Daniel and Jorge Explain the UniverseListener Questions 42: Life, the Universe and Ghosts!
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Hey, Daniel, do you believe in ghosts?
You know?
I do always say that there's plenty we don't understand about the universe.
But does that mean that it's supernatural?
Well, you know, if we can describe it with physics, then it's just part of nature. It's just natural.
What could there be physics that exists out there but that we can't describe?
Hmmm, like some kind of superphysics?
Yeah, how does that make you a superphysicist?
I'd gladly take a promotion to a superphysicist with a super salary.
Wait, would that mean that you sort of take off your glasses and open up your shirt and you're actually a superhero.
Super Daniel doing superphysics sounds super awesome.
Hi.
I'm Hora mccartoonist and the author of Oliver's Great Big Universe.
Hi, I'm Daniel. I'm a particle physicist and a professor at UC Irvine. But I'm not doing it for the money.
Wait, what, but you aren't getting paid though, to be a physicist, right.
Well, I mean, I'm not like turning down the checks out of principle or something crazy.
So you are doing it for money, just not for the money.
I am getting paid. Do not worry. But all of my students who graduate with physics PhDs and go off to work for Google and their competitors are getting paid a lot more than I am.
But you're still getting a pretty super salary, right though, Right, I mean, I know what you see professors make. It's pretty super money. And it's just not the money. It's more of a generic money.
Yeah, it's more like a money than the money. But you're right, I've got no complaints. I got a pretty sweet gig over here, a super gig apparently.
But anyways, Welcome to our podcast, Daniel and Jorge Explain the Universe, a production of iHeartRadio.
In which we cash in on our passion and your passion for understanding the universe. We hope that the whole universe can be described in terms of crazy mathematical models that predict everything that could happen in this universe, and our job on the podcast is to take those mysterious mathematical models and explain all of them to you.
Yes, because it is a pretty mysterious and eerie universe that sometimes seems supernatural, but that somehow a science has been able to describe so far with models and data and experiments.
Yeah, and it's a fascinating transition where originally we just have sort of like mythological stories to describe the things that we see, you know, like lightning and weather, and later on we find explanations for those things. We can make sense of them in sort of mechanistic or even random quantum mechanical processes that describe them the show us that they're following rules and laws and not just like the whims of deities. But there's plenty of other stuff out there in the universe we haven't yet explained, and so one can wonder will science ever explain them or not?
Wait, are you saying that things like dark matter and dark energy are our modern mythology? Is there a god of dark matter or god?
Is I really hope that there's physics of dark matter instead of gods and goddesses of dark matter, because that would be pretty hard to understand. But so far we don't have an explanation for these things, right, and so we just have to like hope that science will one day figure it out, because we're projecting from all those times that science has figured things out. But you know, that's not exactly a guarantee. That doesn't mean that science will always figure things out. Philosophically, we don't have a promise that the universe can always be described by our mathematical stories.
Is there's a fine line between mythology and methodology.
I don't know. I think this is a pretty bright line between those two things, even though they do sound very similar.
What if you do mythology very methodolically, very carefully.
I don't know. That sounds like doing astronomy very astrologically. It sounds similar, but it's not really the same thing.
Well, maybe you make more money if you were an astrologer.
Oh almost absolutely, that's true.
I hear. They have good benefits.
They just don't have big telescopes. It's the problem.
But anyways, it is a pretty interesting and mysterious universe, and we still have a lot of questions about it. It's not just physicists and scientists who ask these questions about how things are and why things are the way they are, but it's also everyday people going about their everyday lives, asking all the big questions.
That's right. It's not just the job of scientists to figure out how the universe works, to think about the ways that science can describe tiny little crawling creatures and swarming quantum particles or huge swirling black holes. It's the job of everybody out there to think about how this works, to apply our human curiosity to the greatest puzzle of all time.
Wait, did you have to get paid for something to count as a job? My son makes that distinction all the time. I might gets your job to take out the dishes from the dishwasher. You said, well, technically am I getting paid?
I think of it more like our role. You know, some of us do get paid because it's our livelihood. But for everybody else, your job is to support the larger endeavor of science just by being curious, just by wondering how things work and wanting to know the answer. You know, the institution of science is quite literally powered by your curiosity. Because you're a curious person and you think this is a good idea, you elect politicians who vote to use your taxes to support the institution of science.
That's right. It's your curiosity and also your taxes or some of your taxes, or a very small fraction of your taxes.
Unfortunately, that's right, your taxes and our facts is I suppose.
It's tactual and factual, and they're vote right, Like how you vote makes a big difference about how what society prioritizes and what kind of science and if science gets funded.
Yeah, that's exactly right, Which is one reason why this podcast's mission is to fan the flames of curiosity, to share our personal joy and wonder the incredible nature of the universe and this incredible cosmic mystery we all share of figuring it all out. Yep.
And people are curious and they have questions, and sometimes on this podcast we like to answer those questions.
