Transcription
There were folks who were going to measure the radiation left over from the big bang, the cosmic microwave background. And they were going to very precisely determine the state of the universe as it existed shortly after the big bang. And we have a new model of the universe which goes by the sexy name lambda CDM. How do I go from the early universe to the late universe? We invoke dark energy shortly after the big bang in a period called inflation. Is there a way to reconcile this without having to invoke another tooth fairy?
>> Yes.
>> You invoke Santa Claus.
>> Exactly.
>> This is Star Talk. Neil deGrasse Tyson, your personal astrophysicist, and I got with me co-hosting.
>> What's up?
>> How you doing, man?
>> I'm good, buddy. Good to see Paul Mccurio.
>> Good to see you again.
>> Professional comedian. You got your own podcast.
>> Yeah. Uh, inside out.
>> Out. Out and in.
>> Inside. There you go.
>> In burgers. Did they sponsor you?
>> Yes.
>> For those listening and watching, this is how not to host the show.
>> Have a guest and not know ex anything about it. Yes. It's called In-N-Out Burger. And the whole podcast is me interviewing people in the drive-through window.
>> In the drive-through window.
>> You want fries with that? So, you're an astrophysicist?
>> The guy was on my podcast.
>> I was. I was.
>> Along with Paul McCartney, by the way.
>> Oh, no. Okay. All right.
>> What do you mean? Okay. That's all you say. Name dropper.
>> But none of that impresses me as much. You You've got like a Peabody award and an Emmy award. This is this for writing. You you've been writing daily show. Yeah. And you worked on the Coor.
>> We love you, man.
>> I love you too, man.
>> Thanks for spending some time with us here.
>> Absolutely. Always great
>> making this happen. You know what we're going to talk about?
Mhm.
>> The cutting edge of cosmology
>> cuz any everybody's talking about cosmology all the time,
>> but who gets in there and say, "Where's the edge?"
Yeah.
>> And where's where are people at fisticuffs?
>> Yeah.
>> We We like to mix it up here. Where can we get people at each other's throats?
>> At each other's throats. Cuz then that's actually I mean the history of science shows that's how discoveries emerge. No, I have to say I've been doing a few of these with you and this one has like is really cool, really interesting because there is a lot of back and forth on this and it's really it's really
>> Yeah. Yeah. No, it's good. And a lot of people uh contenders I think is the way to think about that.
>> So uh so we combed the universe to find who would be ideal in this conversation and we found an old friend and colleague of mine, Adam Reese. Adam, welcome to Star Talk.
>> Thank you for having me.
>> Welcome to my office here at the Hayden Planetarium.
>> Excellent.
>> Yeah.
>> I mean, I was just wandering around the museum and you guys pulled me in.
>> You were He was with a bunch of children. He was and and his hand was being held by a teacher.
>> Yeah. He might rebel and have a Nobel Prize, but apparently he gets lost in large spaces. Everybody,
>> so you're at the John's Hopkins University. You're the the Bloomberg distinguished professor there.
>> Bloomberg. He's a friend of uh my wife worked for him. He has a background in physics and engineering and came through Johns Hopkins and donated a whole building called the Bloomberg Center for Physics and Astronomy.
>> Yeah. So, there's some good Bloomberg action down there in Baltimore.
>> Then he ruined everything when he created bike lanes in New York City.
>> I'm telling you, let's spend an hour on that, Mr. Nobel Laurette. Can we fix that?
>> Says the man who does not ride a bicycle.
>> Exactly.
>> Okay. Uh many people don't know that the space telescope science institute is which was responsible for receiving all the data from Hubble and other telescopes spaceorn is colllocated on the campus of Johns Hopkins University. That's right.
>> So you also have a position there as well.
>> That's right. That's right. That's where we have the joystick.
>> Okay.
>> I'm going to leave that right there.
>> We have to add that you are a Nobel laureate.
>> That's right.
>> That's badass.
>> Yeah. And I I think if you had a business card, just say no. That's all. You don't need anything else.
>> No phone number.
>> No phone.
>> You just think you want to talk to him. He's so smart. He calls it.
>> So remind me what year you won that.
>> Uh we won it in 2011.
>> You won the Nobel Prize. And that year was split three ways. So who are the other two recipients?
>> Uh Brian Schmidt and Saul Pearl Mutter.
>> And Saul I remember was a West Coast guy.
>> Right.
>> Right. Out of
>> he led the supernova cosmology project.
>> Okay. with the same intent of making the kind of measurements you were making. That's right. With Brian Schmidt,
>> right?
>> Right. Okay.
>> And we were members of the High Z supernova team.
>> High Z would be high red shift. Correct. Supernova team. And it was given to you specifically for
>> the discovery of the accelerating expansion of the universe.
>> Which today we just call dark energy.
>> Well, dark energy is we think the driving mechanism for the acceleration. Okay. There's still a lot we're trying to understand about the nature of dark energy. Well, get back to work,
>> please.
>> So, I'm going to say welcome to Star Talk.
>> Thank you. Yeah,
>> it's an honor to be here.
>> Yeah. And so, you are co-discoverer of a this I cuz growing up I mean going I don't mean growing up as a kid. I
>> coming through school
>> in graduate school,
>> we always knew that there was this term in Einstein's equation that it referred to like a negative gravity or something. It was legit mathematically legitimate,
>> but no one had a negative. What is that? Nobody accounted. But no, what is it? It's just a math thing. So every time we had a conversation about the expanding universe, you had to explicitly say, "We're going to assume this is zero
>> because we don't what what are we going to do?"
>> So it's expanding at a constant rate basically.
>> Or or or expanding only according to what the galaxies tell it to do. Got it. This would be an extra thing going on. Okay.
>> And you were just too lazy to explore that. Is that what happened?
>> No. Apparently this gentleman was not too lazy to explore it. And he's saying,
>> "I wonder if that is a thing." Okay. And there you go.
>> Where? So, so first catch us up on being co-discoverer of the accelerating universe through these equations that I'm describing here and and you're getting data. What what was your data?
>> Sure. So, um, so as you said, this term that Einstein had put in, which he actually put in for a good reason. At the time, he thought the universe was static and so this term was needed to balance the attractive gravity.
>> Otherwise, the universe would just collapse on itself. correct? Then it would just collapse. And then um so astronomers at the time told him the universe was static because they thought the universe was the Milky Way galaxy. They thought that was already everything. And of course uh it turns out there are galaxies out there. They're moving further apart. Hubble and others showed that. And
>> Hubble the man.
