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Speaker 1: Hey, Jorge, are you worried about energy conservation?

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Speaker 2: Uh?

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Speaker 3: Not worried, but I try to do as much of

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Speaker 3: it as possible.

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Speaker 4: Oh.

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Speaker 1: Is that because you're very environmentally responsible?

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Speaker 3: Nuts? Because I try to do this little exercise as possible.

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Speaker 1: You're such an adult.

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Speaker 3: Hey, I'm doing it for the planet, not just for me.

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Speaker 1: Well on behalf of planet Earth. We're all very grateful

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Speaker 1: for your lazy attitude.

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Speaker 3: Oh thanks. My body is also very grateful, although maybe

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Speaker 3: not in the long term. Hi am Jorgem, a cartoonist

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Speaker 3: and the author of Oliver's Great Big Universe.

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Speaker 1: Hi. I'm Daniel. I'm a high energy particle physicist, but

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Speaker 1: I don't often feel very high energy or high. There

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Speaker 1: were times in my life when that was more true.

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Speaker 3: Than Yeah, I seem to remember those times. Yeah. But

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Speaker 3: isn't it high a relative term at least in physics?

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Speaker 3: Like how high is high energy? Can't you always go

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Speaker 3: higher in energy?

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Speaker 1: You can always go higher in energy? And what people

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Speaker 1: called high energy fifty years ago we now call nuclear physics.

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Speaker 1: So it doesn't even qualify what it's not low energy,

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Speaker 1: It doesn't even qualify as low energy physics.

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Speaker 3: I guess nobody wants to be called a low energy physicist.

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Speaker 1: Yeah, would you want to be called a low energy cartoonist?

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Speaker 3: Well, I am, and if you call me that it

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Speaker 3: would be accurate. But I guess you can call me that,

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Speaker 3: why not?

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Speaker 1: Yeah? Sure? Well, high energy really means highest energy. And

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Speaker 1: as we keep pushing the boundaries of what we can achieve,

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Speaker 1: then yesterday's high energy collider is today's nuclear physics.

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Speaker 3: Mm sounds like a good slogan for the LGC. Yesterday's

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Speaker 3: high energies now today's nuclear energy. But anyways, welcome to

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Speaker 3: our podcast Daniel and Jorge Explain the Universe, a production

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Speaker 3: of iHeartRadio.

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Speaker 1: In which we use all of our energy to help

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Speaker 1: you understand the nature of the universe. We tear things apart,

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Speaker 1: we peer inside. We try to understand at a microscopic level,

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Speaker 1: how does everything work? Is there a story we can

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Speaker 1: tell about what's happening to the littlest bits in the

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Speaker 1: universe and how it comes together to explain our reality?

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Speaker 3: That's right. We like to explore the high energies, the

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Speaker 3: low energies, and all the energies in between that there

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Speaker 3: are in this universe to discover, to explore, to learn about,

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Speaker 3: and to blow your mind with.

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Speaker 1: And energy is a really central concept in physics and

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Speaker 1: in people's understanding of physics. We'd like to think about

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Speaker 1: things in terms of energy, little quantum fields vibrating with energy,

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Speaker 1: energy being passed between particles, energy used to create particles.

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Speaker 1: In some sense, physics is a study.

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Speaker 3: Of energy, and one that requires some amount of energy

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Speaker 3: to explore, right, I mean, you can't just do physics

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Speaker 3: from your couch.

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Speaker 5: Can you.

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Speaker 1: I don't know if it takes more energy to do

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Speaker 1: physics or cartooning, but you can sort of lie in

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Speaker 1: your couch and just think about the universe, you know,

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Speaker 1: the way the great theorists and the Greeks have done.

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Speaker 1: But absolutely to do experiments to explore the universe, to

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Speaker 1: investigate it deeply, you need to poke it, you need

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Speaker 1: to probe it, you need to interact with it, and

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Speaker 1: that does take some energy.

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Speaker 3: Well, I feel like energy is kind of a topic,

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Speaker 3: that it's a word you learn as a kid, and

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Speaker 3: that everybody has heard of this word and we all

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Speaker 3: use it every day in our everyday lies. But to

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Speaker 3: actually define energy is kind of tricky, isn't it, Not

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Speaker 3: just from a physics point of view, but also if

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Speaker 3: you ask somebody what energy is, You don't get an

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Speaker 3: easy answer.

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Speaker 1: Yeah, energy is a very loaded term, right. We have

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Speaker 1: a sense of like feeling like you have low energy

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Speaker 1: in the morning, or running out of energy to do

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Speaker 1: some chores or something. But it's one of these words

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Speaker 1: that physics has redefined to have a specific meaning, a

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Speaker 1: very crisp idea for what energy means. The way we

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Speaker 1: also have like meanings for force and work and other

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Speaker 1: words that we also use in everyday English without as

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Speaker 1: precise definitions.

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Speaker 3: Right, But even those the simple terms have been changing

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Speaker 3: in physics over time, right, Like the word the idea

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Speaker 3: for force has changed with quantum mechanics. Isn't it Like

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Speaker 3: it used to be an invisible force that we feel

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Speaker 3: towards the Earth or the sun, But now they're talking

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Speaker 3: that maybe it's like a particle or something, it's an

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Speaker 3: exchange of particles.

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Speaker 1: Yeah, the mechanism that explains it is definitely different. I

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Speaker 1: think the concept of force is a change in momentum

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Speaker 1: of something. Something in exchange of momentum essentially has been

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Speaker 1: pretty constant since Newton. Yeah, these things definitely can change.

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Speaker 1: And you know, for example, we've redefined gravity to not

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Speaker 1: even be a force, So what gets counted as a

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Speaker 1: force and what doesn't and how that all works definitely changes.

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Speaker 1: And we like to dig into these basic principles and say, like,

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Speaker 1: what does this really mean? Where does it come from?

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Speaker 1: Did the universe have to me this way? Is energy

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Speaker 1: essential to the universe? And one of the ways that

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Speaker 1: we do that is by noticing what the universe respects,

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Speaker 1: like what doesn't change in the universe, what's constant, what's conserved.

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Speaker 1: That gives you a clue about sort of what's important

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Speaker 1: to the underlying machinery of the universe.

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Speaker 3: Right, you kind of want to know what the rules

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Speaker 3: of the universe are, or what the principles of the

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Speaker 3: universe are by which it lets things happen in it,

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Speaker 3: right exactly.

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Speaker 1: And one of the deepest rules that people imagine in

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Speaker 1: the universe follows is conservation of energy. That energy is

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Speaker 1: somehow immutable, that it can slosh between different kinds of

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Speaker 1: energy kinetic to potential, to mass, to velocity to whatever.

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Speaker 1: But the energy has to go somewhere and has to

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Speaker 1: come from somewhere. That it's a basic component of the

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Speaker 1: universe itself.

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Speaker 3: Yeah, it's a very fundamental rule that people seem to

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Speaker 3: learn about even in high school physics. But is it

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Speaker 3: actually true? Does it always happen in this universe or

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Speaker 3: does it get broken at some levels, like the quantum levels.

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Speaker 3: And so to the end the podcast, we'll be asking

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Speaker 3: the question does quantum mechanics conserve energy? Now, when you

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Speaker 3: say quantum mechanics, do you mean like the field or

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Speaker 3: the people who study quantum mechanics.

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Speaker 1: The mechanics of quantum physics.

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Speaker 3: Can you be a quantum mechanic like a car mechanic,

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Speaker 3: but at the quantum level.

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Speaker 1: Yeah, bring your fields in. They need some new parts.

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Speaker 1: We'll order them.

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Speaker 3: That's right, Your quantum carburetor needs to be swapped out, exactly.

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Speaker 1: No, in this case, we're talking about the rules of

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Speaker 1: the smallest bits in the universe, the tiniest little things,

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Speaker 1: the electrons, the positrons of photons, all the smallest stuff

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Speaker 1: in the universe seems to operate on different rules than

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Speaker 1: the bigger stuff in the universe baseballs and basketballs and

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Speaker 1: rocks and stuff that we're familiar with. And so while

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Speaker 1: we're taught that energy is concerned very generally, we're interested

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Speaker 1: in whether that's always true, and whether it's true at

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Speaker 1: the smallest scale.

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Speaker 3: Yeah, so this is a big question. Does quantum mechanics

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Speaker 3: conserve energy? And so, as usually, we were wondering how

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Speaker 3: many people out there had thought about this question, whether

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Speaker 3: this is a rule that can be broken at the

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Speaker 3: quantum level, or whether the whole universe follows it.

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Speaker 1: Thanks very much to everybody who answers these questions. If

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Speaker 1: you would like to receive a regular dose of tough

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Speaker 1: physics questions in your inbox, right to me too, questions

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Speaker 1: at Danielandhorge dot com, and I will send them to you.

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Speaker 3: Well, regular dose. Now do these doses make you high

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Speaker 3: in physics?

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Speaker 1: These are microdoses, so yeah.

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Speaker 3: Oh, I see right, it's more of a low key high.

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Speaker 1: They're not supposed to blow your mind. They're just supposed

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Speaker 1: to color your experience of the universe a little bit.

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Speaker 3: I see. It's more of a nuclear.

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Speaker 1: Hit exactly, It's not a high energy dose.

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Speaker 3: Well, think about it for a second. Do you think

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Speaker 3: quantum mechanics conserves energy? Here's what people have to say.

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Speaker 5: I think so, or at least the rate of decay

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Speaker 5: is so minute that we are not currently able to

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Speaker 5: detect it on a cosmological scale.

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Speaker 6: I think quantum mechanics conserves energy. I feel like it

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Speaker 6: would be big news if we found the law of

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Speaker 6: conservation of energies to be violated, though maybe it has

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Speaker 6: been and I just haven't seen that news. But the

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Speaker 6: notion of quantum fluctuations seems like it would violate that law.

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Speaker 6: Though I don't really understand quantum fluctuations.

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Speaker 2: I'm assuming it doesn't just because I remember listening to

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Speaker 2: your podcast on how energy actually isn't conserved in the universe.

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Speaker 2: So I'm assuming that quantum mechanics follows that as well,

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Speaker 2: But I don't actually know.

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Speaker 4: I'm not sure about this question. And like conserve in

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Speaker 4: what like in your book frequently asked questions about the universe,

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Speaker 4: you did say like there was like a quantum foam,

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Speaker 4: and like when the universe is expanding, it's just connecting

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Speaker 4: to more quantum particles, I guess. So I'm going to say,

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Speaker 4: I don't know, because if you mean in the universe,

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Speaker 4: like not the growing section, then no. But if we

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Speaker 4: even include all the other disconnected quantum phone then I'm

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Speaker 4: not sure.

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Speaker 3: All right. People are on the fence about this. Some

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Speaker 3: people say it does, some people say they don't think so. Well,

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Speaker 3: they're not sure.

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Speaker 1: Yeah, I was really surprised by this. I was expecting

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Speaker 1: people to rush to the defense of conservation of energy

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Speaker 1: and say it's a fundamental law of the universe.

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Speaker 3: Maybe it's because we've had whole episodes where we say

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Speaker 3: that the energy is not conserving the universe that maybe

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Speaker 3: influence the answers here.

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Speaker 1: Oh my gosh, people actually listening and absorbing the content.

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Speaker 3: Amazing, amazing, they're learning. Well, it's great that they are

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Speaker 3: listening to us. And because we have talked about this

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Speaker 3: idea of conservation of energy in the universe, and we've

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Speaker 3: talked about how it's not actually conserved in the universe

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Speaker 3: as a whole.

