My name is Michelle Thaller and I am an   astronomer. I work at NASA's  Goddard Space Flight Center. How astronomers seek to answer the  biggest questions in the universe. There's sort of two words that float about.  There's astronomer and astrophysicist. And   you know, it kind of depends on whether you're  trying to put on a more friendly or formal vibe.   I think they really these days mean the same  thing. I think there was a time when there was   sort of a separation of duties. There were people  that say a hundred years ago would would map the   stars and create all these wonderful catalogues  of stars and you might call those astronomers.   You know that the name is from astronomy, to  name the stars. And then there were people that   tried to figure out what the stars were and  how they worked, what the science of it was,   you know, behind all that. Those would be the  astrophysicists. And these days, the two studies   are really the same. If you're an astronomer or  an astrophysicist, you pretty much do the same   thing these days. The word that was probably  the best word, astrology, to study the stars,   that one was already taken. A lot of the questions  that I get from members of the public are these   vast conjectural questions like, you know, is  there a multiverse here? What happened before   the big bang? So, for my doctorate, you know, for  my research, um, I studied binary stars, you know,  I I studied two stars that orbit each other.  And most stars in the universe are like that,   by the way. And uh in the case of my stars, they  had these wonderful colliding winds of high energy   particles that produced these giant shocks in  the sky. The fun thing is that for for a while   at least and maybe today, uh there are some stars  in the sky that I've probably spent more time   with than anybody else in the world. You know, I  observed them for hours and hours trying to figure   out how these uh colliding atmospheres worked.  In the case of myself, I'm an observational   astronomer. I went to observatories all over the  world about 25 years ago when I was most active in   research. I did a lot of research in Australia uh  in Arizona, the Kit Peak telescopes, Mount Stromlo   in Arizona. I also used a lot of satellite data.  I I had data from X-ray satellites and uh the   Hubble Space Telescope. I actually got some time.  You see, as an astronomer, you are allowed to to   write into these observatories. It usually happens  once a year. And there is a panel that basically   assesses you know what would all these people  around the world like to do with the Hubble Space   Telescope. And the this this panel of astronomers  actually decides you know who should get priority.   One of the things about being an astronomer is you  end up doing a lot of writing. You end up doing a   lot of writing asking for time on these telescopes  and then hoping that your proposal gets selected.   Another thing is you end up asking for a lot of  time to write grants for money to support your   work. you know, if you get some time on the Hubble  Space Telescope, often it comes with an amount of   money to support the time you're going to do  that research. So, it it turns out that being   an astronomer, all of the training is about  the math and the physics and you the computer  science and then what you actually do dayto-day  is often a lot of writing and a lot of trying to   organize proposals and grants and how you're  going to support yourself doing your science.   And then if you work for a large organization like  NASA, uh, as some of your time as well is usually   assigned to some specific mission, you know, some  specific space telescope where you're going to be   helping clean up the data, figure out how we're  going to issue a call for proposals, organize the   panels that are going to vet and look at all these  different things. So in a way, you become kind of   an administrator. A lot of meetings. I think that,  you know, the normal life cycle of an astronomer   is probably 80% like business person. a lot of  meetings, a lot of grants, a lot of budgets. But   then, at least for me, there really was this  time. It doesn't happen so much when you're a   more mature astronomer, but when you're really  young and out in the field and making your own   discoveries, it really does feel like you're sort  of alone with the night sky all by yourself up up   on top of that mountain and you're you're seeing  things coming down through your telescope that,   you know, it's a it's a minor advance, but you  no human being has has ever seen before. And it's   it's a wonderful feeling of empowerment and sort  of, you know, kind of collaborating with the sky   and and seeing what we can figure out. One of the  things is when you get a doctorate, you have to   produce some kind of original research, something  that's never really been been done before. And   that's not as hard as it sounds. That sounds very  intimidating. I mean, how am I going to think of   an idea that nobody's ever thought of before? But  nothing in astronomy happens alone. You know what  happens when you're a graduate student after  college is you will join a professor doing his   or her research with them sort of as an apprentice  and uh and then over time as you get more familiar   with the work they will give you a little piece of  that research like hey you go ahead and and take   this part over yourself. You don't really need to  think of things entirely you know just off the top   of your head and and come up with brilliant ideas  out of nowhere. You start little by little working  with a group of astronomers and then slowly  you start to ask your own questions. you know,  maybe they've never had time on a telescope

to look up this little bit of it, you know,  or or this little bit of it over here is a new  question nobody thought of. And and eventually  you realize that what you're doing is something  that hasn't been done before. I guess there were  probably about a dozen stars in the sky, but there  were three that I really really focused on. And in  the in every case, these were binary stars. And  these were stars that were very massive. Stars  that were say, you know, anywhere between like  15 and 50 times the mass of the sun. big stars.  They actually only orbited around each other every  couple of days or at most about a week. So these  are very big stars in very close orbits. And so it  should make sense these stars are pouring off you  not only light but but high energy particles,  this wind of particles that we call stellar  winds. And then they collide in between these two  stars. Sometimes one of their winds will not be as  strong as the other. So the wind from one sort  of overtakes the other one and kind of blasts  away the wind from the other one. And as they turn  around each other, you actually sort of have this   wonderful kind of three-dimensional view of how  that shock wave goes all the way around. And so   I use a technique called tmography, which is the  same sort of thing you use in a CAT scan or, you   know, something like an MRI where you're trying  to produce a three-dimensional scan of inside   the human body. In this case, the instrument  goes around you. But in the case of the stars,   the stars would go around each other. And then I  could use this sort of software mainly developed   for medicine to actually try to figure out the  structure of these shock waves. This is you know   just sort of work a day astronomy you nothing  you know all that incredible or sexy about it but   it helps you understand stars better. It turns  out that these shock waves are responsible for  producing a lot of the molecules that we find  in space. You know stars create uh you know   atoms. They fuse hydrogen into helium and then  eventually helium into larger atoms over time.   But these shock waves, at least in the cooler  parts of them, can produce things like water,  the water molecule. And there are, you know, there  are some binary stars, like there are some in the   uh the Orion Nebula that are producing enough  water in a single day along these shock waves   to fill the oceans of the Earth like 60 times over  in a single day. Now, obviously, this isn't liquid   water. This is water in a in a molecular form, a  pretty hot gas, actually. But that's where a lot   of the the molecules responsible for life can come  from is from these shock waves. So it's a way of   trying to figure out just little by little how  the universe really does work, how stars work.   So my research is much more observational, much  more about stars. I certainly took classes in   cosmology, the study of the universe as a whole.  I took classes in quantum mechanics, you know,   graduate level quantum mechanics, graduate level  electromagnetism, all of that. People often start   right off with the, you know, are there parallel  universes? And I'd rather they sort of ask me,   you know, what are the importance of binary stars?  There's honestly not all that many astronomers by   number that do theoretical cosmology. You know,  most of us are trying to figure out things like   how stars are born and how they like live their  lives and die. We're trying to figure out what's   left over after a star explodes, a black hole, a  neutron star, or we're trying to figure out how   galaxies work, how many galaxies there are, how  do we observe them, how do they change over time.   There's only a few of us that are trying to answer  questions like, you know, what happened before the   big bang or, you know, are there multiveres?  We we all study that to an extent. We all go   to lectures at the conferences. I love going to  the ones on, you know, quantum theory and quantum   gravity. Most astronomers study things that are a  bit more concrete than that, if very far away. So,   it's often the case that, you know, I'm giving  some lecture on this the wonderful new images   of Saturn from one of our spacecraft like Cassini  and they're so beautiful and we're learning things   about the atmosphere and look at these pictures of  the these little moons we took in the ring system   and we're studying the ring system and we have a  wonderful lecture. I turn to the audience and say,   "Hey, any questions?" You know, and somebody  raises their hand and the first one is, you know,   are there multiple universes? It's like Saturn.  There are some words that are are really easy  to throw around and in science they become  interestingly complicated. People often say,   you know, do you believe such and such is