We do love to answer your questions. This is not just a one way medium where you're listening to us talk. We want to hear from you. We say it all the time on the podcast, but we mean it. Please write to us with your questions to questions at Danielandjorge dot com. We answer all of them because we think it's important that you have somebody to ask questions of, somebody you can talk to about your curiosity about the universe.
So to the on the podcast will be tackling listener questions number forty two, the answer to life, liberty, and the pursuit of happiness right.
Life, the universe and everything, including maybe the supernatural.
Whoa a teaser spoiler alert.
I'm just trying to cash in on all those podcasts that are higher ranked than us and just deal with like Sasquatch, Bigfoot, and like ancient aliens.
Oh why haven't we done that the science of Sasquatch.
That would be a very short episode, or.
Is that more of any episode? It's biology.
Yeah, maybe that's a good idea.
But we have some amazing questions here today about the supernatural, about neutrinos and neutron stars, and also about how to make space. This is also yeah life organization podcast premit, like how to get yourself organized.
That's right, you can make space in your house by using neutrino beams that also capture ghosts. We're going to tie it all.
Together so you only do experiments that really bring you joy. Doesn't bring joy to you get him out of the list.
Oh man, we do a lot less science in that case.
So let's jump right in and so a first question comes from Brendan.
We've all heard stories about ghosts, telekinesis, remote viewing, and things like that, and I was wondering, if we can just assume that those are real for a second, how could they work. I think it'd be really awesome to hear your opinions.
Thank you.
Interesting question. Brandon seems to be asking, like, if all these stories about ghosts and esp and being able to move things with your mind, if they were real, how would they work from a physics perspective?
Yeah? I love this question because he's not like doubting these observations. He's doing the science of it. He's like, all right, let's see if we can construct an explanation, not some metaphysical supernatural story that violates physics, but let's see if we can bring it into the fold of science. Right, Let's let's see if we can come up with a way to explain this stuff without breaking physics.
Yeah, like, if maybe you do see a go someday to be there, you're crazy? Or is there an actual explanation that someone could come up with?
That's right? And usual disclaimer we are not offering psychological advice on this podcast. Do not follow our health advice in any.
Regards, or financial or career advice apparently, or legal or any kind of advice. I guess we're just talking signs here. But yeah, let's maybe start with some of the situations that he mentioned, for example, remote viewing, Like if you could see into the future maybe, or you can see what's happening on the other side of the world with your mind. How would that maybe work.
Yeah, this one is pretty awesome. I mean remote viewing. I had to look this up to see exactly what it meant. And it's the practice of seeking impressions about a distant or unseen subject. So imagine, for example, you're in your house in California and you want to know, like what's going on in the oval office right now, You like close your eyes and you concentrate and you get a vision for what's happening there. Or you want to know, like what's happening on the surface of the moon, for example. So remote viewing would allow you to see something really far away.
Like FaceTime without the iPhone exactly.
And something that's really fascinating about this one idea is that it's pre technology, right. People have had this idea of remote viewing for thousands of years, but now because of technology, it's not really even that special. Like, as you say, everybody has a device in their pocket that you could use to see what's going on on the other side of the world. It's not really that complicated. We have used physics to basically create this ability for almost everybody.
Well do you think Brendan meant like, right, you can see things happening right now somewhere else or maybe in the past, or maybe in the future.
I think Brendan is probably talking about without iPhones, like just using your mind. Somehow you can gather this information using something other than the Internet. I think probably that's what Brendan is imagining, not just facetiming your grandma.
Hmmm, well, I guess you can always use letters, but they still have mail, right, they do still have mail, and in fact, your grandma would probably prefer that.
And so physics has some things to say about this, right, Like, first of all, it would be very hard for it to be instantaneous, you know, for you see what's happening on the other side of the planet, like literally right now with zero time delay. Would require information to get from there to here with no time gap, and that would violate relativity unless, of course, you use one of the loopholes like warp drives or wormholes.
You mean, like you could open maybe a wormhole between here and the other side of the world, and then the information would flow from there to hear faster than light wood in regular space.
Yeah, exactly. If you opened a wormhole between here and China, then you could pass information between here and there faster than an email would get from here to China, and email travels essentially at the speed of light minus of course all the time for switching in computation.
So you're saying it is possible to see things with your mind that are happening somewhere else, or that happen a few milliseconds before somewhere else.
Physics doesn't rule that out. You know, you have to create a worm which we don't know how to do, and we don't know if wormholes are real, and then that wormhole would have to be stable enough for you to see that stuff. And to keep wormholes open, you need some sort of like exotic negatively charged matter that we don't know if it exists, and you'd have to do that somehow, like inside your brain without also like liquefying your brain, which seems pretty challenging.
Like somehow your brain, the cells in your brain would have to be capable of like absorbing these signals and interpreting them.
Yeah, exactly creating that wormhole, understanding it, and surviving it. That all seems pretty challenging, But I can't tell you that. Physics says it's impossible.
All right, So that's a check for the supernatural here. What about telekinesis, the idea of moving things with your mind that are far away or maybe not so far away, but that are not connected to you.
