Latest / Daniel and Kelly’s Extraordinary Universe / What's the electric charge of the Universe?

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What's the electric charge of the Universe? · Daniel and Kelly’s Extraordinary Universe

• 0:08
  Speaker 1: Ay, Katie, did we use up all of our electricity
• 0:11
  Speaker 1: puns in the last episode we did together?
• 0:14
  Speaker 2: I don't know. I mean, you're the one who's in charge.
• 0:17
  Speaker 1: Yeah, but I'm trying to stay neutral on this.
• 0:20
  Speaker 2: That's just because you think that puns have such a
• 0:23
  Speaker 2: high potential.
• 0:25
  Speaker 1: They do, though, they do. They so much capacity for
• 0:28
  Speaker 1: humor in electricity.
• 0:30
  Speaker 2: It's almost like electricity induces its own jokes.
• 0:35
  Speaker 1: Let's see, we can get a few more, and it's
• 0:37
  Speaker 1: really down to the wire.
• 0:39
  Speaker 2: You will find no resistance for me.
• 0:56
  Speaker 1: Hi, I'm Daniel. I'm a particle physicist and a professor
• 0:59
  Speaker 1: at you see Irvine, and I'm endlessly fascinated by electricity
• 1:03
  Speaker 1: and its capacity for puns.
• 1:05
  Speaker 2: My name is Katie Golden. I host an animal biology
• 1:09
  Speaker 2: podcast called Creature Feature, and I am a particle enthusiast.
• 1:14
  Speaker 2: I like particles, uh so I enjoy learning about them.
• 1:20
  Speaker 2: What's your favorite particle, Daniel.
• 1:24
  Speaker 1: Oh, my favorite particle? Wow? I feel like now they're
• 1:26
  Speaker 1: all listening to me.
• 1:28
  Speaker 2: Wonder just one?
• 1:32
  Speaker 1: I guess I gotta go top quark because I studied
• 1:34
  Speaker 1: it from my phdtiss and it's the most massive of
• 1:38
  Speaker 1: all the particles in that way, kind of the weirdest.
• 1:41
  Speaker 2: Oh okay, now, which one of the top particles is
• 1:45
  Speaker 2: your favorite? Pick one?
• 1:47
  Speaker 1: Pick one. Well, that's actually quite hilarious because for my PhD,
• 1:51
  Speaker 1: I studied like six top quarks, like literally or six
• 1:54
  Speaker 1: that we found at the time. But the way particle
• 1:57
  Speaker 1: physics works is that you get more and more collisions
• 1:59
  Speaker 1: every year the things ramp up. So folks these days
• 2:02
  Speaker 1: doing their PhD have like tens of thousands of top
• 2:05
  Speaker 1: quarks they get to study. Wow, and I like names
• 2:07
  Speaker 1: for mine. I was like, oh, this is top quark
• 2:09
  Speaker 1: number four. Who I call this number two? Who I
• 2:12
  Speaker 1: call Sally. She's a bit weird, but I love her.
• 2:15
  Speaker 2: That's it's adorable. It's like the the seven Dwarfs, except
• 2:20
  Speaker 2: it's the six quarks. Yeah, sleepy grumpy.
• 2:27
  Speaker 1: I really got to know my top quarks. Well, how
• 2:29
  Speaker 1: about you? You said your pro particle. I'm glad to
• 2:31
  Speaker 1: hear that you're not anti particle.
• 2:33
  Speaker 2: Yeah. No, I mean I like things existing. I'm pro
• 2:37
  Speaker 2: existence of there being stuff. I like stuff. I like
• 2:41
  Speaker 2: the way that stuff works. I like being able to
• 2:44
  Speaker 2: It's like rainy today, and I appreciate the physics of
• 2:48
  Speaker 2: being able to have some tea and you know that
• 2:53
  Speaker 2: it's it's just those are the simple things.
• 2:55
  Speaker 1: Right, Like you're really sticking out a controversial position over
• 2:58
  Speaker 1: their pro.
• 2:58
  Speaker 2: Stuff, prost stuff, pro existence, pro hot tea.
• 3:03
  Speaker 1: And Welcome to the podcast Daniel and Jorge Explain the Universe,
• 3:06
  Speaker 1: a production of iHeartRadio in which we are pro stuff,
• 3:10
  Speaker 1: we are pro particles, we are pro the universe, and
• 3:13
  Speaker 1: we are especially pro you understanding the universe because we
• 3:17
  Speaker 1: think that not only is the universe incredible and majestic
• 3:20
  Speaker 1: and kinda crazy and weird, but that it's also understandable
• 3:25
  Speaker 1: that with our tiny little human brains, we can develop
• 3:28
  Speaker 1: mathematical models and intuitive understanding for what's going on out
• 3:32
  Speaker 1: there in the rest of the universe, from the tiniest
• 3:34
  Speaker 1: little particles to the most massive of super massive black
• 3:38
  Speaker 1: holes and everything in between, including me and you and
• 3:41
  Speaker 1: Katie's dog.
• 3:42
  Speaker 2: Yes, Cookie is a very good physicist because she knows
• 3:46
  Speaker 2: that what goes up comes down when it comes to treats.
• 3:50
  Speaker 1: When I talk them, your dog's name is Cookie, not Biscotti.
• 3:55
  Speaker 2: She yeah, it's funny. We didn't change her name to
• 3:58
  Speaker 2: Italian when we moved here.
• 4:00
  Speaker 1: And why is your dog named Cookie? Is it because
• 4:02
  Speaker 1: she's so delicious.
• 4:03
  Speaker 2: It's wow. Well, no, I don't want to eat my
• 4:08
  Speaker 2: canine made out of dog meat. No, No, it's just
• 4:11
  Speaker 2: very very cute. When she was a little puppy, she's
• 4:13
  Speaker 2: very small and cute and kind of cream colored, so
• 4:16
  Speaker 2: she looked like a little biscotti, which is funny because
• 4:19
  Speaker 2: an Italian biscotti is actually just the general term for cookies,
• 4:24
  Speaker 2: like we say a biscotti, but that doesn't really make
• 4:26
  Speaker 2: any sense because it's like biscotti is plural, quick Italian
• 4:31
  Speaker 2: grammar lesson.
• 4:33
  Speaker 1: And doesn't piscotti actually mean like cook twice.
• 4:35
  Speaker 2: I think, yeah, I don't know if it just means
• 4:37
  Speaker 2: cooked twice. It really is just a general term for cookies,
• 4:42
  Speaker 2: and it's not necessarily the really hard ones that you
• 4:45
  Speaker 2: have to dunk to actually get any enjoyment out of.
• 4:48
  Speaker 2: It's just any cookie is called a biscato, and you know,
• 4:51
  Speaker 2: any kind of cookie is you know, like plural biscottis cookies.
• 4:55
  Speaker 1: Until somebody invents the next generation of cookies and then
• 4:57
  Speaker 1: they can call it like triscotti or something.
• 4:59
  Speaker 2: Right right by phosphate scotti. I don't know chemistry stuff,
• 5:04
  Speaker 2: but yeah, let's talk more about particles that are not
• 5:09
  Speaker 2: so visible as the biscotti particle.
• 5:11
  Speaker 1: That's right, because we're not just here to talk about cookies.
• 5:14
  Speaker 1: We're here to understand the whole universe down to the
• 5:16
  Speaker 1: tiness of the particles it's made out of. And on
• 5:19
  Speaker 1: the podcast, we often talk about the mystery of electric charge.
• 5:23
  Speaker 1: What is it? Why do some particles have it, why
• 5:25
  Speaker 1: do other particles not have it? How does it all work?
• 5:28
  Speaker 1: And we usually think about it in terms of the
• 5:30
  Speaker 1: tiniest little individual particles. One is positive, one is negative,
• 5:34
  Speaker 1: one is neutral. But today we actually want to zoom
• 5:36
  Speaker 1: out and ask a much bigger, grander question about the
• 5:40
  Speaker 1: nature of electric charge.
• 5:42
  Speaker 2: Yeah, you know, I got a fortune cookie message that
• 5:45
  Speaker 2: says you will have an electrifying experience. I'm really glad
• 5:48
  Speaker 2: it meant recording this podcast and not like I was
• 5:51
  Speaker 2: going to need to be resuscitated with those electric paddles.
• 5:55
  Speaker 1: And it might still happen. I mean, this podcast could
• 5:58
  Speaker 1: be very shocking.
• 5:58
  Speaker 2: Today we'll see, well, yeah, we'll see if my heart
• 6:02
  Speaker 2: can take it. But yeah, no, I mean it is interesting,
• 6:05
  Speaker 2: right because like electricity is, it's in everything. It's like
• 6:09
  Speaker 2: in our bodies, the heart rhythm, the cytostoism of our
• 6:12
  Speaker 2: heart is determined by electrical pulses our brain activity, Like
• 6:16
  Speaker 2: you are using electricity right now to think for your
• 6:19
  Speaker 2: brain to kind of understand this podcast. But then it's
• 6:24
  Speaker 2: also you know, it is throughout the universe in everything
• 6:29
  Speaker 2: in terms of how molecules stick to each other. So
• 6:33
  Speaker 2: it's a very interesting force in that, Like I feel
• 6:36
  Speaker 2: like we kind of only think about it when it's
• 6:39
  Speaker 2: really obvious, like lightning or getting shocked by your toaster,
• 6:44
  Speaker 2: but it is literally almost everywhere.
