If you love iPhone, you'll love Apple Card. It's the credit card designed for iPhone. It gives you unlimited daily cash back that can earn four point four zero percent annual percentage yield. When you open a high Yield savings account through Apple Card, apply for Applecard in the wallet app subject to credit approval. Savings is available to Apple Card owners subject to eligibility. Apple Card and Savings by Goldman Sachs Bank USA, Salt Lake City Branch Member FDIC terms and more at applecard dot com. 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 digesters to turn the methane from manure into renewable energy that can power farms, towns, and electric cars. Visit us Dairy dot COM's Last Sustainability to learn more.

If you love iPhone, you'll love Apple Card. It's the credit card designed for iPhone. It gives you unlimited daily cash back that can earn four point four zero percent annual percentage yield. When you open a high Yield savings account through Apple Card, apply for Applecard in the wallet app subject to credit approval. Savings is available to Apple Card owners subject to eligibility. Apple Card and Savings by Goldman Sachs Bank USA, Salt Lake City Branch Member FDIC terms and more at applecard dot com. 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 digesters to turn the methane from manure into renewable energy that can power farms, towns, and electric cars. Visit us Dairy dot COM's Last Sustainability to learn more.

Here's a little secret. Most smartphone deals aren't that exciting. To be honest, they're barely worth mentioning. But then there's AT and T and their best deals. Those are quite exciting.

Here's a little secret. Most smartphone deals aren't that exciting. To be honest, they're barely worth mentioning. But then there's AT and T and their best deals. Those are quite exciting.

They're the kind of deals that are really worth talking about, like their deal in the new Samsung Galaxy Z flip six. With this deal, you can trade in your eligible smartphone, any year, any condition for a new Samsung Galaxy Z flip six.

They're the kind of deals that are really worth talking about, like their deal in the new Samsung Galaxy Z flip six. With this deal, you can trade in your eligible smartphone, any year, any condition for a new Samsung Galaxy Z flip six.

It's so good, in fact, it will have you shouting from the rooftops. So get yourself down a street level and learn how to snag the new Samsung Galaxy Z flip six on AT and T and maybe grab a ladder on the way home. AT and T connecting changes everything requires trade in a Galaxy s Note or Z series smartphone, Limited time offer two hundred and fifty six gigabytes for zero dollars. Additional fees, terms and restrictions apply. See att dot com, slash Samsung, or visit an AT and T store for details.

It's so good, in fact, it will have you shouting from the rooftops. So get yourself down a street level and learn how to snag the new Samsung Galaxy Z flip six on AT and T and maybe grab a ladder on the way home. AT and T connecting changes everything requires trade in a Galaxy s Note or Z series smartphone, Limited time offer two hundred and fifty six gigabytes for zero dollars. Additional fees, terms and restrictions apply. See att dot com, slash Samsung, or visit an AT and T store for details.

Does it ever amaze you the sheer arrogance of physics. I don't mean the arrogance of physicists. That's a topic for another day. I mean the very concept that we could understand the universe, the vast reaches of space, the distant stars, and the early moments of the cosmos. We've hardly even left this planet, and yet we imagine that we could understand how distant galaxies are formed and what happens at the center of neutron stars without ever actually visiting them. What would you think if you heard of a biologist who refused to leave her room studying Earth's varied life just by peering out of her windows. And yet it's all that we can do. And so it's incredible what we have learned about the universe just looking out of our cosmic living room windows.

Does it ever amaze you the sheer arrogance of physics. I don't mean the arrogance of physicists. That's a topic for another day. I mean the very concept that we could understand the universe, the vast reaches of space, the distant stars, and the early moments of the cosmos. We've hardly even left this planet, and yet we imagine that we could understand how distant galaxies are formed and what happens at the center of neutron stars without ever actually visiting them. What would you think if you heard of a biologist who refused to leave her room studying Earth's varied life just by peering out of her windows. And yet it's all that we can do. And so it's incredible what we have learned about the universe just looking out of our cosmic living room windows.

Hi.

Hi.

I'm Daniel. I'm a particle physicist, but my curiosity about the universe extends well beyond my living room windows. And welcome to our podcast, Daniel and Jorge Explain the Universe, a production of iHeartRadio. It's just Me and the podcast Today Orge can join us, So I'll be talking to you all about the incredible things in our universe, the things that are close to home, the things that are far away, the things that make us wonder, the things that make us want to go and visit. I'd love to imagine what it's like to go circle a black hole or delve deep into the center of a neutron star, or even just visit another planet and see if there is life. But of course we can't answer all of our questions about the universe by actually going places. All we can do is sit here at home and think about these things, use our minds and our telescopes to peer out of our cosmic living room and try to understand the universe from our tiny little mode of dust. And that's the question at the heart of physics. Can we in fact understand our universe? Is it possible to wrap our puny, little human minds around the incredible mysteries of this vast and incredibly complicated and surprising universe. And when you try to do that, when you ask these questions about the universe, sometimes you come up with a point of confusion. You think, hmm, how does that make any sense? Or what is this actually doing? And that's the point of our podcast to try to bring those questions home to you, to answer your questions about the universe, to explain everything, and along the way, maybe make a few banana jokes. And today on the program we will have an episode chalk full of questions, not just questions from physicists, questions from listeners. And I love getting questions from listeners because they make me ask myself questions. Before I can explain something clear, yearly and well enough for anybody to understand it, I have to really understand it thoroughly. Not just well enough to follow the mathematics and say, hmmm, that must be right, but well enough to explain it using intuitive concepts backwards and forwards and sideways, so that you can really understand it. And for me that's a joy, because sometimes there are things in physics that I never really got to dig into, and when somebody asked me a question about how they work, then it gives me an excuse to go off for an hour or two and read all about it and ask myself all the questions I never quite answered until I have a solid enough understanding of it to explain it to you. So please, if you have a question you would like answered about the universe or something you never really quite understood, send it to us to questions at Danielandjorge dot com. And if you don't like writing emails, you can come to my first ever public office hours, where I'll be hanging out on Zoom and answering questions from the general public. Do you have a question about physics you can't find the answer to on Google. Our to hear more about black holes and singularities and flying through the universe on rockets and solar sales, come to my public office hours. You can find the link on our website, or you can go to sites dot UCI dot edu slash Daniel and you'll find all the information there. It's December fourteenth, twenty twenty at nine am Pacific time, and it's totally free, so see you there. But today on the program, we'll be answering questions that people did send in. Things about space, things about the intergalactic medium, things about huge galaxies, things about gravity. So let's not waste any more time, and let's get right to the first question on the docket, which comes from Nick.