Yeah, telekinesis is also really fascinatingly connected to ideas in physics. Telekinesis is essentially moving something with your brain, as you said, And you know, for a long time there was a puzzle in physics, something called action at a distance, like if two electrons are separated in space, they can still push on each other. How does that happen? It was a big puzzle for a long time, you know, without actually touching, how do two things push on each other? And now, of course we have a solution to that. We know that electrons push on each other using fields that they create, so around. Each electron is a field, and one electron feels the field of the other electron, or alternatively, you can think about it as them exchanging virtual photons, which is fundamentally the same. So physics has a way for two things to push and pull on each other even when they're not touching.
Well, I think in physics, basically everything pulls and pushes on each other without touching, because nothing really touches in physics, right, everything is a point particle, which means that they never really touch.
Well, you can either say nothing really touches, or you can say that's what touching is, and so you kind of are touching at a distance because you know, nothing really has these surfaces. I think is what you're trying to get out when you say they're point particles. There aren't these surfaces that touch, and there some sort of like deep tactile force. In the end, it's just the four fundamental forces and they all operate this way. So that's sort of what touching is. And my point is you can do it at a distance, right, You can pull on something from far away if you can create the right kinds of fields. So you want to levitate your coffee from across the room to you. If you could somehow create the right electromagnetic fields, you could do that because your coffee is made of charged.
Particles, right, Because I guess everything, as we don't understanding, in physics, everything acts at a distance.
Right, Everything acts at a distance.
Yes, so everything is telikinesis. Right, There's no non there's no regular kinesis in physics. There's only telekinesis.
That makes it sound like everything is just like brains thinking about stuff. But yes, everything is action at a distance. In physics, everything is at a distance.
But I guess it would be hard. I wonder to lift the coffee mog using the electromagnetic force because the coffee mug is sort of electrically neutral, right, unless you say, like, unless you like supercharge your cuffee mug.
Yeah, the coffee mug is typically neutral, and you don't want to have to like, you know, rub static electricity on it to move it across the room. But it is made out of charged particles, and so if you wove your electromagnetic fields in just the right way, then I think you could transfer momentum to it.
I guess if maybe, like the cuffee mug was a giant magnet for example, or are you thinking it could be done in a regular mug?
I'm thinking, if we're being crazy here and there's no limit to your technology, if you could craft the electromagnetic fields in a way that you like, push the positive particles one way with one field and push the negative particles with another field, then you could move them together across the room.
Wait, what do you mean, like have two kinds of electromic gutty forces?
Positive particles and negative particles are not literally on top of each other. So if you created an electromagnetic field that was highly variable in distance, it was like sculpted to perfectly match the shape of your mug and the location of all the positive negativity charged particles, then you could give it a coherent push in the direction that you wanted.
Whoa, you could single out the electrons in a coffee mug and single out the positive charges separately and somehow shoot a force at each one.
Yeah. I like how we're talking about telekinesis and your tone is like, Daniel, you're being unrealistic.
Well we're trying to go on with a real answer, right, Yeah, I mean it's theoretically possible. I guess you could single out the trillions of electrons and a mug, but to do it with your mind, I wonder if that would maybe exceed the computational processing of your.
Brain almost certainly. I'm not saying that would be easy, but I'm just reaching for a way to move your mug across the room, and I'm thinking technically, theoretically that might be possible.
It sounds easier to just ask your sun to bring it.
And pay them for it, I hope. But there's another issue there with your brain, which is if physics says momentum is conserved, so if you push on an object, there's an equal and opposite force that pushes back. You know, like if you fire a rifle, there's a recoil. So if you're transferring momentum using your brain to the mug, then this gonna be some momentum also on your brain. Right, So your brain pushes on an object, basically that object is also pushing on your brain, and that could be quite uncomfortable.
I guess, yeah, Like if you want to throw them all across the room, then you kind of need you would feel that forcing with your head. But if I guess, if you're just moving it like within our reach on top of a table. You probably wouldn't feel a huge amount of force on your brain, would you. I mean, your brain is pretty heavy too.
M m. But if you're like magneto and you're lifting like a steam engine or something, that's going to looquify your brain, also, that.
Is pretty mind blowing if Itgnito exists. So that's a rule. Well, okay, now let's get to the juicy one. What about ghosts.
Yeah, you know, I thought about this for a while, and I guess it depends on what you mean by ghosts. If ghosts are just like apparitions that appear human like and make human like noises, then sure than anything could appear to be human. But if you're talking about like actual spirits of dead people, like the continuing thought processes of their brains after their bodies have ceased to live and maybe even composed, it's hard for me to understand how that's possible. I mean, there is quantum information, and quantum information is not destroyed, and so technically the quantum information of those people lives on in the universe, But that doesn't mean that it's coherent in a way that could like speak to you and answer questions.
Wait.
Wait, I feel like there's two things here going on. First of all, it's like, can things be ghostly? Like, can things kind of be in this world but not really be in this world? Or can things you know, sort of appear to you and go through walls and things like that? And second is, can your spirit or your consciousness or what makes you somehow live on after you die, or be transformed into something that is ghostly?