• 6:46
  Speaker 1: It seems like it is almost everywhere, which makes us
• 6:49
  Speaker 1: inspired to think about it. In the grandest sense. We
• 6:52
  Speaker 1: can often learn something about the universe by trying to
• 6:55
  Speaker 1: zoom out by saying, well, what do all these particles
• 6:57
  Speaker 1: make or how do they come together? To determine the
• 6:59
  Speaker 1: biggest features of the universe its size, its shape, it's topology,
• 7:04
  Speaker 1: all this amazing stuff. So in today on the podcast,
• 7:06
  Speaker 1: we want to start from the little particles they're electric charges,
• 7:09
  Speaker 1: and zoom out to think about the whole universe. And
• 7:13
  Speaker 1: so today in the podcast, we'll be answering the question
• 7:20
  Speaker 1: what is the total electric charge of the universe?
• 7:25
  Speaker 2: Twenty that's my guess. It just feels it feels right.
• 7:31
  Speaker 2: It feels like a good number. Twenty charge.
• 7:35
  Speaker 1: You know, there is something interesting about the numerology of
• 7:38
  Speaker 1: the universe. If you imagine like writing down the final
• 7:41
  Speaker 1: equation of the universe or looking at the final numbers
• 7:45
  Speaker 1: in the final theory, you got to wonder, like why
• 7:47
  Speaker 1: those numbers are not some other numbers. You know, there
• 7:50
  Speaker 1: are some numbers that obviously are just human and not
• 7:52
  Speaker 1: important because they have units on them, and we make
• 7:55
  Speaker 1: up units and so anything with the units on it
• 7:57
  Speaker 1: is irrelevant. But you know, it's like the final theory
• 7:59
  Speaker 1: of string theory that explains the universe has like a
• 8:02
  Speaker 1: three in it or eleven in it. Then you got
• 8:04
  Speaker 1: to wonder, like why that number is the universe somehow?
• 8:07
  Speaker 1: Eleven ish right?
• 8:08
  Speaker 2: M Yeah, it does have kind of an eleveny feeling
• 8:12
  Speaker 2: to it. I think that makes sense.
• 8:14
  Speaker 1: That sounds like a delicious name for a cookie.
• 8:16
  Speaker 2: Eleveny sounds like eleven to cookie. So I guess, like
• 8:20
  Speaker 2: when we're talking about like total electric charge, like I
• 8:23
  Speaker 2: don't even know where to start really, because it's like,
• 8:26
  Speaker 2: I mean, it could be positive, it could be negative,
• 8:28
  Speaker 2: it could be neutral. I don't know if they're like
• 8:31
  Speaker 2: if this is something that even could have a number, right, Like,
• 8:34
  Speaker 2: if it's a positive charge, could it have a positive
• 8:37
  Speaker 2: Is twenty even a possible answer?
• 8:39
  Speaker 1: Tony actually is a possible answer. But we're gonna see
• 8:43
  Speaker 1: that there's a lot of sort of assumptions built into
• 8:46
  Speaker 1: this discussion about what's natural, what makes sense, what numbers
• 8:50
  Speaker 1: we would sort of accept, what numbers need explanation, and
• 8:53
  Speaker 1: what numbers don't need explanation, and so these kind of
• 8:56
  Speaker 1: questions I think are fascinating because they reflect not just
• 8:58
  Speaker 1: our understanding of the universe, but our attitudes about it,
• 9:01
  Speaker 1: our biases, our presuppositions about what kind of answers make sense.
• 9:06
  Speaker 1: So I was wondering, as usual, what people thought about
• 9:08
  Speaker 1: this question before we dove in. So I went out
• 9:10
  Speaker 1: there and I asked our group of volunteers what they
• 9:13
  Speaker 1: thought about this question. If you'd like to join this
• 9:16
  Speaker 1: not very illustrious, but very enthusiastic group of volunteers, please
• 9:20
  Speaker 1: write to me at questions at Danielandhorge dot com. So
• 9:23
  Speaker 1: think about it for a moment before you hear these answers.
• 9:26
  Speaker 1: What do you think the total electric charge of the
• 9:29
  Speaker 1: whole universe could be? Here's what people had to say.
• 9:32
  Speaker 3: I would say zero, so that all the charges eventually
• 9:37
  Speaker 3: equal out. That would seem nice and symmetric. But since
• 9:41
  Speaker 3: that's almost certainly not the right answer, I'm gonna go
• 9:44
  Speaker 3: with plus five electron vaults.
• 9:47
  Speaker 4: Well, I know there's the law of the conservation of energy,
• 9:49
  Speaker 4: so I guess it probably depends on what the charge
• 9:51
  Speaker 4: was of all the energy that existed during the Big Bang.
• 9:54
  Speaker 4: Given that Daniel and Jorge are explainers of the universe,
• 9:57
  Speaker 4: there are two people, and they're both very positive, I'm
• 10:00
  Speaker 4: going to say plus two.
• 10:01
  Speaker 5: The electromagnetic field, as far as I understand it, can
• 10:03
  Speaker 5: be thought I was covering the entire universe, and I
• 10:06
  Speaker 5: don't see why that would have been created with a
• 10:10
  Speaker 5: non zero value. So I'm going to say the overall
• 10:14
  Speaker 5: electric charge is zero.
• 10:16
  Speaker 6: Shouldn't this be zero because all this symmetry of particles
• 10:20
  Speaker 6: and charges and the words for maximizing entropy is this emulated.
• 10:28
  Speaker 6: I have my dear, I feel like the net electric
• 10:30
  Speaker 6: charge in the universe must be zero, but that's probably
• 10:34
  Speaker 6: not correct.
• 10:35
  Speaker 7: I want to guess that it's the same as a
• 10:37
  Speaker 7: single electron, only because if every electron is just an
• 10:43
  Speaker 7: expression of the excitation of a single field, then that
• 10:48
  Speaker 7: whole field represents the charge of a single electron. Oh Man, Daniel,
• 10:54
  Speaker 7: I don't know, sounds good.
• 10:56
  Speaker 2: I love the answer. That's like, it seems like it
• 10:58
  Speaker 2: should be zero, like neutral, but knowing that the universe
• 11:02
  Speaker 2: is weird, it's probably like five.
• 11:05
  Speaker 1: That was basically your answer, right, I think that makes
• 11:08
  Speaker 1: a lot of sense.
• 11:08
  Speaker 2: That basically sums up this is typically what I learned
• 11:11
  Speaker 2: from these recordings with you, is that it's like, well,
• 11:14
  Speaker 2: it seems like it should be something really like neat
• 11:16
  Speaker 2: and precise and tidy, and then it's something like five
• 11:21
  Speaker 2: point seven units of physics.
• 11:27
  Speaker 1: It's true that the universe is chock full of surprises,
• 11:30
  Speaker 1: and the way that we think things should work isn't
• 11:32
  Speaker 1: always the way things actually work. But I think this
• 11:35
  Speaker 1: already raises that really fascinating issue. Like if I told
• 11:38
  Speaker 1: you the answer is zero, you'd be like, cool, that
• 11:40
  Speaker 1: kind of makes sense, and you might not even need
• 11:42
  Speaker 1: any more explanation because zero is just like a natural answer.
• 11:46
  Speaker 1: But if I tell you the answer is five, then
• 11:48
  Speaker 1: you're like, well, why five? Why not four? Why not seventeen? Right?
• 11:51
  Speaker 1: Then it needs an explanation. It tells us something about
• 11:54
  Speaker 1: the kind of answers we're willing to accept about these
• 11:56
  Speaker 1: deep questions about the universe.
• 11:58
  Speaker 2: I'm not anti math, but like, I don't think math
• 12:02
  Speaker 2: is a natural thing for me, and certainly not like
• 12:04
  Speaker 2: the kind of math required to sum up all of
• 12:07
  Speaker 2: the charge of the universe, which sounds very time consuming.
• 12:11
  Speaker 2: How would you even go about, like what is the
• 12:14
  Speaker 2: mathematical process here? We're hopefully not counting the atoms and
• 12:19
  Speaker 2: their charges and just summing them up, because that seems
• 12:22
  Speaker 2: like it would take a whole afternoon.
• 12:26
  Speaker 1: Yeah, that's exactly what we're doing. What when we talk
• 12:29
  Speaker 1: about the total electric charge of the universe, we really
• 12:32
  Speaker 1: just mean put all the protons on one side and
• 12:35
  Speaker 1: all the electrons on the other side and count them
• 12:38
  Speaker 1: up and add it all up.
• 12:40
  Speaker 2: It sounds like doing taxes.
• 12:43
  Speaker 1: Yeah, exactly, we're doing the accounting of the universe. It's
• 12:46
  Speaker 1: just one big Excel file. Actually, that's the way the
• 12:48
  Speaker 1: universe works. It's it's just a big Excel's bridge.
• 12:53
  Speaker 2: Oh god, that's the darkest outcome.