I'm Daniel. I'm a particle physicist, but my curiosity about the universe extends well beyond my living room windows. And welcome to our podcast, Daniel and Jorge Explain the Universe, a production of iHeartRadio. It's just Me and the podcast Today Orge can join us, So I'll be talking to you all about the incredible things in our universe, the things that are close to home, the things that are far away, the things that make us wonder, the things that make us want to go and visit. I'd love to imagine what it's like to go circle a black hole or delve deep into the center of a neutron star, or even just visit another planet and see if there is life. But of course we can't answer all of our questions about the universe by actually going places. All we can do is sit here at home and think about these things, use our minds and our telescopes to peer out of our cosmic living room and try to understand the universe from our tiny little mode of dust. And that's the question at the heart of physics. Can we in fact understand our universe? Is it possible to wrap our puny, little human minds around the incredible mysteries of this vast and incredibly complicated and surprising universe. And when you try to do that, when you ask these questions about the universe, sometimes you come up with a point of confusion. You think, hmm, how does that make any sense? Or what is this actually doing? And that's the point of our podcast to try to bring those questions home to you, to answer your questions about the universe, to explain everything, and along the way, maybe make a few banana jokes. And today on the program we will have an episode chalk full of questions, not just questions from physicists, questions from listeners. And I love getting questions from listeners because they make me ask myself questions. Before I can explain something clear, yearly and well enough for anybody to understand it, I have to really understand it thoroughly. Not just well enough to follow the mathematics and say, hmmm, that must be right, but well enough to explain it using intuitive concepts backwards and forwards and sideways, so that you can really understand it. And for me that's a joy, because sometimes there are things in physics that I never really got to dig into, and when somebody asked me a question about how they work, then it gives me an excuse to go off for an hour or two and read all about it and ask myself all the questions I never quite answered until I have a solid enough understanding of it to explain it to you. So please, if you have a question you would like answered about the universe or something you never really quite understood, send it to us to questions at Danielandjorge dot com. And if you don't like writing emails, you can come to my first ever public office hours, where I'll be hanging out on Zoom and answering questions from the general public. Do you have a question about physics you can't find the answer to on Google. Our to hear more about black holes and singularities and flying through the universe on rockets and solar sales, come to my public office hours. You can find the link on our website, or you can go to sites dot UCI dot edu slash Daniel and you'll find all the information there. It's December fourteenth, twenty twenty at nine am Pacific time, and it's totally free, so see you there. But today on the program, we'll be answering questions that people did send in. Things about space, things about the intergalactic medium, things about huge galaxies, things about gravity. So let's not waste any more time, and let's get right to the first question on the docket, which comes from Nick.

Hey, Daniel Jorge. My name is Nick and I'm a video game programmer from Canada. I have a question for you about intergalactic space. Now, I've always assumed that there's pretty much nothing in the space between galaxies, but recently I read a NASA article that talked about how there's a ton of extragalactic stars that live inside these huge voids. So my question for you is just how much stuff is there inside of intergalactic space? Does it contain mostly regular stars or is there a lot of other things like space dust and black holes.

Hey, Daniel Jorge. My name is Nick and I'm a video game programmer from Canada. I have a question for you about intergalactic space. Now, I've always assumed that there's pretty much nothing in the space between galaxies, but recently I read a NASA article that talked about how there's a ton of extragalactic stars that live inside these huge voids. So my question for you is just how much stuff is there inside of intergalactic space? Does it contain mostly regular stars or is there a lot of other things like space dust and black holes.

In dark matter?

In dark matter?

So I love this question because Nick is exploring the universe with his mind. He's wondering what is out there in the deepest, darkest reaches of space. Is it totally empty? Is there actually something out there? How does a star end up outside of its galaxy? And what else is there in the intergalactic space? So awesome question. Thank you very much Nick for sending it in. And I thought it'd be interesting to answer this question by sort of stepping up into intergalactic space and starting with space that's sort of nearby us. So you know that outer space, of course isn't empty. So what about the space that's right outside of our atmosphere? Is that empty? Is there stuff out there? Well, the space that's in our Solar system is dominated by stuff produced by the Sun. This is called the solar wind. So outer space is not empty. It's filled with particles that come from the Sun. These are electrons and protons and sometimes of particles, and they're produced by the same processes that creates all the light for which the Sun is quite famous. All that crazy fusion that's going on in the Sun also injects a lot of particles, so we call this the solar wind. It's not wind in the sense that there's any air in space, of course. It's just a huge stream of particles, a flux of particles, and it's a lot. There are like five to ten million protons per cubic meter, and these things are moving at four hundred kilometers per second, so that's definitely not nothing. And ten million protons sounds like a lot, but remember that in a drop of water there is like ten to the twenty three protons, So it's quite diffuse compared to like our atmosphere or anything on the surface, but it's definitely not empty. You also have to remember that out there in space is a lot of matter that we cannot see. We think that there's five times as much dark matter as there is normal matter in the universe, and that it's clustered roughly the same way that normal matter is. It's a bit more tofu it's not localized into planets and stars. It's fluffy and spread out, but it's out there in space. So if you build a box in space. That's a cubic meter. You're probably also capturing some dark matter one or two protons worth of dark matter per cubic meter, all right, So that's inside our Solar system. We already see that space is not empty. If you take a step outside our Solar system, sort of into interstellar space, but still within our galaxy, then we have something that's called the interstellar medium. This is ninety nine percent gas. It's just hydrogen and helium that's floating out there, stuff that didn't coalesce into a star or sort of left out the last time stars were made, and it could also be the building blocks of future stars. You know that our stars were made when huge clouds of gas and dust were sort of shocked maybe by a supernova or something else, and coalesced into star forming regions. And this kind of stuff can still happen. It could happen in the interstellar medium. So this is ninety nine percent gases, like one percent dust, which of these tiny little grains of stuff left over from other stars, and it's mostly hydrogen out there, and there's not a lot of stuff. There's about one molecule of hydrogen every ten thousand to one million cubic meters, so it's not a whole lot of stuff out there. It's pretty empty, but you know, it's not empty space. And of course, inside our galaxy you still have to multiply by five for dark matter, because there's a lot of dark matter in our galaxy, even out there between the stars, right, the dark matter is spread out more diffusely than the normal matter, but it's still there. So if you're inside the galaxy, there's still a lot of dark matter, all right. So that's just sort of the setup. Now let's get directly to Nix's question. Nixt question is about what's in intergalactic space. So here we have our galaxy, for example, the Milky Way, and this Andromeda, just for example, several million light years away. Nick's really asking about what's between here and there. And now we're still inside our cluster of galaxies. Remember, galaxies are not just like floating out there in space randomly. They are also organized into structures we call these galactic clusters, and gravity is strong enough to hold these things together. All these galaxies are orbiting some central point. So what's in intergalactic space inside one of these galaxy clusters, Well, it's something very cleverly named the intergalactic medium, which basically means the stuff between galaxies. Well what is this stuff, Well, it's basically plasma. It's ionized hydrogen. So hydrogen is just a proton and an electron when it's neutral, But ionized hydrogen is when there's too much energy in that electron, so it can't be held onto by the proton, so the two part their way. So ionized hydrogen is basically just a proton. And this stuff is called a plasma because it's ionized, and that's what a plasma is. You take a gas and you strip away the electrons and you call that a plasma. So this stuff is the intergalactic medium, and it stretches sort of between galaxies. And you might think, well, that doesn't sound like a lot of stuff, but it's surprising. There's so much space out there between galaxies that even though there's not a lot of it is like you know, maybe one hydrogen out of per cubic meter, it really adds up. So there's these incredible reaches of space. Right Like, the space between us and the next galaxy is millions of light years. So even if the stuff between us and them isn't very dense. There's a huge volume. So actually about half of the baryonic matter in the universe, half of the atoms in the universe, are in this intergalactic medium. So half of it is in galaxies, which means stars and planets and hamsters and bananas and all that crazy stuff, and the other half is between galaxies. So yes, Nick, there is stuff between the galaxies. Like half of all the familiar matter in the universe is between galaxies. And these filaments are crazy. They stretch between the galaxies, and you can think of the galaxies as sort of like the bright spots in this web, and there are these connections between the galaxies, these streams between the galaxies. And we talked on the podcast recently about the magnetic fields that are out there in deep space. One of the really fascinating things is that you can use these streams of stuff between galaxies, this intergalactic medium to measure those magnetic fields because the magnetic fields affect how those streams flow. It's really pretty super awesome. But that's not the only stuff that's out there in between galaxies. As Nick said, there are sometimes stars out there. How do stars end up in between galaxies? Well, they don't typically form out there on their own in the darkness of space. Remember that the structure of the universe forms bottom up, meaning that you start out with like denser clouds of hydrogen, and then in those clouds you get stars, and those stars come together to form galaxies. In the very early universe, you may have had stars more distributed through the universe than we have today, but then they came together and they formed galaxies. And dark matter also plays a really important role in that structure formation. Remember that there's more dark matter than anything else in the universe, and so where there was more dark matter, all that stuff fell in and formed the galaxies. All right, so we expect to find the stars mostly inside the galaxies. How do stars end up outside the galaxies? Well, stars can get thrown out of a galaxy. You know, most of the stars are swirling around the center, but sometimes there are collisions. You know, stars will bump into each other, not physically like splash, like a stellar collision, like the way a particle physicist might build a collider. This smashes two stars together, but just sort of gravitationally tugging on each other. If stars pass near each other, one of them might fling the other one outside of the galaxy. Because just like the Earth has an escape velocity, and if you throw a ball, it's going to come back to Earth, but if you throw a ball hard enough, it would go out into space. And in the same way, our Sun has an escape velocity. If you shoot a rocket out into space fast enough, it will leave the Sun's gravitational hold. And if a star ends up with just the right velocity in the right angle, it can also escape the gravitational hold of the galaxy. And that happens, and so you end up with some stars out there in intergalactic space. But most of the stuff in intergalactic space is this rarefied plasma, this intergalactic medium. And the other really weird thing about that medium is that it's really really hot. Like you think about deep space as being cold and frozen, and if you got dropped out there, you would crystallize instantly, and that's probably true. Remember that temperature is a weird thing. There's temperature and then there's heat. So we call this plasma very very hot. In fact, it's temperature or ranks in the millions of kelvins. But that's just because the individual particles in the plasma are zozooming along, so they have a lot of speed, and microscopically, that's what temperature is. You ask, why is this gas hot or that gas cold, it's because the particles inside it are zooming around if they're hot, or not zooming around if they're cold. And so these particles are zooming around, which technically makes this inter galactic medium hot. But it's also not very dense, and so if you're out there, it wouldn't be able to warm you up. Yes, you'd be hit by these zippy little protons slamming into you, but you would still not have enough heat to stay warm, and you would freeze. So you could get dropped into the super hot intergalactic medium and still freeze into an ice cube. Space is weird, and if you want to go further, you know, the deeper reaches of space are the ones that are outside our galactic cluster. These filaments they tie together galaxies in our cluster, But our cluster itself is part of a larger structure we call a supercluster, and these super cl clusters, it's not entirely clear how gravitationally bound they are. Some people think that they're too big that gravity's not really holding them together, that they're getting separated by dark energy. Other people think that parts of the supercluster might be small enough to be tied together. In either case, there are also these filaments between galaxy clusters. This was recently discovered by scientists trying to understand how far into space magnetic fields go, and they use the filaments between galaxies to figure out that there are magnetic fields out there in deep space. And then they found these filaments between galaxy clusters that show that there are also magnetic fields out there in deep space. Now, the dark matter dark matter, remember, clumps together like normal matter does. So there are huge blobs of dark matter associated with each galaxy. But then dark matter peters out in this less of it out there in intergalactic space. So, Nick, to answer your question, was in intergalactic space, it's mostly this rarefied plasmi, these filaments of protons that it's been between galaxies. There's a little bit of dark matter out there, but not as much. But remember that all of the universe also is bathed in dark energy, something we don't understand, but is two thirds of the energy budget of the universe. That's busy pulling the universe apart, accelerating the expansion of the universe, and tearing all of these galaxy clusters apart from each other. Great question, Thank you very much Nick for sending that in super fun stuff to talk about. I want to get to the next question, but first let's take a quick break. With big wireless providers, what you see is never what you get. Somewhere between the store and your first month's bill, the price you thought you were paying magically skyrockets. With Mintmobile, You'll never have to worry about gotcha's ever again. When Mint Mobile says fifteen dollars a month for a three month plan, they really mean it. I've used mint Mobile and the call quality is always so crisp and so clear. I can recommend it to you, So say bye bye to your overpriced wireless plans, jaw drop monthly bills and unexpected overages. You can use your own phone with any Mint Mobile plan and bring your phone number along with your existing contacts. So dit your overpriced wireless with Mint Mobiles deal and get three months a premium wireless service for fifteen bucks a month. To get this new customer offer and your new three month premium wireless plan for just fifteen bucks a month go to mintmobile dot com slash universe. That's mintmobile dot com slash universe. Cut your wireless bill to fifteen bucks a month. At mintmobile dot com slash Universe. Forty five dollars upfront payment required equivalent to fifteen dollars per month new customers on first three month plan only speeds slower about forty gigabytes on unlimited plan. Additional taxi speeds and restrictions apply. See mint mobile for details.

