Latest / Daniel and Kelly’s Extraordinary Universe / Listener Questions 6

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Listener Questions 6 · Daniel and Kelly’s Extraordinary Universe

0:08
Speaker 1: Are you the kind of person that wonders if black
0:11
Speaker 1: holes have air on them? Do you ever think about
0:14
Speaker 1: what it's like to be in a fighter jet and
0:17
Speaker 1: roll down the windows. Do you ever wonder if light gets,
0:20
Speaker 1: you know, tired, on its way across the universe from
0:24
Speaker 1: distant stars all the way to Earth. If so, then
0:27
Speaker 1: you're the right person to be listening to this podcast,
0:30
Speaker 1: because that's exactly the kind of stuff we're gonna be
0:32
Speaker 1: talking about today. Hi. I'm Daniel. I'm a particle physicist,
0:53
Speaker 1: and I'm the co author of the book We Have
0:55
Speaker 1: No Idea, A Guide to the Unknown Universe. My co author,
1:00
Speaker 1: Jorge him is usually the co host of this podcast,
1:03
Speaker 1: Daniel and Jorge Explain the Universe, brought to you by
1:06
Speaker 1: I Heart Radio. Today, Jorge has to be away, so
1:10
Speaker 1: I'm going to do the podcast by myself, and today
1:13
Speaker 1: we're doing something which is absolutely my favorite, which is
1:16
Speaker 1: answering listener questions. I love listener questions because they give
1:21
Speaker 1: me feedback and help me understand what people out there
1:24
Speaker 1: are thinking, what they're understanding, and what they're confused about.
1:28
Speaker 1: When Jorge and I do lectures live, we talk about
1:30
Speaker 1: all the amazing mysteries of the universe, and then people
1:34
Speaker 1: ask questions, and those questions are so valuable because they
1:37
Speaker 1: show me exactly what people have misunderstood. If I said
1:41
Speaker 1: something and I thought I was super clear and then
1:43
Speaker 1: somebody asked the question, it helps me see how to
1:46
Speaker 1: better explain something. So I really value listener questions. Thank
1:50
Speaker 1: you to everybody who has written in, either with a
1:53
Speaker 1: point of confusion about something that we said on the
1:55
Speaker 1: podcast or something totally crazy that they were thinking about
1:59
Speaker 1: and they wanted us to explain. And for all of
2:02
Speaker 1: you who have not written into the podcast, what are
2:05
Speaker 1: you waiting for? We want to hear your questions. When
2:07
Speaker 1: I say I answer every email, I mean it. And
2:10
Speaker 1: when I say I love getting questions from listeners, I
2:13
Speaker 1: am being totally serious. So please send us your questions
2:16
Speaker 1: two questions at Daniel and Jorge dot com. You might
2:19
Speaker 1: even hear yourself on the podcast. So today we'll be
2:22
Speaker 1: answering listener questions. Questions about lights, questions about black holes,
2:26
Speaker 1: questions about flying at the speed of sound with the
2:29
Speaker 1: windows open, and all these questions have something in common,
2:32
Speaker 1: which is they're sort of like what if questions, like
2:35
Speaker 1: how could you do this? Or how could you make
2:36
Speaker 1: this work? Or what would happen if you did this thing?
2:39
Speaker 1: And all of these reveal people's just desire to understand
2:43
Speaker 1: what happens in the universe, to reveal secrets of the
2:45
Speaker 1: universe by cooking up crazy scenarios, scenarios where Nature has
2:49
Speaker 1: to reveal the truth. And in the end, that's really
2:52
Speaker 1: what experimental physics is. We want to know the answer
2:56
Speaker 1: to a question, you know, does the universe work this
2:58
Speaker 1: way or that way? And so we come up with
3:00
Speaker 1: some scenario where nature has to reveal to us the answer.
3:04
Speaker 1: We corner nature and say, well, show us you know,
3:07
Speaker 1: it is light a particle or is it a wave?
3:10
Speaker 1: Does the Higgs boson have this much mass or that
3:12
Speaker 1: much mass? Really, all experimental physics is is constructing physical
3:16
Speaker 1: scenarios where Nature has to show us her cards. And
3:20
Speaker 1: so a lot of the questions you'll hear about today
3:22
Speaker 1: are exactly that kind of question. So today we have
3:25
Speaker 1: three questions. Let's dive in. Hey, guys, my question is
3:29
Speaker 1: what would happen if we quantum entangled two particles and
3:35
Speaker 1: took particle one and shot it into a black hole?
3:39
Speaker 1: Could we learn anything? And what do you think we
3:42
Speaker 1: could learn if we can from particle two. Shout out
3:47
Speaker 1: to South Dakota and LEXI. All right, I got this
3:50
Speaker 1: question and it blew my mind. And it blew my
3:52
Speaker 1: mind because it combines so many different things that I love.
