don't know, logical and basic about the universe that you know,

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Speaker 1: maybe a lot of people don't even think you can

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Speaker 1: even ask. That's right. It's something that's so fundamental to

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Speaker 1: the universe that even is incorporated in how we explain

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Speaker 1: the universe itself. It's something inherent I think in the

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Speaker 1: way humans think and the way we tell stories and

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Speaker 1: think about what makes sense and what doesn't make sense. Yeah,

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Speaker 1: So to be on the program, we'll be asking the

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Speaker 1: question does the universe need cause and effect? WHOA Daniel?

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Speaker 1: This kind of blew my mind. I mean, how can

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Speaker 1: you how can you question cause and effect and causality

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Speaker 1: in the universe? Are you saying there's some effects to

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Speaker 1: question and causes? Yeah? Yeah. The effect of asking this

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Speaker 1: question is it's gott me really confused. I know. I

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Speaker 1: think it's so fundamental to the way we think, you know,

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Speaker 1: we the way we explain things to ourselves, as we

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Speaker 1: tell stories and stories go like a happened, and then

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Speaker 1: be happened, and then see happened. That's the way we talk,

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Speaker 1: that's the way we think, that's the way we organize

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Speaker 1: our minds, and so it's pretty hard to imagine that

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Speaker 1: you could have a universe without cause and effect. On

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Speaker 1: the other hand, just because it's part of our minds

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Speaker 1: doesn't mean it has to be part of the universe, right.

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Speaker 1: The whole goal of physics is to break out of

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Speaker 1: that box and understand something universal instead of something human. Now, Daniel,

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Speaker 1: is this related to like the idea of the arrow

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Speaker 1: of time or is this sort of like a basic

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Speaker 1: kind of thing about the universe where like things can

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Speaker 1: happen without being connected to other things. Do you know

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Speaker 1: what I mean? Yeah, definitely it's connected to the question

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Speaker 1: of time, because cause and effect orders things. And we'll

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Speaker 1: talk about this in more detailed later. You know, there's

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Speaker 1: this concept of like a light cone, which organizes the

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Speaker 1: order of events. Things have to happen in the universe,

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Speaker 1: But that's only true if you have causality. If things

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Speaker 1: have to happen in a certain order. Things don't have

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Speaker 1: to happen in a certain order. That whole picture might

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Speaker 1: go out the window. Whoa, And that's you know, totally

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Speaker 1: opposite from our everyday experience, right, Like our everyday experience

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Speaker 1: is that effects do follow causes, right absolutely. You know,

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Speaker 1: if your friends don't like, arrive for dinner before you

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Speaker 1: invite them, you should meet my friends. Introverts don't have

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Speaker 1: guests rorive for dinner before you invite them. You know.

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Speaker 1: It's like if you send somebody a message, they can't

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Speaker 1: read the message before you send it. Right, the kind

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Speaker 1: of thing would violate causality. It's definitely connected with the

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Speaker 1: flow of time because it has to do with like,

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Speaker 1: you know, sending messages back in time. One of the

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Speaker 1: reasons we always say that you can't travel back in

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Speaker 1: time is that it would violate causality. You would have

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Speaker 1: effects that influence the our own causes. Right. It's like

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Speaker 1: very basic to the way we think about the universe,

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Speaker 1: stepping forwards in time, flowing from now to the future.

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Speaker 1: All right, Well, then the question is do we actually

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Speaker 1: need causality? Do we do we need costs and effect

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Speaker 1: in the universe to make it work or are you

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Speaker 1: saying it's sort of maybe like an illusion or something

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Speaker 1: that's apparent, but not really needed in the universe. What

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Speaker 1: are we actually asking here? I think the question is

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Speaker 1: whether it's always needed? You know, this is the kind

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Speaker 1: of thing that we observe in the universe. It is

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Speaker 1: definitely part of the universe. But just like with relativity

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Speaker 1: and quantum mechanics, there are some places where it seems

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Speaker 1: like it might not hold together, some like little threads

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Speaker 1: where it doesn't really work and it isn't really consistent

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Speaker 1: with some other basic principles, And that gives us a

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Speaker 1: clue that maybe it's not always required, and maybe like

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Speaker 1: it comes together in certain circumstances. It's a nice way

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Speaker 1: to describe what often happens in the universe, but it's

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Speaker 1: not actually a fundamental principle, and we can find some

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Speaker 1: places where it's tossed out the window. So I who

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Speaker 1: would be the one we cause out? Cause or effect?

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Speaker 1: Which one do you like better? I prefer horses to cow,

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Speaker 1: so let's throw out cowsality is it cost or effect? Well? Anyways,

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Speaker 1: we were, as usual, wondering how many people out there

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Speaker 1: had thought about this crazy, deep, fundamental question, and how

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Speaker 1: many people think they might have an answer to this

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Speaker 1: strange query. So Daniel went out there to the internet

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Speaker 1: to ask people do we need cause and effect? So

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Speaker 1: thank you everybody out there on the Internet who is

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Speaker 1: willing to answer these funny, crazy questions without having a

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Speaker 1: chance to think about it or google it. If you'd

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Speaker 1: like to do then it sounds fun. Do you please

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Speaker 1: write to us two questions at Daniel and Jorge dot com.

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Speaker 1: We want your voice, so think about it for a second.

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Speaker 1: Do you think the universe needs cause and effect? Here's

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Speaker 1: what people had to say. I think that we as

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Speaker 1: human beings probably need it. Whether the universe needs it

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Speaker 1: or existence, probably not. I can imagine a crazy universe

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Speaker 1: where everything was upside down and happened of its own coalition,

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Speaker 1: But as people, I think we wouldn't do very well

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Speaker 1: in such a place. I don't know much about this.

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Speaker 1: That makes me think of the Matrix when the marrow

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Speaker 1: Vingian is talking about cause and causality or something like that. Um,

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Speaker 1: I understood about that about as much as I understood

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Speaker 1: most of that movie. But without honestly really knowing much

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Speaker 1: about it, I'm gonna say no. I know things can

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Speaker 1: kind of happen what seems to be randomly in the universe,

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Speaker 1: and with things the statistical chances that some of the

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Speaker 1: things that do happen, the statistical chances are so low

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Speaker 1: that it just doesn't seem like there could be a

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Speaker 1: cause for every single thing that can happen, because there's

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Speaker 1: so many different things that can happen. So do we

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Speaker 1: need causality? I'm going with no on that one. I

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Speaker 1: think we need causality because if we didn't have cause

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Speaker 1: and effect, everything would just be us because like there

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Speaker 1: would be no reason for anything to happen. Things would

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Speaker 1: stepping on a butterfly would cause something completely crazy to happen,

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Speaker 1: not just like butterfly effect, but like completely bananas. Well,

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Speaker 1: let's I'm thinking of this. You eat, you get fat,

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Speaker 1: cause an effect, and I think we don't need it,

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Speaker 1: and they should be voted out so we don't need it.

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Speaker 1: We can start a petition, I'm sure if we need

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Speaker 1: called out, But I mean, if you want to know

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Speaker 1: the past, cause an effect obviously play a role in

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Speaker 1: knowing what that one part was. But if we didn't happen,

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Speaker 1: if we didn't need it, that would mean possibility is multiverse,

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Speaker 1: and that would be though. I think maybe we don't

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Speaker 1: want No. I don't think we need causality. You can

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Speaker 1: have two things that are correlated, like in you know,

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Speaker 1: economics or statistics. You know, they look for correlations, and

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Speaker 1: correlations provide information in and of themselves. Maybe it's nice

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Speaker 1: to no causality, but I don't think you necessarily need

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Speaker 1: causality to get information, all right, some pretty definitive answers here.

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Speaker 1: Nobody seem to sort of stumble a lot, I know,

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Speaker 1: and some people who really think, like, yeah, we could

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Speaker 1: do without causality. That really surprised me. Really, wow, do

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Speaker 1: you think that's human humors? Maybe physics has just been

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Speaker 1: so successful in like knocking down basic pillars of reality

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Speaker 1: that people are ready for, like physics to undermine everything.

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Speaker 1: You're seeing it as a positive, seeing it as a

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Speaker 1: positive people are open minded to unraveling the basic nature

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Speaker 1: of their very existence. That's great. Well, I think maybe

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Speaker 1: this goes back to what I asked earlier about what

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Speaker 1: exactly do we mean by causality and not having causality?

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Speaker 1: Like does it mean that you can't have a without

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Speaker 1: B or does it mean that you know, as always

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Speaker 1: have to be connected to bees? You know what I mean?

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Speaker 1: Like can things appear out of nowhere without a cause?

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Speaker 1: Or are we saying that it always has to come

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Speaker 1: before B. You cant have be before A, you know

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Speaker 1: what I mean? The difference. Yeah, it's about the ordering

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Speaker 1: of events, right, I mean, you still can't break random

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Speaker 1: laws of physics. You can't just like create energy from nothing.

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Speaker 1: It's not like it's a free for all out there.

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Speaker 1: We think the universe still does have laws and does

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Speaker 1: follow those laws. We're just not sure that those laws

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Speaker 1: require that A always happens before B. So we're pretty

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Speaker 1: clear that you can't just have B without like the

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Speaker 1: pop out of nowhere. Right the laws of physics says no, Yeah,

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Speaker 1: well depends on exactly what B is, right, Like quantum

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Speaker 1: mechanics says, you and have particles pop out of the vacuum.