So I love this question because Nick is exploring the universe with his mind. He's wondering what is out there in the deepest, darkest reaches of space. Is it totally empty? Is there actually something out there? How does a star end up outside of its galaxy? And what else is there in the intergalactic space? So awesome question. Thank you very much Nick for sending it in. And I thought it'd be interesting to answer this question by sort of stepping up into intergalactic space and starting with space that's sort of nearby us. So you know that outer space, of course isn't empty. So what about the space that's right outside of our atmosphere? Is that empty? Is there stuff out there? Well, the space that's in our Solar system is dominated by stuff produced by the Sun. This is called the solar wind. So outer space is not empty. It's filled with particles that come from the Sun. These are electrons and protons and sometimes of particles, and they're produced by the same processes that creates all the light for which the Sun is quite famous. All that crazy fusion that's going on in the Sun also injects a lot of particles, so we call this the solar wind. It's not wind in the sense that there's any air in space, of course. It's just a huge stream of particles, a flux of particles, and it's a lot. There are like five to ten million protons per cubic meter, and these things are moving at four hundred kilometers per second, so that's definitely not nothing. And ten million protons sounds like a lot, but remember that in a drop of water there is like ten to the twenty three protons, So it's quite diffuse compared to like our atmosphere or anything on the surface, but it's definitely not empty. You also have to remember that out there in space is a lot of matter that we cannot see. We think that there's five times as much dark matter as there is normal matter in the universe, and that it's clustered roughly the same way that normal matter is. It's a bit more tofu it's not localized into planets and stars. It's fluffy and spread out, but it's out there in space. So if you build a box in space. That's a cubic meter. You're probably also capturing some dark matter one or two protons worth of dark matter per cubic meter, all right, So that's inside our Solar system. We already see that space is not empty. If you take a step outside our Solar system, sort of into interstellar space, but still within our galaxy, then we have something that's called the interstellar medium. This is ninety nine percent gas. It's just hydrogen and helium that's floating out there, stuff that didn't coalesce into a star or sort of left out the last time stars were made, and it could also be the building blocks of future stars. You know that our stars were made when huge clouds of gas and dust were sort of shocked maybe by a supernova or something else, and coalesced into star forming regions. And this kind of stuff can still happen. It could happen in the interstellar medium. So this is ninety nine percent gases, like one percent dust, which of these tiny little grains of stuff left over from other stars, and it's mostly hydrogen out there, and there's not a lot of stuff. There's about one molecule of hydrogen every ten thousand to one million cubic meters, so it's not a whole lot of stuff out there. It's pretty empty, but you know, it's not empty space. And of course, inside our galaxy you still have to multiply by five for dark matter, because there's a lot of dark matter in our galaxy, even out there between the stars, right, the dark matter is spread out more diffusely than the normal matter, but it's still there. So if you're inside the galaxy, there's still a lot of dark matter, all right. So that's just sort of the setup. Now let's get directly to Nix's question. Nixt question is about what's in intergalactic space. So here we have our galaxy, for example, the Milky Way, and this Andromeda, just for example, several million light years away. Nick's really asking about what's between here and there. And now we're still inside our cluster of galaxies. Remember, galaxies are not just like floating out there in space randomly. They are also organized into structures we call these galactic clusters, and gravity is strong enough to hold these things together. All these galaxies are orbiting some central point. So what's in intergalactic space inside one of these galaxy clusters, Well, it's something very cleverly named the intergalactic medium, which basically means the stuff between galaxies. Well what is this stuff, Well, it's basically plasma. It's ionized hydrogen. So hydrogen is just a proton and an electron when it's neutral, But ionized hydrogen is when there's too much energy in that electron, so it can't be held onto by the proton, so the two part their way. So ionized hydrogen is basically just a proton. And this stuff is called a plasma because it's ionized, and that's what a plasma is. You take a gas and you strip away the electrons and you call that a plasma. So this stuff is the intergalactic medium, and it stretches sort of between galaxies. And you might think, well, that doesn't sound like a lot of stuff, but it's surprising. There's so much space out there between galaxies that even though there's not a lot of it is like you know, maybe one hydrogen out of per cubic meter, it really adds up. So there's these incredible reaches of space. Right Like, the space between us and the next galaxy is millions of light years. So even if the stuff between us and them isn't very dense. There's a huge volume. So actually about half of the baryonic matter in the universe, half of the atoms in the universe, are in this intergalactic medium. So half of it is in galaxies, which means stars and planets and hamsters and bananas and all that crazy stuff, and the other half is between galaxies. So yes, Nick, there is stuff between the galaxies. Like half of all the familiar matter in the universe is between galaxies. And these filaments are crazy. They stretch between the galaxies, and you can think of the galaxies as sort of like the bright spots in this web, and there are these connections between the galaxies, these streams between the galaxies. And we talked on the podcast recently about the magnetic fields that are out there in deep space. One of the really fascinating things is that you can use these streams of stuff between galaxies, this intergalactic medium to measure those magnetic fields because the magnetic fields affect how those streams flow. It's really pretty super awesome. But that's not the only stuff that's out there in between galaxies. As Nick said, there are sometimes stars out there. How do stars end up in between galaxies? Well, they don't typically form out there on their own in the darkness of space. Remember that the structure of the universe forms bottom up, meaning that you start out with like denser clouds of hydrogen, and then in those clouds you get stars, and those stars come together to form galaxies. In the very early universe, you may have had stars more distributed through the universe than we have today, but then they came together and they formed galaxies. And dark matter also plays a really important role in that structure formation. Remember that there's more dark matter than anything else in the universe, and so where there was more dark matter, all that stuff fell in and formed the galaxies. All right, so we expect to find the stars mostly inside the galaxies. How do stars end up outside the galaxies? Well, stars can get thrown out of a galaxy. You know, most of the stars are swirling around the center, but sometimes there are collisions. You know, stars will bump into each other, not physically like splash, like a stellar collision, like the way a particle physicist might build a collider. This smashes two stars together, but just sort of gravitationally tugging on each other. If stars pass near each other, one of them might fling the other one outside of the galaxy. Because just like the Earth has an escape velocity, and if you throw a ball, it's going to come back to Earth, but if you throw a ball hard enough, it would go out into space. And in the same way, our Sun has an escape velocity. If you shoot a rocket out into space fast enough, it will leave the Sun's gravitational hold. And if a star ends up with just the right velocity in the right angle, it can also escape the gravitational hold of the galaxy. And that happens, and so you end up with some stars out there in intergalactic space. But most of the stuff in intergalactic space is this rarefied plasma, this intergalactic medium. And the other really weird thing about that medium is that it's really really hot. Like you think about deep space as being cold and frozen, and if you got dropped out there, you would crystallize instantly, and that's probably true. Remember that temperature is a weird thing. There's temperature and then there's heat. So we call this plasma very very hot. In fact, it's temperature or ranks in the millions of kelvins. But that's just because the individual particles in the plasma are zozooming along, so they have a lot of speed, and microscopically, that's what temperature is. You ask, why is this gas hot or that gas cold, it's because the particles inside it are zooming around if they're hot, or not zooming around if they're cold. And so these particles are zooming around, which technically makes this inter galactic medium hot. But it's also not very dense, and so if you're out there, it wouldn't be able to warm you up. Yes, you'd be hit by these zippy little protons slamming into you, but you would still not have enough heat to stay warm, and you would freeze. So you could get dropped into the super hot intergalactic medium and still freeze into an ice cube. Space is weird, and if you want to go further, you know, the deeper reaches of space are the ones that are outside our galactic cluster. These filaments they tie together galaxies in our cluster, But our cluster itself is part of a larger structure we call a supercluster, and these super cl clusters, it's not entirely clear how gravitationally bound they are. Some people think that they're too big that gravity's not really holding them together, that they're getting separated by dark energy. Other people think that parts of the supercluster might be small enough to be tied together. In either case, there are also these filaments between galaxy clusters. This was recently discovered by scientists trying to understand how far into space magnetic fields go, and they use the filaments between galaxies to figure out that there are magnetic fields out there in deep space. And then they found these filaments between galaxy clusters that show that there are also magnetic fields out there in deep space. Now, the dark matter dark matter, remember, clumps together like normal matter does. So there are huge blobs of dark matter associated with each galaxy. But then dark matter peters out in this less of it out there in intergalactic space. So, Nick, to answer your question, was in intergalactic space, it's mostly this rarefied plasmi, these filaments of protons that it's been between galaxies. There's a little bit of dark matter out there, but not as much. But remember that all of the universe also is bathed in dark energy, something we don't understand, but is two thirds of the energy budget of the universe. That's busy pulling the universe apart, accelerating the expansion of the universe, and tearing all of these galaxy clusters apart from each other. Great question, Thank you very much Nick for sending that in super fun stuff to talk about. I want to get to the next question, but first let's take a quick break. With big wireless providers, what you see is never what you get. Somewhere between the store and your first month's bill, the price you thought you were paying magically skyrockets. With Mintmobile, You'll never have to worry about gotcha's ever again. When Mint Mobile says fifteen dollars a month for a three month plan, they really mean it. I've used mint Mobile and the call quality is always so crisp and so clear. I can recommend it to you, So say bye bye to your overpriced wireless plans, jaw drop monthly bills and unexpected overages. You can use your own phone with any Mint Mobile plan and bring your phone number along with your existing contacts. So dit your overpriced wireless with Mint Mobiles deal and get three months a premium wireless service for fifteen bucks a month. To get this new customer offer and your new three month premium wireless plan for just fifteen bucks a month go to mintmobile dot com slash universe. That's mintmobile dot com slash universe. Cut your wireless bill to fifteen bucks a month. At mintmobile dot com slash Universe. Forty five dollars upfront payment required equivalent to fifteen dollars per month new customers on first three month plan only speeds slower about forty gigabytes on unlimited plan. Additional taxi speeds and restrictions apply. See mint mobile for details.

