Latest / Daniel and Kelly’s Extraordinary Universe / Listener Questions 55: Time and waves!

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Listener Questions 55: Time and waves! · Daniel and Kelly’s Extraordinary Universe

• 0:08
  Speaker 1: Hey, Daniel, do you think going to space will make
• 0:09
  Speaker 1: you older or younger?
• 0:12
  Speaker 2: I think it's going to be a rough trip, so
• 0:14
  Speaker 2: you'll probably come back feeling pretty worn down and older.
• 0:16
  Speaker 1: Yeah, but it's probably pretty exhilerating. So when don't you
• 0:19
  Speaker 1: come back younger in spirit?
• 0:23
  Speaker 2: I mean you might feel wiser, which is just going
• 0:25
  Speaker 2: to make you feel older.
• 0:26
  Speaker 1: Wiser is good. But what does physics say? What does
• 0:29
  Speaker 1: relativity say? If you go to space, are you going
• 0:31
  Speaker 1: to get older or younger?
• 0:33
  Speaker 2: Physics says you're going to be a tiny bit younger,
• 0:35
  Speaker 2: probably not enough to compensate for the decades of wear
• 0:38
  Speaker 2: and tear.
• 0:38
  Speaker 1: But you're in space and you're floating. What wears you
• 0:41
  Speaker 1: down the danger of dying at any moment. Perhaps that's
• 0:46
  Speaker 1: the same here on Earth.
• 0:48
  Speaker 2: The lack of gravity, the intense radiation, and yes, the
• 0:51
  Speaker 2: danger of dying, which is much higher up in space.
• 0:55
  Speaker 1: But if you can gain a second, I mean, isn't
• 0:58
  Speaker 1: time priceless? It's all we have.
• 1:00
  Speaker 2: You gain one second and you lose ten years.
• 1:02
  Speaker 1: But what of you? Hi? I'm Jorge, I'm a cartoonist
• 1:19
  Speaker 1: and the author of Oliver's Great Big Universe.
• 1:21
  Speaker 2: Hi, I'm Daniel I'm a particle physicist and a professor
• 1:24
  Speaker 2: at UC Irvine, and I'm gonna enjoy every second of
• 1:27
  Speaker 2: life here on Earth.
• 1:28
  Speaker 1: Yeah, presumably hopefully even these seconds where we are recording
• 1:32
  Speaker 1: this podcast.
• 1:33
  Speaker 2: Oh these are some of my favorite seconds. Absolutely.
• 1:35
  Speaker 1: Would you rather be like floating off an island in
• 1:38
  Speaker 1: the Pacific drinking some drinks? I mean, this is really cool,
• 1:43
  Speaker 1: But how does that compare sitting on a private island.
• 1:47
  Speaker 2: That would be so selfish, you know, just thinking about
• 1:49
  Speaker 2: my needs. We're here to talk about physics with everybody
• 1:51
  Speaker 2: and help everybody understand the universe better. That's so much
• 1:55
  Speaker 2: more valuable.
• 1:56
  Speaker 1: Well, actually, I am sitting in a pool in my
• 1:59
  Speaker 1: private island right now recording this, So I think I
• 2:02
  Speaker 1: think that means I win, is.
• 2:03
  Speaker 2: Your garage a private island or is it just like
• 2:05
  Speaker 2: a mental island.
• 2:06
  Speaker 1: I'm not a I am floating around somehow.
• 2:14
  Speaker 2: You're floating in cyberspace.
• 2:16
  Speaker 1: But anyways, welcome to our podcast, Daniel and Jorge Explain
• 2:18
  Speaker 1: the Universe, a production of iHeartRadio.
• 2:21
  Speaker 2: In which we float your brain through an ocean of
• 2:23
  Speaker 2: crazy physics ideas. We try to take you through the
• 2:26
  Speaker 2: private island of understanding, hoping to marinate your brain in
• 2:30
  Speaker 2: these ideas and percolate some of them down into your consciousness.
• 2:34
  Speaker 2: We think that the deepest questions in the universe, how
• 2:37
  Speaker 2: it started, how big is it, how it all works,
• 2:40
  Speaker 2: are things that can be understood and deserved to be understood,
• 2:43
  Speaker 2: or at the very least, we can explain to you
• 2:45
  Speaker 2: what we do and do not yet understand.
• 2:47
  Speaker 1: That's right, because it is an amazing universe, and we
• 2:49
  Speaker 1: like to take your sense of wonder on a vacation
• 2:52
  Speaker 1: siteeing through the universe and the cosmos, looking at things
• 2:55
  Speaker 1: that are already understood by humankind and things that are
• 2:58
  Speaker 1: still a huge.
• 3:00
  Speaker 2: Because science is a never ending list of questions, We're
• 3:03
  Speaker 2: always going to be curious about the way the world
• 3:05
  Speaker 2: works and why it is the way that it is.
• 3:08
  Speaker 2: And it's those questions that power science. Questions asked by
• 3:11
  Speaker 2: people working in the very forefront of human knowledge, and
• 3:14
  Speaker 2: questions asked by everybody looking up at the night sky
• 3:17
  Speaker 2: or looking down between their toes wanting to understand how
• 3:20
  Speaker 2: everything works.
• 3:21
  Speaker 1: Don't you ever want to take a vacation, Daniel from
• 3:23
  Speaker 1: asking questions? Well, I guess this podcast is sort of
• 3:26
  Speaker 1: your vacation, because you're answering questions.
• 3:29
  Speaker 2: Vacations are just more questions. Where should we go, how
• 3:31
  Speaker 2: should we organize it, how should we get there? What
• 3:34
  Speaker 2: should we eat tonight? There's no end of questions.
• 3:37
  Speaker 1: What should we not do? That's my favorite question on
• 3:40
  Speaker 1: a vacation. But yeah, the universe is full of questions.
• 3:43
  Speaker 1: Things we can ask about it, things we can wonder
• 3:45
  Speaker 1: about it, things we can try to find the answers to,
• 3:47
  Speaker 1: and sometimes on the podcast we like to answer these questions.
• 3:50
  Speaker 2: If you have questions about the nature of the universe,
• 3:52
  Speaker 2: how things work, or if ideas aren't just not clicking
• 3:55
  Speaker 2: in your mind right to us, we would love to
• 3:58
  Speaker 2: help you understand it. Answer all of our emails to
• 4:01
  Speaker 2: questions at Danielandjorge dot com. And sometimes I get a question,
• 4:05
  Speaker 2: I think, ooh, I bet other people want to hear
• 4:08
  Speaker 2: the answer to this, or I want to hear what
• 4:10
  Speaker 2: Jorge has to think or joke about this topic. So
• 4:13
  Speaker 2: then we answer them here on the podcast, so do.
• 4:15
  Speaker 1: They on the program we'll be tackling listener questions number
• 4:23
  Speaker 1: fifty five. Fifty five doesn't seem like a very big number,
• 4:26
  Speaker 1: but we are pretty deep into our production run.
• 4:31
  Speaker 2: Fifty five is a pretty big number. There are lots
• 4:34
  Speaker 2: of podcasts out there that don't even have fifty five episodes.
• 4:37
  Speaker 1: Fifty five seventy five.
• 4:40
  Speaker 2: Time to take a vacation.
• 4:43
  Speaker 1: But yeah, we'd like to ask our listener questions, and
• 4:45
  Speaker 1: so we have three great questions here about space travel,
• 4:48
  Speaker 1: but the nature of light, and about quasi particles, not
• 4:53
  Speaker 1: queasy particles, those are particularly uneasy.
• 5:00
  Speaker 2: We will not be talking about Burbon's today.
• 5:02
  Speaker 1: Yeah, or bar Fonds. But yeah, we have three awesome questions,
• 5:07
  Speaker 1: and so let's dive into our first one. This one
• 5:09
  Speaker 1: comes from Dan.
• 5:10
  Speaker 3: I'm Dan, and I have a question about space travel
• 5:13
  Speaker 3: and time. If we're able to send a spaceship to
• 5:16
  Speaker 3: Mars and back, wouldn't the astronauts be a different age
• 5:18
  Speaker 3: than the rest of us when they returned, And would
• 5:21
  Speaker 3: the difference be caused by how fast they traveled or
• 5:24
  Speaker 3: how long they were gone?
• 5:26
  Speaker 1: Interesting question from Dan. I guess the main thing is
• 5:29
  Speaker 1: is that a lot of people maybe associate space travel
• 5:32
  Speaker 1: with differences in time, like the famous twin Paradix.
• 5:36
  Speaker 2: Yeah, it sounds like Dan is planning a vacation in
• 5:38
  Speaker 2: Mars and he's wondering how many shirts he's got a pack,
• 5:41
  Speaker 2: how long will that trip be for him?
• 5:44
  Speaker 1: Yeah, I guess if he's not aging, he won't need
• 5:46
  Speaker 1: as many shirts, or he doesn't need to go to
• 5:49
  Speaker 1: that rejuvenating spot on Mars.
• 5:51
  Speaker 2: Or maybe he's wondering about renting his place out while
• 5:53
  Speaker 2: he's gone. If he's gone for one year, does he
• 5:56
  Speaker 2: need to AIRBNBA for two years? Or how does that
• 5:58
  Speaker 2: all work?
• 5:59
  Speaker 1: It's confusing here on Earth if you're changing time zones.
• 6:01
  Speaker 2: That's right, exactly. But then it is right to worry
• 6:05
  Speaker 2: about this because clocks do run differently out in space
• 6:08
  Speaker 2: and on space travel, but for two reasons, both of
• 6:11
  Speaker 2: which will affect the answer.
• 6:13
  Speaker 1: Interesting. There are multiple factors here that the universe throws
• 6:16
  Speaker 1: at you.
• 6:17
  Speaker 2: Yeah, there's two different ways that time can flow differently.
• 6:21
  Speaker 2: One is based on relative velocity moving clocks run slow,
• 6:25
  Speaker 2: and the other is an absolute one. It's just based
• 6:27
  Speaker 2: on space curvature. When space is bent, time is also bent,
• 6:32
  Speaker 2: so clocks tend to run more slowly when space is
• 6:36
  Speaker 2: more curved. These are two separate effects with different causes
• 6:40
  Speaker 2: and importantly different behaviors, but both of them will cause
• 6:43
  Speaker 2: clocks to run more slowly.
