Latest / Daniel and Kelly’s Extraordinary Universe / Listener Questions 36

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Listener Questions 36 · Daniel and Kelly’s Extraordinary Universe

0:08
Speaker 1: Hey, or hey, do you ever wish you had more
0:11
Speaker 1: than two arms? That would be weird, but sometimes it
0:14
Speaker 1: would be useful. You know, if you're a parent, you're
0:16
Speaker 1: carrying around a couple of kids, would be great to
0:19
Speaker 1: have extra arms. Well, is it more arms do you
0:22
Speaker 1: want or more hands? I think what I want is
0:24
Speaker 1: maybe more brains. That would be handy. Then I can
0:27
Speaker 1: have twice a number of thoughts, or one of them
0:30
Speaker 1: could think while the other one naps, and then they
0:32
Speaker 1: can take turns. I think I already have more ideas
0:34
Speaker 1: than my arms and hands can handle. It. Sounds like
0:37
Speaker 1: you need less brains then, or more arms, like a
0:39
Speaker 1: whole army of arms. That would be pretty handy. It
0:42
Speaker 1: would be quite a handful. I am hand with cartoonists
1:00
Speaker 1: and the creator of PhD comics. Hi, I'm Daniel. I'm
1:03
Speaker 1: a particle physicist and a professor at UC Irvine, and
1:06
Speaker 1: I'm pretty sure I could make use of a third
1:09
Speaker 1: arm if it had a hand attached to it. Where
1:11
Speaker 1: would you put it? Though? In your body? Like at
1:14
Speaker 1: the top of your head, that would be useful. I
1:16
Speaker 1: was just gonna say it top of my head, yeah, exactly.
1:19
Speaker 1: You could like scratch your nose or scratch your back.
1:21
Speaker 1: Even that would be pretty handy. Yeah, but how would
1:24
Speaker 1: you scratch your arm? I'd have two other arms for
1:27
Speaker 1: that job, but would they reach I think the more
1:30
Speaker 1: interesting question is how you would call them, Like is
1:32
Speaker 1: it your right arm, your left arm, and your top arm,
1:35
Speaker 1: or you're like your dominant arm, your subdominant arm, and
1:38
Speaker 1: your sub subdominant arm. Maybe you could call it like
1:42
Speaker 1: your color arm or your weak heart. What if it's
1:47
Speaker 1: extra strong though, on the top of my head anyway,
1:49
Speaker 1: lots of fun things to think about, Yeah, because it
1:52
Speaker 1: is a fun universe with a lot to think about.
1:54
Speaker 1: There are a lot of stars and galaxies and amazing
1:57
Speaker 1: objects and invisible matter and will energy out there for
2:01
Speaker 1: us to wonder about and to have questions about. No
2:04
Speaker 1: matter which arm you'd like to use to scratch your head.
2:06
Speaker 1: Welcome to our podcast Daniel and Jorge Explain the Universe,
2:09
Speaker 1: a production of iHeartRadio in which we dig into all
2:12
Speaker 1: of the heads scratching mysteries about the universe, Why it
2:16
Speaker 1: looks the way it does, what color it is, if
2:18
Speaker 1: we can even possibly understand it, Why everything out there
2:22
Speaker 1: seems to be spinning, and why they spin in such beautiful,
2:25
Speaker 1: worly patterns. We dig into all of the mysteries of
2:28
Speaker 1: the universe, from the tiny quantum particle to the inside
2:32
Speaker 1: of black holes, to the edge of the universe, to
2:34
Speaker 1: its very beginning and its very end, because we love
2:37
Speaker 1: these mysteries, and we love marinating in our understanding and
2:41
Speaker 1: our ignorance. Yeah, because there are beautiful patterns out there
2:44
Speaker 1: in the universe. Patterns in color, patterns, in shape patterns,
2:48
Speaker 1: also in mysteries. It seems like the universe has sort
2:51
Speaker 1: of a recurring pattern of always having things that are
2:55
Speaker 1: difficult to explain or that don't reveal how they work
2:57
Speaker 1: right away. It is interesting that the universe is mysterious,
3:01
Speaker 1: but not so mysterious that we can't make progress. It's
3:04
Speaker 1: like we are just smart enough to understand like the
3:08
Speaker 1: next chunk of physics, but not so smart that we
3:10
Speaker 1: figure it all out right away, but also not so
3:13
Speaker 1: dumb that it's totally a mystery to us. We seem
3:16
Speaker 1: to be sort of like fine tuned to be entertained
3:19
Speaker 1: by the mysteries of this universe. You're saying, we're like
3:21
Speaker 1: the goldilocks of all species in the universe, But how
3:26
Speaker 1: do you know this, Daniel, how do you know we're
3:27
Speaker 1: not behind? How do you know we're not actually like
3:30
Speaker 1: at the back of the class roster. Yeah, we could be.
3:33
Speaker 1: There might be aliens out there that I figured out
3:35
Speaker 1: the physics of the universe and about ten seconds. But
3:38
Speaker 1: what I'm saying is that maybe this is more fun.
3:40
Speaker 1: Maybe it's more fun to be a little confused for
3:43
Speaker 1: a while and then figure something out, rather than just
3:46
Speaker 1: have the entire theory of everything come to you in
3:48
Speaker 1: a single flash of insight. That sounds like something a
3:51
Speaker 1: student who's not doing well in school might say, like, Hey,
3:54
Speaker 1: I got an F because it's it's fun. It's more
3:57
Speaker 1: like somebody who wants to keep the mysteries on because
4:00
Speaker 1: it's part of my job. I mean, if we like
4:03
Speaker 1: solved physics tomorrow, then what would I do the rest
4:06
Speaker 1: of my life? Is that what you tell the funding
4:08
Speaker 1: Agency's like, Hey, you paid me all this money and
4:10
Speaker 1: I haven't figured anything out, but I'm having a lot
4:13
Speaker 1: of fun. And really what's more important than that. It's
4:16
Speaker 1: the friends you make along the way to figuring out
4:19
Speaker 1: the universe. That's right, I got an F on my
4:21
Speaker 1: research paper, but F stands for friends and fun. Not funding.
4:26
Speaker 1: And it's not just people like me who are wondering
4:28
Speaker 1: about the nature of the universe and enjoying thinking about it.
4:31
Speaker 1: It's everybody sciences of the people, by the people, and
4:35
Speaker 1: for the people, and that includes me and you. It
4:38
Speaker 1: includes anybody who thinks about the universe, wonders why it
4:41
Speaker 1: works the way that does, and tries to figure it out.
4:44
Speaker 1: That's right. Everybody has questions, and sometimes we even answer
4:48
Speaker 1: those questions on this podcast, although sometimes the answer is
4:51
Speaker 1: we don't know. All too often the answer is we
4:53
Speaker 1: don't know, so give us some money to figure it out.
4:56
Speaker 1: Stay tuned. But we encourage everybody out there to engage
5:00
Speaker 1: with their curiosity, to look out the universe and connect
5:03
Speaker 1: with their personal questions. You know, something that I think
5:06
Speaker 1: maybe people don't appreciate is how science is driven by
5:10
Speaker 1: individual people's curiosity. The reason we study this and not that,
5:15
Speaker 1: the reason people investigate the mating patterns of South American bats,
5:19
Speaker 1: is because somebody has decided that that's the most important question,
5:23
Speaker 1: the one to dedicate their life too. So I like
5:25
Speaker 1: to encourage people to think about what is your most
5:28
Speaker 1: important question? If you could ask a single question of
5:30
Speaker 1: the universe and get an answer what would it be?
5:33
Speaker 1: And so we encourage our listener to think about the
5:36
Speaker 1: universe and to write to us with their questions. Yeah,
5:39
Speaker 1: we get questions all the time, and sometimes we even
5:41
Speaker 1: answer them on the podcast. We will pull up a
5:44
Speaker 1: question that we get and we'll try to give you
5:46
Speaker 1: our best answer on the air. Answer Right. We answer
5:49
Speaker 1: all of our questions that listeners send us to questions
5:52
Speaker 1: at Daniel and Jorge dot com. But sometimes there's one
5:55
Speaker 1: that I think is especially intriguing or requires a little
5:58
Speaker 1: bit of background research, so we answer it here on
6:01
Speaker 1: the podcast. And so today on the program, we'll be
6:03
Speaker 1: tackling listening our questions episode number thirty six of our
6:13
Speaker 1: listener question series That's Right, which puts us well above
6:17
Speaker 1: a hundred in terms of questions answered on air. And
6:20
Speaker 1: do we have a theme for this set of questions?