true? You know, do do you believe the big  bang is true? You know, do you believe that the  idea of multiple universes is true? You know, a  lot of these things. And when you're a scientist,  you're aware that what what you're doing is you're   constantly trying to approach reality. you're  trying to get closer and closer to describing   something very well, but you you know you're not  all the way there yet. And it's quite possible   that we we never will be. It's quite possible that  human beings with our our limited senses, our our   limited brains even, you know, won't really  know what the true nature of reality is. It's   it's one of these kind of wonderful things that,  you know, truth can change. you know, you know,   hundred years ago, people uh were certain that the  universe was not expanding, you know, and and of   course we found out that it was. And you have to  be able sometimes to take your your very precious   images, you know, models of what the universe  is like, about what reality is like, you know,   even about what the definition of truth is. You  need to make sure that you're ready to change when   better information comes on board. in physics at  least for the last hundred hundred years that that   has really challenged us to leave behind our human  ideas of of common sense uh the very definition   and perhaps existence of space and time. The whole  idea about what is reality, what is existence, you   know, what am I is a very very complex question  now to answer. I mean to give you some ideas   about this there there are some things that are  are are very simple like what is the interior of  the sun like? It's obviously something we've never  directly observed but we see energy pouring out  of the sun. Uh there are actually uh waves almost  like earthquake waves that go around the sun that   help us to study the interior the way those waves  travel. But do we know exactly how the core of the   sun works? No. No we don't. There are things that  we get pretty close to but we just don't really   have the observational ability to do so. But then  there are questions like what are space and time   really? For so long we've just sort of taken it  for granted that space and time exist around us.   Time flows in one direction. Space extends perhaps  to infinity. But then there was also a time when  we we didn't think that air was anything. People  didn't realize that we actually live, you know,   at the bottom of this wonderful ocean of air that  is our our atmosphere. People took it for granted  that that air existed. That was actually, you  know, proven in the 18th century that this was   actually something. Einstein showed us that space  and time absolutely cannot be the simple way we   perceive them. It it all is related around the  speed of light. The speed of light is always   constant to any observer. One of the myths about  Einstein was that he pulled all of these amazing  ideas just kind of, you know, out of his head  from nowhere that he wasn't part of the scientific   establishment. Well, in fact, he was. Uh he was a  professor. uh he was actually a graduate student   trying to get a job when he was working at that  patent office that he had that miracle year where  he came up with the the theories of special and  general relativity among other things. So here's   an example about allowing yourself to define  whether something is true in kind of a bit more of   an active way. Isaac Newton was able to describe  very very well how gravity worked. He was really   one of the first people that said there's this  force of gravity and he just said that it's a   force. this force permeates the universe and this  is why the planets orbit the sun you know this is   why apples fall from trees is they're reacting to  this force and by using his equation of gravity   you could calculate that force very very well so  you had this you know great thing the force of  gravity the force exists it binds the universe  together but then you have to ask the question  okay what what do we mean by that what is the  force of gravity what is it really what what   what causes it and it took Albert Einstein to say  that that what we think of as gravity is actually   a curvature of space and time. Things have to  follow space and time. We are all embedded in the   space and time of the universe. So if that space  and time has a shape to it, a curve to it, we   have to follow that. Light has to follow that. You  know, light itself that has no mass can actually   bend and go into a black hole. And that's because  the light has to travel through space and time and   the space and time itself is bent. So all of a  sudden there was this answer. What is the force   of gravity? It's a bending of space and time. So  is that it? Is that the end of those questions   that we can ask there? Well, how about the rather  obvious next one. What is space and time? Okay,   there's this thing that Einstein called spacetime  that that you know space and time are sort of  mixed together. They're they're two sides of the  same coin. When you change one, the other has to   change. If you are in a gravitational field and  and space is bent, time actually slows down. It   actually affects time as well. We know that these  two things are bound together. But what are they?   Time can be different for different observers  depending on your velocity. If you're going very   close to the speed of light, as people observe you  going by, they see your time is very slowed down.   If you're actually a photon going at the speed of  light, time stops entirely. So what do we mean by   this thing called time? And this is now what some  of the major physicists of the world are grappling   with. And they are trying to come up with some  very interesting answers. I think answers that   will be very challenging for us. Imagine being  a physicist back in the early 1900s and having  this this young Albert Einstein tell you space  and time are bendable. You can change them. You   can manipulate them. You might have thought they  were crazy. How about looking at space and time   instead as a consequence of quantum mechanics? A  lot of people have been saying that relativity and   quantum mechanics don't match. They don't work  together. And this is true. This has been true   since the beginning of relativity and quantum  mechanics at about the same time. Relativity   says that if you have a certain amount of mass,  you can actually say space bends this much. And   quantum mechanics says that everything is down to  probabilities. The universe never has set answers,   but maybe the probabilities of a particle being  here versus there. Even the curvature of gravity   must somehow be probabilistic. And Einstein didn't  like that. there was no way to work that into his   equations that actually, you know, made them both  work at the same time. What if we were asking the   wrong question? What if we're not looking at two  different things? What if we could actually say   that spaceime itself is a consequence of quantum  mechanics, not something separate from it, not two   things that are clashing together? And this is  the idea now that perhaps quantum entanglement,   if you look at it correctly, is spaceime.  Now quantum entanglement isn't just a term   you can throw off very very easily but this is  something that we have now observed and been able   to replicate in laboratories all across the world  even in space actually. If two objects interact   together they can actually sort of become in a  sense the same system under the laws of quantum  mechanics. So let me just give you a very simple  example of this. A lot of people know the model of   an atom where you have this uh nucleus of protons  and neutrons and the electrons can be in different   orbits around there. In fact, in in a single orbit  around the nucleus, there can be two electrons,   but those electrons can't be exactly the same.  You can't have two that are identical. They have   to have opposing spins, angular momentum. It  turns out you can have two electrons in each   one of these orbits, but the electrons can't be  identical. They have to be spinning in opposite   directions. It's a strange idea that electrons  spin, but at least you can say that there's   some kind of intrinsic angular momentum. What we  think of as something spinning, that's actually   a property that a particle can have, whether or  not there's actually like a physical little ball.   Electrons are not little balls, but they do have a  property of spin of uh angular momentum. You could   have two of them in the same orbit as long as they  have opposing spins. One spinning one way, the   other one's spinning the other way. So, say that  one is spinning, you know, up and one is spinning   down. the way my thumbs are pointing, you know  that these two electrons have to have different   spins. So, what happens if you actually take  them out of that system? You take them away from   the atom entirely and now you've got these two  little electrons somewhere in space and then you   know that they have to have opposing spins because  they once were in that same orbit. Well, okay. So,   now separate them. Separate them by a couple of  feet, maybe a couple of miles. How about a couple   hundreds of miles? Maybe there's no limit. We  found out that if you use some sort of energy   to change the spin of one of these electrons, the  other one basically instantly knows that that's   happened. And it's not that there is a signal  passing between one of these to another because it   doesn't travel even at the speed of light. It is  an instantaneous flip. It's not a signal traveling   because these two things are basically the same  quantum system. In the rules of quantum mechanics,   they are the same object. So there's no signal  really to travel to a quantum system. There   really isn't any such thing as space or time. It  will adjust instantaneously because it's the same   system whether it's microscopic or whether it's  many thousands of miles apart. They're the same   thing. Could it be that everything is entangled  to everything else in some way? Well, I mean,   there once was a time when the universe was very  small. You know, the time right after the big   bang where in a way we were all kind of the same  particle. That particle has changed and expanded.   But is it possible to think that in some way we're  actually the same quantum system to everything in   the universe. And what we perceive of as space  and time is the degree to which we're entangled.   We're entangled more to things that are closer to  us that have a chance to interact with us. The air   in this room, the space that's only outside in  my yard. I'm less entangled to things that I've   not been able to interact with much for a long  time. Things like distant galaxies, I haven't been   close to them since the beginning of the universe.  Einstein asked, "What is gravity really?" And now   we have to ask, what is spaceime really? And we  know it can't be as simple as the way we perceive   it. Maybe the underlying quantum reality of the  universe is that everything in a way really is  still the same quantum system.