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Speaker 1: Right, that's right, And that was in the context of

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Speaker 1: sort of general relativity, thinking about the universe as it

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Speaker 1: expands and as space is changing, how we define energy

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Speaker 1: in that context, and that sort of blows a lot

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Speaker 1: of people's minds to understand that energy might not be

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Speaker 1: conserved in the universe at the biggest scales, you know,

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Speaker 1: when you zoom all the way out and think about

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Speaker 1: how the universe is expanding and what happens to stuff

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Speaker 1: inside of it.

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Speaker 3: Right, Because in the other episode we talked about how

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Speaker 3: the universe is expanding due to dark energy, and basically

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Speaker 3: like there's more space being created all the time out

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Speaker 3: of nothing, which means that energy sort of being added

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Speaker 3: to the universe, created in the universe out of nothing.

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Speaker 1: Right, Yeah, that's right, and you're coming out of nothing,

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Speaker 1: I think says a lot. You know, it implies that

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Speaker 1: energy needs to come from somewhere, and so when you

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Speaker 1: say energy is created, you have to give some explanation

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Speaker 1: for where it comes from, even if you're saying out

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Speaker 1: of nothing. But this tells us that energy isn't something

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Speaker 1: fundamental to the universe. That it can go up and

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Speaker 1: it can go down, like lots of things in the universe,

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Speaker 1: like the number of people in swimming pools is not

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Speaker 1: a constant number of the universe. It can go up

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Speaker 1: and it can go down.

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Speaker 3: How do you know? Are you sure the.

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Speaker 1: Middle of an extensive worldwide experiment to measure the number

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Speaker 1: of people.

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Speaker 3: At any moment? Yes, Oh, you thought you were going to.

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Speaker 1: Challenge me on that and call me out, But actually

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Speaker 1: I've been doing this in preparation for five years just

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Speaker 1: to make that casual comment.

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Speaker 3: You know, somehow I don't believe you any.

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Speaker 1: Away from my paper in nature. Okay, it's coming out soon,

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Speaker 1: I promise.

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Speaker 3: Sure. Let's see the draft. Read me a poll paragraph

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Speaker 3: from the draft right now.

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Speaker 1: Oh, I can't disembargo it because it's too high profile.

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Speaker 3: I see.

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Speaker 1: I signed an NBA. What am I gonna do? No,

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Speaker 1: obviously I have not done that experiment.

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Speaker 3: A nuclear disclosure agreement, which means it's really low.

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Speaker 1: But clearly there are things in the universe that do change,

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Speaker 1: things that are not fundamental to the universe, while there

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Speaker 1: are other things that are fundamental, like momentum. We think

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Speaker 1: momentum is conserved in the universe, and that comes from

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Speaker 1: a really deep symmetry about space and time that the

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Speaker 1: experiments you do anywhere in the universe should give you

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Speaker 1: the same answer. That doesn't matter where you put your

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Speaker 1: origin in space. Rules of physics don't care, and that

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Speaker 1: gives you directly as a consequence of Nuther's theorem, momentum conservation.

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Speaker 1: But energy is not in that same category, and energy

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Speaker 1: can go down and it can go up, like when

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Speaker 1: the universe expands, you get in new space, and that

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Speaker 1: space comes with energy, but also energy gets decreased because

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Speaker 1: as space expands, it reddens the wavelengths of all the

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Speaker 1: photons inside of it. Take for example, the cosmic microwave

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Speaker 1: background radiation from the early universe. When it was created,

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Speaker 1: it was very high energy. That plasma was super dup

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Speaker 1: or hot. It was thousands of degrees kelvin. But it's

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Speaker 1: been stretched out by the expansion of the universe to

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Speaker 1: very long wavelengths, and now it's at like three degrees kelvin.

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Speaker 1: Where do that energy go? Didn't go anywhere, it's just gone.

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Speaker 3: Well, it's not gone, it's just gonna spread out, is it.

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Speaker 1: No, there's less energy in those photons. Those photons have

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Speaker 1: gone from high energy to low.

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Speaker 3: Energy because they got stretched out.

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Speaker 1: But the total energy is also different. It's not just

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Speaker 1: the energy density.

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Speaker 3: But they're longer now, that's what those are longer. Yeah,

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Speaker 3: isn't where the energy went.

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Speaker 1: The energy of those photons is less. They're also longer,

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Speaker 1: but the energy of those photons is less. If you

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Speaker 1: stretch space, the photons get redder, which means they have

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Speaker 1: less energy.

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Speaker 3: Well, I guess this is what I mean. Because the

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Speaker 3: idea of energy, the concept of energy can really vary

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Speaker 3: into a lot of these arguments about whether it can

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Speaker 3: can be conserved or not. I feel like maybe they

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Speaker 3: depend on a good definition of energy, and so maybe

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Speaker 3: for folks we should talk about what energy actually is,

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Speaker 3: how to physicists define it.

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Speaker 1: Yeah, I wish I knew what energy was.

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Speaker 3: Wait, what.

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Speaker 1: Energy is a really slippery topic. It's something we've been

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Speaker 1: struggling with over the last few decades to really define.

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Speaker 1: We have some very crisp but unsatisfying definitions of energy.

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Speaker 1: You know, in some cases you can say energy is

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Speaker 1: the thing that's conserved over time, you know, so you

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Speaker 1: can define it to be something that's conserved. Really, I

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Speaker 1: think a better way to define energy is to talk

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Speaker 1: about like the forms it can take. You know, like

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Speaker 1: there's kinetic energy, which means energy of motion. Something is

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Speaker 1: moving that has energy. There's potential energy, this energy of configuration.

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Speaker 1: Like a book is sitting on the shelf, there's energy

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Speaker 1: stored in that. You know, it takes energy to put

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Speaker 1: the book on the shelf. Mass, for example, is a

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Speaker 1: representation of internal stored energy. Put a bunch of photons

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Speaker 1: into a box, they have energy. That box now has

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Speaker 1: more mass. All these are different ways you can calculate energy,

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Speaker 1: and if you add them all up, you get the

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Speaker 1: total energy. And so that's sort of how we define energy,

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Speaker 1: but you know it's a little hand wavy.

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Speaker 3: Wait wait, wait, So I was right earlier when I

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Speaker 3: said that I don't really know what energy kind of is,

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Speaker 3: but you made it seem like we did know.

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Speaker 1: We don't really know what energy is in the broadest sense,

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Speaker 1: but we can define something and say this is what

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Speaker 1: we call energy. I don't know if it really captures

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Speaker 1: our full experience of energy, but yeah, we can write

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Speaker 1: down a formula for what energy is.

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Speaker 3: But I guess the question is what did those things

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Speaker 3: have in common? And why do you use the same

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Speaker 3: word for all of them? The kinetic energy, potential energy,

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Speaker 3: you know, energy of mass. Why do you use the

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Speaker 3: same word for all of those things?

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Speaker 1: Yeah, great question, And the reason is that in classical

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Speaker 1: mechare at least, you know, things moving around at our

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Speaker 1: scale at or fairly low speeds. We notice that they

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Speaker 1: can turn back and forth into each other. Like you

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Speaker 1: take that book on the shelf. It has potential energy

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Speaker 1: and no kinetic energy. You push it off the shelf.

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Speaker 1: Now it's speeding up towards the ground. It's losing potential

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Speaker 1: energy and gaining kinetic energy. So we notice that these

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Speaker 1: things can turn into each other, and therefore we group

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Speaker 1: them together into one big category. And we notice that,

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Speaker 1: at least in classical mechanics, the total the sum of

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Speaker 1: them all does stay constant. So like if you're add

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Speaker 1: of all the potential energy and all the kinetic energy

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Speaker 1: at one moment, and you do it again later, you

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Speaker 1: find you get the same answer.

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Speaker 3: And how does that relate to the energy of a

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Speaker 3: photocon which you mentioned earlier.

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Speaker 1: So now we're departing classical mechanics a little bit. We're

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Speaker 1: talking about a quantum object, but we can still think

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Speaker 1: about the energy of a photon. A photon has kinetic

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Speaker 1: energy because it's in motion, it's always in motion. It

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Speaker 1: has only kinetic energy. So photons definitely have energy.

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Speaker 3: Well, it seems like maybe the common factor is the

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Speaker 3: idea of motion, like things moving have energy to them,

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Speaker 3: and things that can move in the future or can

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Speaker 3: cost things to move, or like the potential to cost

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Speaker 3: something to move, is what maybe you would call energy.

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Speaker 1: Maybe I think that puts kinetic energy in a more

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Speaker 1: primary position than potential energy, which I'm not sure is justified.

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Speaker 1: I think there really are at its core two different

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Speaker 1: kinds of energy. There stored energy potential energy and kinetic energy.

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Speaker 1: I'm not sure which one would be more fundamental.

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Speaker 3: And so are those the only two kinds of energy?

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Speaker 3: So you have in classical physics kinetic and potential.

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Speaker 1: Yeah, those are the two forms. People might think, what

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Speaker 1: about mass? What is mass? Is that kinetic energy or

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Speaker 1: potential energy? It's sort of a special case. It's just

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Speaker 1: sort of a label we give some kinds of energy

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Speaker 1: if they're stored internally, Like if you have gluons inside

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Speaker 1: of proton, they have a bunch of kinetic energy they're

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Speaker 1: zooming around. They also have potential energy of their bonds.

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Speaker 1: All that energy is inside the proton, so we call

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Speaker 1: that mass. So mass is sort of a label we

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Speaker 1: give to some energy, but it's not on the same

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Speaker 1: level as like kinetic and potential it's not its own

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Speaker 1: kind of energy.

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Speaker 3: So then if an eight year old asked you, hey,

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Speaker 3: doctor Whitson, what is energy? What would you answer?

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Speaker 1: I would say, I've had this nightmare scenario many times

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Speaker 1: and I have no idea how to respond.

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Speaker 3: You would spring in their face, Ah, run away, No, seriously, like,

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Speaker 3: what would you say, you have to say something? What

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Speaker 3: would you say, I'll get you started. It's a quantity that.

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Speaker 1: I'd say, energy is something that makes things move, but

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Speaker 1: it's also something you can store. That's my best shot.

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Speaker 3: It's almost like a liquid or something.

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Speaker 1: You know, for a long time people did imagine that

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Speaker 1: energy in the form of heat was a liquid that

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Speaker 1: flowed between things. But it's not a physical quantity in itself.

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Speaker 1: It's a description of the physical state of other quantities.

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Speaker 1: Like a liquid can have energy, but so can solids.

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Speaker 1: It's not like when energy flows from one thing to another,

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Speaker 1: there's some physical substance that moves between it. It changes

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Speaker 1: the state of those objects.

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Speaker 3: Well, I guess I'm a little surprised you're having so

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Speaker 3: much trouble just defining energy, which is pretty interesting. But

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Speaker 3: as you said, I think one thing that we do

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Speaker 3: sort of know about it is that in some cases

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Speaker 3: it's conserved and maybe in some cases it's not.

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Speaker 1: So.

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Speaker 3: Well, let's dig into the question and when it's conserved,

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Speaker 3: is it conserved at the quantum level or is it not.

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Speaker 3: So let's dig into that, But first let's take a

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Speaker 3: quick break. All right, we are mustering up the energy

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Speaker 3: to talk about something that apparently physicists can't define energy,

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Speaker 3: such a basic word that even little kids use, everyone

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Speaker 3: uses their in their daily lives. But it seems Daniel,

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Speaker 3: that it's something physicists can't really define very well. Maybe

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Speaker 3: only mathematically you can define it. Is that kind of

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Speaker 3: the case.

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Speaker 1: Yeah, And as you'll see, when we get into the

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Speaker 1: quantum system, this is going to be even trickier. And

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Speaker 1: physicists disagree about how to define energy and whether we

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Speaker 1: can even define it in terms of quantum systems.