• 6:44
  Speaker 1: I meaning that time depends not just on how fast
• 6:46
  Speaker 1: you're moving, which is maybe the one people are more
• 6:48
  Speaker 1: familiar with, but also just how close you are to
• 6:51
  Speaker 1: heavy things, things that bend space and time, including.
• 6:54
  Speaker 2: The Earth, including the Earth, and including the Sun. This
• 6:58
  Speaker 2: is why, for example, if somebody is you're a black hole,
• 7:01
  Speaker 2: distant observers will see their time running super duper slowly,
• 7:04
  Speaker 2: not because they're moving at some high speed, but just
• 7:07
  Speaker 2: because they are in place of high curvature. They are
• 7:10
  Speaker 2: near a big, massive object, and time will run more slowly.
• 7:14
  Speaker 2: That's called gravitational time dilation. So there's velocity based time
• 7:18
  Speaker 2: dilation and gravitational time dilation.
• 7:22
  Speaker 1: Well, so then when you're leaving Earth, you're basically experiencing
• 7:26
  Speaker 1: both at different degrees and at different times, right, because
• 7:29
  Speaker 1: you're leaving the Earth, which is has a gravitational field,
• 7:32
  Speaker 1: but you're also going potentially really fast out there in space.
• 7:35
  Speaker 2: Yeah, exactly, And so it depends a little bit on
• 7:38
  Speaker 2: the details, but we can do some approximate calculations to
• 7:41
  Speaker 2: give Dan a rough answer.
• 7:42
  Speaker 1: All right, well, let's start with I guess the first
• 7:44
  Speaker 1: factor velocity. How fast do you think Dan is going
• 7:47
  Speaker 1: to Mars?
• 7:49
  Speaker 2: This is a good question. It depends a lot on
• 7:51
  Speaker 2: what you assume, but I thought, let's crank it to
• 7:54
  Speaker 2: the extreme. Let's think about like the fastest possible trip
• 7:57
  Speaker 2: you could make to Mars to have the most dramatic
• 8:00
  Speaker 2: impact on time.
• 8:01
  Speaker 1: You mean, like to calculate the speed, We're just going
• 8:02
  Speaker 1: to draw a straight line from here to Mars.
• 8:04
  Speaker 2: Yeah, and we're also going to assume that we have
• 8:06
  Speaker 2: super heavy duty engines and excellent power, because you could
• 8:09
  Speaker 2: get to Mars really slowly, Like you could go to
• 8:11
  Speaker 2: Mars at like walking speed, it would take you a
• 8:13
  Speaker 2: zillion years and you'd have no time dilation effects. Or
• 8:17
  Speaker 2: you could get to Mars super duper fast if you
• 8:19
  Speaker 2: have really powerful engines that push you up above a
• 8:22
  Speaker 2: tiny fraction of the speed of light, then you'd have
• 8:24
  Speaker 2: more time dilation effects. So the time dilation effects depend
• 8:27
  Speaker 2: on your top speed in the journey, which depends a
• 8:30
  Speaker 2: little bit on the technology you have to get to
• 8:32
  Speaker 2: that top speed.
• 8:34
  Speaker 1: But in reality, I guess when we send things to Mars,
• 8:36
  Speaker 1: they usually take this roundabout way, right, Like you try
• 8:38
  Speaker 1: to use orbital dynamics and you try to use maybe
• 8:41
  Speaker 1: the gravity of other planets to assist you and push
• 8:43
  Speaker 1: you along, and so it takes a while but even
• 8:45
  Speaker 1: though you're going pretty fast, Yeah, it.
• 8:47
  Speaker 2: Takes a while. It can take like six months to
• 8:49
  Speaker 2: get to Mars. And you are going pretty fast relative
• 8:52
  Speaker 2: to like the speed of a Lamborghini on Earth, but
• 8:55
  Speaker 2: you're not going very fast relative to the speed of light.
• 8:58
  Speaker 2: And that's the issue. And the speed of light is easy,
• 9:00
  Speaker 2: super duper fast, and to see real time dilation effects,
• 9:03
  Speaker 2: you got to get somewhere near the speed of light,
• 9:05
  Speaker 2: and that's pretty challenging. So I thought, how fast can
• 9:07
  Speaker 2: we get to Mars to maximize this effect?
• 9:10
  Speaker 1: I see you thought that it was not an interesting answer,
• 9:12
  Speaker 1: So let's crank it up.
• 9:13
  Speaker 2: Yeah, let's crak it up.
• 9:14
  Speaker 1: Crack it up and make it more fun.
• 9:16
  Speaker 2: Yeah, let's assume Elon Musk or somebody else develops like
• 9:19
  Speaker 2: a really powerful engine, one that uses like antimatter fuel,
• 9:24
  Speaker 2: that uses like antiprotons or anti electrons that totally annihilate
• 9:28
  Speaker 2: perfectly efficiently into energy and can pour that directly into
• 9:32
  Speaker 2: the acceleration of your spacecraft.
• 9:35
  Speaker 1: It doesn't have to be an antimatter engine. It just
• 9:36
  Speaker 1: has to be a powerful engine, right.
• 9:38
  Speaker 2: Just has to be a powerful engine. But you want
• 9:40
  Speaker 2: an efficient fuel source so that you minimize the amount
• 9:43
  Speaker 2: of fuel you have to bring along, so the fuel
• 9:45
  Speaker 2: is mostly pushing the spaceship and not the other fuel.
• 9:48
  Speaker 1: I feel like you're worrying about a real life consequences
• 9:50
  Speaker 1: in an imaginary scenario. Like I guess maybe you calculated
• 9:55
  Speaker 1: to the distance to Mars.
• 9:57
  Speaker 2: What's that distance at the closest approach the Earth to
• 9:59
  Speaker 2: Mars distance is about half of the Earth the Sun distance,
• 10:03
  Speaker 2: So it's like forty five million miles.
• 10:06
  Speaker 1: So we have a distance, and so how did you
• 10:08
  Speaker 1: calculate how fast we need to go to get there
• 10:11
  Speaker 1: in a reasonable scenario.
• 10:13
  Speaker 2: Well, I imagine that we could build an engine out
• 10:15
  Speaker 2: of anti matter, And I thought, what are the practical
• 10:17
  Speaker 2: limitations for launching that kind of ship? But how much
• 10:19
  Speaker 2: engine power could it produce? And you know, if you
• 10:22
  Speaker 2: spent like a few years generating antimatter, you'd have enough
• 10:26
  Speaker 2: engine power at launch that's like more than a thousand
• 10:30
  Speaker 2: times the electrical power output of the United States, which
• 10:33
  Speaker 2: would require like five tons or so of antimatter, which
• 10:37
  Speaker 2: is totally unrealistic. But if you did that, then you
• 10:41
  Speaker 2: would be able to get to Mars in just a
• 10:42
  Speaker 2: couple of days. Like that kind of super powerful engine
• 10:46
  Speaker 2: would get you up to like a third of one
• 10:48
  Speaker 2: percent of the speed of light for a pretty zippy
• 10:50
  Speaker 2: trip to Mars.
• 10:51
  Speaker 1: Would that run into like acceleration limits, Like our bodies
• 10:54
  Speaker 1: can only tolerate so many g's.
• 10:56
  Speaker 2: That's right, humans can only tolerate like eight to ten
• 10:59
  Speaker 2: g and even that's pretty extreme. So I was assuming
• 11:03
  Speaker 2: we have like super robust astronauts that can tolerate about
• 11:05
  Speaker 2: eight to ten gs.
• 11:06
  Speaker 1: Okay, so then you calculated the trip for Dan and
• 11:09
  Speaker 1: you get up to about point to eight c's.
• 11:13
  Speaker 2: Yeah exactly. Then that's at the halfway point because you've
• 11:16
  Speaker 2: got to speed up and then you're going to turn
• 11:17
  Speaker 2: around and slow down so that when you get to
• 11:19
  Speaker 2: Mars you're not just zipping by it at half a
• 11:22
  Speaker 2: percent of the speed of light, because that's kind of
• 11:24
  Speaker 2: beside the point. So this top speed is at the
• 11:27
  Speaker 2: halfway point.
• 11:28
  Speaker 1: Now, this is a very small percentage of the speed
• 11:30
  Speaker 1: of light, less than a third of a percent. So
• 11:32
  Speaker 1: I'm guessing maybe time didn't move that much slower for
• 11:36
  Speaker 1: Dan because of the speed.
• 11:37
  Speaker 2: Yeah exactly. And relativity is very nonlinear, so if you're
• 11:41
  Speaker 2: still at very low velocities, there's basically no effect. The
• 11:44
  Speaker 2: effect gets stronger as you get closer to the speed
• 11:46
  Speaker 2: of light. As you get very close to the speed
• 11:48
  Speaker 2: of light, it gets much more dramatic. So when you're
• 11:51
  Speaker 2: going at this pretty respectable speed compared to Lamborghinians on Earth,
• 11:54
  Speaker 2: but still very very slow compared to photons.
• 11:57
  Speaker 1: How fast are we going relative to a Lamborghini.
• 12:00
  Speaker 2: Yeah, so that's about eight hundred and forty thousand meters
• 12:04
  Speaker 2: per second, which is something like one point eight million
• 12:09
  Speaker 2: miles per hour, so a lot faster than a Lamborghini.
• 12:12
  Speaker 1: Yeah, by a large amount. But even though you're going
• 12:15
  Speaker 1: over a million miles per hour, the time dilation is
• 12:18
  Speaker 1: not dead much.
• 12:19
  Speaker 2: The time dollation factor is one point zero zero zero
• 12:24
  Speaker 2: zero zero four, meaning like every million seconds somebody traveling
• 12:29
  Speaker 2: at that speed experiences four seconds fewer at the peak speed.
• 12:33
  Speaker 2: At the peak speed.