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Speaker 1: But there are rules for that, right, There are ways

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Speaker 1: that it can happen. So we still think that the

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Speaker 1: universe does follow laws. But hey, maybe when the aliens

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Speaker 1: show up, they're like physics, we gave up on that

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Speaker 1: a million years ago because we discover the universe is

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Speaker 1: totally arbitrary deep down. But yes, we still think that

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Speaker 1: if the universe follows laws, And so you're saying that

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Speaker 1: what we're asking today is whether or not. Those laws

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Speaker 1: sort of prescribe a specific order that things have to

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Speaker 1: happen in the universe. Yeah, but not everything in the

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Speaker 1: universe is connected by causal order. Remember, because there's a

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Speaker 1: finite speed of information, there's some things that you can't

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Speaker 1: have an effect on, right Like events that are happening

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Speaker 1: right now in Andromeda. You can't have any effect on

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Speaker 1: with decisions you make right now, because the information from

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Speaker 1: your decision right now to like send a beam of

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Speaker 1: light or whatever won't affect Andromeda for millions of years.

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Speaker 1: So even with causality, there's some parts of the universe

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Speaker 1: that are not causally connected to other parts. All right, Well,

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Speaker 1: let's maybe break it down for people. What exactly do

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Speaker 1: you mean by causality? How do you define causality or

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Speaker 1: causing effect? Yeah, so take two points in space and time,

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Speaker 1: call them A and B for lack of more creative labels.

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Speaker 1: And here we meet a point in space and in time. Right,

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Speaker 1: So we mean like A is at your house at

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Speaker 1: eight a m. In the morning, and B as you've

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Speaker 1: arrived at work at nine am. So the events have

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Speaker 1: a space and a time in them, all right, And

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Speaker 1: so these two things are causally connected to have a

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Speaker 1: definite order of events if something that happens at B

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Speaker 1: relies on information from A. Right. So maybe, for example,

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Speaker 1: you brought something with you from home to work, so

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Speaker 1: for example, you brought your breakfast or you forgot your

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Speaker 1: breakfast when you left the house. So something you did

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Speaker 1: it A affects what you do. Would be you then

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Speaker 1: need to buy breakfast or steal your coworkers breakfast or something.

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Speaker 1: So those two events are connected causally because something that

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Speaker 1: happens at A influences what happens at B, meaning like

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Speaker 1: if I want to have breakfast at my office, I

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Speaker 1: need to have packed it or left the house with

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Speaker 1: that breakfast otherwise there's no way that I could have

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Speaker 1: that breakfast from home, right exactly. And once you get

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Speaker 1: to work and you have breakfast with you or don't,

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Speaker 1: there's nothing you can do to affect A, right, So

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Speaker 1: this is one directional. A can affect B, but B

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Speaker 1: cannot affect A. So that's what we mean by a

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Speaker 1: definite order of events. If A can have influence on B,

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Speaker 1: then B cannot have influence on A. If your decision

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Speaker 1: to leave the house with or without breakfast affects what

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Speaker 1: you do for breakfast at work, then what you do

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Speaker 1: for breakfast at work cannot affect whether or not you

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Speaker 1: leave the house with your breakfast. It can't go backwards, right.

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Speaker 1: I think you're just saying you can't go back in time.

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Speaker 1: But the two are sort of connected, right, Like if

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Speaker 1: I don't have breakfast in my office, then that means

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Speaker 1: I didn't I didn't leave my home with it. Right.

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Speaker 1: So they're sort of connected, aren't they. But you're saying

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Speaker 1: like one of them affects the other and not the

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Speaker 1: other way around. Yes, exactly. Information flow is only in

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Speaker 1: one direction here and here B is part of the

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Speaker 1: sort of the light cone of a Right. We talked

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Speaker 1: about how decisions you make can only influence things around

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Speaker 1: you that are nearby and in your future, and we

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Speaker 1: talked about in a previous podcast how to formalize that.

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Speaker 1: You think about a light cone, which is all the

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Speaker 1: things in your future that you can influence, and you

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Speaker 1: can influence things that are nearby in your immediate future

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Speaker 1: or things that are far away in the deep future,

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Speaker 1: because it's time for information to get there, all right.

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Speaker 1: So I think you're saying that I didn't leave my

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Speaker 1: house with my breakfast, and therefore I don't have it

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Speaker 1: in my office. That's the cause and that's the effect. Yeah, exactly,

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Speaker 1: And there's no way to go to the opposite direction.

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Speaker 1: What would that even mean? Like I'm at my office

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Speaker 1: first and then I left the house without the breakfast.

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Speaker 1: It would mean that somehow, once you get to your

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Speaker 1: office with or without your breakfast, you could still influence

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Speaker 1: whether you left your house with or without your breakfast.

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Speaker 1: That you could like somehow go back and change what

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Speaker 1: happened at eight am and change a decision based on

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Speaker 1: whether or not you had it with you in your

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Speaker 1: office at nine am. So you know, making a decision

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Speaker 1: at nine am can't influence what happened at eight am.

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Speaker 1: That's all we're saying with cause and effect, all right,

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Speaker 1: So then that's cause and effect and that that seems

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Speaker 1: pretty important for the universe to make sense, right, because

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Speaker 1: otherwise things would be what inconsistent, Like I can always

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Speaker 1: you know, create paradoxes and time loops and things like that.

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Speaker 1: It does seem pretty basic, right. It's the way that

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Speaker 1: we think about physics. When I first got into physics,

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Speaker 1: I thought it was amazing because it could predict the future,

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Speaker 1: and it predicts the future based on the conditions of

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Speaker 1: the present. You know, if you are shooting a cannonball

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Speaker 1: at a castle, you can predict its trajectory if you

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Speaker 1: know it's direction and its velocity, right, those are the causes,

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Speaker 1: and the effect is like, oh, it hits the castle

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Speaker 1: wall or it goes over the castle wall. And so

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Speaker 1: physics seems to me to be like all about using

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Speaker 1: causes to predict effects. You know, that's what the laws

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Speaker 1: of physics are. They take the current description the universe

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Speaker 1: and sort of step it forwards in time to the

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Speaker 1: next description. So it seems pretty basic. All right, Well,

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Speaker 1: it seems basic, which I think is probably a queue

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Speaker 1: that we're going to challenge that and it might turn

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Speaker 1: out to be wrong. So let's get into that and

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Speaker 1: what how we can maybe tested or find out the

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Speaker 1: true answer. But first let's take a quick break. All right,

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Speaker 1: we're talking about cause and effect and whether you actually

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Speaker 1: needed to make a happy universe I guess right, a

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Speaker 1: functioning universe. Yeah, exactly whether we can make sense of

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Speaker 1: our universe without causality, or whether it's actually absolutely fundamentally

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Speaker 1: required for anything to make sense to us. Okay, So

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Speaker 1: then we define causality as like I shoot an arrow

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Speaker 1: and an apple and it hits the apple, but I

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Speaker 1: can't do it the other way around. I like, I

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Speaker 1: can't have hit the apple before shooting the arrow exactly,

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Speaker 1: because if you hit the apple before you shoot the arrow,

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Speaker 1: you could like change your mind and not shoot the arrow,

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Speaker 1: and then oops, you already hit it. How can you

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Speaker 1: change your mind? It seems to like automatically make no sense.

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Speaker 1: It seems like a paradox, as you said, And it

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Speaker 1: seems to be sort of connected to the arrow of time, right,

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Speaker 1: like time only flows one way. But there's a little

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Speaker 1: bit more to it than that, right, there's a little

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Speaker 1: bit more to it than that. And of course the

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Speaker 1: thing that makes things weird and twist your brain and

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Speaker 1: maybe give us an escape from causality is going to

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Speaker 1: end up being quantum mechanics. Of course. Of course, quantum

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Speaker 1: mechanics always scrambling your brain. So that seems that I

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Speaker 1: think I'm guessing it's going to add some sort of

431
00:22:39,840 --> 00:22:43,240
Speaker 1: uncertainty or randomness to causality. Yeah, And before we get

432
00:22:43,240 --> 00:22:45,080
Speaker 1: to quantum mechanics, I think it's important that you have

433
00:22:45,160 --> 00:22:48,080
Speaker 1: in your mind a clear picture of the part of

434
00:22:48,119 --> 00:22:52,239
Speaker 1: the universe that you can affect with your causes. This

435
00:22:52,280 --> 00:22:55,400
Speaker 1: is again this concept of a light cone. Right if

436
00:22:55,440 --> 00:22:58,199
Speaker 1: you send out a flash of light right now, you like,

437
00:22:58,280 --> 00:23:01,040
Speaker 1: turn on a really bright light, then who can tell

438
00:23:01,080 --> 00:23:03,560
Speaker 1: that you have done that? People who are really far

439
00:23:03,640 --> 00:23:06,040
Speaker 1: away from you cannot see that right now. They have

440
00:23:06,080 --> 00:23:08,720
Speaker 1: to wait until the future, and people that are even

441
00:23:08,720 --> 00:23:11,159
Speaker 1: further away have to wait till the deeper future to

442
00:23:11,200 --> 00:23:14,159
Speaker 1: see that flash of light. Because light travels are the

443
00:23:14,240 --> 00:23:18,040
Speaker 1: fastest speed of information, people who haven't seen that flash

444
00:23:18,040 --> 00:23:21,320
Speaker 1: of light can't be influenced by it yet, right, So

445
00:23:21,359 --> 00:23:24,639
Speaker 1: we think about that as a light cone. In two dimensions,

446
00:23:24,640 --> 00:23:26,840
Speaker 1: you can imagine yourself sort of the tip of a

447
00:23:26,920 --> 00:23:30,639
Speaker 1: triangle that's opening up as time goes on, and you

448
00:23:30,680 --> 00:23:33,119
Speaker 1: can influence more and more of the future based on

449
00:23:33,200 --> 00:23:35,960
Speaker 1: your decisions of the present. In three D is sort

450
00:23:36,000 --> 00:23:37,679
Speaker 1: of like you know, you're at the tip of a

451
00:23:37,680 --> 00:23:40,760
Speaker 1: cone right now and it's opening up, right. I guess

452
00:23:40,760 --> 00:23:43,240
Speaker 1: maybe I wonder if we can talk about the breakfast

453
00:23:43,280 --> 00:23:47,080
Speaker 1: cone of my breakfast Okay, when I left my home,

454
00:23:47,480 --> 00:23:49,400
Speaker 1: like you're saying, like, there's this sort of a limited

455
00:23:49,560 --> 00:23:52,840
Speaker 1: number of time and places that I can be at

456
00:23:52,920 --> 00:23:56,760
Speaker 1: with my breakfast if I chose to leave my house

457
00:23:56,800 --> 00:23:59,760
Speaker 1: with my breakfast right, like, I can instantly be at

458
00:23:59,800 --> 00:24:02,480
Speaker 1: my work with breakfast, because I can't get there in time.