Oh?
I see, well, things being ghostly? Yeah, that's easy because we basically live in a ghostly world. I mean, surrounding us are all sorts of particles that are transparent to us, and we're transparent to them, neutrinos, dark matter, other stuff we haven't even detected. So there's lots of stuff facing through our walls and through us and through our lives all the time that we don't detect. Yeah.
In fact, there's the idea out there that maybe dark matter is complicated and could be forming structures and maybe you know, biological things and maybe even sort of like sentient dark matter beings kind of living in our universe but us never knowing they're there.
That's certainly possible. Would you be able to see them and detect them as ghosts. That's harder for me to understand. The reason these things are ghostly is because they almost never interact with us, and they do, it wouldn't be in some sort of coherent way you'd see like one particle here in one particle there.
But they do affect our world in some ways, right, Like, for example, dark matter affects us gravitationally, and neutrinos affects us through the weak force.
Right, dark matter does affect us gravitationally, but only on really big scales, like we can't even detect the effect of dark matter on our solar system. We have super high precision measurements of like the orbit of Jupiter, and we can totally ignore dark matter when we do those calculations because it's spread so thin and it's so dilute that it has basically no impact on anything local. So you're not going to see like a dark matter ghost.
Well sort of, maybe I wonder this is recording nuts here? Could it dark matter being somehow use their brain to focus gravitational force onto like particular molecules or atoms or particles, just like we were moving the mug earlier. Could they do telekinesis using gravity on us.
Perhaps they could remember, though, that gravity is the weakest force in the universe by a lot, So to have any sort of gravitational effect on something, you need a very very large mass. And there just isn't that much dark matter around. Like in the volume of the Earth is about one squirrel's worth of dark matter, So one squirrel's worth of gravity is about the biggest impact dark matter could have on Earth.
So I think you're saying there is ghostly matter in the universe, matter that exists out there that could be organized into things. But then if it does exist, it'd be hard for it to interact with us, and so it'd be hard for us to ever see it.
Yeah, exactly, And you certainly wouldn't see it as your grumpy uncle come back to life to haunt your living room.
But what if I take my grumpy uncle and he's a billionaire and he puts all his money into like downloading his consciousness or scanning his brain, or creating an AI that replicates his consciousness that he uses his money for to create a neutrino or dark matter version of himself.
Wow, your family's pretty crazy, That's what I gotta say about that. It's certainly technically possible to do a quantum copy of your information into some storage medium, and so in principle, perhaps in the future one could upload yourself into the cloud. I don't know about creating a neutrino version of yourself, though, again neutrino is almost impossible to.
Interact with, or maybe like a dark matter version of yourself, but.
We don't even know what dark matter is, if it's made of particles, how to interact with it, if he could do anything but gravity. I suppose the computer version of your grumpy uncle could be hooked up to like a projector which creates, you know, holographic image of your uncle, and that way could be sort of like a ghost.
Oh there you go, a dark matter projector using a quantum copy of your uncle.
It doesn't even have to be dark matter, just like a normal matter projector making a hologram.
Right, Oh, yeah, there you go. You don't even need dark matter.
Yeah, so I suppose in that way a ghost could exist, a physics ghost.
All right, Well, hopefully I can convince my uncle to leave the money to me rather than to create a holograms of himself.
Just send your son over there to do a bunch of chores and then send them a bill.
There you go. There's always a way in physics. All right, let's get into our other questions. We have awesome questions about neutrinos and neutron stars and about the nature and origin of space itself, so we'll dig into those. But first let's take a quick break.
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Right, we're answering listener questions here today, and this is our forty second episode where we do that forty two is a pretty significant number, isn't it?
Forty two is a big deal. It's a running joke in my family since we read The Hitchhiker's Guide to the Galaxy several years ago.
What's the running joke.
I guess we just take special joy in seeing the number forty two appear all over the place.
M It is sort of an interesting number, right, It's six times seven.
What's interesting about that?
I don't know. It's take an odd number of times on even number. I don't know.
I do wonder sometimes what made Douglas added to choose that number and not, you know, thirty nine or or one hundred and forty one or something.
Else, maybe because it's six ninety seven, as if.
That's an answer somehow, like the way you say that, as if it answers the question.
Isn't it Jackie Robinson's number two?
Yeah? Could be, I don't know.
Anyways, we're answering questions from listeners because everyone has questions and we like to answer them here on the podcast sometimes, and so our second question here today is about neutrinos and neutron stars.
You've mentioned that a neutrino can penetrate a light year of lead, But how much neutron star matter can a neutrino penetrate? Could we study a neutron star that is paired with a main sequence star using the neutrinos from the main sequence star.
Right, an interesting question here about neutrinos and neutron stars. There's a lot to unpack here, but basically, neutrinos are ghostly, as we just talked about earlier, and neutron stars are super dance, and so I think they're asking what happens if you put them together.