• 12:56
  Speaker 1: But you know, that's really how we define things. The
• 12:59
  Speaker 1: chargement of is the sum of the charges of things.
• 13:02
  Speaker 1: It's made out of Like if you have a cloud
• 13:04
  Speaker 1: of hydrogen gas. It's made of protons electrons, one proton
• 13:08
  Speaker 1: per electron, so the whole cloud is neutral. If you
• 13:11
  Speaker 1: added like one proton in there without an electron, then
• 13:13
  Speaker 1: the whole cloud would have an overall positive charge. So
• 13:18
  Speaker 1: that's really fascinating because the charge of an object really
• 13:20
  Speaker 1: is just the sum of the charges. There's nothing else
• 13:23
  Speaker 1: going on in there. It's very crisp, very clean to
• 13:26
  Speaker 1: calculate the charge of an object.
• 13:28
  Speaker 2: So I noticed in a lot of the answers, which
• 13:31
  Speaker 2: I also kind of understand and agree with, that there
• 13:35
  Speaker 2: is this and what you said earlier, which is there's
• 13:37
  Speaker 2: this comfort with the idea of it being zero because
• 13:41
  Speaker 2: that seems balanced, right, Like this intuitive feeling that there
• 13:45
  Speaker 2: should be for every positively charged particle there should be
• 13:48
  Speaker 2: a negatively charged particle that they're for every proton there
• 13:53
  Speaker 2: should be an electron. Essentially, Why do you think there
• 13:57
  Speaker 2: is this assumption which I'm not necess really disagree with.
• 14:01
  Speaker 2: I just think that's interesting that that is a comfortable
• 14:04
  Speaker 2: stance for people to take, Like, what is it about
• 14:07
  Speaker 2: that neutrality that we like so much?
• 14:09
  Speaker 1: Yeah, I think that's a great question and a deep one.
• 14:12
  Speaker 1: I think it just reflects our biases. You know, I
• 14:14
  Speaker 1: think we like to imagine that the universe makes sense,
• 14:17
  Speaker 1: that it runs on laws, and those laws are reasonable
• 14:20
  Speaker 1: and they make sense, and that they're not arbitrary, and
• 14:23
  Speaker 1: having the overall universe have it's sort of just an
• 14:26
  Speaker 1: arbitrary number for its charge. It needs an explanation, you know,
• 14:30
  Speaker 1: why eighteen? Why sixteen? And it takes a sort of
• 14:34
  Speaker 1: different philosophical approach to ask, like, well, doesn't zero also
• 14:38
  Speaker 1: need an explanation, Like if you have exactly the same
• 14:41
  Speaker 1: number of protons and electrons in the universe, doesn't that
• 14:45
  Speaker 1: also need some explanation. It's sort of an amazing coincidence.
• 14:49
  Speaker 1: Anytime you see a coincidence in nature, you wonder like, hmmm,
• 14:52
  Speaker 1: is there a reason for that? Is there some underlying
• 14:54
  Speaker 1: process we're not aware of that's making that happen, And
• 14:57
  Speaker 1: sometimes it does and sometimes it's not. You know, there's
• 15:00
  Speaker 1: a huge coincidence in our sky. The sun and the
• 15:02
  Speaker 1: moon are almost exactly the same size in our sky,
• 15:05
  Speaker 1: which makes for very dramatic eclipses. Is that a coincidence? Yeah? Absolutely,
• 15:10
  Speaker 1: There's no reason why the sun and the moon should
• 15:12
  Speaker 1: be the same size at all, Like they're very differently
• 15:15
  Speaker 1: sized objects, very different distances away from the Earth. It's
• 15:19
  Speaker 1: just a literally cosmic coincidence that they balance each other
• 15:22
  Speaker 1: in the sky and appeared to be the same size
• 15:25
  Speaker 1: other times. We think that there might really be an
• 15:27
  Speaker 1: underlying reason why the universe would have some cosmic coincidence.
• 15:32
  Speaker 1: So in the case of its total charge, we're just
• 15:34
  Speaker 1: adding up the protons and the electrons and counting them.
• 15:37
  Speaker 1: And I just want to go back to this for
• 15:38
  Speaker 1: one minute, because I think it's kind of amazing that
• 15:40
  Speaker 1: you can calculate the whole charge of the universe just
• 15:43
  Speaker 1: by adding up its bits, because you know that's not
• 15:45
  Speaker 1: true for other stuff, like for mass, right, you can't
• 15:48
  Speaker 1: just say, well, what's the mass of the universe. I'm
• 15:50
  Speaker 1: going to add up the mass of all the quarks
• 15:51
  Speaker 1: and the electrons. Because we've talked about lots of times
• 15:54
  Speaker 1: on the podcast, like the mass of the proton is
• 15:56
  Speaker 1: not just the mass of the things that's made out
• 15:58
  Speaker 1: of there's also energy in its bonds which contributes to
• 16:01
  Speaker 1: its mass. So mass is much more slippery of a
• 16:04
  Speaker 1: concept than electric charge. Electric charge is incredibly crisp and clean,
• 16:08
  Speaker 1: and so you actually can measure the electric charge of
• 16:10
  Speaker 1: the universe on an Excel spreadsheet is really just very
• 16:13
  Speaker 1: simple map, but the numbers are staggering, Like how many
• 16:17
  Speaker 1: protons are there in the universe is something like ten
• 16:21
  Speaker 1: to the eighty protons in the universe. And that's, of
• 16:24
  Speaker 1: course just the observable universe, just the part that we
• 16:27
  Speaker 1: can see and interact with, and that life has had
• 16:30
  Speaker 1: enough time to travel to us since the origin of
• 16:32
  Speaker 1: the universe. We think they're like ten with eighty zeros
• 16:36
  Speaker 1: after it, protons in that chunk of the universe. What
• 16:39
  Speaker 1: lies beyond, of course, we can't know.
• 16:41
  Speaker 2: Yeah, this seems like the trickiest part, right is obviously
• 16:45
  Speaker 2: we cannot have a bean counter go throughout the whole
• 16:49
  Speaker 2: universe counting every single electron and proton, but we would
• 16:53
  Speaker 2: need to sort of, you know, almost like average out
• 16:57
  Speaker 2: like what our expectations are, Like take a slice of
• 17:00
  Speaker 2: the universe, figure out like if it's a representative sample
• 17:04
  Speaker 2: of the universe, and then scale that up or something.
• 17:07
  Speaker 2: I don't even know. Look, I'm thinking in terms of
• 17:09
  Speaker 2: sort of like biology studies and statistics and stuff, but
• 17:12
  Speaker 2: I don't even know if those kinds of things work
• 17:15
  Speaker 2: for the universe, right, because you could have. You could
• 17:18
  Speaker 2: take a reasonably large slice of the universe and try
• 17:22
  Speaker 2: to assume it's a representative sample of the whole universe.
• 17:26
  Speaker 2: But you know, then you could have an entire, massively
• 17:30
  Speaker 2: large area of the universe where you know the density
• 17:34
  Speaker 2: of stuff, or there's a presence of a black hole,
• 17:36
  Speaker 2: and things are completely different.
• 17:38
  Speaker 1: Now, this is a really good point, and I think
• 17:40
  Speaker 1: that fundamentally we need to talk about the universe as
• 17:43
  Speaker 1: a whole, even beyond what we can see. Because imagine
• 17:46
  Speaker 1: the universe is infinite, right, It's still possible that it
• 17:49
  Speaker 1: has an equal number of electrons and protons, that the
• 17:53
  Speaker 1: total universe charge is neutral. But then you know where
• 17:55
  Speaker 1: any individual particle is going to be is going to
• 17:58
  Speaker 1: be a little bit random. So if you take an
• 18:00
  Speaker 1: observable universe sized scoop of that infinite universe, you could
• 18:04
  Speaker 1: take lots of different scoops one here, when they're one
• 18:07
  Speaker 1: exactly where we are, you might get exactly the same
• 18:10
  Speaker 1: number of electrons and protons, but that's actually quite unlikely.
• 18:14
  Speaker 1: You're very likely to get a slight difference in the
• 18:16
  Speaker 1: protons and electrons for any random scoop. Overall, they would
• 18:19
  Speaker 1: average out, but any observable universe scoop would probably have
• 18:23
  Speaker 1: a very small difference. And that's not something we can
• 18:25
  Speaker 1: practically measure, because, as you say, you have to go
• 18:28
  Speaker 1: touch every proton and every electron. But we can think
• 18:31
  Speaker 1: about the overall universe, and we can extrapolate from what
• 18:34
  Speaker 1: we've learned about the laws of physics and what we've
• 18:37
  Speaker 1: observed about the behavior of charges in our scoop to
• 18:40
  Speaker 1: think about what the overall charge of the universe is.
• 18:43
  Speaker 2: Okay, So it's all about sort of trying to figure
• 18:48
  Speaker 2: out some underlying rule that we might be able to
• 18:53
  Speaker 2: safely assume applies to the rest of the universe, rather
• 18:56
  Speaker 2: than trying to get sort of a representative sample, like
• 18:59
  Speaker 2: we are looking for something that seems like a consistent
• 19:02
  Speaker 2: rule that should apply and scale up.
