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Is the Universe Fine-tuned for life? · Daniel and Kelly’s Extraordinary Universe

• 0:07
  Speaker 1: Sometimes physics can make you feel a little insignificant. You know,
• 0:12
  Speaker 1: the Earth isn't the center of the universe. It's just
• 0:14
  Speaker 1: one of many tiny rocks orbiting countless suns and zillions
• 0:18
  Speaker 1: of galaxies. And the universe has existed for billions of
• 0:22
  Speaker 1: years before we came along, happily doing its thing without us.
• 0:26
  Speaker 1: But sometimes physics can also make us feel quite special.
• 0:30
  Speaker 1: When we look at the laws of nature and the
• 0:32
  Speaker 1: values of its constants, life seems to depend very strongly
• 0:36
  Speaker 1: on these little details. A tiny tweak here or a
• 0:40
  Speaker 1: change there in life as we know it would be impossible.
• 0:44
  Speaker 1: Stephen Hawkings said, quote the laws of science as we
• 0:47
  Speaker 1: know them at present contained many fundamental numbers, like the
• 0:51
  Speaker 1: size of the electric charge of the electron, or the
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  Speaker 1: ratio of the masses of the proton and the electron.
• 0:56
  Speaker 1: The remarkable fact is that the values of these numbers
• 0:59
  Speaker 1: seem to have been very finely adjusted to make possible
• 1:03
  Speaker 1: the development of life. End quote? Is Hawking right? Can
• 1:08
  Speaker 1: it physics tell us if we're special? Can it reveal
• 1:11
  Speaker 1: if the universe seems to have been set up so
• 1:13
  Speaker 1: that life can exist? Welcome to Daniel and Kelly's extraordinarily
• 1:19
  Speaker 1: important universe.
• 1:33
  Speaker 2: Hello. I'm Kelly Winer Smith.
• 1:35
  Speaker 3: I study parasites and space, and I'm so glad that
• 1:37
  Speaker 3: the universe is fine tuned for life, including parasitically.
• 1:43
  Speaker 1: Hi, I'm Daniel. I'm a particle physicist. I want to
• 1:46
  Speaker 1: unravel the nature of the universe so we know who
• 1:48
  Speaker 1: to blame for, including parasites.
• 1:50
  Speaker 3: Again, you know, we should blame someone for human and
• 1:52
  Speaker 3: livestock and pet parasites. If I could selectively remove those,
• 1:55
  Speaker 3: I would, right, yeah.
• 1:57
  Speaker 1: Right, mosquitoes? Whose idea was that?
• 2:00
  Speaker 2: A bad idea? Whoever's idea, it's a bad one.
• 2:03
  Speaker 1: I got some notes on the universe.
• 2:06
  Speaker 3: Yeah, I need to figure out how to give those
• 2:07
  Speaker 3: notes too. So here's my question for you. So we're
• 2:10
  Speaker 3: talking about life in the universe, and often when you
• 2:14
  Speaker 3: see depictions of aliens in movies or like comics or whatever,
• 2:18
  Speaker 3: they have tentacles. Daniel, do you think aliens are likely
• 2:23
  Speaker 3: to have tentacles?
• 2:26
  Speaker 1: I wonder what the origin of that is. Wow, Yeah,
• 2:29
  Speaker 1: it must be some early science fiction depiction attempting to
• 2:34
  Speaker 1: describe like life differently. I mean, one thing I love
• 2:37
  Speaker 1: in science fiction is you can see people doing this thing.
• 2:40
  Speaker 1: They are trying they're aware that life should be different
• 2:43
  Speaker 1: on other planets. We shouldn't just expect humans everywhere, and
• 2:46
  Speaker 1: they're adding little tweaks like Starchek is the most hilarious
• 2:48
  Speaker 1: version of this, right, They're like, how about humans but
• 2:50
  Speaker 1: wrinkly foreheads? Or humans but pointy ears? You know. It's
• 2:54
  Speaker 1: like the smallest nudge in that direction. It's pretty hilarious.
• 2:59
  Speaker 1: But the idea is right, you know, And so I
• 3:02
  Speaker 1: bet tentacles are just another move in that direction. Do
• 3:05
  Speaker 1: I expect life to have tentacles on other planets? Wow,
• 3:08
  Speaker 1: there's not a less qualified person to answer that question.
• 3:12
  Speaker 3: I mean, I don't know anyone else who thinks about
• 3:14
  Speaker 3: aliens as much as you do, Daniel, So I'm sure
• 3:16
  Speaker 3: there's some less qualified that's pro Jude.
• 3:20
  Speaker 1: Well, you know, there's a whole chapter in my new
• 3:22
  Speaker 1: book Do Aliens Speak Physics available now at Aliens Speak
• 3:26
  Speaker 1: Physics dot Com, where we talk about how aliens might
• 3:29
  Speaker 1: perceive the universe, what they might see, how they might
• 3:32
  Speaker 1: explore it, how they might sense the universe, and if
• 3:35
  Speaker 1: that might lead them to learn different things about the
• 3:37
  Speaker 1: universe and think about it differently. I don't think it
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  Speaker 1: matters so much if they're using tentacles or fingers or
• 3:43
  Speaker 1: weird slimy protrubances. But I do think it's interesting how
• 3:48
  Speaker 1: they might see the universe and sense it and think
• 3:50
  Speaker 1: about it differently.
• 3:51
  Speaker 3: Well, but like they're going to need a way to
• 3:53
  Speaker 3: pick up their iPhones to watch cat videos. Surely that's universal,
• 3:58
  Speaker 3: you know, I.
• 3:59
  Speaker 1: Think there was a lot lot of time on Earth
• 4:01
  Speaker 1: where life survived without cat videos. Kelly, what, Yeah, it's possible.
• 4:05
  Speaker 1: I know, seems inconceivable.
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  Speaker 3: If I, you know, try to work my way back
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  Speaker 3: through the haze of time, It's possible.
• 4:12
  Speaker 2: I didn't have an iPhone at some point.
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  Speaker 3: So today we're talking about whether or not the universe
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  Speaker 3: is fine tuned for life with or without cat videos and.
• 4:22
  Speaker 1: So, and this is a really fun topic because it
• 4:25
  Speaker 1: touches on physics. Of course, it forces us to think
• 4:28
  Speaker 1: about the structure of the universe, how is it organized?
• 4:31
  Speaker 1: But then my favorite bit, it asks us to wonder
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  Speaker 1: what that means? All right, what does it tell us
• 4:36
  Speaker 1: about the nature of the universe. So today we're going
• 4:39
  Speaker 1: to be walking a fine line between physics and philosophy,
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  Speaker 1: not just the ideas but their consequences.
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  Speaker 3: Oh amazing, all right, So at physics conferences. Do you
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  Speaker 3: all get philosophical or are you talking about like how
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  Speaker 3: to fix the particle collider? No?
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  Speaker 1: No, no, Philosophy is a bad word of physics conferences.
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  Speaker 4: No.
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  Speaker 1: No. Physicists are not interested in these questions, and a
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  Speaker 1: lot of them really look down there, knows that anybody
• 5:00
  Speaker 1: who is oh what a bum I mean. Fiman, for example,
• 5:04
  Speaker 1: said that physicists need philosophers as much as like birds
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  Speaker 1: need ornithologists.
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  Speaker 3: What yeah, well someone's got to study the birds. I
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  Speaker 3: do see the point.
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  Speaker 1: I mean, it's true that philosophy is not the central
• 5:19
  Speaker 1: concern of psists, like let's try to figure out how
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  Speaker 1: the universe works, but which questions are interesting definitely comes
• 5:26
  Speaker 1: from philosophy. Why these questions are interesting, what their answers mean,
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  Speaker 1: That's all philosophy. And the reason the whole field is fascinating,
• 5:33
  Speaker 1: in my opinion, is because the philosophical implications. Figuring out
• 5:37
  Speaker 1: what the universe has made out of tells you how
• 5:39
  Speaker 1: it works at the most basic level, reveals the true
• 5:41
  Speaker 1: nature of reality. That's all interesting because of philosophy. And
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  Speaker 1: I think physicists are all doing philosophy, they just don't
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  Speaker 1: realize it. Like a lot of them hold very strong
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  Speaker 1: philosophical opinions, like, yes, these particles are real even if
• 5:56
  Speaker 1: we weren't looking at them. It feels like a very naturalist,
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  Speaker 1: scientific view of the universe. But it's also a strong
• 6:01
  Speaker 1: philosophical opinion about what truth means that goes well beyond science.
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  Speaker 1: So yeah, I think the physics community should be more
• 6:09
  Speaker 1: open to philosophy.
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  Speaker 3: You gave a much deeper answer that I was expecting.
• 6:12
  Speaker 3: I just wanted to say, these things are really fun
• 6:14
  Speaker 3: to think about and to talk about.
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  Speaker 2: But yes, I agree with all the stuff that you
• 6:18
  Speaker 2: just said.
• 6:18
  Speaker 1: Also, you accidentally accessed a Daniel rant, so.
