Daniel and Jorge Explain the UniverseDaniel and Jorge talk about the numbers that control everything, and the number of those numbers!
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I'm David Ego from the podcast Inner Cosmos, which recently hit the number one science podcast in America. I mean neuroscientists at Stanford, and I've spent my career exploring the three pound universe in our heads. Join me weekly to explore the relationship between your brain and your life, because the more we know about what's running under the hood, better we can steer our lives. Listen to Inner Cosmos with David Eagleman on the iHeartRadio app, Apple Podcasts or wherever you get your.
Podcasts, Hey or Hey. What's your favorite number?
Well?
I like all numbers. I try not to discriminate between numbers, but you know, I think since I was little, I've always liked the number four.
The number four. Why is that that's a lot less than the number of bananas in a bunch for example.
Well, I think I liked it because when I was literally it kind of blew my mind that, you know, four was two plus two and it was two times two and it was two to THEO, and so I just thought that was.
Like amazing, that is pretty tooey twoy.
What about you? What is your favorite number?
Oh, that's easy. It's got to be forty two, because forty two it's the answer to everything.
So maybe that should be our podcast title forty two explains the universe. Forget about those two guys.
I guess we could stretch that to forty five minutes, right, They answered, everything's just forty two.
Every episode would be forty two minutes.
Long, and we'd have forty two good.
Jokes, and they would cancel it after forty two episodes.
And I hope you'd have forty two million listeners.
Hi. I'm Morgan. I'm a cartoonists and the creator of PhD Comics. Hi.
I'm Daniel Whitson. I'm a particle physicist, and I'm a co author of our book, We Have No Idea, a Guide to the Known Universe, in which we talk about all the amazing open mysteries of the universe, all the things science has figured out, and all the things science has not figured out.
It's right, there are a lot of books out there about all the things we know about the universe, but ours is about all the things we don't know, and believe it or not, we fill the whole book with things we don't know.
And it's not just what Jorge and I don't know about the universe, which is a lot, but it's about what science in general. We try to speak for humanity and bring you to the forefront of human knowledge to delve into the deepest questions about the biggest things in the universe, i e. The entire universe.
Yeah, because it turns out there's a lot that scientists don't know about this great, big and complex and beautiful universe, including sometimes things about numbers.
Yeah, because one way to tear the universe apart is to sort of take it apart literally physically and say I am made of bits, what are those bits made out of? What are those bits made out of? And then you can drill down to the sort of the core bit, the fundamental element of the universe. But there's another way to look at the universe, another way to think about it, and that's more mathematical, to think about what are the basic numbers? Like if you had a theory of the universe, what numbers would appear in it?
Yeah, Like if you had an equation that just describes everything in the universe, would it have any numbers in it or not or just symbols or concepts?
And what would those numbers be, right? And why would they be those numbers and not other numbers? I like to think about somebody sitting at a control panel for the universe. Maybe the universe is a simulation and somebody up there has knobs and they're twiddling it. And you know, as you change those knobs, the universe looks different. And so our job is to measure the value of those knobs and then to ask, like, why this value not something else? Could have been anything? Are these two knobs actually connected? Is there just one big knob?
Yeah? Like, why are our podcasts always about forty five minutes? Is there a universe in which our podcasts are shorter or longer?
That's as long as we can be funny for After that, it just trails off.
Yeah. In fact, even the number of knobs that the universe might have would be significant, Like if the universe had seven knobs versus three knobs, that would be pretty significant and would tell you a lot about whoever or whatever made this universe.
Yeah, And this is a deep question, not just of science, but also of philosophy. If you think the goal of science is to reveal the truth about the universe, then you have to be prepared to answer the question what does that truth mean or does it inform us? Right? If you're going to ask a question, you better know how to interpret the answer, which is, of course the underlying joke behind forty two. Those folks that build a huge planet sized computer to figure out the answer to life, the universe and everything and then have no idea what it means.
You think they know there's a universe out there in which there Douglas Adam wrote the same book but used to number forty one or forty seven, and their jokes are all about that number.
I don't know. I'd love to read an interview with him, but how he chose that number because it's achieved such cultural prominence. They did a survey of like all the numbers that appear in Python code on GitHub, and they plotted the distribution, and there's a big spike at forty two. People just like use it as an arbitrary number all the time.
Maybe it's not a coincidence, or you know, maybe it is a basic number that just pops up.
It's the number of neurons that work in an average person's head. Maybe.
Yeah. So this is an interesting concept to think about the constants of the universe. And so today on the episode, we'll be asking the question, what are the basic constants of the universe and are they even constant?
And why do physicists keep calling things constant when they don't know if they are?
Why can they be consistent about it.
Or at least conscientious?
