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What is the electrical charge of the moon? · Daniel and Kelly’s Extraordinary Universe

• 0:08
  Speaker 1: Hey, Daniel, what's your feeling about the Moon?
• 0:11
  Speaker 2: I guess I don't have that many strong feelings. Does
• 0:14
  Speaker 2: anyone Do you like it? Do you dislike it? I mean,
• 0:16
  Speaker 2: I guess I'm generally pro moon, although if it's made
• 0:19
  Speaker 2: out of white chocolate, I'm not going to be very
• 0:21
  Speaker 2: happy about it.
• 0:21
  Speaker 1: Oh what if it was would you want to nuke
• 0:24
  Speaker 1: it out of the sky?
• 0:25
  Speaker 2: Oh? Man, that sounds like a disaster. It would cause
• 0:28
  Speaker 2: a shower of molten white chocolate all over the earth.
• 0:31
  Speaker 1: Yeah, a lot of people would be happy.
• 0:33
  Speaker 2: That sounds like a disaster movie.
• 0:35
  Speaker 1: To me, it sounds like you have really charged feelings
• 0:37
  Speaker 1: about the moon and white.
• 0:38
  Speaker 2: Chocolate, both positive and negative.
• 0:56
  Speaker 1: Hi am Jorhemy Cartoonist'm the author of Oliver's Great Big Universe.
• 1:00
  Speaker 2: Hi, I'm Daniel. I'm a particle physicist and a professor
• 1:03
  Speaker 2: at UC Irvine. And you couldn't pay me enough white
• 1:06
  Speaker 2: chocolate to take a trip to the moon.
• 1:07
  Speaker 1: Can we pay you some money to eat white chocolate?
• 1:09
  Speaker 2: I guess it depends on the amount of white chocolate
• 1:11
  Speaker 2: and the amount of money.
• 1:12
  Speaker 1: Wait, you would have wanted to go to the moon?
• 1:14
  Speaker 1: Why not?
• 1:14
  Speaker 2: I mean, I don't take trips to Antarctica, and I'm
• 1:16
  Speaker 2: pretty sure the Moon is like less cozy than Antarctica.
• 1:21
  Speaker 1: It's not about coziness, It's about the adventure, you know,
• 1:24
  Speaker 1: excitement being someplace interesting.
• 1:26
  Speaker 2: Yeah again, still don't take a lot of trips to
• 1:28
  Speaker 2: Antarctica for the same reason.
• 1:30
  Speaker 1: Have you been to Antarctica? How do you know you
• 1:31
  Speaker 1: won't like it.
• 1:32
  Speaker 2: I've never been to Antarctica, but I've been to some
• 1:34
  Speaker 2: places that are sort of Antarctica adjacent, and I wasn't
• 1:37
  Speaker 2: a fan.
• 1:38
  Speaker 1: I've been to the Arctics Circle that was pretty exciting.
• 1:41
  Speaker 1: I've been on a glacier.
• 1:42
  Speaker 2: I know. I'm trying to hook you up with a
• 1:44
  Speaker 2: trip to Antarctica to visit the physics experiments there, but
• 1:47
  Speaker 2: no luck yet.
• 1:47
  Speaker 1: M Are you just trying to get rid of me?
• 1:51
  Speaker 1: Are you hoping that some sort of a freak accident
• 1:54
  Speaker 1: will happen while I'm there.
• 1:55
  Speaker 2: I think that's a conversation you should have with your
• 1:56
  Speaker 2: therapist about your paranoia. I thought you wanted to visit
• 1:59
  Speaker 2: the South Pole. I don't know.
• 2:00
  Speaker 1: There's all very suspicious, Daniel. I mean, of all the
• 2:03
  Speaker 1: places you could send me to Hawaii, Fiji, do you
• 2:06
  Speaker 1: want to send me to the most remote place on Earth.
• 2:08
  Speaker 2: There's also an awesome physics experiment in the south of France.
• 2:11
  Speaker 2: Maybe you want to visit that one.
• 2:12
  Speaker 1: Yeah, let's do it. I'll take it. Is a podcast paying.
• 2:16
  Speaker 2: Everybody chip in crowdsource Jorgees trip to the South of France.
• 2:19
  Speaker 2: We'll see how many contributions we get.
• 2:20
  Speaker 1: There you go, We'll kickstarted. But anyways, welcome to our podcast.
• 2:24
  Speaker 1: Daniel and Jorge Explain the Universe, a production of iHeartRadio.
• 2:27
  Speaker 2: In which we get all charged up about the mysteries
• 2:29
  Speaker 2: of the universe. We are very positive about the idea
• 2:33
  Speaker 2: that humans can understand the nature of the universe that
• 2:36
  Speaker 2: we live in, and not just a few humans operating
• 2:39
  Speaker 2: on the forefront of science. Everybody. We love taking these
• 2:42
  Speaker 2: crazy ideas that scientists have developed and explaining all of
• 2:45
  Speaker 2: them to you.
• 2:45
  Speaker 1: It's right because we are attracted to the deep mysteries
• 2:48
  Speaker 1: of the universe, and we are also repelled by our
• 2:50
  Speaker 1: deep ignorance of the things. We don't know about how
• 2:53
  Speaker 1: things work.
• 2:53
  Speaker 2: But what we definitely do know is that the universe
• 2:56
  Speaker 2: is controlled by forces. There are pushes, there are pulls,
• 3:00
  Speaker 2: there are tugs. Everything that happens out there in the
• 3:02
  Speaker 2: universe is the result of forces in balance and out
• 3:05
  Speaker 2: of balance.
• 3:06
  Speaker 1: Wait, are you sure about that? I mean, I feel
• 3:08
  Speaker 1: like we need for a long time about the force
• 3:10
  Speaker 1: of gravity, but now I hear that there's no just
• 3:12
  Speaker 1: a thing as the gravitational force.
• 3:14
  Speaker 2: You're right, of course, that gravity is not a force.
• 3:16
  Speaker 2: It's just the curvature of space time, which gives the
• 3:19
  Speaker 2: illusion of a force if you're not aware that space
• 3:22
  Speaker 2: is curved in front of you and causing things to
• 3:25
  Speaker 2: move in a way you might not expect. We can
• 3:27
  Speaker 2: still actually describe a lot of that in terms of
• 3:29
  Speaker 2: pseudo forces. So for the spirit of today's conversation about
• 3:33
  Speaker 2: pushes and pulls and what's tugging on the moon and
• 3:35
  Speaker 2: what's not, doesn't really make a difference if gravity is
• 3:38
  Speaker 2: a force or the curvature of space time.
• 3:41
  Speaker 1: I wonder it could it be that we eventually find
• 3:43
  Speaker 1: out that the other forces in nature are also just
• 3:46
  Speaker 1: distortions of space and time or are we pretty sure
• 3:49
  Speaker 1: those are forces forces?
• 3:50
  Speaker 2: No, you're absolutely right, and that is an active idea
• 3:53
  Speaker 2: people are working on. Einstein spent many, many years trying
• 3:55
  Speaker 2: to explain electromagnetism in terms of additional curvature of space time.
• 4:00
  Speaker 2: He thought maybe that force is actually also a pseudo force,
• 4:04
  Speaker 2: just the result of space being curved in additional ways.
• 4:07
  Speaker 2: He never made it work, and one reason is that
• 4:09
  Speaker 2: he didn't understand the weak force, which is crucially related
• 4:12
  Speaker 2: to electromagnetism, So he sort of didn't have the whole picture.
• 4:15
  Speaker 2: But there are people working on that right now. They
• 4:17
  Speaker 2: just haven't succeeded yet.
• 4:19
  Speaker 1: I guess Einstein felt he was kind of forcing it
• 4:21
  Speaker 1: at some point. He didn't want to push it.
• 4:23
  Speaker 2: I think he went around the wrong curve.
• 4:25
  Speaker 1: He felt like he couldn't pull it off.
• 4:28
  Speaker 2: It wasn't a grave enough matter.
• 4:29
  Speaker 1: But it does seem like in our everyday lives, like
• 4:31
  Speaker 1: things are governed by these laws of nature that seem
• 4:34
  Speaker 1: to pull and push on things. And that's kind of
• 4:36
  Speaker 1: what physics it's all about, right, the push and pull
• 4:39
  Speaker 1: of the universe.