• 6:23
  Speaker 2: Well you kept it concise. I'm impressed. My Kelly rants
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  Speaker 2: can go on for hours.
• 6:27
  Speaker 1: But all right, all right, Well, I was wondering what
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  Speaker 1: people out there thought about this question whether the universe
• 6:34
  Speaker 1: is fine tuned for life, So I reached out to
• 6:37
  Speaker 1: our group of volunteers and asked them to chime in.
• 6:40
  Speaker 1: If you would like to join this group, please write
• 6:41
  Speaker 1: to us to questions at Danielankelly dot org. Life in
• 6:45
  Speaker 1: our universe is inevitable, and I believe that it is
• 6:49
  Speaker 1: also probably plentiful. Yeah, I think that life has evolved
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  Speaker 1: within the laws of physics that we have.
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  Speaker 5: I say no, because the laws of physics were operating
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  Speaker 5: long before or life existed on our planet. The laws
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  Speaker 5: of physics aren't as fine tuned as they could be,
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  Speaker 5: because I want to have a world where life is
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  Speaker 5: even crazier and there's way more connections that atom can
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  Speaker 5: make than what carbon does.
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  Speaker 1: That's a good question. Maybe, as in all biology, it
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  Speaker 1: depends what does that mean? Well, I don't believe so,
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  Speaker 1: I'm feel little bit of anything. It's the other way around.
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  Speaker 1: If you changed almost any parameter in physics, life couldn't exist.
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  Speaker 1: Life evolved according to the laws of physics.
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  Speaker 4: I think that while we might not exist if the
• 7:39
  Speaker 4: laws of physics were different, other people might, and those
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  Speaker 4: people would be inclined to look at their laws of
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  Speaker 4: physics and think they were fine tuned for them.
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  Speaker 1: A constance of physics that if they were off just
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  Speaker 1: by a small margin, there wouldn't be galaxies, elements, or
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  Speaker 1: life as we know it.
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  Speaker 4: You have all of these knobs with very specific numbers
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  Speaker 4: associated with many.
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  Speaker 1: Of which would destroy all life if altered.
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  Speaker 4: So you got me if by fine tuned for life
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  Speaker 4: you mean the ability to consume other forms of life
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  Speaker 4: and often shocking and horrifying ways.
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  Speaker 1: Then yes, I do think that the perception of our
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  Speaker 1: lives fine tunes our laws of physics.
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  Speaker 3: There were so many great answers here, and so many
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  Speaker 3: answers that made me think these people are really listening.
• 8:25
  Speaker 3: You know, it's biology. So it depends. Bravo, bravo.
• 8:30
  Speaker 1: Love the in joke responses that's nice.
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  Speaker 3: Yeah, but yeah, in general, great answers here.
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  Speaker 2: So let's go ahead and jump in.
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  Speaker 3: So you you wanted to know, is the universe fine
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  Speaker 3: tuned for life? What does fine tuned mean in particular?
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  Speaker 1: Yeah, this is a really interesting question philosophically, and I
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  Speaker 1: love you got to start with like, well, what do
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  Speaker 1: you even mean by the words in the question? You know,
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  Speaker 1: you're really digging into philosophy. So here this is inspired
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  Speaker 1: by the fact the physics has laws, you know, like
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  Speaker 1: F equals MA, or you know, the laws of general
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  Speaker 1: relativity or special relativity. But there are also numbers. You know,
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  Speaker 1: there's things like the speed of light, or there's the
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  Speaker 1: gravitational constant. There are numbers there. Sometimes we don't know
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  Speaker 1: why those numbers have their values. There are things that
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  Speaker 1: we just went and measured about the universe. The speed
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  Speaker 1: of light is a great example, like, we don't know
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  Speaker 1: why the speed of light is what it is. It
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  Speaker 1: could have been bigger, it could have been smaller, or
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  Speaker 1: could it is there some constraint there, And these numbers
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  Speaker 1: are important. You know. If you change these numbers, you
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  Speaker 1: change the conditions of the universe, the nature of our
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  Speaker 1: experience in the universe, and of course therefore the conditions
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  Speaker 1: for life. Take the speed of life. For example, if
• 9:43
  Speaker 1: the speed of light was much much bigger, then we
• 9:46
  Speaker 1: could see a much larger range of the universe, which
• 9:50
  Speaker 1: sounds great, right, But also more of the universe could
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  Speaker 1: see us, and an alien death ray could travel to
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  Speaker 1: Earth much more rapidly if the speed of light light
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  Speaker 1: was higher. So you know, if the speed of light
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  Speaker 1: was instantaneous, for example, then anywhere in the universe an
• 10:05
  Speaker 1: alien could point a death ray at us and just
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  Speaker 1: obliterate us with no warning. So you know, it changes
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  Speaker 1: the context of life. And people wonder, like, if these
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  Speaker 1: values are different and that changes the way life works,
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  Speaker 1: then why do they have these values, the ones that
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  Speaker 1: seem so well suited for life as we know it?
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  Speaker 3: Okay, so that's the essay answer to what does fine
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  Speaker 3: tunes me? What would the one sentence answer be, because
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  Speaker 3: I think I lost track a little bit at one point.
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  Speaker 1: Okay, the one sentence answer is like, there are numbers
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  Speaker 1: in the universe, and if you change them a little bit,
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  Speaker 1: life doesn't work the way we know that it does.
• 10:40
  Speaker 1: So why do they have these values?
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  Speaker 2: Amazing?
• 10:43
  Speaker 3: This is why you're such a great professor. Which are
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  Speaker 3: the numbers that we care about? Which are the ones
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  Speaker 3: that determine if there's life or not?
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  Speaker 1: Yes, So the example that I gave the speed of
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  Speaker 1: light is a very intuitive one, very concrete, but it's
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  Speaker 1: not actually the right way to think about these numbers.
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  Speaker 1: The numbers we should think about are not the nu
• 11:00
  Speaker 1: numbers that have units in them. We should think about
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  Speaker 1: the dimensionless numbers, the ones that are pure numbers. Because
• 11:06
  Speaker 1: if you think about it, like the speed of light,
• 11:08
  Speaker 1: it's three times ten to the eight meters per second
• 11:11
  Speaker 1: meters per second. It depends on these human things meters
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  Speaker 1: and seconds. And if you changed meters and seconds at
• 11:19
  Speaker 1: the same time, you could keep the speed of light
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  Speaker 1: the same, Or if you just change the length of
• 11:23
  Speaker 1: the definition of a meter, you could change the speed
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  Speaker 1: of light. So you know, you get on fuzzy philosophical
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  Speaker 1: grounds if you rest everything on the definition of human units.
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  Speaker 3: You've yet again convinced me that we need philosophy alongside physics. Okay,
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  Speaker 3: I think I see where you're coming from. You know,
• 11:39
  Speaker 3: like meters and things, they come in units of ten,
• 11:42
  Speaker 3: probably because we have ten fingers and time probably, Yeah,
• 11:46
  Speaker 3: why why do we have sixty seconds in a minute?
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  Speaker 2: Daniel?
• 11:48
  Speaker 3: Let's probably there's got to be a human explanation there too, right,
• 11:51
  Speaker 3: the universe didn't tell us there are sixty seconds in
• 11:54
  Speaker 3: a minute.
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  Speaker 1: Yeah. I don't think there's any astronomical connection to the
• 11:58
  Speaker 1: length of a minute or one of a second. You know.
• 12:00
  Speaker 1: The only things determined by astronomy are like the length
• 12:03
  Speaker 1: of a year, how long it takes the Earth to
• 12:05
  Speaker 1: go around the sun, and the length of a day,
• 12:07
  Speaker 1: how long it takes the Earth to spin. But even
• 12:10
  Speaker 1: those are local quantities right other places in the universe
• 12:13
  Speaker 1: they won't have the same year or the same day length.
• 12:17
  Speaker 1: So all of these are just human derived constants. And
• 12:19
  Speaker 1: the way to think about this and to wonder like
• 12:21
  Speaker 1: why is this important? Is to imagine whether you could
• 12:24
  Speaker 1: notice if these numbers are changed, you know. Imagine, for example,
• 12:27
  Speaker 1: I changed what a meter is, but I also spread
• 12:31
  Speaker 1: out the universe more right, Or I changed the speed
• 12:33
  Speaker 1: of light and I expanded the universe. You couldn't tell, right,
• 12:37
  Speaker 1: there's no difference. There's no experiment you could do to
• 12:39
  Speaker 1: determine whether I had transformed the universe, made it bigger,
• 12:43
  Speaker 1: but then also increased the length of a meter and
• 12:45
  Speaker 1: the speed of light or shrunk it. So these numbers,
• 12:48
  Speaker 1: if it's possible to change them and not have any
• 12:51
  Speaker 1: impact on the physics or the nature of our experience,
• 12:54
  Speaker 1: then they're not good choices for like the basic measurements
• 12:58
  Speaker 1: of the universe. So not only do we want to
• 13:00
  Speaker 1: be free of human bias because that feels weird and
• 13:04
  Speaker 1: local and colloquial and we can't talk to aliens about it.