Yeah, it's a really great question, not just because it's seeks to understand, like neutrino's a deeper level, but it's got an idea in it, right, an idea to help us probe the interior of neutron stars. We'd love to know what's going on in these crazy, super dense regions of space, these hot, squeezed relics at the end of stars, and so it's a cool idea to imagine like shooting a beam of neutrinos through it and seeing what happens.
So we talked about what a neutrino is. There are particles that exist out dur in the universe. They get made by the sound. There's a whole bunch of them going through us right now, but they don't interact with things using the electromagnetic force. They seem to only interact using the weak force, right.
That's right. Neutrinos have no electric charge, and so they don't interact with photons, and they don't interact at all using electromagnetism, which is really the strongest force that people feel in their everyday lives, you know, lightning and magnetism and the chemical bonds that hold things together. That's all electromagnetism. Neutrinos only feel the weak force, which is much much weaker than electromagnetics. And so that's why we often say that neutrinos can pass through like a wall of lead that's a light year thick without interacting. And it's not because they're like wiggling around those lead particles. It's not because they're super duper small. It's because they just don't interact very often. Every time a neutrino comes near an atom, it like rolls a die, but that die is like a billion sided dye, and only if it comes up one number, one specific number, does the neutrino interact.
And so I guess the idea is to pair that idea with the idea of a neutron star. So, now, Daniel, what is a neutron star.
A neutron star is the endpoint of a big star that's burned and burned and burned. Remember, most stars start out as overwhelmingly hydrogen, but gravity squeezes them down and ignites fusion at their core, which makes heavier and heavier elements. You take hydrogen, mechlium, you squeeze the helium together, you can make carbon. You can make heavier stuff all the way up to iron if you have a really big hot star. But at the end of its life, a star will implode or explode, depending exactly on the mass that it has, and usually leave behind a very hot, dense relic the leftover bits of the fusion that it couldn't burn. And so a neutron star is an extraordinarily dense object. They usually have something like the mass of the Sun but a radius of like ten kilometers. So you're talking about like taking the Sun and squeezing it down to the size of Manhattan after putting it in a blender. And that's a crazy dense object.
Yeah, we've talked about how it's basically like the bestest thing you can get in the universe almost before you get a black hole.
Yeah, gravity is trying to squeeze it down even further, but there's this degeneracy pressure. The quantum effects inside the neutron star are still able to resist gravity. If you add a little bit more mass, then the thing will collapse into a black hole, but it's still resistant. So it's like the last stronghold against gravity's ultimate victory.
And I think part of the reason is that it is made out of neutrons, right, so they don't repel each other electromagnetically, they have almost no reason not to just fall into themselves, not to get crushed together.
Except the neutrons are fermions. There's spin one half particles, which means that like electrons, they can't overlap too much. They can't be in the same quantum state, so they resist being pushed together. So that's one way in which a neutron star is preventing itself from collapsing into a black hole. There's this degeneracy pressure. The neutrons don't want to be in the same quantum state.
Right right. But I think what I meant was, like, the reason I don't fall to the center of the Earth is because my electrons are being repelled by the electrons of the floor.
Yeah, that's right, and that's not happening inside neutron stars because it's all neutral. It's all neutral electromagnetically. But you know, we also don't think that it's really still neutrons at the core of neutron stars. We think that the strong force is probably doing something crazy, something else that you know, the distinction between the neutrons is blurring, and all the quarks inside them are really interacting with each other. We have a whole episode about what's going on the heart of neutron stars, but the bottom line is that we don't know, and it's probably something super fascinating that would tell us something knew about the way the strong force works and the way that it competes with gravity. So super interesting, almost like learning about what's inside a black hole.
Okay, so now the question is we have the the desest thing in the universe before a black hole, and we have something that doesn't really like to interact with anything. What happens is if you shoot a nutrino into a neutron start.
Yeah, so this is really a question about transparency. We recently did an episode all about transparency and photons, and the short version of that is that it depends on the interaction. You have to think about it from a particle physics point of view. Shoot the particle through is it going to interact with the stuff? And when you're talking about transparency for normal materials, like why can light go through air and why can it go through glass but it can't go through steel or can't go through your hand, then again it's depending on those interactions. You're thinking about whether the photon can be absorbed by the electrons in your body. Sometimes those electrons can absorb that photon because there's an energy level available for them to get to, and sometimes they can't. Photon just flies through and ignores the material. So that's why photons can go through matter sometimes if the energy states aren't arranged in a way that the photon can absorb it. So now when we think about a neutrino going through a neutron star, we have to ask similar questions like how can the neutrino interact with that material and is there a sort of a valid particle physics process that would allow that to happen.
Well, as far as we know, neutrinos are neutral, so they don't feel the electromagnetic force, but they do feel the weak force. Right, do they feel the strong force as well or only the weak force?