>> Hubble the man.
>> Hubble was a man before he was a telescope. That's right.
>> More like the Robocop version of
>> But he would be mistaken for a telescope at a lot of parties. The shape of a body. The famous story is that once Hubble showed that Einstein that the universe was expanding in which case it was unnecessary to have this kind of repulsive gravity to balance things and it was kind of dropped to the side but as we know in physics once something is possible it is always there unless you have evidence that it doesn't exist. So
>> right very important bit of scientific wisdom there.
>> So let's jump to the 1990s and uh astronomers are looking for
>> So that was the 1920s.
>> That was 1920s. Yes. So, we're in the 1990s now and astronomers think there's some matter in the universe. And the question is, is there enough matter to stop the expansion of the universe? Like, you know, launching a rocket, does it have escape velocity from the gravity?
>> Is that some is that matter something that would later be called dark energy? Is that sort of
>> No, this is what we called dark matter really. At the time, we knew there was a lot of matter. Most of it was dark. We knew this because there was extra gravity. the the rate at which galaxies or uh stars orbited galaxies, the stars would have flung out if there wasn't this extra matter. So, we knew all that and then the question was is there the critical amount, the amount that would halt the expansion or would the universe expand forever? And so, by the late 1990s, the best way to do this was to measure the expansion rate of the universe in the past and compare it to the expansion rate in the present and see if it was slowing down enough to stop. Oh,
>> and this is where the distance ladder comes in in terms of measurement.
>> Yeah. How do you know how far away I mean nearby? It's hard enough just nearby. I guess you can use parallax on stars, but these stars are sitting on our noses and we have whole galaxies nearby and beyond, right?
>> So, what meth you had to like really define a method to do this?
>> Yeah. So, so you know, parallax is great. Having a tape measure and running it out somewhere is great, but these just don't work very well. You can get those at Home Depot.
>> Yeah, I know. But not one that long. Uh
>> with your Home Depot tape measure, you can get to things that are walking distance of you. All right. But there are stars out there that, you know, you can't do, you know, radar beaming to them because they're light years away.
>> So you have to use parallax, a form of geometry that had its limitations because of the angles of the geometry.
>> You're just trying to make up for getting something wrong a minute ago.
>> I didn't. It's
>> pretty good. But that's good. You did good there. You did good. So So if you you have your two eyes and if you you can put your thumb and you just look at your thumb with one eye
>> and then you switch eyes and then your thumb is like moving back and forth.
>> Hang on. I need a manicure.
>> Wait, what am I doing now?
>> Yeah. Yeah. You look with one eye and switch eyes and your thumb will will shift back and forth as you shift. Right. It turns out the amount that that shifts and the distance between your two eyes uniquely determines how far away your thumb is,
>> which is then used.
>> So try this. Put your thumb here and do the same thing.
>> So now it it separates even more. Yes.
>> So that's an angle. You can measure the angle. We know how far your eyes are. You know exactly how far
>> this with my hand so I don't have to look at you.
>> Well, that works either way.
>> I'm blotted both ways. So uh how what are our eyes? How do we do this with astronomically? Well, you can take a picture of a star and there's a background stars behind it and then six months later take another picture of that same star.
>> Mhm.
>> Now the width of your eyeballs is the diameter of Earth's orbit. Now that's good.
>> So now you can measure.
>> Now you get that and you see how much it varies. You know how the the diameter of our orbit. Bada bing, we get the distance to it. And we have sent telescopes into space to measure this exquisitly far beyond what's even possible from Earth's surface. Very reliable. No, no, it's a a telescope called Gaya.
>> Gaya. G A I A. So now
>> we trust these cuz it's like geometry. We got this
>> right.
>> But now you have to go beyond that and you don't get to use parallax.
>> Right. Right. So then you have to use another method. Okay. And there are methods that we use here on Earth like a lighthouse. So if you're a ship captain, you want to make sure you're far from shore. You want to make sure a lighthouse, which you know is very luminous, looks very faint and assures you, wow, it's I have to be far away. And we can actually do that quantitatively by measuring how bright the lighthouse actually appears. So uh in
>> I like that analogy. It's a good one. Yeah. In the past, um, there was a class of pulsating stars called sephiid variables, uh, that have this wonderful property that they tell us whether they're a very luminous lighthouse or a not very luminous lighthouse depending on how frequently they pulsate. And they're about 100,000 times the luminosity of the sun. And so the big advantage is if you want to measure far, you better have a very powerful lighthouse. So they were good for a while, but we had to go out much further. That's the second is that's the second rung of the distance ladder, right?
>> Yeah, I think so. Yeah, call it that. It's the third rung after the Home Depot tape.
>> That's right.
>> So, so you said something important there. It 100,000 times brighter than the sun, which means the sun at those distances, we would just never even see it.
>> Right. That's right.
>> It's not useful.
>> Right. That's right. So, the name of the game at this point is to be able to measure truly cosmological distances very far out. We're really just in search of an ever more luminous standard candle. something that you can just see far away. If you can't see it, you can't measure the distance to
>> for me. Explain uh the standard candle and that my understanding is that we don't really know what that luminosity is.
>> So a standard candle is any object whose luminosity is uniform. So when we see a standard candle and it's uniform, when it appears dim, that tells us it's far away,
>> right? And we know that they're we know why they're uniform. That's been
>> correct. We know we we have we start out with very good theoretical understanding and then ultimately we have empirical understanding which shows us that. So by the 1990s these sephiid variables are just not luminous enough. We really need things that are billions of times more luminous than the sun because we now want to look so far back that the universe has changed that the universe is younger that it was expanding at a different rate. So uh this requires us to go back billions of light years. So it's like when you're a kid you you shoot up when summer Neil's like
>> in height
>> four.
>> Yes.
>> Or shoot up drug. I don't know. It's you.
>> I don't know what you were doing.
>> I don't know what you I don't know how what kind of job.
>> I'm from the streets everybody.
>> I grew up on the streets. No, you shoot up in height like in one you go from 49 to 5'9 but then as you get older it progresses slowly. So that's sort of the idea here in very rudimentary terms. When you're going back in the early stages of the universe, you're looking
>> you're going back to the younger
>> the younger where the expansion is faster.
>> No, we don't know that yet.
>> Well, it could be.