• 19:05
  Speaker 1: Yeah, I think we can actually do both. We can
• 19:08
  Speaker 1: think about what would make sense, what the rules of
• 19:11
  Speaker 1: electricity and magnetism are, and whether we think the universe
• 19:14
  Speaker 1: should be neutral, and then we can do our best
• 19:16
  Speaker 1: to go out there and look to see if that
• 19:18
  Speaker 1: actually works, look for any evidence of deviation from that,
• 19:22
  Speaker 1: see if we can find hints that we could be
• 19:24
  Speaker 1: wrong about the nature of the universe.
• 19:26
  Speaker 2: Okay, Well, I'm gonna go get my big old chalkboard
• 19:29
  Speaker 2: on wheels do some goodwill hunting style, like suddenly I'm
• 19:34
  Speaker 2: good at math inexplicably, and then maybe I'll come up
• 19:39
  Speaker 2: with the number. But we'll take a quick break and
• 19:42
  Speaker 2: we'll see what Daniel thinks of that number I come
• 19:44
  Speaker 2: up with. So, Daniel, I did some I just wrote
• 20:00
  Speaker 2: some random fractions, but I'm not really getting anywhere. I
• 20:03
  Speaker 2: think that I need more stuff to work with here
• 20:06
  Speaker 2: in my math exploration, because this is a thing, like
• 20:10
  Speaker 2: with theoretical math and theoretical physics, I have such a
• 20:15
  Speaker 2: hard time understanding where one even begins to try to understand,
• 20:19
  Speaker 2: like I would assume perhaps for this like there would
• 20:21
  Speaker 2: be some you would start with some experiments to see
• 20:26
  Speaker 2: if there is some kind of rule that it's consistent
• 20:29
  Speaker 2: in terms of the average charge of a system.
• 20:33
  Speaker 1: And so we can start theoretically and think about like
• 20:35
  Speaker 1: how electromagnetism works. And as you say, thinking about the
• 20:39
  Speaker 1: rules is really important because it helps us understand, like, also,
• 20:43
  Speaker 1: can the electric charge of the universe change? Is it
• 20:47
  Speaker 1: possible for it to go up and down? Because if
• 20:49
  Speaker 1: it is, then it's very difficult to imagine the electric
• 20:52
  Speaker 1: charge of the universe is zero, or even to know
• 20:54
  Speaker 1: what the number is. But something that's super fascinating and
• 20:57
  Speaker 1: super important about electric charge really that it's deeply fundamental
• 21:01
  Speaker 1: to the nature of the universe and matter itself, is
• 21:04
  Speaker 1: that electric charge is conserved. That means that the total
• 21:07
  Speaker 1: electric charge we think can never change. Whatever that number is.
• 21:11
  Speaker 1: Add up all the pluses and all the minuses, and
• 21:13
  Speaker 1: you get some number zero or seven or whatever that
• 21:16
  Speaker 1: cannot change. Is no physical process in the universe that
• 21:19
  Speaker 1: can change that number. There's a wrinkle there. It doesn't
• 21:22
  Speaker 1: mean you can't create and destroy charged particles, right Like,
• 21:26
  Speaker 1: you can have a photon which has no charge, and
• 21:28
  Speaker 1: it can turn into an electron and its antiparticle the positron,
• 21:33
  Speaker 1: so that you have created new charged particles, but you
• 21:36
  Speaker 1: created a plus one and a minus one, so the
• 21:38
  Speaker 1: total charge hasn't changed. Photon with zero the positron and
• 21:42
  Speaker 1: electron pair total charge is still zero. So that kind
• 21:46
  Speaker 1: of stuff can happen. You can create and destroy charge particles,
• 21:49
  Speaker 1: but for some reason, the universe doesn't let you just
• 21:52
  Speaker 1: make an electron or just make a positron. You have
• 21:55
  Speaker 1: to keep those charges balanced.
• 21:57
  Speaker 2: Interesting so when I rub my feet real fast against
• 22:00
  Speaker 2: the carpet, I'm wearing socks, and I have changed my
• 22:04
  Speaker 2: charge slightly, And so I assume though then I have
• 22:08
  Speaker 2: potentially also changed the charge of the carpet or something.
• 22:13
  Speaker 2: Right like, It's not like I don't just produce a
• 22:16
  Speaker 2: positive Well, actually, I guess I don't know what my
• 22:18
  Speaker 2: charges once I rubbed my socks real fast against the carpet.
• 22:21
  Speaker 2: All I know is that I have changed my state
• 22:24
  Speaker 2: somewhat so that when I touch a doorknob, I get
• 22:26
  Speaker 2: a little zap. But my assumption is that this is
• 22:30
  Speaker 2: not coming out of nowhere. There's some exchange happening exactly.
• 22:34
  Speaker 1: That's a really deep insight right there. That if something
• 22:36
  Speaker 1: is conserved, then there has to be a current of it.
• 22:40
  Speaker 1: Then in order for you to get some of it,
• 22:41
  Speaker 1: it has to come from somewhere. It has to flow.
• 22:45
  Speaker 1: So if you're going to get a bunch of electrons,
• 22:46
  Speaker 1: you can't just create them from nothing. They have to
• 22:48
  Speaker 1: come from somewhere. Somewhere else has to lose electrons. If
• 22:52
  Speaker 1: you're going to gain electrons, or more specifically, if you're
• 22:55
  Speaker 1: going to gain negative charges, something else has to gain
• 22:58
  Speaker 1: positive charges either by losing a life netrons or creating
• 23:00
  Speaker 1: positrons or something. So this is like a conserved current
• 23:04
  Speaker 1: in the universe. You cannot just create charge out of nothing.
• 23:08
  Speaker 1: If you're getting it, it comes from somewhere, and that
• 23:11
  Speaker 1: tells you that it's like deeply ingrained in the nature
• 23:14
  Speaker 1: of reality itself. And there's lots of things in the
• 23:16
  Speaker 1: universe we see are almost conserved, like energy is mostly conserved.
• 23:21
  Speaker 1: And this is hard for people to grasp because they
• 23:23
  Speaker 1: think of that way of energy, that energy has to
• 23:25
  Speaker 1: come from somewhere and go to somewhere. But actually we
• 23:28
  Speaker 1: know that energy increases in the universe as it expands.
• 23:31
  Speaker 1: So energy is mostly conserved, but not Actually it's not
• 23:34
  Speaker 1: an exact symmetry or conservation of the universe. Same with
• 23:38
  Speaker 1: lots of other things we talk about, like lefton number
• 23:40
  Speaker 1: or other symmetries we have in particle physics. But this
• 23:43
  Speaker 1: one is exact. This one in the universe will never
• 23:46
  Speaker 1: ever let you violate. It's like down to the wire.
• 23:48
  Speaker 1: It will not give an inch on charge conservation.
• 23:51
  Speaker 2: I don't want to go on a tangent, but you
• 23:53
  Speaker 2: said that the energy increases as the universe expands.
• 23:57
  Speaker 1: Yeah, energy is only conserved if space is constant. But
• 24:01
  Speaker 1: if space is expanding, then is creating more space, and
• 24:04
  Speaker 1: that new space always comes with energy built in. It's
• 24:07
  Speaker 1: like the dark energy of the universe, So the total
• 24:09
  Speaker 1: energy of the universe is actually increasing if space is expanding.
• 24:14
  Speaker 1: We have a whole podcast about that.
• 24:15
  Speaker 2: It's really fun, that's really cool. Yeah, I'm gonna listen
• 24:17
  Speaker 2: to it.
• 24:20
  Speaker 1: But that's not true for electric charge. And I want
• 24:22
  Speaker 1: to disentangle two concepts here. We're talking a lot about
• 24:25
  Speaker 1: particles and antiparticles, and it's true that if you make
• 24:28
  Speaker 1: an electron, you also have to make its antiparticle. But
• 24:31
  Speaker 1: charge conservation is not the same thing as like matter
• 24:34
  Speaker 1: conservation or antimatter conservation. Matter particles can be positive or
• 24:38
  Speaker 1: they can also be negative. Antimatter particles can be positive
• 24:42
  Speaker 1: and they can be negative. So for example, electron we
• 24:45
  Speaker 1: call matter and it's negative. Proton we call matter and
• 24:48
  Speaker 1: it's positive. Antiproton would be negative, anti electron, the positron
• 24:53
  Speaker 1: would be positive. And it's a whole other question about
• 24:56
  Speaker 1: like matter antimatter symmetry in the universe. Like we think
• 24:59
  Speaker 1: that the treats matter and antimatter almost exactly the same
• 25:02
  Speaker 1: way but not quite right. But charge conservation is a
• 25:06
  Speaker 1: different thing than matter antimatter. Conservation matter anti matter is
• 25:10
  Speaker 1: another example of one where the universe is almost conserved,
• 25:13
  Speaker 1: almost symmetric, but not exactly. But charge conservation the universe
• 25:17
  Speaker 1: respects exactly.
• 25:18
  Speaker 2: That's so interesting. It's like it makes it feel like
• 25:21
  Speaker 2: like electricity in charge is like much more. I mean,
• 25:25
  Speaker 2: I guess everything is fundamental, but it's like that this
• 25:27
  Speaker 2: is like the sort of one of the you know,
• 25:31
  Speaker 2: most fundamental aspects or causal aspects of the function of
• 25:35
  Speaker 2: the universe.