If they have mass, then they feel gravity, and we do think that they have masks, though we can't measure it very precisely, but their mass, if they have any, is very very small, and so gravity is probably almost irrelevant for neutrinos. So really it just comes down to the weak force. So if you're a neutrino and you're approaching a neutron star it's filled with neutrons, then what you can do is interact with one of the quarks inside the neutron. For example, you can take a down quark and you can convert it to an upquarkct acting with it because those quarks also feel the weak force. This is called reverse beta decay. Sentially, a neutrino hits a neutron, turns it into a proton, and then you can an electron out the other side.
So there is a process for a nutrina to interact with a quark, is what you're saying exactly.
It can either do this convert a nucleon from a neutron to a proton, or it could just kick one of the nucleons. The reason it's got two options is because there's sort of two versions of the photon for the weak force. Electromagnetism just has the photon, but the weak force has the W and the Z, and the neutrino can use either one. It can either use a Z to sort of give a kick to one of the nucleons, or it can use the W to convert one of the nucleons from a neutron to a proton.
I'm not sure I follow all the mechanics, but I think what I'm saying is if I shoot a natrino into a neutron start, it is possible for to interact with a quark, in which case it would get stopped by the quark. Basically right, it'd be like hitting the quark.
It wouldn't necessarily get stopped. It might get scattered, it might like change direction, or it might even be absorbed and get converted into an electron.
But it wouldn't go through as the main point.
It might go through. There's a possibility for a neutrino to interact with these things, but the probability of it happening depends on a lot of different factors. It still has to roll that big die and come up with the right number, but sort of the number of sides of that dye depends on a few things. One of the things that depends on is the energy of the neutrino. If the neutrino is higher energy, if it's moving faster, then it has a higher probability to interact with the material. So a faster moving neutrino is more likely to bump into one of these nucleons, and a slower moving neutrino is less likely.
But if it does interag then it's sort of like it's it wouldn't count as going through unscathed.
Right, That's right. Any interaction doesn't count as going through unscathed. So it depends on two things. It depends on the neutrino's energy, and that's actually interesting. It's because of relativity. If you're moving really really fast, then space in front of you is looking contracted, which means that you're squeezing this already very dense neutron star. You're squeezing it down even further so it looks even denser. So you like length contract the neutron star into something even smaller, which makes you have a higher probability of interacting with it. So higher energy neutrinos, faster neutrinos have a bigger probability of being absorbed by the neutron star or being bent by it.
So the neutron star is super dense. That means that it basically, as a neutrinu's trying to go through it, there are a lot of possibilities or it's very likely for it to interact with a quirk, which means it wouldn't go through necessarily. Have you done the math like how far can a neutrino penetrate?
So it did sit down to do this calculation, and it turns out it also really depends very strongly on the temperature of the neutron star. So neutron stars, remember there are these degenerate states, which means that like all the quantum states are filled up, so cold neutron star has all those neutrons filling up the lowest energy states, and that's a problem for interaction because if you're coming through your neutrino and you try to bump into one of those neutrons, there's sort of no available state for it to get to. Like the ladder above, it is all filled, so it can't interact with the neutrino because there's nowhere for it to go. On a hotter neutron star, some of those states are not totally filled because the neutrons are moving around they have higher energy, so there's open spots in the ladder, and if a neutrino comes by, it can interact with that neutron because there's a spot for the neutron to jump up to. So for hotter neutron stars, they're more likely to interact. So you have a high energy neutrino hitting a very hot neutron star, than it can interact.
Which means it wouldn't penetrate very.
Much exactly, which is sort of cool because it means that neutron stars start out opaque to neutrinos, and as they cool, they become transparent. And there's this threshold at like ten to the ten degrees kelvin that's like ten billion kelvin that neutron stars essentially become completely transparent to neutrinos. Do neutron stars Neutron stars do cool absolutely very slowly over time, they're still radiating out heat. They're not fusing, right, they're not creating more energy at their cores, but there's still hot lumps of matter, and hot lumps of matter do radiate out photons.
I guess. Maybe another question is, if they are really close to being black holes, wouldn't they also bend the space around them and somehow trap neutrinos that way, or at least bend their path.
Yeah, that's a great question. Neutron stars are definitely dense enough to have very strong gravitational effects, you know. That's why they're almost perfectly spherical. Like you try to make a mountain on the surface of a neutron star, it will get flattened. The tallest mountain on the surface of a neutron star is like a millimeter high, So it's very intense gravity. But there's no event horizon, Right, that's the difference between something that's a black hole and something that's not so. In principle, photons and even neutrinos created at the heart of a neutron star can still escape because there's no event horizon. But you're right, it will get distorted, get like bent around in lots of different directions.
Right. So I guess if you shoot neutrino's at entron star, it would only maybe go through on scathe if you shoot it at the exact center of the neutron star, I wonder. And also if it has, as you said, the right energy to it, and the neutron star is cool enough, then it will go through. But otherwise it might get deflected, or it might hit one of the quarks in the star.
Exactly, And here we've mostly focused on the hot mess that's at the heart of the neutron star. The densest region, the crust of the neutron star, like the surface of it is not nearly as dense.