• 4:39
  Speaker 2: That's right. And the universe as we see it is
• 4:41
  Speaker 2: shaped by lots of different forces. Stuff in the universe
• 4:44
  Speaker 2: is mostly built out of the more powerful forces, the
• 4:47
  Speaker 2: strong force, electromagnetism. But the overall shape of the universe,
• 4:52
  Speaker 2: the way the Solar System is, the shape of the Earth,
• 4:55
  Speaker 2: the structure of the galaxy and beyond is mostly dominated
• 4:58
  Speaker 2: by the weakest force, gravity.
• 5:00
  Speaker 1: As our gravity is what gives the universe its structure.
• 5:03
  Speaker 1: If it wasn't for gravity, we wouldn't have planets, right,
• 5:05
  Speaker 1: or suns or galaxies, and we wouldn't be here. I mean,
• 5:08
  Speaker 1: be nice to be lighter than what we are, but
• 5:12
  Speaker 1: without gravity, we and none of us would exist.
• 5:14
  Speaker 2: That's right. It's gravity that causes the Sun to burn
• 5:17
  Speaker 2: because it squeezes all that gas together, giving it the
• 5:20
  Speaker 2: high temperature and density needed to ignite fusion. It's gravity
• 5:24
  Speaker 2: that forms the structure of the Earth. It's gravity that's
• 5:27
  Speaker 2: formed the Moon. It's gravity that's formed everything that we
• 5:29
  Speaker 2: see out there in the universe. But that doesn't mean
• 5:31
  Speaker 2: that gravity is the only force at play in our
• 5:34
  Speaker 2: Solar system.
• 5:35
  Speaker 1: Yeah, there are other forces, some of which play an
• 5:39
  Speaker 1: equally important role in our existence. If it wasn't for
• 5:42
  Speaker 1: the electromagnetic force, like, none of our atoms would hold together,
• 5:45
  Speaker 1: and so we also wouldn't be here.
• 5:47
  Speaker 2: That's right. You're basically built out of the electromagnetic force.
• 5:50
  Speaker 2: All of your atoms and molecules are bonded together using
• 5:53
  Speaker 2: electrons and electromagnetism. So basically every structure you're familiar with,
• 5:57
  Speaker 2: is an electromagnetic structure.
• 5:59
  Speaker 1: I feel like we're saying we're basically everything. Everything is
• 6:02
  Speaker 1: everything made out of everything, due to everything.
• 6:05
  Speaker 2: It is an incredible balance of all those forces.
• 6:08
  Speaker 1: Yeah, and sometimes that force pulls and pushes on things
• 6:11
  Speaker 1: in ways that you don't quite expect.
• 6:13
  Speaker 2: And so we think that gravity is the dominant force
• 6:16
  Speaker 2: remaining in the solar system, but that's not always the case.
• 6:19
  Speaker 1: And so on the podcast, we'll be tackling the question
• 6:27
  Speaker 1: what's the electrical charge of the moon? Interesting question, like
• 6:34
  Speaker 1: the moon has as a plug in it?
• 6:38
  Speaker 2: Is the Moon a battery? And if we travel there,
• 6:40
  Speaker 2: can we use it to recharge our phone?
• 6:42
  Speaker 1: There you go, that'd be important. Does it have a
• 6:44
  Speaker 1: USBC connector a USB connector lightning port, the USB Moon
• 6:49
  Speaker 1: connector Yeah, that's what I want to know before you
• 6:53
  Speaker 1: send me to the Moon.
• 6:54
  Speaker 2: You know, the way it is with USB, there's always
• 6:56
  Speaker 2: some new shape you've never seen before.
• 6:58
  Speaker 1: Yeah, Well, hopefully the Moon has a stand under plug.
• 7:00
  Speaker 1: But this is an interesting question to ask about the moon,
• 7:03
  Speaker 1: like the idea that the moon has a charge at all.
• 7:07
  Speaker 2: Yeah, because we're very familiar with the Moon having a mass,
• 7:09
  Speaker 2: which is sort of like a gravitational charge. You you're
• 7:12
  Speaker 2: thinking about gravity as a force and a Newtonian sense,
• 7:15
  Speaker 2: but it's weird to think about the Moon having like
• 7:17
  Speaker 2: an electric charge, like it being overall positive or negative.
• 7:21
  Speaker 1: Hmm. Well, I'm positive we'll get to the bottom of this,
• 7:25
  Speaker 1: but as usual, we were wondering how many people out
• 7:27
  Speaker 1: there had thought about the Moon having a charge or
• 7:30
  Speaker 1: what that charge could be.
• 7:31
  Speaker 2: Thanks very much to everybody who volunteers for this fun
• 7:34
  Speaker 2: segment of the podcast. One of my favorites. I love
• 7:36
  Speaker 2: hearing your voices. Please join the group right to meet
• 7:39
  Speaker 2: at questions at Danielanjorge dot com.
• 7:41
  Speaker 1: So think about it for a second. Do you think
• 7:43
  Speaker 1: the Moon has a charge? Here's what people had to say.
• 7:46
  Speaker 3: I would think planets and moons get their charge from
• 7:49
  Speaker 3: their cores, you know. In Earth's case, I think the
• 7:52
  Speaker 3: iron core gives it a magnetic field. But then again,
• 7:55
  Speaker 3: I guess the charges would cancel out and make it neutral.
• 7:58
  Speaker 2: So I don't know.
• 8:00
  Speaker 3: I don't think the Moon has a core or an
• 8:01
  Speaker 3: electric field as far as I know, so I guess
• 8:03
  Speaker 3: maybe you can call that neutral too.
• 8:04
  Speaker 4: I feel like the Moon should have a total electrical
• 8:07
  Speaker 4: charge of zero. It's probably different locally depending on what's
• 8:12
  Speaker 4: getting hit by the solar wind and being ionized at
• 8:15
  Speaker 4: the dust particular level, but that's probably a zero overall.
• 8:19
  Speaker 5: I'm not sure about the electric charge of the Moon
• 8:23
  Speaker 5: because it doesn't have more to love in it, I think,
• 8:29
  Speaker 5: but since it's spinning, it might have a really small,
• 8:34
  Speaker 5: undetectable amount. But I'm not sure about it.
• 8:37
  Speaker 6: Otherwise, I would have guessed that the electrical charge of
• 8:40
  Speaker 6: the Moon would be zero because I thought that all
• 8:45
  Speaker 6: electrical charge balanced out. But you're asking the question, so
• 8:49
  Speaker 6: I'm guessing it's not zero. I'm not sure though. Maybe
• 8:53
  Speaker 6: it has something to do with the Earth's magnetic field.
• 8:56
  Speaker 6: But I'm really not sure. I'm not too sure what
• 9:00
  Speaker 6: the charge of the Moon would be, but I imagine
• 9:02
  Speaker 6: it has the same charge as the Earth.
• 9:05
  Speaker 1: I believe that the electrical charge of the Moon is zero,
• 9:08
  Speaker 1: just us on Earth. All the positive and negative charges
• 9:11
  Speaker 1: should balance, all right, some charge answers here.
• 9:16
  Speaker 2: Consensus seems to be a zero charge for the Moon.
• 9:19
  Speaker 1: Well, it's not positive or negative. It's just kind of there.
• 9:23
  Speaker 2: The Moon just neutral. Just kind of me.
• 9:29
  Speaker 1: Just kind of mad, as the kids say these days.
• 9:34
  Speaker 1: But the moon is a pretty interesting object out in
• 9:37
  Speaker 1: our night sky. It's big, it's about the quarter of
• 9:40
  Speaker 1: the size and diameter.
• 9:41
  Speaker 2: Of the Earth, right, Yeah, I think that sounds right.
• 9:44
  Speaker 1: Yeah, And it's out there in orbit around the Earth.
• 9:46
  Speaker 1: And so the question is does it have an electrical charge?
• 9:48
  Speaker 1: Why would it have an electrical charge? Or should it
• 9:51
  Speaker 1: have an electrical charge?
• 9:52
  Speaker 2: I think the listeners had the right spirit. That ended
• 9:55
  Speaker 2: up mostly getting the wrong answer because a simple model
• 9:59
  Speaker 2: of the solar system suggests that it shouldn't have any charge,
• 10:02
  Speaker 2: that it should be basically neutral.
• 10:04
  Speaker 1: Well, maybe let's take a step back and talk about
• 10:06
  Speaker 1: the charge of things in general, Like do I have
• 10:08
  Speaker 1: a charge? An overall charge me like my body? Or
• 10:13
  Speaker 1: I guess where does a charge come from? Do I
• 10:15
  Speaker 1: have to add up all my electrons and then add
• 10:17
  Speaker 1: up all my protons and if there's an imbalance, then
• 10:19
  Speaker 1: I have an overall charge? Is that kind of what
• 10:21
  Speaker 1: having a charge means?