6:23
Speaker 1: This one's sort of like big questions about the big Universe.
6:27
Speaker 1: I see the usual then everything exactly. Today we have
6:34
Speaker 1: questions about questions exactly. Let's fall into the big questions category.
6:40
Speaker 1: All right, big questions here today we have three awesome
6:42
Speaker 1: questions about the shape of our galaxy, about the color
6:46
Speaker 1: of the universe, and also about whether the universe is
6:49
Speaker 1: maybe tearing itself apart. You mean emotionally or like physically.
6:54
Speaker 1: I think first physically and then emotionally. If you tear
6:56
Speaker 1: yourself apart physically, then if you want to really be
6:58
Speaker 1: able to tear yourself a part emotionally, Yeah, that's true.
7:01
Speaker 1: Depending on how the universe collapses, you might not have
7:04
Speaker 1: time for an emotional response. Well, let's dig into these
7:07
Speaker 1: questions because they're pretty interesting. The first one comes from
7:10
Speaker 1: Matt from Indiana. Hey, Daniel and Horey. This is Matt
7:13
Speaker 1: from Indiana. I was just reading an article which has
7:15
Speaker 1: some of the most recent Hubble pictures now that it's
7:17
Speaker 1: successfully returned to prime time. The question I have is
7:20
Speaker 1: about the galaxy aarp m adri zero zero zero two
7:24
Speaker 1: D five H three. NASA is saying it's noteworthy as
7:27
Speaker 1: it only has three arms to it and most spiral
7:29
Speaker 1: galaxies have even numbers. Why wouldn't we find an equal
7:32
Speaker 1: amount of even an odd armed disc galaxies symmetry. I'm
7:35
Speaker 1: perplexed on this. Thanks for your time, cheers, Matt. All right.
7:38
Speaker 1: Awesome question from Matt. He's asking not about the milk Away,
7:41
Speaker 1: but a different galaxy that the Hubble Telescope has found. Yeah,
7:44
Speaker 1: we have imaged so many galaxies. You know, when you
7:47
Speaker 1: look up in the night sky, you mostly see stars,
7:49
Speaker 1: but behind those are tiny little smudges which are galaxies.
7:53
Speaker 1: And as we saw from the recent James Webb Space
7:56
Speaker 1: Telescope images, every tiny little dot of sky is filled
8:00
Speaker 1: with galaxies, and they have lots of really interesting shapes
8:02
Speaker 1: and characteristics. And so now we have lots and lots
8:05
Speaker 1: of examples of what other galaxies look like. And Matt
8:08
Speaker 1: is asking about one particular one that NASA said was
8:11
Speaker 1: a little weird. Yeah, and he spelled out the name
8:13
Speaker 1: of it. Maybe we should spill it out again in
8:15
Speaker 1: case anyone wants to look it up. Yeah, that's galaxy
8:17
Speaker 1: AARP DASH M A D O R E. Then the
8:22
Speaker 1: number is two one one five dash two seven three
8:26
Speaker 1: And we'll put a link to NASA's page about this
8:28
Speaker 1: in the show notes. They just got a catchy name,
8:30
Speaker 1: my daughter. It sounds like I love you or something. Well,
8:32
Speaker 1: if you look up the image and the link on
8:34
Speaker 1: our website, you'll see basically a picture of our galaxy.
8:37
Speaker 1: But it looks kind of interesting because it's got two
8:40
Speaker 1: short arms, but then a one long arm on the bottom. Yeah,
8:43
Speaker 1: lots of these spiral galaxies have the same basic features
8:46
Speaker 1: you have, like a central bar and then some arms
8:48
Speaker 1: swirling around them. And this one is a little weird because,
8:52
Speaker 1: as you say, it has two sort of shorter arms
8:53
Speaker 1: and one longer arm. And that's the thing that Matt
8:56
Speaker 1: picked up on that the fact that this has three arms,
9:00
Speaker 1: according to this press release, having an odd number of arms,
9:02
Speaker 1: like not two or four or six is a little weird.
9:05
Speaker 1: You mean, it's a little odd you have an odd
9:07
Speaker 1: number of arms, because I think we're kind of used
9:10
Speaker 1: to arms coming in pairs, right, I certainly have two arms,
9:14
Speaker 1: though i'd like a third. But if we're talking about galaxies,
9:17
Speaker 1: then it sort of makes conceptual sense to imagine them
9:20
Speaker 1: being even numbers, like or basically there's just two arms
9:23
Speaker 1: because you have the central bar and then the arms
9:25
Speaker 1: swirling off around it. But it turns out that galaxy
9:28
Speaker 1: arms are a lot more complicated than you might imagine.
9:30
Speaker 1: M Well, let's dig into it. First of all, why
9:33
Speaker 1: do galaxies even have arms? And I guess maybe we
9:36
Speaker 1: should define what we mean by arms. It's kind of
9:38
Speaker 1: like a you look at a picture of a galaxy
9:40
Speaker 1: you see a cluster of stars, but then you see
9:42
Speaker 1: these kind of like tendrils, these rows of stars kind
9:46
Speaker 1: of swirling from the center of it. That's what an
9:48
Speaker 1: arm is. Yeah, and so we tend to call these
9:50
Speaker 1: things spiral arms. And there's really two things going on there,
9:54
Speaker 1: the spiral nature of them and the arms. Right, So
9:57
Speaker 1: let's first talk about like why are these things spiraling
10:01
Speaker 1: at all? Why is there a spiral pattern in the galaxy.
10:04
Speaker 1: And that just comes from the fact that the galaxy
10:06
Speaker 1: is spinning. So everything in space is spinning, and as
10:09
Speaker 1: it collapses, it spins faster and faster. The things a
10:11
Speaker 1: different distance from the center of the galaxy don't always
10:14
Speaker 1: rotate at the same like number of angles per second. Instead,
10:18
Speaker 1: they tend to move through space at the same linear speed.
10:22
Speaker 1: So galaxies don't rotate like a DVD or a compact disc,
10:27
Speaker 1: where like every point along some line rotates with the
10:29
Speaker 1: same angular speed. It's more like they rotate like runners
10:33
Speaker 1: going around a track, where people on the outside tend
10:36
Speaker 1: to fall behind even if they're running at the same speed. Well,
10:40
Speaker 1: maybe let's take it a step back. Because you mentioned
10:43
Speaker 1: everything is always spinning. What does that mean? Wh are
10:46
Speaker 1: things in space necessarily spinning or do you mean, like
10:48
Speaker 1: everything's moving but relative to like the center of gravity
10:52
Speaker 1: or the center of a cluster of stuff, you're sort
10:56
Speaker 1: of spinning around that. So everything in space is sort
10:58
Speaker 1: of whizzing around. And remember that spinning is relative to
11:03
Speaker 1: an axis. You like, draw a line through space and say,
11:06
Speaker 1: are things moving around this point? And so you can
11:09
Speaker 1: pick any axis you like. You know, pick like the
11:12
Speaker 1: center of the sun. That makes sense to think about
11:14
Speaker 1: the motion of the Solar system, or you know, the
11:16
Speaker 1: north south axis of the Earth. But you really could
11:18
Speaker 1: pick anything, but it makes most sense to pick like
11:20
Speaker 1: the center of mass of a big blob of stuff
11:23
Speaker 1: and ask are things moving around this center of mass?
11:26
Speaker 1: And because everything is sort of flying around through space,
11:29
Speaker 1: it's not stationary with respect to like the center, then
11:32
Speaker 1: all that stuff tends to add up to some spinning.
11:35
Speaker 1: Like it's possible for a huge blob of stuff to
11:37
Speaker 1: not be spinning, but that would require everything inside of
11:41
Speaker 1: it to like exactly balance all of its motion. It's
11:44
Speaker 1: sort of unlikely, like flipping a million coins and having
11:47
Speaker 1: exactly fifty percent of them land up heads. So any
11:51
Speaker 1: big blob of stuff tends to have some spin around
11:54
Speaker 1: its center. Yeah, so I guess you know, things tend
11:57
Speaker 1: to fly in a straight line in space. But once
11:59
Speaker 1: you get a bunch of sort of in the same area,
12:01
Speaker 1: it's going to have some gravity and it's going to
12:03
Speaker 1: start pulling stuff inwards towards the center of massive that blob,
12:07
Speaker 1: and that's where the kind of the spinning happens, right,
12:10
Speaker 1: That's where the circular emotion happens. And so that's why
12:12
Speaker 1: everything's kind of spinning around a galaxy cluster m exactly.