All right, Well, I think that's the answer to the question here. How much can neutrinos penetrate a neutron star. It sounds like the answer is it depends on the speed of the neutrino and also the temperature of the neutron star. But it sounds like if it's the right conditions, then it wouldn't penetrate very far, or at least it would maybe get bent for sure, almost definitely by the gravity of the neutron star.
M hm, which means something cool. It means that Doug is right that in principle, you could use a beam of neutrinos that's going through a very hot neutron star to learn something about what's inside that neutron star based on how those neutrinos are bent or stopped.
Mmm, like an X ray kind of like you could shoot some neutrinos at intrust star, have a detector in the back of it, and you can kind of get an X ray of the neutron star.
Yeah, or if there's a bright star behind the neutron star, it's already doing that for us, shooting the neutrinos at us. So we just got to find those and use it as a way to X ray that neutron star.
Maybe my rich uncle will pay for that detector. We'll see, we'll see what we can convince them to do. All right, let's get to our last question here, and it's about space and how it gets made. So let's dig into that. But first, let's take another quick break.
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All Right, we're answering questions from listeners. We've answered awesome questions about ghosts, telikinesis the supernatural or I guess how we can make the super and natural natural? And we've answered questions about neutrinos and some of the densest objects in the universe. Now we have our last question here today, and it comes from a six year old named James. Hi Danyon, Hi, my name's change and I just turned six And how does space get made? Awesome question?
Thank you James, and happy birthday.
Do you think he's getting paid to be a physicist.
I think he's got a future career.
Ahead of him for sure, getting paid in cereal and ice cream.
I wonder if James's question is why does space exist? Like how did it get made in the beginning originally, or if he's asking about how space expands, how we get more space?
What are the words he used?
He says, I'm wondering about how space gets made.
Well, let's see he used the words I wonder how space gets made. So it sounds like it's in the present tense right, like how are space being made? Right now?
Yeah? I guess he's sort of asking for a recipe, like, Hey, I want to make more space? What do I do?
Which I guess is maybe the same question as if you put in the past, as which is how did it? Space?
Can be like when you go to somebody's house and they serve a really delicious dessert and you're like, wow, how does that pie get made?
That seems like a rud question.
Oh, that's very polite. It's saying I want more of that thing you made.
Well, we could all use a little bit more space, for sure, especially down here in southern California. We're space set a premium. And the question is a physical one. I guess about physics, not just like how do you make more room in your house?
Yeah, I think it's about the nature of space itself. Right, when you take everything out of the universe, you strip it of all of its particles and its energy. We're talking about this stuff that everything is existing in. How does that itself get made?
Yeah?
Or maybe James has a sibling and he's wondering when he has to stop sharing a room with that sibling, how can I get more space?
Well, we're spending a lot of time joking around about the question and not answering it. And one reason is that we really just don't have any good answers. You know. One of the deepest mysteries in modern physics is even like what is space anyway? We still don't even really understand. We know that we need to move beyond sort of ancient notions of space from like Newton that space is absolute like a backdrop of the universe, but we don't really have a great idea for what space actually is.
Well, I feel like it's sort of been one of the biggest mind blowing moments in humanity in the last one hundred years to realize that the space is being made right now, Like there's more space today than there was yesterday in the universe.
Yeah. About one hundred years ago, people thought that the universe was static. There was just a bunch of stars hanging out in space, and it was that way, it had always been that way. Then we learned that the universe was expanding, and Einstein's general relativity actually accommodates that very very nicely, even without later confusion about accelerating expansion or decelerating expansion. Just the idea that the universe was expanding at all meant that space itself was increasing, right, not just stuff moving through space, but actual increase in the amount of space.
Yeah, space is being made right now. And I guess the question is, like how do you make space or like where does space come from?
We don't know the answer to that. We know that it is happening, and we can describe it mathematically, and we have some pretty good handles on like when space will contract and when space will expand, But we don't know what space is, so we don't have really any insight into that process itself. We know that the universe is doing it and along the way breaking some rules we used to think we're fundamental, Like when the universe makes space, it makes a new chunk of space that comes with new quantum fields which has non zero energy in them, which means, in principle, is increasing the total energy of the universe. So making more space involves creating energy from nothing, which is not something we know how to do. So yeah, we really don't have any idea for how this works.
I think you're saying that, like all we know right now is that there is some space today there in between the stars that we can see, and tomorrow there's more space, but there's going to be more space between those stars. That's kind of how we see it, Like, that's just what we can observe.
That's what we observe, and it's not like we're totally clueless, right, General relativity gives us a mathematical description for that expansion. We can describe it, we can even predict it that we can explain the history of it, but like the deep underlying mechanism of that is not something that we understand at all, because again we don't even know what the thing itself is. We have this sort of high level mathematical story from Einstein, but we don't understand the microphysics of it, like how does space come together? What are the essential bits of it? We don't even know if space itself is fundamental, Like could you have a universe without space? Or is space like a prerequisite a minimum condition for even having a universe. We don't even know the answer to that totally basic question about the nature of space.