459
00:24:03,400 --> 00:24:06,320
Speaker 1: And also I can't be in like China in an

460
00:24:06,320 --> 00:24:09,320
Speaker 1: hour with my breakfast right because I'm limited to by

461
00:24:09,400 --> 00:24:12,360
Speaker 1: how fast I can move exactly. And so if you're

462
00:24:12,359 --> 00:24:14,959
Speaker 1: going to your office pretty close by, then you can

463
00:24:14,960 --> 00:24:17,600
Speaker 1: bring your breakfast with you, and that can influence your coworkers.

464
00:24:17,640 --> 00:24:19,280
Speaker 1: Are they going to try to steal your breakfast? Did

465
00:24:19,320 --> 00:24:21,639
Speaker 1: they forget their own breakfast? Are they influenced by the

466
00:24:21,680 --> 00:24:23,679
Speaker 1: smell of your breakfast? This kind of stuff. But the

467
00:24:23,760 --> 00:24:27,119
Speaker 1: you know, podcast headquarters in Shanghai, for example, can't be

468
00:24:27,160 --> 00:24:30,800
Speaker 1: influenced by that decision until later, until your light cone

469
00:24:30,800 --> 00:24:34,439
Speaker 1: has grown to expand and include all of those things.

470
00:24:34,960 --> 00:24:37,240
Speaker 1: So there are things that you cannot influence right now

471
00:24:37,280 --> 00:24:39,960
Speaker 1: in the universe just because of this finite speed of light,

472
00:24:40,359 --> 00:24:42,760
Speaker 1: and so everything you can influence, we call that part

473
00:24:42,760 --> 00:24:45,560
Speaker 1: of your light cone, right or breakfast cone, which, by

474
00:24:45,560 --> 00:24:48,520
Speaker 1: the way, it sounds like a great breakfast idea for

475
00:24:48,640 --> 00:24:52,120
Speaker 1: McDonald or one of these fast food chains. Breakfast cone

476
00:24:52,119 --> 00:24:54,800
Speaker 1: that sounds like scrambled egg flavored ice cream that does

477
00:24:54,840 --> 00:24:59,879
Speaker 1: not sound, or scrambled eggs on a cone. Scrambled eggs

478
00:25:00,000 --> 00:25:03,160
Speaker 1: on a cone. Actually, that might be a great food truck,

479
00:25:03,160 --> 00:25:04,400
Speaker 1: you know, that's the kind of thing you would see

480
00:25:04,400 --> 00:25:06,600
Speaker 1: in l a with like a huge line of hipsters,

481
00:25:06,640 --> 00:25:12,040
Speaker 1: you know, right, yeah, breakfast cones happen alright, So then

482
00:25:12,080 --> 00:25:14,480
Speaker 1: how do these light cones affect our our sense of

483
00:25:14,520 --> 00:25:17,040
Speaker 1: cause and effect? Well, the interesting thing about light cones

484
00:25:17,200 --> 00:25:20,800
Speaker 1: is that they're pretty simple if the universe is not bent, right,

485
00:25:20,800 --> 00:25:23,280
Speaker 1: if if space is flat, if light moves in straight

486
00:25:23,320 --> 00:25:25,760
Speaker 1: lines like it does out in deep space, then they're

487
00:25:25,800 --> 00:25:27,960
Speaker 1: just like we talked about them their triangles and two

488
00:25:27,960 --> 00:25:30,640
Speaker 1: dimensions or their cones and three D. But they get

489
00:25:30,640 --> 00:25:35,159
Speaker 1: more complicated when space bends. You know that gravity is

490
00:25:35,160 --> 00:25:37,639
Speaker 1: not just a force, it's also a description of the

491
00:25:37,680 --> 00:25:41,560
Speaker 1: way that the universe bends, that space itself bends when

492
00:25:41,560 --> 00:25:44,640
Speaker 1: we are near heavy objects. So the reason, for example,

493
00:25:44,680 --> 00:25:47,040
Speaker 1: the Earth goes around the Sun is not because there's

494
00:25:47,080 --> 00:25:49,840
Speaker 1: a force of gravity pulling on it, but because the

495
00:25:49,880 --> 00:25:52,840
Speaker 1: Sun bends space, and so the Earth is moving in

496
00:25:52,880 --> 00:25:55,520
Speaker 1: a path which is actually quite natural for an object

497
00:25:55,720 --> 00:25:58,840
Speaker 1: under no force. It's moving in a circle. And so

498
00:25:59,080 --> 00:26:02,040
Speaker 1: the same thing how happens to light cones. If you

499
00:26:02,080 --> 00:26:05,000
Speaker 1: are near something massive like a black hole or a

500
00:26:05,000 --> 00:26:08,080
Speaker 1: star or whatever, your light cone bends because the path

501
00:26:08,200 --> 00:26:11,240
Speaker 1: that light takes also bends. So the things you can

502
00:26:11,280 --> 00:26:14,480
Speaker 1: influence change. Now you're making me think of bugles, you know,

503
00:26:14,560 --> 00:26:18,720
Speaker 1: the snack, but the curved cones. I think maybe I

504
00:26:18,720 --> 00:26:21,560
Speaker 1: should have some breakfast before recording these podcasts. But this

505
00:26:21,640 --> 00:26:24,119
Speaker 1: is important for our food truck. We can't have curved

506
00:26:24,119 --> 00:26:26,560
Speaker 1: cones because then the eggs will all fall out, right

507
00:26:26,800 --> 00:26:31,440
Speaker 1: wit what this is why physicists shouldn't be cooked. But anyway,

508
00:26:31,480 --> 00:26:33,520
Speaker 1: it's going back to our topic. You're saying, as you know,

509
00:26:33,600 --> 00:26:36,280
Speaker 1: space can bend, and that can bend or light cones,

510
00:26:36,320 --> 00:26:38,640
Speaker 1: and that can somehow affect causing effect like you can

511
00:26:38,680 --> 00:26:41,520
Speaker 1: break calls in effect by bending space. It doesn't break

512
00:26:41,520 --> 00:26:45,000
Speaker 1: causing effect yet, it just changes what you can affect.

513
00:26:45,080 --> 00:26:47,679
Speaker 1: For example, say you are inside a black hole and

514
00:26:47,760 --> 00:26:51,400
Speaker 1: you make your breakfast. You cannot influence what people eat

515
00:26:51,600 --> 00:26:54,400
Speaker 1: or who gets breakfast outside of the black hole. Right,

516
00:26:54,840 --> 00:26:57,400
Speaker 1: this concept of a light cone inside a black hole,

517
00:26:57,480 --> 00:27:00,280
Speaker 1: it gets twisted. The light cone only points to towards

518
00:27:00,359 --> 00:27:02,560
Speaker 1: the center of the black hole. If you're near a

519
00:27:02,560 --> 00:27:05,160
Speaker 1: black hole, your light colne is distorted. If you send

520
00:27:05,160 --> 00:27:07,119
Speaker 1: out a flash of light or you know, shoot a

521
00:27:07,200 --> 00:27:09,320
Speaker 1: bunch of breakfasts at your friends, they don't all just

522
00:27:09,359 --> 00:27:12,359
Speaker 1: travel in straight paths. And so there are some people

523
00:27:12,359 --> 00:27:16,159
Speaker 1: who are actually near you who you cannot influence because

524
00:27:16,200 --> 00:27:18,960
Speaker 1: of the bending of space. The point is the bending

525
00:27:18,960 --> 00:27:22,480
Speaker 1: of space determines which causes line up with which effects

526
00:27:23,359 --> 00:27:26,040
Speaker 1: I see. So it's not that you're saying cause and

527
00:27:26,080 --> 00:27:29,000
Speaker 1: effect is flexible in a way. Yeah exactly. As you're

528
00:27:29,040 --> 00:27:31,719
Speaker 1: near some heavy mass, then which causes in which effects

529
00:27:31,760 --> 00:27:34,919
Speaker 1: line up depends exactly on the curvature space because it

530
00:27:34,960 --> 00:27:38,040
Speaker 1: depends on how information travels. You know, if you can't

531
00:27:38,080 --> 00:27:40,760
Speaker 1: send a light pulse to somebody, then you can't send

532
00:27:40,800 --> 00:27:45,080
Speaker 1: them information. Then your causes cannot influence their effects. All right,

533
00:27:45,160 --> 00:27:47,320
Speaker 1: So we can limit cause and effect. But I guess

534
00:27:47,320 --> 00:27:49,080
Speaker 1: the question is can we break it or do we

535
00:27:49,119 --> 00:27:51,439
Speaker 1: need it? And you're saying that things start to get

536
00:27:51,480 --> 00:27:54,680
Speaker 1: weird when you add quantum mechanics, Yeah, exactly. So now

537
00:27:54,760 --> 00:27:57,560
Speaker 1: we've done special relativity with light cones, we went to