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Speaker 3: Well, it seems like we don't even need to get

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Speaker 3: through you already don't know how to define it exactly.

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Speaker 1: And that's why I want to be upfront about how

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Speaker 1: complicated and confusing this topic is, even in the easy case,

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Speaker 1: because when we get to the hard case, it's going

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Speaker 1: to get even trickier. So I did my best to

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Speaker 1: give you like my understanding of energy, but if you

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Speaker 1: look at the official definition of energy, I find it's

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Speaker 1: even less satisfying. Like if you just google energy and

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Speaker 1: you ask Wikipedia or chat GPT, like, what is energy?

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Speaker 3: Well, it's you know, legit sources.

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Speaker 1: Legit sources. They say energy is the quantitative property that

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Speaker 1: is transferred to a body, and that doesn't really even

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Speaker 1: tell you what it is. It's like Okay, well, it

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Speaker 1: can move from one thing to another, but what is it? Man,

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Speaker 1: it doesn't really answer that question.

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Speaker 3: Well, that's kind of what I meant before, is that

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Speaker 3: it's a quantity. Is basically kind of the only way

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Speaker 3: you physicists know how to define it, right, it's a

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Speaker 3: it's a quantity. It's something that can measure, that can

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Speaker 3: be a lot or a little, which you seem to

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Speaker 3: be able to measure about things, and that sometimes seems

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Speaker 3: to be conserved.

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Speaker 1: So mathematically, we can write down a formula that defines it,

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Speaker 1: and then it's defined in terms of things we can

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Speaker 1: measure like velocity and position and stuff like this. And

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Speaker 1: it turns out that if you write it in certain ways,

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Speaker 1: then that number doesn't change. The internal values can slash

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Speaker 1: back and forth, but the total doesn't change. That's sort

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Speaker 1: of like the crispest most mathematical definition. But I think

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Speaker 1: what we're proving forward is like what does it mean philosophically?

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Speaker 1: Like what are the implications of that? And that's much trickier.

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Speaker 3: Well, you seem to not want to give primacy to

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Speaker 3: kinetic energy, but in a way, that's kind of like

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Speaker 3: our most direct experience of energy, which is motion, right,

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Speaker 3: Like if something has a lot of energy to either

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Speaker 3: moving fast, or it's hot or it's exploding. For us,

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Speaker 3: in our experience of the universe, energy is basically things

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Speaker 3: moving fast or things that can make things move fast.

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Speaker 1: Yeah, if you're talking about the experience of it, then

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Speaker 1: you more directly experience motion than stored energy. It's energy

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Speaker 1: you don't really experience when it's stored because it's just

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Speaker 1: being stored. It's when it's transformed into kinetic energy that

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Speaker 1: you're experiencing it. Like if you zap yourself on a battery,

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Speaker 1: it's the motion of those electrons being transformed from the

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Speaker 1: potential into their kinetic energy that's zapping you.

440
00:21:19,600 --> 00:21:22,879
Speaker 3: All right. So then you said that sometimes it's conserved

441
00:21:22,920 --> 00:21:26,399
Speaker 3: and sometimes it's not. So when is energy conserved in

442
00:21:26,440 --> 00:21:27,200
Speaker 3: a classical way?

443
00:21:27,359 --> 00:21:31,240
Speaker 1: In classical sense, energy is only conserved when space time

444
00:21:31,400 --> 00:21:34,320
Speaker 1: is not curved and when space time is not changing.

445
00:21:34,960 --> 00:21:37,119
Speaker 1: So if space time is fixed, like you have flat

446
00:21:37,160 --> 00:21:40,040
Speaker 1: space time, meaning you shoot two photons and they stay

447
00:21:40,080 --> 00:21:43,000
Speaker 1: parallel to each other, then you can expect energy to

448
00:21:43,080 --> 00:21:45,920
Speaker 1: be conserved. But if that space is changing, like it's

449
00:21:45,960 --> 00:21:48,960
Speaker 1: expanding the way our universe is, then the general relativity,

450
00:21:49,080 --> 00:21:52,479
Speaker 1: energy is not conserved. Even more generally, anytime you have

451
00:21:52,680 --> 00:21:56,439
Speaker 1: curved space in general relativity, you do not have conservation

452
00:21:56,520 --> 00:21:59,800
Speaker 1: of energy. So, for example, black holes colliding do not

453
00:22:00,119 --> 00:22:01,080
Speaker 1: conserve energy.

454
00:22:01,240 --> 00:22:02,520
Speaker 3: Wait, what what do you mean.

455
00:22:02,400 --> 00:22:04,439
Speaker 1: When two black holes collide? You have the collision of

456
00:22:04,480 --> 00:22:06,879
Speaker 1: two curved bits of space, and what comes out of

457
00:22:06,920 --> 00:22:08,960
Speaker 1: that is not the sum of what goes into that.

458
00:22:09,000 --> 00:22:11,320
Speaker 1: You're not guaranteed that in general relativity.

459
00:22:11,520 --> 00:22:15,359
Speaker 3: But is in space always curved like uncurving space around me,

460
00:22:16,359 --> 00:22:18,320
Speaker 3: and yet I don't seem to have infinite energy.

461
00:22:18,560 --> 00:22:20,560
Speaker 1: That's right, you do not have infinite energy and you

462
00:22:20,560 --> 00:22:23,320
Speaker 1: are curving space around you. But the total amount of

463
00:22:23,440 --> 00:22:27,199
Speaker 1: energy in the system changes in time in general relativity,

464
00:22:27,480 --> 00:22:30,000
Speaker 1: and it gets really fuzzy and weird because general relativity

465
00:22:30,040 --> 00:22:32,320
Speaker 1: is really hard to think about in some reference frames.

466
00:22:32,359 --> 00:22:35,439
Speaker 1: According to generalativity, energy is conserved in others, it's not.

467
00:22:35,880 --> 00:22:37,719
Speaker 1: Depends sort of on how you're looking at things.

468
00:22:37,960 --> 00:22:40,160
Speaker 3: Okay, it sort of sounds like you're saying like, if

469
00:22:40,160 --> 00:22:43,359
Speaker 3: you don't think about general relativity, then you can assume

470
00:22:43,359 --> 00:22:46,320
Speaker 3: that energy is being conserved. If you assume that there's

471
00:22:46,359 --> 00:22:49,280
Speaker 3: general relativity and things are being space is being bent

472
00:22:49,960 --> 00:22:52,200
Speaker 3: like around black holes or the expansion of the universe.

473
00:22:52,240 --> 00:22:55,040
Speaker 3: Then you can't assume that energy is being conserved.

474
00:22:54,640 --> 00:22:56,359
Speaker 1: As long as we're above the quantum level.

475
00:22:56,480 --> 00:22:58,920
Speaker 3: Right, So it's mostly like whether or not you ignore

476
00:22:59,119 --> 00:23:00,560
Speaker 3: the bunding of space exactly.

477
00:23:00,600 --> 00:23:03,240
Speaker 1: If you can ignore the bending or expansion of space time,

478
00:23:03,400 --> 00:23:06,160
Speaker 1: then classically you can think of energy as conserved.

479
00:23:06,280 --> 00:23:08,000
Speaker 3: Right. And so we talked about that the universe is

480
00:23:08,040 --> 00:23:11,199
Speaker 3: expanding and so therefore energy is not being concernedd and

481
00:23:11,200 --> 00:23:14,359
Speaker 3: we talked about two black holes colliding. Energy is not

482
00:23:14,400 --> 00:23:16,720
Speaker 3: being conserved there So now the question of the episode

483
00:23:16,800 --> 00:23:19,040
Speaker 3: is when you get down to the quantum level, is

484
00:23:19,320 --> 00:23:23,800
Speaker 3: energy still conserved even though maybe there's no space time

485
00:23:23,840 --> 00:23:25,960
Speaker 3: bending at the quantum level. If you assume there's no

486
00:23:26,040 --> 00:23:30,159
Speaker 3: bending at the quantum level, does energy get conserved.

487
00:23:30,280 --> 00:23:32,280
Speaker 1: Yeah, And we have to assume there's no space time

488
00:23:32,320 --> 00:23:34,199
Speaker 1: bending at the quantum level because we don't know how

489
00:23:34,200 --> 00:23:36,600
Speaker 1: to do quantum mechanics when space is curved and you

490
00:23:36,600 --> 00:23:40,040
Speaker 1: have gravity, and gravity for particles is something we don't understand.

491
00:23:40,400 --> 00:23:43,520
Speaker 1: So let's assume space is totally flat and we have objects,

492
00:23:43,560 --> 00:23:46,800
Speaker 1: you know, like baseballs and rocks for which we think

493
00:23:47,000 --> 00:23:49,760
Speaker 1: energy is conserved and then zoomed down to the quantum

494
00:23:49,840 --> 00:23:52,320
Speaker 1: level and try to understand when you have photons and

495
00:23:52,359 --> 00:23:56,280
Speaker 1: electrons instead of rocks and baseballs, is energy still conserved?

496
00:23:56,480 --> 00:23:59,000
Speaker 1: And really the deep question is like, is energy conservation

497
00:23:59,119 --> 00:24:01,960
Speaker 1: something that's through in through the universe at every scale

498
00:24:02,119 --> 00:24:04,720
Speaker 1: or is this something that emerges only at the scale

499
00:24:04,760 --> 00:24:07,760
Speaker 1: we experience it out of something that operates totally differently,

500
00:24:07,920 --> 00:24:11,200
Speaker 1: because remember, quantum mechanics breaks all the rules of classical physics.

501
00:24:11,440 --> 00:24:14,480
Speaker 1: It says things don't actually have well defined positions and locations,

502
00:24:14,480 --> 00:24:16,720
Speaker 1: and lots of the things that emerge at our level

503
00:24:16,720 --> 00:24:18,560
Speaker 1: are not true at the quantum level. So it's not

504
00:24:18,600 --> 00:24:22,440
Speaker 1: guaranteed that everything about our experience will be translated down

505
00:24:22,440 --> 00:24:23,320
Speaker 1: to the quantum level.

506
00:24:23,359 --> 00:24:25,560
Speaker 3: All right, So then let's answer the question, does quantum

507
00:24:25,560 --> 00:24:27,240
Speaker 3: mechanics can serve energy or not?

508
00:24:27,440 --> 00:24:29,359
Speaker 1: So the short answer is we don't know.

509
00:24:29,600 --> 00:24:32,160
Speaker 3: Surprise, surprise, But let's talk about it anyways.

510
00:24:32,359 --> 00:24:35,200
Speaker 1: The slightly less short answer is it depends on what

511
00:24:35,240 --> 00:24:38,200
Speaker 1: you think is happening at the quantum level, mostly about

512
00:24:38,200 --> 00:24:40,320
Speaker 1: what happens when you try to measure energy.

513
00:24:40,640 --> 00:24:44,240
Speaker 3: What do you mean? So I guess, because it's quantum mechanics,

514
00:24:44,320 --> 00:24:47,159
Speaker 3: you have to measure things. That's very importing quantum mechanics.

515
00:24:47,160 --> 00:24:49,480
Speaker 3: So you're saying, we have to answer this question with

516
00:24:49,720 --> 00:24:50,600
Speaker 3: this idea in mind.

517
00:24:50,680 --> 00:24:53,440
Speaker 1: Yeah, exactly. So let's start off the easy case without

518
00:24:53,480 --> 00:24:56,280
Speaker 1: measurements and have a picture in our minds or what's happening.