3:55
Speaker 1: You've got black holes, you've got quantum mechanics, you got
3:59
Speaker 1: inventing new ways to explore the universe. Right, So I
4:02
Speaker 1: love when listeners think up new ideas for how we
4:05
Speaker 1: could solve ancient questions. All right, so first let's talk
4:08
Speaker 1: about why would we want to know what's going on
4:11
Speaker 1: inside a black hole? Like, why does anybody care? Isn't
4:13
Speaker 1: it just basically the garbage disposal of the universe, jammed
4:16
Speaker 1: filled with rejected matter that's got swashed down the toilet
4:20
Speaker 1: bowl and into the black hole. Well, that's what we
4:22
Speaker 1: don't know. General relativity tells us that black holes might
4:26
Speaker 1: have a singularity in the center of them, right, a
4:29
Speaker 1: tiny dot of matter with infinite density something, which is,
4:33
Speaker 1: you know, hard for us to imagine. What does infinite
4:35
Speaker 1: density mean? And but according to Einstein's equations, that's exactly
4:40
Speaker 1: the conditions you need to create a black hole. Fine,
4:43
Speaker 1: And we know that Einstein's equations have been validated many,
4:46
Speaker 1: many times, and nobody's ever found flaw on them. They
4:49
Speaker 1: predicted gravitational waves, we've seen them. They predicted all sorts
4:53
Speaker 1: of other crazy gravitational phenomena, and they've been verified and checked. So,
4:57
Speaker 1: as far as we know, Einstein's equations are correc except
5:01
Speaker 1: quantum mechanics tells us that you can't have a singularity
5:05
Speaker 1: at the center of a black hole. Remember, quantum mechanics
5:08
Speaker 1: tells us the universe is not smooth and continuous, instead
5:11
Speaker 1: of the universe is discrete. Space itself is probably pixelated
5:16
Speaker 1: into tiny little units. Right, Mass is probably pixelated, time
5:20
Speaker 1: is probably pixelated. All these things are probably discreete and
5:23
Speaker 1: not continuous, And that means you can't have an infinitely
5:27
Speaker 1: small dot, certainly not one with an infinite mass inside
5:30
Speaker 1: of it. In addition, there's all sorts of issues about
5:32
Speaker 1: the Heisenberg uncertainty principle. Can you have so much matter
5:35
Speaker 1: localized in one spot for such a long time. Quantum
5:39
Speaker 1: mechanics says that that you should not find a singularity
5:42
Speaker 1: inside a black hole. The problem, of course, is it's
5:45
Speaker 1: awfully difficult to look inside a black hole. So I
5:47
Speaker 1: think that's probably what motivates this question the desire to
5:50
Speaker 1: see what's inside a black hole. And I'll be honest,
5:53
Speaker 1: if I could see inside a black hole, I would
5:55
Speaker 1: do it in a second. I would love to know
5:57
Speaker 1: what is going on inside there, all right, it So
6:00
Speaker 1: the idea from this question is to quantum entangle two
6:04
Speaker 1: particles and shoot one into a black hole, and I
6:07
Speaker 1: guess use the other one to sort of learn something
6:10
Speaker 1: about what's going on inside the black hole. Right, well,
6:13
Speaker 1: let's talk about quantum entanglement. Quantum entanglement is a very
6:17
Speaker 1: tricky topic, and we discussed in some depth on our
6:19
Speaker 1: quantum Computing episode. The short version is that it links
6:23
Speaker 1: two particles potentially across gray distances or great barriers like
6:29
Speaker 1: the edge of a black hole. The link is a
6:31
Speaker 1: kind of constraint. If one particle spins up, the other
6:34
Speaker 1: one has to spin down. So by knowing something about
6:37
Speaker 1: one of the particles discovering that it's spin up, for example,
6:41
Speaker 1: you can learn something about the other, such as knowing
6:43
Speaker 1: that it's spin down, even if you never see it
6:46
Speaker 1: or can't possibly see it because it's hidden. So you
6:50
Speaker 1: see the attraction for potentially probing a black hole using
6:54
Speaker 1: pairs of entangled particles to sort of extract some information
6:59
Speaker 1: from one particle by looking at the other one. All right, Well,
7:02
Speaker 1: the short answer is we would learn nothing, And the
7:05
Speaker 1: reason is that there are pretty solid theorems about getting
7:08
Speaker 1: information out of the black hole. All right, So the
7:11
Speaker 1: no hair theorem, I'm not joking. It's literally called the
7:15
Speaker 1: no hair theorem, and I don't know if it was
7:17
Speaker 1: invented by a business without hair, but the no hair
7:20
Speaker 1: theorem says that the only information you can get about
7:23
Speaker 1: a black hole is its mass, it's total electric charge,
7:28
Speaker 1: and its momentum. That's it, right. You can't get any
7:31
Speaker 1: other information. Nothing that's going on inside the black hole
7:35
Speaker 1: can never leave, right, certainly can't see things escaping the
7:38
Speaker 1: black hole. Nothing can escape, so no light can come
7:41
Speaker 1: out to reveal to you what's inside the black hole.
7:43
Speaker 1: But more than that, you cannot get any information, no
7:46
Speaker 1: matter how clever you are, other than those three pieces
7:49
Speaker 1: of information. And this raises all sorts of fascinating questions,
7:53
Speaker 1: Like um, the listener was asking about quantum entangled particles
7:57
Speaker 1: where one is inside and one is outside the black hole.