I've always thought  when people think about alien civilizations   and they say the flying saucers and UFOs and  spaceships, I kind of wonder if the next step   in really understanding reality is that there's no  such thing as distance. And maybe a very advanced   civilization that can somehow manipulate that. You  don't have to travel anywhere in a spaceship. You   simply figure out how you access this entanglement  of the rest of the universe. Could it be that you   are really the same quantum system as everything  in the universe at once? And that degree of   entanglement is what we think of as space, as  time, as gravity. That's an amazing idea and  it's one that more and more people are starting  to look at. Do we know this is true yet? No. This   is still conjectural. But the physics is working  very well. And one of the promising things is that   the equations of gravity emerge now from quantum  mechanics. They're no longer general relativity,   quantum mechanics, they don't mix. You start with  quantum mechanics and gravity emerges from it,   from the degree of entanglement. So stay put  for a couple more decades. And uh like I said,   maybe someday we're actually going to figure out  what the underlying structure of this entanglement   is and then we can actually move outside of  space and time. When you are pure energy,   you have to travel at the speed of light. A  photon has to travel at the speed of light. It   can't go any other speed. A photon can't exist in  a state where it's only moving at say 20 m hour.   It has to travel at the speed of light. And when  you're traveling at the speed of light, you don't   experience space or time. You're probably familiar  with Einstein's idea that as you go faster and   faster, closer to the speed of light, time slows  down for you compared to an observer watching you.   If I'm sitting here still on the Earth and I watch  somebody in a spaceship whizzing by at half the   speed of light, I see them very very slowed down  compared to me. And when you're actually going at   the speed of light itself, time stops. That means  that light does not experience space or time in   any kind of extended way. All points in space are  one and all time. All points in time are one. Time   and space don't exist to a photon the way it does  to us. And yet I am made of something that you   can convert to photons and back and forth. And I  experience space and time. I experience those as   extended properties. There's a duality to the  universe. And I think this is going to become   one of the most important things for modern  physics that the next revolutions in physics.   Light around us. I mean, it's coming from the sun  through my windows. It's coming at me through,   you know, the lights that we have in the studio  doesn't experience the same universe I do. to it   in a real way. The universe never expanded. All  points of time and space are still one from the   perspective of a photon. And I am made of photons  kind of. But why do I experience space and time?   Space and time as we perceive them cannot be the  end story. There has to be a different perspective   that shows us a reality that that our human brains  don't perceive yet. But the physics all around us   of something something as simple as light demands  it. The things that kind of give me chills is just   how little we understand the nature of reality  itself. If something bouncing off me right now   doesn't experience the universe as having even  expanded, what does that mean? So that equation   equals mc^2. I mean it's it's useful. You can  use it to power nuclear reactions. You can use   it for particle accelerators. But it actually  sort of claws away the fabric of reality itself   and challenges us to ask what's underneath. To  me, I think one of the the most amazing things  about the universe is the question what is energy?   And this can go very very deep. Uh you know a lot   of us are familiar with you know energy is it  takes energy to accelerate something like you   know to actually like throw a softball that takes  you know energy chemical energy from your arms or   you could say something has potential energy like  it's sitting at the top of a hill and it's prone   to roll down the hill in the gravity field of the  earth that's actually called potential energy. But   then there's also the energy that's just intrinsic  in matter. One of the things that always gets me   about this is that energy, light, you know, light  is sort of a form of pure energy and us, you know,   matter, we're made of particles like protons and  neutrons and electrons. They seem so different.   They seem to have completely different views of  the universe as well, which I think is one of   the more interesting and disturbing things I know  about in modern physics. Let's just think about  the idea that energy and mass really are somehow  the same thing. that mass is some like coagulated   stored form of energy. That means the two of them  you can actually go from energy to mass and and   back and forth. And that's the famous equation  that Einstein came up with equals mc^2 that in   any amount of mass there is an equivalent amount  of energy and the two are basically the same   things. The universe actually doesn't seem to see  much difference between mass and energy. As long   as the amount is the same, it can exist in either  form. And let me give you some examples of that.   The way a nuclear reaction works like a nuclear  fusion reaction is you convert some amount of mass   into pure energy. Nuclear fusion actually brings  particles together, slams them into larger atoms   and in the process energy is released. So a little  bit of mass is lost but energy is produced. It   also goes the other way. In a particle accelerator  you get more and more energy because of collisions   of particles colliding together. They produce so  much energy that as long as as a given particle   has that amount of energy, any particle can pop  out of that reactor. And that's how we find new   particles. As we get to higher and higher energies  in a particle accelerator, just having that amount   of energy around the universe can manifest  it now as mass takes a lot of energy equals   mc^ squ. Energy equals mass time the speed of  light squared. That's a lot. But energy and   mass pretty much are the same thing.

One of the  ways the universe seems to do this is something   called virtual particles that if you have um you  know just just the energy you know around you the   energy of space and time itself there sort of  an inherent energy just in the universe that   energy can actually become mass it'll actually  form what we call virtual particle pairs like   an electron and its antimatter equivalent  a posetron. those two particles will just   literally pop out of the universe because there's  that amount of energy around and then pretty much   always they just annihilate each other. They  just go back. Matter and antimatter annihilate   back into pure energy. And this is happening  all around you. Everywhere around you in space,   these little virtual particles are forming and  collapsing together all the time. Some of the   more interesting things happen in the universe  when those particles get separated. Uh one example   is around a neutron star. It can actually make  a beam of energy coming off the magnetic poles   of the neutron stars by having virtual particles  be created and then accelerated by the magnetic   field. So all of a sudden you have this energy  that wasn't there before produced by the virtual   particles themselves. As you get to higher  energies, you know, say you have a very very   strong magnetic field, very high energy. Again,  we find these around neutron stars. That can start   creating lots and lots of these virtual particle  pairs. And the more energy you have, the more of   these little virtual particles you get until space  itself takes on an aspect of having mass. The   density of these virtual particles right around a  neutron star, even in empty space itself, would be   about three times the density of iron. It's just  just unbelievable. So energy and mass really are   the same thing. They're two sides of the same  coin. They can be converted back and forth to   each other, and the universe doesn't really care.  It sees them both the same way. When people think   about the most dramatic things in space, they they  tend to go immediately to black holes, which are,   you know, absolutely incredible. You know, out of  control gravity that you can actually, you know,   suck light back in. It's just amazing. But I think  neutron stars deserve a little more love because a   neutron star is also created when a massive star  dies, but it doesn't have quite enough mass to   actually collapse into a black hole. It actually   leaves behind a thing, you know, a physical thing   that you can study. So while black holes are  just sort of this bottomless pit, you know,   with neutron stars, you have this very strange  thing that you can look at them, you can observe   them, you can take real measurements of, and  you're looking at something that is mind-blowing,   and in some ways our physics really isn't ready  to describe yet. The thing about a neutron star,   you know, why why do we call it a neutron  star? For one thing, and I'm I'm going to   really oversimplify here, but basically when you  think about an atom, you have protons and neutrons   in the nucleus of the atom, and then electrons are  in in orbitals around farther away from around the   nucleus. Amazingly, the gravity of a neutron  star is so strong that it actually collapses   the electrons into the nucleus. The gravity  crushes electrons into the nucleus. And if   you crush an electron and a proton together, one  is negatively charged, one is positively charged,   you will get a neutron. A neutron actually will  naturally decay sometimes into an electron and you   know a proton. You have an object that's mainly  made of neutrons. There are some protons as well.   And it basically has the density of an atomic  nucleus, but it's about 10 miles across. I mean,   that's like one big nucleus. 10 miles across. It's  incredible. And because there was so much collapse   involved in their forming, you know, when when  you think about what they call the conservation   of angular momentum, if something is spinning and  stars actually do spin, if you collapse that down,   you actually spin up much faster. It's the classic  ice skater analogy. You have an ice skater with   her arms out spinning around and then as she draws  them in, you can watch that ice skater spin faster   and faster. Same thing happens. But in this case,  you actually have a ball that is about, you know,   10 miles across spinning 500 times a second. I  mean, I mean, that in itself is just mind-blowing   to think of, right? Something that big spinning  that fast.