519
00:24:56,359 --> 00:24:59,400
Speaker 1: You know, quantum mechanics tells us that there are probabilities

520
00:24:59,440 --> 00:25:01,960
Speaker 1: for various things to happen, and we can calculate those

521
00:25:02,000 --> 00:25:06,480
Speaker 1: probabilities using the rules of quantum mechanics, and those probabilities propagate.

522
00:25:06,800 --> 00:25:09,560
Speaker 1: You have two electrons heading towards each other, they might

523
00:25:09,600 --> 00:25:11,720
Speaker 1: scatter off each other and go that way, they might

524
00:25:11,760 --> 00:25:15,040
Speaker 1: pass right through each other. All those probabilities are sort

525
00:25:15,040 --> 00:25:18,600
Speaker 1: of live until somebody actually asks the question and makes

526
00:25:18,640 --> 00:25:21,680
Speaker 1: a measurement using a classical object and you know, tries

527
00:25:21,720 --> 00:25:23,879
Speaker 1: to take a picture of it. Until then sort of

528
00:25:24,000 --> 00:25:28,240
Speaker 1: have all the possibilities live. So that's quantum mechanics without measurement.

529
00:25:28,359 --> 00:25:30,720
Speaker 1: You know, that's what we're imagining is happening when we're

530
00:25:30,760 --> 00:25:33,879
Speaker 1: not looking. And in that scenario we can ask, well,

531
00:25:34,080 --> 00:25:38,040
Speaker 1: is energy conserved? Like when all those probabilities are slashing around,

532
00:25:38,160 --> 00:25:41,080
Speaker 1: the electrons are maybe bouncing off each other and maybe

533
00:25:41,119 --> 00:25:44,840
Speaker 1: not is energy conserved there? And already we kind of

534
00:25:44,920 --> 00:25:47,560
Speaker 1: run into trouble because we don't really know how to

535
00:25:47,720 --> 00:25:51,600
Speaker 1: define energy here. Like, what if you have a quantum

536
00:25:51,680 --> 00:25:54,560
Speaker 1: system and has a few different possible states, a low

537
00:25:54,680 --> 00:25:56,919
Speaker 1: energy state and a high energy state. How do you

538
00:25:57,000 --> 00:25:59,920
Speaker 1: define the energy of it? Is it like the way

539
00:26:00,280 --> 00:26:03,919
Speaker 1: average of the probabilities of the various states? Is it

540
00:26:04,080 --> 00:26:06,840
Speaker 1: something else. I've had conversations with a bunch of physicists

541
00:26:06,840 --> 00:26:09,040
Speaker 1: this week to try to sort out what people think

542
00:26:09,160 --> 00:26:11,760
Speaker 1: energy is, and some people say, you can't define energy

543
00:26:11,760 --> 00:26:14,280
Speaker 1: in that context, and other people say, no, it's definitely

544
00:26:14,280 --> 00:26:17,320
Speaker 1: the weighted average of the various probabilities.

545
00:26:16,720 --> 00:26:18,639
Speaker 3: Right, I think, meaning maybe for people who are not

546
00:26:18,760 --> 00:26:22,119
Speaker 3: super familiar with quantum mechanics. So in quantum mechanics, particles

547
00:26:22,119 --> 00:26:24,520
Speaker 3: and things like that aren't just in one state, like

548
00:26:24,520 --> 00:26:27,280
Speaker 3: a baseball sitting on your table. It's like it's doing

549
00:26:27,359 --> 00:26:29,240
Speaker 3: multiple things at the same time. It's here, it's a

550
00:26:29,240 --> 00:26:31,879
Speaker 3: little bit there, it's moving in this direction a little bit,

551
00:26:31,880 --> 00:26:34,000
Speaker 3: but it's also has the probability to be moving in

552
00:26:34,040 --> 00:26:37,240
Speaker 3: this other direction. And so you're saying that maybe one

553
00:26:37,280 --> 00:26:39,840
Speaker 3: way to measure its energy, or to think about its

554
00:26:39,960 --> 00:26:42,520
Speaker 3: energy is like, if it has a fifty percent probability

555
00:26:42,520 --> 00:26:45,600
Speaker 3: of going this way, then you take that energy and

556
00:26:45,680 --> 00:26:48,560
Speaker 3: multiply by a half. And if it has a certain

557
00:26:48,600 --> 00:26:51,240
Speaker 3: probility that it's moving this way with that velocity, like

558
00:26:51,280 --> 00:26:54,560
Speaker 3: a twenty five percent probability, then you maybe multiply that

559
00:26:54,720 --> 00:26:56,760
Speaker 3: energy by a quarter, and then you would add it

560
00:26:56,760 --> 00:26:58,480
Speaker 3: all up and maybe that would kind of give you

561
00:26:58,520 --> 00:27:00,679
Speaker 3: an average of it energy.

562
00:27:00,800 --> 00:27:03,120
Speaker 1: Yeah, exactly, Like if it has a fifty percent chance

563
00:27:03,119 --> 00:27:05,639
Speaker 1: of having twenty five jewels of energy and a fifty

564
00:27:05,640 --> 00:27:08,159
Speaker 1: percent chance of having seventy five jewels, then you say, well,

565
00:27:08,200 --> 00:27:10,080
Speaker 1: I'm going to average those two. I'm gonna say its

566
00:27:10,200 --> 00:27:13,720
Speaker 1: energy is fifty jewels because on average that's what it has.

567
00:27:13,840 --> 00:27:16,600
Speaker 1: And here allowing the particle to still have both probabilities

568
00:27:16,600 --> 00:27:18,840
Speaker 1: to say, oh, maybe it's in the lower energy state,

569
00:27:18,920 --> 00:27:20,359
Speaker 1: maybe it's in the higher energy state.

570
00:27:20,600 --> 00:27:23,240
Speaker 3: Right, it's in a superposition, it's with a life and dead.

571
00:27:23,760 --> 00:27:25,560
Speaker 3: Then you said, some of your physicist friends said, you

572
00:27:25,600 --> 00:27:27,800
Speaker 3: can't do that, like that's not even that doesn't make sense.

573
00:27:27,920 --> 00:27:30,040
Speaker 1: Yeah, And they say, you can't do that because you

574
00:27:30,080 --> 00:27:32,800
Speaker 1: can't measure that, right, you never measure the fifty Like

575
00:27:32,840 --> 00:27:35,040
Speaker 1: if you went and asked the question, all right, we

576
00:27:35,119 --> 00:27:37,159
Speaker 1: have the particle in this state, go measure the energy.

577
00:27:37,240 --> 00:27:39,920
Speaker 1: You're gonna get twenty five or you're gonna get seventy five.

578
00:27:39,960 --> 00:27:42,200
Speaker 1: You're never going to get the average. It's like saying

579
00:27:42,359 --> 00:27:44,800
Speaker 1: the average number of children in the US is two

580
00:27:44,880 --> 00:27:48,080
Speaker 1: point four, but nobody actually has two point four children, right,

581
00:27:48,600 --> 00:27:50,320
Speaker 1: and so in the same way, you'll never see this

582
00:27:50,440 --> 00:27:52,840
Speaker 1: particle have that energy. So in what sense is that

583
00:27:52,880 --> 00:27:55,600
Speaker 1: the energy of the particle? That's sort of the complaint.

584
00:27:55,680 --> 00:27:58,000
Speaker 3: That's kind of a fundamental problem with quantum mechanics. Like

585
00:27:58,080 --> 00:28:00,399
Speaker 3: it's you know, the cat is alive and dead. Obviously

586
00:28:00,480 --> 00:28:03,080
Speaker 3: the cat can't be alive if you see the cat.

587
00:28:03,160 --> 00:28:05,919
Speaker 3: It can't be both. But in a quantum sense, it

588
00:28:06,000 --> 00:28:06,359
Speaker 3: is both.

589
00:28:06,520 --> 00:28:08,760
Speaker 1: In a quantum sense, it is both. In quantum sense,

590
00:28:08,760 --> 00:28:10,920
Speaker 1: we need a new idea for what these things mean,

591
00:28:11,400 --> 00:28:14,320
Speaker 1: Like what does position mean in a quantum sense, Well,

592
00:28:14,359 --> 00:28:16,560
Speaker 1: you know, for a particle that you haven't measured, it's

593
00:28:16,600 --> 00:28:19,760
Speaker 1: not really well defined. There's only a probability where is

594
00:28:19,800 --> 00:28:23,720
Speaker 1: the particle Actually, well, it's not anywhere. Actually, So these

595
00:28:23,800 --> 00:28:26,640
Speaker 1: concepts that are so important to us at the macroscopic

596
00:28:26,720 --> 00:28:28,960
Speaker 1: scale have to take different meanings. We have to do

597
00:28:29,040 --> 00:28:33,040
Speaker 1: this like philosophical extrapolation, and this is a problem with energy.

598
00:28:33,080 --> 00:28:35,320
Speaker 1: For example, say we have the particle and has two

599
00:28:35,359 --> 00:28:38,200
Speaker 1: different possibilities, the twenty five jewel and the seventy five jewel.

600
00:28:38,280 --> 00:28:39,760
Speaker 1: Then you go and you measure and it turns out

601
00:28:39,760 --> 00:28:42,320
Speaker 1: it has seventy five jewels. Well, if a minute ago

602
00:28:42,400 --> 00:28:44,560
Speaker 1: you said it had fifty jewels because that was the average.

603
00:28:44,720 --> 00:28:46,320
Speaker 1: Now you've measured it and you said you have seventy

604
00:28:46,320 --> 00:28:49,120
Speaker 1: five jewels. Where did that twenty five jewels come from?

605
00:28:49,280 --> 00:28:49,440
Speaker 3: Right?

606
00:28:49,480 --> 00:28:52,240
Speaker 1: And so boom right there, you have a violation of

607
00:28:52,240 --> 00:28:56,040
Speaker 1: conservation of energy. If that's how you define energy before

608
00:28:56,080 --> 00:28:56,640
Speaker 1: you measure it.

609
00:28:56,960 --> 00:28:59,080
Speaker 3: Wait, say it again. It is energy suddenly appear.

610
00:28:59,280 --> 00:29:00,840
Speaker 1: So if you start out the particle we were just

611
00:29:00,880 --> 00:29:03,080
Speaker 1: talking about, it has a fifty percent chance of having

612
00:29:03,080 --> 00:29:05,360
Speaker 1: twenty five jewels and a fifty percent chance of having

613
00:29:05,360 --> 00:29:08,120
Speaker 1: seventy five jewels. So we say, okay, we define the

614
00:29:08,240 --> 00:29:10,840
Speaker 1: energy of it to be fifty jewels because that's the average.

615
00:29:10,920 --> 00:29:12,800
Speaker 1: Now you go and you measure it, and you measure

616
00:29:12,800 --> 00:29:15,120
Speaker 1: it to have seventy five jewels for example, Then according

617
00:29:15,160 --> 00:29:17,760
Speaker 1: to our definition of energy, it's gone from having fifty

618
00:29:17,880 --> 00:29:20,920
Speaker 1: jewels to having seventy five jewels, and so where did

619
00:29:20,920 --> 00:29:22,000
Speaker 1: that energy come from?

620
00:29:22,080 --> 00:29:24,440
Speaker 3: It didn't come from anywhere, it just said before it

621
00:29:24,480 --> 00:29:26,680
Speaker 3: was a guess about what its energy was. It was

622
00:29:26,800 --> 00:29:29,520
Speaker 3: kind of like the expectations of it or the average

623
00:29:29,560 --> 00:29:31,840
Speaker 3: of what we think its energy was. But then in

624
00:29:31,960 --> 00:29:35,120
Speaker 3: the second instance, is what we measured its energy. So

625
00:29:35,160 --> 00:29:37,080
Speaker 3: they shouldn't be a surprise if it's more or less,

626
00:29:37,160 --> 00:29:37,640
Speaker 3: should it?