538
00:27:57,680 --> 00:28:01,760
Speaker 1: general relativity by bending those light cones through space. Now

539
00:28:01,840 --> 00:28:04,320
Speaker 1: we're going to add in the final ingredient, which is

540
00:28:04,400 --> 00:28:07,480
Speaker 1: quantum mechanics. Right, say we're near this black hole, so

541
00:28:07,520 --> 00:28:09,680
Speaker 1: a light cone is all twisted and bent, and who

542
00:28:09,680 --> 00:28:13,119
Speaker 1: we can influence and talk about breakfast with depends on

543
00:28:13,200 --> 00:28:15,800
Speaker 1: the curvature of space. But what if the curvature of

544
00:28:15,800 --> 00:28:19,800
Speaker 1: space itself was uncertain? Like what if we didn't know

545
00:28:19,920 --> 00:28:23,280
Speaker 1: exactly where that black hole was because it was like

546
00:28:23,600 --> 00:28:26,960
Speaker 1: created from some quantum process, So I had a probability

547
00:28:26,960 --> 00:28:29,920
Speaker 1: to be here and a probability be over there, then

548
00:28:29,920 --> 00:28:33,600
Speaker 1: we would have like two possible light cones, which would

549
00:28:33,600 --> 00:28:36,520
Speaker 1: mean like two possible portions of the universe that we

550
00:28:36,560 --> 00:28:38,960
Speaker 1: could influence. But I wonder, do you actually need the

551
00:28:39,000 --> 00:28:41,360
Speaker 1: black hole to get those two possible light cones? Like,

552
00:28:41,600 --> 00:28:45,440
Speaker 1: you know, isn't there quantum uncertainty in everything? Right? Like

553
00:28:45,600 --> 00:28:48,120
Speaker 1: if I leave my house, there's maybe a fifty percent

554
00:28:48,160 --> 00:28:50,400
Speaker 1: chance that I took a rite in a fifty percent

555
00:28:50,440 --> 00:28:52,640
Speaker 1: chance I took at left, And so there's two possible

556
00:28:52,680 --> 00:28:56,560
Speaker 1: breakfast cones, two possible breakfast cones. Yes, the black hole

557
00:28:56,640 --> 00:28:59,160
Speaker 1: is just the extreme example because it's easy to think

558
00:28:59,200 --> 00:29:01,920
Speaker 1: about how the black hole changes the shape of your

559
00:29:02,000 --> 00:29:05,640
Speaker 1: light cone is very dramatic. But every time this quantum uncertainty,

560
00:29:05,840 --> 00:29:09,400
Speaker 1: and that uncertainty leads to uncertainty and where stuff is

561
00:29:09,520 --> 00:29:12,840
Speaker 1: in the universe. That means this uncertainty about the curvature

562
00:29:12,880 --> 00:29:17,080
Speaker 1: of space, which means this uncertainty about the causality. Right,

563
00:29:17,120 --> 00:29:18,840
Speaker 1: if I don't know where the black hole is or

564
00:29:18,840 --> 00:29:22,160
Speaker 1: where Jorhees Breakfast went, that I can't necessarily predict which

565
00:29:22,240 --> 00:29:25,920
Speaker 1: part of the universe I can influence. Okay, so then, um,

566
00:29:25,960 --> 00:29:29,920
Speaker 1: there's some uncertainty in the light cones and two possible futures.

567
00:29:30,040 --> 00:29:32,400
Speaker 1: So then how does that break causality? Well, you can

568
00:29:32,440 --> 00:29:35,320
Speaker 1: imagine some experiments, right, Like let's say, for example, we

569
00:29:35,400 --> 00:29:39,480
Speaker 1: have two people doing experiments, and in quantum mechanics thought experiments,

570
00:29:39,480 --> 00:29:42,719
Speaker 1: people always use Alice and Bob because there you know

571
00:29:42,800 --> 00:29:44,800
Speaker 1: A and b. Maybe we can mix it up a

572
00:29:44,840 --> 00:29:47,160
Speaker 1: little bit, you can think of more clever names. But

573
00:29:47,240 --> 00:29:50,280
Speaker 1: we have two people doing experiments somewhere out in space,

574
00:29:50,440 --> 00:29:53,440
Speaker 1: and their experiments depend, for example, on how close they

575
00:29:53,440 --> 00:29:56,160
Speaker 1: are to the Earth, right, because the Earth is going

576
00:29:56,240 --> 00:29:59,000
Speaker 1: to bend space and you know that for example, if

577
00:29:59,040 --> 00:30:02,280
Speaker 1: you are near the Earth, then your time slows down

578
00:30:02,440 --> 00:30:06,800
Speaker 1: because gravitational time dilation makes clocks run slower like Clocks

579
00:30:06,840 --> 00:30:09,400
Speaker 1: closer to the Earth run more slowly than clocks further

580
00:30:09,480 --> 00:30:12,680
Speaker 1: from the Earth. So now we have these two experimenters.

581
00:30:12,680 --> 00:30:15,560
Speaker 1: They're out in space. One of them is closer to

582
00:30:15,600 --> 00:30:18,000
Speaker 1: the Earth than the other one, right, but if the

583
00:30:18,040 --> 00:30:21,160
Speaker 1: Earth's location is uncertain, we don't know which one it is.

584
00:30:21,480 --> 00:30:24,280
Speaker 1: So now one of them has had their time slowed

585
00:30:24,280 --> 00:30:26,479
Speaker 1: down more than the other one. So one of them

586
00:30:26,560 --> 00:30:30,680
Speaker 1: can influence the other because their time has been slowed down. So,

587
00:30:30,720 --> 00:30:33,400
Speaker 1: for example, if Alice has had her time slowed more,

588
00:30:33,720 --> 00:30:36,240
Speaker 1: then she hasn't gotten as far in her experiment, and

589
00:30:36,320 --> 00:30:39,560
Speaker 1: Bob can send her a message influencing her experiment. But

590
00:30:39,640 --> 00:30:42,320
Speaker 1: if Bob has had his time slowed down more, then

591
00:30:42,360 --> 00:30:46,040
Speaker 1: Alice can influence his experiment. So we don't know necessarily

592
00:30:46,440 --> 00:30:49,560
Speaker 1: which way causality goes from Alice to Bob or from

593
00:30:49,640 --> 00:30:53,200
Speaker 1: Bob to Alice, because we don't know where Earth is,

594
00:30:53,320 --> 00:30:57,160
Speaker 1: and that determines where these light cones flow. Okay, well, um,

595
00:30:57,200 --> 00:30:59,440
Speaker 1: first of all, I'm a little worried we can't find Earth.

596
00:31:00,120 --> 00:31:03,080
Speaker 1: It's a little concerning. I think you're saying, like the

597
00:31:03,120 --> 00:31:05,560
Speaker 1: Alice and Bob are doing the same experiment right, Like

598
00:31:05,600 --> 00:31:07,840
Speaker 1: you're trying to figure out whats inside of a box

599
00:31:08,080 --> 00:31:10,560
Speaker 1: and they have maybe the same box, and you're saying

600
00:31:10,600 --> 00:31:12,479
Speaker 1: that if one of them is moving at a different

601
00:31:12,480 --> 00:31:15,560
Speaker 1: time rate than like, if one of them has time

602
00:31:15,600 --> 00:31:18,040
Speaker 1: moving faster for them, they could finish the experiment and

603
00:31:18,080 --> 00:31:20,600
Speaker 1: then run over until the other one what's in the

604
00:31:20,640 --> 00:31:23,920
Speaker 1: box exactly? Or maybe they're like trying to unlock somebody's

605
00:31:23,920 --> 00:31:26,520
Speaker 1: phone and they're trying to guess codes or something. And

606
00:31:26,560 --> 00:31:30,600
Speaker 1: if Alice's time runs more slowly, then Bob can try

607
00:31:30,600 --> 00:31:32,480
Speaker 1: a bunch of codes, and if he finds one, he

608
00:31:32,480 --> 00:31:34,960
Speaker 1: can send Alice a message saying, oh, try this one,

609
00:31:35,040 --> 00:31:37,400
Speaker 1: or don't try these, I already try them. That's if

610
00:31:37,440 --> 00:31:40,920
Speaker 1: Alice's time is running more slowly. If it's the opposite,

611
00:31:41,000 --> 00:31:43,680
Speaker 1: like the Earth happens to be in another situation where

612
00:31:43,680 --> 00:31:46,720
Speaker 1: it slows down Bob's time, then Alice can finish her

613
00:31:46,720 --> 00:31:50,200
Speaker 1: experiment first. So who finishes the experiment first and who

614
00:31:50,200 --> 00:31:52,240
Speaker 1: can send a message to the other one about their

615
00:31:52,280 --> 00:31:56,400
Speaker 1: results depends on who is closer to the gravitational object

616
00:31:56,480 --> 00:31:59,160
Speaker 1: that's slowing down time. And you know it sounds weird

617
00:31:59,240 --> 00:32:00,680
Speaker 1: to say, like, well, how do we not know where

618
00:32:00,680 --> 00:32:03,320
Speaker 1: the Earth is? It's a crazy thought experiment where we've

619
00:32:03,400 --> 00:32:05,800
Speaker 1: like put the Earth in some sort of crazy quantum

620
00:32:05,800 --> 00:32:08,560
Speaker 1: mechanical superpositions, so we don't know where it is. That's

621
00:32:08,600 --> 00:32:10,560
Speaker 1: pretty hard to imagine. But this is what we do

622
00:32:10,560 --> 00:32:13,200
Speaker 1: when we try to understand like the extremes of the universe.