• 10:23
  Speaker 2: Yeah, You're made out of charged objects, the quarks, the
• 10:25
  Speaker 2: electrons that are in your body. They all have electric charges,
• 10:29
  Speaker 2: and some of them are positive and some of them
• 10:31
  Speaker 2: are negative, and so you add them all up. It's
• 10:34
  Speaker 2: like a big accounting and if you have more positives
• 10:36
  Speaker 2: the negatives. Then you're positively charged, and you're made up
• 10:39
  Speaker 2: of charged out of the molecules. Sometimes you have ions
• 10:42
  Speaker 2: inside your body which have electrical charges, but the electromagnetic
• 10:46
  Speaker 2: force is very, very powerful, and so it tends to
• 10:48
  Speaker 2: try to neutralize things.
• 10:50
  Speaker 1: But would you say that's an overall way to define
• 10:53
  Speaker 1: my charge or define the charge of something like if
• 10:56
  Speaker 1: it has more electrons than protons, which are made out
• 10:59
  Speaker 1: of quarks, then it has a negative charge.
• 11:02
  Speaker 2: Yeah. That's the definition of the charge of an object
• 11:05
  Speaker 2: is the sum of all the charges of its particles.
• 11:08
  Speaker 1: So if I have excess electrons somehow inside of me,
• 11:11
  Speaker 1: then I'm going to be negative charge, which means that
• 11:13
  Speaker 1: if you put me in front of a whole bunch
• 11:15
  Speaker 1: of electrons, am I going to be repelled by those electrons?
• 11:17
  Speaker 2: Yeah? Exactly. If you're negatively charged and then like a
• 11:20
  Speaker 2: cloud of electrons comes by, you're going to be repelled
• 11:23
  Speaker 2: from those electrons and they will be repelled by you.
• 11:26
  Speaker 2: Or if a cloud of protons comes by, you would
• 11:29
  Speaker 2: be attracted to those protons and they would be attracted
• 11:31
  Speaker 2: to you. And that's sort of the reason why most
• 11:34
  Speaker 2: stuff in the universe is very close to electrically neutral,
• 11:38
  Speaker 2: because electromagnetism is very strong, and if you do have
• 11:40
  Speaker 2: an overall charge, it tends to cancel itself out by
• 11:43
  Speaker 2: slurping up the opposite charge.
• 11:45
  Speaker 1: Right Like, if I have just a whole bunch of
• 11:47
  Speaker 1: electrons floating in space, I guess, first of all, they
• 11:49
  Speaker 1: would repel each other and fly away from each other.
• 11:52
  Speaker 1: But second of all, they would probably attract protons from
• 11:54
  Speaker 1: around them, and then they would quickly become neutral in
• 11:57
  Speaker 1: terms of charge exactly.
• 11:58
  Speaker 2: And that's just what happened in our universe when things
• 12:01
  Speaker 2: cooled down very early on. There were protons and there
• 12:05
  Speaker 2: were electrons, and they were all flying around. The whole
• 12:07
  Speaker 2: universe was charged. It was a plasma, which is just
• 12:10
  Speaker 2: a gas of charged particles. We think overall it was neutral,
• 12:14
  Speaker 2: but like individual electrons and protons of course had charge,
• 12:17
  Speaker 2: but they also had a lot of energy, were moving
• 12:19
  Speaker 2: really really fast, too fast for electromagnetism to sort of
• 12:22
  Speaker 2: capture them. But then when the universe cooled down, eventually
• 12:26
  Speaker 2: they were captured by each other, and protons electrons came
• 12:29
  Speaker 2: together to make neutral hydrogen. Then the whole universe was
• 12:32
  Speaker 2: filled with neutral gas.
• 12:34
  Speaker 1: Oh, that's an interesting question. Is the universe overall charge? Like,
• 12:38
  Speaker 1: is the total number of universal electrons the same as
• 12:41
  Speaker 1: a number of protons?
• 12:43
  Speaker 2: Yeah, great question. We don't know. We think that charge
• 12:46
  Speaker 2: is concerned in the universe, meaning it can't change. So
• 12:49
  Speaker 2: when the universe was born, there was a number which
• 12:51
  Speaker 2: is a total charge and that hasn't ever changed. We
• 12:54
  Speaker 2: think probably that was zero just due to symmetry arguments,
• 12:57
  Speaker 2: but the whole thing is very fuzzy.
• 12:59
  Speaker 1: And poorly now probably zero. Interesting.
• 13:02
  Speaker 2: Yeah, in the same way that we think like matter
• 13:04
  Speaker 2: and antimatter were made at the same rates in the
• 13:06
  Speaker 2: very early universe, although now we have a lot more
• 13:08
  Speaker 2: matter than antimatter, which is not something we understand. We
• 13:11
  Speaker 2: think that positrons and electrons were made at the same
• 13:14
  Speaker 2: rate in the early universe, that we started overall with
• 13:17
  Speaker 2: zero charge and created equal amounts of positive and negative
• 13:20
  Speaker 2: charge particles.
• 13:22
  Speaker 1: All right, So now let's get to the moon. And
• 13:23
  Speaker 1: now the question we're asking today is is the moon
• 13:26
  Speaker 1: positively or negatively charge overall? And you said that the
• 13:31
  Speaker 1: simple model of the moon says that it should be neutral,
• 13:33
  Speaker 1: So why is that?
• 13:34
  Speaker 2: Well, go back to our simple history of the universe.
• 13:37
  Speaker 2: The universe is filled with neutral gas. And what happened
• 13:39
  Speaker 2: after that is gravity took over. Right, Electromagnetism is neutralized out,
• 13:43
  Speaker 2: it's not really pushing and pulling on everything anymore. And
• 13:46
  Speaker 2: now gravity, the weakest force by huge amount, right, like
• 13:50
  Speaker 2: trillions and trillions of times weaker than electromagnetism, finally has
• 13:54
  Speaker 2: a chance to influence things. And it takes millions and
• 13:56
  Speaker 2: billions of years, but it pulls together planets and stars
• 13:59
  Speaker 2: and moons and forms the structure of the universe. The
• 14:03
  Speaker 2: weird thing about gravity is that it can't get canceled out.
• 14:06
  Speaker 2: There's only one charge for gravity. There's positive mass, there's
• 14:10
  Speaker 2: no negative mass, and so gravity forms this structure and
• 14:13
  Speaker 2: it's still the thing that dominates the universe because it's
• 14:17
  Speaker 2: still around. Unlike electromagnetism, it doesn't get neutralized or canceled out.
• 14:22
  Speaker 2: So the simple model of the universe is everything neutralizes
• 14:25
  Speaker 2: and then gravity takes over, and it's basically just the
• 14:28
  Speaker 2: gravity of neutral objects. So the Earth, the Moon, everything
• 14:31
  Speaker 2: should be basically neutral.
• 14:32
  Speaker 1: M I think you're saying that the Moon was basically
• 14:35
  Speaker 1: formed out of rocks, and way before those rocks formed
• 14:38
  Speaker 1: the Moon, those rocks were already electrically neutral.
• 14:41
  Speaker 2: Mmmmm exactly. And if the Moon had like a really
• 14:44
  Speaker 2: big positive charge and the Earth had a really big
• 14:47
  Speaker 2: negative charge, what would happen is that they would slur
• 14:50
  Speaker 2: particles off of each other and neutralize that.
• 14:52
  Speaker 1: Wait wait, wait, do you mean slur particles like pull
• 14:55
  Speaker 1: the electrons out of their rocks?
• 14:56
  Speaker 2: I mean you would hear this giant sucking sound like whew.
• 15:00
  Speaker 2: Quite literally.
• 15:01
  Speaker 1: I thought there was no sound in space. What kind
• 15:04
  Speaker 1: of misinformation are you giving out of here?
• 15:06
  Speaker 2: There is sound on Earth. And if the Moon was
• 15:08
  Speaker 2: sucking electrons off the Earth, we would hear it. Yeah,
• 15:11
  Speaker 2: the Moon was positively charged and the Earth was very
• 15:14
  Speaker 2: negatively charged, then the Moon would suck electrons off the
• 15:17
  Speaker 2: Earth until it was roughly in balance. Because electromagnetism is
• 15:21
  Speaker 2: very powerful.
• 15:22
  Speaker 1: Why would the Moon give up its electrons whatever they're
• 15:24
  Speaker 1: like embedded inside of their atoms.