Now, recently, neutron stars had  played this important role in explaining something   that we had no explanation for. They were very,  very mysterious. In fact, there were some people   that were wondering if we were actually looking  at might be a signal from an advanced alien   civilization. Those are called uh fast radio  bursts. Now, uh fast radio bursts have been in   the news for a couple of years because there  was so much energy in these mysterious bursts of  radio emission that we couldn't explain what was   going on. So for example, we would have uh you  know our radio telescopes would register a burst   of emission and the uh that burst would last say a  millisecond 1,000th of a second. That's about how   long these things would last. But in that 1,000th  of a second enough energy was radiated similar to   what the sun puts out in a week in a millisecond.  And so we were getting these signals from you know   all over the sky. We were trying to figure out  what that could possibly be. How could you make   that much of a tight burst of radiation in that  small amount of time at those incredibly high   energies? So, the race was on to try to figure out  what these fast radio bursts really were. Luckily,   we have many, many things that are at our disposal  to try to study these things. Right now, we have   many high energy telescopes that actually are  orbiting the Earth that measure things like X-rays   and gamma rays, the most uh energetic types of  light. light you only get if something is in the   millions or billions of degrees. It'll actually  emit X-rays and gamma rays. A wonderful thing   is that we actually started to be able to kind of  pinpoint to where these things were coming from in   the sky. And as we did that, they actually seem  to line up with neutron stars. So neutron stars   are most likely responsible for these fast radio  bursts. Now, exactly what's happening is something   that we don't really know yet, but it probably has  something to do with almost like an earthquake.   an earthquake, you know, you you have something,  you know, our something in our crust shifts and   there all these waves that go through the earth.  It's actually the way that we know the interior   of the earth is by studying those waves. You know,  we've never been able to actually take a sample of   the fact that the earth has magma all the way down  until you get to a at first a liquid metal core,   then a solid metal core. No one's ever seen  that physically, but we actually watch how   these waves of compression go through the earth  and we can put together what the interior of the   earth must be like. The same thing may be  possible for neutron stars, but on a much   more energetic scale. You have this this this  ball of of neutrons. Incredible densities,   incredible temperatures. And we think that there  must be a crust of neutrons actually that actually   forms on the outside of these stars. And inside  is probably a fluid, a fluid of pure neutrons.   We know this because neutron stars as they spin  sometimes seem to sort of slosh around almost like   a water balloon. So, we've modeled that to be sort  of a crystallin thin crust. I can't imagine what  that would be like. I mean, for one thing, that   the gravity would be so intense near that crust  that it would just crush you into just particles   basically on the surface of that neutron star.  But if that crust were to have a flaw in it and  there was some sort of uh you know a quake, it   shifted somehow, it would send compression waves  through the neutron star and release tremendous   amounts of energy in a quick little moment of the  crust actually sort of refiguring itself. So right   now our best explanation is that these amazingly  mysterious fast radio bursts are probably neutron   star quakes. And just like earthquakes have  taught us so much about the interior of the earth,   now we're looking at the signal, you know, even  in a thousandth of a second, take that signal,   pull it apart, and try to find the structure  that's going on inside that burst of radiation   and see if we can reconstruct what the inside of  a neutron star is like. Neutron stars really are   these real monsters. Unlike black holes, you  can see them. You can see their surfaces. You   can actually map how the radiation is coming off  them. When it comes to really mysterious parts of   the universe, but things that you actually can  measure, I'd say go for some neutron stars. The   closest neutron stars to us are very far away.  You know, they're on the order of many hundreds   or thousands of light years. So, luckily, they  don't really cause any uh trouble for us.

But the  question I've always wondered is how close could  you actually get to one of these things and and   make a measurement before you would just be fried  by radiation? Or in in the case of a neutron star,   something stranger still. A lot of people are  familiar with Einstein's famous equation E= MC^2   which says that energy is equal to mass times the  speed of light squared. And what that really means   is that in any amount of of mass, so if I think  about like the mass of my little finger, there's a   tremendous amount of energy. So if I could convert  my little finger into pure energy, the nuclear  bombs that were dropped on Japan, you know,  converted on the order of like a dime's worth of   mass. So, you know, there would be many, many, you  know, nuclear warheads right in my little fingers   worth of energy. But E= MC^² also goes the other  way. If you have a lot of energy, that basically   starts acting the same way as mass. And it does so  in something called virtual particles. If you have   a a lot of energy in a small space, the universe  will start to actually create particles that have   the same energy in their mass. So a lot of energy  can actually become mass. And and this is how our   particle accelerators work. This is why you can  discover new particles because if you just have  a very energetic collision, like you take two  gold nuclei and you slam them together, there's   so much energy produced in that collision that it  starts to pop off particles just from the amount   of energy. And as long as you have enough energy,  you can make any particle the universe has. The   particles come off in all different flavors as  long as they have the same amount of energy that  that collision is putting out. So neutron stars  are doing something kind of like that. They're   actually becoming sort of natural particle  accelerators in a way just because of their   mass. There is so much gravitational contraction  that the magnetic field, the electric field and   magnetic field of that star is actually compressed  around this tiny little object. Now, so neutron   stars have magnetic fields that are trillions of  times more strong than a typical magnet you might   have in your home, like a refrigerator magnet.  It would actually pull regular matter apart,   just the magnetic field. But there's so much  energy in those magnetic fields. So so think about   E= MC². There's so much magnetic energy right  around a neutron star that the vacuum of space   itself starts to make these virtual particles. And  I was at a lecture one time and this just blew my   mind. You know this is what happens when you work  at NASA and you know you go into a lecture your   colleagues are having you just you know any any  day of the week. And they were saying that right   around a neutron star the density of space itself  the vacuum of space right a place where it's a   vacuum. there aren't any particles otherwise  has about three times the density of pure iron   just from that amount of virtual particles being  produced by the energy of that magnetic field.   So what's it like to fly around something where  space itself has the density of three times of  iron? What's that like? What does that look like?  I would love to see what a neutron star looks like   from a safe distance. And I'm not exactly sure  what that is. When you're dealing with so much  energy that even empty space becomes much more  dense than iron. And once again, these are real.   They're up in the night sky tonight. I mean, you  can't see them because they're they're dim and   they're small and they're far away. So, it's not  something we actually see in the night sky. But   all around us, we're getting the radiation, the  high energy radiation from these things that are   are real monsters. Our sun has this wind of high  energy particles. This is something that was only   relatively recently discovered. I mean, when  you think about the fact that the very first   satellites we put into space, you know, starting  in, you know, the very late 1950s, you know,   and 1960s, they they realized that there was this  source of of of radiation up there. There was,   you know, a lot of particles around up in space.  I actually had the honor of being next to this   man named Eugene Parker. We have a a a wonderful  mission named after him called the Parker Solar   Probe. This mission is actually orbiting around  the sun right now, closer than any human-made   thing has ever orbited the sun before. It's really  really exciting. He was I I believe 94 years old   at the time of the launch. Usually we we only name  spacecraft after people postumously after they've   died. He was the one that basically predicted the  solar wind and was the the one that figured out   how it worked. And of course, we're still figuring  out a lot of the details, but they just couldn't   think of anybody better to name it after than  him. And so that was lovely. The source of these   these these high energy particles and exactly how  they get accelerated away from the sun is is what   we're studying right now. We know that this wind  of particles, when I say high energy particles,   I'm talking electrons and protons and, you know,  sometimes, you know, as large as like the nucleus   of a helium atom, something like that. and they  uh they get blasted through our solar system at   a million miles an hour in some cases. And so,  you know, we have this very high energy wind.   It changes planets. You know, it's responsible for  Mars losing its atmosphere over time and becoming   this kind of cold dead desert. It's responsible  for for Venus becoming sort of this this hellish   thing that we know it. It actually blasted  away all of the lighter molecules like water.   