>> It could be slower.
>> So let's not jump the gun. So So by the late 1990s, we had known about supernovi. Gosh, going back to the, you know, ancient Chinese, a star would suddenly appear where you had saw nothing. And we came to realize that these are exploding stars that are billions of times the luminosity of the sun.
>> In fact, the very word supernova, nova means new.
>> Yeah.
>> In Latin. And so a really bright new thing called supernova. And only we would later learn that it started dying at the end of its life.
>> Right. My wife calls me a supernova.
>> Dying at the end feel about that. But uh uh anyway uh
>> he's still in therapy. We'll let him.
>> I didn't mean to look in your eyes when I said that. So what we came to really realize in the 1990s is there's two completely different ways nature produces this kind of supernova explosion and that's very important. One way is you have a very massive star that uh loses its ability to produce energy at its core and producing energy was the way it produced uh pressure that held back gravity and so it's uh a very dangerous thing for a star like this to lose the ability to do that. It's basically lost its structure and so it will implode followed by an explosion. And those are very bright. They're great. But the problem is they come over a wide range. That could have been a very massive star or a medium star or that could have been a star that when it collapsed turned into a black hole in which case we'll see almost nothing.
>> So they're not as reliable as a standard camera.
>> So it's not going to be a good standard. Not a standard candle.
>> But it's not a good standard candle. And then we realized hiding in this distribution of all kinds of different exploding things was a subclass that were all the same. And that is a completely different mechanism. It's called a type 1A supernova. And that occurs when you have the core of an old star like our sun will become called a white dwarf which is in a very special state. It's holding itself up against gravity because of uh because of quantum mechanics really. Um and it it can only be stable up to a certain mass known as the Chandra Seekar limit after the famous Indian astrophys physicist Chandra Sar who in the 1930s
>> showed that a star could only sustain itself up to about 1.4 times the mass of the sun. So now imagine this you have the a white dwarf star. It's sitting there. It's it's less massive than this chandra sear limit. Maybe it's in the mass of our sun
>> and minding its own business at this point. is doing nothing and it would be happy that way. It would just cool off and live its whole life that way. Cooling, cooling, radiating. But what if it has a friend and you know with friends like these who needs enemies? These are a star orbiting that star and they get too close we think and mass starts to transfer over we think and the details of exactly how this occurs are debated but somehow
>> how the mass transfer is not clear.
>> Exactly. Whether it's like they actually merged or it was a gradual process. Can I just say something between Einstein and you guys? You seem to leave a lot of stuff off to the side. We're not sure, but we'll just go whatever.
>> Well, because he's after the consequence of what happened.
>> Correct. That's correct. That'll be clear in a minute. Okay. So, anyway, so somehow mass transfers over and when it reaches that chander limit, it's like boom, a thermonuclear explosion runs through the star. Okay. And what's so great about this is
>> they always blow up at just about that same mass, very close to that. So, this is a standard candle. This is something you you recognize it far away. And how do we recognize it? It has a certain spectrum. It has a certain chemical fingerprint.
>> And this was observable within the Milky Way because that was a distance that we could observe this or we
>> Oh, we could observe these beyond. We could observe these at some of the most distant galaxies
>> because of the telescopes.
>> Now, they're incredibly rare. There's only one in a galaxy like ours per century, but there's no real limit of galaxies. So if we can take a wide enough image that contains hundreds of thousands of galaxies and then come back you know a month later you know what turned out to be oh so unlikely to happen is like guaranteed to happen. It's like winning the lottery because you buy all the lottery tickets. Right.
>> Chuck last year we all went to your comedy show.
>> Yes.
>> Right here in Manhattan.
>> That's right.
>> And what what was the title? What did you call it?
>> It's called Chuck Nice. Just smart enough because I sit next to you. No, we love you because you were you have a science literacy and you don't let anything by.
>> Yeah. Well, I took that and I put it on comedy special and you were there in the audience and
>> you have a clip you can show us.
>> Absolutely. And just like if I were on the Tonight Show, I have no idea what it is, but check it out.
>> I am too lazy not to believe in God. Okay. Cuz when you ponder the origins of the universe, that gets very, very deep. a singularity just that by itself something that is infinitely hot and infinitely dense. How can it be infinitely dense? At some point you can't patch it in anymore like what? And at that point I'm just like God did it. The December 30th you'll be able to come to Star Talk and you'll be able to see the whole comedy special. So bring in the new year with some science, dumbass. Please head to the Star Talk watch page on YouTube and tap notify me so you'll get a ping when we go live. and then we'll watch it together. Be there.
>> And you began this in graduate school if I remember correctly. And that whole group with uh who the head guy on that group?
>> Brian Schmidt and Bob Kersner and the the Chilean group for the Colontool which you know very well.
>> Um, and so what changed the game was in the 1990s we both came to realize this class was special. It wasn't like the other supernovi. And the advent of large cameras by those standards on telescopes that had a big enough field of view that you could simultaneously stare at 100,000 galaxies and actually have a chance to do this experiment, actually find supernovi on demand.
>> Right. So you didn't have to wait around for one to show up and then look at it. You would like we're going to find three supernova tonight.
>> Right. Right. And it was actually quite amazing because back in the day when the Hubble Spellbased telescope was a new thing and it was incredibly valuable to get time, we would propose for time and say, "Uh, we'll tell you exactly where the supernova is on Tuesday so you could start observing it Thursday." And they were like, "You're going to what?" Like you're going to you're going to tell us where a supernova is on Tuesday. And we're like, "Maybe Monday night if the computer's operating fast enough."
>> And they're like, you know, I got a dinner. Can we pull that off?
>> But it was, you know, if we had bad weather or something. And it was scary too cuz it was like and if we don't just stare at blank sky which is no astronomer wants to use the most capable facility to just like stare at night.
>> This type 1A supernovi are visible halfway across the the universe. That's right.
>> But they're only useful as a standard candle once you can calibrate those that are closer that have some overlap maybe with the sephiids. Is that right? for the discovery of the 1990s that the expansion of the universe and here's the the big spoiler alert that it was accelerating not decelerating. You don't even have to calibrate them because you're only using them as relative measures. You're saying you're saying how much was the universe expanding back then relative to how much it's expanding now. Even if I don't know an absolute basically divides out Neil is handsome but relative to me not so much. Okay. Um, so
>> I'd forgotten that's
>> important and it's a very important. So the two the two stories we're going to tell disconnect in that way. And so by the late 1990s even if I didn't know the absolute the true luminosity was it 10 billion solar luminosities or 8 billion solar luminosities. What I could say is oh that distant one was so faint that it is you know 10 times further away than this one. Whatever the true
>> but you've got you got a history or so you got a whole string of pearls through time and space.