• 13:06
  Speaker 1: Also we want to make sure that if we do
• 13:08
  Speaker 1: change these numbers, it really does change the universe in
• 13:11
  Speaker 1: a way that we can measure. That's why we focus
• 13:13
  Speaker 1: on dimensionless numbers, things that have no units in them.
• 13:17
  Speaker 3: This is why the meaning of life is forty two.
• 13:20
  Speaker 3: It doesn't have any dimensions. So it's true anywhere you.
• 13:22
  Speaker 1: Go exactly exactly, so bad examples of things that you
• 13:27
  Speaker 1: might think control the universe but don't actually are. Like
• 13:30
  Speaker 1: the example I gave earlier, this speed of light for
• 13:32
  Speaker 1: the reasons I just described, right, the speed of light.
• 13:35
  Speaker 1: It is a constant, but it has units, and so
• 13:37
  Speaker 1: you can change it as long as you also change
• 13:39
  Speaker 1: those arbitrary units and have no impact on the nature
• 13:42
  Speaker 1: of the universe. Another example is like the force of
• 13:45
  Speaker 1: gravity on Earth. Right, Yes, the force of gravity affects
• 13:49
  Speaker 1: the way life has evolved, but it actually comes from
• 13:52
  Speaker 1: other constants like the big gravitational constant and the mass
• 13:55
  Speaker 1: of Earth and all sorts of stuff, and of course
• 13:57
  Speaker 1: it has dimensions or the things like Avagadro's number. Right,
• 14:02
  Speaker 1: this is a dimensionless quantity, but it's totally arbitrary. It's
• 14:05
  Speaker 1: just a number we made up to feel useful. But
• 14:08
  Speaker 1: we have figured out a bunch of constants of the
• 14:10
  Speaker 1: universe that are dimensionless and that if you changed any
• 14:14
  Speaker 1: of them would significantly impact the nature of the universe
• 14:18
  Speaker 1: and life on Earth.
• 14:19
  Speaker 3: Okay, so it's not just that the number needs to
• 14:22
  Speaker 3: be dimensionless. It also needs to not have been arbitrarily
• 14:26
  Speaker 3: picked by people, and it needs to Why can't Why
• 14:30
  Speaker 3: does geometrical not work because wouldn't circles be the same anywhere.
• 14:34
  Speaker 1: Yeah, so you're thinking about like pi, right, is pi
• 14:37
  Speaker 1: a fundamental nature of the universe. It's a fascinating question,
• 14:40
  Speaker 1: Like pie is dimensionless? You're right, and it's not arbitrary. Right,
• 14:44
  Speaker 1: we didn't make up pie. Pi is the ratio of
• 14:48
  Speaker 1: the circumference of a circle to its diameter, and that
• 14:51
  Speaker 1: feels really deep. But I don't know that it's physical.
• 14:54
  Speaker 1: You know, it's geometrical. It tells you about the nature
• 14:57
  Speaker 1: of space, and so if, for example, space is curved,
• 15:01
  Speaker 1: pie has a different value. So in that sense it
• 15:03
  Speaker 1: tells you about the nature of curvature of the universe.
• 15:06
  Speaker 1: But that's already encapsulated in some of the other quantities.
• 15:09
  Speaker 1: I think. So you could argue about pie. I think
• 15:12
  Speaker 1: that's on the edge philosophically. It'd be really cool, though,
• 15:14
  Speaker 1: to talk to aliens about pie. It see if like
• 15:16
  Speaker 1: they have an understanding of it that's deeper than we do.
• 15:20
  Speaker 1: But it's sort of a function of three D space.
• 15:22
  Speaker 3: What I'm hearing you say is that if we meet aliens,
• 15:24
  Speaker 3: I can't start dissecting them until after you've asked them
• 15:27
  Speaker 3: about pie, because may I mean maybe they can tell
• 15:30
  Speaker 3: me about their parasites and we can skip the dissection.
• 15:32
  Speaker 1: Yeah, that's right. I'm sure they'd be very grateful for
• 15:35
  Speaker 1: you to pull whatever those bits are out of their
• 15:38
  Speaker 1: whatever holes.
• 15:39
  Speaker 3: Okay, all right, we're not going to get on the
• 15:43
  Speaker 3: topic of transient anuses again. So tell me about what
• 15:47
  Speaker 3: kind of dimensionless numbers are we looking for?
• 15:49
  Speaker 1: All right? So it's time to dive into the dimensionless
• 15:52
  Speaker 1: numbers that define the current human understanding of the universe.
• 15:56
  Speaker 1: And there are twenty six of them, right and six?
• 16:00
  Speaker 1: I know it sounds like a lot, right, It feels like, boy,
• 16:02
  Speaker 1: we have a lot of work to do because I
• 16:04
  Speaker 1: think the goal is a theory with zero numbers or
• 16:08
  Speaker 1: one number. Maybe I'm not sure you could actually get
• 16:10
  Speaker 1: to zero numbers. But the simpler the theory the better. Right,
• 16:14
  Speaker 1: But we have twenty six numbers.
• 16:15
  Speaker 3: So we have twenty six numbers in what is there
• 16:20
  Speaker 3: like an equation that determines if life is fine tuned?
• 16:23
  Speaker 3: What are these twenty six numbers all about?
• 16:24
  Speaker 1: These are twenty six numbers in our current laws of physics. Ok.
• 16:27
  Speaker 1: We don't have all the physics in one equation. We
• 16:29
  Speaker 1: have a bunch of equations and some of those equations
• 16:32
  Speaker 1: have numbers in them that we can't remove or derive
• 16:35
  Speaker 1: or predict. We just measure them. We don't know why
• 16:38
  Speaker 1: they have those values. So two of them relate to
• 16:41
  Speaker 1: the strength of forces. So, for example, the fine structure
• 16:44
  Speaker 1: constant is a number that's all over the place in physics,
• 16:48
  Speaker 1: and you can express it in terms of other physical constants.
• 16:52
  Speaker 1: It's the charge of an electron squared divided by h
• 16:55
  Speaker 1: Bar times the speed of light.
• 16:57
  Speaker 2: That's what I was going to guess.
• 17:01
  Speaker 1: Everybody just talks about that, right, yes, right back of
• 17:03
  Speaker 1: the hand. Yeah, yeah, Well it's a funny number because
• 17:06
  Speaker 1: you have to sort of put these other physical constants
• 17:08
  Speaker 1: together to get something that has no units. It's a
• 17:11
  Speaker 1: pure number. But this number controls the strength of electromagnetism.
• 17:16
  Speaker 1: Like if you increase the fine structure constant, electromagnetism gets
• 17:20
  Speaker 1: more powerful, meaning that like the force between two electrons
• 17:24
  Speaker 1: at a fixed distance would grow as you increase the
• 17:27
  Speaker 1: fine structure constant. Okay, And this also controls the weak force,
• 17:31
  Speaker 1: because you remember, the weak force is connected to electromagnetism. The
• 17:35
  Speaker 1: Higgs mechanism unifies these things. It's called electroweak symmetry and
• 17:39
  Speaker 1: tells us that the weak force and electromagnetism are actually connected.
• 17:43
  Speaker 1: So this one number determines the strength of electromagnetism and
• 17:47
  Speaker 1: also with another number we're going to talk about in
• 17:48
  Speaker 1: a minute of the strength of the weak force. So
• 17:51
  Speaker 1: that's three of the four forces already just from this
• 17:54
  Speaker 1: one number.
• 17:55
  Speaker 3: And so that sounds to me like if we tinkered
• 17:57
  Speaker 3: with any of those things, are day to day's experiences
• 18:00
  Speaker 3: would be very different. But have we already hit on
• 18:02
  Speaker 3: things that like we would die I or we would
• 18:05
  Speaker 3: not be here if they were different.
• 18:07
  Speaker 1: Yeah, this number is why we have chemistry. So like
• 18:09
  Speaker 1: if you have notes for the universe, we could already
• 18:11
  Speaker 1: start there because you know this controls like electron orbitals, right,
• 18:16
  Speaker 1: this controls how far they are away from the nucleus
• 18:19
  Speaker 1: because electrons in quantum states around the nucleus are there
• 18:23
  Speaker 1: in some sort of balance. They're balancing their energy with
• 18:25
  Speaker 1: the attraction from the nucleus. It's similar in spirit to
• 18:29
  Speaker 1: like an orbit. Right, we have a force between them,
• 18:31
  Speaker 1: but you still have velocity. Of course electrons are not
• 18:34
  Speaker 1: actually orbiting, but it's similar in spirit. And anyway, if
• 18:38
  Speaker 1: you increase the fine structure constant. Electron orbitals would shrink, right,
• 18:42
  Speaker 1: their distance on average of electrons from the nucleus would shrink.