• 15:26
  Speaker 2: I'm saying, if somehow the Moon was positively charged, like
• 15:29
  Speaker 2: I had a bunch of protons that didn't have electrons
• 15:31
  Speaker 2: to match it. They were hanging out on the Moon,
• 15:34
  Speaker 2: and the Earth had an excess of electrons like hanging
• 15:37
  Speaker 2: out in the atmosphere, then those electrons would get sucked
• 15:40
  Speaker 2: off the Earth to the Moon. The protons might also
• 15:43
  Speaker 2: get sucked off towards the Earth, but electrons are lighter,
• 15:46
  Speaker 2: so they would move further than the protons.
• 15:49
  Speaker 1: But I guess we're sticking to the model where the
• 15:51
  Speaker 1: Moon and the Earth were made out of neutral rocks,
• 15:54
  Speaker 1: and so that's what you're saying. That's a simple model
• 15:56
  Speaker 1: of how things got to be.
• 15:58
  Speaker 2: Yeah, so that simple model tells you that the Moon
• 16:01
  Speaker 2: should either be totally neutral or very close to neutral,
• 16:04
  Speaker 2: because anything else would have gotten balanced out early on,
• 16:07
  Speaker 2: and any large deviation from that later on would be
• 16:10
  Speaker 2: balanced out.
• 16:11
  Speaker 1: All right, Well, that's the first approximation. But as usual,
• 16:14
  Speaker 1: we know that physics and nature likes to surprise this.
• 16:16
  Speaker 1: So let's find out if that's really the case. Is
• 16:19
  Speaker 1: the Moon charged or not? Dig into that, But first
• 16:22
  Speaker 1: let's take a quick break. Right. We're asking the question
• 16:37
  Speaker 1: is the moon charged? Like is it amped up?
• 16:39
  Speaker 2: What else is going on with the moon to give
• 16:42
  Speaker 2: it positive or negative charges?
• 16:44
  Speaker 1: M All right, Well you said that the simple bottle
• 16:46
  Speaker 1: is that the Moon is made out of rocks, and
• 16:49
  Speaker 1: by the time those rocks got made, they were pretty
• 16:51
  Speaker 1: electrically neutral. Because that's kind of how the universe works,
• 16:55
  Speaker 1: and so what makes us think that maybe the universe
• 16:58
  Speaker 1: is not neutral.
• 16:58
  Speaker 2: Well, I think probably the whole universe is neutral. But
• 17:02
  Speaker 2: the Moon, it turns out, is more complex because that
• 17:04
  Speaker 2: simple story we told where you have like just a
• 17:07
  Speaker 2: bunch of gravitational rocks floating in space is not everything
• 17:10
  Speaker 2: that's happening in the Solar system. There's a lot more
• 17:13
  Speaker 2: going on, and specifically, the Sun is pumping out a
• 17:16
  Speaker 2: huge amount of positive and negatively charged particles. The solar wind,
• 17:21
  Speaker 2: which is essentially a stream of plasma flowing through the
• 17:24
  Speaker 2: Solar system, has big impact on everything.
• 17:26
  Speaker 1: You mean, we're all getting kind of showered by sun rays,
• 17:29
  Speaker 1: which not only include light, but also little tiny particles,
• 17:32
  Speaker 1: right like little quarks and electrons.
• 17:34
  Speaker 2: Exactly, mostly protons and electrons. A few positrons are also created,
• 17:38
  Speaker 2: and the Moon is going through this essentially soup of
• 17:41
  Speaker 2: electrons and protons, and that has a big effect on
• 17:44
  Speaker 2: the charge of the Moon.
• 17:46
  Speaker 1: But what isn't the Sun throwing out both positive and
• 17:49
  Speaker 1: negative charges. So basically the solar wind is neutral too,
• 17:54
  Speaker 1: isn't it.
• 17:55
  Speaker 2: The solar wind is overall neutral, But fascinatingly, the backside
• 17:59
  Speaker 2: of the moon tends to attract electrons more. Electrons stick
• 18:04
  Speaker 2: to the backside of the Moon more than protons do
• 18:07
  Speaker 2: because electrons are lighter and faster.
• 18:10
  Speaker 1: Wait wait, wait, wait, go back a little bit. What
• 18:11
  Speaker 1: does that mean. What do you mean electrons are different?
• 18:13
  Speaker 2: Well, electrons and protons have opposite charges, but they don't
• 18:17
  Speaker 2: have the same mass. Protons are much much more massive
• 18:20
  Speaker 2: than electrons are, right, and so that affects their velocity.
• 18:24
  Speaker 2: They come out of the Sun with the same energy,
• 18:26
  Speaker 2: but they have a lot more mass, so they're moving
• 18:28
  Speaker 2: much more slowly and it takes a bigger force to
• 18:31
  Speaker 2: accelerate them. And so electrons come out of the Sun
• 18:34
  Speaker 2: moving faster, and so there's just like a greater flux
• 18:36
  Speaker 2: of them hitting the Moon than the.
• 18:38
  Speaker 1: Protons, a greater flux.
• 18:40
  Speaker 2: So there's like more electrons per second per square meter
• 18:44
  Speaker 2: hitting the Moon than there are protons.
• 18:47
  Speaker 1: So wouldn't that mean that the Sun is making more
• 18:49
  Speaker 1: electrons than protons.
• 18:50
  Speaker 2: It's making the same number. But because the electrons are faster,
• 18:53
  Speaker 2: more of than are getting out to the moon. Like,
• 18:55
  Speaker 2: the protons don't have as much energy, so they don't
• 18:57
  Speaker 2: always get out to the moon, and they certainly don't
• 18:59
  Speaker 2: get out as rapidly.
• 19:01
  Speaker 1: Wait wait, wait, so you're saying that, what do you mean,
• 19:03
  Speaker 1: like some of the protons don't make it out to
• 19:04
  Speaker 1: the moon, like they get stuck somewhere.
• 19:06
  Speaker 2: Some of them get stuck. They just like exist in
• 19:08
  Speaker 2: the outer layers of the Sun.
• 19:10
  Speaker 1: Like the Sun is punet electrons and protons. But some
• 19:14
  Speaker 1: of the protons that don't get very far they maybe
• 19:16
  Speaker 1: get stuck back into the Sun you're saying, or they
• 19:18
  Speaker 1: get it's trapped into orbit with the Sun.
• 19:20
  Speaker 2: Yeah, exactly. And there are electrons and protons that do
• 19:23
  Speaker 2: make it out there by the Moon. But again the
• 19:25
  Speaker 2: electrons are moving faster and so they just tend to
• 19:28
  Speaker 2: hit the Moon more.
• 19:29
  Speaker 1: But then what would that mean that the center of
• 19:31
  Speaker 1: the solar system it has a positive charge, if you know,
• 19:34
  Speaker 1: if there's more electrons leaving it than protons, that.
• 19:37
  Speaker 2: Does tend to make the Sun more positive than negative.
• 19:40
  Speaker 2: There's a lot of other processes happening at the same
• 19:43
  Speaker 2: time that affect the overall charge. For example, the streams
• 19:46
  Speaker 2: of electrons end up creating a positive charge at the
• 19:50
  Speaker 2: core of the solar system, but that in turn makes
• 19:53
  Speaker 2: an electric field that tends to accelerate positive charges away
• 19:57
  Speaker 2: from the Sun, which ends up helping to balance that out.
• 20:00
  Speaker 2: So you see how electromagnetic effects tend to neutralize themselves.
• 20:04
  Speaker 2: The key takeaway is not that the Sun is throwing
• 20:07
  Speaker 2: out electrons which are hitting the Moon, but just more generally,
• 20:10
  Speaker 2: that the Sun fills the solar system with charged particles
• 20:13
  Speaker 2: which are then around to interact with the Moon. So
• 20:17
  Speaker 2: that's a whole other topic we can dig into, like
• 20:19
  Speaker 2: what is the electrical charge of the Sun. Turns out
• 20:22
  Speaker 2: to be much more complicated even than the electrical charge
• 20:24
  Speaker 2: of the moon.
• 20:25
  Speaker 1: Hmmm. But I guess it does have a positive charge
• 20:29
  Speaker 1: because you know, the Sun is so sunny all the time.
• 20:33
  Speaker 2: I've never seen the Sun be negative. That's true.
• 20:36
  Speaker 1: There you go, all right. So then the idea is
• 20:38
  Speaker 1: that the Sun is positive and negative charges in the
• 20:41
  Speaker 1: solar wind, but more electrons make it out to where
• 20:44
  Speaker 1: we are, and so are basically weed the Earth and
• 20:48
  Speaker 1: the Moon are getting showered by more electrons than protons.
• 20:51
  Speaker 3: Mm hmm.