7:59
Speaker 1: That act really happens already. There's something called hawking radiation
8:03
Speaker 1: or a photon inside the black hole will decay to
8:07
Speaker 1: two quantum entangled particles, and the decay will happen so
8:10
Speaker 1: close to the event horizon that one of the particles
8:13
Speaker 1: slips out of the event horizon and gets to leave.
8:16
Speaker 1: That's Hawking radiation and requires this quantum fluctuation right right
8:20
Speaker 1: at the edge of the event horizon. And so you
8:22
Speaker 1: might ask, can we learn something about the side of
8:26
Speaker 1: the Hawking radiation that got slurred into the black hole
8:29
Speaker 1: by looking at what happens outside the black hole by
8:32
Speaker 1: measuring that Hawking radiation. Well, the answer is no, right,
8:36
Speaker 1: no information can leave the black hole. Is just impossible
8:39
Speaker 1: to extract any information. Even though that electron and that
8:42
Speaker 1: positron are entangled with each other, right, they do not
8:45
Speaker 1: contain any information about what's going on inside the black hole.
8:49
Speaker 1: And the shorter answer is, as soon as you're trying
8:51
Speaker 1: to interact with the electron impositron, you will anyway break
8:55
Speaker 1: that entanglement. Right. The entanglement only exists when those particles
8:58
Speaker 1: are isolated from the to the system. So as soon
9:01
Speaker 1: as you trying to measure something about that electron, you're
9:03
Speaker 1: probably going to break that entanglement anyway, which is usually
9:07
Speaker 1: usually the problem with entanglement is that you can't really
9:10
Speaker 1: use it to convey information because interacting with the particles
9:13
Speaker 1: breaks that entanglement. All Right, This brings us to another
9:17
Speaker 1: fascinating and current topic in black hole physics, which is
9:21
Speaker 1: people are wondering where the information goes. Like, according to
9:26
Speaker 1: black hole theories, no information can leave the black hole, right,
9:30
Speaker 1: But according to Hawking, radiation particles do escape the black hole,
9:34
Speaker 1: which means the black hole can shrink. In fact, for
9:37
Speaker 1: small black holes, black holes could even evaporate and disappear.
9:41
Speaker 1: So what happens to the information that went into the
9:44
Speaker 1: black hole? What happened to all that quant those quantum
9:48
Speaker 1: states and all that stuff that went into the black
9:50
Speaker 1: hole and then the black hole disappeared? Because there's another
9:54
Speaker 1: law of quantum mechanics that says It says that all
9:56
Speaker 1: the information about past states in the universe is contained
9:59
Speaker 1: in the ragement of the current universe, right, no information
10:02
Speaker 1: should be lost. For those mathematically inclined, this means essentially
10:06
Speaker 1: that the wave function is unitary, right. The transformations through
10:09
Speaker 1: times do not change the overall normalization of the wave function.
10:14
Speaker 1: So if black holes can evaporate and disappear, but no
10:18
Speaker 1: information can leave the black hole. That suggests that information
10:22
Speaker 1: is destroyed, and that particular puzzle goes by the name
10:25
Speaker 1: of the black hole information paradox. And people have proposed
10:29
Speaker 1: all sorts of crazy solutions to this, including firewalls and
10:32
Speaker 1: all sorts of crazy stuff that we might actually see
10:35
Speaker 1: at the edges of black holes one day. So thank
10:38
Speaker 1: you for this wonderful question about black holes and quantum
10:41
Speaker 1: mechanics and entanglement and information and all sorts of crazy,
10:45
Speaker 1: amazing stuff. One of my favorite things about these kinds
10:47
Speaker 1: of questions is that they seem theoretical, they seem crazy abstract,
10:51
Speaker 1: but these are real, like black holes, they're real objects.
10:54
Speaker 1: They are out there, and one day, if we build
10:57
Speaker 1: the right kind of spaceship and the right kind of probes,
10:59
Speaker 1: we could go when we could observe them, and we
11:01
Speaker 1: might learn the answers to some of these questions. So
11:04
Speaker 1: thanks for sending in that question, and keep writing. Well,
11:07
Speaker 1: this is a perfect spot to take a break. We'll
11:09
Speaker 1: be right back. This is a wonderful question that we
11:25
Speaker 1: got recently from a listener and from that listener's dad. Hi,
11:29
Speaker 1: my name is Phineas, and I'm in fourth grade and
11:32
Speaker 1: I live in Sico, Alaska. I was wondering, if you
11:35
Speaker 1: were in an airplane going faster on the speed of
11:37
Speaker 1: sound and you said something to the person next to you,
11:40
Speaker 1: would they actually be able to hear what you said.