• 18:45
  Speaker 1: It would make atoms harder for them to bond. And
• 18:49
  Speaker 1: if you released it, if you decreased the affine structure constant,
• 18:52
  Speaker 1: then the atoms would grow larger and they would have
• 18:54
  Speaker 1: a looser hold. And so all of chemistry would be different.
• 18:57
  Speaker 1: Because remember all of chemistry, the whole periodic table, and
• 19:01
  Speaker 1: how atoms interact and their properties. Are they bitter, are
• 19:04
  Speaker 1: they solid, are they metallic? Do they conduct? Depend on
• 19:07
  Speaker 1: the behavior of electrons around these nuclei and how they
• 19:11
  Speaker 1: like to touch each other or not, And this constant
• 19:14
  Speaker 1: directly affects them. So you tweak this thing even a
• 19:18
  Speaker 1: little bit, all of chemistry is different. Do you still
• 19:20
  Speaker 1: get water, we don't know. Do you still get all
• 19:23
  Speaker 1: sorts of things that allow life to form, you know,
• 19:26
  Speaker 1: DNA and RNA and all the complicated machinery of life
• 19:30
  Speaker 1: all depends on this number being what it is.
• 19:33
  Speaker 3: All right, So my existential dread is starting to creep
• 19:36
  Speaker 3: up as I think about all of these factors, where
• 19:38
  Speaker 3: if they change at all, life falls apart. And when
• 19:41
  Speaker 3: we get back from the break, we'll talk about more
• 19:43
  Speaker 3: of these things upon which our lives depend. Okay, So, Daniel,
• 20:06
  Speaker 3: we just finished talking about the fine structure constant. Yeah,
• 20:09
  Speaker 3: and you talked about how if it changed at all,
• 20:11
  Speaker 3: probably chemistry would change, which would mean life as we
• 20:14
  Speaker 3: know it would change. Before we get onto the next one,
• 20:16
  Speaker 3: I'm going to slow us down even farther, okay, and say,
• 20:19
  Speaker 3: how do we know for sure that there's not some
• 20:21
  Speaker 3: third or fourth thing out there that we haven't measured
• 20:24
  Speaker 3: that would like accommodate if we made some changes, or
• 20:28
  Speaker 3: like maybe we don't really understand what's important, Like how
• 20:30
  Speaker 3: I guess how sure are we that there's not something
• 20:33
  Speaker 3: we're missing here?
• 20:34
  Speaker 1: Well, there's lots of things we could be missing. It
• 20:36
  Speaker 1: could be, for example, that this number has to be
• 20:39
  Speaker 1: what it is. You know, we have a theory in
• 20:43
  Speaker 1: which this number is a parameter that's not predicted and
• 20:46
  Speaker 1: we have to go out and measure it, and so
• 20:48
  Speaker 1: in our theory, this number could have other values, like
• 20:51
  Speaker 1: if you're at the control panel of the universe, this
• 20:54
  Speaker 1: is just a knob, and according to our theory, you
• 20:57
  Speaker 1: could crank that number up or down, or you could
• 21:00
  Speaker 1: even be changing right, it's not guaranteed that this thing
• 21:04
  Speaker 1: is fixed. All of our measurements suggest that it's fixed,
• 21:07
  Speaker 1: and when we look back into the history of the universe,
• 21:09
  Speaker 1: we see physics playing out the same way with the
• 21:11
  Speaker 1: same find structure constant. So it appears to be constant.
• 21:15
  Speaker 1: But that's just a measurement. But it could be that
• 21:17
  Speaker 1: our theory is just incomplete, that there's a better theory
• 21:20
  Speaker 1: out there that's more clever, and it requires the fine
• 21:24
  Speaker 1: structure constant to be this value. It predicts it. I mean,
• 21:27
  Speaker 1: that would be Nobel Prize winning stuff. You come up
• 21:30
  Speaker 1: with another theory for electroname inmics that predicts this thing
• 21:33
  Speaker 1: and shows why it has to have this particular value.
• 21:36
  Speaker 1: We can't have any other value. Boom. You have left
• 21:40
  Speaker 1: us forward one thousand years or whatever in physics, and
• 21:43
  Speaker 1: you've shown us why this number is what it is.
• 21:46
  Speaker 1: So in that sense we could be missing something for sure.
• 21:48
  Speaker 2: Okay, great, that's what I was asking.
• 21:50
  Speaker 1: But there's lots of other numbers out there. And the
• 21:52
  Speaker 1: second one also relates to a force. So the other
• 21:56
  Speaker 1: quantum force that's out there is the strong nuclear force.
• 21:58
  Speaker 1: So that's four fundamental quantum forces and electricity magnetism, and
• 22:02
  Speaker 1: the weak force, which all bundle together into a single
• 22:04
  Speaker 1: electra week. And then the fourth fundamental force is the
• 22:07
  Speaker 1: strong nuclear force, which holds protons and neutrons together and
• 22:11
  Speaker 1: also holds the nucleus together and all that good stuff.
• 22:14
  Speaker 1: And this one we have not yet unified with the
• 22:16
  Speaker 1: other three quantum forces into a grand unified force. People
• 22:19
  Speaker 1: are working on that, but we don't have that figured
• 22:21
  Speaker 1: out yet. So we have a whole separate system of equations.
• 22:23
  Speaker 1: They're inspired by the same machinery. It's all quantum field theory,
• 22:27
  Speaker 1: but it's a different quantum field, and the numbers are
• 22:30
  Speaker 1: all different, and it uses weird color charges whatever. So
• 22:32
  Speaker 1: we got another number there, the strong coupling constant, and
• 22:36
  Speaker 1: that's just a number, and it tells us how strong
• 22:39
  Speaker 1: is the strong force. And it's a much bigger number
• 22:42
  Speaker 1: than the fine structure constant, which is why the strong
• 22:44
  Speaker 1: force is called the strong force, because it's so dang strong.
• 22:47
  Speaker 3: And because you physicists aren't super clever with your naming structures.
• 22:52
  Speaker 1: What would you have called the strong coupling constant killing.
• 22:55
  Speaker 2: The hulk force or something.
• 23:01
  Speaker 1: We hold nucleus together, that's right.
• 23:04
  Speaker 3: Right, already we've made improvements here. I'm available whenever you
• 23:08
  Speaker 3: guys need suggestions.
• 23:09
  Speaker 1: I'd love to zoom in on the nucleus and see
• 23:11
  Speaker 1: tiny little hulks in there. That would be better than gluons, right,
• 23:16
  Speaker 1: little hulcons or something.
• 23:17
  Speaker 2: Yeah, I'm going to copyright that little hulky nose.
• 23:22
  Speaker 1: Anyway. This also has a big impact on the nature
• 23:25
  Speaker 1: of life. We were talking a minute ago about the
• 23:28
  Speaker 1: electron and how that determines a lot of the properties
• 23:30
  Speaker 1: of the atom and chemistry, but of course the nucleus
• 23:33
  Speaker 1: is important too, and in the nucleus it's the strong
• 23:36
  Speaker 1: force that dominates. You have neutrons which have no charge,
• 23:39
  Speaker 1: and you have protons which have positive charge, and those
• 23:42
  Speaker 1: protons don't like to be near each other. But the
• 23:44
  Speaker 1: strong force is strong enough to overcome that and keep
• 23:47
  Speaker 1: all those positive charge protons bound together into a nucleus
• 23:51
  Speaker 1: and to create those protons and neutrons in the first place.
• 23:55
  Speaker 1: And that's really the building block of all of matter
• 23:58
  Speaker 1: and everything in the universe. So if the strong force
• 24:01
  Speaker 1: constant was different, you wouldn't get nuclei the same way.
• 24:04
  Speaker 1: You wouldn't get the same isotopes. You might not even
• 24:07
  Speaker 1: be able to manufacture these things in the hearts of stars.
• 24:10
  Speaker 3: Okay, yeah, that sounds pretty fundamental. Why can't we make
• 24:13
  Speaker 3: these things in the hearts of stars?
• 24:15
  Speaker 1: Yeah, So the strong force determines not just how protons
• 24:19
  Speaker 1: and neutrons come together, like how you build them, but
• 24:22
  Speaker 1: how they like to stick together well a nuclei that
• 24:24
  Speaker 1: they can form. And so you know what happens in
• 24:27
  Speaker 1: a nucleus is you have protons and neutrons and those
• 24:30
  Speaker 1: things are all neutral from a color charge point of view.
• 24:34
  Speaker 1: So you might wonder, like, how does the nucleus stick together? Anyway,
• 24:37
  Speaker 1: There's all these positive charges from protons and neutral charges
• 24:41
  Speaker 1: from neutrons, and everything is also neutral from a strong
• 24:45
  Speaker 1: forest point of view, So how does this stick together?