It left Venus with an atmosphere of carbon  dioxide and sulfuric acid. And even Pluto,   you know, all the way out at the edge of our  planetary system, Pluto is is still losing tons   of atmosphere a day, blasted away by this wind of  high energy particles. The only reason the Earth   is not really affected by it much is because  we have a very strong magnetic field. And so,   you know, our molten metal core, all that molten  metal moving around inside the Earth generates   kind of a magnetic bottle around the Earth. And  that protects us from this solar wind. But someday   the sun will actually, you know, pretty much  blast away our atmosphere anyway. So, you know,   planets change and and one of the important  things about knowing about this wind is we have   to understand our environment in space. The solar  wind normally is at levels that humans can take   quite quite easily. You I know that some people  that are into conspiracy theories say, you know,   how could we have gone to the moon because there's  so much radiation in space. Well, the answer is we   we kind of got lucky with Apollo because a normal  day, the solar wind is a a radiation level humans   can handle quite easily, you know, up in space  or, you know, on the moon. Problem is that if you   have a solar storm, a very very violent event that  unleashes lots of this solar wind, a lot of times   we call these coronal mass ejections. The corona  is the outer layer of the sun's atmosphere and and  coronal mass ejection. All this stuff comes out  at once. It's true that if if a big one of those   happens in the direction where astronauts are  unprotected from the Earth's magnetic field, they   could die. I mean, it could actually give them  a fatal dose of of radiation. That is something   that we need to consider. And it turns out that we  got kind of lucky that, you know, in between some   of the Apollo missions when no astronauts were  up on the moon, luckily we actually had events,   solar events that would have endangered the  astronauts. That's why it's hard to go to the   moon and also to Mars is to protect people from  that that radiation. It's not that hard to protect   you from it. I mean, a good amount of water  could do it. Like if you had a water tank in your   spacecraft and you could shelter behind that. It's  just that you'd have to bring up a decent amount   of water and that's a lot of mass. Or in the case  of the moon, I think if if you could dig down just   about 10 ft below the lunar surface, that amount  of rock above you would shelter you. But then we   need to bring, you know, construction equipment to  the moon that can dig a tunnel, right? So I mean I   mean there's all kinds of things we're considering  as to how you would handle that. So what happens   with shock waves is that you have say two binary  stars close to each other and they both have a   wind of particles. You in this case we don't say  a solar wind, we say a stellar wind because we're   talking about stars. But it's really the same  thing. The main difference is that the stars   that I was studying are very massive stars. Stars  that have, you know, anywhere from, you know,   let's say 20 to 50 times the mass of the sun.  And they actually have really strong winds. much   stronger even than the sun does. So when you have  these two stars close to each other, these winds   come off and they collide. And when that happens,  I mean I mean literally the the the electric and   magnetic fields, you know, sort of entangle with  each other. The particles collide together and   that creates a very very hot area that we call a  shock wave. As all of this stuff comes together,   basically slows itself down as it collides, you  get all of this heat and radiation emitted along   that that that shock front. Those are wonderful  shock waves that are created by colliding winds.   Yeah. So, one of the big challenges right now,  especially as we consider putting astronauts back   on the moon, is there a way to predict when one  of these violent events is coming? The answer is   uh yes, in several ways. So in the in the very  simplest way, we actually have spacecraft as I   mentioned there's a spacecraft orbiting the sun  right now. There's actually two, the Parker Solar   Probe and the Solar Orbiter from the Europeans.  And we also have other spacecraft between the   Earth and the Sun. As one of these, you know, big  belches of material, charged high energy particles   comes out of the sun, it will hit different  satellites that will measure how fast it's going,   how much energy is being delivered. And usually  in the case of of say the moon, uh the the earth   has about a day or maybe two days notice. So you  could say to the astronauts, hey, something's   coming. You know, everybody go shelter. You know,  as long as you had a good shelter there. But then   there's the question of can you predict it before  it actually happens. And this of course is one of   the the huge goals all over the world of people  called helopysicists. Helio for sun and then   physicists. So people who are are physicists that  specifically study the sun. the the sun is this   incredible magnetic marvel. A magnetic field is  generated by moving charges, right? So you think   about like the the charges in moving metal that  generates a magnetic field in an engine. In the   case of the sun, the sun is made almost entirely  of hydrogen, but it is so hot on the surface that   that gas has become ionized. that what that means  is there's so much energy that electrons that   normally orbit around a nucleus, the electron gets  so much energy it just takes off and that leaves   two particles that are charged, an electron and  a proton. Anything that has an electric charge,   a magnetic field can bend. And so when you see  these wonderful like loops on the sun and and and   you know all of these beautiful shapes, that's the  very hot electrically charged gas just following   the magnetic field of the sun. The name for it,  and it's kind of a confusing name, is plasma. You   know, you can actually see the shape of the sun's  magnetic field, but it's chaotic. It's incredibly   complicated. So, you have these wonderful loops  of magnetic energy, you know, all this stuff   following it. So, how do you predict, you know,  when one of those loops is going to break open and   and actually like spew stuff out and create one of  these big ejections? We're getting better at it,   but it's still something that we don't understand.  I mean mean something that simple of you know our   own star when is there going to be a really big  storm we can't predict it down to the hour we can   say there's a very active region here that looks  like it might produce something but there's no   way to guarantee that actually it kind of reminds  me of the year uh 2012 because I was having sort   of a difficult year that year because uh people  had this idea of the Mayan apocalypse. It was   2012 apparently that was the end of some  calendar cycle in the the Mayan calendar.   The the idea was that something catastrophic was  going to happen. And I would get calls, seriously,   people would call us at NASA and say, you  know, I don't want my pets to suffer. You know,  should I euthanize? I I actually got a call  somebody wondering if they should euthanize their   pets. Other people would say things like, is the  world going to end next month? And and I' I'd say,   you know, look, okay, if I knew the world was  going to end next month, do you think I'd be here   in my office answering phone calls? I don't think  so. And we kept telling people that there was   really no reason to worry about anything. There  was nothing unusual astronomically happening. The   sun was in a naturally active period that year.  Every 11 years or so, the sun becomes very active   and then it kind of gets quieter again. One of  the reasons I know this is cuz I I love to see the   northern lights, the auroras, you know, those are  caused when you get these charged particles in our   atmosphere and uh they create these beautiful  glows around the poles. You know, for us,  that's really the only thing we really notice  for the most part. What happened actually is   that there was a colossal coronal mass ejection,  one that would have actually been dangerous to our   power grids here on Earth. It wouldn't have caused  any damage to like people or animals or plants,   but it would have actually dumped electric  current into our magnetic field and it it   probably would have taken down, you know, a lot of  power grids. It would have caused a lot of damage.   The thing though is it went off on the other side  of the sun from the earth and we had satellites   out there in that other direction out in the solar  system and and and they got knocked silly by this   big burst of charged particles from the sun. And  so we looked at that and we were able to observe   it and see what had happened and track it and all  of that. We all kind of went the the sun spins.   It actually doesn't all spin at the same rate.  The equator spins faster than the poles. It's   not a solid thing. It kind of twists itself up.  the sun, you know, on average spins about once   every 29 days. And so we don't really know. There  could be an active region that's about to blast,   but then it could spin out of our view and and  so we're safe from it. Or something could come,   you know, from the other side of the sun that  we didn't see. There's all sorts of wonderful   complexities when it comes to observing this this  phenomena we call space weather. The winds and the   storms, but in this case, winds of particles and  magnetic storms, storms of magnetic chaos on the   sun. It's a wonderful thing to think about that  our our lovely gentle star up there is is actually   very dramatic and and very volatile. Sitting here  at the bottom of the Earth's atmosphere, we're not   really aware that we're in a larger environment  in space. And the dominant thing is the sun. You   know, the sun obviously is the biggest thing in  our solar system, the most important thing. The   sun not only puts out a lot of light and heat, but  it also puts out a wind of high energy particles,   high energy protons and electrons, charged  particles. We actually are bathed in this all the   time. It interacts with our atmosphere. It creates  the northern and southern lights. In some cases,   it can even be a a risk, especially to our  technology. We're quite well protected from   these high energy particles by our atmosphere and  also by the Earth's magnetic field. The Earth has   a very strong magnetic field that surrounds our  planet and protects us from the worst of this   stuff. Even the astronauts up in the space  station, they're actually close enough to   the Earth that they're largely protected by this  magnetic field. When you go out to the moon and   farther away, that's when you're not protected by  the Earth's magnetic field and you find yourself   just basically exposed to this wind of high energy  particles. A lot of people don't realize how  significant that is and how much uh not only NASA,  but Noah and other organizations all over the the   planet are monitoring this. There is a fleet of  satellites right now and I don't know exactly   the number because it usually changes but we have  some satellites that are orbiting the sun itself.   