• 20:52
  Speaker 2: But this turns out to be a dominant effect only
• 20:54
  Speaker 2: on the back side of the Moon. The backside of
• 20:58
  Speaker 2: the Moon, you have this like sheath of plasma, these
• 21:00
  Speaker 2: protons and these electrons that have come along from the
• 21:03
  Speaker 2: solar wind and they're hanging out there and more the
• 21:05
  Speaker 2: electrons end up on the Moon than the protons. So
• 21:08
  Speaker 2: the backside of the Moon is negative. But there's a
• 21:11
  Speaker 2: very different process that dominates on the other side of
• 21:14
  Speaker 2: the Moon, on the sun facing side of the moon.
• 21:16
  Speaker 1: Wait wait, wait, so okay, so I'm the Moon and
• 21:18
  Speaker 1: I'm facing the Sun and I'm getting showered by electrons
• 21:21
  Speaker 1: and a little bit of protons. Now what you're saying
• 21:25
  Speaker 1: that the electrons stick to my backside, why would that be?
• 21:28
  Speaker 2: The electrons will also stick to your front side. But
• 21:30
  Speaker 2: there's another process on your front side that's even more powerful.
• 21:34
  Speaker 2: That's forcing the front side to become positively charged, and
• 21:38
  Speaker 2: that's the photoelectric effect. Photons from the Sun, really high
• 21:41
  Speaker 2: energy particles hit the Moon and they eject electrons. This
• 21:45
  Speaker 2: is the same experiment that Einstein wather bo fries for
• 21:48
  Speaker 2: explaining if you shine light on a piece of metal,
• 21:51
  Speaker 2: you'll give energy to electrons and eject electrons from the metal,
• 21:55
  Speaker 2: making it overall positively charged. The same thing happens on
• 21:58
  Speaker 2: the sun facing side of the mo Moon, making that
• 22:01
  Speaker 2: side positive and the backside ends up negative.
• 22:04
  Speaker 1: Okay, So I'm the Moon and I'm getting hit by
• 22:07
  Speaker 1: sun rays. So forget the electrons for now, I'm just
• 22:09
  Speaker 1: getting hit by sunlight, which are photons. And you're saying
• 22:12
  Speaker 1: it's kicking off the electrons off of the rocks facing
• 22:15
  Speaker 1: the sun. But where are those electrons going? Are you
• 22:18
  Speaker 1: saying they're flying off into space?
• 22:20
  Speaker 2: They're flying off into space exactly. The Moon doesn't have
• 22:23
  Speaker 2: a significant atmosphere as what they call an exosphere we
• 22:26
  Speaker 2: talked about once on the podcast, so they don't like
• 22:29
  Speaker 2: run into other particles. It's basically collisionless, so they just
• 22:32
  Speaker 2: fly out into space.
• 22:33
  Speaker 1: Yeah, okay, Well what's kicking them off into space?
• 22:36
  Speaker 2: The photons, right, Photons are coming in hitting those rocks,
• 22:39
  Speaker 2: giving those electrons a boost so they have enough energy
• 22:41
  Speaker 2: to leave the rocks and also leave the Moon.
• 22:44
  Speaker 1: Okay. So you're saying, like the moon's getting a little
• 22:47
  Speaker 1: bit of a sunburn, and the sunburn basically makes the
• 22:51
  Speaker 1: surface of the Moon facing the sun positively charge. Okay,
• 22:54
  Speaker 1: so now my sun facing side is positively charge. And
• 23:00
  Speaker 1: you're saying, now I'm getting a shower of electrons from
• 23:03
  Speaker 1: the Sun.
• 23:03
  Speaker 2: That's right. At the same time, you have a shower
• 23:05
  Speaker 2: of electrons from the sun, and your backside tends to
• 23:08
  Speaker 2: attract those electrons. Those electrons end up in this plasma
• 23:12
  Speaker 2: sheath that's around you. Plasma member is just a mix
• 23:15
  Speaker 2: of protons and electrons.
• 23:16
  Speaker 1: So it would in the front facing side, which is
• 23:18
  Speaker 1: positively charged, wouldn't that attract the electrons hitting me and
• 23:22
  Speaker 1: make them stick to me more?
• 23:23
  Speaker 2: It does do that, Yeah, and that limits the overall
• 23:26
  Speaker 2: positive charge of the front side. Right. The more positively
• 23:29
  Speaker 2: charged she gets, the more it pulls electrons back out
• 23:32
  Speaker 2: of the solar wind and out of this plasma. So
• 23:34
  Speaker 2: this isn't a huge effect. It's self limiting. As we
• 23:37
  Speaker 2: talked about, electromagnetism can be neutralized, and anytime you build
• 23:41
  Speaker 2: up a big charge, it tends to limit itself. But
• 23:44
  Speaker 2: there's a constant process here. You're constant getting bombarded by
• 23:46
  Speaker 2: more and more photons where it's generating more of a
• 23:49
  Speaker 2: positive charge, so it sort of comes into balance.
• 23:52
  Speaker 1: Oh, I see, so getting electrons knocked up into space
• 23:55
  Speaker 1: by the sunlight, but I'm also getting showered by electrons
• 23:59
  Speaker 1: from the sun. But maybe those two are not the
• 24:01
  Speaker 1: same amounts, and so overall I have a little you're
• 24:05
  Speaker 1: saying overall, I'm still left with a little bit of
• 24:07
  Speaker 1: a positive charge in my sun facing side.
• 24:09
  Speaker 2: Yes, exactly, your sunburn side is positively charged.
• 24:12
  Speaker 1: Okay, so then what happens.
• 24:14
  Speaker 2: And on the backside, as we talked about, you're negatively charged. Wait,
• 24:17
  Speaker 2: why so the front side gets charged because it's being
• 24:19
  Speaker 2: hit by these photons, right, that doesn't happen on the backside.
• 24:22
  Speaker 2: The backside of the Moon is dark. Photons don't make
• 24:25
  Speaker 2: it there, right, and so there's no photons to drive
• 24:28
  Speaker 2: it positively charged. All you have are the protons and
• 24:31
  Speaker 2: the electrons floating around in this plasma. And the electrons
• 24:35
  Speaker 2: are much higher velocity and they tend to hit the
• 24:37
  Speaker 2: Moon's surface and stick more.
• 24:39
  Speaker 1: Wait, I thought that this is not facing the Sun,
• 24:43
  Speaker 1: and most of this stuff is coming from the Sun
• 24:45
  Speaker 1: to where is my backside of the moon catching all
• 24:47
  Speaker 1: this stuff?
• 24:48
  Speaker 2: There's a gravitational effect here, right, You have this like
• 24:50
  Speaker 2: solar wind that's washing over the Moon, and then some
• 24:54
  Speaker 2: of the protons and the electrons get pulled around on
• 24:56
  Speaker 2: the backside, and you have this plasma of electrons and
• 24:59
  Speaker 2: proto hanging out on the backside because of gravity. And
• 25:03
  Speaker 2: then the electrons get pulled down to the Moon more
• 25:06
  Speaker 2: than the protons because electrons are faster moving and lighter.
• 25:10
  Speaker 1: So you're saying the backside of my moon sucks electrons
• 25:14
  Speaker 1: in through gravity.
• 25:15
  Speaker 2: Yeah, And also the electrons are moving faster and they
• 25:18
  Speaker 2: end up hitting the backside of the moon.
• 25:20
  Speaker 1: M all right. So then and more electrical than positive
• 25:24
  Speaker 1: because that's just what the solar wind is made out
• 25:26
  Speaker 1: of it.
• 25:26
  Speaker 2: And because electrons are lighter, right, they are easier to
• 25:29
  Speaker 2: pull down, And so you end up with this positive
• 25:32
  Speaker 2: charge on one side and this negative charge on the
• 25:35
  Speaker 2: other side. And then there's this threshold, this terminator region
• 25:39
  Speaker 2: right at the edge of darkness and light where it's
• 25:42
  Speaker 2: totally neutral between the positive and the negative. So this
• 25:46
  Speaker 2: is like a ring of neutrality on the Moon between
• 25:49
  Speaker 2: the positive these charged sun facing side and the negatively
• 25:52
  Speaker 2: charged dark side.
• 25:53
  Speaker 1: Hmmm, that's super interesting. But I wonder, like, isn't the
• 25:57
  Speaker 1: Moon rotating with respect to the Sun, so r and
• 25:59
  Speaker 1: d these surfaces and positive negative surfaces rotating all the
• 26:04
  Speaker 1: time and changing.