Right, it seems like a constant annoyance to have to recalibrate my meaning of words when I talk to physicists.
Yeah, and I don't think it's even a conscious thing. You know, we talk about constants, we really mean numbers. But then there's a question, you know, are these numbers is actually constant? Are they changing? How could we tell if they were changing? What if two of them are changing at the same time, would we even notice? These are really fun, interesting questions, and they really go deep into the nature of the universe itself. You know, we have these basic laws that describe sort of how things interact. But then there just seem to be numbers that determine, you know, the relative power, Like why is the gravitational force so much weaker than the other forces? You know, why are stars so far apart? There has to be something to set these scales to determine why the universe turned out this way and not other ways.
Daniel, I feel like this maybe this question assumes that there are basic constants in the universe. Do we know for sure that there are constants in the universe? Is it maybe just something that we haven't discovered or something.
Well, we have constants that we've measured, and we do not know how to derive them, and we'll get into the definition of what it means to be a basic constant. There used to be more, right, And sometimes we discover, oh, this thing that we thought was fundamental turns out to just be a combination of these other numbers, and so we.
Needed sometimes like a basic number is just a combination of other numbers.
Just a combination of other numbers. So what we're looking for is the minimal set, right, We want the smallest number of constants, just like we want the smallest number of physical laws. We don't want to describe five thousand forces. We want to have one force that describes everything. All the features of electromagnetism, we've tied them up so nicely into a few equations with a small number of numbers in them. So we're always working to reduce the number of ideas and then the number of parameters of those ideas.
And we're not talking about things like pi or e, right, which are sort of mathematical or geometric constants in the universe. We're talking more about physical constants, right, Yeah.
Things that you have to measure, right, not just geometrical stuff that you could calculate without having access to the universe. Things you have to go out and actually measure.
Because things like pi and e are like sort of like basic constants in mathematics, you know, which is sort of abstract. Where we're talking about the constants in the universe that seem to be there that sort of define how things work.
Yes, things that if you change them, the nature of the universe would change. Things would be different. You wouldn't have chemistry anymore, or you wouldn't have stars, or you'd have more stars, or you know, different forces would be more powerful, or we'd be made out of different kinds of particles, you know, this kind of stuff that fundamentally change our description of the universe. But you're right, we don't know how many constants we actually need right now. We need quite a few to describe the number. But if we had the ultimate theory, how many constants would it have in it? Maybe one, maybe five, maybe ten.
Maybe you'd have pi number of consonants.
What does that even mean?
It means I just blew your mind.
Well, you know, we talked about how in Stephen Wolfram's world there are two point seven dimensions, so maybe you can have three point one four numbers.
Me and Stephen Wolfram are at the forefront.
Well, I pulled our listeners who are willing to participate in virtual person on this Street interviews and ask them this question about the basic constants of the universe. And if you like to participate in these virtual person on the street interviews, just write to us to questions at Daniel and Jorge dot com and you can also display your knowledge or lack thereof on the podcast.
So think about it for a second. If someone asks you, what are the basic constants of the universe, what would you answer? Here's what people had to say this one.
It's easy. I don't know the.
Gravitational constant and the Avogadro constant.
Other than light speed, I would say that pie and oiler's number are also constants of the universe.
I think it's just like things that we've measured.
Well, I don't know.
Well, they gave us one hint of the speed of light, but I think based on other podcasts that I've listened to and learned from them. I think entropy might be a constant, gravity is a constant, and my last guest would be maybe thermodynamics.
I think physics, the you know, the standard model of physics, as we know what is constant, right.
See equals one, h equals one.
What else he calls one.
Pi is Avigadro's number from ancient chemistry, lettles Plank, mass, plank length, Botzman's constant reintroprey. I think there was a Danuine why I explain the universe episode onto my dynamics. I mentioned that the gravitational constant, uh elementary charge.
The exponent of the radius the radius squared in Gaussian formula, and probably, I guess also called Maxwell's equations, death and taxes.
And there's also the charge of an electron, and maybe the mass of the fundamental particles that have mass.
I know there are several constants in the universe, however I can't remember most of them. The ones I do remember are the speed of light, the gravitational constant, and Plank's constant.
All right, some pretty good answers, man. Some of these I'd never even heard of.
Death and taxes. You never heard it before, you know your past leadline?
What are taxes? I don't understand? Is that why I keep getting letters in the mill?
Do you live in the sovereign state of Jorge.
Maybe I'll ask my accountant. But you know, a lot of people are talking about real physical things like light speed and soul and entropy and the speed of light.
Yeah, people are saying things that are sort of parameters of physical theories. But these are not actually the basic constants that physicists talk about. Oh, the speed of light, planks constant, the gravitational constant. They seem basic, but they're actually susceptible to sort of arbitrary definitions because they're expressed in terms of human units.