12:16
Speaker 1: And as that's been happens, it very naturally forms a
12:19
Speaker 1: spiral pattern, right, because things that the outside get left behind.
12:22
Speaker 1: They're not spinning as fast as things closer in. Like
12:26
Speaker 1: if you're really close to the center, it doesn't take
12:28
Speaker 1: you as long to go all the way around the galaxy.
12:30
Speaker 1: For example, if you're really far out and you're moving
12:33
Speaker 1: at the same speed, takes you a lot longer to
12:35
Speaker 1: go all the way around the galaxy. So things and
12:38
Speaker 1: the outside tend to get left behind, and that's why
12:40
Speaker 1: you end up with spiral patterns in the galaxy. But
12:43
Speaker 1: that doesn't explain why you get arms, right, if you
12:46
Speaker 1: just have like a big blob of stuff and it
12:48
Speaker 1: was spinning and collapsing, it would tend to sort of
12:50
Speaker 1: like wind itself up. You wouldn't necessarily get blobs like arms.
12:55
Speaker 1: So the spinning explains the spiral nature, but not the arms. Right,
12:58
Speaker 1: Like if you had a big blob of out there
13:00
Speaker 1: in space and that was evenly distributed, like a hazy cloud,
13:03
Speaker 1: and then you just got it going, you would think
13:06
Speaker 1: it would just kind of like swirl towards the center,
13:08
Speaker 1: kind of like a toilet, right, there'd be no clustering.
13:11
Speaker 1: It's just like a like a tornado, like an even
13:13
Speaker 1: swirl down to the center. Yeah, Like if you put
13:15
Speaker 1: a fork in spaghetti and spin it, you're gonna end
13:18
Speaker 1: up with lots and lots and lots of strands, not
13:20
Speaker 1: like a few big clumps. But what we see in
13:22
Speaker 1: galaxies is it we've got like really big chunks. We
13:25
Speaker 1: got like two or four or three in this case,
13:28
Speaker 1: chunks of stuff flying out in this spiral pattern, or
13:31
Speaker 1: more like the three giant or three or four giant
13:34
Speaker 1: spaghetti noodles, right, instead of like a bunch of little
13:37
Speaker 1: spaghetti noodles. Somehow, the spaghetti's kind of clustering to giant
13:42
Speaker 1: strands of spaghetti. Yeah, exactly like metapasta or something megapasta formations.
13:48
Speaker 1: And so a lot of people think that when you're
13:50
Speaker 1: looking at a galaxy and you're looking at these spiral arms,
13:53
Speaker 1: that you're looking at structures of matter, that like, the
13:56
Speaker 1: arms are a blob of stars like a blob of spaghetti,
13:59
Speaker 1: and that whole arm is sort of rotating, that the
14:02
Speaker 1: stars are moving with the arm. But that's actually not
14:05
Speaker 1: the case. The arms are not structures of matter. They're
14:10
Speaker 1: just density waves. They're more like traffic patterns in cars,
14:14
Speaker 1: you know, like a traffic wave can move along the highway,
14:18
Speaker 1: making some cars slow down and some cars speed up
14:20
Speaker 1: or clump together, But the cars don't necessarily move with
14:23
Speaker 1: those waves in the same way the arms in the
14:26
Speaker 1: galaxy are rotating. But stars don't necessarily rotate with the arms.
14:31
Speaker 1: They can be left behind by the arm, the arm
14:32
Speaker 1: can catch up with them. The stars don't move with
14:36
Speaker 1: the arms. Well, first of all, what do you mean,
14:38
Speaker 1: because there aren't the arms made of stars? Like, if
14:40
Speaker 1: we can see them in the night sky in space,
14:42
Speaker 1: that means it's bright, and so that means we're seeing
14:45
Speaker 1: the stars in them. Yeah, they are made of stars.
14:47
Speaker 1: For sure, the same with the like traffic patterns are
14:49
Speaker 1: made of cars. But the things that make the arm
14:52
Speaker 1: the arm is that there's a denser spot of stars.
14:55
Speaker 1: There's more stars there than somewhere else. But as the
14:59
Speaker 1: arm moves, sort of moves through the stars the same
15:03
Speaker 1: way that like waves move through water, but the individual
15:06
Speaker 1: particles of water don't necessarily move with the wave. Right,
15:10
Speaker 1: the wave is motion of the water. Oh, I see
15:12
Speaker 1: what you're saying. You're saying, like if I looked at
15:14
Speaker 1: a sped up or fast forwarded movie of a galaxy,
15:18
Speaker 1: I would see it looking like it's a squirrel, like
15:20
Speaker 1: it's spinning, But it's not actually spinning, you're saying. It
15:23
Speaker 1: just has these waves running through it that go around.
15:26
Speaker 1: The waves are spinning, But if you tracked a wave
15:29
Speaker 1: and you also tracked an individual star, you would not
15:31
Speaker 1: necessarily see them move together, like a star can be
15:35
Speaker 1: part of an arm and then later not part of
15:37
Speaker 1: an arm, and then part of another arm. Whoa, and
15:41
Speaker 1: so how do we know this because we haven't been
15:43
Speaker 1: looking long enough for us to see that. Yeah, it's
15:45
Speaker 1: a really interesting idea. It's only been around for a
15:48
Speaker 1: few decades, and it's not one hundred percent certain, though
15:51
Speaker 1: in the last few years we've got some evidence that
15:53
Speaker 1: this is true because we've looked at the color of
15:56
Speaker 1: light in these stars. Because the galactic arms tend to
15:59
Speaker 1: be aligned with star formation, these galactic arms are places
16:03
Speaker 1: of greater density, which means you get more stars being
16:06
Speaker 1: made because you're compressing the gas. So you tend to
16:08
Speaker 1: have younger stars in the arms as they are forming,
16:12
Speaker 1: and younger stars tend to be bluer because bluer stars
16:15
Speaker 1: don't live as long. So anyway, the long story short,
16:17
Speaker 1: you can look at the pattern of color in these
16:20
Speaker 1: arms and you can see how sort of how old
16:22
Speaker 1: they are and the age of stars within the arms,
16:25
Speaker 1: and so you can sort of confirm this hypothesis, though
16:28
Speaker 1: I should say it's not a one hundred percent totally established.
16:31
Speaker 1: So you're saying the arms of a galaxy are actually
16:34
Speaker 1: kind of like waves that are going through the huge
16:38
Speaker 1: cloud of stars in the galaxy. But what's causing these waves?
16:42
Speaker 1: So these are density waves, So they're just caused by
16:45
Speaker 1: things not being totally smooth, the same way like all
16:48
Speaker 1: gravitational effects are. If you have a little perburbation, things
16:52
Speaker 1: aren't totally smooth. Then gravity tends to pull on that
16:54
Speaker 1: and exaggerated, so gravity will take a little perburbation in
16:58
Speaker 1: like a totally smooth clump and turn it into larger
17:01
Speaker 1: and larger perturbations. So it's not again totally understood where
17:05
Speaker 1: these come from and why they last so long. But
17:08
Speaker 1: they think they come from original density perturbations and like
17:11
Speaker 1: the central clump of the galaxy. So they are structures.
17:15
Speaker 1: Then you said earlier that they weren't structures. So it
17:18
Speaker 1: is there because the stuff in it is kind of
17:20
Speaker 1: holding together gravitationally. Yeah, but it's a density structure. It's
17:23
Speaker 1: not like a matter structure. It's not like the same
17:26
Speaker 1: stars are sweeping around and staying in the arm. There
17:29
Speaker 1: is a structure there at the density structure, right, and
17:32
Speaker 1: that you're saying the density is caused by the gravity
17:35
Speaker 1: between them. So let's see, I'm a planet or I'm
17:39
Speaker 1: a star around a galaxy. What's going to make me
17:42
Speaker 1: want to join one of these waves. Well, it's sort
17:44
Speaker 1: of sweeping through the galaxy and it creates regions with
17:47
Speaker 1: higher gravity and regions with lesser gravity, and so some
17:49
Speaker 1: stars are like getting pulled towards these things, and some
17:52
Speaker 1: stars are getting left behind right, And so that's how
17:56
Speaker 1: a density wave propagates. Right, it creates regions of great
18:00
Speaker 1: and lesser force, which tends to apply differential forces on
18:04
Speaker 1: the stars. Right. But unlike a wave and water, you
18:07
Speaker 1: have forces that pull and push, right, like something behind
18:12
Speaker 1: you pushes you forward, but then some in front of
18:14
Speaker 1: you pushes you back, and that's kind of how the
18:16
Speaker 1: wave occurs. But in gravity, gravity only attracts. So what
18:20
Speaker 1: moves the wave forward? Well, what's moving the wave forward,
18:22
Speaker 1: Like at the forefront of the wave, it's density, So
18:25
Speaker 1: it's pulling those stars towards it. Right, So the density
18:29
Speaker 1: of the arm creates a denser region in front of it.