623
00:32:13,240 --> 00:32:16,600
Speaker 1: We come up with these crazy experiments to understand whether

624
00:32:16,640 --> 00:32:19,479
Speaker 1: the rules are broken in extreme situations. I wonder if

625
00:32:19,480 --> 00:32:23,000
Speaker 1: you can simplify by just talking about like short Dinger's box, right,

626
00:32:23,040 --> 00:32:25,080
Speaker 1: Like you're saying, let's put the Earth, Alice and Bob

627
00:32:25,120 --> 00:32:27,400
Speaker 1: inside of a box, and we sort of don't know

628
00:32:27,400 --> 00:32:30,400
Speaker 1: where the Earth is, and so from us sitting outside

629
00:32:30,400 --> 00:32:33,240
Speaker 1: of the box, we don't know who told who about

630
00:32:33,240 --> 00:32:37,360
Speaker 1: the results of their experiment. It sounds like Shortingers prisoners dilemma,

631
00:32:38,160 --> 00:32:43,000
Speaker 1: sounds catastrophic exactly. So we don't know then what has

632
00:32:43,040 --> 00:32:45,760
Speaker 1: happened inside the box. Was it Alice and then Bob,

633
00:32:46,040 --> 00:32:48,880
Speaker 1: or was it Bob and then Alice? And so in

634
00:32:48,920 --> 00:32:53,240
Speaker 1: this situation, because the position of the light cones is uncertain,

635
00:32:53,600 --> 00:32:57,440
Speaker 1: causality is uncertain, and so in this kind of experiment,

636
00:32:57,480 --> 00:32:59,840
Speaker 1: it's like, well, which happened Was it A before B

637
00:33:00,160 --> 00:33:03,880
Speaker 1: or B before A. So now causality has become uncertain.

638
00:33:04,120 --> 00:33:07,280
Speaker 1: Remember the very beginning, we define causality saying, well, if

639
00:33:07,320 --> 00:33:10,440
Speaker 1: A can influence B, you know A causees B. That

640
00:33:10,440 --> 00:33:13,440
Speaker 1: that means it's impossible for B to cause A. So

641
00:33:13,480 --> 00:33:16,160
Speaker 1: in this experiment, like we have two events and we

642
00:33:16,280 --> 00:33:19,440
Speaker 1: can't say which one happened first, and they do influence

643
00:33:19,480 --> 00:33:21,840
Speaker 1: each other. One is definitely inside the light cone of

644
00:33:21,880 --> 00:33:24,760
Speaker 1: the other. We just don't know which, right, And and

645
00:33:24,840 --> 00:33:27,800
Speaker 1: that's just sort of isn't that sort of regular quantum mechanics,

646
00:33:27,840 --> 00:33:30,040
Speaker 1: Like we don't really know whether the cat is alive

647
00:33:30,120 --> 00:33:32,440
Speaker 1: or dead anyways, right, that's right, we don't know quantum

648
00:33:32,440 --> 00:33:34,440
Speaker 1: mechanics whether the cat is are live or dead. But

649
00:33:34,520 --> 00:33:38,240
Speaker 1: we've added in another element here, which is causality, because

650
00:33:38,280 --> 00:33:41,640
Speaker 1: now quantum mechanics is influencing the very shape of space,

651
00:33:41,880 --> 00:33:45,440
Speaker 1: which determines which events can happen in what order. In

652
00:33:45,440 --> 00:33:49,520
Speaker 1: this classical shortingers box example, you know, the causality is clear,

653
00:33:49,920 --> 00:33:52,920
Speaker 1: like you know, the radioactive element decays and either kills

654
00:33:52,960 --> 00:33:55,440
Speaker 1: the cat or it does not. The order of events

655
00:33:55,560 --> 00:33:58,719
Speaker 1: is clear, even though which events happens is not right,

656
00:33:58,760 --> 00:34:01,200
Speaker 1: it's not like the cat can scape and then rebuild

657
00:34:01,200 --> 00:34:04,600
Speaker 1: the box or something. You can't have anything going backwards

658
00:34:04,600 --> 00:34:07,360
Speaker 1: in that experiment. Here, we might have things happening in

659
00:34:07,400 --> 00:34:10,760
Speaker 1: an indefinite order because we've made the shape of space

660
00:34:10,840 --> 00:34:14,360
Speaker 1: itself uncertain, and it's that shape of space that determines

661
00:34:14,680 --> 00:34:17,719
Speaker 1: what can influence what because it controls the shape of

662
00:34:17,719 --> 00:34:20,640
Speaker 1: the light cone. All right, So then the causality of

663
00:34:20,640 --> 00:34:23,800
Speaker 1: what happened inside the box is uncertain. There's a quantum

664
00:34:23,880 --> 00:34:27,359
Speaker 1: uncertainty about it. But does that really mean that causality

665
00:34:27,880 --> 00:34:31,279
Speaker 1: broke or it's it's not needed or it's false, do

666
00:34:31,320 --> 00:34:33,040
Speaker 1: you know what I mean? Like, it's just it's just

667
00:34:33,080 --> 00:34:35,520
Speaker 1: that we don't know, right, How does that sort of

668
00:34:35,560 --> 00:34:38,200
Speaker 1: break things about the universe. Yeah, well, it means that

669
00:34:38,239 --> 00:34:41,280
Speaker 1: maybe causality is not always needed. You know, it seems

670
00:34:41,320 --> 00:34:43,400
Speaker 1: like it's the kind of thing that happens a lot

671
00:34:43,840 --> 00:34:46,520
Speaker 1: most of the time. In most circumstances, you don't get

672
00:34:47,000 --> 00:34:51,400
Speaker 1: huge uncertain bending of space that makes causality uncertain. So

673
00:34:51,480 --> 00:34:54,759
Speaker 1: causality is probably like a very effective principle. But you know,

674
00:34:54,840 --> 00:34:57,320
Speaker 1: we want to understand the deep nature of the universe,

675
00:34:57,400 --> 00:35:00,160
Speaker 1: not just like hey, this mostly works. Let's move on.

676
00:35:00,600 --> 00:35:03,400
Speaker 1: We want to understand how things actually work. And right

677
00:35:03,440 --> 00:35:06,799
Speaker 1: now we have these two really key ideas about the

678
00:35:06,800 --> 00:35:09,480
Speaker 1: way the universe works, quantum mechanics, which tells us things

679
00:35:09,520 --> 00:35:13,399
Speaker 1: are fundamentally uncertain, and general relativity, which tells us how

680
00:35:13,480 --> 00:35:16,960
Speaker 1: space bends around mass. And we'd like to emerge those two.

681
00:35:17,000 --> 00:35:19,040
Speaker 1: We would like to have a theory of quantum gravity

682
00:35:19,080 --> 00:35:21,680
Speaker 1: that tells us, you know, how quantum mechanics and gravity

683
00:35:21,680 --> 00:35:24,520
Speaker 1: play well together. Well, this suggests that, you know, we

684
00:35:24,640 --> 00:35:27,200
Speaker 1: might have to give up causality if we want to

685
00:35:27,200 --> 00:35:29,360
Speaker 1: emerge them. That if we want to bring quantum mechanics

686
00:35:29,400 --> 00:35:32,719
Speaker 1: and general relativity together, then these two concepts might not

687
00:35:32,800 --> 00:35:35,279
Speaker 1: play well together. You know, they seem to create these

688
00:35:35,320 --> 00:35:38,759
Speaker 1: situations with uncertain causality. And so maybe the key to

689
00:35:39,280 --> 00:35:41,640
Speaker 1: finding a theory of quantum gravity and revealing the deep

690
00:35:41,719 --> 00:35:44,719
Speaker 1: nature of the universe is to give up on causality.

691
00:35:44,760 --> 00:35:48,120
Speaker 1: To say, it happens a lot, it's convenient, it's nice,

692
00:35:48,280 --> 00:35:51,319
Speaker 1: but it's not actually always required. I guess maybe it's

693
00:35:51,360 --> 00:35:53,400
Speaker 1: hard to see sort of the stakes here with Bob

694
00:35:53,400 --> 00:35:56,319
Speaker 1: and ell is because you know, like whether one of

695
00:35:56,320 --> 00:36:00,480
Speaker 1: them tells the other first or the second, maybe it doesn't,

696
00:36:00,560 --> 00:36:02,920
Speaker 1: you know, sort of affect my reality that much. But

697
00:36:03,080 --> 00:36:04,880
Speaker 1: can you think of an example of where like this

698
00:36:05,000 --> 00:36:09,279
Speaker 1: uncertainty in causality would sort of have more, I don't know,

699
00:36:09,520 --> 00:36:12,120
Speaker 1: sort of like deeper repercussions. You know. I think that

700
00:36:12,200 --> 00:36:15,040
Speaker 1: physicists are still struggling to get their minds around the

701
00:36:15,200 --> 00:36:18,000
Speaker 1: consequences here. And we'll talk in a minute about like

702
00:36:18,080 --> 00:36:20,879
Speaker 1: experiments people are doing to try to use this. We're

703
00:36:20,920 --> 00:36:25,520
Speaker 1: developing ideas for like how to improve computation or you know,

704
00:36:25,719 --> 00:36:30,440
Speaker 1: make information transmission actually more efficient, or change the very

705
00:36:30,520 --> 00:36:33,440
Speaker 1: nature of thermodynamics. But it's something that's so basic and

706
00:36:33,480 --> 00:36:36,400
Speaker 1: fundamental to our thinking that we're having trouble even like

707
00:36:36,560 --> 00:36:40,080
Speaker 1: contemplating what physics would look like without causality, and so

708
00:36:40,160 --> 00:36:42,320
Speaker 1: it's hard to get your mind around like how that

709
00:36:42,360 --> 00:36:45,040
Speaker 1: would actually influence the universe. All right, Well, I think

710
00:36:45,040 --> 00:36:47,640
Speaker 1: basically what you're saying though, is that you know, there

711
00:36:47,640 --> 00:36:52,520
Speaker 1: are situations where quantum mechanics can throw uncertainty about the

712
00:36:53,160 --> 00:36:55,600
Speaker 1: order of things, right, Like there can be situations where

713
00:36:55,640 --> 00:36:57,480
Speaker 1: we don't know if A came before B or B

714
00:36:57,640 --> 00:37:01,040
Speaker 1: came before A. And so because there our situations where

715
00:37:01,440 --> 00:37:04,320
Speaker 1: we don't know. Maybe the question is do we actually

716
00:37:04,320 --> 00:37:06,440
Speaker 1: need it? Right? That's I think that's what you're getting at.