We have some that are actually placed between the  earth and the sun. There is a place that actually   the the sun's gravity and the earth's gravity  balances out. If you're between the earth and the   sun, you're actually attracted equally to either  one gravitationally and you stick a satellite   right there and it doesn't take a lot of energy  to actually keep it in that spot. So we have this   kind of early warning system to see if there's  something dangerous coming from the sun. And then   we have all kinds of observatories both here on  the earth on in on the ground and also space-based   observatories that orbit the earth that just look  at the sun continuously. We even have satellites   around the solar systems look at different angles  of the sun. So we we've got the sun covered. Now   why is it so important? Well, the solar wind  normally doesn't really have much danger to us,   you know, or the environment in space. But when  you're dealing with space weather, sometimes   there's a really big line of thunderstorms  coming through. Right? So in the case of the sun,   the sun sometimes has very very violent storms.  And these are storms caused by the the chaotic   twisting magnetic field of the sun. Some of the  hot gas on the surface of the sun actually gets   accelerated so quickly by these magnetic fields  that it just breaks off and takes off into space.   And in one moment you could have trillions of  tons of fast highmoving charged material coming   out towards the earth. Now that's not actually  very dangerous to us biologically. But what that   can do is carry a huge amount of electrical and  magnetic energy. All of a sudden all these charged  particles hit the magnetic field of the earth and  they can actually dump electric current right into   our magnetic field. There was a famous event  in the mid 1800s called the Carrington event.   With the Carrington event, we really were just  starting to have things like telegraph lines. Now,   in order to get a telegraph to work, there has to  be electric current on the wires. And normally,   you would hook up your telegraph to a power  generator, and that would create electric current,   and you could send your signals. So, when this  Carrington event occurred, there was so much   electric current dumped into the Earth's field  that you could actually start sending signals  with no connection to power. And then eventually  as the storm went on, some of the telegraph wires  actually caught on fire just from a storm of  magnetic and electrical energy. These particles  coming from the sun. So these days, of course,  you know, we know that this could happen again. Uh   events like this are rare, but they they certainly  will happen from time to time. So there are all   kinds of organizations, you know, the uh like like  FEMA, you all these disaster relief organizations   that work with NASA and Noah to actually figure  out what happens if we think that a a dangerous   solar storm is imminent. Um in the case of  all of our satellites up above the atmosphere,   they're very at risk. So we can basically shut  them down, put them to sleep for a little while.   Of course, that that that energy burst will  hit them and it may damage their detectors,   but at least most of the electronics are shut down  at the time and we can recover them hopefully. And   then there may even be uh you know plans that  are necessary to to shut down parts of power   grids because I think the biggest danger of these  things to us is that when they actually hit the   earth's field you could have so much again energy  in that magnetic field of the earth that it could   you know fry our power grids. I mean think about  how bad it would be if all the power on earth just   went out because of one of these solar storms. I  mean that that could conceivably cause billions   or maybe even trillions of dollars of damage. So  there are people rehearsing these scenarios. There   are people uh you know trying to figure out how  we would shut things down, how we would protect   ourselves and then we have our fleet of satellites  trying to observe the sun all the time and we   would have probably about a day's notice as one of  these big storms made its way through the sun. The   sun we think of as putting off lots of light and  you know light travels at the speed of light which   takes about 8 minutes to get from the sun to us.  But this isn't light. These are charged particles,   protons and electrons. And although they may be  moving millions of miles an hour, it still will   take them about, you know, a day or more to get to  the Earth. So, we will have some warning. But yes,   I mean, all around you there are people monitoring  space weather and getting ready for a big storm.

You know, the thing that's really fascinating  to me about asteroids is that they are kind   of a preservation of the way the solar system  was billions of years ago. This is really true.   The solar system was once this kind of cloud of  gas and dust and then under the forces of gravity,   things started to clump together into smaller bits and then larger bits that eventually  became planets. And planets like the Earth   changed so much, right? I mean, the interior  of our planet is molten. There's stuff that's   melting down there. On the surface, you've got  erosion and rain and wind. So, nothing is   really the same as it was billions of years ago.  But there were these little small building blocks   that got left behind that actually never got  made into larger things and they're pretty much   unchanged for billions of years. So scientifically  the reason these are such treasures is that  they are kind of a a time capsule of what the  chemistry the physical conditions everything was  like as the solar system formed. The question of   mining them. So the thing that happened with the  earth is that the earth has this this hot molten   core and most of anything that's heavy sinks to  the bottom. Right? So when you have a liquid,   heavier stuff sinks to the bottom. So the core of  our planet is made of iron, you know, and nickel,   but also metals like gold and silver and platinum,  anything that was heavy when the Earth was molten   would have mainly sunk to the core. So that  means that if that didn't happen to an asteroid,   an asteroid is still kind of all mixed up.  The heavier stuff hasn't actually sunk out   of it. Given a volume, there is in fact more rare  elements, more gold, more platinum, more titanium,   whatever. But asteroids are also fairly small and  of course they're in space, so they're hard to get   to. To me, it becomes kind of a a cost question.  Yes, asteroid material by and large has more rare   valuable elements than parts of our Earth's crust.  It also has a lot more iron. You can get very   expensive iron. I don't know when it will actually  become economically feasible to go all the way to   an asteroid, mine it, bring stuff back or however  you want to do that to get the tiny little bit of   gold that you'll get out of it. My guess is not  soon. I don't think we will actually be mining  asteroids in any real commercial way very soon at  all. It's a fascinating question whether you could   use a compass in space. So, let's talk first  about compasses and then maybe talk a bit more   about the idea of how we locate ourselves in space  in general. A compass is something that responds   to a magnetic field. So, the reason a compass  always points north is that it's responding to   the magnetic field of the Earth. Our planet has  this wonderful core of molten metal. That metal   moves around inside the Earth and it generates a  magnetic field that has two poles, a north pole   and a south pole. When you make a compass, you  make it out of something metal that can respond to   that magnetic field and it points to the magnetic  pole of the Earth, which is very close to our   north pole. A magnetic field directs compasses.  Obviously, if you go away from the Earth,   far away from our planet, it's no longer going to  be able to feel our magnetic field. So, a compass   will not point to the north pole of the Earth if,  say, you're out by Saturn. Saturn and Jupiter are   separate planets and they have magnetic fields  of their own. So certainly if you were actually   close to Jupiter, Jupiter has a magnetic field  much stronger than the Earth's magnetic field.   Your compass would definitely point to the  north pole of Jupiter if you were actually   around Jupiter. Now, but what if you get farther  out? What if you actually go farther from there?   Is there any magnetic field out in space itself?  Well, actually, it turns out that there are that   our galaxy does have a magnetic field as a whole,  too. This magnetic field might be hard to detect.   You might need a very, very sensitive compass, but say you had it. you would actually see that   our galaxy does have sort of a magnetic north and  south pole and that magnetic field permeates our   whole galaxy. With compasses, you could actually  at least find out where the north and south pole   of another planet is, the north and south pole of  a star. A star has a magnetic field, too. Even the   north and south pole of a galaxy that's responding  to a local magnetic field. But then it kind of   begs the question, how do you find your direction  in space that doesn't involve a magnetic field   out between the galaxies where really there's no  detectable magnetic field at all? Everything is   moving. There's nothing to say this point is still  and this is the reference point we're going to use   and everything moves according to that point.  We're moving around the sun at uh about 66,000   miles an hour. Right now the sun is moving around  the galaxy around the core of the galaxy at about   half a million miles an hour. We are actually  falling gravitationally into the center of a   cluster of galaxies at about a million and a half  miles an hour. That's just when we say relative   to what? Relative to the sun. Relative to this  group of galaxies. There is no absolute standard   of reference in the universe. There is one thing  that is perhaps the best way of navigating your   way around the universe and that's something  called the microwave background radiation. That's   the farthest radiation we can possibly see. That's  radiation that's coming everywhere in the universe   from a time about 400,000 years after the Big  Bangs. And it fills all of space with this gentle   microwave radiation. And it's pretty much the  same in every direction. In fact, if you had an   old style television that used to have an antenna  decades ago, a lot of the static that you would   see on the screen was actually microwaves from  this background radiation. And one of the things   we can measure is our motion relative to this bath  of radiation, the microwave background. So if you   were trying to navigate with a compass in space,  just remember that compass is going to respond to   the strongest and closest magnetic field. It will  point north, north to the pole of a planet, north   to the pole of a star, even to the north and south  magnetic poles of our galaxy. But what you're   reading is a magnetic field. That's what a compass  does. And that's pretty much all it can tell you.