18:32
Speaker 1: Oh I see, So the wave in front of it
18:34
Speaker 1: eats up more stars, which moves the center of gravity
18:38
Speaker 1: of the arm forward, which then leaves behind the stars
18:42
Speaker 1: behind it exactly. And so that's how a density wave propagates.
18:46
Speaker 1: And what's really interesting to me is that you know,
18:48
Speaker 1: the velocity of the arms is not the same as
18:51
Speaker 1: the velocity of the stars. That means where your star
18:54
Speaker 1: is in the galaxy determines whether these density waves are
18:57
Speaker 1: passing you or whether you're passing them, like for example,
19:01
Speaker 1: our sun moves around the center of the galaxy at
19:03
Speaker 1: a certain speed, which is basically determined by where it
19:06
Speaker 1: is a distance from the center, And so it's actually
19:08
Speaker 1: moving around the galaxy about twice as fast as the arms.
19:12
Speaker 1: So we are catching up to arms and passing them by.
19:15
Speaker 1: But if we were further out, then the density waves
19:17
Speaker 1: would be passing us by, and so that's where arms
19:20
Speaker 1: come from. Now. Matt's question was, why is it weird
19:23
Speaker 1: that this one galaxy that we saw has three arms?
19:26
Speaker 1: Why is it weird to have an odd number of arms?
19:28
Speaker 1: So they make this comment on the page describing this galaxy.
19:31
Speaker 1: So I chatted with a couple of experts about galaxy formation,
19:35
Speaker 1: and they quibbled a little bit with this claim that
19:37
Speaker 1: it is unusual. First of all, they say, it's not
19:40
Speaker 1: even really easy to define, like how many arms a
19:43
Speaker 1: galaxy has, you know, because it's basically just visual inspection.
19:47
Speaker 1: You're just sort of like looking at it and seeing sorrels.
19:50
Speaker 1: But you know, galaxies have more complex structure than just
19:53
Speaker 1: like here's an arm. There's an arm. Like if you
19:55
Speaker 1: look at the Milky Way our galaxy, it has sort
19:58
Speaker 1: of two major arms, but lots of like little spurs
20:01
Speaker 1: off of it. For example, we live in the Orion spur,
20:05
Speaker 1: which is like a little offshoot from the major Sagittarius arm.
20:10
Speaker 1: So is that really another arm or not. It's not
20:13
Speaker 1: like a well defined way to count these arms. It's
20:15
Speaker 1: just sort of like by looking at it, M I
20:18
Speaker 1: see so's it's it's hard to define what makes an arm.
20:21
Speaker 1: It's hard to define what makes an arm exactly. And
20:25
Speaker 1: so you look at this particular galaxy and you're like, yeah,
20:28
Speaker 1: I could call that three or I could call that
20:30
Speaker 1: four maybe. And so the short answer is that I
20:33
Speaker 1: don't think there's broad agreement on how to define arms
20:37
Speaker 1: or how many arms it makes sense for galaxies to have. M.
20:41
Speaker 1: I guess my question would be, if you look at
20:43
Speaker 1: all the galaxies that we can see out they're in space,
20:47
Speaker 1: what is more common? Is it more common to have
20:49
Speaker 1: an even ish number of arms or an odd ish
20:53
Speaker 1: number of arms. Yeah, it's a great question, and it's
20:55
Speaker 1: a hard question to answer without like a systematic way
20:58
Speaker 1: to analyze these things. Basically, a human has to look
21:01
Speaker 1: at it and say, I think it has three, But
21:03
Speaker 1: another human might look at the same galaxy and say, no,
21:06
Speaker 1: I think this one has four. So to get like
21:08
Speaker 1: enough statistics to do some analysis of that, you need
21:12
Speaker 1: some like really rigorous way to analyze these things. And
21:15
Speaker 1: people have done like for any analysis or the distribution
21:18
Speaker 1: of density waves through galaxies, But that's really just a
21:21
Speaker 1: way of counting like the strength of these things. Again,
21:23
Speaker 1: you have the problem of deciding when to call it
21:26
Speaker 1: another arm. So right now is really just mostly anecdotal.
21:29
Speaker 1: People have seen a bunch of galaxies and they haven't
21:32
Speaker 1: seen ones that look like this to them, And there
21:34
Speaker 1: are ways to explain it. Like if you look at
21:36
Speaker 1: a galaxy like this and you say, how did this
21:37
Speaker 1: galaxy get this way? Well, one possible explanation is that
21:41
Speaker 1: it recently had a strong gravitational interaction with another galaxy
21:45
Speaker 1: that sort of messed it up. Because this one also
21:47
Speaker 1: seems sort of asymmetric, right It's got like one long
21:50
Speaker 1: arm on one side and two shorter arms on the
21:52
Speaker 1: other side. So it may just be that like a
21:55
Speaker 1: passing galaxy sort of pulled on it in a way
21:58
Speaker 1: it separated those density waves. M But I mean, I
22:01
Speaker 1: guess is it easy to pull up pictures of galaxies
22:05
Speaker 1: that look like they have three arms? Is it maybe
22:07
Speaker 1: harder or easier or the same as pulling up pictures
22:10
Speaker 1: that looked like they have four arms or two. I
22:13
Speaker 1: think it's probably true that most of the galaxies you
22:16
Speaker 1: look at, if you've just counted them, you would probably
22:18
Speaker 1: get an even number of arms. A lot of them
22:20
Speaker 1: just look like they have two, though they're sort of
22:22
Speaker 1: like tightly wrapped around. But look at the Milky Way,
22:25
Speaker 1: for example, it's not easy to say, like how many
22:27
Speaker 1: are there? Like I count one, two big ones and
22:30
Speaker 1: at least two maybe four little ones. Although we don't
22:33
Speaker 1: really have a picture of the Milky Way, do we.
22:35
Speaker 1: We certainly don't have an actual image of the Milky
22:38
Speaker 1: Way from the outside, though we can reconstruct the density
22:42
Speaker 1: of stars in the Milky Way using a lot of
22:44
Speaker 1: our observations. Right, well, could there be maybe some effects
22:48
Speaker 1: we are talking about waves right around sort of a
22:50
Speaker 1: fixed medium. Is it possible that, you know, given the
22:54
Speaker 1: typical size of a galaxy with the typical number of stars,
22:57
Speaker 1: maybe like a standing way of four arms is more
23:02
Speaker 1: likely than a standing wave of three arms, you know,
23:05
Speaker 1: like waves around the spiral of the galaxy. I read
23:08
Speaker 1: some papers about these things, and there's are some arguments
23:12
Speaker 1: for why you might get two or four if these
23:15
Speaker 1: things really do come from like density perturbations in the
23:18
Speaker 1: center of the galaxy, because you would expect that to
23:20
Speaker 1: be somewhat symmetric, right, that it would cause similar effects
23:24
Speaker 1: in one direction and in the other. And so it
23:26
Speaker 1: makes some sort of sense for this thing that collapse
23:28
Speaker 1: into a bar that then generates two arms, and that
23:31
Speaker 1: those might split, but that splitting would always give you
23:35
Speaker 1: an even number. So there are some papers suggesting that
23:38
Speaker 1: you would expect, on average to get an even number
23:41
Speaker 1: of arms, and I think that makes some sense, but
23:43
Speaker 1: it's not very well established. Well, so then the picture
23:47
Speaker 1: that Matt saw, he saw I did an article that
23:49
Speaker 1: said that NASA think is weird to have an odd
23:52
Speaker 1: number of arms? What was NASA saying there? So the
23:55
Speaker 1: quote the article says, while most disc galaxies have an
23:58
Speaker 1: even number of spiral arms, this one has three. But
24:01
Speaker 1: you know, the astronomers I talked too, quibbled with that
24:03
Speaker 1: a little bit. They didn't think it was so weird.