Oh, I see, meaning that, for example, the speed of light could be a constant, but the constant wouldn't be three hundred thousand meters per second. Yeah, because that's subject to units.
Yeah, so let's get into that, Like, what do we mean by a basic physical constant? And one important thing is that it should be dimension lists, like, it shouldn't have units. It shouldn't be expressed in terms of like furlongs per fortnite, you know, or gallons per second or something. It should just be a pure number.
Like a pure number without unit, without units, like pie is a number without unit.
Pi is a number without units. But it's not a physical constant because it doesn't need to be measured with experiment, right, you can do it in a simulation or on the computer or something. But we're talking about physical constants that have to be measured, and those are things like we'll get into the whole list, but you know, things like the mass of a particle relative to the mass of another particle.
Like ratios, like ratios, which wouldn't change if you suddenly change what it means, if you change, like from English units to international unit exactly.
And there's two important reasons why you have to use numbers without units. The first is you want to look at the number and know what it means, and it doesn't mean anything if it's relative to some stick in Paris, or you know the length of somebody's foot one hundred years ago. Right. If you're interested in knowing a number, then you don't want to express it in terms of human units because it's totally arbitrary, and you could change that number. It could be one hundred and eighty six thousand miles per second or three times ten dy meters per second. Like, you can't look at the number and say it means anything if it's defined relative to something totally arbitrary.
You need a basic constant to feel classic, like not subject to the whims of man and what they consider a footing.
That's right, And it's more than just you know, having an arbitrary standard. You also need the basic constants to be dimensionless so that you can tell if they're changing. If they're changing, then you can tell what's changing.
I see, you don't want a meter to be you know, the length of a length of putty, because the length of putty might change.
That's right, of the length of putty might change. But also like you know, say you're interested in the question, you know, does the speed of light change? Right? This is a question you see in science all the time. It turns out it doesn't actually have the meaning that you think it does when you drill down into it, because it's so subject to human conventions. It depends on how you're defining units. And in fact, in nineteen eighty three, we changed what we meant by the speed of light.
Really, yeah, the speed of light changed in nineteen eighty three.
In nineteen eighty three. After nineteen eighty three, it doesn't make any sense to measure the speed of light. And that's because before nineteen eighty three, we defined the meter to be the length of some rod in Paris, and the second to be, you know, ten trillion oscillations of caesium one thirty three. So we had the meter and we had the second, and then you could go out. You could measure the speed of light. You could say how far did a beam of light go in ten seconds? And it will measure that distance with my ruler from Paris or my copy of it and get a number. Cool.
But then in nineteen eighty three.
A bunch of people got together and decided that we'll keep the second as like, you know, the number of oscillations of CZM one thirty three. But then we're going to fix the speed of light. We're going to define it to be something. So we just pick on number. We say it's two point nine to nine whatever times ten of the eight meters per second. Okay, So once you do that, you don't have to define the meter anymore. It's already defined by the other constants. Right, You've got time, and you've got speed because you have the speed of light. So a meter then is just defined as how far light goes in a certain tiny fraction of a second. So the meter is now defined to be a fraction of a light second. Right. Light seconds are the reference for distance now, the fundamental way we measure distance to the universe instead of that crazy rod in Paris. And we're used to measuring distances in terms of time, like a light year is a unit for distance to the stars. Right, that's familiar. Well, a meter is now just a tiny bit of a light second. It's not defined anymore by a rod in Paris. It's measured by how far light goes in that tiny slice of a second. It Yeah, we flipped it. And so now you ask, well a meter is now measured instead of the speed of light being measured.
Isn't even time variable? You know, according to relativity? You know, how close you are to a gravitational object, you know, like, isn't even the oscillations of caesium one point thirty three also maybe subject to you know, relativity.
Yeah, absolutely, And that's why you want to focus on dimensionless constants. Right, But the point here, the point I was trying to make is that, like you can't even tell in this example, if the speed of light is changing, or you know, the length scale of the universe itself is changing. It depends on if you're defining the speed of light to be fixed and measuring the meter relative to that, or you're defining the meter to be fixed and measuring the speed of light relative to that. So the way to figure out if the universe is changing, if the physics of the universe are changing in time or static, which is really what we're trying to get at when we measure these numbers and see if they're changing, is to define only dimensionless numbers, numbers without any units, because they're not subject to any of these totally arbitrary definitions.
All right. So that's kind of what a basic constant is. It's a number that defines some kind of ratio about physical things in the universe, which may be there at the end when we discover the equation of the universe.