• 12:34
  Speaker 1: Yeah, but Dan is not going at the peak speed
• 12:36
  Speaker 1: the whole time. So like if he goes around back,
• 12:38
  Speaker 1: how much time is a younger relative to his twin
• 12:41
  Speaker 1: who was born at the same time here on Earth
• 12:43
  Speaker 1: and that didn't go.
• 12:43
  Speaker 2: If he goes there in forty eight hours and back
• 12:45
  Speaker 2: in forty eight hours, that's like roughly one hundred hours,
• 12:48
  Speaker 2: which is not even a million seconds, so the difference
• 12:51
  Speaker 2: is going to be less than a second overall.
• 12:53
  Speaker 1: But he's also had to accelerate up to the speed
• 12:56
  Speaker 1: and accelerate down to zero, so it's probably even less
• 12:59
  Speaker 1: than that, maybe maybe like a tenth of that.
• 13:01
  Speaker 2: Yeah, it's going to be less than a second for sure.
• 13:03
  Speaker 1: So Dan's gonna go to Mars come back. He's going
• 13:06
  Speaker 1: to be at eight to ten g's the whole time,
• 13:10
  Speaker 1: and he'll only be younger by about less than a second.
• 13:13
  Speaker 2: Yeah, less than a second, exactly. That's only considering the
• 13:16
  Speaker 2: velocity effects.
• 13:17
  Speaker 1: Right right, like starting from orbit or something.
• 13:19
  Speaker 2: Mm hmm, exactly, that's not considering the gravitational time dilation.
• 13:24
  Speaker 1: All right, Well let's get into that. What are the
• 13:25
  Speaker 1: gravitational effects of a time due to gravity?
• 13:29
  Speaker 2: So there's two effects here to think about. One is
• 13:31
  Speaker 2: that you're leaving Earth's gravity and time passes more slowly
• 13:35
  Speaker 2: when you're close to earth gravity. We know this because
• 13:38
  Speaker 2: like satellites in orbit that keep our GPS systems in sync,
• 13:42
  Speaker 2: their clocks run faster than clocks on Earth. This is
• 13:45
  Speaker 2: something we've measured, so we know this very very well.
• 13:47
  Speaker 1: They've measured this in with mountains too, right, like you
• 13:50
  Speaker 1: can tell the difference between someone at the bottom of
• 13:52
  Speaker 1: a mountain and a clock running at the top of
• 13:54
  Speaker 1: the mountain.
• 13:54
  Speaker 2: Yeah, exactly. They have atomic clocks that are like two
• 13:56
  Speaker 2: meters apart in altitude, and they can tell the difference
• 13:59
  Speaker 2: in how they run. It's very very precise. It's super awesome.
• 14:02
  Speaker 1: Yeah, which means like your feet are moving through time
• 14:04
  Speaker 1: slower than your head if you're standing up.
• 14:07
  Speaker 2: Yes, but the size of this effect is tiny. Like
• 14:11
  Speaker 2: time passes on Earth more slowly than out in deep
• 14:13
  Speaker 2: space by like point seven parts per billion. That means
• 14:18
  Speaker 2: in a billion seconds, time on Earth will have ticked
• 14:20
  Speaker 2: by point seven seconds more slowly.
• 14:23
  Speaker 1: So if Dan just went up to orbit Earth's orbit,
• 14:26
  Speaker 1: we would be a little bit younger, but not by much,
• 14:28
  Speaker 1: Like I have a part per billion.
• 14:30
  Speaker 2: Yeah exactly. A billion seconds is like thirty two years,
• 14:34
  Speaker 2: So if you've been thirty two years, like in deep
• 14:36
  Speaker 2: deep orbit, then your clock will have run faster by
• 14:38
  Speaker 2: one second.
• 14:39
  Speaker 1: So it's a very negligible effect.
• 14:41
  Speaker 2: It's not I don't know if it's negligible, and you
• 14:43
  Speaker 2: can measure it with very precise devices, but it's real.
• 14:46
  Speaker 2: And the interesting thing is that Mars has lower gravity
• 14:49
  Speaker 2: than Earth. Right, it's a smaller planet, so on the
• 14:51
  Speaker 2: surface the gravity is not as intense, and so this
• 14:55
  Speaker 2: same effect on Earth that's like point seven parts per
• 14:58
  Speaker 2: billion is only point one four parts per billion on Mars.
• 15:02
  Speaker 2: So if you go to Mars and spend a lot
• 15:04
  Speaker 2: of time there, your clock will run faster than clocks
• 15:08
  Speaker 2: on Earth because you're not as deep in a gravity.
• 15:10
  Speaker 1: Well, well you're aging faster in Mars.
• 15:13
  Speaker 2: You're aging faster on Mars exactly. But that's actually not
• 15:16
  Speaker 2: even the biggest gravitational effect. Mars is further away from
• 15:20
  Speaker 2: the Sun, so the Sun's gravity is weaker at Mars
• 15:23
  Speaker 2: than it is on Earth. This is actually a bigger
• 15:26
  Speaker 2: effect than the difference between Earth and Mars. Sun's gravity
• 15:30
  Speaker 2: causes a seven parts per billion effect on Mars and
• 15:33
  Speaker 2: a ten parts per billion effect on.
• 15:35
  Speaker 1: Earth, meaning from the suns to gravity, you're aging faster
• 15:39
  Speaker 1: in Mars.
• 15:39
  Speaker 2: Also, yeah, that's right, you're aging faster on Mars because
• 15:42
  Speaker 2: its gravity is weaker and because you're further from the
• 15:45
  Speaker 2: Sun's gravity. Overall, this effect is like six parts per
• 15:48
  Speaker 2: billion on Mars.
• 15:50
  Speaker 1: Okay, so then what's the grand total for that? It
• 15:53
  Speaker 1: seems like he's gonna gain a little bit of time
• 15:56
  Speaker 1: due to velocity going to Mars and back, but he's
• 15:58
  Speaker 1: gonna lose a little bit of time by being further
• 16:01
  Speaker 1: away from the Sun and by being around a planet
• 16:04
  Speaker 1: that's smaller. What's the grand total.
• 16:05
  Speaker 2: Well, it depends on how much time he spends there. Right,
• 16:08
  Speaker 2: If he just goes there and back, there's basically no
• 16:10
  Speaker 2: effect from gravitational curvature. But if he goes there and
• 16:13
  Speaker 2: lives there for like a thousand years, then he's going
• 16:16
  Speaker 2: to accumulate some effect from the curvature. So it depends
• 16:19
  Speaker 2: on how much time he spends there.
• 16:20
  Speaker 1: On Mars, depends on how long he books that Airbnb exactly.
• 16:24
  Speaker 2: But the overall story is that these are tiny, tiny effects.
• 16:28
  Speaker 2: You'd be a challenge to measure these things. You'd need
• 16:31
  Speaker 2: very precise devices. But in the assumption that we could
• 16:33
  Speaker 2: build crazy powerful engines that get us to Mars in
• 16:36
  Speaker 2: two days, then the time dilation effects are going to
• 16:39
  Speaker 2: be the most dramatic. But even those are parts per million.
• 16:44
  Speaker 1: Yeah, they're super tiny, but what's interesting is that they're there, right,
• 16:47
  Speaker 1: They're measurable. Like if we synchronize our clocks and you
• 16:50
  Speaker 1: went out there and came back like our clocks would
• 16:52
  Speaker 1: be off.
• 16:53
  Speaker 2: Yeah, and it really reveals that we live in an
• 16:54
  Speaker 2: unusual set of circumstances. You know, we're not living near
• 16:58
  Speaker 2: very strong gravity, not traveling at very high speeds, and
• 17:02
  Speaker 2: so our clocks are mostly just synchronized. But there are
• 17:06
  Speaker 2: places in our universe with extreme gravity where things are
• 17:09
  Speaker 2: traveling at very high speeds relative to each other, and
• 17:11
  Speaker 2: their clocks are much creasier.
• 17:13
  Speaker 1: All right, Well, I guess then the answer for Dan
• 17:15
  Speaker 1: is that he's much better off vacationing here with me,
• 17:19
  Speaker 1: my private island floating at the pool, than by going
• 17:21
  Speaker 1: to Mars. I think my mojito will probably take more
• 17:24
  Speaker 1: time off with his overall age than then going to
• 17:27
  Speaker 1: space and then with an antimatter engine.
• 17:30
  Speaker 2: Yeah, that's right, His mojito will melt one second slower
• 17:33
  Speaker 2: after a million mohidos.
• 17:35
  Speaker 1: Well, it'd be hard to drink it going at eight
• 17:38
  Speaker 1: to ten g's. So again, come join me, Dan, This
• 17:43
  Speaker 1: is much more comfortable here.
• 17:45
  Speaker 2: Dan, you just scored an invitation. Wow.
• 17:47
  Speaker 1: Yeah, of course I don't know your last name, Dan,
• 17:49
  Speaker 1: so I'm just gonna ignore all emails from Dan's I
• 17:56
  Speaker 1: don't I know which one asked the question, where's this Dan, Dan?
• 18:00
  Speaker 1: Did I just invite you to my island?
• 18:04
  Speaker 2: Yes? This is my alter ego, Dan.
• 18:07
  Speaker 1: This is your twin, the twin that I wanted to
• 18:09
  Speaker 1: go to space.
• 18:10
  Speaker 2: When I take off my glasses, I'm Dan.
• 18:13
  Speaker 1: It's the twin parad doctor. All right, Well, let's get
• 18:17
  Speaker 1: to our two other questions. We have an awesome question
• 18:19
  Speaker 1: here about the nature of light and one about quasi
• 18:23
  Speaker 1: particles and crossword puzzles. So we'll get to that clue.
• 18:27
  Speaker 1: But first, let's take a quick break. All right, we're
• 18:41
  Speaker 1: asking listener questions here today and inviting people to our
• 18:45
  Speaker 1: private island. Apparently. All right, we have a great question
• 18:48
  Speaker 1: here from John Lopez about the reality and nature of light.
• 18:53
  Speaker 2: Hi, Daniel len Jorge.
• 18:55
  Speaker 4: My question is what is the physical reality of a
• 18:57
  Speaker 4: wavelength of light? Like, what is it like to have
• 19:00
  Speaker 4: a wavelength of nanometers versus a wavelength of tens of
• 19:04
  Speaker 4: meters long?