Well, this is the thing about the power of  astronomy that kind of really does blow my mind   is how much we actually do know. There's all kinds  of things that we don't know and and astronomers,   scientists in general tend to really focus on  what we don't know because that's what we're   working on. That's that's our jobs. That's that's  how we get, you know, the grant money to sustain   ourselves is trying to answer the questions that  we don't know yet. But the things that we do know   in some ways, just how recently we know them  really kind of blow my mind. You think about   what are stars made of, right? I mean, you've  probably heard that stars are mainly made of   hydrogen and helium. You know, they're these big  sort of balls of gas, you know, very, very hot,   dense burning balls of gas. But how long ago did  we know that? It was actually really not until,   you know, times like the 20s or 30s that a young  woman named Cecilia Payne, uh, working at Harvard   wrote a PhD dissertation pretty much proving they  had to be made out of hydrogen. It was a graduate  student, a woman graduate student. At the time,  the idea was that the sun was probably something   very much like the earth. It was like a big rock.  And if you have a rock that big, and this is true,   there would be so much gravity pushing it  together that the temperature of the rock would   be very hot. So, you know, the temperature of the  surface of the sun is round about 10,000°. And if   you had a rock that big with that much gravity  pushing it together, it would be that hot. But   it would only be that hot for probably a couple  million years. And the neat thing was, you know,   around about the late 1800s, it was Charles Darwin  who had been looking at things like uh evolution,   the strata of rock like the Grand Canyon, and  he sort of had this this feeling that millions   of years certainly was a long amount of time,  but he didn't think it was long enough to for  the changes that he saw in the earth itself.  The prevailing idea, and this was a problem,   is that the sun was basically a big earth. Gravity  just just the contraction of gravity was making   it hot. it would take millions of years to cool  off. It turns out that wasn't it at all. It was   actually made of hydrogen, the lightest substance  in the universe. But now you have so much gravity   crushing together the hydrogen making the interior  very hot, millions of degrees hot, hot enough   actually to start a nuclear fusion reaction and  that can last billions of years. Certainly one   of the biggest misconceptions is that people think  that scientists feel that the big bang came out of   nothing, right? I mean, how did all of this energy  and all of this matter that made up the universe,   you're saying it just came out of nothing? No. I  I I don't think any scientist actually believes   that. The problem is when you think about  the condition the universe was in at that   point where I mean take our observable universe,  right? I mean, you can look from one side of the   universe to the other back, you know, 13.5 billion  lightyears or more. All of the stuff that we see   was actually compressed into a space smaller  than an atom, a volume smaller than an atom.   We don't have the physics that describes how that  would work. That is so much mass, so much energy   in so little volume. I mean, at this point there  wasn't even mass, just basically pure energy that   right now our physics doesn't go there. As we get  a better idea about how gravity works under very   extreme circumstances, you huge energy densities,  we may have some idea what set off the big bang   and possibly what came before the big bang. And  even that word is a little bit difficult when you   start talking about the big bang because the big  bang we believe was the creation not just of space   but of time. Whatever state the universe was in  before the big bang probably didn't have time as   we perceive it either. Space and time appear to  be some kind of a consequence that of the later   expansion. So how do you describe something that  doesn't have space and time that has huge amounts   of energy and tiny little volumes? We don't have  the physics. It's not that we will never know this   but right now we don't have any way to describe  it. Now another major misconception about the big   bang is that the universe before the big bang was  small. Okay. Now didn't I just say that everything   we see in the universe was probably contained,  you know, less than the volume of an atom. And   didn't I just say that? Well, the thing is I know  every scientist understands that we cannot see the   entire universe right now. And that's because  there's such a thing that we quantify as the   observable universe. The universe has existed, we  think since the big bang about say 13.8 billion   years. So as you look farther and farther out  into space, you necessarily have to look back   in time. If something is a million lighty years  away from you, like the Andromeda galaxy is about   two million lighty years away. The light that   you see through binoculars tonight as you look   up at the Andromeda galaxy left two million years  ago. You're seeing the Andromeda galaxy as it was.   So today we actually have telescopes that are so  powerful they can see back to a time about 400,000   years after the Big Bang. That's amazing. We can  see so far away in space that the light has taken   that long to get to us. You know, nearly 13.8  billion years. And when we look back to that time,   the universe looks very different. For one thing,  it's very hot. It's actually about as hot as the   surface of the sun. And it's so dense and hot  that we actually can't see any farther. Literally,   in any direction you look around the sky, anywhere  you look, if you look to that distance, you see   the universe as it was at that time, 400,000 years  after the Big Bang, and everything becomes just   hot hydrogen gas. So, I know this is kind of a  strange way to uh to put it because we're talking   about before the Big Bang, there may not have been  space and time the way we think they are today.   But whatever it was before the Big Bang, whatever  was there, there was a tiny little part of it,   a tiny little volume that expanded to become the  universe we see today. But that little bit wasn't   the whole universe. We don't know yet how big the  original universe was, all of it, before the big   bang happened, before something changed to make  it expand and completely change its form. So the   universe before the big bang didn't have to be  necessarily tiny. It actually could be infinitely   large. Because of that, we have no idea how big  the universe is, what shape it has. All we can   see is a tiny little bit of it. Think about my arm  being the universe before the Big Bang. you know,   in some kind of state that we can't even  describe through modern physics. The entire   observable universe that we can see now used to be  a tiny volume of it, maybe an atom in my arm. One   atom expanded and became the entire observable  universe that we see. But that's not the whole   universe. There are trillions of atoms in my arm.  Each one of those could have expand to actually   be its own entirely observable universe. So, we  can't tell yet how big the universe was before  the Big Bang or even what shape the universe  is because all we're seeing is a tiny little   bit of it that expanded to become everything that  we see. But that's not the whole universe. That's   our observable universe. There's far more out  there than what we can see. One of the most   common questions that I'm getting from the public  these days is, is our universe a simulation? I I   think that one of the things people are thinking  about is they've heard the term the holographic   universe and this is indeed a very powerful and  increasingly popular idea in modern physics but  it's a little bit unfortunately named and and let  me sort of take you through this. This all started   a couple decades ago when people like Stephven  Hawking and others were trying to figure out how   a black hole really works. We know black holes  exist. We actually observe them from a distance   very routinely. But the physics of how they work  never quite worked. They appeared to violate some   pretty important laws of physics. The universe  doesn't like to lose information. A particle has   a charge. It has a spin. There are all kinds of of  things you can say about an elementary particle.   But when it falls into a black hole, the only  thing that seems to exist anymore is mass, the   gravity that that particle had. What happened to  the information about its charge? Can you ever get   that back? As people began to do the mathematics  a bit, they noticed something very intriguing   that everything seemed to work much better if you  assumed the black hole was twodimensional. Now,   black holes are actually three-dimensional  objects. You know, a lot of times they're   portrayed kind of as things going down a drain,  but basically you have a sphere, which is the   point of no return. Gravity is so intense around  a black hole that if you get anywhere this close,   you never come back out. That's the event horizon  of a black hole. So instead of assuming that it is   a a sphere around the black hole, it all started  to act like it was a two-dimensional surface,   something that was three-dimensional became much  more understandable if it was two-dimensional.   And as scientists do, they thought, well, okay,  if this works for a black hole, is it telling   us something about the rest of the universe?  