You mean, like we don't know what space is in the first place.
Right, Yeah, and so we don't know if you have to have it right, maybe there's a place where space.
Isn't now maybe to answer then James's question, like how does space get made? Like what does that process look like? I wonder if maybe that's one of the questions he's wondering about, Like is space being created smoothly sort of like you know, like a balloon being inflated smoothly, or does it get created in chunks or in steps?
What do you think Another great question I would love to have the answer to it depends on whether space is smooth and continuous or quantum mechanical, like in Einstein's description of general relativity, space is continuous. Between any two points is an infinite number of steps, and you can continue to divide those as long as you'd like. Quantum mechanical views of space say that's not true, that there must be like space pixels, that everything is discrete. And if that's true, then as the universe expands, then you pop out new countable numbers of space pixels, right, like one more and then one another one. You can't have like one and a half more space pixels. So whether it's continuous or depends on whether space is sort of classical and smooth or quantum mechanical and discrete. And we don't know the answer to that either.
One of their other possibilities for like explaining what we see out there, is it possible we're shrinking and space is the same where we're just shrinking. Just seems like space is getting bigger.
That's absolutely possible. Remember the expansion of space absolutely Yeah.
I was just pulling that out of that yeah, out of my pocket. There.
The expansion of space is relative it's a scale factor we measure as space expands relative to its size in the past, and it's mathematically equivalent to say, space is expanding and stuff is staying the same size, or space is staying the same size and everything is shrinking. You could never tell the difference between those two things, because they would only be different relative to some external ruler which doesn't exist.
Wait, what does that even mean? Now? I was literally just making up words, but it sounds like it's a real possibility. What does that mean? Like, we're getting smaller relative to like, let's say, like us and our sun here, and there's another star in the sky. We're getting smaller. Would that necessarily make the space between us bigger?
Imagine the expanding universe, right your usual picture, everything's staying the same size and getting further and further apart, and we think that's probably infinite. But just imagine like a chunk of it. And now, instead of allowing that to get bigger and bigger, try holding it to be the same size, so as time goes on, you don't allow it to expand in order to keep all the relationships the same. You can instead just squeeze everything down. So like now, you're holding that chunk of space and you're watching it, and instead of it getting bigger, so things get further apart, everything just shrinks inside of it, so it gets smaller and smaller. So then the beings on those little planets, they measure the distances to be larger because their rulers.
Are shrinking, even the ruler between like here and there.
Yes, everything within it shrinks. And so if you don't have an external metric, if you're not that alien outside, you know, running the simulation a whole holding that chunk of space, you can't tell the difference. If you're inside the universe, you can't tell the difference between stuff shrinking and space staying the same, or everything's staying the same size and space increasing.
And that would apply even to things like light. Right Like, as the universe expands, we see light being stretched. Do that mean the light itself the photons are shrinking or the speed of light is shrinking.
Everything stays same relative to that ruler, But those rulers are shrinking, so yes, WHOA.
And it's time shrinking as well, or time stays the same.
Time stays the same. In these pictures, it's space that's shrinking.
Whoa.
So maybe space is not being made. They we're just getting you know, shorter with age.
I don't know. I mean, if you're shrinking, doesn't that make more space for you? I mean if you said, hey, Daniel, I want a bigger house, and then I like shrunk you in your family down the half size, you'd be like, oh awesome, my house is down twice as bien.
I think there's a movie with Matt Damon about that that's been made already. But what's an important distinction, though, isn't there Like that means that space is not being made. It's not sort of a thing that's being created. We're just drinking.
If according to the people on those planets, they're measuring greater distances between stuff, then I would say, yes, space is still being made.
In both scenarios, I see, you can make space by vacating it or by making an addition to your houses.
What you're saying, yeah, by either increasing the distances or shrinking the rulers. It's the same thing.
So you're saying, as I get older and my house is going to get bigger automatically, or as for my kids, right now, the house is just getting smaller and smaller physics says, Yes, it's a family affairs. What I'm saying. All right, So I guess the answer for James is that, unfortunately, we don't really know how space gets made. We just know that it is being made out there in space, or at least it seems like it's getting made.
Yeah, that's right, we don't understand space. There's all these fascinating mysteries. And it feels like the kind of thing where in fifty years or one hundred years, people are going to look back and be like, oh my gosh, the answer was so obvious, it was staring them in the face, but they were so stuck in their old way of thinking just couldn't see it.
Just sounds like maybe if James keeps asking questions, there's a lot of space for him to maybe find the answer to these questions.
There's plenty of space for everybody out there to contribute knowledge at the forefront of human ignorance.
And hopefully enough money out there to pay them also in the future. All right, Well, thanks to everyone for sending in their questions. We enjoy answering questions. We hope you enjoyed that. Thanks for joining us. 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. House US dairy tackling greenhouse gases, Many farms use anaerobic digestors to turn the methane from manure into renewable energy that can power farms, towns, and electric cars. Visit you as dairy dot COM's Last Sustainability to learn more.
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