627
00:29:37,760 --> 00:29:40,040
Speaker 1: So you're saying, those are really two different things. One

628
00:29:40,120 --> 00:29:42,400
Speaker 1: is an actual energy because you've measured it. The other

629
00:29:42,520 --> 00:29:45,480
Speaker 1: is just some estimation of what we might measure, but

630
00:29:45,560 --> 00:29:46,680
Speaker 1: not really the energy.

631
00:29:46,880 --> 00:29:49,880
Speaker 3: Well, and it is in the quantum sense right like

632
00:29:49,960 --> 00:29:52,520
Speaker 3: it's alive and it's dead before I look at the

633
00:29:52,520 --> 00:29:54,520
Speaker 3: cat in the box and then I wanted to open

634
00:29:54,520 --> 00:29:56,240
Speaker 3: the box. It's alive with it. It's not like the

635
00:29:57,240 --> 00:29:59,040
Speaker 3: cat suddenly came back to life.

636
00:29:59,160 --> 00:30:00,920
Speaker 1: And I think this comes down to a question of

637
00:30:01,000 --> 00:30:04,080
Speaker 1: like interpretation, You know, what is really happening there? It

638
00:30:04,120 --> 00:30:07,400
Speaker 1: does the particle secretly already have seventy five jewels and

639
00:30:07,440 --> 00:30:09,800
Speaker 1: now we're measuring it and discovering it. You know, is

640
00:30:09,840 --> 00:30:12,760
Speaker 1: the uncertainty there or reflection of our lack of knowledge

641
00:30:13,080 --> 00:30:16,000
Speaker 1: about something that's actually already determined or something that really

642
00:30:16,080 --> 00:30:20,080
Speaker 1: isn't determined until we measure it. The particle really is

643
00:30:20,120 --> 00:30:22,320
Speaker 1: in a superposition of those two states. If it really

644
00:30:22,440 --> 00:30:24,880
Speaker 1: isn't determined until we measure it, then we do have

645
00:30:24,920 --> 00:30:26,800
Speaker 1: to kind of ask, like, where does the energy come

646
00:30:26,800 --> 00:30:29,480
Speaker 1: from when the universe decides to make that seventy five

647
00:30:29,560 --> 00:30:31,960
Speaker 1: jewel particle instead of the twenty five jewel particle.

648
00:30:32,160 --> 00:30:33,800
Speaker 3: Well, I guess in the same way that you can

649
00:30:33,840 --> 00:30:36,560
Speaker 3: ask if you find that the cat is alive, how

650
00:30:36,560 --> 00:30:38,440
Speaker 3: did the cat come alive? It was if it was

651
00:30:38,480 --> 00:30:40,520
Speaker 3: alive and dead before you open the box.

652
00:30:40,360 --> 00:30:42,200
Speaker 1: Right, But the difference between the two states of the

653
00:30:42,200 --> 00:30:45,280
Speaker 1: cat doesn't violate the conservation of energy, which we thought

654
00:30:45,400 --> 00:30:48,120
Speaker 1: was maybe a fundamental rule in the universe. That violates

655
00:30:48,120 --> 00:30:50,760
Speaker 1: the conservation of the number of dead cats, which nobody

656
00:30:50,760 --> 00:30:52,120
Speaker 1: really thinks it's a.

657
00:30:52,040 --> 00:30:55,880
Speaker 3: Conservation I hope not well or well, And this says

658
00:30:55,920 --> 00:30:57,880
Speaker 3: that we think that it's impossible for a cat to

659
00:30:57,880 --> 00:30:59,320
Speaker 3: go from being dead to being alive.

660
00:30:59,480 --> 00:31:01,160
Speaker 1: Right, I think if we're going to make the analogy

661
00:31:01,200 --> 00:31:03,400
Speaker 1: to the shorten your cat experiment, and then you want

662
00:31:03,400 --> 00:31:06,440
Speaker 1: to ask the question, is the cat alive before it's measured,

663
00:31:06,480 --> 00:31:07,880
Speaker 1: And the answer I think a lot of people would

664
00:31:07,880 --> 00:31:09,760
Speaker 1: give is it's neither alive nor dead. It has the

665
00:31:09,800 --> 00:31:13,640
Speaker 1: probability of being both. And then to extrapolate that philosophically

666
00:31:13,680 --> 00:31:16,560
Speaker 1: back to our particle, you'd say, well, the particle doesn't

667
00:31:16,600 --> 00:31:18,720
Speaker 1: really have twenty five or seventy five jewels, It just

668
00:31:18,800 --> 00:31:21,040
Speaker 1: has a probability of being both. And energy is not

669
00:31:21,320 --> 00:31:24,120
Speaker 1: really well defined. So I think one answer there is

670
00:31:24,160 --> 00:31:27,120
Speaker 1: to say, well, energy is not really defined without measurements,

671
00:31:27,400 --> 00:31:29,920
Speaker 1: so you can't answer this question, and the others to say, no,

672
00:31:30,040 --> 00:31:32,600
Speaker 1: that's the definition of energy, and there is violation of

673
00:31:32,640 --> 00:31:34,880
Speaker 1: conservation of energy, So you either have to give up

674
00:31:35,040 --> 00:31:38,479
Speaker 1: an understanding of what energy means for quantum particles or

675
00:31:38,520 --> 00:31:40,520
Speaker 1: you have to give up energy conservation.

676
00:31:40,920 --> 00:31:43,719
Speaker 3: All right, So it seems like the moment you measure

677
00:31:43,720 --> 00:31:47,280
Speaker 3: a quantum particle is super important because it's so fuzzy

678
00:31:47,320 --> 00:31:49,920
Speaker 3: before you measure it, and it's so crisp after you

679
00:31:50,000 --> 00:31:52,240
Speaker 3: measure it, and so you kind of fall into a

680
00:31:52,280 --> 00:31:54,640
Speaker 3: trap to try to compare the energy before that moment

681
00:31:54,720 --> 00:31:57,720
Speaker 3: and after that moment, you know, you could interpret it

682
00:31:57,760 --> 00:32:00,600
Speaker 3: as saying that energy is not conserved or could interpret

683
00:32:00,640 --> 00:32:04,680
Speaker 3: it saying, well, you know, there's no definition of energy

684
00:32:04,680 --> 00:32:07,160
Speaker 3: before you measure it, and so therefore don't even worry

685
00:32:07,160 --> 00:32:10,080
Speaker 3: about energy classivation exactly.

686
00:32:10,200 --> 00:32:13,640
Speaker 1: But there's really important loophole that we're overlooking here, and

687
00:32:13,680 --> 00:32:17,960
Speaker 1: that's the measurement itself. Some people argue that energy isn't conserved,

688
00:32:18,160 --> 00:32:21,720
Speaker 1: that this extra energy must come from the measurement, that

689
00:32:21,760 --> 00:32:24,520
Speaker 1: we're only violating conservation of energy because we're not including

690
00:32:24,520 --> 00:32:27,480
Speaker 1: the full system. Right. Energy is only conserved inside a

691
00:32:27,480 --> 00:32:30,520
Speaker 1: closed system where you don't have energy transfer anyway. Right,

692
00:32:30,600 --> 00:32:33,400
Speaker 1: Like energy is not conserved for a battery. As you

693
00:32:33,560 --> 00:32:35,840
Speaker 1: use it, it's energy is decreasing, but if you include

694
00:32:35,840 --> 00:32:38,680
Speaker 1: where that energy is going, usually it is concerned. So

695
00:32:38,880 --> 00:32:41,840
Speaker 1: some people argue, ah, what about the measurement. In order

696
00:32:41,880 --> 00:32:43,640
Speaker 1: to measure something, you have to like poke it, you

697
00:32:43,640 --> 00:32:46,240
Speaker 1: have to interact with it. Maybe you're adding that energy

698
00:32:46,360 --> 00:32:49,400
Speaker 1: when you're making that measurement and things do balance out

699
00:32:49,440 --> 00:32:50,000
Speaker 1: in the end.

700
00:32:50,360 --> 00:32:53,240
Speaker 3: Wait what that was very confusing? Can you give me

701
00:32:53,280 --> 00:32:53,840
Speaker 3: an example.

702
00:32:54,040 --> 00:32:56,000
Speaker 1: So let's say you want to measure this particle and

703
00:32:56,040 --> 00:32:57,960
Speaker 1: you want to say it doesn't have seventy five jewels

704
00:32:58,040 --> 00:33:00,200
Speaker 1: or twenty five jewels, How do you measure things about

705
00:33:00,200 --> 00:33:02,880
Speaker 1: a quantum particle, you have to bounce another quantum particle

706
00:33:02,880 --> 00:33:05,840
Speaker 1: off of them. So shoot this electron with a photon,

707
00:33:06,320 --> 00:33:08,400
Speaker 1: then measure where that photon goes and use that to

708
00:33:08,440 --> 00:33:11,400
Speaker 1: detect what the energy of your particle was. Well, now

709
00:33:11,440 --> 00:33:13,760
Speaker 1: you're shooting your electron with a photon, which is going

710
00:33:13,840 --> 00:33:17,080
Speaker 1: to change its energy. And so people argue, when you're

711
00:33:17,120 --> 00:33:20,280
Speaker 1: doing this, the energy that gives that electron seventy five

712
00:33:20,360 --> 00:33:22,640
Speaker 1: jewels comes from that photon somehow.

713
00:33:22,760 --> 00:33:26,040
Speaker 3: But then wouldn't you measure that the overall energy went

714
00:33:26,120 --> 00:33:28,440
Speaker 3: down because you would measure the photon after it hits

715
00:33:28,440 --> 00:33:30,920
Speaker 3: the electron, and you would see that it was had

716
00:33:30,960 --> 00:33:32,160
Speaker 3: less energy exactly.

717
00:33:32,200 --> 00:33:33,959
Speaker 1: So this is the game people try to play in

718
00:33:34,080 --> 00:33:37,120
Speaker 1: order to recover conservation of energy for quantum mechanics. They say,

719
00:33:37,120 --> 00:33:39,719
Speaker 1: this argument is flawed because you're not taking into account

720
00:33:39,800 --> 00:33:42,640
Speaker 1: the energy of the measurement. So there's a whole cottage

721
00:33:42,680 --> 00:33:45,000
Speaker 1: industry and a bunch of paper. It's recently about whether

722
00:33:45,040 --> 00:33:47,760
Speaker 1: it's possible to recover it using the measurement or whether

723
00:33:47,800 --> 00:33:48,600
Speaker 1: that's a red herring.

724
00:33:48,720 --> 00:33:50,400
Speaker 3: Well, the whole thing could be a red herring, right,

725
00:33:50,440 --> 00:33:52,320
Speaker 3: Like it could be that it just doesn't make sense

726
00:33:52,320 --> 00:33:54,080
Speaker 3: to talk about energy before the measurement.

727
00:33:54,160 --> 00:33:56,560
Speaker 1: It could be and that actually depends also on your

728
00:33:56,560 --> 00:34:00,040
Speaker 1: interpretation of quantum mechanics. We're talking right now in the

729
00:34:00,040 --> 00:34:03,200
Speaker 1: Copenhagen interpretation, which has this whole idea that there's a

730
00:34:03,240 --> 00:34:05,920
Speaker 1: superposition and when you make a measurement it collapses to

731
00:34:05,960 --> 00:34:09,320
Speaker 1: one of those options. That's just one view of quantum mechanics,

732
00:34:09,800 --> 00:34:13,799
Speaker 1: and our argument about the energy non conservation depends on

733
00:34:13,880 --> 00:34:15,840
Speaker 1: that view. It turns out in other views of quantum

734
00:34:15,840 --> 00:34:17,640
Speaker 1: mechanics they tell a whole different story.