Yeah, and I really like thinking about this this way, like thinking about measuring distances in terms of times, you know, it makes a lot of sense when you think about, you know, measuring distances to stars in terms of the speed of light. And it just shows you that all these numbers that we measure, like the speed of light, they're really just ways to convert between meters and seconds. They're just like translations between arbitrary human conventions. So they're not actually fundamental. The things that are fundamental are things that we'll talk about in a little bit. But yes, we're looking for sort of a minimal list of dimensionless quantities which would change the world if they changed, right.
So let's maybe get into what is that minimal list of basic constants in the universe and what we know about them so far. But first let's take a quick break.
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All right, Daniel, we're talking about this constant topic that keeps coming up in physics, which is constants and what is and what isn't changing about the universe? And are there constants in the basic equations of the universe? And there are how many? And what are they? And let's just get out of the way. It's probably forty two, but you know, we still have to check.
Well, forty two would be wonderful because it'd be kind of a good joke, but it would also be kind of disappointing because forty two is a big number.
You're never happy, Daniel, I'm never happy. All answers have both good and bad consequences.
I'm constantly disappointed.
Now.
What we're looking for, what we'd love is to have a small number of constants, because that would tell us that we're close, right, like the way we're trying to boil down the universe to one particle and one rule that tells you something deep about the universe. If your list of particles and your list of rules about how they interact is fifty pages long, it tells you you're not really close to the answer. So we want to get down to a small number of constants because we think those are probably fundamental. We want to look at those and say, hmm, you know, the theory of the universe has the number seven in it. What does that mean? Why is the universe seven ish? You know, why seven and not six? And we're looking for that moment where we get to ask that philosophical question about the universe. And you can't really do that if you suspect that your list of numbers is sort of an artifact of not having gotten there yet.
Do you think maybe the last number in the universe. Do you think it's an integer like a whole number, or do you think it's gonna be some weird numbers?
I don't know. You know a lot of particle theorists like numbers that are close to one. They think all the numbers and there should just be one.
They're like, we got one, we don't need anymore.
Yeah, And they wonder when they find a number that's not one. You know, they see things like, well, why is electromagnetism so much stronger than the weak force? And why is it so much stronger than gravity? And they have these numbers that reflect the relative strength of those forces, and they wonder, why is it not one? They look for symmetry and simplicity. So anytime they see a number that's not one, they get suspicious because they think maybe there's a reason, maybe there's a simpler way to express things, where all these things are just one.
And that's how they conduct their social life too. They're like, there's more than one people hear, what's going on? This is not what I ordered.
They have one friend at a time, you know.
One friend at a time, like everyone else is. Apparently, that's right.
So we are not there yet. We are not down to one constant. In fact, we sort of have an embarrassing number of constants so far. We have twenty six basic constants of the unit.
Twenty six. Oh man, that seems like a significant number in itself.
Twenty six seems like a special number because it's what two times thirteen.
Yeah, and thirteen is a prime number.
Yeah, But that means twenty six isn't right, so it's much less exciting.
All right, Well, what do you mean? We have twenty six constants? Meaning in all of physics and all the equations that we currently have about the universe, there are twenty six numbers that you can't break down anymore or that are not related to each other.
If you wrote down the whole standard model of particle physics, and you have to put all the numbers into all the four strengths and all the mass particles and all the way things change to each other, there are a lot of numbers in there, like thousands of thousands of numbers, but most of those numbers come from other numbers, Like how long does the muon live? That's a number, but you can calculate that based on the muon mass and the electron mass and the four strength between them. And so if you boil it down to the minimal set of numbers that you need to define all those other numbers, right, the ones that, according to our understanding currently are the knobs of the universe, Then you get twenty six.
If I toss a ball up into the air and catch it, you can maybe derive that time using other numbers.
Yeah, exactly. If I know the mass of the electron relative to the gravitational constant and stuff like that, I can derive most of physics from just a few numbers.
All right, Well, then let's talk numbers. Daniel, what are these twenty six? Break it down for us, what are these twenty six apparently basic constants of the universe that we have right now.
Yeah, So there are sort of three categories. One is like the strength of forces, another is the masses of particles and how they mix, and then there's the cosmological constant in its own category. The first ones are really really interesting, and these are the fourth ones. The most important one, the one that you hear about a lot and I think reveals a lot about what we mean by a dimensionless physical constant. Is this one called the fine structure constant.
Fine structure constant, all right, I'm intrigued.
It's a weird name. It's called the fine structure constant because it comes from when people were trying to understand the nature of the atom and the structure of the spectra that it emitted. And so what it really reveals is sort of the strength of the electromagnetic force. And so this number here tells you about the power of electromagnetism as probed by the internals of the atom, but it turns out to be a fundamental number of the universe.