24:05
Speaker 1: They've seen galaxies with three arms before. M I guess
24:09
Speaker 1: we'll have to ask NASA. I mean, what do they know.
24:12
Speaker 1: Let's have them on the podcast. All right, Well, I
24:14
Speaker 1: think that answers Matt's question, which is like, maybe it's
24:17
Speaker 1: maybe it's not that weird, right, It seems like some
24:20
Speaker 1: astronomers don't think it's as weird to have three arms.
24:23
Speaker 1: It seems like it's kind of a fuzzy thing. Anyways,
24:25
Speaker 1: it is. But what is weird is that arms exist
24:28
Speaker 1: at all. It's really fascinating in the dynamics of galaxies.
24:31
Speaker 1: They have these things slashing and swirling around, and it
24:34
Speaker 1: just reminds you that galaxies are dynamical objects. They're not
24:38
Speaker 1: fixed things that have been formed millions of years ago
24:41
Speaker 1: and unchanged. Right, they are swirling, they're crashing into each other,
24:45
Speaker 1: they're constantly changing, just on these vast, vast time scales
24:49
Speaker 1: that we can hardly even imagine. Yeah, and they're not
24:52
Speaker 1: just dynamic, they're like wavy, right, They're rippling. That's what
24:55
Speaker 1: these arms are. They're ripples in their structure. All right, Well,
24:58
Speaker 1: let's get into some of our other questions. One is
25:00
Speaker 1: about the color of the universe and the other is
25:03
Speaker 1: about the fate of the universe. So let's get into those.
25:07
Speaker 1: But first let's take a quick break. All right. We're
25:21
Speaker 1: answering listener questions here about everything is usual, the whole
25:26
Speaker 1: she bang, the whole universe. And our second question comes
25:29
Speaker 1: from Genie, Hi, Daniel and Hagee. The question I would
25:33
Speaker 1: really like to ask is did the universe have a
25:35
Speaker 1: color after the Big Bang? If there was no color,
25:39
Speaker 1: when was there first a color? And what was it?
25:42
Speaker 1: Thank you have all the questions we've gotten, this is
25:45
Speaker 1: the one that really threw me for a loop, Like, Wow,
25:48
Speaker 1: a question I've never even thought of before, never heard
25:50
Speaker 1: of before. What a super fun question. Yeah, it's a
25:54
Speaker 1: very colorful question. Jennie asked, did the universe have a
25:57
Speaker 1: color after the Big Bang? So I guess a big
26:00
Speaker 1: bang happened, and I guess her maybe her question is like,
26:03
Speaker 1: if there was a human present there, what would it
26:06
Speaker 1: look like? Would it look red, purple, green, polka? Or
26:10
Speaker 1: would it just fry your eyes? Yeah? It really is
26:13
Speaker 1: one question what would you see if you were there? Right?
26:16
Speaker 1: Really love this question and I think it's really fun
26:18
Speaker 1: because it makes us think about like what is color? Anyway? Yeah,
26:21
Speaker 1: let's dig into that. What is color? How would you
26:24
Speaker 1: define it? I know it's related to the wavelength of
26:27
Speaker 1: the light. It is related to the wavelength of light,
26:30
Speaker 1: But I think it's important to distinguish, right, Like, photons
26:33
Speaker 1: have a wavelength, which means like how long it takes
26:36
Speaker 1: for them to go up and down. It's related to
26:38
Speaker 1: their frequency, right, how many times they wiggle per second.
26:41
Speaker 1: But the color is not a property of the photon,
26:44
Speaker 1: like photons themselves don't have color. Color is something inside
26:48
Speaker 1: your head. It's like how your brain responds to a
26:52
Speaker 1: signal of a photon of a specific color, So it's
26:56
Speaker 1: not part of the photon itself. It's like the taste
26:58
Speaker 1: of salt itself. Doesn't have a taste your tongue as
27:01
Speaker 1: a response to sensing salt. Right, I guess you're sort
27:05
Speaker 1: of quivaling about the definition of things. But I mean
27:07
Speaker 1: light does have different wavelengths, right, it does. But there
27:10
Speaker 1: are lots of wavelengths of light that we can't see
27:13
Speaker 1: and our brain doesn't respond to. So photons above the
27:16
Speaker 1: visible spectrum like have no color to them. Early, they
27:20
Speaker 1: have no color. So far, we could panically start naming
27:24
Speaker 1: other colors, right, Yeah, absolutely, you could even imagine creating
27:29
Speaker 1: a new internal response that's a different color than anybody
27:33
Speaker 1: has ever imagined before. Right, If colors are really just
27:36
Speaker 1: part of your mind, If there are a response to
27:39
Speaker 1: signals from your optic nerve that in principle there's no
27:42
Speaker 1: limitation on experiencing new colors, not just combinations of existing colors,
27:47
Speaker 1: but like brand new colors, and so in principle that's possible,
27:51
Speaker 1: and you could assign those to very high frequency light.
27:53
Speaker 1: You could imagine like building a technological eyeball that sends
27:57
Speaker 1: messages to your brain. Your brain would learn to interpret
28:00
Speaker 1: those responses by giving you some new experience that would
28:02
Speaker 1: be like a new color. Yeah. I think what you're
28:05
Speaker 1: talking about is that you know, light has a certain
28:06
Speaker 1: frequency that can come in certain frequencies, and let's say
28:09
Speaker 1: like seven gig gigga hurts or something, or like seven
28:13
Speaker 1: hurts might be a frequency. And when I see that
28:18
Speaker 1: frequency of light, I think the color green, for example,
28:22
Speaker 1: And you and I agree that if we see light
28:24
Speaker 1: at this frequency, if we're going to call it green.
28:26
Speaker 1: But I think what you're saying is like, maybe what
28:27
Speaker 1: I experienced this green is different with them what you
28:30
Speaker 1: experience is green. That's certainly true. And there's only also
28:33
Speaker 1: a narrow band of photon frequencies that we even have
28:36
Speaker 1: colors assigned to, and sort of the long history of
28:39
Speaker 1: the universe is that it started out really really hot
28:42
Speaker 1: and dense, and photons created in the very very beginning
28:45
Speaker 1: of the universe after the Big Bang had very very
28:48
Speaker 1: high energies, very high frequencies. Then the universe is cooling down,
28:51
Speaker 1: and so the photons created get longer and longer, right,
28:55
Speaker 1: lower frequencies, and so the universe sort of starts out
28:58
Speaker 1: invisible and then passes through the visible spectrum. And so
29:02
Speaker 1: like Genie's asking, what color was the universe when it started? Right,
29:05
Speaker 1: And the problem is that the energy of the photons
29:07
Speaker 1: at the very beginning of the universe don't really have
29:10
Speaker 1: a color. They're too high frequency for us to fc right,
29:13
Speaker 1: because the energy of a photon is related directly related
29:17
Speaker 1: to its frequency, right, Like the higher the energy, the
29:20
Speaker 1: higher the exactly, and hot stuff tends to make higher
29:24
Speaker 1: energy photons. We've talked about this on the podcast a
29:26
Speaker 1: few times. Everything generates photons. Everything that has charged particles
29:30
Speaker 1: inside of it generates photons, and it generates photons based
29:34
Speaker 1: on its temperature. So the Sun generates photons as some
29:37
Speaker 1: temperature because of its thousands of degrees kelvin, the Earth
29:40
Speaker 1: glows and generates photons at some temperature because it's much cooler,
29:44
Speaker 1: and you generates photons at some wavelength. Your eyes can't
29:47
Speaker 1: see the photons generated by yourself or by the Earth.
29:50
Speaker 1: They can see the ones from the sun. So some
29:53
Speaker 1: of these photons are visible and some of them are invisible.
29:55
Speaker 1: But the hot or something is the higher energy the
29:58
Speaker 1: photons it generates. Right. So are you're saying maybe at
30:01
Speaker 1: the Big Bang everything all the photons that were there
30:05
Speaker 1: were super high frequency or low wavelength. What are you
30:09
Speaker 1: saying that? Initially at the Big Bank things were so crazy.