735
00:34:18,360 --> 00:34:20,719
Speaker 3: All right, well, let's get into what these other views

736
00:34:20,719 --> 00:34:24,799
Speaker 3: of quantum mechanics are and what they say about the

737
00:34:24,840 --> 00:34:27,920
Speaker 3: conservation of cat energy or not. So let's dig into that.

738
00:34:27,960 --> 00:34:43,319
Speaker 3: But first let's take another quick break. All Right, we're

739
00:34:43,360 --> 00:34:47,319
Speaker 3: talking about energy, whether it's conserved in the universe, is

740
00:34:47,320 --> 00:34:49,680
Speaker 3: it conserved at the quantum level? And I think we've

741
00:34:49,800 --> 00:34:55,400
Speaker 3: established that it's a minefield of confusion for everybody. Some

742
00:34:55,480 --> 00:34:57,439
Speaker 3: people might say, does it even make sense to talk

743
00:34:57,480 --> 00:35:01,799
Speaker 3: about energy before you measure something? And you know, it

744
00:35:01,800 --> 00:35:03,640
Speaker 3: doesn't make sense to talk about whether the cat is

745
00:35:03,680 --> 00:35:07,160
Speaker 3: alive or dead before you open the box. And some

746
00:35:07,239 --> 00:35:09,879
Speaker 3: people might say that it does kind of matter, right,

747
00:35:10,000 --> 00:35:12,320
Speaker 3: or that if you discovered the cat to be aliver

748
00:35:12,880 --> 00:35:14,800
Speaker 3: before or after, maybe you killed the cat when you

749
00:35:14,840 --> 00:35:17,040
Speaker 3: open the box. That's kind of what you're saying exactly.

750
00:35:17,440 --> 00:35:19,480
Speaker 1: And it's amazing to me that this is a topic

751
00:35:19,560 --> 00:35:22,520
Speaker 1: of recent discussion. This is not like something that Bore

752
00:35:22,600 --> 00:35:25,520
Speaker 1: and Heisenberg argued about and figured it out in nineteen

753
00:35:25,560 --> 00:35:29,040
Speaker 1: thirty seven their papers about this. Like last year, you know,

754
00:35:29,160 --> 00:35:33,400
Speaker 1: people are still debating what energy even means in quantum mechanics. Like,

755
00:35:33,480 --> 00:35:35,640
Speaker 1: sort this out, folks. You had it for one hundred years.

756
00:35:35,680 --> 00:35:37,719
Speaker 1: You think that would be enough time to figure out

757
00:35:37,760 --> 00:35:39,280
Speaker 1: basic stuff about quantum mechanics.

758
00:35:39,400 --> 00:35:41,759
Speaker 3: Yeah, can't you just run an experiment to figure this out?

759
00:35:41,800 --> 00:35:46,120
Speaker 3: Like if measuring an electron somehow adds energy to it

760
00:35:46,239 --> 00:35:48,960
Speaker 3: or creates energy, can't you just measure that cad you

761
00:35:49,000 --> 00:35:51,160
Speaker 3: just design an experiment where you should a photon at

762
00:35:51,160 --> 00:35:51,800
Speaker 3: an electron.

763
00:35:52,080 --> 00:35:54,600
Speaker 1: So people are trying to design experiments, and the crucial

764
00:35:54,640 --> 00:35:58,200
Speaker 1: thing is designing an experiment where you think the measurement

765
00:35:58,320 --> 00:36:01,800
Speaker 1: will not influence the energy of the system. That's the goal,

766
00:36:02,360 --> 00:36:04,400
Speaker 1: because then you can have an internal system and an

767
00:36:04,400 --> 00:36:06,719
Speaker 1: external system, and you can isolate it and say this

768
00:36:06,840 --> 00:36:08,360
Speaker 1: is the whole system. So you want to try to

769
00:36:08,400 --> 00:36:11,120
Speaker 1: separate your measuring device from the energy of the system.

770
00:36:11,280 --> 00:36:12,600
Speaker 3: Wait, wait, do you mean like they're trying to come

771
00:36:12,640 --> 00:36:14,560
Speaker 3: up with how to measure something without measuring it.

772
00:36:14,640 --> 00:36:17,480
Speaker 1: Well, they want to measure it without changing its energy,

773
00:36:17,600 --> 00:36:20,960
Speaker 1: so they want a energy independent measuring system.

774
00:36:21,080 --> 00:36:23,400
Speaker 3: But I guess, if you shoot a photon at an electron,

775
00:36:23,520 --> 00:36:25,879
Speaker 3: don't you know how much energy the photon had when

776
00:36:25,880 --> 00:36:28,640
Speaker 3: you shot it so that you can take it into

777
00:36:28,680 --> 00:36:31,000
Speaker 3: account later when it comes out? Like, why is this

778
00:36:31,040 --> 00:36:31,920
Speaker 3: problem so hard?

779
00:36:32,080 --> 00:36:34,680
Speaker 1: Well, every quantum object has an uncertainty to it, and

780
00:36:34,719 --> 00:36:36,680
Speaker 1: so you shoot a photon at it. You try to

781
00:36:36,719 --> 00:36:39,480
Speaker 1: generate photons with a specific energy, but those photons will

782
00:36:39,520 --> 00:36:42,080
Speaker 1: also have an uncertainty to them, and that uncertainty propagates

783
00:36:42,080 --> 00:36:44,080
Speaker 1: through your whole experiment. So what you want to try

784
00:36:44,080 --> 00:36:46,520
Speaker 1: to do is set up a scenario where the uncertainty

785
00:36:46,680 --> 00:36:50,720
Speaker 1: you're adding by your measurement is smaller than the difference

786
00:36:50,719 --> 00:36:52,640
Speaker 1: in the energy between the two states of the thing

787
00:36:52,719 --> 00:36:54,920
Speaker 1: that you're measuring. So you want to try to use

788
00:36:55,160 --> 00:36:58,040
Speaker 1: something really low energy to measure a really big difference.

789
00:36:58,320 --> 00:36:59,879
Speaker 3: I guess it's kind of like you know, you're trying

790
00:36:59,880 --> 00:37:01,640
Speaker 3: to figure out if the cat is alive or dead

791
00:37:01,640 --> 00:37:03,719
Speaker 3: in the box, and you're sending it in a cat

792
00:37:03,800 --> 00:37:05,680
Speaker 3: to do it. But it turns out that the scientist

793
00:37:05,760 --> 00:37:08,120
Speaker 3: cat is also a quantum object, so it could also

794
00:37:08,160 --> 00:37:10,439
Speaker 3: be a live or dead, in which case you don't

795
00:37:10,440 --> 00:37:13,480
Speaker 3: really know the scientist cat is killing the other cat exactly.

796
00:37:13,520 --> 00:37:14,879
Speaker 1: So what you want to do is try to send

797
00:37:14,920 --> 00:37:18,280
Speaker 1: in like a tiny miniature kitten that you can argue

798
00:37:18,400 --> 00:37:20,840
Speaker 1: is going to not influence whether your cat is alive

799
00:37:20,960 --> 00:37:21,680
Speaker 1: or dead as much.

800
00:37:21,600 --> 00:37:24,120
Speaker 3: As possible, or that you know for sure if it's

801
00:37:24,160 --> 00:37:25,000
Speaker 3: alive or dead.

802
00:37:25,040 --> 00:37:27,600
Speaker 1: Or the uncertainty on it is smaller than the uncertainty

803
00:37:27,640 --> 00:37:29,759
Speaker 1: on the thing you're trying to measure. So people come

804
00:37:29,800 --> 00:37:32,560
Speaker 1: up with these crazy clever experiments where you try to

805
00:37:32,640 --> 00:37:35,919
Speaker 1: use really low energy device to measure a very high

806
00:37:36,080 --> 00:37:39,359
Speaker 1: energy difference in the possible states of the object. So

807
00:37:39,440 --> 00:37:42,520
Speaker 1: the thing you're measuring is not influencing the state enough

808
00:37:42,560 --> 00:37:43,560
Speaker 1: to change the answer.

809
00:37:44,120 --> 00:37:45,879
Speaker 3: Oh I see, yeah, Like you said, like you want

810
00:37:45,920 --> 00:37:49,840
Speaker 3: to send in a scientist kitty whose state whether the

811
00:37:49,880 --> 00:37:51,400
Speaker 3: kitty is a live or dead is not really going

812
00:37:51,480 --> 00:37:54,080
Speaker 3: to influence whether the big cat is a live or

813
00:37:54,080 --> 00:37:56,279
Speaker 3: dead exactly.

814
00:37:56,960 --> 00:37:58,839
Speaker 1: And so there's these folks that come up with its

815
00:37:58,880 --> 00:38:01,759
Speaker 1: really clever experience where you take a box and you

816
00:38:01,800 --> 00:38:04,920
Speaker 1: put low energy photons inside of it, and under some

817
00:38:05,160 --> 00:38:09,520
Speaker 1: almost magic like wave mechanics mathematics, there's a place in

818
00:38:09,520 --> 00:38:11,840
Speaker 1: the box where the photon wavelengths add up in a

819
00:38:11,880 --> 00:38:14,640
Speaker 1: special way to wiggle at a really high energy. So

820
00:38:14,719 --> 00:38:16,920
Speaker 1: waves can add up and they can cancel each other out.

821
00:38:17,000 --> 00:38:20,319
Speaker 1: This is constructive and destructive interference, where it turns out

822
00:38:20,320 --> 00:38:22,799
Speaker 1: if you put a bunch of low energy photons into

823
00:38:22,800 --> 00:38:25,200
Speaker 1: a box, there's one portion of the box where they're

824
00:38:25,239 --> 00:38:28,680
Speaker 1: wiggling really really fast where all those photons added up

825
00:38:29,000 --> 00:38:31,920
Speaker 1: kind of make a higher energy photon than the sum

826
00:38:31,960 --> 00:38:34,440
Speaker 1: of all the energy of the photons you put in.

827
00:38:35,000 --> 00:38:36,520
Speaker 1: And they came up with this way to try to

828
00:38:36,560 --> 00:38:39,400
Speaker 1: reflect that one part of the photon out of the

829
00:38:39,400 --> 00:38:42,160
Speaker 1: box by slipping a mirror in really quick. And so

830
00:38:42,160 --> 00:38:44,560
Speaker 1: it's sort of like putting a few low energy photons

831
00:38:44,560 --> 00:38:46,640
Speaker 1: in a box and then getting out a really high

832
00:38:46,760 --> 00:38:49,919
Speaker 1: energy photon. So this is the experiment they propose would

833
00:38:50,000 --> 00:38:53,480
Speaker 1: prove violation or conservation of energy and quantum mechanics. But

834
00:38:53,520 --> 00:38:56,080
Speaker 1: there's a lot of controversy about what this experiment might

835
00:38:56,160 --> 00:38:57,799
Speaker 1: mean and whether you could actually do it.

836
00:38:58,160 --> 00:39:01,080
Speaker 3: Oh, I see, because if you measure a really big

837
00:39:01,120 --> 00:39:03,480
Speaker 3: photon coming out of this corner of the box, you

838
00:39:03,520 --> 00:39:05,080
Speaker 3: have to wonder where that energy came from.