717
00:37:06,480 --> 00:37:09,279
Speaker 1: It's like, maybe since it's not something that has to

718
00:37:09,520 --> 00:37:11,680
Speaker 1: be known, maybe it's something we don't even need in

719
00:37:11,719 --> 00:37:14,960
Speaker 1: the universe. Yeah, and maybe it's not something the universe demands,

720
00:37:15,400 --> 00:37:18,000
Speaker 1: you know, the same way when you have quantum entanglement.

721
00:37:18,239 --> 00:37:21,319
Speaker 1: You might have like two particles that are far away

722
00:37:21,360 --> 00:37:24,600
Speaker 1: in uncertain states about you know, what direction their spin is,

723
00:37:25,080 --> 00:37:27,000
Speaker 1: and we like to think, oh man, but there has

724
00:37:27,040 --> 00:37:28,959
Speaker 1: to be a real truth there. It has to either

725
00:37:29,000 --> 00:37:31,239
Speaker 1: be this or that. You know, there has to be

726
00:37:31,280 --> 00:37:34,200
Speaker 1: some deep hidden knowledge. And we discovered actually the universe

727
00:37:34,239 --> 00:37:36,920
Speaker 1: doesn't care the universes happen to have that be uncertain,

728
00:37:37,160 --> 00:37:40,239
Speaker 1: the true nature of these particles. And now we're taking

729
00:37:40,239 --> 00:37:42,400
Speaker 1: that a step further and saying, look, maybe the universe

730
00:37:42,440 --> 00:37:45,560
Speaker 1: doesn't really care always whether A happen before B or

731
00:37:45,600 --> 00:37:48,200
Speaker 1: B happened before A. Maybe it's happy to have that

732
00:37:48,280 --> 00:37:51,560
Speaker 1: be uncertain, for it to be undetermined, which is pretty

733
00:37:51,600 --> 00:37:54,040
Speaker 1: hard for us to consider. All Right, Well, maybe we

734
00:37:54,080 --> 00:37:57,000
Speaker 1: don't need causality, but we definitely need to pay for

735
00:37:57,040 --> 00:38:00,279
Speaker 1: this podcast. So that's the one cost and of we

736
00:38:00,320 --> 00:38:03,640
Speaker 1: can't ignore. So let's talk about how you might test

737
00:38:03,680 --> 00:38:06,200
Speaker 1: whether or not this theory is right, or whether or

738
00:38:06,200 --> 00:38:09,080
Speaker 1: not you actually do need castality in the universe. But

739
00:38:09,160 --> 00:38:24,200
Speaker 1: first let's take a quick break. All right, So, Daniel,

740
00:38:24,239 --> 00:38:27,000
Speaker 1: apparently maybe the universe doesn't need causality, you know, or

741
00:38:27,080 --> 00:38:28,719
Speaker 1: maybe I think what you're saying is that maybe the

742
00:38:28,800 --> 00:38:31,880
Speaker 1: universe doesn't really care that much about castality, Like it

743
00:38:31,920 --> 00:38:35,799
Speaker 1: could go either way. Exactly. It's like effect before cause,

744
00:38:35,880 --> 00:38:38,080
Speaker 1: caused before effect, whatever. As long as I got my

745
00:38:38,120 --> 00:38:41,560
Speaker 1: breakfast cone, I'm fine, you know, whatever, as long as

746
00:38:41,600 --> 00:38:45,000
Speaker 1: I got taken in my scrambled cone. Yeah, and again,

747
00:38:45,080 --> 00:38:48,439
Speaker 1: let me just reiterate. This doesn't mean that anything goes

748
00:38:48,760 --> 00:38:51,200
Speaker 1: that you should just like go out there and steal

749
00:38:51,280 --> 00:38:54,359
Speaker 1: jewelry and whatever. There are no consequences for your actions, right,

750
00:38:54,360 --> 00:38:56,600
Speaker 1: You're still going to prison if you steal money from

751
00:38:56,640 --> 00:38:59,400
Speaker 1: your local grocery store. It just means that sometimes in

752
00:38:59,440 --> 00:39:02,440
Speaker 1: scenarios are there are two possible orders for events, the

753
00:39:02,520 --> 00:39:06,040
Speaker 1: universe might not pick between them, right. Yeah, it might

754
00:39:06,239 --> 00:39:11,480
Speaker 1: leave things undecided and go about its happy way. Yeah, exactly.

755
00:39:11,640 --> 00:39:15,600
Speaker 1: Physicists called this indefinite causality, so not like a complete

756
00:39:15,640 --> 00:39:19,080
Speaker 1: overthrow of causality, but like an important weakening, you know,

757
00:39:19,160 --> 00:39:21,440
Speaker 1: to say like, oh, these are cracking causality. There are

758
00:39:21,440 --> 00:39:25,000
Speaker 1: cases when you don't have to know what happens first.

759
00:39:25,120 --> 00:39:29,880
Speaker 1: What if you just call it causality is diet causality?

760
00:39:30,239 --> 00:39:33,080
Speaker 1: There you go, all right, so that's a possibility. And

761
00:39:33,120 --> 00:39:35,520
Speaker 1: it seems like the universe, you know, it's kind of

762
00:39:35,520 --> 00:39:38,319
Speaker 1: fuzzy about causality, And so are there experiments to sort

763
00:39:38,320 --> 00:39:40,200
Speaker 1: of test this or to figure out what the right

764
00:39:40,239 --> 00:39:43,839
Speaker 1: answer is in physics, Yeah, there are some really cool experiments.

765
00:39:44,120 --> 00:39:46,800
Speaker 1: People came up with these ideas in the two thousands

766
00:39:46,840 --> 00:39:48,640
Speaker 1: and sort of playing with them. Is as they were

767
00:39:48,680 --> 00:39:52,080
Speaker 1: trying to stitch together quantum mechanics and general relativity to

768
00:39:52,120 --> 00:39:55,080
Speaker 1: think about quantum gravity, and realized maybe this is the

769
00:39:55,120 --> 00:39:57,480
Speaker 1: stumbling block, Maybe this is the piece we need to

770
00:39:57,480 --> 00:40:00,320
Speaker 1: get rid of so that everything else clicks together nicely,

771
00:40:00,880 --> 00:40:03,239
Speaker 1: And so they tried to make some experiments. Then you know,

772
00:40:03,280 --> 00:40:06,080
Speaker 1: it's hard to have black holes or to put the

773
00:40:06,120 --> 00:40:08,759
Speaker 1: Earth in a quantum superposition, so they came up with

774
00:40:08,800 --> 00:40:11,239
Speaker 1: a totally different set of experiments. And it's mostly folks

775
00:40:11,280 --> 00:40:14,239
Speaker 1: who are working on things like quantum information. Whether you know,

776
00:40:14,280 --> 00:40:18,000
Speaker 1: they are like splitting photon beams and polarizing them and

777
00:40:18,040 --> 00:40:20,440
Speaker 1: capturing the information in them and not in them, and

778
00:40:20,480 --> 00:40:22,480
Speaker 1: this kind of stuff. They were able to do experiments

779
00:40:22,480 --> 00:40:25,359
Speaker 1: that probe this kind of thing. All right, So then

780
00:40:25,440 --> 00:40:27,759
Speaker 1: how does the experiment work? What's going on? Yeah, So

781
00:40:27,800 --> 00:40:29,880
Speaker 1: what you do is you take a beam of photons.

782
00:40:29,920 --> 00:40:32,480
Speaker 1: These are just you know, like it's a laser beam essentially,

783
00:40:32,560 --> 00:40:34,839
Speaker 1: and you have these particles flying out and then you

784
00:40:34,880 --> 00:40:37,320
Speaker 1: split them use this one of these beams splitters, so

785
00:40:37,400 --> 00:40:39,440
Speaker 1: like half the photons go one way and half the

786
00:40:39,440 --> 00:40:42,200
Speaker 1: photons go the other way. And then you send the

787
00:40:42,239 --> 00:40:46,239
Speaker 1: photons through two different paths. Along one path you do

788
00:40:46,360 --> 00:40:48,919
Speaker 1: A to the photons and then B. And then along

789
00:40:48,960 --> 00:40:50,920
Speaker 1: the other path you do B. And then you do A.

790
00:40:51,480 --> 00:40:53,080
Speaker 1: What does that mean to do A or do B.

791
00:40:53,480 --> 00:40:56,280
Speaker 1: It's like you perform some operation you change the photons

792
00:40:56,320 --> 00:40:58,719
Speaker 1: a little bit. In this case, what they did is

793
00:40:58,760 --> 00:41:01,839
Speaker 1: they polarize the photo potons. Photons are more than just

794
00:41:01,920 --> 00:41:04,600
Speaker 1: like packs of light. They have like little spins to them.