11:44
Speaker 1: This is Phineas's dad. Phineas asked me this question a
11:47
Speaker 1: while ago, and it got me wondering if one was
11:50
Speaker 1: traveling at or above the speed of light, would they
11:54
Speaker 1: be able to see the person next to them? So
11:57
Speaker 1: I love this question for so many reasons. I love
12:00
Speaker 1: that that young boys imagining what it's like to be
12:03
Speaker 1: on a spaceship or what it's like to be on
12:05
Speaker 1: a plane traveling past the speed of sound. And it's
12:08
Speaker 1: a great question. He's wondering about how this information is processed,
12:12
Speaker 1: how this information is transmitted. Essentially, are you leaving that
12:15
Speaker 1: information behind right? Well, first of all, I want to
12:18
Speaker 1: break his bubble and say, if you're on a fighter
12:21
Speaker 1: jet that's traveling faster than the speed of sound, probably
12:24
Speaker 1: you don't have the windows open, right, which means that
12:27
Speaker 1: you're in a little air bubble. That air bubble is
12:29
Speaker 1: moving with you fast in the speed of sound. If
12:33
Speaker 1: you had the windows open and the air was rushing
12:35
Speaker 1: past you fasten the speed of sound, it would probably
12:38
Speaker 1: tear you to shreds. And that's why fighter jets, for example,
12:42
Speaker 1: have that little bubble right the window that protects them
12:45
Speaker 1: from what's going on outside. All right, so they have
12:48
Speaker 1: a little bubble of air. And that's the key, because
12:51
Speaker 1: sound is a wave, right, Sound is just vibrations of
12:55
Speaker 1: the air, and so what it does is it moves
12:58
Speaker 1: relative to the air. Right. It's like if you have
13:01
Speaker 1: a bathtub of water and you're slapping it to make
13:04
Speaker 1: to make waves, the waves move relative to the water.
13:08
Speaker 1: If that water, if that bathtub was on a train
13:11
Speaker 1: traveling a super duper fast, it wouldn't make any difference, Right,
13:14
Speaker 1: You could still have a bath and you can still
13:16
Speaker 1: make splashes and they wouldn't be any different. In the
13:19
Speaker 1: same way, if you're on a fighter jet and you're
13:22
Speaker 1: in a little bubble of air inside the fighter jet,
13:25
Speaker 1: you can turn to the person next to you, can
13:26
Speaker 1: say hello, would you please pass the peanuts or whatever
13:30
Speaker 1: you say to somebody in a fighter jet, and the
13:32
Speaker 1: air between you is not moving relative to you, so
13:35
Speaker 1: you can send waves through it normally, just as you
13:38
Speaker 1: would if you were sitting on your couch in your
13:40
Speaker 1: living room. So the sort of cheap answer to the
13:43
Speaker 1: question is that there's no difference if you're in a
13:46
Speaker 1: little bubble of air that's moving with you, all right,
13:49
Speaker 1: So that's no fun. Let's imagine what happens when you
13:52
Speaker 1: open the windows, right, You're going mocked too, You're zooming
13:56
Speaker 1: through the atmosphere. You open the windows, all of a sudden,
13:59
Speaker 1: the wind is screaming past you with two thousand miles
14:01
Speaker 1: per hour. Right now, that's an interesting question. What happens
14:04
Speaker 1: if you turn to your friend and you say, past
14:06
Speaker 1: the bananas? Right? Can they hear you? The key thing
14:10
Speaker 1: to remember is that sound moves at a fixed speed
14:13
Speaker 1: relative to the air. So if you shout into a
14:16
Speaker 1: wind blowing at your back, then your show gets carried
14:20
Speaker 1: away from you by the wind more quickly than if
14:22
Speaker 1: there had been no wind. Similarly, if the wind is
14:26
Speaker 1: blowing in your face, it can slow down your shout.
14:30
Speaker 1: If the wind blows in your face at the speed
14:32
Speaker 1: of sound, ouch, then when you scream, your scream doesn't
14:36
Speaker 1: actually go anywhere. It stays right there on top of you.
14:40
Speaker 1: So in the fighter jet, if the windshield is down
14:43
Speaker 1: or whatever they call it in a fighter jet, then
14:45
Speaker 1: they can just talk normally right there in a bubble
14:47
Speaker 1: of air. Just like if you're in a bathtub and
14:49
Speaker 1: you make waves. It doesn't matter if you're on a
14:51
Speaker 1: train at the time, because the water is moving with you.
14:54
Speaker 1: But if they open the windshield, the wind is whipping
14:58
Speaker 1: by them at faster than the speed of so sound,
15:00
Speaker 1: and so they will leave their words behind. There's no
15:04
Speaker 1: way that they can talk, even if they shout straightforwards.
15:07
Speaker 1: This is also why planes make sonic booms. If a
15:10
Speaker 1: plane is traveling faster than the sound it's making, then
15:13
Speaker 1: it's catching up to his own sound, and the sound
15:16
Speaker 1: from two seconds ago gets piled up on top of
15:18
Speaker 1: the sound from one second ago and the sound from
15:21
Speaker 1: right now. It's the same amount of sound total, doesn't
15:24
Speaker 1: generate more sound, but it gets concentrated in certain places
15:28
Speaker 1: because the plane is out racing the sound it's making.