• 25:36
  Speaker 1: Yeah, it seems like a deep clue about the nature
• 25:38
  Speaker 1: of reality itself. And you might ask, like, well, where
• 25:41
  Speaker 1: does it come from? Right? Why is it this way?
• 25:44
  Speaker 1: What does it tell us about the nature of reality?
• 25:46
  Speaker 1: And about one hundred years ago a mathematician Emmy Nuther
• 25:49
  Speaker 1: told us that everything that's conserved in the universe, anytime
• 25:52
  Speaker 1: there's a quantity that doesn't change, like momentum, is conserved
• 25:55
  Speaker 1: in a similar way. It tells you about some symmetry
• 25:59
  Speaker 1: in the universe that every conservation law, like conservation of
• 26:02
  Speaker 1: electric charge or conservation of momentum comes from some symmetry.
• 26:06
  Speaker 1: And that's a nuclear's theorem that every symmetry leads to
• 26:08
  Speaker 1: a conservation law. If there's a symmetry, it means some
• 26:11
  Speaker 1: quantity is conserved. And the case of momentum, the reason
• 26:15
  Speaker 1: momentum is conserved in the universe is because there's no
• 26:18
  Speaker 1: absolute location in space. Every place in the universe has
• 26:21
  Speaker 1: the same laws of physics. We think, it doesn't matter
• 26:23
  Speaker 1: if you do your experiment here or somewhere else, or
• 26:26
  Speaker 1: an alpha centauri, like, the fundamental laws of the universe
• 26:29
  Speaker 1: are the same. It's called translation invariance, and you do
• 26:33
  Speaker 1: a little bit of math, and out of translation in
• 26:35
  Speaker 1: variance comes conservation of momentum. So then you might ask, well,
• 26:39
  Speaker 1: what symmetry is it that creates conservation of electric charge?
• 26:44
  Speaker 1: Why do we have that? What does it tell us
• 26:45
  Speaker 1: about the universe? It's a little bit mathematical. It tells
• 26:48
  Speaker 1: us something about the phase of the electromagnetic field. The
• 26:52
  Speaker 1: electromagnetic field of these numbers that feel all of space
• 26:55
  Speaker 1: right and like, do you have an electric field here?
• 26:57
  Speaker 1: Do you have a magnetic field here? But those numbers
• 27:00
  Speaker 1: also have directions, like everywhere in space. The electromagnetic field
• 27:04
  Speaker 1: isn't just a number, it's an arrow. It points in
• 27:07
  Speaker 1: a certain direction, and the phase of that arrow, like
• 27:10
  Speaker 1: which direction it's actually pointing in, turns out to not
• 27:13
  Speaker 1: really matter. You can change that without changing the dynamics
• 27:15
  Speaker 1: of electromagnetism, and so it's a little bit mathematical and abstract,
• 27:20
  Speaker 1: but this is the quantity whose symmetry leads to conservation
• 27:25
  Speaker 1: of electric charge. And actually there's a whole set of
• 27:28
  Speaker 1: these symmetries, of these fundamental fields of the universe that
• 27:31
  Speaker 1: lead to conservation laws. We have an episode about these
• 27:34
  Speaker 1: gauge symmetries and how they lead to conservations and how
• 27:36
  Speaker 1: they're really deeply fundamental to the way the universe works.
• 27:40
  Speaker 1: So it's a little bit abstract, but conservation of electric
• 27:43
  Speaker 1: charge is telling us something about the nature of the
• 27:45
  Speaker 1: electromagnetic field and the symmetries of that field.
• 27:49
  Speaker 2: If you changed the direction of an electromagnetic field, would
• 27:54
  Speaker 2: that have an impact on the direction of other electromagnetic
• 27:59
  Speaker 2: fields or what is just simply change direction and have
• 28:03
  Speaker 2: no impact on anything else.
• 28:06
  Speaker 1: It absolutely would have an impact if you didn't have photons.
• 28:10
  Speaker 1: So photons are the things that actually preserve this symmetry.
• 28:13
  Speaker 1: Without photons, you can't have this symmetry in the universe.
• 28:16
  Speaker 1: Photons like zip around transmitting this information about the direction
• 28:20
  Speaker 1: of electric field changing from here to there. You can
• 28:22
  Speaker 1: actually deduce the existence of photons just by saying I
• 28:26
  Speaker 1: want an electromagnetic field and I wanted to have this
• 28:28
  Speaker 1: weird particular symmetry. For that to happen, you have to
• 28:32
  Speaker 1: have photons. And so that sort of like explains why
• 28:35
  Speaker 1: we have photons, why we have forces. In general, all
• 28:38
  Speaker 1: of the forces are actually there to preserve these symmetries.
• 28:42
  Speaker 1: So it's a really fascinating and deep new way to
• 28:45
  Speaker 1: think about the nature of forces. Encourage everybody interested in
• 28:48
  Speaker 1: this stuff to check out our episode about gauge symmetry.
• 28:51
  Speaker 1: But this tells us something about the nature of electric charge,
• 28:54
  Speaker 1: but it's still not something we really understand. Like we
• 28:57
  Speaker 1: kick the can down the road a little bit. We say, okay,
• 28:59
  Speaker 1: so just conserving the universe, Why well because of this
• 29:02
  Speaker 1: other weird symmetry in the universe. Why does it have
• 29:05
  Speaker 1: that other weird symmetry. We don't know. That's just like
• 29:08
  Speaker 1: something we observe, and this is the process of science, right,
• 29:11
  Speaker 1: We're like, why is this oh because of that?
• 29:13
  Speaker 7: Well?
• 29:13
  Speaker 1: Why that? Oh because of this other thing? Well why
• 29:15
  Speaker 1: that other thing, right, and so we're sort of at
• 29:18
  Speaker 1: that stage and we're like, we don't know what that
• 29:20
  Speaker 1: really means, but we do think the universe preserves it.
• 29:24
  Speaker 2: Yeah, I mean that's interesting. I think it's also interesting
• 29:26
  Speaker 2: this sort of way you phrased it, which is that
• 29:28
  Speaker 2: like photons are here in order to maintain this neutrality
• 29:33
  Speaker 2: or this conservation. And look, I'm totally here for the ride,
• 29:38
  Speaker 2: so I believe you. But I also think it's interesting that, like, uh,
• 29:43
  Speaker 2: I think that sometimes like we have as humans, we
• 29:46
  Speaker 2: are extremely causal, right, Like we love a thing that
• 29:52
  Speaker 2: like had like this causes this, right X causes why
• 29:56
  Speaker 2: I push a ball? That's what causes the ball to
• 29:58
  Speaker 2: roll down the hill. I wonder like if you know
• 30:02
  Speaker 2: there's something I mean it it certainly seems like everything
• 30:06
  Speaker 2: is interlocking in this extremely precise way, but it's like, well,
• 30:12
  Speaker 2: could one option be like everything sort of happened all
• 30:15
  Speaker 2: at once, right, like in terms of like everything maybe interlocking,
• 30:18
  Speaker 2: but one thing doesn't necessarily cause another thing, or could
• 30:21
  Speaker 2: it be like that you have this fundamental rule about
• 30:24
  Speaker 2: charge being conserved, and then somehow like photons became this,
• 30:29
  Speaker 2: Like I mean, in biology, it's like called the spandrel,
• 30:33
  Speaker 2: where it's like this thing that doesn't at least initially
• 30:36
  Speaker 2: have any purpose, but it is just because of the
• 30:40
  Speaker 2: structure of the organism. This structure has to exist. Like
• 30:46
  Speaker 2: an architecture, you'll have a spandrel being like a section
• 30:50
  Speaker 2: of the wall when you have an archway like that
• 30:53
  Speaker 2: is sort of between the rectangle of the opening and
• 30:57
  Speaker 2: then the arch. There's like those little kind of like
• 31:00
  Speaker 2: curvy pizza slices which are the spandrels, and they don't
• 31:04
  Speaker 2: actually serve any structural purpose, but they just have to
• 31:07
  Speaker 2: exist because the arch is there. And so like I
• 31:12
  Speaker 2: find that kind of interesting of like how do we like,
• 31:14
  Speaker 2: what are some of the ways that we think about
• 31:17
  Speaker 2: these Like could photons just obviously we have use for
• 31:21
  Speaker 2: photons now and they fit in with everything in all
• 31:24
  Speaker 2: the other particles in the universe, But just like, are
• 31:26
  Speaker 2: these things just happening because of some fundamental rule basically
• 31:29
  Speaker 2: forced everything else into place? Or did everything just kind
• 31:32
  Speaker 2: of pop into place all at once? And now my
• 31:35
  Speaker 2: brain hurts, Yeah, we don't know.
• 31:38
  Speaker 1: The answer to that question. We're struggling to figure it out.