30:12
Speaker 1: All the photons were super duper high energy. They were
30:15
Speaker 1: super high energy, which means very short wavelength, which means
30:19
Speaker 1: very high frequency, right, And so these photons were zipping
30:22
Speaker 1: around the universe. And if your eyeball was there just
30:25
Speaker 1: after this moment, when the universe was like at the
30:27
Speaker 1: Plank temperature, then not only would it be cooked instantly,
30:30
Speaker 1: but the photons that hit it it wouldn't know how
30:32
Speaker 1: to interpret. Your eye wouldn't see them, So the universe
30:35
Speaker 1: would just be black, even though it'd be super duper
30:37
Speaker 1: hot and filled with photons. Yeah, Like, if your eye
30:40
Speaker 1: could somehow survive being in a Big Bang, it wouldn't
30:42
Speaker 1: you would see total darkness, right, because all the light
30:45
Speaker 1: would be sort of like X rays, they just passed
30:47
Speaker 1: through your eyeball. One question is would they interact with
30:49
Speaker 1: your eyeball or they passed through like X rays, right.
30:52
Speaker 1: X rays do interact with some parts of your body,
30:54
Speaker 1: but not others. And as a frequency of photons change,
30:57
Speaker 1: there are chances of interacting with you changes. But you're right,
30:59
Speaker 1: a lot of these photons might just fly right through you,
31:02
Speaker 1: like X rays, which are higher energy photons than our
31:05
Speaker 1: eyeballs can see. But then the universe temperature changes. But
31:08
Speaker 1: then eventually, after the Big Bang, the universe started cooling down, right,
31:12
Speaker 1: and so you started seeing photons with a lower energy, yes, exactly.
31:16
Speaker 1: So as the universe cools and it's really dense, plasma
31:19
Speaker 1: gets more and more dilute, it cools down, and so
31:22
Speaker 1: it starts generating photons with longer wavelengths. So as time
31:26
Speaker 1: goes on, the temperature of the universe is dropping and
31:29
Speaker 1: the energy those photons is dropping, and so the wavelength
31:32
Speaker 1: is increasing. So they're like the general light of the
31:36
Speaker 1: universe started off way too high for our eyes, but
31:39
Speaker 1: then it gradually as it cools starts to approach the
31:42
Speaker 1: visible spectrum. Yeah, and there's a really fascinating moment around
31:46
Speaker 1: three hundred and eighty thousand years after the Big Bang
31:49
Speaker 1: when the universe cooled so much that atoms could now form.
31:54
Speaker 1: So you have protons and electrons whizzing around with so
31:56
Speaker 1: much energy that they couldn't be bothered to bond together.
31:59
Speaker 1: But after a certain time things cool down those electrons
32:02
Speaker 1: that it no longer had enough energy to escape the
32:05
Speaker 1: pull of those protons which have a positive charge and
32:08
Speaker 1: pull on the electrons, and so you get neutral hydrogen forms.
32:12
Speaker 1: And in this moment, the universe goes from being opaque
32:15
Speaker 1: like a really hot plasma like the center of the Sun,
32:18
Speaker 1: to being transparent, just like clouds of gas in space
32:21
Speaker 1: that light could mostly pass through. So all the light
32:24
Speaker 1: generated before this moment was just reabsorbed by the hot plasma.
32:28
Speaker 1: Light generated after this moment can fly through the universe,
32:32
Speaker 1: and like hit your eyeball, and this light is still
32:34
Speaker 1: flying through the universe. It's the cosmic microwave background light.
32:38
Speaker 1: We can see it with our telescopes. When it was
32:40
Speaker 1: generated at that moment in time, the universe was still
32:43
Speaker 1: filled with a pretty hot plasma. It was like several
32:46
Speaker 1: thousand degrees So that was the moment when the universe
32:48
Speaker 1: first became transparent and the light that were created sort
32:52
Speaker 1: of becomes persistent. Right, But still that light is too
32:56
Speaker 1: high energy for eyeballs to capture. Right, Like when I
32:59
Speaker 1: look up at the night sky, I can't see the
33:01
Speaker 1: cosmic microwave background with my eyes, can I You cannot
33:04
Speaker 1: see the cosmic microwave background with your eyes currently. But
33:07
Speaker 1: when it was created, it actually was in the visible
33:10
Speaker 1: spectrum because remember that the wavelength depends on the energy,
33:13
Speaker 1: on the temperature, and when that light was created, the
33:17
Speaker 1: universe was still pretty hot. It was several thousand degrees kelvin,
33:21
Speaker 1: which is about the same temperature as the surface of
33:23
Speaker 1: the Sun, which produces visible light. So when the CMB
33:27
Speaker 1: light was created, it was in the visible spectrum. You
33:30
Speaker 1: could have seen it if Jeanie had her eyeballs back
33:33
Speaker 1: in the early universe. Back then, she could have seen
33:35
Speaker 1: the CMB with her eyeballs. Now, you're right, when you
33:38
Speaker 1: look up in the night sky, you don't see it.
33:40
Speaker 1: That's because it's no longer at that frequency. It's been
33:43
Speaker 1: stretched by the expansion of the universe. Down to much
33:46
Speaker 1: much longer wavelengths, right, and that's why you need like
33:50
Speaker 1: infrared telescopes, right exactly. But it's too low frequency for
33:55
Speaker 1: us to see, right. It started out in the visible
33:56
Speaker 1: spectrum and got stretched out below the visible spectrum very
34:00
Speaker 1: very long wavelengths infrared, and so that's why we need
34:03
Speaker 1: really sensitive telescopes in order to see it, because it's
34:06
Speaker 1: now super duper infrared. And people say the temperature of
34:09
Speaker 1: the universe is two point seven three degrees kelvin. What
34:12
Speaker 1: they're talking about is the temperature a plasma would have
34:16
Speaker 1: to be to generate the photons that we see in
34:19
Speaker 1: the CMB. The plasma that actually generated those photons much
34:24
Speaker 1: much earlier, was much hotter, but then it's light got
34:27
Speaker 1: stretched out, so now it looks like a plasma that's
34:30
Speaker 1: much cooler generated this light. Right. So that's a cosmic
34:34
Speaker 1: microwave background radiation which comes from the moment when the
34:37
Speaker 1: universe became transparent and not hazy. But that's I wonder
34:41
Speaker 1: if that's really what would fit into her definition of
34:45
Speaker 1: the first light, Like, you know that the light still
34:47
Speaker 1: existed when the universe was hazy and opaque, right, yeah, exactly,
34:51
Speaker 1: So backing up again, the universe started out really really hot,
34:54
Speaker 1: and then as it cools, it passes into the visible spectrum.
34:58
Speaker 1: That happened before this moment when the universe became transparent,
35:02
Speaker 1: but just about the same time. It's like an interesting
35:04
Speaker 1: overlap here that the universe became transparent around the same
35:08
Speaker 1: time as it became visible. The temperature for hydrogen become
35:12
Speaker 1: neutral is about the same as the temperature of the
35:15
Speaker 1: surface of the sun where visible light is generated. Right, So,
35:19
Speaker 1: then as the universe moved into the visible spectrum, what
35:22
Speaker 1: would have been the first color that you would have
35:24
Speaker 1: seen if you were there and was able to survive, Like,
35:27
Speaker 1: what's the highest frequency color that we can see with
35:30
Speaker 1: our eyes? Yeah, it'd be like the most violet violet, right,
35:34
Speaker 1: it'd be like super duper purply blue is the highest
35:37
Speaker 1: frequency light that we can seem. So then the first
35:40
Speaker 1: color was blue, That was right. I don't know if
35:46
Speaker 1: purple and blue are the same, but yeah, it was
35:48
Speaker 1: definitely very very bluey, very purply blue, ultra violet, he said,
35:52
Speaker 1: violet blue. All right, we'll go with purple. The first
35:55
Speaker 1: color in the universe was purple, basically, Yeah, I think
35:59
Speaker 1: that's true. It was purple. All right, Well, Genie, thank
36:01
Speaker 1: you for that question. I hope purple is your favorite
36:04
Speaker 1: color as well, because it is apparently the universe first color.
36:08
Speaker 1: But you know, if there are aliens out there and
36:10
Speaker 1: they have eyeballs and their brains interpret things differently, if
36:13
Speaker 1: they brains give them like a red experience for that
36:16
Speaker 1: same frequency and a purple experience for very low frequencies,
36:19
Speaker 1: then aliens would say a different color was the first color.