AI might be the most important new computer technology ever. It's storming every industry and literally billions of dollars are being invested, so buckle up. The problem is that AI needs a lot of speed and processing power. So how do you compete without cost spiraling out of control. It's time to upgrade to the next generation of the cloud. Oracle Cloud Infrastructure or OCI. OCI is a single platform for your infrastructure, database, application development, and AI needs. OCI has four to eight times the bandwidth of other clouds, offers one consistent price instead of variable regional pricing, and of course nobody does data better than Oracle. So now you can train your AI models at twice the speed and less than half the cost of other clouds. If you want to do more and spend less, like Uber eight by eight and Data Bricks Mosaic. Take a free test drive of Oci at Oracle dot com slash Strategic. That's Oracle dot com slash Strategic. Oracle dot com slash Strategic.

AI might be the most important new computer technology ever. It's storming every industry and literally billions of dollars are being invested, so buckle up. The problem is that AI needs a lot of speed and processing power. So how do you compete without cost spiraling out of control. It's time to upgrade to the next generation of the cloud. Oracle Cloud Infrastructure or OCI. OCI is a single platform for your infrastructure, database, application development, and AI needs. OCI has four to eight times the bandwidth of other clouds, offers one consistent price instead of variable regional pricing, and of course nobody does data better than Oracle. So now you can train your AI models at twice the speed and less than half the cost of other clouds. If you want to do more and spend less, like Uber eight by eight and Data Bricks Mosaic. Take a free test drive of Oci at Oracle dot com slash Strategic. That's Oracle dot com slash Strategic. Oracle dot com slash Strategic.