What does it mean? Is it like how how attracted an electron is to a proton or something like that.
Yeah, it's something like the probability for an electron to emit a photon, and that number is a vacuum or well, electrons only emit photons inside electromagnetic fields, of course, and that number.
Everyone knows that.
And that number it turns out to be one over one thirty seven.
What exactly one over one thirty not exactly.
For a long time people thought it was exactly one over one thirty seven, and there was a big mystery in physics like why that number. And Richard Fineman likes to say that if you were a physicist and you were ever like stranded in a foreign city, you just hold up a piece of cardboard that says one over one thirty seven on it, and some other physicists will see that and know that you're a physicist and come rescuing.
It's like a code. I'm not sure if you're stranded in a city, you want what do you need as a physicist to rescue you? But you know, let's leave that aside and all right, So that one of these constants of the universe is kind of how like the an electron is to emit a photon.
Yeah, it's like the probability for an electron to emit a photon, and it's it's actually expressed in terms of other numbers that you will find familiar, Like the way you calculated is the charge of the electron squared divided by planks constant hbar times the speed of light, and so it has all these other familiar things built into it. But when you put all those things together, the units cancel, Like you get up a number that has no units in it, and that means something really really deep. What do you mean deep? What I mean is that it tells you something about the importance of the speed of light. It tells you, for example, that the speed of light is not actually a fundamental constant. That if you changed the speed of light, but then you also change these other numbers inside the find structure constant. To keep the find structure constant the same, you would not be able to tell the difference.
The universe would work the same way.
As long as you keep these numbers the same. Then you can change the speed of light and the strength of electromagnetic force, and you could not do an experiment that showed that anything had changed.
Like it doesn't have any consequences anywhere else in the universe. That's right, if you change the speed of light, Wooden, you we noticed like, oh, it takes longer for light to come to us from the sun.
If you only change the speed of light, which means that you're effectively changing the fine structure constant, then yes. But if you change the speed of light and you also changed like the charge of the electron or planks constant, or you manipulated these things in such a way to keep the fine structure constant the ratio of these things the same, then you could not tell the difference. It's like, okay, distance now means something different. But you know the electromagnetic force is now stronger. So what are you using to measure distance. You're using, you know, the photons emitted by electrons or something. So you cannot devise an experiment that is sensitive to changes of just planks constant or just the speed of light if you keep the fine structure constant fixed.
I see, somebody could change these things and nobody in the universe would even notice.
Nobody in the universe could even notice, you know, imagine a simpler example, like.
I feel like, I feel like this is a conspiracy. Somedly I feel nervous.
It's about our world is relative to our units. Imagine, for example, somebody came in and changed the universe so that now every distance was doubled, the distance between all particles was doubled. Suddenly, could you notice?
Well?
Sure, but not if then they also increase the power of all the forces, so the things didn't seem as far, and they increased the maximum speed you could go. Right, then it would take you just as long to get from here to work, and your rulers would also change, right, so you would say, oh, I'm still the same high as that was yesterday.
It's like if somebody just scaled up the universe, but they made sure that everything worked the same, would we even notice exactly? They could somebody bottle up the whole universe into a little bottle and then made sure that all the knobs were also changed that we wouldn't notice the difference. It could happen.
It could happen, And that's why we focus on these dimensionless quantities, because you can't change those without changing the physics. You can change the things that they express. You know, this fine structure constant. You can change the dimension full of the unit quantities inside them. But if you change these fine structure constants, then there's no way to hide.
That they do seem like basic constants of the universe.
They do.
In fact, it's like a basic ratio of the universe, you know, just like pies, like the ratio of you know, the ratus and this circumference. This is like the basic ratio of matter and how it moves in the world.
And now I'm going to disappoint you because it turns out it's not actually constant. No, no, but it's not that it's not constant in time. It's really weird and we're going to dig into this next week when you talk about renormalization. But it depends on how fast you're going when you measure it.
Isn't that what I brought up earlier, like its relativity special relativity.
Yeah, it's actually it's more about the momentum you have relative to the thing that you're measuring, rather than actual velocity.
Right, you just can't admit I was right.
You're always right or hey, that's one constant of the.
Universe relatively speaking. All right, So that's a good flavor. I think that gives us a good flavor for what these constants mean. And it blows my mind that there are twenty six of these that we think we know about, twenty six things it can't change or could change internally, but we wouldn't notice. Yeah, all right, Well, let's get into the other kinds of constant in the universe that we have and what they mean, and whether or not there are more of them. But first, let's take another quick break.
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Hi, I'm David Eagleman from the podcast Inner Cosmos, which recently hit the number one science podcast in America. I'm a neuroscientists at Stanford, and I've spent my career exploring the three pound universe in our heads.