• 19:06
  Speaker 2: On the graph?
• 19:07
  Speaker 4: I know we represent it as the pigs and valleys
• 19:10
  Speaker 4: all stretched out, but what does this mean in real life?
• 19:14
  Speaker 4: For example, in microwaves, mesh holes block microwaves because their
• 19:18
  Speaker 4: wavelength is longer than the size of the holes. The
• 19:22
  Speaker 4: visible light passes through because the wavelength is so much smaller.
• 19:26
  Speaker 4: So in reality, in wavelength must be something different than
• 19:31
  Speaker 4: stretched out pigs and valleys, because otherwise it seems like
• 19:35
  Speaker 4: both could pass through the holes.
• 19:37
  Speaker 1: Just fine, All right, great question. Basically, what exactly is light?
• 19:42
  Speaker 1: Is the question? Can you shed some light on this topic.
• 19:46
  Speaker 2: I love this question because it's clear to me that
• 19:48
  Speaker 2: John is trying to like build a mental picture in
• 19:51
  Speaker 2: his Mind's trying to think about what happens in the
• 19:53
  Speaker 2: universe and trying to describe it mentally, thinking about like
• 19:57
  Speaker 2: are the photon zigging and zagging is like really wiggling sideways?
• 20:00
  Speaker 2: What is actually going on? How to think about this stuff?
• 20:03
  Speaker 2: It's really important that you build this mental model in
• 20:06
  Speaker 2: your head. That's what physics is. So I love hearing
• 20:08
  Speaker 2: him doing physics in his mind, trying to link it
• 20:11
  Speaker 2: all together to get a coherent picture. It's perfect.
• 20:13
  Speaker 1: Yeah, I guess he's trying to get it like an
• 20:15
  Speaker 1: intuitive sense of what light is like, Like if you
• 20:17
  Speaker 1: were shrunk down to the small level of quantum level,
• 20:20
  Speaker 1: what would it be like to experience light?
• 20:22
  Speaker 2: Yeah, that's a great question, and you know, fundamentally we
• 20:24
  Speaker 2: don't know what light is. Quantum mechanical things are very
• 20:28
  Speaker 2: hard to visualize and to think about. But John's question
• 20:31
  Speaker 2: actually is more about like classical physics, like thinking about
• 20:35
  Speaker 2: light in terms of electromagnetic waves, you know, the peaks
• 20:39
  Speaker 2: and the valley and the wiggles, and why that means
• 20:41
  Speaker 2: your microwave is not frying your brain even if you
• 20:44
  Speaker 2: stick your nose against it while you're cooking your popcorn
• 20:46
  Speaker 2: that you know of, Maybe that's why my brain is fried.
• 20:51
  Speaker 2: Oh my gosh.
• 20:52
  Speaker 1: Yeah, you're too impatient from the popcorn there to go
• 20:55
  Speaker 1: to Mars, take a vacation, come back. It'll be ready
• 20:59
  Speaker 1: for you.
• 20:59
  Speaker 2: And I think is a lot to learn in terms
• 21:01
  Speaker 2: of how to think about light as wiggles in the
• 21:04
  Speaker 2: electromagnetic field, because I hear a lot of misconceptions out
• 21:07
  Speaker 2: there and actually a lot of mistakes in popular descriptions
• 21:10
  Speaker 2: of how light works. So I think we can clear
• 21:12
  Speaker 2: up a lot of those misunderstandings, even just in the
• 21:15
  Speaker 2: classical picture, ignoring quantum effects, not thinking about photons, just
• 21:19
  Speaker 2: thinking about light as an oscillation in the electromagnetic field.
• 21:22
  Speaker 1: WHOA, Okay, So this is confusing me a little bit
• 21:25
  Speaker 1: because I think maybe what I know what a lot
• 21:27
  Speaker 1: of people know is that light is both a particle
• 21:29
  Speaker 1: and a wave, right Like, that's kind of one of
• 21:32
  Speaker 1: the dualities that physics found out at some point. So
• 21:34
  Speaker 1: you're saying, let's ignore the fact that it's a particle,
• 21:36
  Speaker 1: or are we just going back in time and forgetting
• 21:39
  Speaker 1: quantum physics.
• 21:40
  Speaker 2: We're going back in time and forgetting quantum physics because
• 21:42
  Speaker 2: we don't need quantum physics to explain this effect. The
• 21:45
  Speaker 2: reason your microwave works and the reason that doesn't fry
• 21:48
  Speaker 2: your brain can be explained using purely classical physics.
• 21:51
  Speaker 1: So when you're talking about the wavelength of light as
• 21:53
  Speaker 1: a wave in classical physics, is that the same wave
• 21:56
  Speaker 1: as when you're talking about quantum physics and things having
• 22:00
  Speaker 1: a wave function for example?
• 22:01
  Speaker 2: There's an evolution there from one idea to the other idea. Absolutely,
• 22:05
  Speaker 2: But we don't need to go into quantum physics for
• 22:07
  Speaker 2: this answer. And that's all digression. And you might think,
• 22:10
  Speaker 2: hold on a second, but you know the world is quantum,
• 22:12
  Speaker 2: how can you do that? But you know, physics is
• 22:14
  Speaker 2: all about making approximations. None of our theories of the
• 22:17
  Speaker 2: universe are exact and perfect. They ignore quantum gravity, because
• 22:20
  Speaker 2: we don't understand it. But you only need to apply
• 22:22
  Speaker 2: the physics. You need to answer the question like if
• 22:25
  Speaker 2: somebody asks, is this canniball going to make it over
• 22:27
  Speaker 2: that castle wall? You don't need to do quantum calculations.
• 22:29
  Speaker 2: You just need F equals MA. So part of doing
• 22:32
  Speaker 2: physics is applying physics judiciously. And in this case we
• 22:35
  Speaker 2: can just think about like Maxwell's understanding of photons and
• 22:39
  Speaker 2: light as waves in the electromagnetic field.
• 22:41
  Speaker 1: Well, I imagine John is curious and it seems like from
• 22:44
  Speaker 1: his question he is about the nature of light. Yeah, so,
• 22:47
  Speaker 1: like is light a wave? Is light a not a wave?
• 22:50
  Speaker 1: We can think of it as not a wave or
• 22:52
  Speaker 1: as a wave or only a wave. What is the
• 22:54
  Speaker 1: classical picture of light?
• 22:55
  Speaker 2: Yeah? So the classical picture of light. Maxwell's idea from
• 22:58
  Speaker 2: like one hundred and fifty years ago before quantum mechanics
• 23:01
  Speaker 2: is that light just wiggles in the electromagnetic field, like
• 23:05
  Speaker 2: an electron has an electric field, right, and if you
• 23:07
  Speaker 2: wiggle an electron, the field wiggles with it. That's why
• 23:11
  Speaker 2: wiggling electrons in an antenna will generate waves like radio waves,
• 23:15
  Speaker 2: which are electromagnetic waves and other charge particles wiggling more
• 23:20
  Speaker 2: quickly with higher frequency will generate waves in the electromagnetic
• 23:25
  Speaker 2: field that have higher frequency. Some of those are visible
• 23:28
  Speaker 2: light or even ultraviolet light. So all kinds of light
• 23:32
  Speaker 2: and radio waves, all the electromagnetic radiation are just wiggles
• 23:36
  Speaker 2: in the electromagnetic field. That's the classical picture.
• 23:39
  Speaker 1: And the electromagnetic field in this case is not the
• 23:41
  Speaker 1: same as the electromagnetic quantum field that we've talked about before.
• 23:45
  Speaker 2: Well, you can quantize this whole theory, right, You can
• 23:47
  Speaker 2: say the electromagnetic field follows rules of quantum mechanics and
• 23:50
  Speaker 2: so only some solutions are valid and there's minimum oscillations.
• 23:55
  Speaker 2: But in classical physics, it just follows standard wave equations
• 23:58
  Speaker 2: and it's just the electromagnetic fields. It's the same field.
• 24:01
  Speaker 2: It's just like which equations are using to describe it,
• 24:04
  Speaker 2: and are those quant mechanical or not. And here we
• 24:06
  Speaker 2: don't need to get into the quant mechanics. But it
• 24:08
  Speaker 2: is important to understand what that field is. Right. Sometimes
• 24:12
  Speaker 2: we imagine a field is this like weird physical thing
• 24:14
  Speaker 2: that fills space, But really what it is is a
• 24:17
  Speaker 2: set of numbers at every point in space. Like if
• 24:20
  Speaker 2: you think about an electric field. You think, well, it's
• 24:22
  Speaker 2: strongest near the electron, it's weaker further from the electron. Right,
• 24:25
  Speaker 2: there's values to the field, and those values vary across space.
• 24:29
  Speaker 2: That's how you can have a wave propagating through it.
• 24:32
  Speaker 2: It's like stronger here and weaker there, and stronger here,
• 24:35
  Speaker 2: and those values are moving through the field.
• 24:37
  Speaker 1: Sort of, I guess, like a sound wave kind of,
• 24:39
  Speaker 1: but instead of there being like a physical air particles,
• 24:42
  Speaker 1: imagine they're just being nothing there, just mad.
• 24:45
  Speaker 2: Yeah, exactly, just numbers. Imagine those numbers then moving through space,
• 24:49
  Speaker 2: Like this location is a zero and the next location
• 24:51
  Speaker 2: is a two, and then that two is moving through space,
• 24:54
  Speaker 2: and now a different location has that too. That's like
• 24:56
  Speaker 2: a pulse moving through a field.
• 24:58
  Speaker 1: But is it too moving through space or is it
• 25:00
  Speaker 1: too somehow like exciting the number besides it making it
• 25:04
  Speaker 1: sort of like the wave in a stadium when you're
• 25:06
  Speaker 1: watching a game or something.
• 25:08
  Speaker 2: Yeah, it's more like the wave in a stadium. Right.
• 25:10
  Speaker 2: The energy is moving from one spot in space to
• 25:13
  Speaker 2: another spot in space. It's a different place in the
• 25:15
  Speaker 2: field that now has that energy.