If you love iPhone, you'll love Apple Card. It's the credit card designed for iPhone. It gives you unlimited daily cash back that can earn four point four zero percent annual percentage yield. When you open a high Yield savings account through Applecard, apply for Applecard in the Wallet app, subject to credit approval. Savings is available to Applecard owners subject to eligibility. Apple Card and Savings by Goldman sax Banks, a Salt Lake City branch member, FDIC terms and more at applecar dot com. All right, we're back and we're answering listener questions. Today we're helping you explore the things you are curious about. What's out there in deep space? How does it all work? So sit down and enjoy a mental journey into the deep dark regions of the universe as we use physics to try to understand how it all works, and so we're answering listener questions and here comes our second one.

If you love iPhone, you'll love Apple Card. It's the credit card designed for iPhone. It gives you unlimited daily cash back that can earn four point four zero percent annual percentage yield. When you open a high Yield savings account through Applecard, apply for Applecard in the Wallet app, subject to credit approval. Savings is available to Applecard owners subject to eligibility. Apple Card and Savings by Goldman sax Banks, a Salt Lake City branch member, FDIC terms and more at applecar dot com. All right, we're back and we're answering listener questions. Today we're helping you explore the things you are curious about. What's out there in deep space? How does it all work? So sit down and enjoy a mental journey into the deep dark regions of the universe as we use physics to try to understand how it all works, and so we're answering listener questions and here comes our second one.

What I've been struck by from your podcast is that scale wise, we seem to lie in the middle of the universe. On one end, there's all these tiny, tiny particles, and on the other extreme there's this enormous scale of all these countless galaxies, and we happen to be somewhere in the middle. Separately, quantum physics has this weird observer effect, a situation where we, no matter what we do, have an impact on the state of something that we are trying to study. It's like our presence or our attention partly to find the state of things when we try to analyze it. My question is whether these are somehow related. I find it hard to believe that we just happen to be in the middle, we just seeing our version of the universe, that this perception of being in the middle scale wise is actually because we are observing the universe and we are the center of how it is presented to us.

What I've been struck by from your podcast is that scale wise, we seem to lie in the middle of the universe. On one end, there's all these tiny, tiny particles, and on the other extreme there's this enormous scale of all these countless galaxies, and we happen to be somewhere in the middle. Separately, quantum physics has this weird observer effect, a situation where we, no matter what we do, have an impact on the state of something that we are trying to study. It's like our presence or our attention partly to find the state of things when we try to analyze it. My question is whether these are somehow related. I find it hard to believe that we just happen to be in the middle, we just seeing our version of the universe, that this perception of being in the middle scale wise is actually because we are observing the universe and we are the center of how it is presented to us.

Wow, thanks so much for that question, super fun. I love the general concept behind this question, this idea that the universe as we see it is somehow a product of how we are looking and who we are, because remember that physics is often trying to separate ourselves from the essential humanity of the way we think. We are trying to get some universal understanding of the universe, something that when aliens come, we could use it to compare notes with them. We could talk to them using mathematics and understand the same physics questions. The kind of stuff we put on the Voyager and the Pioneer probes is our most distilled understanding of the universe that we hope that we think alien intelligence could also understand. And that's because physicists are trying to understand the universe not just from a human perspective, but from a fundamental perspective. We imagine, we hope that there's a way to understand the universe separated from the biases of the human perspective. But is that even possible, because we know that quantum mechanics tells us that observing things changed it. So I think that's what's at the heart of this question, So thank you very much for asking it. Let's begin by talking about the scale. That question started by talking about how we are in the middle of everything between the tiny tiny particles and the huge, huge galaxies. So is that actually true? Well, what is the smallest thing that we can see? What is the smallest thing that humans have observed? Well, if you take atoms, for example, and strip them apart, you get down to the nucleus, and inside the nucleus are proton and neutrons, and inside those protons and neutrons are quarks. If you get down to the smallest stuff, then we're talking about fundamental particles. And we had a whole episode in the podcast about what is a fundamental particle? How big is it? What does it even mean? And unfortunately it's sort of a philosophical question, like what is the size of an electron or what is the size of a quark? And in our theory, we think about these things as point particles like dots in space with no volume, which means they don't have a well defined size. And if you ask three different theoretical physicists how you define the size of a particle, you might get three different answers. But what we decided on that podcast was that it sort of makes sense to talk about the size of a particle based on its interactions, like how it touches other stuff, because that really determines sort of how it fits into the nature of the universe, how close you can get to it. If you think about the size of something, it's like, you know, the distance between its left edge and its right edge. Those edges are determined by when it pushes back on others things. So just as an exercise, you can imagine the size of quarks is like how big is the proton? Because quarks come together to make a proton, so you can imagine the quarks are sort of inside their own little bubble inside the proton. So the distances involved inside the proton are crazy tiny numbers, things like ten to the minus fifteen meters. You know, that's zero points zero zero zero, or 's zero fifteen zeros and then one. So it's a really unfathomedly tiny scale. And you know, it's hard for a physicists or hard for anybody to imagine what's really going on down there. And this is where we have to rely on the mathematics. We look at that number, we say, well, I assume that means something it's hard to really understand. Is that really a distance? Is someone down there with a ruler and you could measure the distance between the quarks. But anyway, protons are down there about ten to the minus fifteen meters, so fifteen orders of magnitude smaller than a human. A human is about one meter, right to a physicist, within a factor of two, a human is one meter. We don't really care about factors of two or even five. We're mostly just trying to figure out, like, roughly, what is the order of magnitude of stuff? And you know, of course we designed the meter to be approximately a human side because it's it's the kind of thing we used to measure, all right. So then zooming out how big are cosmic structures like our milky way, or a milky way is about one hundred thousand light years across. Translate that into meters and you get about ten to the twenty meters. So already the scale extends further on the big side than on the small side, Like a proton or a quark is like fifteen orders of magnitude smaller than us, but the Milky Way is twenty orders of magnitude bigger than us, And that's a big deal. That five orders of magnitude is a huge factor. You know, that's one hundred thousand. If I ask to borrow one hundred thousand dollars and then I pain you back to just one dollar, that would make a pretty big difference to your life. But the Milky Way is not the biggest thing that's out there. Clusters of galaxies are these structures of galaxies that come together, and superclusters are these clusters of clusters, and that's probably the biggest thing in the universe because if you zoom out even further, you see it's just like a vast ocean of superclusters. And so the scale of the supercluster is like ten to the twenty four meters. So that means that the smallest things we can see are fifteen orders of magnitudes smaller than we are. But the biggest things we can see are twenty four orders of magnitude bigger than we are. So are we really at the center? We're actually sort of on the small edge of things. Something that's about in the middle, you know, that's between a proton and a supercluster is something that's like one hundred kilometers wide, so you know, I don't know, take the city of Los Angeles for example, that's about one hundred kilometers wide. So Los Angeles has the same relationship to a proton as a supercluster does to Los Angeles, which is pretty incredible.