15:31
Speaker 1: Just like with a boat in the water, if it
15:33
Speaker 1: travels faster than the waves in water, then those waves
15:37
Speaker 1: pile up and you get a wake. A sonic boom
15:39
Speaker 1: is just a plane's wake. Alright, awesome question, and my
15:44
Speaker 1: favorite part I think of this is that his dad
15:46
Speaker 1: couldn't help but jump in and ask even more physics equestion, right,
15:51
Speaker 1: a question about traveling at or faster than the speed
15:54
Speaker 1: of light. Wonderful and I love this because it allows
15:57
Speaker 1: us to draw this contrast between the speed of sound
16:00
Speaker 1: and the speed of light. Now, first of all, of course,
16:03
Speaker 1: you can't travel at the speed of light, right, Nothing
16:06
Speaker 1: that has mass can travel at the speed of light.
16:09
Speaker 1: Only things that are massless travel at the speed of light,
16:12
Speaker 1: and everything that's massless travels at the speed of light. Photons, gravitons,
16:18
Speaker 1: if they exist, anything that does not have mass has
16:21
Speaker 1: to travel at the speed of light, and always at
16:24
Speaker 1: the speed of light. Can't go any slower. The amazing
16:28
Speaker 1: thing about photons is not only that they travel at
16:31
Speaker 1: the speed of light, which is super dup or fast,
16:33
Speaker 1: but that they don't travel relative to some medium. Sound
16:37
Speaker 1: and water waves travel it's fixed speeds relative to their
16:40
Speaker 1: medium air or water, but the rules are totally different.
16:44
Speaker 1: For light. It's a wave, but it always moves at
16:47
Speaker 1: the speed of light relative to the person measuring it,
16:50
Speaker 1: not relative to the medium, because it doesn't have a medium. Now,
16:55
Speaker 1: for a while people thought that there has to be
16:57
Speaker 1: some medium that light traveled through, and they called it
17:00
Speaker 1: ether and searched for it. But now we know that
17:02
Speaker 1: there is no ether, no medium that's doing the waving
17:06
Speaker 1: for light like air does for sound. The Michaelson Morley
17:09
Speaker 1: experiments showed us that because they measured the speed of
17:12
Speaker 1: light in two different directions and found them to be identical,
17:16
Speaker 1: even though the Earth is obviously moving in one direction
17:18
Speaker 1: or the other as it goes around the Sun. The
17:21
Speaker 1: reason is because light doesn't have a medium. It's the
17:24
Speaker 1: waving of quantum fields that are the properties of space itself.
17:28
Speaker 1: So space can be empty and still have light in it.
17:31
Speaker 1: And the way we showed it is that we discovered
17:33
Speaker 1: that light moves at the speed of light relative to everybody,
17:37
Speaker 1: no matter how fast you're going. So if you are
17:40
Speaker 1: standing on Earth and you turn on a flashlight, those
17:43
Speaker 1: photons leave your flashlight at the speed of light. Right cool. Now,
17:48
Speaker 1: what happens if you jump into Lamborghini and you turn
17:51
Speaker 1: on a flashlight. Lamborghini is going to two miles per hour.
17:55
Speaker 1: You're in the Lamborghini, you turn on the flashlight. What happens, Well,
17:58
Speaker 1: the light leaves your fly light at the speed of
18:01
Speaker 1: light relative to you, No big deal. What about somebody
18:05
Speaker 1: on the ground, right, the person you left behind who
18:07
Speaker 1: you didn't offer a ride in your Lamborghini too? When
18:11
Speaker 1: they when you turn on the flashlight in your Lamborghini,
18:13
Speaker 1: how fast did they see the light going? Well, you
18:16
Speaker 1: might think, well, it's the speed of light plus the
18:18
Speaker 1: speed of the Lamborghini, right, because the flashlight itself is
18:21
Speaker 1: moving at two hundred miles. But that's where you'd be wrong. Right,
18:25
Speaker 1: That's whyw light is weird. That's how our whole universe
18:28
Speaker 1: is super bizarre. Frankly, it's bonkers. But we know that
18:32
Speaker 1: light always travels at the speed of light, no matter
18:35
Speaker 1: what the speed of the thing making it is, right,
18:38
Speaker 1: And everybody who measures the speed of light always sees
18:41
Speaker 1: it moving at the speed of light relative to them.
18:44
Speaker 1: And that's different from sound, right. Sound travels relative to
18:47
Speaker 1: a medium like air, and that's sort of an absolute
18:50
Speaker 1: reference frame. And sound always moves at the same speed
18:53
Speaker 1: relative to the air. And so if you're moving with
18:55
Speaker 1: respect of the air, like you're in a fighter jet,
18:57
Speaker 1: and you're moving at the speed of sound, if you
18:59
Speaker 1: screen sam, then you're moving with that sound. Right. So
19:02
Speaker 1: if you scream in a fighter jet and you're moving
19:05
Speaker 1: at the speed of sound, you can basically just like
19:07
Speaker 1: stay inside your scream. You can fly along through the
19:10
Speaker 1: air with your scream. That's not true with light, right,
19:14
Speaker 1: Light will always move at the speed of light relative
19:16
Speaker 1: to you. You turn on that flashlight, even if you
19:19
Speaker 1: were traveling very close to the speed of light, you
19:21
Speaker 1: couldn't stay with those photons. It would leave you at
19:24
Speaker 1: the speed of light. And so if you're traveling very
19:27
Speaker 1: close to the speed of light, because you can't travel
19:29
Speaker 1: at the speed of light, and you look next to you, right,
19:33
Speaker 1: and the person next to you has a flashlight, it's
19:35
Speaker 1: going to act totally normally for you, right, It doesn't
19:39
Speaker 1: matter what's happening outside. Light always travels at the speed
19:42
Speaker 1: of light relative to you. So the short I answer
19:45
Speaker 1: to your question is, if you're traveling nearly at the
19:48
Speaker 1: speed of light, then everything will feel normal inside your spaceship.