• 26:05
  Speaker 2: Yes. Absolutely. As the moon rotates, a different part of
• 26:09
  Speaker 2: it comes into contact with the photons, and so a
• 26:11
  Speaker 2: different part of the moon becomes positive and negatively charged.
• 26:15
  Speaker 2: This charging and discharging times are very very quick, and
• 26:19
  Speaker 2: so like fractions of a second, so there's not like
• 26:22
  Speaker 2: a lag between the charge of the moon and which
• 26:24
  Speaker 2: part the Sun is hitting.
• 26:26
  Speaker 1: So when I look at the moon, whether it's like
• 26:28
  Speaker 1: full moon or half moon, basically when I see it,
• 26:31
  Speaker 1: I should imagine that the part that we can see,
• 26:33
  Speaker 1: the light side, is positively charged and the dark side
• 26:36
  Speaker 1: is negatively charge no matter what phase of the moon
• 26:39
  Speaker 1: it is in.
• 26:39
  Speaker 2: Exactly, if you can see half of the moon and
• 26:41
  Speaker 2: half of it is lit, then that side is positive
• 26:44
  Speaker 2: and the dark half is negative. Then as it rotates,
• 26:47
  Speaker 2: those charges change. So if you're just standing on the
• 26:50
  Speaker 2: surface of the moon, the surface you're standing on goes
• 26:52
  Speaker 2: from being positively to negatively charged from daytime to nighttime.
• 26:57
  Speaker 1: Hmmm, that sounds super interesting. See what do you want
• 27:00
  Speaker 1: experience that yourself? I mean, you talk so excitedly about it.
• 27:06
  Speaker 1: Wouldn't it be great to be there?
• 27:08
  Speaker 2: I think it's super fascinating, But I think it could
• 27:10
  Speaker 2: also be unpleasant. I mean we're talking about like up
• 27:13
  Speaker 2: to forty five hundred volts of static electricity.
• 27:16
  Speaker 1: Wait what, yeah? That much?
• 27:19
  Speaker 2: Yes, it's so powerful that it causes like dust to
• 27:22
  Speaker 2: levitate on the surface of the Moon. If your dust
• 27:26
  Speaker 2: develops a charge, it can repel the surface of the moon.
• 27:29
  Speaker 2: You have like electromagnetic levitation happening on the surface of
• 27:33
  Speaker 2: the moon.
• 27:33
  Speaker 1: That just makes it sound more exciting, Daniel, I.
• 27:37
  Speaker 2: Think it's exciting for other people to go and take
• 27:39
  Speaker 2: pictures and tell me all about it while I stay
• 27:41
  Speaker 2: in the comfort of southern California.
• 27:44
  Speaker 1: I see charge neutral on your couch.
• 27:47
  Speaker 2: The astronaut saw this. You can see dust levitating like
• 27:50
  Speaker 2: a meter off of the Moon's surface if you go
• 27:53
  Speaker 2: for a.
• 27:54
  Speaker 1: Walk, meaning that there is like if you're in the
• 27:56
  Speaker 1: light side, there's just a lot of it's just a
• 27:58
  Speaker 1: lot of electrons floating and things. Everything's negative charge, which
• 28:02
  Speaker 1: makes the dust repel the rest of the dust which
• 28:05
  Speaker 1: makes it float.
• 28:06
  Speaker 2: Yeah, it can repel the surface. So if you're standing
• 28:08
  Speaker 2: on the surface of the moon and it's daytime, so
• 28:10
  Speaker 2: you're in the lift part, the surface is positively charged.
• 28:13
  Speaker 2: So if you can have a rock be also positively charged,
• 28:16
  Speaker 2: then it will repel the surface of the moon. You
• 28:18
  Speaker 2: just got to like rub the rock and brust some
• 28:20
  Speaker 2: electrons off of it, just that hard. You can do
• 28:23
  Speaker 2: that with like a rag then it will be positive
• 28:25
  Speaker 2: and it can float. It's not something we experienced like
• 28:28
  Speaker 2: down here on Earth very often, like unless you're in
• 28:30
  Speaker 2: a magnetically levitating train.
• 28:32
  Speaker 1: M And I guess the same would happen in the
• 28:34
  Speaker 1: dark side too, right, I mean, the same effect would
• 28:36
  Speaker 1: happen in the dark side, like you might see dust floating,
• 28:39
  Speaker 1: but for the opposite reason.
• 28:40
  Speaker 2: Yeah, exactly. And so if you plan to like have
• 28:43
  Speaker 2: your house plants levitate, then you have to switch from
• 28:45
  Speaker 2: positive to negative charge as the day goes into night.
• 28:48
  Speaker 1: Mmm. Right, like a dawn and a dust things would
• 28:51
  Speaker 1: fall to the ground.
• 28:53
  Speaker 2: Sounds like a good problem for the engineers.
• 28:55
  Speaker 1: Yeah exactly, or just you know, a handy man with
• 28:58
  Speaker 1: a hammer and a nail. All right, Well, it sounds
• 29:02
  Speaker 1: like the moon has at all times a positively charged
• 29:07
  Speaker 1: side and a negatively charged side at all times. But
• 29:11
  Speaker 1: maybe the question is does it overall have a positive
• 29:14
  Speaker 1: or negative charge? So let's dig into that. But first
• 29:17
  Speaker 1: let's take another quick break. All right, we're asking charge
• 29:33
  Speaker 1: questions about the moon. Does the moon have a charge?
• 29:35
  Speaker 1: And it sort of does? I guess it depends on
• 29:38
  Speaker 1: which side of the moon you're in. If you're in
• 29:39
  Speaker 1: the light side being hit by sunlight, then things are
• 29:42
  Speaker 1: positively charged where you are, and if you're in the
• 29:45
  Speaker 1: dark side, things are negatively charged by a lot. You
• 29:47
  Speaker 1: said about forty five hundred volts.
• 29:50
  Speaker 2: It can be up to that. Yeah, that's the largest
• 29:52
  Speaker 2: that they've measured.
• 29:53
  Speaker 1: Wow, So why doesn't it just act like a giant battery?
• 29:56
  Speaker 1: And you see these you know, sparks or currents going
• 29:58
  Speaker 1: through the moon.
• 29:59
  Speaker 2: You don't get lightning storms on the moon, right, There
• 30:01
  Speaker 2: isn't like another layer there to discharge from. And I
• 30:04
  Speaker 2: think it depends also on the distance over which you
• 30:06
  Speaker 2: have this voltage, but it can potentially be dangerous for
• 30:10
  Speaker 2: stuff on the moon if you have like electrical equipment
• 30:12
  Speaker 2: up there. That's very sensitive.
• 30:13
  Speaker 1: M But I guess if the light side and the
• 30:15
  Speaker 1: darks are so differently charged, why doesn't the charge equalize,
• 30:19
  Speaker 1: Like why don't you get a whole bunch of electrons
• 30:22
  Speaker 1: from the backside rushing to the front side.
• 30:24
  Speaker 2: Some of that does happen, right, This is self limiting,
• 30:26
  Speaker 2: and so this is like the result of a balance
• 30:28
  Speaker 2: of all these processes. If you turned off the solar wind,
• 30:31
  Speaker 2: for example, then eventually the moon would just neutralize. But
• 30:34
  Speaker 2: the solar wind is constantly making this happen, and really interestingly,
• 30:37
  Speaker 2: when the solar wind is stronger, like when you have
• 30:39
  Speaker 2: solar storms, these effects grow more dramatic. Then the moon
• 30:43
  Speaker 2: is more charged, or when the moon passes through like
• 30:46
  Speaker 2: the magnetic tail of the Earth, which tends to focus
• 30:49
  Speaker 2: the solar wind, then it also gets more powerful. So
• 30:53
  Speaker 2: it sort of depends on the solar weather.
• 30:54
  Speaker 5: Mmm.
• 30:55
  Speaker 1: Interesting, Okay, so then the light side is positively charged
• 30:58
  Speaker 1: and dark side is maked charged. But does it have
• 31:01
  Speaker 1: a charge overall or does it all balance out to
• 31:04
  Speaker 1: zero for the whole mood?
• 31:05
  Speaker 2: So this is really interesting question, like philosophically, like do
• 31:07
  Speaker 2: you really mean exactly zero? Because I think that's pretty
• 31:11
  Speaker 2: unlikely for the number of protons and the number of
• 31:13
  Speaker 2: electrons to be exactly matched to each other. It's like
• 31:16
  Speaker 2: flipping a billion coins and getting fifty percent heads exactly.