Wow, thanks so much for that question, super fun. I love the general concept behind this question, this idea that the universe as we see it is somehow a product of how we are looking and who we are, because remember that physics is often trying to separate ourselves from the essential humanity of the way we think. We are trying to get some universal understanding of the universe, something that when aliens come, we could use it to compare notes with them. We could talk to them using mathematics and understand the same physics questions. The kind of stuff we put on the Voyager and the Pioneer probes is our most distilled understanding of the universe that we hope that we think alien intelligence could also understand. And that's because physicists are trying to understand the universe not just from a human perspective, but from a fundamental perspective. We imagine, we hope that there's a way to understand the universe separated from the biases of the human perspective. But is that even possible, because we know that quantum mechanics tells us that observing things changed it. So I think that's what's at the heart of this question, So thank you very much for asking it. Let's begin by talking about the scale. That question started by talking about how we are in the middle of everything between the tiny tiny particles and the huge, huge galaxies. So is that actually true? Well, what is the smallest thing that we can see? What is the smallest thing that humans have observed? Well, if you take atoms, for example, and strip them apart, you get down to the nucleus, and inside the nucleus are proton and neutrons, and inside those protons and neutrons are quarks. If you get down to the smallest stuff, then we're talking about fundamental particles. And we had a whole episode in the podcast about what is a fundamental particle? How big is it? What does it even mean? And unfortunately it's sort of a philosophical question, like what is the size of an electron or what is the size of a quark? And in our theory, we think about these things as point particles like dots in space with no volume, which means they don't have a well defined size. And if you ask three different theoretical physicists how you define the size of a particle, you might get three different answers. But what we decided on that podcast was that it sort of makes sense to talk about the size of a particle based on its interactions, like how it touches other stuff, because that really determines sort of how it fits into the nature of the universe, how close you can get to it. If you think about the size of something, it's like, you know, the distance between its left edge and its right edge. Those edges are determined by when it pushes back on others things. So just as an exercise, you can imagine the size of quarks is like how big is the proton? Because quarks come together to make a proton, so you can imagine the quarks are sort of inside their own little bubble inside the proton. So the distances involved inside the proton are crazy tiny numbers, things like ten to the minus fifteen meters. You know, that's zero points zero zero zero, or 's zero fifteen zeros and then one. So it's a really unfathomedly tiny scale. And you know, it's hard for a physicists or hard for anybody to imagine what's really going on down there. And this is where we have to rely on the mathematics. We look at that number, we say, well, I assume that means something it's hard to really understand. Is that really a distance? Is someone down there with a ruler and you could measure the distance between the quarks. But anyway, protons are down there about ten to the minus fifteen meters, so fifteen orders of magnitude smaller than a human. A human is about one meter, right to a physicist, within a factor of two, a human is one meter. We don't really care about factors of two or even five. We're mostly just trying to figure out, like, roughly, what is the order of magnitude of stuff? And you know, of course we designed the meter to be approximately a human side because it's it's the kind of thing we used to measure, all right. So then zooming out how big are cosmic structures like our milky way, or a milky way is about one hundred thousand light years across. Translate that into meters and you get about ten to the twenty meters. So already the scale extends further on the big side than on the small side, Like a proton or a quark is like fifteen orders of magnitude smaller than us, but the Milky Way is twenty orders of magnitude bigger than us, And that's a big deal. That five orders of magnitude is a huge factor. You know, that's one hundred thousand. If I ask to borrow one hundred thousand dollars and then I pain you back to just one dollar, that would make a pretty big difference to your life. But the Milky Way is not the biggest thing that's out there. Clusters of galaxies are these structures of galaxies that come together, and superclusters are these clusters of clusters, and that's probably the biggest thing in the universe because if you zoom out even further, you see it's just like a vast ocean of superclusters. And so the scale of the supercluster is like ten to the twenty four meters. So that means that the smallest things we can see are fifteen orders of magnitudes smaller than we are. But the biggest things we can see are twenty four orders of magnitude bigger than we are. So are we really at the center? We're actually sort of on the small edge of things. Something that's about in the middle, you know, that's between a proton and a supercluster is something that's like one hundred kilometers wide, so you know, I don't know, take the city of Los Angeles for example, that's about one hundred kilometers wide. So Los Angeles has the same relationship to a proton as a supercluster does to Los Angeles, which is pretty incredible.

Right.

Right.

That tells you how ting a proton is compared to the glorious city of LA and also how big a supercluster is compared to LA. And I know sometimes it feels like you're driving all the way across a supercluster when you're stuck in traffic in LA. But trust me, supercluster is much bigger than Los Angeles. So we're not actually in the middle. Humans are not really in the middle of these two scales. But still your point holds. I mean, we are much closer to the middle than we are to the edges. Right, We're not proton sized, We're not supercluster sized. We're roughly speaking between these two scales. And it's definitely true that the size of us controls what we can see. Right. Our ability to probe things that are really really small depends on the tools that we build to probe them. On the other hand, our ability to see things that are really really big doesn't really depend on our size. It's limited more on the speed of light, like the time it takes information to get to us from these vast structures and our ability to build telescopes to gather that light. For example, if we could build a huge number of telescopes that surrounded the Earth that gathered light from all over the universe, we could build an incredible three D map of the universe and understand the structure of superclusters and their distribution and stuff like. We still don't even really know what the map of the universe, the observable universe, looks like, only because we haven't spent enough time looking. The only thing that limits us to building this map is just gathering the light in telescopes. So on the small side, I think there definitely is an effect because we have to use objects that we can control in order to see things that are small, Like we'd like to see things that are much much smaller, but we're limited to building tools out of the objects that we can control. That's how we've gotten down to ten to the minus fifteen meters. We've used particle colliders, for example, to smash these things together. If we were made out of much smaller particles, we could manipulate even smaller particles and we could probe even further. But then one might ask, well, how small can you probe?

That tells you how ting a proton is compared to the glorious city of LA and also how big a supercluster is compared to LA. And I know sometimes it feels like you're driving all the way across a supercluster when you're stuck in traffic in LA. But trust me, supercluster is much bigger than Los Angeles. So we're not actually in the middle. Humans are not really in the middle of these two scales. But still your point holds. I mean, we are much closer to the middle than we are to the edges. Right, We're not proton sized, We're not supercluster sized. We're roughly speaking between these two scales. And it's definitely true that the size of us controls what we can see. Right. Our ability to probe things that are really really small depends on the tools that we build to probe them. On the other hand, our ability to see things that are really really big doesn't really depend on our size. It's limited more on the speed of light, like the time it takes information to get to us from these vast structures and our ability to build telescopes to gather that light. For example, if we could build a huge number of telescopes that surrounded the Earth that gathered light from all over the universe, we could build an incredible three D map of the universe and understand the structure of superclusters and their distribution and stuff like. We still don't even really know what the map of the universe, the observable universe, looks like, only because we haven't spent enough time looking. The only thing that limits us to building this map is just gathering the light in telescopes. So on the small side, I think there definitely is an effect because we have to use objects that we can control in order to see things that are small, Like we'd like to see things that are much much smaller, but we're limited to building tools out of the objects that we can control. That's how we've gotten down to ten to the minus fifteen meters. We've used particle colliders, for example, to smash these things together. If we were made out of much smaller particles, we could manipulate even smaller particles and we could probe even further. But then one might ask, well, how small can you probe?

Right?

Right?