We're looking at a whole new.
Series of episodes this season to understand why and how our lives look the way they do. Why does your memory drift so much? Why is it so hard to keep a secret? When should you not trust your intuition? Why do brains so easily fall for magic tricks? And why do they love conspiracy theories. I'm hitting these questions and hundreds more because the more we know about what's running under the hood, the better we can steer our lives. Join me weekly to explore the relationship between your brain and your life by digging into unexpected questions The inner cosmos with Savid Eagleman on the iHeartRadio app, Apple Podcasts or wherever you get your podcasts.
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All right, then, we're talking about the basic constants of the universe that are not constants, but we think are sort of constants consistently.
Well, that's one thing we don't know, right, we measure this thing, We've measured it a lot of different times, over many different years, and we do not see it changing in time, and so we say, maybe this is constant. And it's just like the rest of science. We have no reason to believe that you do an experiment today and you do experiment in a week, you should get the same answer in the same conditions. But it seems to be true. We live in an empirical universe where you can repeat experiments, and it seems like these numbers are fixed. We may discover, if we keep doing science over a thousand years or a million years, that they're very slowly varying, and that would be fascinating. But so far they do seem constant.
All right. And so you're telling me that physicists have twenty six of these constants, and some of them are related to how particles interact with each other and how attracted they are to each other, but some of them are also related to their masses. Yeah, so tell me about this.
Yeah, So we have two that determine the forces. One is the fine structure constant that tells you about electromagnetism. There's a second one which tells you about the strong nuclear force. But then most of these constants actually relate to the particles, and that's because we just don't know why the particle masses are what they are. Like, we have twelve matter particles that make up the Standard model. There are six kinds of quarks up down, charm strange top bottom. Those are six different particles with six different masses. And then there's six leptons, electrons, muons, towels, and they are three neutrinos. So those are twelve particles and we do not know why they have the masses they do. We can't predict it, we can't calculate it. We don't even see a pattern, and so we just have to put one parameter, one dimension, this constant for each one.
You wish they were related, but so far they don't seem to be.
Yeah, we wish that, like you know, the muon was twice the mass of the electron and the towel four times the mass, or there was some relationship so that you could only fix one number that would determine all the rest of them, and also that would give us some insight to like why are there these other particles and why are they heavier and stuff like that, But we see no pattern at all. There's a huge range. The electron is super duper light, the neutrinos are even lighter. The top quark is like enormously heavy relative to all the other ones. So there are some very general rough patterns, but really nothing we can put our finger on.
So it's the masses of these particles. And I guess the question is how do you measure these masses? Is it like how much they weigh when you put them on a scale in Paris, or you know, is it more like if you push a Tauel particle, how much does it move? What do you call it? The mass of these particles?
Yeah, so here we're talking about the rest mass, right, which means how much energy it has essentially when it's at rest, when you're in its reference frame. And it's hard to measure because particles are very very small and their masses are very very light. And so what we do instead is we wait for one of these things to decay, for example, and we measure the energy of the particles that come out. So if a massive particle turns into massless particles. Then the mass of the original particle gets turned into energy of those massless particles. We measure those energies like of photons, et cetera, then we can measure the mass of the original particle, and so we can do things like that, but it gets harder for particles that don't do that, like the electron's stable. So there you have to do things like put it in a magnetic field and see how much it bends, because that's partially determined by its mass.
I guess it would be rude just to ask them what they're mask.
They don't like to talk about it constant, but they have to be dimensionless numbers. And so what you could do is because I'm going to fix the mass of the electron, and I'm gonna measure everything relative to the mass of the electron. But then the electron mass then is still a dimension full number. And so what we do is we set all these things relative to the gravitational constant big G, which has the same units of mass, and so all these things are relative to big G.
Big G meaning like nine point eight meters per second square.
No, that's little G. Little G is lit G.
Is G but just you say it louder.
Little G is the force of gravity at the surface of the Earth, right, And that's a number that's important to us and relevant, but definitely not a constant of the universe. It just depends on the size of the Earth and how much mass it is and this kind of stuff. Big G is the number that goes inside Newton's equation and then later also in Einstein's field equations for gravity that determines the strength of the gravitational force.
Okay, it's more basic.
It's more basic, yeah, and it should be true all over the universe. And so we measure the mass of these particles relative to that because usually what you're interested in is actually the ratio of inertial mass to forces, right, like how much gravity are you putting on this thing? How much is it going to accelerate? That depends on how much mass it has, And so we measure these things relative to big G also to keep them dimensionless.
And so it seems that we have twelve particles and their masses. That seems to be basic about d universe. And are these constants sort of like define structure constant where I could you know, change the mass of an electron, and I wouldn't notice.