795
00:41:04,880 --> 00:41:07,839
Speaker 1: You can change the way those spins are pointed, and

796
00:41:07,920 --> 00:41:10,600
Speaker 1: so along one path they like flip the spins one

797
00:41:10,640 --> 00:41:12,960
Speaker 1: way and then another way. Along the other path. They

798
00:41:12,960 --> 00:41:15,120
Speaker 1: do it in the opposite order, right, they sort of

799
00:41:15,200 --> 00:41:17,400
Speaker 1: run it through some filters, right, yeah, exactly. You can

800
00:41:17,440 --> 00:41:19,280
Speaker 1: think about it like that, running it through some filters.

801
00:41:19,480 --> 00:41:22,520
Speaker 1: And the key thing is that the order matters, Like

802
00:41:22,600 --> 00:41:25,279
Speaker 1: the photons look different if you do A and then

803
00:41:25,320 --> 00:41:28,440
Speaker 1: B versus B and then A, and you know this

804
00:41:28,560 --> 00:41:31,719
Speaker 1: could happen because sometimes these are things are conceptually the

805
00:41:31,760 --> 00:41:34,799
Speaker 1: same as like rotations, where you know it matters what

806
00:41:34,960 --> 00:41:37,480
Speaker 1: order you do them. It's like if you turn around

807
00:41:37,640 --> 00:41:39,440
Speaker 1: and then you turn left, it's different than if you

808
00:41:39,480 --> 00:41:41,719
Speaker 1: turn left and then turn around. All right, So then

809
00:41:41,760 --> 00:41:44,080
Speaker 1: I have a laser beam. I split it and in

810
00:41:44,280 --> 00:41:46,520
Speaker 1: one half of it I do A and B and

811
00:41:46,600 --> 00:41:48,920
Speaker 1: the other side I do B and then A, And

812
00:41:48,960 --> 00:41:51,799
Speaker 1: then what I compare them to see if they if

813
00:41:51,800 --> 00:41:54,759
Speaker 1: something different happen, And then you bring them back together, right,

814
00:41:55,040 --> 00:41:57,560
Speaker 1: you rejoin them, and now you have photons and you

815
00:41:57,600 --> 00:41:59,840
Speaker 1: don't know which path they took. Do they do the

816
00:42:00,000 --> 00:42:02,719
Speaker 1: A B path or the B A path? And what

817
00:42:02,880 --> 00:42:05,440
Speaker 1: you see when it comes out is a really interesting

818
00:42:05,480 --> 00:42:09,279
Speaker 1: interference pattern between photons that went through A B and

819
00:42:09,320 --> 00:42:11,680
Speaker 1: then photons that went through B A And just like

820
00:42:11,719 --> 00:42:14,759
Speaker 1: in sort of the double slit experiment where particles could

821
00:42:14,760 --> 00:42:16,920
Speaker 1: have gone through one slit or the other, and the

822
00:42:16,960 --> 00:42:19,920
Speaker 1: probability to have gone through one or the other interferes

823
00:42:20,120 --> 00:42:23,279
Speaker 1: with the first ones. Then you get these interference patterns.

824
00:42:23,280 --> 00:42:25,920
Speaker 1: So this interference patterns means that you really do have

825
00:42:25,960 --> 00:42:29,239
Speaker 1: photons from both in your beam, and that for any

826
00:42:29,280 --> 00:42:31,360
Speaker 1: given photon, you don't know whether it went through A

827
00:42:31,480 --> 00:42:33,920
Speaker 1: B or whether it went through B A. So what

828
00:42:33,960 --> 00:42:38,040
Speaker 1: you're seeing is this interference pattern between the probabilities, which

829
00:42:38,040 --> 00:42:41,959
Speaker 1: means that both possibilities exist for any given photon. Each

830
00:42:41,960 --> 00:42:44,680
Speaker 1: photon has a possibility to have gone through one side

831
00:42:44,840 --> 00:42:47,080
Speaker 1: or the other. Oh, I see, it's like you take

832
00:42:47,120 --> 00:42:49,319
Speaker 1: those two beams and then you join them again, and

833
00:42:49,320 --> 00:42:51,920
Speaker 1: then you look the photons that come out, and when

834
00:42:51,920 --> 00:42:54,080
Speaker 1: you get a photon out of that joint beam, you

835
00:42:54,120 --> 00:42:56,920
Speaker 1: don't know whether it went through A B or B A,

836
00:42:57,920 --> 00:43:00,399
Speaker 1: but it's sort of it looks like it went through

837
00:43:00,440 --> 00:43:02,600
Speaker 1: both at the same time, sort of like the cat

838
00:43:02,840 --> 00:43:06,520
Speaker 1: alive and death exactly. And so here these photons have

839
00:43:06,680 --> 00:43:10,799
Speaker 1: had an experience that has indefinite causality. Right, we don't

840
00:43:10,840 --> 00:43:13,960
Speaker 1: know what the order of events was for these photons,

841
00:43:14,000 --> 00:43:17,200
Speaker 1: and it matters, right, A B has different photons than

842
00:43:17,360 --> 00:43:21,160
Speaker 1: BE at an individual photon, there's a probability of one

843
00:43:21,400 --> 00:43:24,239
Speaker 1: or probability of the other, and that leads to this

844
00:43:24,520 --> 00:43:27,040
Speaker 1: really interesting interference pattern. So you can see that this

845
00:43:27,120 --> 00:43:29,640
Speaker 1: is actually happening. It's not like you have just two

846
00:43:29,719 --> 00:43:32,040
Speaker 1: different groups of photons, ones that are A B and

847
00:43:32,080 --> 00:43:34,960
Speaker 1: ones that are B A. Every photon now has a

848
00:43:34,960 --> 00:43:38,160
Speaker 1: probability of having one order or the other. Right, But

849
00:43:38,239 --> 00:43:41,040
Speaker 1: I guess you know it's looking at this skeptically. It's

850
00:43:41,040 --> 00:43:42,920
Speaker 1: not like you did the same thing A and B

851
00:43:43,080 --> 00:43:46,120
Speaker 1: in different orders, but they went through different filters kind

852
00:43:46,120 --> 00:43:49,160
Speaker 1: of right, They took a different path through space. So

853
00:43:49,160 --> 00:43:51,960
Speaker 1: it's sort of not like I'm not really changing the

854
00:43:52,080 --> 00:43:54,400
Speaker 1: order of events. I'm changing the path, that's right. But

855
00:43:54,440 --> 00:43:56,880
Speaker 1: in this case, the path determines the order of events.

856
00:43:56,960 --> 00:43:59,080
Speaker 1: And you're right, it's not exactly analogous to what we're

857
00:43:59,080 --> 00:44:02,320
Speaker 1: talking about before with light cones and the bending of space.

858
00:44:02,600 --> 00:44:05,640
Speaker 1: It's a different way to try to construct indefinite causality,

859
00:44:05,960 --> 00:44:09,759
Speaker 1: right there, not exactly physically the same filters, right, it's

860
00:44:09,760 --> 00:44:12,279
Speaker 1: sort of like a standing for having done the same

861
00:44:12,320 --> 00:44:15,319
Speaker 1: thing in a different order. Yes, exactly, because you can't

862
00:44:15,360 --> 00:44:17,799
Speaker 1: do that. You can't like reverse time and do the

863
00:44:17,840 --> 00:44:20,719
Speaker 1: experiment again in the other order and then rejoin it.

864
00:44:20,760 --> 00:44:22,440
Speaker 1: That would be super awesome if you could do that,

865
00:44:22,520 --> 00:44:25,600
Speaker 1: but here we separate them in space instead. That would

866
00:44:25,600 --> 00:44:28,080
Speaker 1: be a dessert cone for sure. But I think what

867
00:44:28,080 --> 00:44:30,160
Speaker 1: you're saying is that they did this this experiment and

868
00:44:30,200 --> 00:44:32,880
Speaker 1: it confirmed that. You know, it's sort of like you

869
00:44:32,920 --> 00:44:35,760
Speaker 1: can have two different orders at the same time happening

870
00:44:36,120 --> 00:44:38,839
Speaker 1: quantum mechanically exactly. And what they do are really cool

871
00:44:38,880 --> 00:44:42,480
Speaker 1: things with correlations. It's just like with bells inequality. You know,

872
00:44:42,520 --> 00:44:45,799
Speaker 1: the example of having two quantum entangled particles, where you

873
00:44:45,840 --> 00:44:47,279
Speaker 1: know if one is spin up, the other one has

874
00:44:47,320 --> 00:44:50,799
Speaker 1: to be spinned down. And to prove that they're not

875
00:44:50,920 --> 00:44:53,399
Speaker 1: determined until you open one box, even if they're really

876
00:44:53,400 --> 00:44:56,120
Speaker 1: far apart, you have to do these really subtle experiments

877
00:44:56,200 --> 00:44:59,480
Speaker 1: called probing bells inequality that showed that you can get

878
00:44:59,520 --> 00:45:02,560
Speaker 1: like or relations between the two boxes that you can't

879
00:45:02,600 --> 00:45:05,399
Speaker 1: have otherwise. In the same way they do that. Here,

880
00:45:05,600 --> 00:45:08,120
Speaker 1: they like change what A and B are, they rotate them,

881
00:45:08,160 --> 00:45:10,239
Speaker 1: and they get these correlations between one side and the

882
00:45:10,280 --> 00:45:14,000
Speaker 1: other that you can't have if causality was definite. So

883
00:45:14,080 --> 00:45:17,520
Speaker 1: you have to have indefinite causality to see the specific

884
00:45:17,560 --> 00:45:20,560
Speaker 1: results of these experiments. The patterns, the numbers that they

885
00:45:20,600 --> 00:45:24,279
Speaker 1: get out cannot be reproduced if causality is definitely If

886
00:45:24,320 --> 00:45:27,000
Speaker 1: every photon actually went to one side or the other

887
00:45:27,320 --> 00:45:29,920
Speaker 1: and then merges, that does not explain the results of

888
00:45:29,960 --> 00:45:32,480
Speaker 1: the experiment. It has to be indefinite to get the

889
00:45:32,600 --> 00:45:36,439
Speaker 1: interference patterns and the correlations that they see, right, all right,

890
00:45:36,480 --> 00:45:39,080
Speaker 1: So then it's sort of confirms that the universe is

891
00:45:39,160 --> 00:45:45,239
Speaker 1: CAUSALI ish and definitely causal. So then what does that

892
00:45:45,320 --> 00:45:47,799
Speaker 1: mean for us? Like, does that mean that we can

893
00:45:47,840 --> 00:45:51,880
Speaker 1: now break the rules and then to do cool things

894
00:45:52,080 --> 00:45:54,680
Speaker 1: or does it mean that, you know, it's just another

895
00:45:54,719 --> 00:45:57,920
Speaker 1: sort of step in our sort of befuddlement with quantum mechanics.