And we don't know if there's a minimum size to stuff in the universe. It might be that things just get smaller and smaller, that inside the cork there are smaller particles, and inside that there are smaller particles, and inside that there are smaller particles, and it literally just goes on forever. It might be the things can get infinitely small, But I suspect that's not the case, because the universe is quantum mechanical, which means it likes to have discrete units. It likes to have a basis. It likes to be built out of fundamental building blocks. And we don't know what that scale is. We don't know what the size or the smallest thing is. But we suspect that the universe follows these rules of quantum mechanics, and we can make some very bad estimates for how small the smallest thing might be. We take the numbers that we have around, like planks constant and the speed of light and the gravitational constant, and we can and squish those numbers together, multiply them by each other, and divide and do all sorts of stuff, and do we get a number that has distance units. Right, it's just a number that means a distance. Doesn't mean that it is the size of the smallest particle or the scale of space pixels or anything like that. It just means like, hey, this is the number we can get. And we do this kind of estimate because we don't have any better way of understanding what the smallest thing in the universe is. This is like the dumbest thing you can do. Also the only thing we can do at this point, So better to do the dumbest thing than to do nothing. And you put all those numbers together, you get something like ten to the minus thirty five meters, And that suggests that we could continue exploring the universe twenty more orders of magnitude smaller than we have. Right, We've gotten down to like ten to the minus fifteen meters. So there's like twenty more orders of magnitude left to explore in the universe, maybe, we think, but we suspect there might be a minimum size there. On the other side, is there a maximum size of something we can explore? Well, we think that the largest thing in the universe is a supercluster, meaning that after that there isn't any organized structure. We don't think superclusters have gathered together to make super duper clusters, whether those have pulled together to make super duper duper clusters, And that's for a good reason. That's just because gravity hasn't had enough time to organize that stuff. Remember that structure in the universe is organized bottom up. Stars are formed, they come together to make galaxies. Those galaxies come together to make clusters. Those clusters come together to make superclusters, and all this stuff takes time because gravity is pretty weak. So after billions of years it's formed these superclusters which are like just barely held together gravitationally. Will it make super duper clusters in the future, We don't know, because there's an opposing force they have, dark energy. Dark energy is pulling the universe apart. So anything that gravity is not like holding together the way your body holds itself together, or the Earth holds you on it, or the Sun holds the Earth around it will get pulled apart by dark energy. So gravity's had its moment to build structures, and it might be that it's run out of time that anything that's not now gravitationally held together will get torn apart and separated by dark energy. So that suggests that even though the universe itself might be infinite, the biggest thing in the universe might already have been formed. It might be that it MAXs out at ten to the twenty four meters. Now, there's one more aspect to this wonderful question I want to touch on, which is this quantum observer effect. It's true that every time you observe something in the universe, you affect it. You can't measure anything in the universe without interacting with it. Even just looking at something requires that you bounce a photon off of it, because you can't see something unless there are photons coming from that thing to your eyeballs. So there's literally no way to know anything about the universe without interacting with it. And interacting with things changes them. So this is intimate relationship between the observer person making a measurement trying to understand the universe, and the thing that's being observed. There's no way to separate those two things. So if aliens come and they do physics differently, they might see different observations. They will definitely have different ways of thinking about the universe. But it's impossible to try to develop a system of understanding a set of observations that are separate from the person doing the observer. So certainly there is an influence there the way we do observations the way we think about the universe. But I don't see a direct connection between this idea that you affect things when you observe them in the universe and the size of things in the universe. I think we're much more limited just by the life that we can gather to see biggest things in the universe, and by the probes we can use to see the smallest things in the universe. All right, so are we in the middle of everything? Sort of things seem to be more big than they are small at at this point. We don't know if we can drill down smaller to see even smaller things, but we suspect we might have already seen the biggest things in the universe. So it is sort of amazing that over all those orders of magnitude, we're much closer to the middle than we are to the edges. So thanks very much for thinking so grandly about the universe and wondering about our place in it. That's exactly what makes physics so much fun. All right, I want to answer one more question, but first let's take another break. When you pop a piece of cheese into your mouth or enjoy a rich spoonful of Greek yogurt, you're probably not thinking about the environmental impact of each and every bite. But the people in the dairy industry are. US Dairy has set themselves some ambitious sustainability goals, including being greenhouse gas neutral by twenty to fifty. 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. Take water, for example, most dairy farms reuse water up to four times the same water cools the milk, cleans equipment, washes the barn, and irrigates the crops. How is US dairy tackling greenhouse gases? Many farms use anaerobic digestors that turn the methane from maneuver into renewable energy that can power farms, towns, and electric cars. So the next time you grab a slice of pizza or lick an ice cream cone, know that dairy farmers and processors around the country are using the latest practices and innovations to provide the nutrient deents dairy products we love with less of an impact. Visit usdairy dot com slash sustainability to learn more.

And we don't know if there's a minimum size to stuff in the universe. It might be that things just get smaller and smaller, that inside the cork there are smaller particles, and inside that there are smaller particles, and inside that there are smaller particles, and it literally just goes on forever. It might be the things can get infinitely small, But I suspect that's not the case, because the universe is quantum mechanical, which means it likes to have discrete units. It likes to have a basis. It likes to be built out of fundamental building blocks. And we don't know what that scale is. We don't know what the size or the smallest thing is. But we suspect that the universe follows these rules of quantum mechanics, and we can make some very bad estimates for how small the smallest thing might be. We take the numbers that we have around, like planks constant and the speed of light and the gravitational constant, and we can and squish those numbers together, multiply them by each other, and divide and do all sorts of stuff, and do we get a number that has distance units. Right, it's just a number that means a distance. Doesn't mean that it is the size of the smallest particle or the scale of space pixels or anything like that. It just means like, hey, this is the number we can get. And we do this kind of estimate because we don't have any better way of understanding what the smallest thing in the universe is. This is like the dumbest thing you can do. Also the only thing we can do at this point, So better to do the dumbest thing than to do nothing. And you put all those numbers together, you get something like ten to the minus thirty five meters, And that suggests that we could continue exploring the universe twenty more orders of magnitude smaller than we have. Right, We've gotten down to like ten to the minus fifteen meters. So there's like twenty more orders of magnitude left to explore in the universe, maybe, we think, but we suspect there might be a minimum size there. On the other side, is there a maximum size of something we can explore? Well, we think that the largest thing in the universe is a supercluster, meaning that after that there isn't any organized structure. We don't think superclusters have gathered together to make super duper clusters, whether those have pulled together to make super duper duper clusters, And that's for a good reason. That's just because gravity hasn't had enough time to organize that stuff. Remember that structure in the universe is organized bottom up. Stars are formed, they come together to make galaxies. Those galaxies come together to make clusters. Those clusters come together to make superclusters, and all this stuff takes time because gravity is pretty weak. So after billions of years it's formed these superclusters which are like just barely held together gravitationally. Will it make super duper clusters in the future, We don't know, because there's an opposing force they have, dark energy. Dark energy is pulling the universe apart. So anything that gravity is not like holding together the way your body holds itself together, or the Earth holds you on it, or the Sun holds the Earth around it will get pulled apart by dark energy. So gravity's had its moment to build structures, and it might be that it's run out of time that anything that's not now gravitationally held together will get torn apart and separated by dark energy. So that suggests that even though the universe itself might be infinite, the biggest thing in the universe might already have been formed. It might be that it MAXs out at ten to the twenty four meters. Now, there's one more aspect to this wonderful question I want to touch on, which is this quantum observer effect. It's true that every time you observe something in the universe, you affect it. You can't measure anything in the universe without interacting with it. Even just looking at something requires that you bounce a photon off of it, because you can't see something unless there are photons coming from that thing to your eyeballs. So there's literally no way to know anything about the universe without interacting with it. And interacting with things changes them. So this is intimate relationship between the observer person making a measurement trying to understand the universe, and the thing that's being observed. There's no way to separate those two things. So if aliens come and they do physics differently, they might see different observations. They will definitely have different ways of thinking about the universe. But it's impossible to try to develop a system of understanding a set of observations that are separate from the person doing the observer. So certainly there is an influence there the way we do observations the way we think about the universe. But I don't see a direct connection between this idea that you affect things when you observe them in the universe and the size of things in the universe. I think we're much more limited just by the life that we can gather to see biggest things in the universe, and by the probes we can use to see the smallest things in the universe. All right, so are we in the middle of everything? Sort of things seem to be more big than they are small at at this point. We don't know if we can drill down smaller to see even smaller things, but we suspect we might have already seen the biggest things in the universe. So it is sort of amazing that over all those orders of magnitude, we're much closer to the middle than we are to the edges. So thanks very much for thinking so grandly about the universe and wondering about our place in it. That's exactly what makes physics so much fun. All right, I want to answer one more question, but first let's take another break. When you pop a piece of cheese into your mouth or enjoy a rich spoonful of Greek yogurt, you're probably not thinking about the environmental impact of each and every bite. But the people in the dairy industry are. US Dairy has set themselves some ambitious sustainability goals, including being greenhouse gas neutral by twenty to fifty. 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. Take water, for example, most dairy farms reuse water up to four times the same water cools the milk, cleans equipment, washes the barn, and irrigates the crops. How is US dairy tackling greenhouse gases? Many farms use anaerobic digestors that turn the methane from maneuver into renewable energy that can power farms, towns, and electric cars. So the next time you grab a slice of pizza or lick an ice cream cone, know that dairy farmers and processors around the country are using the latest practices and innovations to provide the nutrient deents dairy products we love with less of an impact. Visit usdairy dot com slash sustainability to learn more.