>> Like you're a super sleuth in a way. It's like you're a detective sort of using evidence. But within the distance ladder, you have these three rungs. And what strikes me is four rungs. Sorry. You have but this is to be clear this entire discovery of the accelerating universe only depended on one rung internally to itself. So
>> but if a Sophia is a sort of got a you know okay if dust affects its brightness right now. So now that rung is sort of u there's there's some weakness in that rung which can propagate through the rest of the distance ladder. So how are we accounting for there's so much we don't know dust right or other components that could sort of affect one rung of the ladder could then sort of throw off the entire calculation
>> or even dust in your even in your relative comparisons the dust would give you the wrong distance
>> right so when I was a graduate student this was the the part of my thesis was to figure out how to contend with dust um in these type 1 supernova observations so it turns out that dust makes things dimmer which would fool you into thinking it's further further away. That's very bad. Okay. But it does something else, too.
>> It makes light look redder when the light passes through it. So, look at a sunset, right? Not only does the sun look dimmer, but it also looks redder because
>> So, if you're seeing the red, then you know that's there must be dust.
>> Exactly.
>> But, but then how do you determine how much dust?
>> You look at some supernova where there is no dust, like it's way far out of its galaxy or it's the blest one you've ever seen or something like that. So, the power of the red the dust matter
>> the re the redder it is the more dust
>> right and in fact if you really do this right differentially all you need to know is it's so much redder than other ones and that then that affects how much difference it is it's like that you that you're sort of you you're getting these pieces of evidence and building that's fascinating to me
>> so much science happens that way people think it's just one question and one answer and one experiment techniques oh my gosh so much
>> well what's striking me in all of what you do not so much Neil but you um is uh you hit a roadblock and find a way around it,
>> right? It's all solving problems. We need clever people exactly on the team.
>> It's fascinating.
>> Okay, so now if I remember correctly, the goal wasn't so much to measure this Einstein term, was it?
>> No idea. No, it wasn't even on my radar screen.
>> It was just to lay it out. It's just to see what's going on.
>> It was just to measure how much the expansion was slowing.
>> Okay.
>> Right. And was it slow?
>> Tell me about your equations. Tell me what you you wrote stuff.
>> I wrote stuff down. Yes. Yeah. So I wrote down some standard equations of what should have worked for the data which is uh a
>> anyone would know. Just I want you to know.
>> And you thought you were thinking it was slowing down the expansion. Not only that, I was so sure it was slowing down because that's what everybody told me and I was in graduate school at the time was that I said I said okay so the supernovi will measure the slowing and I'll immediately convert that to what is the mass density of our universe this famous number called omega m
>> and then and then apply that to our universe right away yes but right away that number tells you what we want to know if omega m is greater than one there's so much matter in the universe it will recolapse. If it's less than one, it will expand forever. Omega m equal one is called a critical universe or the critical it's it's the the mass that it's the gravity that the and mass that the earth would have to have to launch a rocket and have it be escape velocity.
>> So, is this the big freeze, the big rip, and the big crunch?
>> No, we'll get to that.
>> Okay,
>> we'll get to that.
>> So, can you catch up cuz I'm really I'm working slow for you. So, I had a baby.
>> Come on, guys. I got stuff to do. There's a supernova happening in an hour. Yeah, that's a good point. You've been listening. So, so there's a very simple sequence here is supernova measure deceleration related to how much matter is in the universe that's causing the slowing expansion. So when I
>> wrote my computer program, I said, "Hey computer, fit that and tell me the answer." And the answer it spit back was negative mass. Okay, now there's no such thing as negative mass. That's not like a physics option, but you know, computers don't know physics. And so you give them very simple instructions. Measure deceleration, turn into mass. And I hadn't yet noticed that the data was saying the universe was accelerating. So it was like, okay, you want me to make that equation work? I'll just flip the sign over here on matter. Now it's negative. And I'm like, that isn't right. You can't do that in physics. We can't report that. And so after doing a lot of checks, I was like, well, what could do that? And then you know it was like all the classes we ever took was like you know Einstein once had suggested something that could go the other way. You put that into the equations and it like fit like a glove.
>> Bada bing.
>> Yeah.
>> And you've got it's not just expanding but it's accelerating in its expansion. Correct.
>> And now it's why and that gets you to dark energy.
>> Right. And so what is it? So you know
>> you you you made them you made the measurement that it exists
>> right
>> which is a separate thing from knowing what it is you know
>> the interpretation. Yeah. And just to mention um
>> just people need to that needs to sink in here because
>> the universe is accelerating whatever is doing it.
>> Yeah. We can make measurements of things even if we don't know what's causing it.
>> Well this one it's the how the some of the greatest things happen. And so you you're you're going for A and then you find B. And and and this is going to sound, you know, as a writer in a in a room in comedy shows, you could give us an assignment. Write a joke about, I don't know, airplanes travel, right? And nothing great comes. And then just out of that comes a great side bit that ends up being that's how the Back in Black segment came about at the Daily Show because Yeah. because we were trying to come up with great jokes on these little stories like a Florida man and we're like we don't know what to do with this like give it to him and let him rant. So it's the same it's it's obviously in the arts but it's the same thing. You're going for one thing and in a beautiful way it's like a beautiful mistake in a way or whatever
>> but it's also the thing that still to this day we don't know for sure or understand well. I mean we could say the universe is accelerating. There's no question about that. But what is causing it? You know, we're still relying on Einstein's cosmological constant or more generally dark energy, but we don't understand the physics of that at all.
>> Well, get back to work, dude.
>> Yeah. Well, what are you doing here?
>> What? Yeah, you made the discovery. Now, I expect part two of this.
>> Well, actually, you know, there's something in my pocket, you know? It's been I've been sitting on it and it's like bothering me. You ever get like a pebble and you're like sitting and it's like, "OH YEAH, THIS." OH,
>> WOW.
>> Wait a minute.
>> There you go.
>> Wait a minute.
>> Wow. Did you buy that on the street?
>> Wait. It's in the gift shop downstairs.