• 24:47
  Speaker 1: And the answer is residual strong charge because what's happening
• 24:51
  Speaker 1: is that the quarks in one proton are talking to
• 24:53
  Speaker 1: the quarks inside another neutron, and so those charges are
• 24:57
  Speaker 1: talking to each other. And that only happens if a
• 24:59
  Speaker 1: strong is strong enough. If you change the nature of
• 25:03
  Speaker 1: the strong force, then you might not get fusion. For example,
• 25:06
  Speaker 1: like what happens when you try to stick two protons
• 25:08
  Speaker 1: together inside the heart of a star to go from hydrogen,
• 25:11
  Speaker 1: which is what the big mag made to things like
• 25:14
  Speaker 1: helium and lithium and carbon and oxygen and all the
• 25:16
  Speaker 1: stuff that we need for life. Is you rely on
• 25:19
  Speaker 1: the strong force to be able to grab those protons
• 25:21
  Speaker 1: when they get close enough and stick them together. So
• 25:24
  Speaker 1: you start changing with the strong force, you're going to
• 25:26
  Speaker 1: change fundamentally the chemistry, the fusion that's happening inside the
• 25:30
  Speaker 1: hearts of stars, and some of these steps in nucleosynthesis
• 25:34
  Speaker 1: are pretty tricky. So to get carbon, for example, requires
• 25:37
  Speaker 1: like a complicated combination of three helium simultaneously, and like
• 25:42
  Speaker 1: this is very dependent on the strong force. So if
• 25:46
  Speaker 1: you have your hand on that knob and you like
• 25:48
  Speaker 1: accidentally tweak it a little bit, you could change fundamentally
• 25:51
  Speaker 1: what's happening inside all the stars in the universe.
• 25:53
  Speaker 3: All right, So I'm feeling a little bit uncomfortable that
• 25:55
  Speaker 3: you keep talking about chemistry, but we should push on.
• 25:58
  Speaker 2: So this is the strong coupling.
• 26:00
  Speaker 3: So for the fine structure constant, you gave us an
• 26:02
  Speaker 3: equation to let us know what values are going in there.
• 26:06
  Speaker 3: What values go into the strong coupling constant?
• 26:09
  Speaker 1: Yeah, great question. The strong coupling constant is just a number,
• 26:13
  Speaker 1: and it's one that we derived sort of later on,
• 26:15
  Speaker 1: So we just measured it directly because we didn't even
• 26:18
  Speaker 1: know about the strong force until, you know, a few
• 26:20
  Speaker 1: decades or almost a century ago, Whereas the fine structure
• 26:24
  Speaker 1: constant comes from electromagnetism, and there were earlier experiments, you know,
• 26:28
  Speaker 1: things to like measure the speed of light and things
• 26:30
  Speaker 1: to measure each bar, and then we derived most of
• 26:32
  Speaker 1: the theory of electromagnetism in terms of those existing constants,
• 26:37
  Speaker 1: and then later realized, oh, we should put these together
• 26:39
  Speaker 1: in terms of a dimensionless one. So short answer is,
• 26:42
  Speaker 1: we can't express the strong coupling constant in terms of
• 26:46
  Speaker 1: other constants because we realized later on, oh, we should
• 26:48
  Speaker 1: just define the dimensionless thing first. So the fine structure
• 26:52
  Speaker 1: constant is a bit of a historical anomaly, and we
• 26:55
  Speaker 1: sort of came to this way of thinking about things
• 26:57
  Speaker 1: later on.
• 26:58
  Speaker 3: Your initial explanation convinced me that this is important. But
• 27:03
  Speaker 3: the explanation you just gave me for how we determined
• 27:05
  Speaker 3: the value does not convince me that this is a
• 27:09
  Speaker 3: that we have figured out the right way to measure this.
• 27:11
  Speaker 1: Well, we don't know that we figured it out. The
• 27:13
  Speaker 1: right way. But we have a theory, and that theory
• 27:15
  Speaker 1: has a number in it. We can't predict that number. Okay,
• 27:18
  Speaker 1: like our theory of the strong force would work with
• 27:21
  Speaker 1: different values of this knob. You know, you make it
• 27:24
  Speaker 1: more powerful, you could make it less powerful. Our theory
• 27:26
  Speaker 1: essentially describes a huge range of possible strong forces, and
• 27:31
  Speaker 1: then we have to go out in the universe and
• 27:32
  Speaker 1: figure out which one do we have. Oh, we have
• 27:34
  Speaker 1: the one where the knob is set to this value.
• 27:36
  Speaker 1: And then of course the question why what does it mean?
• 27:40
  Speaker 1: And that's the philosophical joy of physics, right You discover
• 27:42
  Speaker 1: the universe is set up in a certain way, and
• 27:44
  Speaker 1: then you wonder why this way and not some other way?
• 27:47
  Speaker 1: Does it have to be this way? What does it
• 27:49
  Speaker 1: mean that it is this way? But what we know
• 27:51
  Speaker 1: is that this is a number we have no explanation for.
• 27:55
  Speaker 1: It's independent as far as we know of the other
• 27:57
  Speaker 1: constant find structure constant. You could change strong cupling constant
• 28:01
  Speaker 1: separately from the fine structure constant and you would definitely
• 28:04
  Speaker 1: notice and any change you would observe. So we can't
• 28:07
  Speaker 1: explain it. And it seems very sensitive to the value
• 28:10
  Speaker 1: that it's set to. So yeah, I think it's pretty
• 28:13
  Speaker 1: good example of something that's fine tuned.
• 28:15
  Speaker 3: No, biology is so complicated, you guys are always like,
• 28:18
  Speaker 3: it defends but right anyway, So if I had to
• 28:22
  Speaker 3: guess some other values that should show up in the constant,
• 28:24
  Speaker 3: I would guess that it would have something to do
• 28:27
  Speaker 3: with like the mass of the mass particles in the
• 28:30
  Speaker 3: force particles, but those would have dimensions because they'd be
• 28:35
  Speaker 3: mass and so yes, so I'm wrong.
• 28:38
  Speaker 1: You're mostly right. I mean you're on the right track.
• 28:40
  Speaker 2: Oh good.
• 28:40
  Speaker 1: Definitely, the masses of the particles influence the way things happen.
• 28:44
  Speaker 1: You know, if the electron were heavier, if the electron
• 28:46
  Speaker 1: were lighter, you would get different chemistry. If the heavy
• 28:50
  Speaker 1: versions of the upquirk were lighter, then they might exist
• 28:54
  Speaker 1: more often and play a role in life for example.
• 28:56
  Speaker 1: So you definitely need to capture that somehow. But you're right.
• 28:59
  Speaker 1: You also want to avoid dimension full numbers things that
• 29:03
  Speaker 1: are related in terms of mass. So we have twelve
• 29:06
  Speaker 1: particle masses for the matter particles, there are twelve fermions.
• 29:10
  Speaker 1: There's six quarks up down charm strange bottom top, and
• 29:14
  Speaker 1: six leptons electron muon tau and then the three neutrinos.
• 29:19
  Speaker 1: So that's twelve numbers, and we can make them dimensionless
• 29:22
  Speaker 1: just by expressing them relative to g which is the
• 29:25
  Speaker 1: gravitational constant, And so we can't sort of cook up
• 29:28
  Speaker 1: a dimensionless number which reflects these masses. Think about it, like,
• 29:32
  Speaker 1: what we're doing here is expressing the mass ratios.
• 29:35
  Speaker 3: More like, so, why is it correct to be looking
• 29:37
  Speaker 3: at the mass relative to gravity as opposed to relative
• 29:40
  Speaker 3: to the average mass of an elephant. Why is gravity
• 29:43
  Speaker 3: the right the right thing to use to make your
• 29:47
  Speaker 3: mass dimensionless?
• 29:48
  Speaker 1: Yeah, yeah, because the nature of the universe depends on
• 29:53
  Speaker 1: this ratio. So if you cranked down the gravitational constant
• 29:57
  Speaker 1: and made everything weaker, and then you cranked up the
• 29:59
  Speaker 1: mass to compensate, everything would behave the same gravitationally, And
• 30:04
  Speaker 1: the opposite is true too. If you made gravity stronger
• 30:06
  Speaker 1: and then you just weakened all the masses, you wouldn't notice.
• 30:09
  Speaker 1: And so it's really this ratio that determines the behavior
• 30:12
  Speaker 1: of these things, whether they decay in to each other,
• 30:14
  Speaker 1: all the masses, all this kind of stuff, and so boom,
• 30:17
  Speaker 1: that's twelve numbers right there, And that's kind of a mess.
• 30:21
  Speaker 1: You know, like these other things, like, okay, they're fundamental
• 30:24
  Speaker 1: forces and determined chemistry, you could begrudge a couple of them.
• 30:28
  Speaker 1: It feels like icky to me that we have twelve
• 30:30
  Speaker 1: numbers here.
• 30:31
  Speaker 3: I mean it's divisible by two. That feels like a
• 30:34
  Speaker 3: thing that physicists like. It would be icky er to
• 30:37
  Speaker 3: me if there was like something that had three instead
• 30:39
  Speaker 3: of something divisible by two.
• 30:42
  Speaker 1: Yeah, that's true. I mean I think it feels icky
• 30:44
  Speaker 1: for a couple of reasons. One is I want this
• 30:46
  Speaker 1: number to be small. I mean the number of numbers.