There are children, friends, and families walking, riding on paths and the roads every day. Remember they're real people with loved ones who need them to get home safely. Protect our cyclists and pedestrians because they're people too. Go safely, California from the California Office of Traffic Safety and Caltrans.

There are children, friends, and families walking, riding on paths and the roads every day. Remember they're real people with loved ones who need them to get home safely. Protect our cyclists and pedestrians because they're people too. Go safely, California from the California Office of Traffic Safety and Caltrans.

Jump looking for excitement. Jump Casino is here.

Jump looking for excitement. Jump Casino is here.

Play anytime, Play anywhere, Play on the train, play at the store, play at home, Play when you're bored, Play today for your chance to win and get daily bonuses when you log in.

Play anytime, Play anywhere, Play on the train, play at the store, play at home, Play when you're bored, Play today for your chance to win and get daily bonuses when you log in.

So what are you waiting for?

So what are you waiting for?

Don't delay?

Don't delay?

Jump the Casino is free to play.

Jump the Casino is free to play.

Experience social gameplay like never before. Go to Champbuck Casino right now to play hundreds of games, including online slots, bingos, lingo, and more. Live the Champa life at Champacasino dot com pwroup.

Experience social gameplay like never before. Go to Champbuck Casino right now to play hundreds of games, including online slots, bingos, lingo, and more. Live the Champa life at Champacasino dot com pwroup.

No prest necessary.

No prest necessary.

We were prohibited by lossy terms and conditions.

We were prohibited by lossy terms and conditions.

Eh.

Eh.

Plus All right, we're back and we are exploring the universe with our minds. We are wondering about the way things work. We are asking questions and we're hoping to do some answering. So I'm here on my own because Jorge can't be here today, and I'm catching up on listener questions. And remember, if you have a question about the universe and you can't find the answer on Google, then please write to us to questions at Daniel and Jorge dot com. All right, let's get to our last question of the day, which is a super awesome one.

Plus All right, we're back and we are exploring the universe with our minds. We are wondering about the way things work. We are asking questions and we're hoping to do some answering. So I'm here on my own because Jorge can't be here today, and I'm catching up on listener questions. And remember, if you have a question about the universe and you can't find the answer on Google, then please write to us to questions at Daniel and Jorge dot com. All right, let's get to our last question of the day, which is a super awesome one.

Hi, guys, this is Florence in Texas. I have a question about gravity. You've described it before as the weakest force, and you said in fact that it's so weak that when you're picking up an object with a magnet, you're overpowering the entire Earth's gravity.

Hi, guys, this is Florence in Texas. I have a question about gravity. You've described it before as the weakest force, and you said in fact that it's so weak that when you're picking up an object with a magnet, you're overpowering the entire Earth's gravity.

So that's pretty weak.

So that's pretty weak.

My problem is when I start thinking about the objects and a Kuiper belt, they are thirty to fifty astronomical units away, and that's billions and billions of miles, and yet the Sun's gravity is still able to keep them in orbit, and that just gives me the impression that gravity is really strong, not weak. So those two thoughts really don't go together. Would you help me with that? Thank you bye.

My problem is when I start thinking about the objects and a Kuiper belt, they are thirty to fifty astronomical units away, and that's billions and billions of miles, and yet the Sun's gravity is still able to keep them in orbit, and that just gives me the impression that gravity is really strong, not weak. So those two thoughts really don't go together. Would you help me with that? Thank you bye.

Thank you so much for that question, Florence. I love this question and I love the way you phrased it at the end. Those two thoughts don't go together. That's doing physics right there. You are a physicist, Florence, because you are trying to reconcile two ways of thinking about things, because you think, well, the universe has got to make sense, right, and so if I understand idea A and idea B, then I have to somehow be able to bring them together to one holistic idea. And that's exactly what we do in physics. We say, huh, this thing over here works this way. I wonder if that's related to that or there, or how do we get these two things to agree. The whole program of physics is to get a single understanding of the universe. So thank you for doing that exercise. That's exactly what I love seeing. So let's help you bring these two ideas together. So idea number one is that gravity is really really weak. It's the weakest of the forces, and yet somehow it seems to control the structure of the universe. Things orbiting around the Sun, the Sun, orbiting around the center of the galaxy, how is it possible for gravity to be at the same time the weakest force in the universe and the dominant force in the universe. Awesome question, And so first let's review what does it mean when we say gravity is the weakest force in the universe. So we know about a bunch of forces. Forces are things that push and pull. They create little fields so particles can tug on each other without actually touching. We know about electromagnetism, the force that makes like lightning and electricity and photons and stuff. We know about the nuclear weak force, which is actually part of electromagnetism. We call that electroweak, but it's the thing that like can push and pull on nutrinos and it's responsible for radioactive decay of a nucleus. Then there's the strong force that holds the nucleus together and also binds protons and neutrons together using these funky particles called gluons. And then there's gravity, and gravity is the weakest of those forces. So in order, the strong force is well named because it's the strongest force as the most energy held into it. And then there's electromagnetism, which is also a powerful force. Then there's the weak force, which is well named because it's much weaker than the rest of electromagnetism. And the reason it's weak is because the particles that it uses to communicate the force are the w and the z bosons, and they're very massive, so they don't live for very long. This sort of peter out very very quickly compared to the photon. And then there's gravity at the bottom. And you know, if you organize these things to a race, like, the difference between the strong force and electromagnetism and the weak force is really pretty small compared to gravity. Gravity is not even in their league. Gravity is ten to the forty times weaker than all of these other forces. So, for example, if you take two electrons and you put them a centimeter apart, and you ask, well, what's the strength of the electromagnetic force between them they're repelling each other because of their negative charges compared to the gravitational attraction, Well, it's ten to the forty times stronger. Right. Gravity is basically zero in comparison. So that's what we mean when we say that gravity is super duper weak. The example you gave me your question is another excellent one. You can overcome all of the gravity of Earth tugging on a magnet just by using another tiny magnet and a super weak fridge magnet can overpower the gravity of a celestial body, an entire planet. Right, So that's what we mean when we say gravity superduper weak. And yet you're right, it seems to dominate the universe. Right. If you're talking about why does a neptune move around the Sun, well, it's because of the gravity of the Sun. It's not like the Sun has a positive electric charge and Neptune has a negative electric charge and it's using that electromagnetic force to hold Neptune in place. And it's definitely not the strong force of the weak force. It's gravity. So why is that? And the short answer is because gravity cannot be neutralized. It can't be balanced. All objects have mass and those objects feel gravity. You can't be neutralized the way you can, for example, with electromagnetism. Think about, for example, what would happen if the Earth had an overall negative charge and the Sun had an overall positive charge. That would be an enormous force that would be crazy strong, much stronger than the Sun's gravity on the Earth. And what would happen is that particles would very quickly get transmitted between the Earth and the Sun to neutralize that force. As the force would be so powerful that it would pull negative particles out of the Earth and positive particles out of the Sun, the force itself would neutralize itself, right, it would balance itself out. The force acts on charged particles and moves them around in a way to neutralize itself. This is, for example, why you can't get a cell phone signal inside an elevator, because a cell phone signal is electromagnetic radiation. It moves particles around, and if it hits the wall of the elevator, it moves those particles around in order to balance out to cancel out the electromagnetic radiation. So electromagnetism, because it has a plus and a minus, it can be balanced out. And that's also true for the other forces. Most of the things in the universe that are made out of the strong force, that are held together by the strong force proton or neutron have no overall strong charge.