And this may be one of the most important new   revolutions in modern physics that the laws of  physics might work a lot better, might actually   work out together if you assume that our reality  is really two-dimensional. You look around, there   seems to be more than two dimensions in space and  there's time. How would that work? The example  of a hologram came up. You know, I still remember  being at a hologram museum back in the 1980s. Uh,   and the holograms were really new and really  exciting. The idea that a hologram is made out   of just a two-dimensional block of film or a block  of glass, but it seems to be three-dimensional   when you look into it. And even more than that,  I remember this one hologram that was put on a   pedestal and as you walked around the hologram,  somebody appeared to move inside and wave at   you. If you were looking at the hologram, there  appeared to be motion and even time all embedded   in just this two-dimensional surface. That's what  they mean when they say holographic principle. It   doesn't imply that anybody made a hologram or  that we are part of a projection that somebody   some evil genius is projecting reality on us.  What the holographic principle really is is   the universe may store energy in a way and  information in a way similar to a hologram.   If that's true and we really are embedded in  this two-dimensional universe that has some   pretty amazing repercussions. It probably means  that every point in time exists at once. That,   you know, our idea that things are changing and  that I'm I'm moving right now and time is flowing  in one direction. That's probably the same as  somebody just walking by a hologram and having the   perception that the image is moving. It's probably  not real. The amazing idea is that the extension   of space itself and time actually flowing may not  be real intrinsic parts of the universe. They may   be some way that we perceive it with the human  brain, but in fact there's an underlying reality   where that is not true. We say that these are  emergent properties. It's not the real story.   A hologram doesn't really move. A hologram is not  really three-dimensional, but it seems so through   our perception. That's an amazing idea that the  entire universe exists all at once as some kind   of surface of information. That's the holographic  principle. It's working quite well right now. I   can't tell you whether it's true or not, whether  there there really is some real two-dimensional   thing that we think of as the universe. So, stay  tuned. At the time that Darren was doing this, I   think there was sort of this argument between like  biblical people that said the earth was a couple   thousand years old and then the scientists said,  "Oh, no, no, it must be millions of years old."   What one of the things about being an astronomer  is you throw around very very large numbers all   the time. I mean, some of them are just kind  of, you know, stupidly large. But even things   like how many is a million, right? How many is  a billion? The the human brain, I don't perceive   that really any better than anybody else. The  human brain just doesn't go there. Instead, you   kind of find yourself getting used to swimming in  an environment where your your mind can't really   grasp all the way around a concept. It just can't.  You I can't tell you how far away a lightyear is.   I mean, one lightyear, you know, the distance  light travels in one year at 186,000 miles per   second. That's a close to about 6 trillion miles.  I I don't have the ability to actually visualize   that or feel it. And yet to me a lightyear seems  very familiar and actually actually quite close.   So maybe that's one of the reasons astronomers  are almost kind of predisposed to being able to   let go of sort of your common sense when people  say things like the inside of a neutron star,   you know, is is is so dense that a single  teaspoonful, you know, of that material would have   as much mass as Mount Everest. It's like, okay,  the laws of physics pretty much require that. or   when when people say what was the temperature  of the universe just you know 3 seconds after  the big bang that our physics really does work to  to predict that. So I think that when you start   swimming just in these big numbers and you begin  to kind of let go of the idea that the human mind   is the beall and endall. You know we have these  tools to start attacking larger problems to start   asking bigger questions. All of a sudden it comes  very natural to say things like oh yeah you know   gravity is actually a bending of space and time.  The amazing thing about that is that that started   out to be completely theoretical. You know, people  thought that Einstein's theories were very useful.   I mean, they made extremely accurate predictions  about how the planets move, about how the universe   works. But was there any really reality to the  fact that space and time could bend? I mean,   literally the space in front of me, the  space and time around me can change and bend,   even have a direction to it. It turns out that  you know our theories for the most part do lead   us to something really physically true. And you   know right now people ask me questions like are   there multiple universes? What's the shape of the  universe? You know the larger universe? All of   these things are wonderful questions and we don't  know the answer to them yet. But I have a feeling   that it's not just wasting time. You I think some  of these stranger theories will bear themselves   out over time. We just need to wait. Right now,  I think it's a little bit too soon to follow them   all the way into the rabbit hole. Let's say that  there were many, many multiple realities. Well,   how would physics work? How would this work? It's  still too much conjecture for me to invest a huge   amount in it. You know, I still remember, you  know, what's only 2,000 years ago, unless that you   had people like Aristotle who were brilliant and  they came up with this idea that all the planets   had to follow perfect spherical orbits around the  Earth in the middle and they were on these crystal  spheres that somehow moved and you know, people  all the way up into the Renaissance were trying   to figure out how those crystal spheres could  have worked and how they were supported. Well,   it turns out there weren't any crystal spheres.  There's always a bit of me as an observational   scientist that says, you know, take everything  with a grain of salt for now. Oh, I mean, airsoft   had this elegant, wonderful system. I mean, people  loved it until the Renaissance, right? It's just   that our observations didn't bear up with it. And  it was so beautiful, people hated to let it go,   but unfortunately, that's not how the solar  system works. Definitely pursue these questions,   but I'm not sure I'm ready to dive all the way  into any of those rabbit holes quite yet. I love   to think about them, but I think it's probably  a little too soon to follow them ultimately   to where they might go. So, people today have  all these wonderful questions that that modern  physics is leading us to. Questions like, are  the way we perceive space and time real? That's   even 100 years old. Albert Einstein said that  space and time could be bent. Time itself could   stop. Then there are things like the holographic  principle. Is it possible that our whole universe   is some sort of embedded information  structure on a two-dimensional surface?   These are amazing ideas and they may turn out to  actually have some physical truth to them. We're   not really sure yet. But sometimes people say,  "Well, are you scientists just absolutely crazy?   How is it that you so blightly get rid of the idea  that time has a direction or that space is real?"   One of the things you have to very deeply  accept to be a scientist is that your senses,  the human brain is just not the best instrument  to perceive the entirety of the universe. I mean,   let's take a simple example. There are many, many  colors of light, energies of light that our eyes   are not sensitive to. There are things like gamma  rays and x-rays, ultraviolet light, radio waves.   Those are all just different colors that our  eyes don't see. The universe has colors that just   weren't built for the human body to perceive. And  when it comes to a mind, a brain. Think about some   of the incredible creatures all around us. I mean,  you know, think about a grasshopper, a marvel   of evolution. It has a brain. It has a central  nervous system. But could you teach a grasshopper   quantum mechanics or general relativity? You know,  could it compose a symphony or or write a novel?   It just can't. I mean, a grasshopper's brain  just doesn't have the complexity to do that.   A grasshopper doesn't perceive those things. What  about a bacterium? A bacterium doesn't even have   a brain, but of course, the the majority of life  on Earth by mass is still bacteria. You have to   have this humility and remind yourself that it's  possible that the human brain is just as far away   from perceiving the way the universe really is as  a grasshopper is to perceiving quantum mechanics.   We are not some beall and endall of perception.  The universe was not designed, not built to be   comprehensible to the human mind. We only see a  little bit of it through the filter of what our   minds can ingest and how they do it. And so we  think that there really is such a thing as space   and time. You know, we we actually think that  there is a past, present, and a future when in   fact there may not be. And this goes all the way  back to Galileo. You know when Galileo was around   the idea that the earth had to be the center.  God made it. So God must have put the earth   in the center. But then it became proven that the  earth went around a larger object, the sun. And I   think almost more beautifully, one of my favorite  observations of Galileo is that when he invented   his little telescope, he he looked at the sky and  he realized that there were stars in the sky you   couldn't see with just the unaded human eye. There  were stars up there that we were unable to see   unless you looked through a telescope, a piece  of technology. And the question was, why would   the universe do that if the universe was designed  for us to see and us to perceive? Why would there   be things too far away and too dim for us to  see? Why are parts of the universe so strange   and so incomprehensible and make so little common  sense? Honestly, why should it be any other way? Want to support the channel? Join the Big Think   Members community where you get  access to videos early, ad-free.