• 30:49
  Speaker 1: I wish the humanity had a theory with like one, two,
• 30:52
  Speaker 1: three numbers. It would feel like we were on the
• 30:53
  Speaker 1: verb of figuring it all out. So boom, adding twelve
• 30:56
  Speaker 1: and one fell swoop. Ugh. That's like an admission that
• 30:59
  Speaker 1: were newer clo to the answer. And I think it
• 31:02
  Speaker 1: also reflects the fact that we haven't solved another mystery,
• 31:05
  Speaker 1: which is where this twelve comes from, which is why
• 31:07
  Speaker 1: are there twelve particles? Right? It feels like this is
• 31:10
  Speaker 1: just wrapping up one piece of ignorance into another.
• 31:13
  Speaker 2: That's what I say.
• 31:14
  Speaker 1: There should be an explanation for like why do we
• 31:17
  Speaker 1: have three copies? Of every particle. What it's the relationship
• 31:20
  Speaker 1: between the quarks and leftons. Anyway, those are deeper mysteries,
• 31:23
  Speaker 1: and I feel like if those were solved, then we
• 31:26
  Speaker 1: could reduce the number of numbers, but we aren't there yet,
• 31:29
  Speaker 1: so we've got to pay the price and add twelve
• 31:32
  Speaker 1: numbers to our list. And you know, in terms of sensitivity,
• 31:35
  Speaker 1: like obviously the masses of the up, down, and electron
• 31:39
  Speaker 1: are very important because those are the things the building
• 31:41
  Speaker 1: blocks of life as we know it, and atomic matter
• 31:44
  Speaker 1: and you know, me and you and bananas and kittens
• 31:46
  Speaker 1: and all that stuff. The other particles, like the top
• 31:49
  Speaker 1: court it's super heavy and so it rarely appears in
• 31:53
  Speaker 1: the universe outside of like high energy collisions at the
• 31:56
  Speaker 1: LHC or alien facilities or cosmic rays. So probably life
• 32:00
  Speaker 1: is less sensitive to that. Like if you cranked up
• 32:03
  Speaker 1: the top quark mass or cranked it down, probably you
• 32:06
  Speaker 1: would still get life pretty much as we know it.
• 32:08
  Speaker 1: Particle physicists might discover it earlier or later, so the
• 32:12
  Speaker 1: Nobel Prize trajectory would be different, like the specific scientific history.
• 32:18
  Speaker 1: But you could make a pretty good argument that we're
• 32:19
  Speaker 1: not that sensitive to the mass of the top quark
• 32:22
  Speaker 1: for example.
• 32:22
  Speaker 3: Well, and I think giving out of Nobel prizes is
• 32:25
  Speaker 3: not like a fundamental feature of the universe. I don't
• 32:27
  Speaker 3: know that we need to account for that necessarily.
• 32:30
  Speaker 1: But the other side of this, the strength of gravity
• 32:32
  Speaker 1: is really important. You know, if gravity were a lot weaker,
• 32:36
  Speaker 1: then we wouldn't get it clumping things together. You know,
• 32:40
  Speaker 1: the whole history of the universe is that we start
• 32:43
  Speaker 1: with very dense plasma, which has some slight over densities
• 32:48
  Speaker 1: and slight under densities due to quantum fluctuations, and it's
• 32:52
  Speaker 1: dense enough, and gravity is strong enough, despite its overwhelming
• 32:55
  Speaker 1: weakness to start gathering this stuff together to form structure.
• 32:58
  Speaker 1: So structure in the universe only comes because of gravity,
• 33:03
  Speaker 1: and because gravity is powerful enough to pull this stuff together.
• 33:06
  Speaker 1: If gravity were a little weaker, then you wouldn't get galaxies.
• 33:09
  Speaker 1: You wouldn't get stars and planets. As it is, the
• 33:12
  Speaker 1: gravity of atomic matter of the protons and neutrons and
• 33:15
  Speaker 1: electrons wasn't enough to form galaxies and stars and planets.
• 33:20
  Speaker 1: We needed help from the dark matter. Like if you
• 33:22
  Speaker 1: had a universe without dark matter, just with the normal
• 33:26
  Speaker 1: matter atoms and whatever, you wouldn't get galaxies and stars
• 33:29
  Speaker 1: and planets fourteen billion years into the universe. It would
• 33:32
  Speaker 1: take a lot lot longer if it ever happened at all.
• 33:35
  Speaker 1: So it takes not just gravity, but the right amount
• 33:38
  Speaker 1: of gravity and the right density of dark matter to
• 33:41
  Speaker 1: construct this structure that we live on. The whole framework
• 33:45
  Speaker 1: of the universe depends on gravity having its strength, all.
• 33:49
  Speaker 3: Right, So now you've convinced me that it's important to
• 33:51
  Speaker 3: have gravity in here instead of the average mass of.
• 33:53
  Speaker 2: A big element.
• 33:54
  Speaker 1: But it also goes the other direction, like if gravity
• 33:59
  Speaker 1: was too strong, then we wouldn't have the universe that
• 34:02
  Speaker 1: we know and love. We would have a lot more
• 34:04
  Speaker 1: black holes. It would like pull stuff together more rapidly.
• 34:08
  Speaker 1: We'd have smaller stars because you get more seeding of
• 34:11
  Speaker 1: individual bits. Like remember the way stars forms. You have
• 34:14
  Speaker 1: a huge cloud of gas and there are little seeds there,
• 34:17
  Speaker 1: little places where gravity is slightly more powerful. But if
• 34:20
  Speaker 1: gravity was everywhere more powerful, you get more seeds and
• 34:23
  Speaker 1: you had with smaller stars. And smaller stars are colder,
• 34:26
  Speaker 1: like our sun is unusually big and hot for the universe.
• 34:30
  Speaker 1: So in a universe with stronger gravity, you get more
• 34:34
  Speaker 1: black holes and a bunch of small cold stars, and
• 34:37
  Speaker 1: that would be a very different kind of universe to
• 34:39
  Speaker 1: grow up in.
• 34:40
  Speaker 3: And so is the fact that our sun is unusually
• 34:42
  Speaker 3: big and hot. Does that kind of explain why life
• 34:45
  Speaker 3: is so rare in the universe that you kind of
• 34:47
  Speaker 3: need a big, hot sun.
• 34:49
  Speaker 1: It's a hypothesis I've heard, you know, because most of
• 34:51
  Speaker 1: the stars in the galaxy are red dwarfs. So why
• 34:54
  Speaker 1: didn't we evolve around a red dwarf? Does that mean
• 34:57
  Speaker 1: that the sun is the only kind of place that
• 34:58
  Speaker 1: life can evolve or does it just mean we got
• 35:01
  Speaker 1: lucky and got a bigger, hotter sun. And it's just
• 35:04
  Speaker 1: you know, in most universes we would have evolved around
• 35:06
  Speaker 1: red dwarfs. Red dwarfs seem a little bit more chaotic
• 35:09
  Speaker 1: there may be not as stable as our star is.
• 35:12
  Speaker 1: But this is the problem with an equals one philosophizing, Right,
• 35:15
  Speaker 1: we have one example and we're trying to draw conclusions
• 35:18
  Speaker 1: from it. You know how dangerous that is. Like you
• 35:20
  Speaker 1: have two kids, they're very different. I have two kids,
• 35:22
  Speaker 1: they're very different. Imagine you only had one kid and
• 35:25
  Speaker 1: you're like, well, every kid that I have is like
• 35:27
  Speaker 1: this kid. Obviously that's not true, you know, And so
• 35:30
  Speaker 1: it's very dangerous to generalize from one example to assume
• 35:35
  Speaker 1: that this example tells you something inherent about the process
• 35:39
  Speaker 1: you're studying. So it's pretty dangerous.
• 35:41
  Speaker 3: Yeah, let's take a break and then we'll talk about
• 35:43
  Speaker 3: the last few constants that determine whether or not you
• 35:46
  Speaker 3: get to stay alive. All right, Daniel, we're talking about
• 36:08
  Speaker 3: constants that are necessary for life as we know it.
• 36:11
  Speaker 3: Which constants have we not talked about yet?
• 36:13
  Speaker 1: So there's a few more messy particle physics constants that
• 36:16
  Speaker 1: indicate that particle physicists really haven't figured it out yet.
• 36:19
  Speaker 1: There's three more particle masses we have to account for.
• 36:23
  Speaker 1: This is the Higgs Boson mass, the W mass, and
• 36:26
  Speaker 1: the Z mass. And the W and Z mass are
• 36:29
  Speaker 1: the reason that the weak force is weaker than electromagnetism.
• 36:32
  Speaker 1: So the fine structure constant sets the strength of electroweak force.