36:23
Speaker 1: And that's just because again, color is not part of
36:25
Speaker 1: the universe, it's part of our brains. So it's a
36:27
Speaker 1: very human thing to say that violet was the first
36:30
Speaker 1: color in the universe. It was the first human color
36:32
Speaker 1: in the universe, I suppose. Well, it's the first name
36:35
Speaker 1: that the human would give it. But the frequency was
36:37
Speaker 1: still the same, so we would all agree. I mean,
36:39
Speaker 1: the experience I have a violet might not be the
36:41
Speaker 1: same experience you have a violet, but we can all
36:44
Speaker 1: agree that about that frequency. That's true. Yeah, though aliens
36:48
Speaker 1: might be able to see much higher frequencies, and they
36:50
Speaker 1: might say an even higher frequency was visible before our violet.
36:55
Speaker 1: M I see, they might have a different first color,
36:58
Speaker 1: assuming they call it color. Maybe they spell over the
37:01
Speaker 1: K or something, but they put a U after the second. Oh,
37:08
Speaker 1: I think you went too far there, Yeah, who would
37:10
Speaker 1: do that? All right, well, I think then answers Jeannie's question.
37:13
Speaker 1: Thank you, Jeanie. And so we'll get to our last question.
37:16
Speaker 1: This one is about the universe tearing itself apart. So
37:20
Speaker 1: let's take that apart. But first let's take another quick break.
37:36
Speaker 1: All right, we're answering questions about the universe and our
37:38
Speaker 1: last question. It's a bit dramatic, a bit drastic, it
37:43
Speaker 1: certainly is, which is why we saved it from last.
37:46
Speaker 1: All right, our last question comes from Courtney, and she
37:48
Speaker 1: has a question about the universe. Hey, Daniel and Jorge,
37:53
Speaker 1: I have a question for y'all. Is our universe tearing
37:55
Speaker 1: itself apart? Is physics as we know and measure it
37:58
Speaker 1: stable enough to be really light upon? If so, for
38:01
Speaker 1: how long? If at the beginning of the universe the
38:04
Speaker 1: electro week force broke in one moment, everything was whizzing
38:08
Speaker 1: around at the speed of light, then suddenly the next
38:12
Speaker 1: some particles experienced mass, fundamentally altering the trajectory of our universe.
38:18
Speaker 1: Could we be looking forward to another dramatic change in
38:21
Speaker 1: how our physical forces manifest themselves? Could we measure that
38:25
Speaker 1: looking forward to hearing back? Thanks? All right, awesome question
38:29
Speaker 1: for Corney. I think really what she's asking is does
38:31
Speaker 1: she have to do her homework for tomorrow or do
38:34
Speaker 1: that errente she needs to do? Or if the universe
38:36
Speaker 1: just totally going to flip on itself or maybe she
38:40
Speaker 1: could be doing other things today. Yeah. I did get
38:42
Speaker 1: the sense that she was trying to make plans and
38:44
Speaker 1: she wanted to know how far in the future she
38:47
Speaker 1: needed to think, Like, if I buy this house, is
38:49
Speaker 1: it going to be for sale in twenty years or
38:51
Speaker 1: is the whole universe going to get shredded before that? Yeah?
38:54
Speaker 1: Do I still have to pay my mortgage? Or can
38:56
Speaker 1: I just buy the biggest mansion I can now because
39:00
Speaker 1: the universe is going to end? That's right, real estate
39:02
Speaker 1: investment advice from people you shouldn't be listening to about
39:05
Speaker 1: real estate. Well, she's going to ask a multipart question.
39:07
Speaker 1: She asked whether the universe is tearing itself apart, which
39:10
Speaker 1: I guess maybe is related to her second question, which
39:13
Speaker 1: is like how stable do we think the universe is? Like?
39:15
Speaker 1: Is it going to stay like this? Forever. Can we
39:18
Speaker 1: invest in real estate? Or is it possible for the
39:21
Speaker 1: universe to suddenly change tomorrow or today or right now
39:25
Speaker 1: and make it a whole different universe, And it maybe
39:28
Speaker 1: that happened, we would we notice even I really love
39:31
Speaker 1: this question because the touch is on one of the
39:32
Speaker 1: most interesting ideas in physics that I think is not
39:36
Speaker 1: very widely appreciated, And it's actually connected to Genie's question
39:40
Speaker 1: about like the temperature of the universe. You know, we
39:43
Speaker 1: think about the universe and how it works, but we're
39:46
Speaker 1: really just describing the universe in one phase. When I
39:49
Speaker 1: say phase, I don't mean like, you know, a toddler
39:51
Speaker 1: throwing a tantrum. More like a phase is in the
39:54
Speaker 1: state of matter. Like if you're a scientist and you're
39:56
Speaker 1: trying to understand water, then you might have one understanding
39:59
Speaker 1: of how works when it's a vapor, and another understanding
40:02
Speaker 1: of how it works when it's a liquid, and another
40:04
Speaker 1: understanding of how it works when it's a solid. Right,
40:06
Speaker 1: we notice these phase transitions when water changes its behavior
40:10
Speaker 1: pretty dramatically as it heats up or as it cools down,
40:14
Speaker 1: and we can have a law that describes each of
40:16
Speaker 1: those phases and in principle, if you had like the
40:19
Speaker 1: ultimate theory of physics, you could have a single law
40:22
Speaker 1: that describes all of them. But typically what we do
40:25
Speaker 1: is we have effective laws to describe one phase at
40:27
Speaker 1: a time. And so the universe, the whole universe is
40:32
Speaker 1: cooling down, as we talked about a minute ago, and
40:34
Speaker 1: so we think it's passing through different phases, and so
40:38
Speaker 1: our current understanding of physics, a standard model of quarks,
40:41
Speaker 1: the photons, the weak force, the Higgs boson, all that
40:43
Speaker 1: stuff just describes the current phase of the universe in
40:48
Speaker 1: the sense of like having an effective theory that describes
40:51
Speaker 1: how things work right now, right because as we kind
40:54
Speaker 1: of talked about a minute ago with Genie's question, the
40:57
Speaker 1: universe kind of went through a pretty significant a change
41:00
Speaker 1: early soon after the Big Bang, Like before this event,
41:05
Speaker 1: everything all the matter, what's had so much energy, so
41:08
Speaker 1: much velocity, so much going on that like not even
41:11
Speaker 1: protons and electrons could hold together or come together and
41:14
Speaker 1: stick into atoms and matter things that are just kind
41:17
Speaker 1: of like a giant plasma. And then when things cooled,
41:20
Speaker 1: when space expanded, things cool suddenly, like things clicked into
41:24
Speaker 1: atoms and the stuff we see today, which is I
41:27
Speaker 1: think what you're trying to say is similar to like
41:28
Speaker 1: what happens to vapor or ice. It's like the molecules
41:32
Speaker 1: are flying around, but at some point they lose so
41:34
Speaker 1: much energy that some of the other forces in plate
41:36
Speaker 1: start to click them together or to bring them together
41:39
Speaker 1: as a liquid exactly. And what Cordy is bringing up
41:43
Speaker 1: is another kind of phase transition, even deeper phase transition
41:46
Speaker 1: than just like how do protons and electrons click together?
41:50
Speaker 1: She was talking about the moment when things got mass.
41:53
Speaker 1: All right, we've described the nature of the universes. We
41:55
Speaker 1: understand it in terms of all these quantum fields that
41:58
Speaker 1: are slashing around, and we talk about how the Higgs
42:00
Speaker 1: field is there and it's giving mass to particles by
42:04
Speaker 1: interacting with them and changing how they moved through the
42:07
Speaker 1: universe and all of this stuff. But if you go
42:08
Speaker 1: back to one of our podcasts where we talk about
42:10
Speaker 1: the very early history of the universe, you know that
42:13
Speaker 1: there was a moment before this happened, before the Higgs
42:16
Speaker 1: field was giving mass to particles, when we still had
42:19
Speaker 1: this description of everything in terms of quantum fields, but
42:21
Speaker 1: effectively the universe was very different. Everything was basically mass
42:25
Speaker 1: less electrons and quarks and all this stuff. We're flying
42:28
Speaker 1: to the universe all at the speed of light before
42:30
Speaker 1: the Higgs boson sort of kicked in and gave everything mass.
42:34
Speaker 1: So that was another big phase transition in our universe.
42:38
Speaker 1: Now that one's pretty fundamental, like the universe went from
42:41
Speaker 1: not having mass to having mass. Things having mass, and
42:45
Speaker 1: you said, something clicked, but like the laws of physics change,
42:49
Speaker 1: or within our laws just some sort of potential change,
42:53
Speaker 1: or we reached the threshold where suddenly the laws preferred
42:56
Speaker 1: to be this way rather than having no mass, so
43:00
Speaker 1: that the laws we have now describe the universe now.