>> I got a guy.
>> Don't bite it cuz it's
>> got bling that's bigger than this at the club.
>> Hanging out.
>> So just for context, they didn't give us the Nobel Prize for discovering dark energy, but for discovering that the expansion is accelerating. accelerating. Right. Right. Right.
>> That's why if it would be bigger if you it was more significant.
>> It's just a little discovery. So they give you the baby. This is the baby Nobel Prize. That's right. I'm sorry.
>> So this I guess that's Alfred Nobel on the cover on the cover there. Very cool. Is this actually gold?
>> Yeah.
>> Or is it gold? Like it's I don't know what it's 18 karat or something.
>> 18 karat.
>> I know it's worth a lot.
>> He gave it to me.
>> It's It's worth a lot today. Have you seen the price of gold?
>> 4,000. I'm worried walking out on the street with this. There's a funny story about Brian Schmidt taking his on the airplane and the um the uh TSA agents were very confused because when they x-rayed his backpack, it just showed up as a hole in his backpack cuz the gold is in your backpack and he was like he took it out and they go what is that? And they said who gave that to you? He said the king of Sweden. What did he give it to you for? for discovering the expan accelerating expansion of the universe. They were dead panned though. So
>> basically this guy discovered that you wouldn't be here if I wouldn't be talking to you right now.
>> Can I just say something? You're brilliant and I'm impressed with that. But I'm more impressed that you're walking around New York City with that in your pocket.
>> I hear people are nice here.
>> So then it doesn't come with a a thing around your neck like like the swimmer, you know?
>> Yes. Oh, it's Mark Spitz. We had seven. Stay modern here. Um,
>> no, I'm going with Mark Phelps. I was a swimmer Phelps.
>> Michael Phelps.
>> Michael Phelps. This is heavy.
>> Yes. It's probably got at least we got to give to our figure out how much gold is actually in it.
>> And And you know, where where did the gold come from that was in it?
>> Oh, SUPERNOVI.
>> OH MY GOD. IT'S ALL COMING FULL CIRCLE. Full circle.
>> They said, in fact, yeah. They said, "We want to give you something that really represents the work you did." And they was like, "Let's find a supernova by Tuesday and we'll get some little bits and we'll make something."
>> Listen, I know a guy that can melt that down into a watch if you want. That's beautiful.
>> You'd surely know in here at the American Museum of Natural History in our backyard. It's our yard, but it's run by the city. The city controls it, including the dog run. But there's a monument there put there by one of the
>> one of the Swedish uh pharmaceutical companies
>> in the Teddy Roosevelt
>> in the park. And it's in honor of all the American Nobel Prize winners. And my boy's name is on that on that statue. They're all carved.
>> They're chiselled. Chiseled in.
>> Yeah.
>> My boy's on that statue right there near the dog
>> run.
>> Are you saying dogs watch it as they poop?
>> So what? We live on 79th Street right around the corner from here. My dog pees on your name. I'm sorry.
>> My name is actually pretty high up. You would have to climb up.
>> My dog is well endowed. That's all I'm saying. He can reach high.
>> Okay. So say what you said again because it's important. You you got this not for knowing what dark energy is,
>> right?
>> But for the discovery that it exists.
>> For the discovery that this phenomenon, the universe accelerating exists, which everybody attributes to dark energy because normal gravity from matter doesn't do that.
>> Doesn't do that.
>> It goes the other direction. It's like the other direction that showed up.
>> It's like having a car and like all you've ever done is hit the brake and then one day the car just takes off and you're like, "How did the brake do that?" And it's like, no, a different pedal, the gas pedal did that.
>> And I think you've started to move toward that the idea that
>> dark energy determines the fate of our universe. Right. And that's where it becomes which makes you a real Debbie Downer. Uh, but there's Big Freeze, there's Right. There's Big Rip, and there's Big Crunch, which actually feels like Ben and Jared's Ben and Jerry's anxiety flavors. Like
>> you would be the big freeze cuz you're closed off emotionally. I You would be the big rip. You're strong. And I'd be the big crunch cuz I'm a baby. Uh, everything the big crunch I think is not in the cards.
>> Actually, everything's on the table still to be honest with you. And yeah, in light of some more recent results on dark energy where it may look like it's thawing or weakening.
>> Well, let's get into that. Let's get into that like right now. We're all up to speed now
>> and we have like 3 minutes left.
>> Yeah. Yeah. So, the universe is accelerating and we have a new model of the universe which goes by the sexy name Lambda CDM.
>> Okay. which encompasses everything we know about the universe. The lambda part means there's dark energy.
>> This is the astrophysicist version of a standard model. Correct. I guess correct, right? And the CDM part is called dark matter. It means there's a lot of dark matter in the universe. But there are other things uh in that description like the universe is relatively flat. There's a certain number of nutrinos particles. It's everything we know. It's an inventory of the universe, but 96% of it is still kind of unknown stuff. in fact very unknown
>> that's the dark matter and dark energy combined
>> so by the early 2000s it was recognized well we want to understand this more and so there were folks who were going to measure the radiation left over from the big bang the cosmic microwave background with a series of satellites WAP plank and they were going to very precisely determine the state of the universe as it existed shortly after the big bang the folks who were measuring the cosmic microwave background got a very beautiful baby picture of the universe that has a lot of uh fine grained information about the state of the universe and
>> excess radiation for lack of a better term.
>> Uh, yeah. No, but it's a it's a description of what the early soup of the universe looked like, whether how much what were barons, normal matter, how much was dark matter, uh, photons,
>> a really important snapshot of what was going on. Yeah. And so the the great success was the picture they got of the universe was the same model that we were essentially seeing from these more local observations. This yeah there's a lot of dark energy. There's a lot of dark matter. Everything fit except one thing didn't fit which is uh it also predicts how fast the universe should be expanding today. And that number called the Hubble constant is something we also can learn by this route that we've been describing where you you measure parallax and you measure stars and you measure supernovi. And using that route, you can measure how fast the universe actually is expanding today. It would be like, you know, having a 2-year-old kid. You measure their height, right? Then you predict how tall they'll become. And then you measure them when they get to that full height. And what if it was off by like a foot or something? You'd say
>> you'd disown the kid.
>> Yeah. You'd disappoint. You're right. He's still he's still in family therapy.