• 31:41
  Speaker 1: We think that maybe understanding the nature of reality at
• 31:44
  Speaker 1: a deeper level, you know, quantum gravity. That might explain
• 31:47
  Speaker 1: where all these fields come from and why we have
• 31:50
  Speaker 1: them and why they have These symmetries could help us
• 31:53
  Speaker 1: understand why this exists in our universe. And there's some
• 31:56
  Speaker 1: people exploring theories that suggest that maybe charge is in conserved,
• 32:00
  Speaker 1: like maybe it's almost conserved, ben we've never seen it
• 32:04
  Speaker 1: be broken, but at some very tiny level, like very
• 32:07
  Speaker 1: very rarely can be broken. And most of these theories
• 32:11
  Speaker 1: suggest that our universe exists in higher dimensions, that like
• 32:14
  Speaker 1: it's more than just the three dimensions of space plus
• 32:16
  Speaker 1: one dimension of time that we're used to, but that
• 32:19
  Speaker 1: it's like five dimensional or six dimensional or ten dimensional
• 32:22
  Speaker 1: or whatever, and that maybe it's neutral in that ten
• 32:24
  Speaker 1: dimensional space, but in our like four dimensional subspace, maybe
• 32:28
  Speaker 1: it's not. You know, if you imagine the whole universe
• 32:30
  Speaker 1: is neutral, but you have like a random slice of it,
• 32:33
  Speaker 1: then particles can move in and out of that slice,
• 32:35
  Speaker 1: and that would look to you like charge is not conserved.
• 32:39
  Speaker 1: There's no data to support these ideas, but it's the
• 32:41
  Speaker 1: kind of things people are thinking about. You could create
• 32:44
  Speaker 1: charge non conservation in our universe by sort of expanding
• 32:47
  Speaker 1: the concept of the universe to something with more dimensions
• 32:50
  Speaker 1: in it. But if the universe does respect charge conservation,
• 32:53
  Speaker 1: that means that the total charge of the universe now
• 32:57
  Speaker 1: is the same as it was a minute ago, is
• 32:58
  Speaker 1: the same as it was in hours ago, is the
• 33:00
  Speaker 1: same as it was a billion years ago, Which means
• 33:04
  Speaker 1: that to figure out what the charge of the universe
• 33:05
  Speaker 1: is today, we only need to think about what the
• 33:08
  Speaker 1: charge of the universe was at the Big Bang or
• 33:11
  Speaker 1: when it began, right, and that will tell us what
• 33:13
  Speaker 1: the charge of the universe is still today. And that
• 33:17
  Speaker 1: relies really crucially on the charge never changing. So that's
• 33:19
  Speaker 1: why that's such an important part of this argument.
• 33:22
  Speaker 2: Well, I'm excited to see a video of the Big Bang,
• 33:25
  Speaker 2: which Daniel clearly has, but let's take a little bit
• 33:30
  Speaker 2: of a break so I can hydrate before my mind
• 33:32
  Speaker 2: is blown. And then when we get back, Daniel's going
• 33:35
  Speaker 2: to explain exactly what happened during the Big Bang, leave
• 33:38
  Speaker 2: no detail undescribed. All right, Daniel, you promised, you promised
• 33:55
  Speaker 2: this big Bang? What happened there? What was up with that?
• 34:00
  Speaker 1: Think you may have oversold this maybe a little bit.
• 34:04
  Speaker 1: You're right that the argument is if we know the
• 34:07
  Speaker 1: charge of the universe when it began. Then we know
• 34:09
  Speaker 1: the charge of the universe now because it hasn't changed.
• 34:12
  Speaker 1: So do we know the charge of the universe when
• 34:14
  Speaker 1: it began? Well, do we know how the universe began?
• 34:17
  Speaker 1: Unfortunately we don't, right, and people think about the Big Bang,
• 34:21
  Speaker 1: is this moment fourteen billion years ago when the universe began?
• 34:25
  Speaker 1: But really things are much fuzzier than that. What we
• 34:28
  Speaker 1: do know is fourteen billion years ago the universe was
• 34:30
  Speaker 1: in some very hot and dense state. We know that
• 34:33
  Speaker 1: because we see how the universe is progressing over time.
• 34:37
  Speaker 1: The further back we are looking in time, so we
• 34:39
  Speaker 1: can see the history of the universe. It's literally written
• 34:41
  Speaker 1: in the night sky.
• 34:42
  Speaker 2: This is because light takes time to reach us, and
• 34:46
  Speaker 2: so we know based on the distance that it was, Like,
• 34:49
  Speaker 2: if stuff is closer, it's coming to us more recently
• 34:53
  Speaker 2: in time, and if stuff is further away, it's coming
• 34:56
  Speaker 2: to us further back in time.
• 34:58
  Speaker 1: Right, like from that direction is arriving now that left
• 35:01
  Speaker 1: a long long time ago. So the images we are
• 35:04
  Speaker 1: seeing when we look really really far away are in
• 35:06
  Speaker 1: the deep, deep past, and what they tell us is
• 35:09
  Speaker 1: that the universe is getting colder. As it gets older,
• 35:13
  Speaker 1: it gets more spread out, more dilute, it gets chiller.
• 35:16
  Speaker 1: And if you run that clock backwards in time, then
• 35:18
  Speaker 1: the universe is getting hotter as you get backwards, and
• 35:21
  Speaker 1: more dense. So the universe started in some very hot
• 35:24
  Speaker 1: dense state and then spread out over time. And people
• 35:27
  Speaker 1: often think of the Big Bang as some dot of
• 35:30
  Speaker 1: matter spreading out into empty space. But the more accurate
• 35:34
  Speaker 1: picture is that the universe was already infinite, already filled
• 35:38
  Speaker 1: with an infinite amount of hot, dense stuff everywhere, and
• 35:42
  Speaker 1: the Big Bang is the expansion of that space, space
• 35:45
  Speaker 1: being created between those particles spreading out to make those
• 35:49
  Speaker 1: things colder and more dilute. That's our picture of the
• 35:52
  Speaker 1: Big Bang. And that's as far back as we can go.
• 35:55
  Speaker 1: Our theories of physics work really, really well back to
• 35:58
  Speaker 1: that hot dense state. Understanding how it is banded and
• 36:00
  Speaker 1: cooled and formed stuff. Kittens and ice cream and lava
• 36:03
  Speaker 1: and hamsters and all that good stuff before that, we
• 36:06
  Speaker 1: just really don't know.
• 36:07
  Speaker 2: They don't mix particularly well those things anyway.
• 36:13
  Speaker 1: Kitten ice cream, oh my gosh, really.
• 36:15
  Speaker 2: And hamsters, they don't. They don't love lava.
• 36:18
  Speaker 1: You could put a nice piscatti run on top of
• 36:19
  Speaker 1: that scoop of kitten ice cream. Perfectly you should name
• 36:23
  Speaker 1: your kitten cookie instead of your dog. But the pla
• 36:26
  Speaker 1: is that we don't know where that came from, right,
• 36:28
  Speaker 1: And so there's ideas, you know, it could be that
• 36:31
  Speaker 1: it decayed from some other unknown field like the Inflanton field,
• 36:35
  Speaker 1: or it could be as a bubble of exotic stuff
• 36:37
  Speaker 1: which turned into our universe. We don't really know. And
• 36:41
  Speaker 1: here's where we get sort of like philosophical, and we say, well,
• 36:45
  Speaker 1: probably it was born and neutral, because what else makes sense?
• 36:49
  Speaker 2: Well, so if it's if we know it was super
• 36:52
  Speaker 2: hot and dense, is there something about heat and density
• 36:56
  Speaker 2: that could like tell us about the charge? Right, Like
• 37:00
  Speaker 2: do we know like if when we have really hot
• 37:03
  Speaker 2: dnse stuff, do we know the charge of those things?
• 37:06
  Speaker 2: And like could we somehow extrapolate like what is the
• 37:10
  Speaker 2: likely charge of like the it's like super super soup
• 37:17
  Speaker 2: of the initial universe.
• 37:20
  Speaker 1: Yeah, so here's where we get into the evidence. The
• 37:23
  Speaker 1: only theoretical argument we have is the universe should be
• 37:26
  Speaker 1: neutral because it only makes sense for it to be
• 37:28
  Speaker 1: born neutral. And we're pretty sure that if it was
• 37:30
  Speaker 1: born neutral, it's still neutral, Well, do we have any
• 37:32
  Speaker 1: evidence to back that up. We can't actually look at
• 37:35
  Speaker 1: pictures from the very very early universe and look for
• 37:38
  Speaker 1: hints to see if there was any overall positive or
• 37:41
  Speaker 1: negative charge, because that really does affect how things oscillate.