• 25:17
  Speaker 1: Okay, so then before quantum physics, we thought all light
• 25:21
  Speaker 1: is just like the wave in a stadium. It propagates
• 25:24
  Speaker 1: that way. And I guess that makes sense for like
• 25:27
  Speaker 1: a light bulb, which is emanating light in all directions.
• 25:30
  Speaker 1: But then how do you think about it as a
• 25:32
  Speaker 1: for a laser. Is it just like one row of
• 25:34
  Speaker 1: the stadium is carrying the wave?
• 25:37
  Speaker 2: Yeah, just like one row of the stadium exactly. And
• 25:40
  Speaker 2: there's an important point here. When you're visualizing that laser beam,
• 25:43
  Speaker 2: that photon flying through space, you probably have in your
• 25:46
  Speaker 2: mind some sort of like sine wave, like it's wiggling
• 25:48
  Speaker 2: sideways as it moves through space, right, So what is
• 25:51
  Speaker 2: actually wiggling sideways there? Does the laser actually have like
• 25:54
  Speaker 2: a sideways extent? The answer is no. The light moves
• 25:57
  Speaker 2: in a straight, perfect line. Make a laser beam that
• 26:01
  Speaker 2: has like zero width and is perfectly parallel, then the
• 26:04
  Speaker 2: light moves in a narrow line. It doesn't wiggle sideways.
• 26:08
  Speaker 2: What's wiggling are the values of the field, right, Because
• 26:11
  Speaker 2: electromagnetic fields are slightly more complicated than just numbers in space.
• 26:15
  Speaker 2: There are vectors in space. So now at every point
• 26:19
  Speaker 2: in the field, you don't just have a number like
• 26:21
  Speaker 2: a two. You have a number and a direction and
• 26:24
  Speaker 2: so that's what's oscillating. As the light beam moves through space,
• 26:28
  Speaker 2: you have like an arrow a vector from that point,
• 26:31
  Speaker 2: and that vector can change directions and magnitude. So when
• 26:34
  Speaker 2: they depict the photon like wiggling sideways, it's not physically
• 26:38
  Speaker 2: moving to other points of space. It's just that the
• 26:40
  Speaker 2: arrow of the electro or magnetic field is now pointing
• 26:43
  Speaker 2: in a different direction.
• 26:44
  Speaker 1: Like its value as a direction sort of perpendicular to
• 26:47
  Speaker 1: the direction of the travel. Yeah, exactly is that direction changing?
• 26:51
  Speaker 1: Like for a regular pulse of light, That direction doesn't
• 26:54
  Speaker 1: really change, does it?
• 26:55
  Speaker 2: Absolutely? It does, And that's what the wavelength is, right.
• 26:57
  Speaker 2: The wavelength is how far the life light travels before
• 27:01
  Speaker 2: the arrow comes back to where it was before.
• 27:03
  Speaker 1: Wait, as it's going, as the pulse is going, it's
• 27:06
  Speaker 1: changing in both the value and it's rotating.
• 27:08
  Speaker 2: That's right, because it's shifting between its electrical and magnetic components.
• 27:13
  Speaker 2: At one point, it's purely electrical in one direction, and
• 27:16
  Speaker 2: then that electrical component is shrinking as the magnetic component
• 27:19
  Speaker 2: is growing in a perpendicular direction. Those two fields are
• 27:22
  Speaker 2: always perpendicular to each other. Which direction does it rotate?
• 27:25
  Speaker 2: That depends on the polarization of the light. Light can
• 27:28
  Speaker 2: be polarized in lots of different directions, so it could
• 27:30
  Speaker 2: not rotate, or it could rotate left, or it could
• 27:32
  Speaker 2: rotate right. That's a whole other issue. We talked about
• 27:35
  Speaker 2: that in another podcast, the polarization of light. But here
• 27:38
  Speaker 2: we can just imagine the simplest scenario. Imagine it's not polarized.
• 27:41
  Speaker 2: The electric field is pointing in one direction, then it
• 27:44
  Speaker 2: shrinks to zero as the magnetic field is created. Then
• 27:46
  Speaker 2: it goes negative, so it points in the opposite direction,
• 27:49
  Speaker 2: and then it comes back. The wavelength of the light
• 27:51
  Speaker 2: is how far it's traveled between those peaks of the
• 27:54
  Speaker 2: electric field.
• 27:55
  Speaker 1: All right. So then John's question was like, what does
• 27:58
  Speaker 1: it mean to have a nanometer wavelength and wavelength that's
• 28:02
  Speaker 1: maybe tens of meters long. Does that mean like the
• 28:05
  Speaker 1: wiggles are just shorter.
• 28:06
  Speaker 2: Yeah, it just means the wiggles are shorter. So if
• 28:09
  Speaker 2: you generate microwave radiation, you know, with microwave wavelength, that
• 28:13
  Speaker 2: means like the light travels a very short distance between
• 28:16
  Speaker 2: those peaks and the electric field. If it's like radio
• 28:18
  Speaker 2: waves with tens of meters of wavelength, then it means
• 28:22
  Speaker 2: that You can start off with like your electric field
• 28:24
  Speaker 2: peaking at one place, and then it's literally tens of
• 28:26
  Speaker 2: meters before it osclates down and then back so that
• 28:29
  Speaker 2: it has the electric field pointing in the same direction. Again,
• 28:32
  Speaker 2: that really is something physical.
• 28:35
  Speaker 1: But in both cases it's going at the speed of light.
• 28:37
  Speaker 1: It's going at the same speed. Is just that's right,
• 28:39
  Speaker 1: Spiraling or wiggling or changing at a different scale.
• 28:44
  Speaker 2: That's right. The frequency is different, but the overall speed
• 28:46
  Speaker 2: of the wave is the same. It's still moving at
• 28:48
  Speaker 2: the speed of light. Just how many wavelengths happen when
• 28:51
  Speaker 2: you go one hundred meters.
• 28:54
  Speaker 1: But again, I feel like this is kind of the
• 28:56
  Speaker 1: classical view. You preface this as being the classical view.
• 28:59
  Speaker 1: Is this actually what's going on? And does this actually
• 29:02
  Speaker 1: tell us what light is? Or is this just some
• 29:04
  Speaker 1: mathematics that we came up with that helps explain what's
• 29:08
  Speaker 1: going on with life?
• 29:10
  Speaker 2: You know, some mathematics that we came up with that
• 29:12
  Speaker 2: helps explain what we see, could describe all the physics.
• 29:15
  Speaker 2: You know, we don't know what's really going on at
• 29:18
  Speaker 2: any level philosophically. All of our theories are just some
• 29:21
  Speaker 2: mathematics that help us explain what's going on. We don't
• 29:24
  Speaker 2: know what's true. We think that none of our theories
• 29:26
  Speaker 2: are true.
• 29:26
  Speaker 1: Well, there's a little bit of a difference, right, Like
• 29:28
  Speaker 1: for example, like if you're dealing with waves in the ocean,
• 29:31
  Speaker 1: you can use wave equations describe those ways, but really
• 29:33
  Speaker 1: you know that underneath there's you know, little particles of
• 29:36
  Speaker 1: water bumping against each other and propagating energy and pulling
• 29:41
  Speaker 1: on each other. Right, So it's like the wave equations
• 29:44
  Speaker 1: work and they start tell you what's going on, but
• 29:46
  Speaker 1: they maybe don't tell you about the nature of what's
• 29:48
  Speaker 1: going on underneath.
• 29:49
  Speaker 2: That's right, but sometimes they're actually better at answering questions.
• 29:52
  Speaker 2: Depends on the question you're asking. If you're asking questions
• 29:55
  Speaker 2: about waves and why they reflect or why they break,
• 29:58
  Speaker 2: then the answer is better described in terms of the
• 30:00
  Speaker 2: macroscopic why the waves break. It's because as they approach
• 30:03
  Speaker 2: the shore, part of them get dragged. You can't really
• 30:06
  Speaker 2: answer that question using the microscopic picture of waves as
• 30:09
  Speaker 2: tiny particles. You get lost in the details. So the
• 30:12
  Speaker 2: answer depends on the question you're asking. Which theory of
• 30:14
  Speaker 2: physics you want to use, which approximation, which details you
• 30:17
  Speaker 2: want to sweep under the rug depends on the question
• 30:19
  Speaker 2: you're asking, because fundamentally we don't know the deepest theory
• 30:23
  Speaker 2: of the universe, So in that sense, we can't answer
• 30:25
  Speaker 2: any questions. We always got to zoom out to some
• 30:27
  Speaker 2: level and give the appropriate answer based on the question.
• 30:30
  Speaker 1: Right right. But I feel like John's question here is
• 30:32
  Speaker 1: trying to get us to like, what is the nature
• 30:34
  Speaker 1: of things? Right? Like, I feel like we've just repeated
• 30:37
  Speaker 1: his question thus far, which is like, yeah, life has
• 30:40
  Speaker 1: different wavelengths, and some of them are shorter, some of
• 30:42
  Speaker 1: them are longer. Like, then what would you say then,
• 30:45
  Speaker 1: is the relationship between these oscillating electromagnetic fields and arrows
• 30:51
  Speaker 1: and maybe what we know now about the quantum particle
• 30:55
  Speaker 1: nature of things?
• 30:56
  Speaker 2: I mean, I think maybe you're more curious about the
• 30:58
  Speaker 2: quantum nature John wanted to know about micro wave But
• 31:01
  Speaker 2: you know, in terms of the quantum nature, quantum theory
• 31:03
  Speaker 2: of electrodynamics is a natural successor of classical electrodynamics. Like
• 31:08
  Speaker 2: you take Maxiwell's equations for electromagnetic fields and you quantize them.
• 31:12
  Speaker 2: You say, well, they can't just have any value, they
• 31:14
  Speaker 2: have to have limited values, And you end up with
• 31:16
  Speaker 2: photons packets minimum bundles of energy in the field instead
• 31:20
  Speaker 2: of arbitrary size energies. In classical theory, you can have
• 31:24
  Speaker 2: as dim light as you want, but in quantum theory
• 31:27
  Speaker 2: you can't. There's a minimum there. It's because there's additional mathematics.