>> I understand the fact that these two routes from the early or late side of the universe on the one hand tell us the same rough more than rough story. Basic story. Yeah. Like they're like doppelganger universes except one is younger and expanding faster and one is older and expanding more slowly.
>> That's the 71 and the 67.
>> The 731 explain the numerical values. Numerical values of the con.
>> That's right. And this Hubble tension emerged about 10 years ago.
>> Tension as in the two numbers are not agreeing.
>> As in the two numbers are not agreeing.
>> Now I have to butt in. I'm in graduate school and we're fighting over whether the Hubble constant is 50 or 100. And so you're telling me you're now fighting over whether it's 67 and 72, whatever. And I I don't I don't have sympathy for that.
>> No, no, no. I My whole time in graduate school, we didn't know the size of the universe by a factor of two. And you have to complain in about a few%.
>> So now let me get out of here. Let me leave your Nobel Prize.
>> Let me let me tell you why this is so much more interesting than that was. Okay. When people were measuring 50 or 100, they were measuring the same thing. They were measuring how fast the universe is expanding here today. Often measuring the distance to the same galaxies, the same star. When you say here, when you say here today, you mean within the Milky Way, right? Or just regional universe. So what you know so if I if I told you the length of this table is such and such and Neil said no I get a different answer the table has one length right and so this is something it's not that profound one of us is making a mistake the big difference here isant we are measuring opposite ends of the universe and we are using our story of the universe to connect them and so disagreeing in this case has the potential to teach us something profound about the universe whereas disagreeing back then just meant people were making mistakes
>> and when you say profound about the universe but our understanding of physics and the possibility that there could be new physics out there,
>> right? Because how do I go from the early universe to the late universe? I need a I need a function. I need a a piece of math to tell me how do I translate from there to there? It's like that kid, you know, they were 2 years old, then they're an adult. How did you guess how tall they would be? Well, you had a growth chart, right? The growth chart is our model of the universe formula. But, you know, with a growth chart for a kid,
>> but it's not precise.
>> Well, you've seen a lot of kids grow up, right? So, you you have a lot of confidence in the growth chart because they follow that. We only have one universe and most of it's made of stuff we don't really understand. We'll get another universe then.
>> So work a little harder.
>> So you know the fact that they disagree and and Neil makes a good point. It's it's not a big disagreement in absolute sense. It's like 9%. But our measurements have gotten so precise that it's five or six times the error bar between them.
>> I've banned the term error bar because no one knows what the hell that means. Okay. The uncertainty.
>> Sure. the the measurement of the uncertainty of each of those two two quantities does not leave room for overlap.
>> That's right. Okay.
>> Okay. So, there you go.
>> So, from someone who's not as bright as
>> well, you him I'm same. But now, could it be that dark mean this means that dark energy is shifting like sort of like a petulant teenager? Like it's calm and steady and then all of a sudden you never understood me Einstein and it's slamming the door on you, right? Like is it that possibility? Is that happening?
>> Yes. I would say that we may be discovering that what we call dark energy is a general phenomenon that happens all the time in the history of the universe. So let me tell you this. We invoke dark energy shortly after the big
Bang in a period called inflation to inflate the universe. Okay? We give it the name inflation, but it's dark energy. Okay? We have the universe currently accelerating now. That's dark energy. By the way, it was called inflation because the idea was advanced in the 1970s when we had like 18% inflation.
>> The word was had a lot of currency inflation, right?
>> Yes. It was under President Carter and inflation win button. Win whip inflation now. Remember that win.
>> But we have but so we have other we have things something uh in physics that's important part of physics called the Higs field which is a field in space that gives rise to mass for particles. That is an energy an invisible energy in space. So this is a regular feature now in physics is to recognize that there are invisible energy fields and in Einstein's theory of gravity an in an invisible energy field plus Einstein's theory of gravity automatically has this consequence of giving a push to the universe and so I would say at this point we are sort of
>> watching the universe to sort of try to learn when episodes like this may occur. Maybe it maybe there's only two. Maybe there's 10. Maybe
>> is that the new that there's from my understanding there's five possible reasons for this Hubble tension. Is that the new new dark energy theory or is that the
>> Yeah. So there's an early dark energy theory which posits a third episode of dark energy, not inflation. That was the beginning, not the current one. So
>> is that the turbo boost one or is it some something different?
>> I don't know about the turbo boost, but it goes by the name early dark energy. It's the same concept is that you know if you give a kick somewhere along the way then using the simple form of the cosmological model to connect two end points you know you're not going to quite get things right.
>> Doesn't it have to be motivated to manifest itself and so what would manifest a a pulse of dark energy in a place unexpected
>> right it usually ties to a particle and it usually ties to some event some symmetry breaking or something like that and it becomes very theoretical. I mean, theorists argue that sounds reasonable. That doesn't sound reasonable. To me, they all sound kind of like la. But, you know, I look at it like, all right, how many times have you invoked the tooth fairy in this conversation? And, you know, I've learned that like a close cousin of the tooth fairy is not a new invocation of the tooth fairy. It's just her cousin, you know? And so, to me, there's a big tooth fairy that's that we've already been living with for a long time. And these are like
>> revisits of the tooth fairy.
>> All right. So
>> I'm an observer so I this is not you know I look at stuff.
>> Is there a way to reconcile this without having to invoke another tooth fairy?
>> Yes.
>> You invoke Santa Cl.
>> Exactly.
>> Well, first of all,
>> big fan.
>> There are a lot of ideas.
>> Better gifts.
>> Yeah. One way to play the game is to change the the way the universe looked before the this radiation from the big bang leaks out. So
>> how do you change the way it looks? So change our understanding of we're not changing it. We don't think we go.
>> It's a it's a kind of a plasma soup. And so even something as subtle as saying if there was a magnetic field in it that could start this process of collapsing by
>> there could be new particles.
>> There could be a new particle. That is absolutely another possibility. It it rearranges the way energy is distributed in the early universe. Um, and so there are many ideas electron uh mass decaying interactions between dark matter. See when physicists start out with the cosmic microwave background they have to build a model of what's going on in the universe. So this would be like some new attribute going on there or it could be something late in the universe like as dark energy emerges it's not this cosmological constant which means static uniform unchanging but it has some kind of mind of its own.
>> Right? So you have your option to either make the early universe match the current universe or the current universe match the other or have them do something both that can meet in the middle.
>> That's exactly right.
>> Okay. So how uncertain are the nearby measurements? Seems to me those should be pretty secure.