• 37:45
  Speaker 1: So the oldest images that we have, the earliest measurements
• 37:48
  Speaker 1: we can make of the early universe, are from about
• 37:51
  Speaker 1: three hundred and eighty thousand years after that very very hot,
• 37:54
  Speaker 1: dense state. That's when things cool down enough that like
• 37:57
  Speaker 1: protons and electrons start to hang out to get into
• 38:00
  Speaker 1: neutral atoms, and then the universe became transparent. Before that,
• 38:04
  Speaker 1: it was hot and dense and opaque like the center
• 38:07
  Speaker 1: of the sun. After that moment became more transparent like
• 38:10
  Speaker 1: the air which let's light through. So we can still
• 38:13
  Speaker 1: see life from that last moment of opacity still shining
• 38:17
  Speaker 1: around the universe. That's the cosmic microwave background radiation we
• 38:21
  Speaker 1: talked about a lot on the podcast, and by looking
• 38:23
  Speaker 1: at patterns in that light, we can tell how that
• 38:26
  Speaker 1: gas or how that last moment of plasma was oscillating,
• 38:30
  Speaker 1: was sloshing around. We see all sorts of cool patterns
• 38:32
  Speaker 1: in that plasma that tell us like how much dark
• 38:35
  Speaker 1: matter there was in the universe, how much normal matter,
• 38:37
  Speaker 1: how many photons? The imprint of the ripples and the
• 38:41
  Speaker 1: cosmic microwave background radiation are an extraordinarily precise way to
• 38:45
  Speaker 1: understand the dynamics of that early plasma, and we can
• 38:48
  Speaker 1: actually use that to answer the question of whether there
• 38:51
  Speaker 1: was any overall charge very very far back in their
• 38:54
  Speaker 1: early universe.
• 38:56
  Speaker 2: Okn, So how do we look at the charge of
• 38:59
  Speaker 2: this background radiation that we can actually observe on Earth.
• 39:03
  Speaker 1: Well, the lucky thing is electromagnetism is super duper powerful,
• 39:07
  Speaker 1: Like it's so much more powerful than gravity that if
• 39:11
  Speaker 1: there was any positive charge or any negative overall charge
• 39:15
  Speaker 1: in those clouds of gas, we would see it because
• 39:17
  Speaker 1: it would overwhelm gravity. Mostly. When we look at the
• 39:20
  Speaker 1: cosmic backroway background radiation and use it to think about
• 39:23
  Speaker 1: like the sloshing and the oscillation of that gas in
• 39:26
  Speaker 1: the early universe, we see gravitational effects. We see dark
• 39:29
  Speaker 1: matter pulling it in, we see particles passing through each other.
• 39:32
  Speaker 1: We can think about the acoustic waves of pressure in
• 39:35
  Speaker 1: that gas, so we can see the gravitational effects if
• 39:39
  Speaker 1: there was any charge left over, any positive or negative
• 39:42
  Speaker 1: we would see a really strong effect because it would
• 39:44
  Speaker 1: overwhelm all that gravity. And yet when we look at
• 39:46
  Speaker 1: the data, we only see gravity effects. We see no
• 39:49
  Speaker 1: indication there that there's any positive or any negative charge
• 39:53
  Speaker 1: in the early universe clouds.
• 39:54
  Speaker 2: Of gas that would indicate that maybe it is zero, right,
• 39:58
  Speaker 2: that it's neutral.
• 39:59
  Speaker 1: You can't actually pinning down all the way to zero.
• 40:01
  Speaker 1: You can do a set a limit and say, look,
• 40:04
  Speaker 1: if there is an excess of protons or electrons, it's
• 40:07
  Speaker 1: got to be a tiny fraction, because if it was
• 40:09
  Speaker 1: any bigger, we would have seen it. And numerically what
• 40:12
  Speaker 1: that means is that, like, if there's an overall positive
• 40:15
  Speaker 1: or negative charge, it has to be less than one
• 40:18
  Speaker 1: part in ten to the twenty nine, which means like
• 40:21
  Speaker 1: for every ten of the twenty nine protons, there's ten
• 40:24
  Speaker 1: to the twenty nine electrons plus one.
• 40:27
  Speaker 2: I may not know math, but I know that's that's tiny.
• 40:30
  Speaker 2: That's very small.
• 40:32
  Speaker 1: It's very small.
• 40:33
  Speaker 2: If you put that in as like a thing, I
• 40:36
  Speaker 2: couldn't see that thing.
• 40:39
  Speaker 1: That's true. It is very very small. It's not exactly zero,
• 40:41
  Speaker 1: and ten to the twenty nine is a big number,
• 40:43
  Speaker 1: but it's actually small compared to the total number of
• 40:46
  Speaker 1: electrons and protons, which remember is like ten to the eighty,
• 40:50
  Speaker 1: So it's possible that the universe has a slightly positive or.
• 40:53
  Speaker 2: Negative actually be infuriating. That would be so aggravating, And it.
• 40:57
  Speaker 1: Could actually be that they're like ten to the fifty
• 41:00
  Speaker 1: more protons than electrons in the universe, which would still
• 41:03
  Speaker 1: be a tiny fraction of the ten to the eighty
• 41:06
  Speaker 1: protons and electrons in the universe. So that's what we
• 41:09
  Speaker 1: can learn from the cosmic microwave background radiation. But we
• 41:12
  Speaker 1: can keep fast forwarding in time for the universe and
• 41:14
  Speaker 1: look for effects in other dynamics, other structure that was
• 41:17
  Speaker 1: formed in the universe. That's actually a little bit more precise.
• 41:21
  Speaker 2: Okay, I like this because I hate the idea that
• 41:23
  Speaker 2: we would just leave it at like it could be
• 41:26
  Speaker 2: zero or maybe, you know, tend to the twenty ninth ish,
• 41:30
  Speaker 2: We don't know.
• 41:30
  Speaker 1: If you want definitive answers, cosmology is the wrong place
• 41:33
  Speaker 1: to look. So what happens next in the universe. The
• 41:37
  Speaker 1: protons and electrons have formed together to make hydrogen, then
• 41:41
  Speaker 1: that hydrogen fuses together very briefly like we're used to
• 41:45
  Speaker 1: thinking about fusion happening at the hearts of stars, which
• 41:48
  Speaker 1: formed hundreds of millions of years later. But for a
• 41:50
  Speaker 1: couple of minutes in the very early universe, things were
• 41:53
  Speaker 1: hot and dense enough that hydrogen could fuse together to
• 41:56
  Speaker 1: make heavier elements. It's like, briefly, the whole universe was
• 41:59
  Speaker 1: like the heart of a star, so that hydrogen made
• 42:02
  Speaker 1: some helium and very trace amounts of lithium. It didn't
• 42:05
  Speaker 1: last long enough to make anything heavier than that, and
• 42:08
  Speaker 1: the rate at which that happens tells us a huge
• 42:10
  Speaker 1: amount about the nature of reality at that moment, Like
• 42:13
  Speaker 1: we can measure the density of the protons at that
• 42:15
  Speaker 1: moment by the ratios of like how much helium was
• 42:18
  Speaker 1: made and how much lithium was made, because fusing two
• 42:21
  Speaker 1: protons together is really hard. You got to really push
• 42:24
  Speaker 1: them together with a lot of force. But you need
• 42:26
  Speaker 1: a huge amount of density in high temperature because protons
• 42:29
  Speaker 1: don't like to get together. They're both positively charged, they
• 42:31
  Speaker 1: repel each other. So you can learn a lot about
• 42:34
  Speaker 1: the density. And this is really precise science called Big
• 42:36
  Speaker 1: Bang nucleosynthesis that tells us a lot about the nature
• 42:40
  Speaker 1: of the universe back then, just by measuring these ratios,
• 42:43
  Speaker 1: the helium to hydrogen to lithium ratios, and it also
• 42:47
  Speaker 1: tells us about the positive and negative charges, because if
• 42:51
  Speaker 1: there was a bunch of extra protons flying around, that
• 42:54
  Speaker 1: would really change the rate of fusion, or if there
• 42:56
  Speaker 1: was a bunch of extra electrons flying around, because again
• 42:59
  Speaker 1: the electric force is really powerful and it would disrupt
• 43:02
  Speaker 1: or enhance the rate of the production of these heavier
• 43:05
  Speaker 1: elements in that moment. So by measuring these ratios, we
• 43:08
  Speaker 1: can get a limit on the total electric charge of
• 43:10
  Speaker 1: the universe now to one part in ten to the
• 43:13
  Speaker 1: thirty two, So it's like a thousand times more powerful
• 43:17
  Speaker 1: than the limit we get from the Cossack microwave background radiation.
• 43:20
  Speaker 2: Okay, so intellectually I understand this is amazing and that
• 43:24
  Speaker 2: the science behind this is I mean, it's incredible right
• 43:28
  Speaker 2: to be able to do this kind of like deduction
• 43:30
  Speaker 2: and to do this calculation to this level of precision,
• 43:34
  Speaker 2: and that tend to the thirty two is a lot
• 43:37
  Speaker 2: more than tend to the twenty ninth because that is
• 43:40
  Speaker 2: the nature of exponential growth. And yet to my little
• 43:44
  Speaker 2: monkey brain, I'm like, these numbers are essentially the same,
• 43:48
  Speaker 2: and I like it's just real small, but the uncertainty
• 43:52
  Speaker 2: is still there. It's just real small.
• 43:56
  Speaker 1: No, that's fair. I mean, on one hand, these are
• 43:57
  Speaker 1: very very precise studies, really incredible. We can learn this
• 44:00
  Speaker 1: much about the early universe from this trace information. And
• 44:04
  Speaker 1: on the other hand, it's nowhere near getting us close
• 44:07
  Speaker 1: to zero to understanding whether the universe is actually overall neutral.