No, if you change the fine structure constant, you would definitely notice. But if you change one of the numbers inside of it, you might not notice. So as long as it's a constant, then we would have noticed. Yeah. And so if you change the mass of the electron, for example, and made it heavier than the muon, then a lot of things would change, because then the electron wouldn't be stable anymore. It could decay into muons. And then maybe our atoms would we have muons in them instead of electrons, right, we'd be muonic matter instead of electronic matter.
But I guess what you're saying is that the speed of light could change. But as long as you change everything else, we wouldn't notice. And as long as you also don't change the masses of the particles.
Yeah, but if you change these masses of the particles relative to the gravitational constant, you'll definitely notice, And especially if you change their relative orders, you know, because there's a hierarchy there, and if you change those things then we will definitely notice. It would change the way physics and chemistry works.
All right, Okay, we have twenty six constants. Two of them are about the forces of the universe, twelve are about the masses of the particles, and some of them are also sort of related to how particles mix together. Right, and then we have the cosmological constants, which we talked about in a previous episode.
Yeah, and so all the other ones relate to the particles and how they mix and all that stuff. There's three more for the force particles, Higgs, W and Z, and then eight for how the particles turn into each other and how often that happens. But then you're right, the big one, the one at the end, is the cosmological constant. That's the one that tells us how fast the expansion of the universe is accelerating, or if it's accelerating at all, And it determines like the overall shape of the universe.
But you guys, don't go in between here. It's either about little tiny particles or the entire universe.
It turns out little tiny particles determine the entire universe.
Do you think maybe the cosmological constant is related to something about particles?
Be right, People have tried to calculate it. They say, let's try to predict the cosmological constant. If it's in fact just the energy of empty space, like the vacuum of empty space. If it comes, for example, from the Higgs Boson field, then we should be able to calculate it. And they've tried. But the number they get is different from the number we measure by ten to one hundred and twenty. So we're not even close. Yeah, we're not even close to getting that one right, but we'd love to. You're right, we'd love to be able to derive this number from the other numbers, because then we could take it off our list and we'd be down to a thin and trim twenty five numbers.
And you would make a little bit of progress in deconstant defying the universe. Yeah, all right, Well we add there are twenty six right now that physicists can't break down anymore. And is that it? Do you think maybe there are more? Do you think there should be less? Are you guys aiming to collect more or to you know, do some spring cleaning and get rid of some of these.
I think there should definitely be a fewer, right, we should have one number, maybe maybe even zero. I'd love a theory of the universe that has narrow numbers.
Yeah, yeah, well zero numbers in terms of physics. But maybe like if you can get it to come down to a mathematical constant, then that would be cool, that's what you mean.
Right, Yeah, maybe you could have pi and e and i and there. It'd be cool if there are no physical parameters in the fundamental theory. But we're sort of working in the other direction right now, Like, if anything, we're moving in the direction of adding more numbers. Because this theory we've been talking about, the standard model that describes the universe, we know, doesn't actually describe everything in the universe, and so as we add to it to describe those other bits, we're just figuring out that we're going to need more numbers.
Yeah, because it turns out that apparently the standard model only covers about five percent of the entire universe, right.
Yeah, And you know, it's a staggering achievement so far, but there's a lot of stuff out there it does not describe. And so what about dark matter, for example, if dark matter is fifty kinds of particles and we don't understand why there are fifty and why they all have different masses, Boom that's fifty more numbers right there.
Maybe could have one number, or I wonder if it could help you cancel some of your numbers.
Dark matter has the same structure as normal matter, And now we understand the masses because we see more of the pattern and it reveals itself and we get some insights and it helps us figure it out. That's why we're always struggling to attack the parts of the universe we don't understand, because they could be the puzzle piece that lets us see the whole picture.
And so, yeah, there could be more out there, because there's a lot of the universe we don't know about. And you're also telling me that they're not really maybe even constants, like maybe the mass of the electron could be changing. Is that possible, or you know, this fine structure constant could also be different, not just in time, but in different parts of the universe.
Yeah, we don't know if these things are constant in space and in time. It's sort of like a hypothesis. It's the simplest description so far, because we haven't seen them change and they seem really basic and fundamental, but because we don't know where they come from and why they're important why we have this set not a smaller set. We can't say anything about whether they really are consonant. It's just an observation. It's like if you live in la and you go outside and you're like, hey, every day is sunny. Well, that doesn't mean it's gonna be sunny every day. There might be a reason why it's sunny or in La than it is in New York, but unless you understand the reason for it, you can't really make an accurate prediction. But you know, I like looking forward to the end days when we have that theory and we're looking at it and we're asking questions about what those numbers mean. So I went around and I did a little informal survey in my department. I asked some of the particle theorists. I said, how many numbers do you expect to see in a theory of everything?