>> Yeah. So I would say now after you know 10 years of scrutiny they're pretty darn good. Um, what I can tell you is, you know, having made a lot of those measurements with the Hubble Space Telescope, along came the James Web Space Telescope, and it was like, I don't know, it was like riding the the your first little bike when you were a kid, and then like somebody gives you a 10-speed, you're like, "Oh my god." And you're like doing laps around what you did. So, I've been doing laps around the the work that I've been doing over the last few years, and the images are pristine, the measurements are textbook, but the answer is the same. Um, and so the fact that James Webb is confirming what Hubble is confirming is confirming that this is a real problem.
>> And that deserves I got to emphasize this because what he just said is
>> you can make measurements with whatever precision your equipment allows
>> and then you extract from that an answer in the den of cosmic noise. It's kind of saying this. If you have better data and you get the same answer, you you're good. That's right. And the signal to noise is 10 times higher for the measurement I'm making with James Web than it was for Hubble. So if you get a full order of magnitude improvement and nothing changes, that's very compelling.
>> So for those at home in it's in simplified terms, there was a debate. Well, maybe the math or the way we're doing the math is off. And then the web telescope enters the picture and tells you maybe not. So now you have to go to the idea that maybe there's something about the world of cosmology that we're not understanding or there's something new or there's new
>> subtlety I'm going to say or some subtlety something being lost in translation between the the universe we see and how we transform it to these sort of mathematical models like this is the sky and the telescopes confirm that is the way the sky looks but perhaps there's some subtlety in the way we translate that into math or we translate to the beginning of Fine.
>> All right. Let me go back 130 years.
>> Yes.
>> I think
>> that's you living in the past.
>> Go ahead. When I was a kid,
>> go back then.
>> Yeah. Let's go back.
>> We were riding high on classical physics.
>> Yes.
>> And people said, "Look, there's not much left to discover in the universe. We got this. We got Newton. We we got thermodynamics. We we got this. And there just a few clouds on the horizon that
>> the procession of Mercury isn't quite working out.
>> Yeah. But we we'll solve that soon.
>> It's just another planet out there.
>> So don't go into physics because right
>> it's about to end.
>> Bada bing, quantum physics comes up and special relativity and general relativity and and all that came with that,
>> right? Is there something lurking
>> right
>> in in the in the in the dark in the woods right
>> that will need a much bigger transformation of our understanding than just meddling in here and there
>> right the answer is I don't know but what I
>> good scientist
>> but but I do know
>> I was hoping for an answer
>> I got to be honest with you
>> I do know the process
>> I don't want to die
>> soon here's the process we're very happy with the model, the science we have, we go out and we predict experiments and we do things and then you start to build up these cracks or tensions, little funny things. The procession of Mercury is not following Newton's theory. Uh, you know, there's supposed to be an ether out there and we're supposed to be traveling through it, so the speed of light should be different in different directions. We don't see that. Hm. What's going on there? You start to build up these things and
>> it's like holding back the water in a dyke.
>> Right.
>> Right. You say you just plug this hole. Did that work?
>> Right. And when somebody comes along, I'll say Einstein in 1916, right? Uh
>> he comes up with a brilliant re-imag re-imagination of physics which first does something very important. It explains or fits everything we already knew. You can't go and lose that, right? And then all these puzzles get solved. He the first thing that Einstein supposedly did after he developed general relativity was he looked back at this procession of Mercury. This problem that Mercury uh its orbit is itself rotating very slowly around the sun. Um unlike the other planets and nobody knew why they thought maybe there was another planet between Mercury and the sun. Einstein chose
>> Vulcan
>> cuz it would be hot
>> called Vulcan. We just invented. We were perfectly happy to say it's Vulcan is there. We can't see it. It's too close to the sun. It get in the glare.
>> This was not unreasonable because when the planet Uranus was not traveling where it was supposed to, they invoked a planet Neptune, which they found right where it was supposed to be. So, this is what makes science so much fun and why you can't just play the game like you're studying history and going to predict what's going to happen. Cuz sometimes the planet misbehaves cuz there's some stuff out there you missed. and sometimes it misbehaves because we have the wrong understanding of physics. And in in that case, Einstein uh showed that his theory would explain Mercury's procession because Mercury was living so close to the sun. It was in what we call the strong gravity regime where gravity was operating differently than Newton. So to answer your question, we are collecting these sort of cracks and problems and sometimes that is the kind of harbinger of some certain sort of new revolutionary thing. Sometimes it's the loose thread on a sweater. You know, you pull it and sometimes it was just that annoying thread and that's fine. Or sometimes it unravels the sweater and it's just it's hard to say,
>> right? But we live in a society where we want answers to everything, right? And to the average person, you want an answer. But what this feels like is like you're assembling the universe using like IKEA instructions and then you look at the manual and it's like it doesn't look like the manual and you're like honey what's this extra part?
>> I don't know. It's dark energy and why is there another Allen wrench? Like and so you literally
>> Well, I think what we're saying is a we're not done because everything isn't fitting and b we have this wealth of new facilities which are now coming online that really should help us answer these questions. We have the Nancy Grace Roman telescope.
>> So that's specifically tuned for dark energy. Is that correct?
>> It's going to be particularly good with dark energy.
>> Okay. So So yeah. So we just It's not just another telescope. We got smart people figuring we got this problem. Let's design it.
>> But I'm going to ask what we you both consider a stupid question. If we don't know what it is other than naming it dark energy, how do we know what to build to
>> That's a great question. That's a great So I was actually on this panel uh called the decadal survey that once every decade recommends what to build next and this this is what we thought about and we recommended this in 2010 and the reason is because it takes us decades to build these things. So what if the science questions change as you're building or the techniques change? So we designed the telescope to measure the current techniques best that could be done
>> but also recognized that a telescope that didn't exist was a space-based telescope with a wide field of view. Remember I said earlier in this you need a wide field of view to observe hundreds of thousands of galaxies and that operates in the near infrared which it's very difficult to observe in the near infrared from the ground because the sky is very bright.
>> Define near infrared.
>> Near infrared are wavelengths that are redder than red.