• 31:31
  Speaker 2: So there's definitely a relationship between like the wave function
• 31:34
  Speaker 2: of a photon and the classical wave length of a
• 31:38
  Speaker 2: beam of light. And we're actually going to talk about
• 31:40
  Speaker 2: that in an episode coming up soon where we talk
• 31:42
  Speaker 2: about like how long is a photon? But I think
• 31:45
  Speaker 2: to answer John's question here about like why can mesh
• 31:48
  Speaker 2: holes block microwaves, we only need to use classical physics.
• 31:52
  Speaker 1: All right, Well, let's answer that question then, because he
• 31:54
  Speaker 1: asked that directly, like why is it that some waves
• 31:57
  Speaker 1: can pass through holes and others not?
• 31:58
  Speaker 2: This is a really cool ques question, and actually a
• 32:01
  Speaker 2: very difficult one. A simpler version of the question is
• 32:03
  Speaker 2: much more simple, like why does a metal box at
• 32:07
  Speaker 2: all block radiation? The microwave is encased in a metal
• 32:10
  Speaker 2: box to protect you from the radiation, but you might wonder,
• 32:12
  Speaker 2: like how do the metal box block radiation? Like when
• 32:15
  Speaker 2: you get into an elevator, why you have no cell
• 32:18
  Speaker 2: phone signal. It's the same question. And this is a
• 32:20
  Speaker 2: simple process called a Faraday cage. Anything that's a conductor
• 32:24
  Speaker 2: that has electrons roaming around in it. If you try
• 32:27
  Speaker 2: to pass an electrical signal through that conductor, the electrons
• 32:31
  Speaker 2: inside the conductor are going to rearrange themselves to basically
• 32:34
  Speaker 2: cancel out that electromagnetic radiation. Because there are electrons free
• 32:39
  Speaker 2: to move. The radiation creates electric fields that pushes the
• 32:42
  Speaker 2: electrons to counteract that electric field. So you basically can't
• 32:47
  Speaker 2: have an electric field inside a conductor. And so you
• 32:50
  Speaker 2: build a metal box. You can put your phone inside,
• 32:52
  Speaker 2: for example, it'll get no signal and also nobody can
• 32:55
  Speaker 2: spy on you. So that's how a Faraday cage works
• 32:58
  Speaker 2: if it has no holes in it.
• 33:00
  Speaker 1: Because the box, i guess, is made out of stuff,
• 33:03
  Speaker 1: and that stuff blocks the light trying to get in.
• 33:05
  Speaker 2: Yeah, exactly. And it's not just that it blocks light, right,
• 33:08
  Speaker 2: you know, materials can block light, but metal can also
• 33:11
  Speaker 2: block invisible radio waves that could pass through walls, they
• 33:14
  Speaker 2: just can't pass through metal.
• 33:16
  Speaker 1: So for a given metal box, there's no wave of
• 33:20
  Speaker 1: light that can penetrate it.
• 33:21
  Speaker 2: It depends on the wavelength and the thickness of the box,
• 33:24
  Speaker 2: Like there is a depth that electromagnetic radiation can penetrate
• 33:28
  Speaker 2: into various conductors. So like a super high intensity beam
• 33:32
  Speaker 2: or the right wavelength might be able to penetrate some
• 33:35
  Speaker 2: metal boxes depending on their thickness. But for a perfect conductor,
• 33:39
  Speaker 2: then yes, you have to have zero electromagnetic field inside
• 33:42
  Speaker 2: of it.
• 33:43
  Speaker 1: Okay, So then what happens in like in my microwave
• 33:45
  Speaker 1: that if you punch holes in this box?
• 33:48
  Speaker 2: Yeah, so you might wonder, Okay, there's holes in the box.
• 33:50
  Speaker 2: Why can't like go through the holes and be blocked
• 33:52
  Speaker 2: by the mesh?
• 33:53
  Speaker 3: Right?
• 33:54
  Speaker 2: Am I just getting like patchy radiation through the holes? Amazingly,
• 33:57
  Speaker 2: You're not. Even though there are holes in that none
• 34:00
  Speaker 2: of the light gets through.
• 34:02
  Speaker 1: Well, some light gets through, because I can see inside
• 34:04
  Speaker 1: my microwave.
• 34:04
  Speaker 2: That's right. None of the microwaves get through. The light
• 34:06
  Speaker 2: actually does get through. And so now it depends on
• 34:09
  Speaker 2: the frequency of the light. And I think in John's question,
• 34:12
  Speaker 2: he's wondering, like, is that because the light is like
• 34:15
  Speaker 2: oscillating sideways and so it can't fit through the mesh.
• 34:19
  Speaker 2: And the answer to that is no, that's misleading, right,
• 34:21
  Speaker 2: light is not oscillating sideways. Microwaves or visible light in
• 34:25
  Speaker 2: right through the center of one of those holes. They
• 34:27
  Speaker 2: can both fit through the hole. It's not a physical issue.
• 34:30
  Speaker 2: They're not like bumping up against the size of the hole.
• 34:32
  Speaker 2: It's a different effect. That's filtering out the microwaves and
• 34:36
  Speaker 2: not the visible light.
• 34:37
  Speaker 1: So then what is that effect?
• 34:38
  Speaker 2: Yeah, so what's going on there is a little bit
• 34:39
  Speaker 2: more subtle. What has to happen is you have to
• 34:42
  Speaker 2: have zero electric field inside the mesh. Like everywhere you
• 34:45
  Speaker 2: have metal, you have conductor, you have electrons. That's going
• 34:48
  Speaker 2: to zero out the field. Now you need to think
• 34:50
  Speaker 2: of the light not as a particle, not like as
• 34:52
  Speaker 2: one little thing that's like a tennis ball flying through
• 34:54
  Speaker 2: the hole, but like a wave. And when a wave
• 34:57
  Speaker 2: meets a new kind of material, like when light it
• 35:00
  Speaker 2: hits glass or when light hits water, right, then you
• 35:03
  Speaker 2: have to find a solution that satisfies all the wave
• 35:05
  Speaker 2: equations at the boundaries. What that really means is that
• 35:08
  Speaker 2: the waves have to line up. Remember we talked about
• 35:11
  Speaker 2: the waves as wiggles in the field. Well, you can't
• 35:14
  Speaker 2: have weird discontinuities in the field. They have to match
• 35:17
  Speaker 2: up at that boundary. This is why, for example, light
• 35:21
  Speaker 2: bends when it goes from air to glass or water,
• 35:23
  Speaker 2: because the different medium means a different index of refraction,
• 35:27
  Speaker 2: which means a different wavelength. So for two fields to
• 35:30
  Speaker 2: match at the boundary when they have a different wavelength,
• 35:34
  Speaker 2: one of them has to be bent relative to the
• 35:36
  Speaker 2: other at a different angle. The same principle applies here
• 35:40
  Speaker 2: with the case of the mesh, but it's much harder
• 35:42
  Speaker 2: to find solutions on both sides of the mesh because
• 35:46
  Speaker 2: the mesh requires the field to be zero at so
• 35:49
  Speaker 2: many places on it, and in this case, requiring that
• 35:52
  Speaker 2: the electromagnetic field is zero inside the mesh creates these
• 35:56
  Speaker 2: interference effects that can slowt any electromagnetic fields below a
• 36:00
  Speaker 2: certain wavelength on the other side of the mesh.
• 36:03
  Speaker 1: Okay, you lost me a little bit there. I wonder
• 36:05
  Speaker 1: if we've lost our listeners. So maybe maybe a more
• 36:08
  Speaker 1: simple scenario. Let's say I'm a markwave and I'm flying
• 36:11
  Speaker 1: through space and I see a big metal sheet in
• 36:14
  Speaker 1: front of me with a little tiny hole in it.
• 36:16
  Speaker 1: Now earlier saying that I should be able to go
• 36:18
  Speaker 1: through it because I don't really have any width to
• 36:20
  Speaker 1: me right like, the wavelength of my light is not
• 36:24
  Speaker 1: sideways to me. It's more like how often I'm pulsing?
• 36:30
  Speaker 1: Right A, Technically I could still go through that hole.
• 36:33
  Speaker 2: You have no width to you.
• 36:34
  Speaker 1: Yes, yeah, I'm a beam of light. If I'm a microwave,
• 36:37
  Speaker 1: why can't I go through that little hole?
• 36:39
  Speaker 2: Yeah, it sounds like you should be able to. But
• 36:41
  Speaker 2: you're actually using a particle picture, right. You're thinking of
• 36:44
  Speaker 2: yourself as having one location and flying through space, But
• 36:48
  Speaker 2: we're talking about waves, and waves have to have solutions
• 36:51
  Speaker 2: everywhere in space. So you have to find a solution
• 36:54
  Speaker 2: that satisfies all the equations everywhere in space. It's not
• 36:57
  Speaker 2: about an individual particle flying through space. It's like a
• 37:00
  Speaker 2: steady state. You have like waves in this box and
• 37:02
  Speaker 2: they're bouncing around. Can any of them escape?
• 37:05
  Speaker 1: Didn't we talk about like a single beam of light
• 37:08
  Speaker 1: being like one row in a stadium that's doing the
• 37:11
  Speaker 1: wave like it's super thin. Couldn't that wave go through
• 37:15
  Speaker 1: a little hole?
• 37:15
  Speaker 2: Yeah, it's one row, But you have to think about
• 37:17
  Speaker 2: the whole row, right, You have to think about the
• 37:19
  Speaker 2: equations of the whole row and the wather. The equations
• 37:21
  Speaker 2: work on one side of the mesh and the other
• 37:23
  Speaker 2: side of the mesh. It's a little bit unsatisfactory because
• 37:26
  Speaker 2: it's all about these interference terms, satisfying the equations. It's
• 37:30
  Speaker 2: hard to get a physical intuition on it. The best
• 37:32
  Speaker 2: I can do is to remind you that when you
• 37:34
  Speaker 2: approach that mesh, you're not just flying through it, right,
• 37:38
  Speaker 2: You're inducing electromagnetic fields in nearby and so you need
• 37:41
  Speaker 2: a solution on both sides, and that effectively induces light
• 37:44
  Speaker 2: in lots of different directions. And there's the requirement that
• 37:48
  Speaker 2: the electric field be zero inside the mesh, means that
• 37:51
  Speaker 2: you can't have wavelengths that are longer than that because
• 37:54
  Speaker 2: it will hit that zero requirement and get canceled out.