19:52
Speaker 1: Clocks will run normally. Everything will seem normal. Now if
19:55
Speaker 1: you look outside your spaceship, but things that are not
19:57
Speaker 1: traveling at that high speed, that's when relative he kicks in.
20:01
Speaker 1: Things seem to run slow and they seem to get shrunk. Right,
20:04
Speaker 1: But light always travels at the same speed no matter what.
20:09
Speaker 1: I hope that was an answer to your question. Thank
20:11
Speaker 1: you so much for writing in, Thank you for wondering
20:14
Speaker 1: about the universe, and thank you to all the parents
20:16
Speaker 1: out there who are sharing their wonderings about the universe
20:19
Speaker 1: with their kids and sharing this podcast with their kids
20:22
Speaker 1: and letting their kids ask us crazy, awesome, amazing, super
20:26
Speaker 1: fun questions about the universe that we totally love to answer.
20:31
Speaker 1: Let's get to our last question, but first, let's take
20:33
Speaker 1: a break. Okay, we're back and we're answering listener questions.
20:49
Speaker 1: Today we talked about zooming around at the speed of
20:52
Speaker 1: sound with the speed of light, and we talked about
20:54
Speaker 1: quantum entanglement and black holes, and our last question is
20:58
Speaker 1: also related to light and zoom across the universe. Here
21:01
Speaker 1: it is Hello, Daniel and Jorge. Hey, my name is
21:04
Speaker 1: Marcella and I'm forming a Jeanette Brazil. I'm a big
21:07
Speaker 1: fan of your podcast and your book. So my question
21:10
Speaker 1: is about how does light carry information or how exactly
21:15
Speaker 1: does a photon transmit or carry within itself a pixel
21:19
Speaker 1: so that we are able to see the images we
21:21
Speaker 1: see on our telescopes. How does it not disintegrate after
21:25
Speaker 1: traveling so far. Thank you so much. All right, that's
21:30
Speaker 1: not really one question. That's like a bunch of questions
21:32
Speaker 1: I'll stuck together but totally fair will answer all of them.
21:36
Speaker 1: The first part of the question was essentially what information
21:39
Speaker 1: does light carry? And I think the question is trying
21:41
Speaker 1: to ask, like, when you see a picture of like
21:44
Speaker 1: a distant star, what is it that the photon is carrying?
21:47
Speaker 1: How does it how does that picture come from the
21:50
Speaker 1: star and end up in my eyeballs or in my telescope. First,
21:53
Speaker 1: let's be really microscopic about it, right, What happens when
21:57
Speaker 1: you see a star is that you're seeing photons from
21:59
Speaker 1: that star. So somewhere really far away, billions of miles away,
22:03
Speaker 1: that big ball of fusion is shooting out photons. And
22:06
Speaker 1: once the photons leave the star, they have nothing to
22:09
Speaker 1: do with the star anymore. Right, they're flying through space
22:11
Speaker 1: and the fact that they came from the star is irrelevant.
22:13
Speaker 1: But they do carry information. They're pointing in a specific direction. Right.
22:18
Speaker 1: That's information. If you see light coming from one direction
22:21
Speaker 1: or another left versus right, it tells you where that
22:24
Speaker 1: object is. Right, So where in the sky the light
22:27
Speaker 1: is coming from is very important information to know where
22:30
Speaker 1: that star might be. So first piece of information light
22:33
Speaker 1: carries is its direction. Second very important piece of information
22:38
Speaker 1: is its energy. Every photon has a certain amount of energy,
22:41
Speaker 1: and this is the critical thing about photon. This is
22:43
Speaker 1: the reason we know photons exist, is that light comes
22:47
Speaker 1: in these little packets of energy. That's basically what a
22:49
Speaker 1: photon is. And the specific energy that a photon has
22:53
Speaker 1: also determines its frequency. Remember, photons their particles, their waves,
22:58
Speaker 1: but when you think about them as way, you have
23:00
Speaker 1: to think about them as sort of electromagnetic fluctuations, like
23:03
Speaker 1: vibrations in the electromagnetic field. Those vibrations have a certain frequency,
23:08
Speaker 1: and you probably heard of visible light having frequencies in
23:11
Speaker 1: the range of hundreds of nanometers. So every photon has
23:14
Speaker 1: a certain amount of energy. That energy determines a few
23:17
Speaker 1: things about the photon. It determines the frequency of the
23:20
Speaker 1: wiggles because remember photons are just electromagnetic waves and they're
23:24
Speaker 1: wiggling along through space their vibrations in the electromagnetic field
23:28
Speaker 1: or the quantum photon field, if you want to think
23:30
Speaker 1: about it in terms of quantum field theory. So it
23:33
Speaker 1: determines its frequency and also its wavelength, and in addition,
23:38
Speaker 1: those things determine the photons color. But color, of course,
23:41
Speaker 1: is something even more complicated. We're gonna have a whole
23:43
Speaker 1: episode about that soon what it means to see different colors.