896
00:45:58,160 --> 00:46:00,319
Speaker 1: Is there some rule in particular your hope to get

897
00:46:00,360 --> 00:46:03,359
Speaker 1: to break looking for permission? Yeah, you know, I want

898
00:46:03,360 --> 00:46:06,200
Speaker 1: to eat the breakfast coding and not gain weight, reverse

899
00:46:06,840 --> 00:46:10,560
Speaker 1: cause and effect. They're exactly, or you can eat breakfast

900
00:46:10,640 --> 00:46:13,759
Speaker 1: any time of day. No, there are some potential applications

901
00:46:13,800 --> 00:46:15,839
Speaker 1: to this. You know, any time you gain some new

902
00:46:15,960 --> 00:46:18,640
Speaker 1: insight to the way the universe works, you can come

903
00:46:18,719 --> 00:46:20,920
Speaker 1: up with some ways to take advantage of that insight

904
00:46:21,080 --> 00:46:23,719
Speaker 1: to do something you couldn't do before. And so people

905
00:46:23,719 --> 00:46:25,839
Speaker 1: are thinking carefully about what this means, and there's some

906
00:46:25,880 --> 00:46:28,280
Speaker 1: cool things that you can do, like you can send

907
00:46:28,320 --> 00:46:32,440
Speaker 1: more information over noisy channels by using indefinite causality to

908
00:46:32,600 --> 00:46:35,520
Speaker 1: encode some of that extra information, or people have come

909
00:46:35,600 --> 00:46:38,759
Speaker 1: up with like weird quantum computers where two halves the

910
00:46:38,760 --> 00:46:41,560
Speaker 1: computer are not linked by causality, and so they can

911
00:46:41,800 --> 00:46:45,240
Speaker 1: both do their calculation before the other one and send

912
00:46:45,280 --> 00:46:47,279
Speaker 1: the results to the other one, and so you can

913
00:46:47,320 --> 00:46:49,960
Speaker 1: sort of like skip steps there and sort of like

914
00:46:50,080 --> 00:46:52,440
Speaker 1: cheat in time, which is pretty cool. So there's some

915
00:46:52,480 --> 00:46:55,279
Speaker 1: ways people are thinking about using this. For me, it's

916
00:46:55,280 --> 00:46:58,680
Speaker 1: not about the applications, it's about making progress to this

917
00:46:58,800 --> 00:47:01,520
Speaker 1: ultimate theory. You know, we want a deep picture of

918
00:47:01,560 --> 00:47:04,440
Speaker 1: the universe, and we want to understand how the bending

919
00:47:04,480 --> 00:47:07,319
Speaker 1: of space is consistent with quantum mechanics and all this

920
00:47:07,400 --> 00:47:10,360
Speaker 1: crazy stuff. And so it might just be that this

921
00:47:10,719 --> 00:47:14,360
Speaker 1: very way we think about the universe, causality isn't always required.

922
00:47:14,400 --> 00:47:16,879
Speaker 1: It's like it usually happens. It's most of the time

923
00:47:16,920 --> 00:47:19,319
Speaker 1: a good way to describe things, but not something that

924
00:47:19,360 --> 00:47:22,200
Speaker 1: you have to have at the basic core in all

925
00:47:22,280 --> 00:47:24,960
Speaker 1: the deep equations, and so that would you think maybe

926
00:47:25,239 --> 00:47:27,800
Speaker 1: give us some insight into merging these two theories together

927
00:47:28,160 --> 00:47:32,200
Speaker 1: quantum mechanics and general relativity. Yeah, exactly. This is a

928
00:47:32,239 --> 00:47:35,080
Speaker 1: stumbling block, right, as we talked about before. If you

929
00:47:35,200 --> 00:47:38,640
Speaker 1: have general relativity, which bend space, and you have quantum mechanics,

930
00:47:38,760 --> 00:47:43,160
Speaker 1: which makes that bending uncertain, then causality is no longer clear.

931
00:47:43,280 --> 00:47:46,040
Speaker 1: And that's been a problem for quantum gravity. So maybe

932
00:47:46,040 --> 00:47:48,400
Speaker 1: the answer is like, well, just act like it's not

933
00:47:48,440 --> 00:47:51,560
Speaker 1: a problem. Maybe it's actually okay, you know, maybe this

934
00:47:51,719 --> 00:47:53,920
Speaker 1: wasn't a wall in our progress. We just need to

935
00:47:53,920 --> 00:47:56,359
Speaker 1: so like not worry about it so much. Yeah, that's

936
00:47:56,400 --> 00:48:00,000
Speaker 1: my favorite way to deal with problems, Daniel, Just tocore them.

937
00:48:00,360 --> 00:48:02,560
Speaker 1: Just don't look at the scale when you weigh yourself,

938
00:48:02,920 --> 00:48:04,919
Speaker 1: and then you don't have to worry about causing it. Well,

939
00:48:04,960 --> 00:48:06,640
Speaker 1: it is an important lesson and the way we think

940
00:48:06,680 --> 00:48:09,040
Speaker 1: about things, you know, we put up mental barriers. Sometimes

941
00:48:09,120 --> 00:48:12,319
Speaker 1: we imagine like, oh, well that's impossible, they can't be

942
00:48:12,480 --> 00:48:14,239
Speaker 1: and then later people come along and they're like, well,

943
00:48:14,280 --> 00:48:17,800
Speaker 1: actually why not, or you know, why are we following?

944
00:48:17,840 --> 00:48:20,520
Speaker 1: This rule? Is there's really actually important. And then they

945
00:48:20,560 --> 00:48:23,960
Speaker 1: discovered this is a whole rich area of exploration, you know,

946
00:48:24,200 --> 00:48:27,640
Speaker 1: think about like imaginary numbers. People for a long time thought, well,

947
00:48:27,680 --> 00:48:29,800
Speaker 1: that's ridiculous, it's nonsense, but it turns out to be

948
00:48:29,880 --> 00:48:32,759
Speaker 1: really important branch of mathematics for understanding the way the

949
00:48:32,840 --> 00:48:36,200
Speaker 1: universe works. And so sometimes you've got to like knock

950
00:48:36,239 --> 00:48:39,200
Speaker 1: on these mental walls and discover that there's actually lots

951
00:48:39,200 --> 00:48:41,440
Speaker 1: of interesting territory on the other side. Yeah, I think

952
00:48:41,440 --> 00:48:44,040
Speaker 1: that should be your new slogan for physics. You know,

953
00:48:44,239 --> 00:48:48,080
Speaker 1: physics colon. Why not? You know, Nike has just do it?

954
00:48:48,239 --> 00:48:51,080
Speaker 1: You should have Why not haven't destroyed the universe yet?

955
00:48:52,600 --> 00:48:55,480
Speaker 1: Why not put scrambled eggs in that cone? Seriously, that's

956
00:48:55,480 --> 00:48:58,000
Speaker 1: a great idea. All right, Well, we hope you enjoyed that,

957
00:48:58,200 --> 00:49:00,160
Speaker 1: and you know, got you to think a little bit

958
00:49:00,160 --> 00:49:02,959
Speaker 1: about what we think is certain in this universe. Maybe

959
00:49:03,200 --> 00:49:04,880
Speaker 1: things are not as certain as we think they are,

960
00:49:04,960 --> 00:49:08,919
Speaker 1: even the basic logic of how and when things happen.

961
00:49:09,200 --> 00:49:11,200
Speaker 1: And that goes to show you that there are still

962
00:49:11,360 --> 00:49:14,680
Speaker 1: really deep end basic questions out there that people are

963
00:49:14,719 --> 00:49:18,120
Speaker 1: struggling with about the nature of the universe. And maybe

964
00:49:18,160 --> 00:49:21,080
Speaker 1: what we're missing is one really cool flash of insight.

965
00:49:21,560 --> 00:49:24,080
Speaker 1: And maybe you will have that flash of insight and

966
00:49:24,120 --> 00:49:28,399
Speaker 1: revolutionize the way everybody thinks about the universe. Why not, Well,

967
00:49:28,440 --> 00:49:31,200
Speaker 1: we hope you enjoyed that. Thanks for joining us, see

968
00:49:31,200 --> 00:49:41,600
Speaker 1: you next time. Thanks for listening, and remember that Daniel

969
00:49:41,600 --> 00:49:44,120
Speaker 1: and Jorge explained the universe is a production of I

970
00:49:44,360 --> 00:49:47,799
Speaker 1: Heart Radio or more podcast from my heart Radio, visit

971
00:49:47,840 --> 00:49:51,319
Speaker 1: the I heart Radio app, Apple Podcasts, or wherever you

972
00:49:51,440 --> 00:49:58,680
Speaker 1: listen to your favorite shows. Yeah,