• 37:58
  Speaker 2: This is the same issue with like thinking about how
• 38:00
  Speaker 2: like it's bent at an interface, Like, how does that
• 38:02
  Speaker 2: actually happen? How does an individual photon get bent? How
• 38:05
  Speaker 2: all the photons bent the same way? It's the photon
• 38:08
  Speaker 2: picture that's the problem. Is really there's a wave description here,
• 38:11
  Speaker 2: and it's the solutions to the wave equations that dictate
• 38:14
  Speaker 2: what happens. So the problem is thinking about it in
• 38:17
  Speaker 2: terms of like a little particle flying through.
• 38:19
  Speaker 1: You're right, that is a very unsatisfied. It's hard to
• 38:22
  Speaker 1: tackle in a podcast, but I think what you're saying
• 38:25
  Speaker 1: is that instead of thinking about this in a time
• 38:28
  Speaker 1: sequential way, like I'm in one side of the wall
• 38:31
  Speaker 1: with a hole in it, and then later I'm on
• 38:33
  Speaker 1: the other side of the wall with the hole in it.
• 38:36
  Speaker 1: You because you're talking about waves, you kind of have
• 38:38
  Speaker 1: to think about it all at the same time, Like
• 38:40
  Speaker 1: the before and the after all had to be part
• 38:42
  Speaker 1: of the same physical consistency. And somehow if my wavelength
• 38:47
  Speaker 1: is too big, I just can't go through that hole,
• 38:50
  Speaker 1: Like there's no solution that puts me in both sides
• 38:52
  Speaker 1: of the hole in the timeline of the universe.
• 38:55
  Speaker 2: Yeah, exactly. And you can actually escape this requirement a
• 38:57
  Speaker 2: tiny bit if you send little pulses, Like if you
• 39:00
  Speaker 2: said individual tiny little pulses are microwaves, some of them
• 39:03
  Speaker 2: will get through, but it's when you have a consistent
• 39:06
  Speaker 2: source of the microwaves. It's like the previous ones are
• 39:09
  Speaker 2: canceling out the future ones, and they're all interfering with
• 39:11
  Speaker 2: each other in just the right way to cancel any
• 39:14
  Speaker 2: waves that make it through. Individual pulses actually can get
• 39:18
  Speaker 2: through a little bit, so you're exactly right. You have
• 39:20
  Speaker 2: to think about, like the steady state solution, all the
• 39:22
  Speaker 2: waves working together, can any of them make it through?
• 39:26
  Speaker 2: So it's really it's an interference.
• 39:27
  Speaker 1: Effect, like the before and the after at the same time.
• 39:30
  Speaker 1: So I think to answer John's question, I mean he
• 39:32
  Speaker 1: is asking, I think about the physical reality of wavelength
• 39:35
  Speaker 1: and what's really the nature of these things. Maybe the
• 39:37
  Speaker 1: answer is that the you know, light has this wave nature,
• 39:40
  Speaker 1: and this wave nature is not just in space, it's
• 39:43
  Speaker 1: also in time. And so for whatever reason, the nature
• 39:47
  Speaker 1: of light means that you have to take into account
• 39:49
  Speaker 1: the path and the future all at the same time,
• 39:51
  Speaker 1: and it all has to work together with the effects
• 39:53
  Speaker 1: of the electromagnetic interactions with the wall exactly.
• 39:57
  Speaker 2: And this wave picture of light really can't explain all
• 40:00
  Speaker 2: these kinds of effects. Light bouncing off of water, light
• 40:03
  Speaker 2: refracting in water, and also light being trapped by Faraday cages.
• 40:08
  Speaker 1: Well, I feel like it's a bit of an unsatisfied
• 40:10
  Speaker 1: answer for John.
• 40:10
  Speaker 2: Here.
• 40:11
  Speaker 1: Basically the answer is because you can't.
• 40:14
  Speaker 2: The answer is that, like the mental picture of light
• 40:17
  Speaker 2: moving as a little particle isn't really the right way
• 40:19
  Speaker 2: to think about this problem. And unfortunately you need different
• 40:23
  Speaker 2: mental models to solve different problems. There's no single unifying
• 40:26
  Speaker 2: understanding of physics that we can use in every situation.
• 40:29
  Speaker 1: All right, well, thank you John for that question. Now
• 40:32
  Speaker 1: let's get to our last question of the day, and
• 40:34
  Speaker 1: this one is about quasi particles and crossword puzzles. So
• 40:38
  Speaker 1: let's dig into that, but first let's take another quick break.
• 40:53
  Speaker 1: All right, we're answering questions here today, and our last
• 40:56
  Speaker 1: question comes from Peter.
• 40:58
  Speaker 5: Hi, Daniel and Jorge from Winchester, Massachusetts. My question comes
• 41:02
  Speaker 5: from a crossword puzzle. The clue was type of quasi
• 41:06
  Speaker 5: particle and had to be seven letters. The answer turned
• 41:10
  Speaker 5: out to be plasmon p L A S M O N.
• 41:13
  Speaker 5: Could you explain what that is?
• 41:15
  Speaker 2: Thank you?
• 41:16
  Speaker 1: All right, interesting questions here. Peter was doing a crossword
• 41:20
  Speaker 1: puzzle and he came across an interesting solution, which is
• 41:24
  Speaker 1: a plasmon, and so he's wondering what is that? Or
• 41:33
  Speaker 1: maybe Peter just made a mistake on his crossword puzzle.
• 41:36
  Speaker 2: No, I think he's exactly right. A plasmon is a
• 41:38
  Speaker 2: quaniti particle and it has seven letters. So boom boom boom.
• 41:41
  Speaker 1: Oh all right, well, I would have to look at
• 41:43
  Speaker 1: the whole crossword puzzle to double check that answer. Sometimes
• 41:47
  Speaker 1: crossword puzzles have multiple answers.
• 41:49
  Speaker 2: Hmm, that's true. Yeah, there might be many quasi particles
• 41:52
  Speaker 2: that satisfy this.
• 41:53
  Speaker 1: Yeah. No, they actually designed I think they even call
• 41:56
  Speaker 1: them like quantum crossword puzzles where there's like multiple solutions
• 42:01
  Speaker 1: that can fit.
• 42:02
  Speaker 2: Oh my gosh, like crosswands interfering crosswands. Yeah.
• 42:06
  Speaker 1: Yeah, and they have wavelengths and time moves slower. That's
• 42:09
  Speaker 1: the whole thing. All right, Well, it sounds like plasmon
• 42:14
  Speaker 1: is a real thing. What is it, Daniel, And just
• 42:16
  Speaker 1: to spell it out, Peter spells it out, plasmmm.
• 42:22
  Speaker 2: A plasmon is a quasi particle. It's like an oscillation
• 42:27
  Speaker 2: in plasmas that we can describe using the mathematics of particles.
• 42:32
  Speaker 2: Usually when we talk about particles, we're talking about oscillations
• 42:36
  Speaker 2: in fields like the electromagnetic field or an electron is
• 42:40
  Speaker 2: the oscillation in the electron field, and we have wave
• 42:44
  Speaker 2: equations to describe how those fields oscillate and how they vibrate,
• 42:48
  Speaker 2: and how the Higgs boson affects them to give them
• 42:50
  Speaker 2: mass and all that kind of stuff. You can imagine
• 42:52
  Speaker 2: like a little standing wave in the electron field. That's
• 42:56
  Speaker 2: what an electron is. So when we talk about particles,
• 42:59
  Speaker 2: we have math. It describes the oscillation of these fundamental fields.
• 43:03
  Speaker 2: We don't know what these fields are, what really is
• 43:06
  Speaker 2: doing the oscillating. That's the math we have. We can
• 43:09
  Speaker 2: take that same mathematics and we can apply it to
• 43:11
  Speaker 2: things that are not fundamental fields, like you can apply
• 43:14
  Speaker 2: it to sound waves in air, or you can apply
• 43:18
  Speaker 2: it to electrons moving through materials. You can apply in
• 43:21
  Speaker 2: lots of situations, and those are quasi particles. So particles
• 43:26
  Speaker 2: are these particular kinds of oscillations in fundamental fields. Quasi
• 43:30
  Speaker 2: particles are the same kind of mathematics, the same kind
• 43:32
  Speaker 2: of oscillations, but in something that isn't a fundamental field.
• 43:36
  Speaker 1: But then you can apply that to real things that
• 43:39
  Speaker 1: are made out of things like water and air. Right,
• 43:42
  Speaker 1: you can sort of apply those wave functions to media.
• 43:46
  Speaker 2: Yeah, exactly. And the cool thing about a particle is
• 43:49
  Speaker 2: that it's persistent, right, It's that quantized. You can count it.
• 43:52
  Speaker 2: It's discrete, and it like moves through the universe. An
• 43:56
  Speaker 2: electron as it moves to the universe, doesn't like dissipate
• 43:58
  Speaker 2: down into little many electron ripples. Right. It's persistent in
• 44:02
  Speaker 2: this way, and so sometimes you can see the same
• 44:05
  Speaker 2: thing happening in other media, right, Like if you can
• 44:08
  Speaker 2: make a smoke ring that's really persistent, right, it like
• 44:10
  Speaker 2: flows to the universe and holds itself together somehow. I mean,
• 44:14
  Speaker 2: I'm not an expert in how smoke rings work, but
• 44:16
  Speaker 2: imagine that. Then you could maybe describe that using the
• 44:18
  Speaker 2: same kind of mathematics you could use to describe electrons.
• 44:22
  Speaker 2: So you might call that a smoke on or whatever.
• 44:25
  Speaker 1: But it maybe just even more typical like a wave
• 44:29
  Speaker 1: in the ocean. You can use wave equations to describe them,
• 44:32
  Speaker 1: mm hmmm, and they're just ripples in the body of water.
• 44:35
  Speaker 1: So in a way, they're sort of just like water ons. Right.