839
00:39:05,160 --> 00:39:07,960
Speaker 1: Yeah, how did the universe make this high energy photon

840
00:39:08,239 --> 00:39:10,719
Speaker 1: out of just a few very low energy photons? Where

841
00:39:10,760 --> 00:39:12,520
Speaker 1: did it come from? Just like the example we were

842
00:39:12,520 --> 00:39:15,520
Speaker 1: talking about before, how did the particle get seventy five

843
00:39:15,600 --> 00:39:18,160
Speaker 1: GeV when the expected value of the energy was fifty

844
00:39:18,200 --> 00:39:20,600
Speaker 1: Where did that energy come from? And you can only

845
00:39:20,600 --> 00:39:23,000
Speaker 1: really ask that question where did it come from if

846
00:39:23,040 --> 00:39:25,719
Speaker 1: you believe it should come from somewhere, which implies that

847
00:39:25,760 --> 00:39:27,960
Speaker 1: it's conserved, that it has to come from somewhere, that

848
00:39:28,000 --> 00:39:30,799
Speaker 1: it's like flows around in it's a limited amount. But

849
00:39:30,800 --> 00:39:32,719
Speaker 1: if energy is not conserved, it can just like go

850
00:39:32,800 --> 00:39:34,480
Speaker 1: up or down, like the number of dead cats in

851
00:39:34,520 --> 00:39:36,360
Speaker 1: the universe. Then that's not really a problem.

852
00:39:36,400 --> 00:39:38,040
Speaker 3: But couldn't you just say that the energy of that

853
00:39:38,200 --> 00:39:40,719
Speaker 3: right photon in the corner came from the little photons

854
00:39:41,120 --> 00:39:43,320
Speaker 3: or would it come out with a much bigger energy

855
00:39:43,360 --> 00:39:46,520
Speaker 3: than the if you add up the little smaller photons.

856
00:39:46,600 --> 00:39:49,040
Speaker 1: Yeah, in this case, the energy is much bigger than

857
00:39:49,080 --> 00:39:51,200
Speaker 1: the sum of the energies of all the photons you

858
00:39:51,239 --> 00:39:53,520
Speaker 1: put in, So you can't explain it by just like

859
00:39:53,560 --> 00:39:56,720
Speaker 1: having added up those photons. It's a really cool experiment.

860
00:39:56,760 --> 00:39:59,520
Speaker 1: It's called super oscillation if you want to check out

861
00:39:59,520 --> 00:40:00,520
Speaker 1: more details about it.

862
00:40:00,680 --> 00:40:02,680
Speaker 3: Well, but then you said that this is all just

863
00:40:02,960 --> 00:40:06,200
Speaker 3: base on one interpretation of quantum mechanics. What did the

864
00:40:06,239 --> 00:40:08,560
Speaker 3: other interpretations say or how can they help us?

865
00:40:08,719 --> 00:40:10,480
Speaker 1: Yeah, because a big part of the issue is what

866
00:40:10,560 --> 00:40:12,799
Speaker 1: happens when you make a measurement. Right if you go

867
00:40:12,880 --> 00:40:15,680
Speaker 1: from a state that has on average fifty jewels of energy,

868
00:40:15,880 --> 00:40:17,560
Speaker 1: then you make a measurement, how do you end up

869
00:40:17,560 --> 00:40:19,680
Speaker 1: in one of those states? And where does that energy

870
00:40:19,719 --> 00:40:22,360
Speaker 1: come from? And other interpretations of quantum mechanics tell a

871
00:40:22,520 --> 00:40:25,319
Speaker 1: very different story about what's happening there. For example, the

872
00:40:25,360 --> 00:40:28,560
Speaker 1: Many Worlds or ever Ready in quantum mechanics says that

873
00:40:28,600 --> 00:40:31,359
Speaker 1: there is no collapse of the wave function. That if

874
00:40:31,360 --> 00:40:34,440
Speaker 1: you have a superposition of two possibilities that has alive

875
00:40:34,560 --> 00:40:37,319
Speaker 1: or dead, the particle has twenty five or seventy five

876
00:40:37,400 --> 00:40:40,000
Speaker 1: jewels of energy, that when you make a measurement, the

877
00:40:40,120 --> 00:40:42,440
Speaker 1: universe just branches and now there's one branch that has

878
00:40:42,480 --> 00:40:44,600
Speaker 1: one option and another branch that has the other option.

879
00:40:44,840 --> 00:40:47,279
Speaker 1: And so in that sense, if you're like averaging over

880
00:40:47,320 --> 00:40:50,640
Speaker 1: the branches, nothing has really changed. You know, the total

881
00:40:50,760 --> 00:40:53,839
Speaker 1: energy in the universe hasn't changed. One individual branch might

882
00:40:53,880 --> 00:40:56,880
Speaker 1: see seventy five jewels, so they might think they're seeing

883
00:40:57,000 --> 00:41:00,480
Speaker 1: violation of conservation of energy. But averaged over all the branches,

884
00:41:00,520 --> 00:41:03,080
Speaker 1: including the ones that don't see, nothing has really changed.

885
00:41:03,120 --> 00:41:05,440
Speaker 1: There's still just a distribution of different energies.

886
00:41:05,719 --> 00:41:09,000
Speaker 3: I feel like you just skipped over a humongas concept

887
00:41:09,160 --> 00:41:11,040
Speaker 3: which is just throwing the multiverse.

888
00:41:11,200 --> 00:41:13,359
Speaker 1: Yes, exactly, in the multiverse.

889
00:41:12,800 --> 00:41:16,520
Speaker 3: Quantum multiverse. So you're saying, like, one way to interpret

890
00:41:16,600 --> 00:41:19,480
Speaker 3: quantum mechanics is that things don't collapse. You know, if

891
00:41:19,480 --> 00:41:21,319
Speaker 3: something if the cat is alive and dead, it means

892
00:41:21,320 --> 00:41:23,560
Speaker 3: that there's a universe where the cat is alive and

893
00:41:23,640 --> 00:41:27,200
Speaker 3: there's a universe where it's dead, and so overall energy

894
00:41:27,239 --> 00:41:28,719
Speaker 3: is still conserved. That's kind of the idea.

895
00:41:28,960 --> 00:41:33,960
Speaker 1: Yeah, energy is just unevenly distributed among those quantum multiverses.

896
00:41:34,320 --> 00:41:37,000
Speaker 1: One of them gets more, another one gets less. Overall

897
00:41:37,080 --> 00:41:40,200
Speaker 1: it all balances out across the multiverse. But in an

898
00:41:40,239 --> 00:41:44,040
Speaker 1: individual universe, an observer does see a violation of energy.

899
00:41:44,320 --> 00:41:46,719
Speaker 1: So that's a pretty different story than what's being told

900
00:41:46,719 --> 00:41:47,719
Speaker 1: by the Copenhagen group.

901
00:41:47,800 --> 00:41:49,360
Speaker 3: Let me see if I get this, so, like, I

902
00:41:49,400 --> 00:41:51,520
Speaker 3: have the cat in the box, and I open the

903
00:41:51,560 --> 00:41:53,799
Speaker 3: box and I find that the cat is alive, and

904
00:41:53,840 --> 00:41:55,680
Speaker 3: I think, oh my god, this is a violation of

905
00:41:55,840 --> 00:41:59,200
Speaker 3: cat aliveness in the universe because before the cat was

906
00:41:59,239 --> 00:42:01,520
Speaker 3: only fifty percent and now it's fully alive.

907
00:42:01,680 --> 00:42:02,080
Speaker 1: Sure.

908
00:42:02,880 --> 00:42:06,240
Speaker 3: Yeah, And you're saying, if you think that the actually

909
00:42:06,280 --> 00:42:09,680
Speaker 3: there's a multiverse, is a quantum multiverse, then there's no

910
00:42:09,760 --> 00:42:12,640
Speaker 3: real violation because if you consider my universe where the

911
00:42:12,680 --> 00:42:15,279
Speaker 3: cat is alive and your universe where the cat is dead,

912
00:42:15,840 --> 00:42:18,000
Speaker 3: then it makes sense for me to see that the

913
00:42:18,040 --> 00:42:19,640
Speaker 3: cat is alive, and it makes sense for you to

914
00:42:19,680 --> 00:42:21,960
Speaker 3: see that the cat is dead. There's no violation here.

915
00:42:21,840 --> 00:42:24,840
Speaker 1: Yeah, because across the quantum multiverse it's still fifty percent

916
00:42:24,880 --> 00:42:26,360
Speaker 1: alive and fifty percent dead.

917
00:42:26,480 --> 00:42:30,200
Speaker 3: But in the single universe version of quantum mechanics, the

918
00:42:30,440 --> 00:42:33,520
Speaker 3: cat aliveness went up from one half to one if

919
00:42:33,560 --> 00:42:34,520
Speaker 3: I see that the cat.

920
00:42:34,360 --> 00:42:38,360
Speaker 1: Is alive exactly. So in the collapse theory where measuring

921
00:42:38,400 --> 00:42:41,160
Speaker 1: it forces the universe to choose one of these branches

922
00:42:41,200 --> 00:42:44,480
Speaker 1: instead of maintaining all of them, then somehow the number

923
00:42:44,520 --> 00:42:46,600
Speaker 1: of live cats in the universe goes up from half

924
00:42:46,640 --> 00:42:49,840
Speaker 1: to one, violating the well known principle of the number

925
00:42:49,840 --> 00:42:51,360
Speaker 1: of living cats in the universe.

926
00:42:51,800 --> 00:42:54,680
Speaker 3: Yeah, or people in swimming pools, which I'm going to

927
00:42:54,840 --> 00:43:00,000
Speaker 3: wait for that paper from me. Okay, hold your breas, yeah,

928
00:43:00,120 --> 00:43:02,560
Speaker 3: to under the pool. Yes, Okay. So then I feel

929
00:43:02,600 --> 00:43:06,920
Speaker 3: like maybe I wonder, like you're saying, if we require

930
00:43:07,480 --> 00:43:10,400
Speaker 3: energy to be conserved in the universe for real, for sure,

931
00:43:11,280 --> 00:43:14,960
Speaker 3: then maybe I wonder if that's proof that the multiverse exists,

932
00:43:15,239 --> 00:43:17,040
Speaker 3: because that's the only way that this is going to work.

933
00:43:17,120 --> 00:43:19,799
Speaker 1: Right, That's a cool perspective I hadn't thought of. Yeah,

934
00:43:19,840 --> 00:43:23,640
Speaker 1: I suppose if you define energy that way as across

935
00:43:23,640 --> 00:43:29,000
Speaker 1: the multiverse and you insist that it's conserved, then Copenhagen

936
00:43:29,040 --> 00:43:31,680
Speaker 1: interpretation of quantum mechanics does violate that. But that's not

937
00:43:31,719 --> 00:43:34,319
Speaker 1: something you can test, right. You can never access these

938
00:43:34,320 --> 00:43:37,439
Speaker 1: other branches of the multiverse. You can never know if

939
00:43:37,440 --> 00:43:40,320
Speaker 1: they exist, and if other people are measuring other things,

940
00:43:40,360 --> 00:43:42,680
Speaker 1: then you can only ever access our branch.

941
00:43:42,920 --> 00:43:46,319
Speaker 3: We think, maybe, right, maybe you can this. I think

942
00:43:46,320 --> 00:43:48,920
Speaker 3: we've talked about this before and in our books, like

943
00:43:49,239 --> 00:43:52,040
Speaker 3: you could maybe discover something about the mathematics of our

944
00:43:52,120 --> 00:43:55,520
Speaker 3: universe that maybe points to the necessity of other universes.

945
00:43:55,560 --> 00:43:58,359
Speaker 1: No, we definitely argue in our book that it might

946
00:43:58,400 --> 00:44:01,840
Speaker 1: be that the only consistent explanation of the universe is

947
00:44:01,880 --> 00:44:05,680
Speaker 1: the multiverse. So you can prove the multiverse exists without

948
00:44:05,800 --> 00:44:08,480
Speaker 1: ever experimentally verifying it, though that takes a lot of

949
00:44:08,520 --> 00:44:11,399
Speaker 1: confidence to say that there's no other explanation out there.