23:47
Speaker 1: But essentially, the energy carries all this information. So so
23:50
Speaker 1: far we have a photon zooming through space, and it's
23:53
Speaker 1: carrying information about its direction, and it's carrying information about
23:56
Speaker 1: the energy, and that's most of the information you need
23:59
Speaker 1: from a poton. If you think about all the photons
24:02
Speaker 1: coming off the Sun, for example, then there's a big
24:05
Speaker 1: mix of frequencies. There's green, there's red, there's blue, there's
24:08
Speaker 1: all those together and together they make white. So the
24:10
Speaker 1: image you see of the sun if you look at
24:12
Speaker 1: the sun, please don't if you take a picture of
24:15
Speaker 1: the sun, is you see all those photons coming together
24:18
Speaker 1: into your telescope or your camera or your eye, and
24:21
Speaker 1: it's making that image. It's a summed up all those
24:25
Speaker 1: little bits of photons together make that image. It's really
24:28
Speaker 1: similar to the way you look at a screen. A
24:31
Speaker 1: screen is a bunch of pixels. It's an image broken
24:34
Speaker 1: down into little pieces, and the same thing happens in
24:37
Speaker 1: nature even without a screen, even without a device, right,
24:39
Speaker 1: just your eye essentially just gathers all those photons and
24:42
Speaker 1: builds an image in your mind. So the second part
24:45
Speaker 1: of the question was how does the photon carry within
24:48
Speaker 1: itself a pixel so that we're able to see the
24:50
Speaker 1: images we see on our telescopes. We'll remember the photons
24:53
Speaker 1: that don't carry the pixels. Pixels themselves are a way
24:56
Speaker 1: to see photons are way to detect photons. So if
25:00
Speaker 1: you think about what happens inside a telescope these days,
25:03
Speaker 1: telescopes are all digital, meaning you have a bunch of
25:05
Speaker 1: lenses to gather the light and focus the light, but
25:08
Speaker 1: the light in the end is focused onto a digital device,
25:11
Speaker 1: a digital camera basically that gathers and measures the amount
25:14
Speaker 1: of light. And the way those work is essentially to
25:17
Speaker 1: have a bunch of little buckets, and if a photon
25:19
Speaker 1: lands in that bucket, then it gets counted, and then
25:22
Speaker 1: you just count the number of photons you see and
25:24
Speaker 1: the picture is formed by having the places where more
25:27
Speaker 1: photons landed be more intense and the places where fewer
25:31
Speaker 1: photons landed be less intense. So you divide up the
25:34
Speaker 1: whole space into these buckets, and in each one you
25:36
Speaker 1: count how many photons you saw, and that forms your image.
25:40
Speaker 1: So that's how you might form like a black and
25:42
Speaker 1: white image if you're just counting the number of photons
25:45
Speaker 1: and you don't care what the energy was for any
25:47
Speaker 1: individual photon. That's how black and white camera works. We,
25:51
Speaker 1: of course, are very interested in color photography or color
25:54
Speaker 1: images of things that come from space. We want to
25:56
Speaker 1: know not just what's there, but how bright is it
25:59
Speaker 1: in red, or in green or in blue. So the
26:01
Speaker 1: way that works is instead of just having a bunch
26:04
Speaker 1: of individual buckets that capture photons regardless of their energy,
26:08
Speaker 1: we have different kinds of buckets, just like in your eye,
26:11
Speaker 1: how you have different kinds of things in the back
26:13
Speaker 1: of your eye, the rods and the cones, some of
26:16
Speaker 1: which can capture light and some of which can capture
26:18
Speaker 1: light of only specific wavelengths. In the same way, a
26:21
Speaker 1: digital camera has different kinds of buckets buckets with filters
26:25
Speaker 1: over them, so they capture lighted different wavelengths, different frequencies,
26:28
Speaker 1: different energies. All those things are equivalent, and so you'll
26:31
Speaker 1: have like a red bucket that only captures reddish photons,
26:35
Speaker 1: or a blue bucket that captures things around the blue
26:38
Speaker 1: part of the spectrum, and a green one that captures
26:40
Speaker 1: things around the green part of the spectrum. In an
26:43
Speaker 1: ideal world, for every pixel in your image, you would
26:47
Speaker 1: have a red, a green, and a blue bucket, so
26:50
Speaker 1: that you could figure out afterwards exactly what the color
26:53
Speaker 1: was by combining them back from red, green and blue
26:55
Speaker 1: and figuring out exactly what the mixture was and telling
26:58
Speaker 1: you what color it is. But you can't really have
27:01
Speaker 1: these buckets on top of each other, so practically what
27:03
Speaker 1: happens in most digital cameras is that for one pixel,
27:07
Speaker 1: you'll only have one kind of bucket. So for a
27:09