• 44:11
  Speaker 1: But we can do even better. We can look in
• 44:14
  Speaker 1: the modern day universe to see if there are currents
• 44:17
  Speaker 1: flowing in the whole universe, like if the universe had
• 44:21
  Speaker 1: a bunch of positive charge here or a bunch of
• 44:23
  Speaker 1: negative charge there, if there was an imbalance in the
• 44:26
  Speaker 1: protons and electrons, that would create huge electric fields throughout
• 44:30
  Speaker 1: the whole universe, just the way like electrons and protons
• 44:33
  Speaker 1: can create electric fields in the atom or in materials
• 44:36
  Speaker 1: or between like your sock and the floor. If you
• 44:38
  Speaker 1: have an overall excess of electrons or protons somewhere, which
• 44:41
  Speaker 1: you'd have to have if there was an imbalance, then
• 44:44
  Speaker 1: you'd have electric fields. And we think we could see
• 44:46
  Speaker 1: that because those electric fields would steer cosmic rays. Cosmic
• 44:50
  Speaker 1: rays are just charged particles that hit the Earth like
• 44:52
  Speaker 1: tiny little asteroids like protons or sometimes heavier elements hit
• 44:56
  Speaker 1: the Earth, and we can measure them in our atmosphere
• 44:58
  Speaker 1: and using all sorts of cool time technology, and by
• 45:01
  Speaker 1: studying the patterns of those cosmic rays, we can use
• 45:03
  Speaker 1: them as probes of these cosmic electric fields and try
• 45:07
  Speaker 1: to figure out whether there is an overall positive or
• 45:10
  Speaker 1: negative charge to the universe.
• 45:12
  Speaker 2: Okay, I mean that makes sense, right. You've got if
• 45:16
  Speaker 2: you have an imbalance that would cause this sort of
• 45:19
  Speaker 2: like sloshing of fields, and then we would see that
• 45:23
  Speaker 2: from here in cosmic rays that we receive.
• 45:26
  Speaker 1: Yeah, and we've studied these cosmic rays. They're super interesting
• 45:28
  Speaker 1: for lots of other reasons, like what's even making them?
• 45:31
  Speaker 1: How do they get such high energy? The patterns of
• 45:34
  Speaker 1: them in the sky are very strange. We've analyzed them carefully,
• 45:36
  Speaker 1: and there's no evidence for an overall positive or negative
• 45:39
  Speaker 1: charge of the universe from cosmic rays. And we can
• 45:42
  Speaker 1: set a limit of one part in ten to the
• 45:44
  Speaker 1: thirty nine. So this is jumping up like seven more
• 45:48
  Speaker 1: orders of magnitude, improving this result by factor of ten million.
• 45:52
  Speaker 1: I hope that impresses you, Katie.
• 45:54
  Speaker 2: Look again, intellectually, this is incredible, nothing but respect for
• 45:58
  Speaker 2: these scientists, And I understand that it is significant that
• 46:02
  Speaker 2: we keep increasing the precision of this estimation, meaning that
• 46:08
  Speaker 2: it looks more and more like it could probably be
• 46:12
  Speaker 2: zero or neutral. And yet you know, again there's a
• 46:16
  Speaker 2: little uncertainty, and the part of my brain that is
• 46:20
  Speaker 2: still a monkey does not like it.
• 46:24
  Speaker 1: Well, you're right, we still don't actually know the answer,
• 46:26
  Speaker 1: and that's about as good as we can do so far.
• 46:29
  Speaker 1: We have other ways to look for electric fields, like
• 46:31
  Speaker 1: to look at the gravitational structure of the universe. You know,
• 46:34
  Speaker 1: if galaxies were overall positive or overall negative, it would
• 46:38
  Speaker 1: change the way they pull and tug on each other,
• 46:40
  Speaker 1: the way they move in galaxy clusters. And that's a
• 46:43
  Speaker 1: powerful way to look for excess charges, but it's not
• 46:45
  Speaker 1: as powerful as the cosmic ray limits. So those are
• 46:48
  Speaker 1: our best measurements so far about the overall neutrality of
• 46:51
  Speaker 1: the universe, about one part in ten to the thirty nine,
• 46:54
  Speaker 1: which is only like, you know, forty orders of magnitude
• 46:57
  Speaker 1: away from having a definitive answer to this question.
• 47:01
  Speaker 2: I feel like at a certain point it's going to
• 47:04
  Speaker 2: be less of a math problem and more of a
• 47:06
  Speaker 2: problem to solve in therapy or I learned just to
• 47:09
  Speaker 2: accept uncertainty.
• 47:11
  Speaker 1: Well, I think this is a really fascinating question because
• 47:14
  Speaker 1: we have a very strong answer from the theoretical side.
• 47:16
  Speaker 1: There's a very strong bias that says the universe should
• 47:20
  Speaker 1: be neutral when it was created, because again, no other
• 47:22
  Speaker 1: answer makes sense, and that's really just very philosophical. There's
• 47:26
  Speaker 1: no very strong theoretical argument there other than just like
• 47:29
  Speaker 1: a preference for zero is the most natural answer if
• 47:32
  Speaker 1: you have to pick one. But then the theory tells
• 47:34
  Speaker 1: us that once you picked one for the early universe,
• 47:36
  Speaker 1: once you create a universe, its charge is fixed. That
• 47:39
  Speaker 1: will just never change. And that's really cool experimentally because
• 47:43
  Speaker 1: it means we can measure the charge of the universe anytime.
• 47:46
  Speaker 1: We can measure it today. We can look for evidence
• 47:48
  Speaker 1: in the early universe, we can look for a thousand
• 47:50
  Speaker 1: years after the universe which created. We have lots and
• 47:52
  Speaker 1: lots of opportunities to make these measurements. So far, these
• 47:55
  Speaker 1: measurements tell us that the universe is mostly neutral, down
• 47:59
  Speaker 1: to about one part heart intended the thirty nine, which
• 48:02
  Speaker 1: I think is pretty good. But Katie's unimpressed. Maybe one
• 48:05
  Speaker 1: day we'll come up with another technique that lets us
• 48:07
  Speaker 1: push these measurements even further so we can get a
• 48:10
  Speaker 1: deeper answer to this question.
• 48:12
  Speaker 2: Yeah, I mean, you know, And it's also a good lesson, like,
• 48:15
  Speaker 2: think real hard before you create your own universe, because
• 48:17
  Speaker 2: once you pick that charge, you can't change it later.
• 48:21
  Speaker 1: That's you are literally stuck with it. There's no changing
• 48:24
  Speaker 1: the electric charge of the universe. But that's also not
• 48:27
  Speaker 1: something we understand. Right, we don't understand how the universe
• 48:30
  Speaker 1: was made or what its charge was in the beginning.
• 48:32
  Speaker 1: We also still don't really understand why charge is conserved.
• 48:36
  Speaker 1: This again, is just something we've observed. We've done a
• 48:39
  Speaker 1: zillion particle physics experiments looking for violation as rule and
• 48:42
  Speaker 1: never seen one. That doesn't mean that it doesn't happen occasionally, right,
• 48:46
  Speaker 1: We have these theoretical reasons that suggest that photons exist
• 48:50
  Speaker 1: to preserve electric charge, but again we don't really understand
• 48:53
  Speaker 1: why that is, and so it's possible that sneakily the
• 48:56
  Speaker 1: universe is changing its little bits of charge here and
• 48:59
  Speaker 1: there very occasionally under our newses.
• 49:02
  Speaker 2: My therapist is going to be so confused when I
• 49:04
  Speaker 2: talk to her about like and then Daniel said that
• 49:06
  Speaker 2: we can't know if the charge doesn't change. I don't
• 49:10
  Speaker 2: know what to believe anymore. Who do I trust?
• 49:12
  Speaker 1: I think you should just sit with your dog cookie
• 49:14
  Speaker 1: and have a nice cookie, and you have the therapy
• 49:16
  Speaker 1: right there.
• 49:17
  Speaker 2: That is the best therapy, the buye cookie therapy.
• 49:22
  Speaker 1: All right, Well, thanks everyone for joining us on this
• 49:24
  Speaker 1: exploration of the nature of the universe, not just its size,
• 49:28
  Speaker 1: not just its structure, but it's overall charged and what
• 49:31
  Speaker 1: that tells us about the nature of reality and what's
• 49:34
  Speaker 1: important to the universe For reasons we still don't understand.
• 49:37
  Speaker 1: The charge seems to be a fundamentally conserved quantity in
• 49:40
  Speaker 1: the universe, but we still don't actually know what the
• 49:42
  Speaker 1: total charge of the universe is. Thanks very much Kennie
• 49:45
  Speaker 1: for joining us today, and thanks everybody for listening.
• 49:48
  Speaker 2: Thanks for having me.
• 49:49
  Speaker 1: Tune in next time for more science and curiosity. Come
• 49:56
  Speaker 1: find us on social media where we answer questions and
• 49:59
  Speaker 1: post videos. We're on Twitter, Discorg, Insta, and now TikTok.
• 50:04
  Speaker 1: Thanks for listening, and remember that Daniel and Jorge Explain
• 50:07
  Speaker 1: the Universe is a production of iHeartRadio. For more podcasts
• 50:11
  Speaker 1: from iHeartRadio, visit the iHeartRadio, app, Apple podcasts, or wherever
• 50:16
  Speaker 1: you listen to your favorite shows.