950
00:44:11,480 --> 00:44:13,960
Speaker 3: That would take a high amount of confidence, not a

951
00:44:14,040 --> 00:44:15,200
Speaker 3: nuclear amount of confidence.

952
00:44:15,239 --> 00:44:18,279
Speaker 1: So extrapolining that argument, if you can somehow prove that

953
00:44:18,360 --> 00:44:21,560
Speaker 1: a complete theory of the universe has to satisfy conservation

954
00:44:21,600 --> 00:44:24,120
Speaker 1: of energy at the quantum level, then yeah, that might

955
00:44:24,200 --> 00:44:26,960
Speaker 1: require the existence of the multiverse. But I don't know

956
00:44:26,960 --> 00:44:30,320
Speaker 1: how you would prove that requirement because energy is not

957
00:44:30,440 --> 00:44:32,920
Speaker 1: even necessarily well defined at the quantum level.

958
00:44:33,160 --> 00:44:34,960
Speaker 3: I wonder if that means that some of the other

959
00:44:35,080 --> 00:44:38,080
Speaker 3: places that we've seen energy conservation being violated, like the

960
00:44:38,120 --> 00:44:40,560
Speaker 3: expansion of the universe. I wonder if that can mean that,

961
00:44:41,080 --> 00:44:43,959
Speaker 3: you know, as our universe expands and gains energy, maybe

962
00:44:43,960 --> 00:44:48,160
Speaker 3: there's another universe out there losing energy and being compressed.

963
00:44:48,239 --> 00:44:49,680
Speaker 1: It's a great question and one of the reasons I

964
00:44:49,760 --> 00:44:52,840
Speaker 1: really like this question zooming down to the microscopic scale

965
00:44:52,880 --> 00:44:55,880
Speaker 1: and trying to understand what is conservation of energy there

966
00:44:56,160 --> 00:44:58,160
Speaker 1: is because we're really interested in what it means at

967
00:44:58,160 --> 00:45:00,560
Speaker 1: our scale, Like where does energy come from? Why is

968
00:45:00,560 --> 00:45:03,040
Speaker 1: it conserved for us? Is it because it's required at

969
00:45:03,040 --> 00:45:05,920
Speaker 1: the quantum level, or is it because it emerges somehow?

970
00:45:06,320 --> 00:45:10,560
Speaker 1: And so yeah, maybe energy non conservation in general relativity

971
00:45:10,880 --> 00:45:15,080
Speaker 1: could eventually be derived from some deep quantum gravity, some

972
00:45:15,239 --> 00:45:17,680
Speaker 1: explanation of the nature of space time at the quantum

973
00:45:17,840 --> 00:45:21,160
Speaker 1: level that has these consequences at our scale or at

974
00:45:21,160 --> 00:45:23,400
Speaker 1: the scale of the whole universe. So that would be

975
00:45:23,440 --> 00:45:24,279
Speaker 1: really fascinating.

976
00:45:24,560 --> 00:45:26,759
Speaker 3: Yeah, or maybe vice versa, right, Like, if you prove

977
00:45:26,880 --> 00:45:30,239
Speaker 3: energy conservation at the grand level, it must might have

978
00:45:30,320 --> 00:45:33,080
Speaker 3: some consequences about you know, what we think is happening

979
00:45:33,160 --> 00:45:34,040
Speaker 3: at the quantum level.

980
00:45:34,080 --> 00:45:37,360
Speaker 1: It could be although sometimes conservation laws cannot be exact.

981
00:45:37,440 --> 00:45:39,800
Speaker 1: They can just emerge, so they don't have to always

982
00:45:39,840 --> 00:45:42,480
Speaker 1: hold true at the quantum level to hold true at

983
00:45:42,520 --> 00:45:44,440
Speaker 1: the classical level. But there are some things that are

984
00:45:44,480 --> 00:45:47,160
Speaker 1: truet the quantum level, Like we think conservation momentum is

985
00:45:47,280 --> 00:45:49,640
Speaker 1: rock solid at the quantum level, and the reason we

986
00:45:49,719 --> 00:45:52,520
Speaker 1: have it at our level is because everything is made

987
00:45:52,560 --> 00:45:55,840
Speaker 1: out of these quantum bits which follow these rules. So

988
00:45:55,880 --> 00:45:58,400
Speaker 1: we don't know basically whether conservation of energy is exact

989
00:45:58,600 --> 00:46:01,520
Speaker 1: the way conservation momentum is because it comes out of

990
00:46:01,520 --> 00:46:04,360
Speaker 1: the quantum level, or if it's something that emerges somehow

991
00:46:04,400 --> 00:46:06,080
Speaker 1: when you get classical physics.

992
00:46:06,400 --> 00:46:08,640
Speaker 3: I guess maybe your people in a pool experiment is

993
00:46:08,640 --> 00:46:10,160
Speaker 3: going to conclusively prove that.

994
00:46:10,200 --> 00:46:13,480
Speaker 1: Then give me one hundred years. It's going to take

995
00:46:13,520 --> 00:46:15,240
Speaker 1: a lot of data.

996
00:46:15,400 --> 00:46:17,120
Speaker 3: What do you Why do you need five years to

997
00:46:17,160 --> 00:46:17,480
Speaker 3: do this?

998
00:46:19,800 --> 00:46:22,200
Speaker 1: Oh man, because the I RB you know, you're doing

999
00:46:22,239 --> 00:46:25,319
Speaker 1: experiments on people. You got to sign the papers. It's

1000
00:46:25,360 --> 00:46:25,839
Speaker 1: the whole thing.

1001
00:46:27,120 --> 00:46:29,120
Speaker 3: I see. Yeah, And then there's a pool, so the

1002
00:46:29,160 --> 00:46:32,080
Speaker 3: forms get wet. It's all a big mess. What does

1003
00:46:32,120 --> 00:46:35,239
Speaker 3: this have more implications for our understanding of quantum mechanics

1004
00:46:35,360 --> 00:46:38,160
Speaker 3: or understanding of energy conservation in the universe.

1005
00:46:38,400 --> 00:46:41,000
Speaker 1: I think it has consequences for our understanding of what

1006
00:46:41,160 --> 00:46:43,960
Speaker 1: energy is. As we drill down to see what the

1007
00:46:44,040 --> 00:46:47,319
Speaker 1: universe really is like at the microscopic scale, we learn

1008
00:46:47,360 --> 00:46:50,600
Speaker 1: about things that turn out to just be features of

1009
00:46:50,640 --> 00:46:53,520
Speaker 1: our existence. They're not generally true at every level of

1010
00:46:53,520 --> 00:46:56,439
Speaker 1: the universe, you know, like there's no equivalent to ice

1011
00:46:56,440 --> 00:46:59,000
Speaker 1: cream at the quantum level, for example, there's no equivalent

1012
00:46:59,040 --> 00:47:02,279
Speaker 1: to cats. Those things only exist at our level. And

1013
00:47:02,360 --> 00:47:04,480
Speaker 1: so I love that as we keep looking deeper into

1014
00:47:04,480 --> 00:47:07,520
Speaker 1: the universe, we discover things about our experience that turn

1015
00:47:07,560 --> 00:47:09,360
Speaker 1: out to just be part of our experience. They're not

1016
00:47:09,480 --> 00:47:13,480
Speaker 1: generally true about the universe, Like our sun is unusual,

1017
00:47:13,520 --> 00:47:16,400
Speaker 1: and maybe our planet is weird, maybe our way of

1018
00:47:16,440 --> 00:47:19,319
Speaker 1: life is weird. And the same way, we discover that

1019
00:47:19,400 --> 00:47:21,600
Speaker 1: the way we experience the universe and the things we

1020
00:47:21,640 --> 00:47:24,399
Speaker 1: think are fundamental about it actually aren't. To me, that's

1021
00:47:24,440 --> 00:47:27,440
Speaker 1: really cool and opens up questions about like other conservation

1022
00:47:27,560 --> 00:47:30,440
Speaker 1: laws are other things that we thought were hard and

1023
00:47:30,480 --> 00:47:32,719
Speaker 1: fast and true about the universe actually just sort of

1024
00:47:32,760 --> 00:47:35,960
Speaker 1: like emergent approximate things, and at a quantum level they're

1025
00:47:36,000 --> 00:47:38,400
Speaker 1: not preserved. That would be kind of scary.

1026
00:47:38,600 --> 00:47:40,480
Speaker 3: Well for me, I'm getting the sense that maybe, like

1027
00:47:40,600 --> 00:47:43,360
Speaker 3: even if we do discover that energy is conserved or

1028
00:47:43,400 --> 00:47:47,239
Speaker 3: not in our universe, that wouldn't maybe really tells what

1029
00:47:47,280 --> 00:47:49,799
Speaker 3: the real truth is because we wouldn't have access to

1030
00:47:49,840 --> 00:47:54,200
Speaker 3: maybe the multiverse in other universes, which would maybe cancel

1031
00:47:54,280 --> 00:47:56,560
Speaker 3: out what we think is the rule of the universe.

1032
00:47:56,800 --> 00:47:58,520
Speaker 1: Yeah, that's right. We could see what we think is

1033
00:47:58,640 --> 00:48:01,759
Speaker 1: energy non conservation and bigger picture, it all balances out,

1034
00:48:02,360 --> 00:48:04,480
Speaker 1: and so we might never really know these answers.

1035
00:48:04,719 --> 00:48:06,480
Speaker 3: Well, I'll just take comfort in the fact that even

1036
00:48:06,520 --> 00:48:09,920
Speaker 3: if I don't exercise today, maybe there's a quantum Woorge

1037
00:48:10,080 --> 00:48:14,040
Speaker 3: in another universe who is doing double the exercise for

1038
00:48:14,080 --> 00:48:16,560
Speaker 3: the tour that both us and in some way you

1039
00:48:16,600 --> 00:48:18,120
Speaker 3: can say that I exercised today.

1040
00:48:18,280 --> 00:48:21,240
Speaker 1: Yeah, that's true, and that quantum Hohoge will live longer

1041
00:48:21,239 --> 00:48:24,879
Speaker 1: than you and on average, you know, some fractionales across

1042
00:48:24,880 --> 00:48:26,200
Speaker 1: the teams, this will be alive or not.

1043
00:48:27,160 --> 00:48:29,560
Speaker 3: Yeah, there you go. There you go, playing with some

1044
00:48:29,680 --> 00:48:33,960
Speaker 3: kittens and counting people in a swimming pool. All right, Well,

1045
00:48:33,960 --> 00:48:37,080
Speaker 3: we hope you enjoyed that. Thanks for joining us. See

1046
00:48:37,120 --> 00:48:37,640
Speaker 3: you next time.

1047
00:48:42,800 --> 00:48:45,680
Speaker 1: For more science and curiosity, come find us on social

1048
00:48:45,719 --> 00:48:49,640
Speaker 1: media where we answer questions and post videos. We're on Twitter,

1049
00:48:49,760 --> 00:48:53,080
Speaker 1: this word instant and now TikTok. And remember that Daniel

1050
00:48:53,120 --> 00:48:56,560
Speaker 1: and Jorge explain the universe is a production of iHeartRadio.

1051
00:48:56,840 --> 00:49:00,400
Speaker 1: For more podcast from iHeart Radio, visit the iHeart Radio

1052
00:49:00,440 --> 00:49:04,480
Speaker 1: Apple Apple Podcasts, or wherever you listen to your favorite shows.