• 31:20
  Speaker 2: I think it's unlikely. So I'm sure the moon has
• 31:23
  Speaker 2: some overall charge, but I bet it's very very close
• 31:26
  Speaker 2: to zero because it's mostly made of neutral stuff, and
• 31:28
  Speaker 2: then the surfaces are a little bit charged, but one's positive,
• 31:31
  Speaker 2: one's negative, So I think overall it's going to be
• 31:34
  Speaker 2: very close to zero.
• 31:35
  Speaker 1: But here, you're just speculating, or yes.
• 31:40
  Speaker 2: I'd be pretty confident that if you added up every
• 31:42
  Speaker 2: single particle on the Moon, it would not come out
• 31:45
  Speaker 2: to a perfect balance of zero.
• 31:47
  Speaker 1: Right, But I guess would it be negative or positive?
• 31:50
  Speaker 1: What do you think it would be?
• 31:51
  Speaker 2: If I had to guess, I'd probably lean negative because
• 31:53
  Speaker 2: I think the effects of the sun light probably taper
• 31:55
  Speaker 2: off more quickly near the terminator region as the sun
• 31:59
  Speaker 2: sort of gets low in the Moon's sky, So overall
• 32:02
  Speaker 2: that might be a little bit weaker than the effects
• 32:04
  Speaker 2: on the negative side. But I'm really not sure.
• 32:07
  Speaker 5: Hmm.
• 32:08
  Speaker 1: I see, like, if the sunlight effect kicking off electrons
• 32:12
  Speaker 1: off of the rocks is not as strong as like
• 32:15
  Speaker 1: the idea of being showered by a whole bunch of
• 32:17
  Speaker 1: electrons from the sun, then overall it would have a
• 32:19
  Speaker 1: negative charge. Yeah, exactly, But it's not quite clear, right, Like,
• 32:23
  Speaker 1: maybe maybe the sunlight does kick off more electrons than
• 32:26
  Speaker 1: get absorbed from the silver wind.
• 32:27
  Speaker 2: Mm, And this is not something we know the answer to.
• 32:30
  Speaker 2: There are folks who study the charge of the Moon,
• 32:33
  Speaker 2: and they make some measurements from things orbiting the Moon,
• 32:36
  Speaker 2: but mostly they have models that describe like these plasmachines
• 32:39
  Speaker 2: and on these processes we talked about the photo electric effect,
• 32:42
  Speaker 2: and they try to match them up with a few
• 32:44
  Speaker 2: measurements they make. But we don't have a whole lot
• 32:46
  Speaker 2: of measurements on the surface of the Moon, and we
• 32:49
  Speaker 2: have some measurements from Apollo astronauts. We're not sure that
• 32:52
  Speaker 2: they were always working in like typical conditions, and as
• 32:55
  Speaker 2: we know, this is like constantly changing throughout the day.
• 33:00
  Speaker 1: Throughout the seasons as well, right like as it interacts
• 33:02
  Speaker 1: with the Earth.
• 33:03
  Speaker 2: Maybe also yeah, and it's probably not a coincidence, but
• 33:06
  Speaker 2: most of the Apollo astronauts tend to visit the Moon
• 33:08
  Speaker 2: under pretty normal solar conditions, Like if there's going to
• 33:12
  Speaker 2: be a big solar storm, then you're probably not going
• 33:14
  Speaker 2: to launch your astronauts up to the Moon. And so
• 33:16
  Speaker 2: we tend to have measurements during intervals of less extreme
• 33:20
  Speaker 2: space weather.
• 33:22
  Speaker 1: But I wonder if you could measure some other charge
• 33:24
  Speaker 1: of the Moon from a distance, could you? Or you
• 33:26
  Speaker 1: mentioned earlier, some signists are trying to do that. How
• 33:29
  Speaker 1: are they doing that and what kind of effect are
• 33:31
  Speaker 1: they using to measure this?
• 33:32
  Speaker 2: What they're doing is basically measuring the particles that come
• 33:35
  Speaker 2: off of the moon. Like you have something orbiting the moon.
• 33:38
  Speaker 2: You can collect particles, you can count, like how many
• 33:40
  Speaker 2: electrons are being pushed off of the positive side, how
• 33:43
  Speaker 2: many electrons are being lost on the negative side. Basically,
• 33:46
  Speaker 2: where are the particles and where are they going? And
• 33:48
  Speaker 2: then compare that to the model you have of what's
• 33:51
  Speaker 2: going on on the surface, and try to constrain it
• 33:53
  Speaker 2: and say, by measuring this many protons per second per
• 33:56
  Speaker 2: square centimeter up here, then how many are actually being
• 34:00
  Speaker 2: attracted to the moon or being pushed off of the moon.
• 34:03
  Speaker 1: Or I guess maybe to bring it down to Earth.
• 34:05
  Speaker 1: Like if I had an apple in front of me,
• 34:06
  Speaker 1: how would I measure whether it has a positive or
• 34:09
  Speaker 1: negative charge?
• 34:09
  Speaker 2: So the overall charge you can measure quite easily from
• 34:12
  Speaker 2: a distance. Right, you just have a test particle, You
• 34:15
  Speaker 2: put an electron near it, and you see the force
• 34:16
  Speaker 2: on that electron, and that will tell you the charge
• 34:19
  Speaker 2: of the apple.
• 34:20
  Speaker 1: What do you mean you test the force of an electron.
• 34:23
  Speaker 2: So if the apple is charged, it will create an
• 34:25
  Speaker 2: electric field, and that electric field would push or pull
• 34:27
  Speaker 2: on other charged particles. So if you want to measure
• 34:30
  Speaker 2: the charge of the apple, you basically need to measure
• 34:32
  Speaker 2: the strength of the field that it creates, and you
• 34:34
  Speaker 2: can do that by putting another particle in that field.
• 34:37
  Speaker 2: So if you have an electron, for example, and you
• 34:39
  Speaker 2: drop it near some object and you watch that electron move,
• 34:43
  Speaker 2: it'll tell you what the strength of the field is
• 34:45
  Speaker 2: moving through is because you'll see it bend or accelerate
• 34:48
  Speaker 2: or whatever, and that'll tell you the charge of the
• 34:50
  Speaker 2: object that made that field.
• 34:52
  Speaker 1: Could you do that with the Moon? Also? Like could
• 34:54
  Speaker 1: we not just like drop an electron near the Moon
• 34:57
  Speaker 1: and then figure out if it's positively or negatively?
• 35:00
  Speaker 2: Yeah, it's a cool question, and you could do that
• 35:02
  Speaker 2: if like there was a total vacuum, right, But everywhere
• 35:04
  Speaker 2: around the moon is a plasma. There's lots of positive
• 35:08
  Speaker 2: negative particles, So you can't just like isolate the moon.
• 35:11
  Speaker 2: And it comes down a little bit too like definition,
• 35:13
  Speaker 2: Like what do you mean by the moon? Do you
• 35:14
  Speaker 2: mean just the rocks that are made up you mean
• 35:17
  Speaker 2: also the exosphere? Do you mean this plasma sheet that
• 35:19
  Speaker 2: surrounds it as well?
• 35:21
  Speaker 1: Yes, to all of it. I mean I mean just
• 35:25
  Speaker 1: like if you stand away from the Moon a good
• 35:27
  Speaker 1: distance away, is it is it does overall have a
• 35:29
  Speaker 1: negative or positive charge. I mean, I thought that's kind
• 35:32
  Speaker 1: of what we're asking in this episode.
• 35:33
  Speaker 2: Yeah, I don't know if anybody's actually tried to measure
• 35:36
  Speaker 2: the overall charge of the Moon in that way. I'm
• 35:39
  Speaker 2: pretty sure it's close to zero. And we've measured the
• 35:42
  Speaker 2: charges on various sides of it and these processes and
• 35:45
  Speaker 2: understood that pretty well, and that all comes together to
• 35:47
  Speaker 2: tell you the story that the Moon is very likely
• 35:50
  Speaker 2: overall zero. But I don't know about an actual direct measurement,
• 35:53
  Speaker 2: Like we're talking about here dropping electrons somewhere near the
• 35:56
  Speaker 2: Moon and seeing what happens to them.
• 35:58
  Speaker 1: It sounds like somebody needs to go there, I know.
• 36:01
  Speaker 2: All right, everybody chip in for Jorges trip to the Moon.
• 36:04
  Speaker 1: Yeah, there you go, I'll pay for the electrons, now
• 36:08
  Speaker 1: go drop them off. All right. Well, what does this
• 36:11
  Speaker 1: mean about the Moon in general in kind of how
• 36:14
  Speaker 1: things are going in our solar system?