• 36:36
  Speaker 1: But part of that electroweak force is the weak force,
• 36:39
  Speaker 1: and that's weaker because the W and Z masses have
• 36:41
  Speaker 1: the values that they have. We don't know why they are,
• 36:44
  Speaker 1: you know, according to our theory, there could have been
• 36:46
  Speaker 1: different values there. They tend to be very large, which
• 36:48
  Speaker 1: makes the weak force very weak. In other universes, maybe
• 36:52
  Speaker 1: the weak force is stronger, and they didn't call it
• 36:54
  Speaker 1: the weak force, you know, called the mini hulk force
• 36:57
  Speaker 1: or something like that.
• 36:58
  Speaker 2: That's the universe I want to live in.
• 37:00
  Speaker 1: Yeah, the Higgs Boson is a special mystery. Why it
• 37:02
  Speaker 1: has the value that it does. We suspect the Higgs
• 37:05
  Speaker 1: Boson mass should be much much bigger. Our calculations for
• 37:08
  Speaker 1: the Higgs Boson mass involve calculating a ten digit number
• 37:12
  Speaker 1: and then subtracting from it another ten digit independent number
• 37:16
  Speaker 1: and getting this three digit mass. The Higgs Boson masses
• 37:19
  Speaker 1: one hundred and twenty five GeV. But like, what are
• 37:21
  Speaker 1: the odds having these two ten digit numbers exactly balanced
• 37:25
  Speaker 1: or almost exactly balanced. So the Higgs mass itself, people think,
• 37:28
  Speaker 1: is fine tuned and it controls the masses of everything else.
• 37:32
  Speaker 1: And so this whole thing feels like very arbitrary and
• 37:36
  Speaker 1: not well understood. So that's three more masses.
• 37:39
  Speaker 2: And so here too, we've got masses, and so what
• 37:41
  Speaker 2: are they relative to?
• 37:43
  Speaker 1: Yeah, good point, they're relative again to the gravitational constant
• 37:46
  Speaker 1: to big G. So we can keep them dimensionless.
• 37:49
  Speaker 3: Okay, the fact that there's three feels wrong, but we'll
• 37:52
  Speaker 3: move on.
• 37:54
  Speaker 1: I guess you're not Catholic. You don't find the universe
• 37:56
  Speaker 1: to be three ish fundamentally. Huh.
• 37:58
  Speaker 3: I was raised Catholic, but I don't go to mess anymore.
• 38:03
  Speaker 2: My apologies.
• 38:05
  Speaker 1: Well, that's probably just because of the fine tuning of
• 38:07
  Speaker 1: the constants. It's not your fault.
• 38:08
  Speaker 2: Oh yeah, okay.
• 38:09
  Speaker 1: So then we have eight more parameters that mean particle
• 38:13
  Speaker 1: physicists haven't figured it out yet, and these are how
• 38:15
  Speaker 1: the fermions talk to each other. We have these complicated
• 38:18
  Speaker 1: mixing parameters that tell us like how different neutrinos turn
• 38:22
  Speaker 1: from one into another, or how quarks can turn from
• 38:25
  Speaker 1: one flavor into another flavor. And so there's eight numbers
• 38:28
  Speaker 1: there that we just measure in the universe. We can't predict.
• 38:31
  Speaker 1: We don't know why they have their values. I hope
• 38:33
  Speaker 1: alien physicists have figured it out. But again, these things
• 38:36
  Speaker 1: determine the nature of the universe, That determine how often
• 38:39
  Speaker 1: particles change from one kind to the other. Probably life
• 38:42
  Speaker 1: is not super sensitive to these because it mostly involves
• 38:46
  Speaker 1: the heavier, rarer particles that we don't see mostly in
• 38:50
  Speaker 1: terms of life. But you know, we don't understand these
• 38:52
  Speaker 1: things super well. These things could also determine things like
• 38:56
  Speaker 1: the matter anti matter asymmetry in the universe. I think
• 38:59
  Speaker 1: a lot of this is why we have matter and
• 39:02
  Speaker 1: not antimatter in the universe. So in a universe where
• 39:04
  Speaker 1: these numbers are different, you might have a perfect balance
• 39:07
  Speaker 1: between matter and antimatter. And then in the beginning of
• 39:09
  Speaker 1: the universe, you get no electrons, you get no protons,
• 39:13
  Speaker 1: you just get light. It's all the matter and antimatter
• 39:15
  Speaker 1: annihilates into photons and that's it. And so it could
• 39:19
  Speaker 1: be that these numbers determine the matter antimatter asymmetry, which
• 39:23
  Speaker 1: is why we're made of matter, or you know, other
• 39:26
  Speaker 1: sets of these values, you could end up with the
• 39:27
  Speaker 1: universe made of antimatter that they of course would call matter.
• 39:31
  Speaker 1: And so it's not well understood, but it could certainly
• 39:34
  Speaker 1: influence the nature of the universe.
• 39:36
  Speaker 3: I'll note that as you're talking about these conditions under
• 39:39
  Speaker 3: which we might all be annihilated, you have this weird
• 39:41
  Speaker 3: like sparkle in your eye. But anyway, so just to
• 39:45
  Speaker 3: try to bottom line where we are so far, there
• 39:48
  Speaker 3: is at least twenty six dimensionless values in the equations
• 39:54
  Speaker 3: that govern how the universe works, and they vary in
• 39:58
  Speaker 3: the extent to which we think that they are critical
• 40:01
  Speaker 3: for the universe to work as we know it. So
• 40:04
  Speaker 3: some of these you can tinker with a little bit,
• 40:06
  Speaker 3: maybe you'd still get life. And some of these, if
• 40:09
  Speaker 3: you tinkered with them even a teeny tiny bit, it's
• 40:12
  Speaker 3: hard to imagine that you could ever get life, yes, exactly.
• 40:15
  Speaker 1: And the last one is the cosmological constant. This is
• 40:19
  Speaker 1: a big one. This is the one that determines how
• 40:22
  Speaker 1: fast the universe is accelerating. It's our best explanation for
• 40:26
  Speaker 1: dark matter. You know, we think that space has some
• 40:28
  Speaker 1: inherent potential energy, and according to general relativity, if space
• 40:32
  Speaker 1: has potential energy in it, then you get this repulsive,
• 40:35
  Speaker 1: accelerating expansion in the universe. And so this is very
• 40:39
  Speaker 1: important for the formation of the universe as we know it.
• 40:42
  Speaker 1: If the expansion rate is too large, then the universe
• 40:45
  Speaker 1: starts to tear itself apart before gravity can do its
• 40:48
  Speaker 1: work and form stars and planets. If this number is
• 40:52
  Speaker 1: too small, the universe collapses due to gravity very early
• 40:55
  Speaker 1: on into one mega black hole. And so you can't
• 40:59
  Speaker 1: tweak the cosmos constant very much, which is the source
• 41:02
  Speaker 1: of all the recent consternation. You know, people have been
• 41:04
  Speaker 1: trying to measure this number and finding that, oh, actually,
• 41:07
  Speaker 1: it doesn't make sense to happen be a single number,
• 41:09
  Speaker 1: and it needs to change over time because the structure
• 41:12
  Speaker 1: of the universe is very sensitive to this number. And
• 41:14
  Speaker 1: the more we measure about the evolution of the structure,
• 41:17
  Speaker 1: the more we have questions about whether this number actually
• 41:19
  Speaker 1: is a constant or whatever. But the point is this
• 41:22
  Speaker 1: is a big one. It controls the structure of the
• 41:24
  Speaker 1: universe as we know it. And so, yeah, a lot
• 41:27
  Speaker 1: of these the universe is very sensitive to Some of them.
• 41:29
  Speaker 1: You might be able to fudge a little bit, but
• 41:32
  Speaker 1: we're still faced with these questions like does this mean
• 41:35
  Speaker 1: the universe is fine tuned? We have all these numbers
• 41:37
  Speaker 1: that we don't have predictions for if we change them
• 41:40
  Speaker 1: a little bit, life would be different. What does that
• 41:42
  Speaker 1: really mean? And that's where we get into the philosophy.
• 41:45
  Speaker 3: Yeah, I feel like quite clearly this is where physicists
• 41:48
  Speaker 3: should start talking about the existence of God and stuff.
• 41:51
  Speaker 2: But I don't see that in the outline.
• 41:54
  Speaker 3: And so what what are the philosophical explanations that physicists tackle?
• 41:58
  Speaker 1: So my favorite explot is, Look, we're just not done.
• 42:02
  Speaker 1: There is a theory out there that does explain these things,
• 42:05
  Speaker 1: that tells us why it has to be this way
• 42:07
  Speaker 1: that connects these masses. And maybe that theory has zero
• 42:11
  Speaker 1: or maybe has one parameter. But if we had a
• 42:13
  Speaker 1: deeper insight, or we could crib on alien physics textbooks,
• 42:18
  Speaker 1: you know, or even future humanity that maybe we just
• 42:20
  Speaker 1: have a deeper understanding and the universe has to be
• 42:23
  Speaker 1: this way. We just don't get it yet. That's my
• 42:26
  Speaker 1: favorite explanation because it also inspires more research, you know,
• 42:30
  Speaker 1: it tells us to keep digging, that there are more
• 42:32
  Speaker 1: answers there and if we keep going, we'll figure it out.