Speaker 1: certain pixel you might have a blue bucket, the next
27:12
Speaker 1: pixel will be only a red bucket, and the next
27:14
Speaker 1: one will be only a green bucket. And then later
27:17
Speaker 1: when you want to understand how much green light is
27:20
Speaker 1: there in a place where there was only a red pixel,
27:23
Speaker 1: you don't know because you didn't measure it because you
27:25
Speaker 1: didn't have a green bucket there. So what they do
27:27
Speaker 1: is they interpolate. They say how much green was there
27:30
Speaker 1: over there on the right, and how much green was
27:32
Speaker 1: there over there on the left, and it figures it out,
27:34
Speaker 1: it guesses how much green there might have been. So
27:37
Speaker 1: color photography is much more complicated, and even color photography
27:41
Speaker 1: using digital cameras attached to telescopes is much more complicated
27:45
Speaker 1: than you might imagine. So that's the way that photons
27:48
Speaker 1: carry information that creates the pixels we see in our images. Right,
27:52
Speaker 1: they don't carry the pixel. They don't show up and say, Hi,
27:55
Speaker 1: you should make this pixel a certain amount. The pixels
27:57
Speaker 1: instead add up, they integrate over all the photons that
28:01
Speaker 1: they detect. Alright, wonderful question. And my favorite part is
28:05
Speaker 1: this last bit that how do photons not disintegrate after
28:08
Speaker 1: traveling so far? Right? Because the photons have gone really
28:11
Speaker 1: far away. They might have left their star a bismillion
28:14
Speaker 1: miles away and flown through space for oodles of years
28:17
Speaker 1: before finally landing on your telescope or on your eyeball
28:21
Speaker 1: or on that rock. Right, think about how many amazing
28:24
Speaker 1: things have happened in the universe and the light from
28:26
Speaker 1: them has just been ignored. It's just like you know,
28:29
Speaker 1: hit a dog, or hit a street light, or just
28:32
Speaker 1: you know, hit the earth when it was daytime so
28:34
Speaker 1: we couldn't even see it. Anyway. The question is how
28:37
Speaker 1: does it not disintegrate? How does it last for so long? Well,
28:40
Speaker 1: a photon can go forever. It has the energy it needs,
28:43
Speaker 1: and it can fly through space. If it doesn't hit something,
28:47
Speaker 1: if it doesn't bounce into an electron or hit some atmosphere,
28:50
Speaker 1: it could literally fly forever. A photon is self sustaining.
28:53
Speaker 1: It's it's this amazing combination of electric fields and magnetic
28:57
Speaker 1: fields that slash back and forth to be completely self sustaining.
29:01
Speaker 1: So in an empty universe, if you shot a photon,
29:04
Speaker 1: it would fly forever, nothing, nothing, but there's nothing there
29:09
Speaker 1: to stop it, in the same way that if you
29:10
Speaker 1: pushed a ball through space through empty space, it would
29:14
Speaker 1: fly forever. So photons don't get tired. They're happy to
29:17
Speaker 1: fly through the whole universe to bring to you pictures
29:20
Speaker 1: from amazing and crazy things that are happening super far away.
29:23
Speaker 1: And we're glad that they are. We're glad that they
29:26
Speaker 1: get here, that they deliver this information into our eyeballs
29:29
Speaker 1: because we get to see this, this beautiful spectacle that
29:33
Speaker 1: is the universe. All right, So that was a wonderful
29:35
Speaker 1: listener Questions episode. Thank you very much to everybody who
29:38
Speaker 1: wrote in and sent us their questions. And to those
29:41
Speaker 1: of you who have sent us your recording of your
29:43
Speaker 1: questions but not heard yourself yet on the air, be patient.
29:46
Speaker 1: We will get to you. Thanks everybody for tuning in.
29:48
Speaker 1: I hope you enjoyed hearing about traveling at the speed
29:51
Speaker 1: of sound and hairy black holes and photons limping their
29:55
Speaker 1: way through the universe after billions of miles of journeys,
29:58
Speaker 1: and I hope that your journeys take you to place
30:00
Speaker 1: where you can appreciate this incredible, beautiful, but perplexing universe
30:04
Speaker 1: that we find ourselves in. Send your questions to Questions
30:08
Speaker 1: at Daniel and Jorge dot com. Thanks for tuning in.
30:19
Speaker 1: If you still have a question after listening to all
30:22
Speaker 1: these explanations, please drop us a line. We'd love to
30:25
Speaker 1: hear from you. You can find us at Facebook, Twitter,
30:27
Speaker 1: and Instagram at Daniel and Jorge That's one word, or
30:31
Speaker 1: email us at Feedback at Daniel and Jorge dot com.
30:35
Speaker 1: Thanks for listening, and remember that Daniel and Jorge Explain
30:38
Speaker 1: the Universe is a production of I Heart Radio. For
30:41
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30:44
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Speaker 1: favorite shows,