• 44:38
  Speaker 2: Yes, not every wave phenomenon can describe a particle like
• 44:41
  Speaker 2: a particle's a special kind of persistent, discrete wave phenomenon.
• 44:46
  Speaker 2: But yeah, in the end, it's all rooted in wave
• 44:48
  Speaker 2: descriptions of how a medium is moving. And we talk
• 44:52
  Speaker 2: about sound waves as like phonons. It's like a basic
• 44:56
  Speaker 2: unit of the sound wave. Can you describe all sound
• 44:58
  Speaker 2: in terms of these like sound quasi particles. That's what
• 45:02
  Speaker 2: a phonon is.
• 45:05
  Speaker 1: Where I guess if we're following the same convention here,
• 45:07
  Speaker 1: it would be aerons perhaps depending on what the or gasons.
• 45:13
  Speaker 2: Yeah, if you want to reinvent stuff that already has
• 45:15
  Speaker 2: names for it so that everybody gets totally confused, then perfect.
• 45:18
  Speaker 1: Yes, Yeah, to make it clearer. Perhaps there is.
• 45:21
  Speaker 2: A thing called phonons, and there's lots of these quasi particles.
• 45:25
  Speaker 2: People are discovering new ones all the time. You know.
• 45:27
  Speaker 2: There's things called anions, and plasmons are an example of
• 45:32
  Speaker 2: a quasi particle. There are particular kinds of oscillations. But
• 45:37
  Speaker 2: in plasma, so plasma is just gas that's really really hot,
• 45:42
  Speaker 2: Like take hydrogen. It's got a proton and an electron.
• 45:45
  Speaker 2: The electron is bound to the proton because it doesn't
• 45:47
  Speaker 2: have the energy to fly away. Well, if you give
• 45:50
  Speaker 2: that electron more energy so that it's moving like too
• 45:53
  Speaker 2: fast to be bound by the proton, then it's free
• 45:56
  Speaker 2: and now you have a gas of protons and electrons
• 45:59
  Speaker 2: instead of a gas of hydrogen. That's a plasma.
• 46:02
  Speaker 1: Now it is a plasma. Then basically a phonon in plasma.
• 46:06
  Speaker 2: Well, the phonon is like a density wave, and that's
• 46:09
  Speaker 2: ignoring the charge distribution. Plasma is a little bit more
• 46:13
  Speaker 2: than that because it also has to do with the
• 46:14
  Speaker 2: charge distribution, because once you have a gas that has
• 46:18
  Speaker 2: charges in it, there's more kinds of forces that it
• 46:21
  Speaker 2: can feel like hydrogen pressure passes through it because the
• 46:24
  Speaker 2: particles are bumping up against each other. But in a plasma,
• 46:28
  Speaker 2: pressure can move through it because the charges are repelling
• 46:31
  Speaker 2: and attracting each other. So you have it's sort of
• 46:34
  Speaker 2: like two gases on top of each other. You have
• 46:35
  Speaker 2: a positive and a negative gas on top of each other,
• 46:38
  Speaker 2: and they're pushing and pulling on each other. If everything
• 46:41
  Speaker 2: has infinite time to sit around, it'll equilibrate, but that's
• 46:46
  Speaker 2: not usually what happens. You form these things in high
• 46:48
  Speaker 2: intensity situations. You have pulses in them, et cetera. And
• 46:51
  Speaker 2: so plasma is a description of the oscillation of mostly
• 46:54
  Speaker 2: the electrons, but also a little bit of protons due
• 46:57
  Speaker 2: to the charges of these things.
• 47:00
  Speaker 4: HM.
• 47:00
  Speaker 1: So you have this plasma of electrons and protons floating around,
• 47:04
  Speaker 1: flying around, and sometimes because of the dynamics between the
• 47:06
  Speaker 1: different particles, you get these weird little effects that move
• 47:11
  Speaker 1: around like they were particles inside of the plasma, and
• 47:14
  Speaker 1: that's what you call a plasma exactly.
• 47:16
  Speaker 2: And that's actually related to the previous question because the
• 47:19
  Speaker 2: reason these electrons are moving is because there's an electric field.
• 47:23
  Speaker 2: Often the electric field is because the electrons are separated
• 47:26
  Speaker 2: from the protons, so they've created an electric field between them.
• 47:29
  Speaker 2: So now the electrons move to try to balance out
• 47:32
  Speaker 2: that electric field that they had a part in making.
• 47:35
  Speaker 2: But sometimes they overshoot and so they oscillate back and
• 47:38
  Speaker 2: forth and back and forth. So you get all these
• 47:40
  Speaker 2: sort of like oscillations of the electrons because of their
• 47:44
  Speaker 2: charge differential, and those oscillations we can call plasmads. This
• 47:49
  Speaker 2: is like people trying to make connections between different fields
• 47:51
  Speaker 2: of physics. They're like, oh, people have all these cool
• 47:53
  Speaker 2: mathematical tools they can use to describe waves as particles.
• 47:57
  Speaker 2: Maybe if we apply that to our situation, we'll try
• 47:59
  Speaker 2: to gain some understanding. This is all about like emergent physics,
• 48:03
  Speaker 2: Like should we take a step up from the microphysics
• 48:06
  Speaker 2: and try to understand the bigger picture immersion phenomenon. Should
• 48:09
  Speaker 2: you think about the water particles or should you think
• 48:11
  Speaker 2: about the waves? Right? It depends again on the questions
• 48:14
  Speaker 2: you're asking and which tools you want to bring to bear.
• 48:17
  Speaker 2: We don't have a fundamental theory of physics that can
• 48:19
  Speaker 2: answer every question we can ask, so we have to
• 48:21
  Speaker 2: sort of choose, like how to zoom in, how to
• 48:23
  Speaker 2: zoom out, what approximations to make, what things to focus on,
• 48:26
  Speaker 2: what things to ignore. So plasmas can be useful for
• 48:29
  Speaker 2: some kinds of questions in plasma physics.
• 48:32
  Speaker 1: Like what kinds of questions? Like what are these useful for?
• 48:35
  Speaker 2: Like how do keep plasma stable? You know, in magnetic
• 48:38
  Speaker 2: confinement fusion, when you get plasmas really really hot and
• 48:40
  Speaker 2: you hope that the protons will fuse sometimes and then
• 48:43
  Speaker 2: create more fusion, you're really interested in these kinds of oscillations.
• 48:47
  Speaker 2: The thing that makes magnetic confinement and fusion difficult is
• 48:51
  Speaker 2: that plasmas are really hard to keep stable. They're very
• 48:54
  Speaker 2: turbulent and very chaotic. So understanding the oscillations and a plasma,
• 48:58
  Speaker 2: how to keep those stable high, to keep those from
• 49:00
  Speaker 2: spiraling out of control and creating chaos that breaks up
• 49:03
  Speaker 2: the plasma and ruins the fusion conditions can really help
• 49:07
  Speaker 2: you build like a long lasting fusion reaction, which is
• 49:10
  Speaker 2: the whole idea of magnetic confinement fusion.
• 49:13
  Speaker 1: That's kind of the holy grail of fusion, right, it
• 49:15
  Speaker 1: was super clean energy that will last us forever. Like
• 49:19
  Speaker 1: we can control plasma and then we can basically replicate
• 49:22
  Speaker 1: what's going on inside the sun.
• 49:23
  Speaker 2: Yeah, that's exactly right. We need to understand plasma oscillations
• 49:26
  Speaker 2: if we have any hope of keeping plasma stable and
• 49:29
  Speaker 2: getting fusion, which is the energy source of the universe
• 49:32
  Speaker 2: in the end. So plasmas can be really helpful for
• 49:35
  Speaker 2: answering some questions about plasmas.
• 49:39
  Speaker 1: And crossword puzzles. Apparently, I wonder which one is more
• 49:42
  Speaker 1: useful to humanity.
• 49:44
  Speaker 2: I don't know, but maybe you and Peter can answer
• 49:46
  Speaker 2: these crossword puzzles as you drink mohtos on your private island.
• 49:50
  Speaker 1: That sounds wonderful. It's going to be me, Dan, John
• 49:52
  Speaker 1: and Peter drinking mojitos solving crossword puzzles in my private
• 49:57
  Speaker 1: island while we get wiser and older.
• 50:01
  Speaker 2: That sounds good to me.
• 50:02
  Speaker 1: Wait, wait, are you Dan or not? Were you just
• 50:05
  Speaker 1: happy for us?
• 50:07
  Speaker 2: I'm the quantum interference between Dan and Daniel.
• 50:10
  Speaker 1: Yeah, I need to know which one we're getting here.
• 50:13
  Speaker 1: All right. Well, those are three awesome questions we've answered today.
• 50:16
  Speaker 1: Thank you to all of our question askers.
• 50:18
  Speaker 2: And thanks to everybody who writes in with questions about
• 50:20
  Speaker 2: the universe. Keep thinking deeply, keep asking questions, and don't
• 50:24
  Speaker 2: give up until it makes sense to you.
• 50:26
  Speaker 1: And or you get an answer from Daniel or us
• 50:29
  Speaker 1: on the podcast that's right, or maybe shows up in
• 50:32
  Speaker 1: a crossword puzzle. Either way to thrill.
• 50:34
  Speaker 2: And if you don't hear from me, feel free to
• 50:36
  Speaker 2: look up poor his address and take him up on
• 50:38
  Speaker 2: his invitation to the private island.
• 50:40
  Speaker 1: Yeah there you go. All right, Well, we hope you
• 50:42
  Speaker 1: enjoyed that. Thanks for joining us, See you next time.
• 50:50
  Speaker 2: For more science and curiosity, come find us on social
• 50:53
  Speaker 2: media where we answer questions and post videos. We're on Twitter, Discord, Instant,
• 50:58
  Speaker 2: and now TikTok. Thanks for listening, and remember that Daniel
• 51:01
  Speaker 2: and Jorge Explain the Universe is a production of iHeartRadio.
• 51:05
  Speaker 2: For more podcasts from iHeartRadio, visit the iHeartRadio app, Apple Podcasts,
• 51:10
  Speaker 2: or wherever you listen to your favorite shows.