• 42:36
  Speaker 1: So that's why I like that explanation, not because I
• 42:38
  Speaker 1: know that it's true or I can argue for it
• 42:41
  Speaker 1: like scientifically, but it's the one that inspires us to
• 42:44
  Speaker 1: keep going, because that's the whole motivation of science. Right,
• 42:46
  Speaker 1: Let's keep trying to understand, let's keep looking for those explanations.
• 42:50
  Speaker 1: We have no reason to believe those explanations exist or
• 42:53
  Speaker 1: that the universe is sensible at some fundamental level. Anyway,
• 42:56
  Speaker 1: I have some sort of operating just on the assumption
• 42:58
  Speaker 1: that it is, and so it's worth well, so far,
• 43:01
  Speaker 1: let's keep going.
• 43:02
  Speaker 3: But I like that explanation because it's actionable. It's like, Okay,
• 43:05
  Speaker 3: we don't know, but let's not give up, let's keep trying.
• 43:07
  Speaker 3: And so all right, so we've got that's explanation one.
• 43:09
  Speaker 3: What's explanation two.
• 43:10
  Speaker 1: Explanation two is that there is no explanation. These are
• 43:13
  Speaker 1: just random, right, and they could have any value, and
• 43:17
  Speaker 1: we happen to live in a universe where these values
• 43:21
  Speaker 1: are the ones that we need for life, and so
• 43:24
  Speaker 1: life evolves according to the laws of physics to fit
• 43:27
  Speaker 1: into it. It sort of shapes life. You know, some
• 43:31
  Speaker 1: other weird form of life couldn't have evolved in these
• 43:33
  Speaker 1: universe because our form of life is very sensitive to
• 43:36
  Speaker 1: the chemistry and the structure of universe and all this
• 43:38
  Speaker 1: kind of stuff. And you know, there's an explanation here
• 43:41
  Speaker 1: that's called the anthropic principle that says that we wouldn't
• 43:44
  Speaker 1: be here if those fine tuned constants weren't fine tuned
• 43:48
  Speaker 1: to the numbers needed for life to be as we
• 43:50
  Speaker 1: know it. So in most of those universes where you
• 43:53
  Speaker 1: change those numbers, you don't get Daniel and Kelly having
• 43:55
  Speaker 1: a podcast conversation about it. You don't get people writing
• 43:58
  Speaker 1: philosophy papers about it. Not a question because we're not
• 44:01
  Speaker 1: there to ask it. And so this sort of says, well, look,
• 44:05
  Speaker 1: this is a big coincidence, but there's no deeper explanation.
• 44:08
  Speaker 3: But so doesn't that kind of depend heavily on what
• 44:13
  Speaker 3: we know? Like how how we understand how things worked out?
• 44:17
  Speaker 3: Like if you tinkered with these values, maybe you wouldn't
• 44:20
  Speaker 3: end up with galaxies, you would end up with like
• 44:23
  Speaker 3: one big flat disc that we all live on or something.
• 44:26
  Speaker 3: And maybe we'd all have tentacles. And how much are
• 44:29
  Speaker 3: we biased by tentacles.
• 44:31
  Speaker 1: A bad outcome or a good outcome? I'm trying to
• 44:34
  Speaker 1: figure that out. Oh, I don't know.
• 44:37
  Speaker 2: I could see it going either way.
• 44:38
  Speaker 1: It's hard to watch cat videos when you only have tentacles.
• 44:41
  Speaker 1: You know. Can you use your suckers to control the phone?
• 44:43
  Speaker 1: I don't know how that works.
• 44:44
  Speaker 3: I mean you can get attachments for your suckers maybe,
• 44:46
  Speaker 3: and that could help you with your phone.
• 44:48
  Speaker 2: But we're getting off topic here.
• 44:51
  Speaker 3: But yeah, but so how I mean, how do we
• 44:53
  Speaker 3: know that the universe couldn't just look so different that
• 44:57
  Speaker 3: it's like beyond our ability to comprehend.
• 44:59
  Speaker 1: Yeah, you're exactly right, and that's another explanation, right, So,
• 45:02
  Speaker 1: wrapping up the anthropic explanation, I agree with you. And
• 45:05
  Speaker 1: the thing I don't like about it is that it
• 45:07
  Speaker 1: tells us to stop looking. It says, look, there are
• 45:09
  Speaker 1: no answers, so don't waste your time, and it can
• 45:13
  Speaker 1: hide real explanations, like there are sometimes real explanations. And
• 45:17
  Speaker 1: if you just say, look, I don't know and just
• 45:20
  Speaker 1: the way it is, and we wouldn't be here to
• 45:23
  Speaker 1: ask these questions otherwise, then it stops you from finding
• 45:25
  Speaker 1: true answers. So I'm not a big fan of the
• 45:27
  Speaker 1: anthropic explanation. And another answer to this question is that
• 45:31
  Speaker 1: we don't know what life would be like in these
• 45:33
  Speaker 1: other scenarios. It's true that if you tweak the fine
• 45:35
  Speaker 1: structure constant, you get very different chemistry, and therefore you
• 45:38
  Speaker 1: would have to have different life, but we don't know
• 45:41
  Speaker 1: what that life would be like, and if that life
• 45:42
  Speaker 1: would also ask this question, and it presumes the structure.
• 45:46
  Speaker 1: This question presumes that like we are some sort of outlier,
• 45:50
  Speaker 1: we're unusual in our complexity and intelligence. It might be
• 45:54
  Speaker 1: that we're kind of simple and boring, and that if
• 45:56
  Speaker 1: you changed one of these fine structured constants or one
• 45:58
  Speaker 1: of the other constants, get a much more interesting universe
• 46:01
  Speaker 1: filled with life. And they're all super intelligent and they
• 46:04
  Speaker 1: figured it out fast and light travel and like we're
• 46:07
  Speaker 1: a bad outcome. We're like, oh boy, you know, I
• 46:10
  Speaker 1: hope we don't get that universe right. And so call
• 46:13
  Speaker 1: comes down to the question you asked earlier, basically, like
• 46:16
  Speaker 1: do aliens have tentacles? We can't imagine life as we
• 46:20
  Speaker 1: don't know it. It's very hard for us to think
• 46:22
  Speaker 1: outside the box. We don't know where the box edges are,
• 46:24
  Speaker 1: what assumptions we're making. The bee don't even realize, and
• 46:28
  Speaker 1: it's very almost impossible to calculate. You might say, well, Daniel,
• 46:31
  Speaker 1: you're a physicist, change the numbers, run the simulations, tell
• 46:35
  Speaker 1: us what those universes are like, right, that involves so
• 46:38
  Speaker 1: much complexity. We can't even tell you, like how stars form.
• 46:42
  Speaker 1: We don't understand the nature of the universe. We have
• 46:44
  Speaker 1: to just go out and look, right. We can't start
• 46:47
  Speaker 1: from these principles and tell you how our universe should
• 46:50
  Speaker 1: look because we can't do the calculations. It's too complicated.
• 46:53
  Speaker 1: You know, we can't like predict what chicken soup taste
• 46:56
  Speaker 1: like from particle physics, right, that's too many numbers. We
• 47:00
  Speaker 1: can't predict the weather, we don't understand turbulence, and so
• 47:03
  Speaker 1: I can't then change these numbers and tell you what
• 47:05
  Speaker 1: the universe would look like. It's too complicated. We're not
• 47:08
  Speaker 1: capable of doing that. So we don't know, right, And
• 47:12
  Speaker 1: you're right that it could be that in most settings
• 47:14
  Speaker 1: of these numbers we get interesting stuff life and intelligence
• 47:17
  Speaker 1: and happiness and parasites and tentacles, good or bad. So yeah,
• 47:21
  Speaker 1: we don't know, and I think that's what you were asking,
• 47:24
  Speaker 1: and so then let's just wrap up. The last possible
• 47:26
  Speaker 1: answer is like, well, maybe they are fine tuned, you know,
• 47:29
  Speaker 1: maybe we're living in a simulation, or God exists and
• 47:31
  Speaker 1: they have set these numbers to be the way they are,
• 47:34
  Speaker 1: and discovering these things means that we're special. And I
• 47:37
  Speaker 1: don't like that answer because it makes us sound special.
• 47:39
  Speaker 1: And anything that makes us sound special is too tempting
• 47:42
  Speaker 1: and too seductive and makes me very skeptical. I'm with
• 47:46
  Speaker 1: you there, all right, So thanks everyone for coming along
• 47:48
  Speaker 1: on this ride between physics and philosophy exploring the nature
• 47:51
  Speaker 1: of the universe, what it all means, what we've learned,
• 47:53
  Speaker 1: and what we have yet to figure out.
• 47:55
  Speaker 2: See y'all next time.
• 48:03
  Speaker 3: Daniel and Kelly's Extraordinary Universe is produced by iHeartRadio.
• 48:07
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• 48:09
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• 48:12
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• 48:17
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