• 36:16
  Speaker 2: Well, it makes the Moon an even less pleasant place
• 36:19
  Speaker 2: to visit, because all the dust on there is very
• 36:22
  Speaker 2: very charged up, and it makes it really a pain,
• 36:25
  Speaker 2: like the dust tends to stick to everything. All the
• 36:28
  Speaker 2: experiments they did on the Moon and all the equipment
• 36:30
  Speaker 2: they brought came back like coded with this terrible regolith dust.
• 36:34
  Speaker 2: Everything on the Moon tends to stick because it all
• 36:37
  Speaker 2: gets charged up and it's a big mess.
• 36:39
  Speaker 1: Wait, why would dust stick if it's negatively charged? Wouldn't
• 36:43
  Speaker 1: be repelled by something neutral? Or would he care about
• 36:46
  Speaker 1: something neutral like my clothes?
• 36:48
  Speaker 2: For the same reason that like a balloon will stick
• 36:50
  Speaker 2: to your hair if you rub it enough. You know,
• 36:52
  Speaker 2: you are effectively shedding charges, and so you're building up
• 36:55
  Speaker 2: an overall electromagnetic force. And so the same thing happens
• 36:59
  Speaker 2: on the Moon all the time.
• 37:01
  Speaker 1: I see. So it's not easy to get rid of
• 37:03
  Speaker 1: this dust.
• 37:04
  Speaker 2: Yeah, exactly, But there are some positive sides. The fact
• 37:08
  Speaker 2: that the moon surface can be positively or negatively charged
• 37:12
  Speaker 2: might help us develop technology to explore or live on
• 37:15
  Speaker 2: the Moon. Is a group trying to build a levitating glider.
• 37:19
  Speaker 2: They're like, Hey, if dust can float on the Moon
• 37:21
  Speaker 2: using electromagnetism, why can't we build a device that like
• 37:24
  Speaker 2: floats on the moon, basically flying cars on the Moon? Mmm?
• 37:29
  Speaker 1: Like, use the fact that the surface of the Moon
• 37:31
  Speaker 1: is very charged, you know, positively on the light side,
• 37:34
  Speaker 1: negatively on the dark side, to maybe do like a
• 37:37
  Speaker 1: mac left train.
• 37:38
  Speaker 2: Yeah, except in this case would be like electro lev
• 37:40
  Speaker 2: I suppose the idea is to use an ion engine.
• 37:44
  Speaker 2: An ion engine is where you take like a neutral atom,
• 37:47
  Speaker 2: you know, a proton and an electron, you break them down,
• 37:50
  Speaker 2: you accelerate one of them and shoot them out the
• 37:52
  Speaker 2: back of the engine. So say, for example, you shoot
• 37:55
  Speaker 2: the electrons out the back of the engine. That's like
• 37:57
  Speaker 2: you're propellant. So you have a little rocket that's shooting
• 37:59
  Speaker 2: electrons the back and it gives you a little bit
• 38:01
  Speaker 2: of thrust. That's an ion engine. Well, one consequence of
• 38:04
  Speaker 2: throwing electrons out the back of your engine is now
• 38:07
  Speaker 2: your engine becomes positively charged. So if you're trying to
• 38:10
  Speaker 2: levitate over a positively charged surface, that gives you an
• 38:12
  Speaker 2: extra little boost. So you run your little engines, but
• 38:15
  Speaker 2: they don't have to be as powerful as normal because
• 38:18
  Speaker 2: now they're getting positively charged, so they're getting repelled by
• 38:21
  Speaker 2: the surface. So if you're going to build a little
• 38:23
  Speaker 2: glider to explore the Moon, you can take advantage of
• 38:25
  Speaker 2: this effect.
• 38:26
  Speaker 1: I see, figure out how to get rid of all
• 38:29
  Speaker 1: your electrons so that your car is positively charged, which
• 38:35
  Speaker 1: would make it float a little bit above the positively
• 38:38
  Speaker 1: charged moon.
• 38:39
  Speaker 2: Floor exactly, But then you're like Cinderella and you have
• 38:41
  Speaker 2: to watch out for the sunset because then your car
• 38:43
  Speaker 2: is going to slam into the surface.
• 38:45
  Speaker 1: When you get to the dark side, then the whole
• 38:47
  Speaker 1: surrounding floor turns negative exactly.
• 38:51
  Speaker 2: But then you just got to flip your ion engines
• 38:53
  Speaker 2: the other way and shoot the protons out of it
• 38:55
  Speaker 2: instead of the electrons, so it can work on either side.
• 38:58
  Speaker 1: But would that be enough gosh, I know the gravity
• 39:02
  Speaker 1: is lower on the Moon, but would it be enough
• 39:04
  Speaker 1: to actually make something flow?
• 39:06
  Speaker 2: Potentially? They're working on the technology and they've tested one
• 39:09
  Speaker 2: on Earth where they have like a one kilogram object
• 39:12
  Speaker 2: who was able to levitate a centimeter above the surface,
• 39:15
  Speaker 2: and they speculate that on future missions to very low
• 39:19
  Speaker 2: mass moons, very small moons, you might want a flyer
• 39:22
  Speaker 2: instead of a rover because rovers get stuck on surface effects,
• 39:26
  Speaker 2: and helicopters can be pretty tricky if there isn't enough atmosphere.
• 39:29
  Speaker 2: So they're thinking about developing these electrically levitating gliders for
• 39:33
  Speaker 2: exploring future small moons. We might want to figure out
• 39:37
  Speaker 2: if there's like alien life on or just figure out
• 39:39
  Speaker 2: what's on them.
• 39:40
  Speaker 1: I see, just to get around, because I guess wheels
• 39:42
  Speaker 1: can only get you so far.
• 39:44
  Speaker 2: Yeah, exactly. The glider doesn't get stuck in a crevass,
• 39:47
  Speaker 2: then it's easier to get over hills. You know. We
• 39:49
  Speaker 2: have these cool helicopter on Mars now and they're developing
• 39:51
  Speaker 2: one to fly on some of the moons of Jupiter.
• 39:54
  Speaker 2: But those are really good in higher atmosphere environments, and
• 39:57
  Speaker 2: this would work in a very low atmosphere environment moon.
• 40:00
  Speaker 1: All right, Well, it sounds like the answer to our
• 40:02
  Speaker 1: question today what's the electrical charge of the moon, is
• 40:05
  Speaker 1: that it depends on what side of the Moon you're in.
• 40:07
  Speaker 1: If you're in the light side, the charge is positive.
• 40:10
  Speaker 1: You're in dark side, it's negative. If you're in the
• 40:12
  Speaker 1: dusks or twilight zone, then things are neutral. But overall
• 40:17
  Speaker 1: it sounds like it's still kind of a mystery what
• 40:19
  Speaker 1: the charge of the whole moon is.
• 40:21
  Speaker 2: We think it's probably pretty close to zero, but we
• 40:24
  Speaker 2: don't have direct measurement using jorgees.
• 40:27
  Speaker 1: Electron right, right, and by we Daniel means Daniel.
• 40:30
  Speaker 2: That's right. I've not yet sent jorget to measure the
• 40:32
  Speaker 2: charge of the moon, so I don't have that data.
• 40:34
  Speaker 2: Nobody knows the exact charge of the.
• 40:37
  Speaker 1: Moon right now, all right, but I think it's another
• 40:40
  Speaker 1: interesting example of how complex things can get in the universe.
• 40:43
  Speaker 1: You know, you might think that something like the Doing
• 40:46
  Speaker 1: is just floating out there in space and it's made
• 40:48
  Speaker 1: out of neutral rocks, and so it must have a
• 40:49
  Speaker 1: neutral charge. But you know, there's so much going on
• 40:51
  Speaker 1: in the Solar system with the solar wind and gravity
• 40:54
  Speaker 1: and light and the photo electric effect, that things can
• 40:57
  Speaker 1: I get complicated and a little bit charged up.
• 40:59
  Speaker 2: Yeah, there's a lot more going on than just gravity
• 41:01
  Speaker 2: that shapes our solar system and our galaxy. These winds
• 41:05
  Speaker 2: affect our solar system, but there are also galactic winds
• 41:08
  Speaker 2: radiation from the center of the galaxy that shape the
• 41:12
  Speaker 2: structure of the galaxy and the star formation. So electromagnetism
• 41:16
  Speaker 2: still has things to say about the structure of the universe.
• 41:18
  Speaker 1: All right, Well, we hope you enjoyed that. Thanks for
• 41:21
  Speaker 1: joining us. See you next time.
• 41:27
  Speaker 2: For more science and curiosity. Come find us on social
• 41:30
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• 41:34
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• 41:37
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• 41:40
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