43:03
Speaker 1: And also before this transition, so same laws of physics,
43:06
Speaker 1: but you have different temperature. And so as the Higgs
43:09
Speaker 1: field was cooling down, it got stuck in sort of
43:12
Speaker 1: a local minimum, and that's what she referred to as
43:14
Speaker 1: electroweak symmetry breaking. It's got stuck in this sort of
43:18
Speaker 1: weird spot where it treats w's and z's differently from
43:21
Speaker 1: how it treats photons, and it gave those particles mass,
43:24
Speaker 1: and it gives mass to the other particles sort of
43:26
Speaker 1: because where it got stuck as the universe was cooling,
43:30
Speaker 1: So it's the same basic laws of physics, but as
43:32
Speaker 1: the universe cools down, the effect of those laws changes,
43:35
Speaker 1: and one of the effects is that the Higgs field
43:37
Speaker 1: got stuck in this weird spot and that's why these
43:40
Speaker 1: particles have mass. And so really, I think her question
43:43
Speaker 1: is like, do we expect further similar phase transitions in
43:46
Speaker 1: the future or the universe that could fundamentally change what
43:49
Speaker 1: we experience. Yeah, I guess she's not asking like can
43:53
Speaker 1: the laws change? He's more asking like, is the universe,
43:56
Speaker 1: like you said, is the universe stable? Are we like
43:58
Speaker 1: in a spot where the basic configuration of the universe
44:01
Speaker 1: is going to be the same, or can it change
44:03
Speaker 1: like it did once before? Though, you know, it is
44:05
Speaker 1: possible that the laws could change, because even though we
44:09
Speaker 1: can describe the history of the universe pretty far back
44:12
Speaker 1: using our laws and quantum fields, there's a moment beyond
44:15
Speaker 1: which we can't right at the very very beginning of
44:17
Speaker 1: the universe, just after inflation with things where at the
44:20
Speaker 1: plank temperature. We think our laws break down there, and
44:23
Speaker 1: before that we need something else, some theory of quantum
44:25
Speaker 1: gravity that's deeper. We think that even our laws of
44:29
Speaker 1: physics that do a great job of describing the universe
44:32
Speaker 1: today and very very far back in time. They are
44:34
Speaker 1: just effective laws. They're like understanding water when it's a
44:37
Speaker 1: liquid and how it flows, but not deeply understanding the
44:40
Speaker 1: true theory of water that would explain all of its phases.
44:44
Speaker 1: So there is a sense in which the actual effective
44:47
Speaker 1: laws of physics do change over time, though we don't
44:50
Speaker 1: know what's going to happen in the future. We think
44:52
Speaker 1: the universe is just going to keep cooling and probably
44:54
Speaker 1: this current effective set of laws are going to hold fast.
44:58
Speaker 1: But even if these laws hold fast, there might be
45:00
Speaker 1: phase transition still in our future. Right. We talked on
45:03
Speaker 1: the podcast once about how the Higgs field is sort
45:06
Speaker 1: of stuck in this one spot, but it's not that stable.
45:08
Speaker 1: We don't know if it's going to stay stuck in
45:11
Speaker 1: that spot or if it's going to collapse and change
45:14
Speaker 1: the masses of everything, and that would be like another
45:17
Speaker 1: effective phase transition. So it might be that sometime in
45:20
Speaker 1: the future, you know, maybe spurred on by particle collisions,
45:24
Speaker 1: that some super collider could spark a change in the
45:26
Speaker 1: Higgs field which creates an effective phase transition in the
45:29
Speaker 1: basic laws of physics. Yeah, I think we talked about
45:32
Speaker 1: this in our book. Frequently ask questions about the universe,
45:34
Speaker 1: But you know, is the universe is going to end
45:36
Speaker 1: at some point? Or how is the universe going to end?
45:38
Speaker 1: And one possibility is for this Higgs field to collapse,
45:42
Speaker 1: because it can collapse right like, it's sitting at a
45:45
Speaker 1: place where it can still fall down in terms of energy. Yeah,
45:49
Speaker 1: the reason the Higgs field does what it does is
45:51
Speaker 1: because it has a lot of energy still stored in it.
45:54
Speaker 1: It's like the whole universe is cooling down, but the
45:56
Speaker 1: Higgs field got stuck and sort of staying hot. But
45:59
Speaker 1: it's kind of like ball that's stuck on a shelf
46:01
Speaker 1: and it could roll off that shelf and fall further
46:04
Speaker 1: down in temperature. We don't really understand very well how
46:07
Speaker 1: stable the spot it's stuck in is and what it
46:11
Speaker 1: would take to sort of nudge it out of that,
46:13
Speaker 1: and so there's a possibility that it could collapse even further,
46:16
Speaker 1: and that would mean a change in the masses of
46:18
Speaker 1: all the particles, which would mean like chemistry out the window,
46:21
Speaker 1: need totally new chemistry, and you know, everything that relies
46:24
Speaker 1: on chemistry, like life and podcasts also out the window,
46:28
Speaker 1: and I guess buying a house also along with that.
46:32
Speaker 1: But I think you describe it as sort of like
46:34
Speaker 1: a spark and a spark propagating. I know we've covered
46:37
Speaker 1: this in the book, but it's almost like if something
46:40
Speaker 1: happens and does cause a Higgs boson to kind of
46:42
Speaker 1: fall over or give up its energy in one spot,
46:45
Speaker 1: it would basically cause the entire universe to do the same,
46:48
Speaker 1: Like it would spread out like a wave. Right, if
46:51
Speaker 1: it happened anywhere, it would spread out like a wave
46:54
Speaker 1: propagating at the speed of light. So it may have
46:56
Speaker 1: already happened somewhere else in the universe, and that wavefront
47:00
Speaker 1: of phase transitions is heading for us or maybe not,
47:04
Speaker 1: and maybe it'll be stable forever, right, And you're saying
47:06
Speaker 1: that one thing that could trigger it maybe is building
47:09
Speaker 1: a large particle collider, maybe under Geneva or something, yeah,
47:13
Speaker 1: or around the surface of the Moon or around the
47:16
Speaker 1: edge of the galaxy. It sounds like we need to
47:18
Speaker 1: shut those things down right away. It sounds like we
47:20
Speaker 1: need to build one and find out. That sounds like
47:26
Speaker 1: exactly the opposite thing. You want to find out if
47:28
Speaker 1: you can destroy the universe. I don't know. I'm pro curiosity.
47:30
Speaker 1: I don't know how you feel. I am pro not
47:32
Speaker 1: destroying the universe, because once you find out that you
47:35
Speaker 1: can destroy the universe, you've destroyed the universe, Daniel, but
47:40
Speaker 1: you've learned something along the way. No, because you won't
47:43
Speaker 1: be here. Look what I'm saying, is nobody ever regretted
47:46
Speaker 1: destroying the universe. Well, I think the answer here for
47:50
Speaker 1: Corney is that go ahead and buy that house you're
47:53
Speaker 1: thinking of buying. And maybe you should write to Daniel
47:55
Speaker 1: tell him not to destroy the universe. Send your questions,
48:00
Speaker 1: your ideas, your requests to not destroy the universe. Two
48:04
Speaker 1: questions at Daniel and Jorge dot com. All right, thank
48:07
Speaker 1: you everyone for sending us their question. A lot of
48:10
Speaker 1: interesting things we've learned about here. I think we can
48:12
Speaker 1: give ourselves a pat on the back, Daniel, maybe with
48:14
Speaker 1: a third army out at the top of your head. Yeah, exactly,
48:17
Speaker 1: it's busy scratching my head right now. You can give
48:19
Speaker 1: yourself three handshakes. Triple high five. It would be the
48:21
Speaker 1: highest of fives. M it would be a triple five. Yeah,
48:25
Speaker 1: it would be a fifteen. All right, Well, thanks for
48:28
Speaker 1: joining us. We hope you enjoyed that. See you next time.
48:39
Speaker 1: Thanks for listening, and remember that Daniel and Jorge Explain
48:41
Speaker 1: the Universe is a production of iHeartRadio. For more podcast
48:45
Speaker 1: from my heart Radio, visit the iHeartRadio app, Apple Podcasts,
48:49
Speaker 1: or wherever you listen to your favorite shows.