Expect to be or want there to be?
I think, I think, isn't it to say it seems like a biased you know, you're asking whether they expect to be disappointed?
Essentially, yeah, kind of. So what did they say? How many numbers did they predict our final theory of the universe will have.
I was surprised. I was expecting them to say one number, and that numbers should be one or close to.
One, one number, one quantity.
Yeah exactly, But they really didn't know. They said, you know, it could be one number, could be seven numbers. You know, they expected to be smallish, you know, maybe less than ten numbers, but they wouldn't give a firm prediction. And then I asked them, well, what do you expect those numbers to look like? Like, should they be huge numbers or small numbers? Should they all be close to one and one of them? A friend of mine, Tim Taits, would have blew my mind, and he said, it doesn't really matter if it's close to one, because close to one is just relative to the integers. And who knows if like equally spaced numbers one unit apart means anything anyway. So he's like thinking about, like whether integers are a kind of unit?
What?
Yeah, exactly, questioning the nature of numbers themselves.
Yes, yes, And you know, it doesn't even make sense to have mathematics in terms of equally spaced numbers, because you know, the numbers are all there. Just declaring these equally spaced numbers to be meaningful. You know, it's sort of a human convention.
Let's just throw everything out the door, Daniel, numbers don't mean anything. Distance the word constantly. Yeah.
Well, that's why we try to drill down, because we try to peel away the human bias and look at the universe the way it actually is, which is why you know, I like stories about alien scientists where the aliens don't have differentiated bodies. They're like part of some larger mass, and so they never come up with this idea of integers because they never count like me and you and indistinct objects, and they aren't linked to this kind of assumption in their mathematics, and that makes them think differently about the universe. And that's what we're trying to do here, not specifically meet those weird aliens, but get out of our human bias and think about the universe as close to objectively as we can.
Yeah.
I think the lesson here is don't go to a physics theorist if you want the concept simplified.
That's what I'm here for. I'm trying to filter the physics theory for everybody.
All right, Well, that was a pretty cool discussion. I feel like It's amazing to think that there are constans that you know, kind of define our universe, and that maybe in another universe those numbers are different and they're having different discussions.
About the whole thing. Yeah, and it could be that we get down to the theory of everything and it has a few numbers in it, and we wonder, like, why those numbers, And you know, it could be that those numbers are just an accident, that there are zillions of universes and they're all set randomly, or it could be that, you know, they were set for some other reason, or it could be that they could only be those numbers. It'll be a fascinating moment when if we finally get.
There, there could be no answer.
You are preparing to be disappointed. I'm always looking forward to the future of the universe, expecting it to be chock full of insights and discoveries and mind blowing revelations. That's why I'm helping out.
You're a constant optimistic.
Yeah, exactly. So far, I've revealed exactly zero truth about the universe in my professional career, but I am optimist.
Hey, zero is a basic constant in the universe. You know, Douglas Adam would be proud.
To zero what I've accomplished today the number of pairs of pants I put on.
Well, we hope you guys enjoyed that. Thank you for joining us.
And think about whether the universe around you is constant and what that means.
See you next time.
Thanks for listening and remember that Daniel and Jorge explain the universe is a production of iHeartRadio. For more podcasts from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows. When you pop a piece of cheese into your mouth, you're probably not thinking about the environmental impact. But the people in the dairy industry are. That's why they're working hard every day to find new ways to reduce waste, conserve natural resources, and drive down greenhouse gas emissions. How is us dairy tackling greenhouse gases? Many farms use anaerobic digestors to turn them thing for manure into renewable energy that can power farms, towns, and electric cars. Visit you asdairy dot COM's Last Sustainability to learn more.
Hi, I'm David Eagleman from the podcast Inner Cosmos, which recently hit the number one science podcast in America. I mean neuroscientists at Stanford and I've spent my career exploring the three pound universe in our heads. Join me weekly to explore the relationship between your brain and your life, because the more we know about what's running under the hood, that or we can steer our lives. Listen to Inner Cosmos with David Eagleman on the iHeartRadio app, Apple Podcasts, or wherever you get your podcasts.
Parents looking for a screen free, fun and engaging way to teach your kids the Bible. As a mom, I was looking for the same thing, so I created Kids' Bible Stories podcast. Thousands of families are raving about it, and kids actually request to listen. With captivating sound effects, voices, and an apply section at the end of spark Meaningful Conversations SUSA hit with both kids and parents. Listen to Kids' Bible Stoice podcast on the iHeartRadio app, Apple Podcasts, or wherever you get your podcasts.