>> So longer wavelengths than that but but it's near it sits closer to the visible spectrum than the far infrared. So near and far it's stupid words but we're stuck with them. So the whole infrared part of the spectrum sits adjacent to the to the
>> right
>> sits adjacent to red, orange, yellow, green, blue, violet sits adjacent to that and those wavelengths that are near visible. We call this near and then far. That's all. It's not deeper than that. So so we both build a telescope. We say well today this is what we would want and we think it'll be great. But also tomorrow this will be the capability that doesn't exist. So there's a discovery space capability where you say, you know, this has got to show us new things because we've never looked in that window. We've never opened that door. So it has both elements.
>> Got it.
>> Very important here because that's why why build something that only can see
>> what you're looking for or expect
>> the the breadth of those capabilities. That's what advances the field. But what is see has to feel at times overwhelming to you is it's a constant moving target, right? So you've developed this telescope, but as you just mentioned a minute ago around that new discoveries are being made, new equations are being calculated, right? So this it's it must be maddening because it there's never a firm like yeah this is this is
>> Yeah. What I find very satisfying, I mean, when Neil and I were in graduate school, there were sets of questions about the universe, and those questions have either been answered or have changed to these other ones. So,
>> they're not even interesting anymore.
>> Yeah. The the story, I mean, we were all like, um, how much matter is in the universe and is it going to recolapse? And that isn't even the right
>> one of our colleagues to think about
>> any wrote a book called Just Three Questions or something or some it was some title such as that. And it was because of that book that I now tell the world when they say, "What question do you want to see answered about the universe?" And my answer is, "It's the question I don't yet know to ask
>> because there's a vista that will rise up beneath me from research being done now."
>> So that I will then ask a question undret of today.
>> That's the question I'm thinking of. And our field of cosmology, right, used to jokingly, you said that we only had two and a half facts in cosmology. So we have so much more information. It's such a a great laboratory. Cosmology used to be considered closer to philosophy than physics. And now
>> there's hardly any data.
>> Right. Right. We knew the universe was expanding. We knew there was radiation left over from the big bang. And we knew the sky was dark at night. That was that was about it.
>> There's several people thinking about this tension. Yes.
>> You're not the lone wolf in this. So do you guys are you converging at any point?
>> So we have a fleet of new observatories coming online. We have the Nancy Grace Roman telescope built by NASA to launch next year study dark energy. We have the Vera Rubin telescope. She was the discoverer of dark matter. One of them um and that is a massive groundbased telescope that will cover most of the sky every three or four days.
>> I don't see that one working.
>> A million supernovi. That one is already working. Um, and contradict me all the time.
>> It's going online to discover thousands of asteroids that were not even
>> catalog. Well, no one told me.
>> We we have new CMBB experiments. The Simon's Observatory. Um, we have uh LIGO is just still getting up and going and has great capability. We have we expect new results from Gaia. Um, so there are a lot of facilities that really are well poised to give us answers.
>> So, but is there like a fight out there? Is there a cage match among you guys?
>> Right. So, um I would say five or 10 years ago, the the folks from the CNB particularly were like, well, you local people are probably wrong because um it used to be 50 or 100 and you know that that seems like hard stuff. Okay. And maybe some of us were like plank looks really good, but gee, I really would like some confirmation of that. So, along came new facilities that allows people to check the work. Okay. So uh from the cosmic microwave background we've had these great highresolution CMBB experiments like ACT and SPT one's Princeton mostly one is more at Chicago. Um, and though they have replicated the cosmic microwave background measurements actually they've even pushed the Hubble constant lower not 67 but 66.
>> Are these observatories in Antarctica?
>> Yeah, one's at the South Pole South Pole telescope and the other one's in uh the Atakama in Chile. Okay. Um, and so you need very little water in
>> one of the driest places on earth at a comet depth as is Antarctica. It's one of the driest places on earth.
>> And then nearby we have seen uh the James Web Space Telescope replicate the measurements which was absolutely critical. We've seen other techniques developed that have cross-cheed the measurements and I just came back from a something called the distance network. So, not the distance ladder, but how do we combine all of these different measures simultaneously taking account their covariance? And what we've learned is
>> network great name for that because you it all has to work together.
>> Correct. Correct. It's not just a ladder anymore, but it's like, but what if I have this information and this information? Well, this information was calibrated the same way as this, but it gives me a unique measure to something else.
>> It reminds me of this stupid comic where the the transcontinental railroad
>> and there's the golden spike, which is the last spike, right? and and the railroads come and the tracks don't match up.
>> Well, that is the problem.
>> Hey, they're down there.
>> I told you we were wrong.
>> Right. Right. So, so we've seen a lot of cross-checking and this problem is not going away. It's been getting stronger and stronger. So, I think we have to think hard about what it means. Has your position altered at all? Or you at one point you said, I think the universe is giving us a lesson in cosmic humility. It doesn't seem to be following the manual we had.
>> We can rule out a measurement error as a cause of the Hubble tension with very high confidence. Yes,
>> there's there's some people out there that would sort of say perhaps not. And then
>> well, are you a groupy? You're quoting him from some other program. We have him here. Would you quote him from half the time? He doesn't know what he said.
>> Let me let me define error. Do you do you ever watch baseball?
>> Oh yeah.
>> You know baseball? Okay. So So Aaron America, what do you think you are quarterback? There's a wide receiver. No. Yeah.
>> So I like baseball that they define an error as there was something that was supposed to be done. You know, you're supposed to feel the ground ball
>> and you messed up, right? And it didn't happen and they score that as an error. Okay? But you know making some extraordinary play like climbing the wall and stealing a home run and not doing that is not an error. Right? So in our parlance I would say we are convinced after 10 years of scrutiny that we're not making an error in the baseball sense that that everybody in terms of measurements and stuff everybody appears to be following the manual carefully. Everybody appears to be measuring what they said they're measured. Uh the data is public. This is very important. Unlike back in the 50 or 100 days, half the battle was people had their secret photographic plates in their drawer. And so you'd have a battle and you were like,
>> "None of the drawers in the drawer."
>> Sorry. This isn't where you guys are freaks. This guy's walking around with a piece of metal in his pocket. You got stuff in your drawers.
>> So what's important is all the data that I talk about is in a public archive. So I say this star is this bright. It's right there.
>> I'm sorry. Back up on the 1500.
>> Just be clear. I So I can verify that and I don't have to think that I don't have to just take his word. But back in the day, what do you mean? There were secretly you were not you were not publicly
>> if you were Humble, literally the guy, right? You would go to the 100inch telescope, you put in a photographic plate, you'd take your deep exposure and it was your plate. You took it home to your laboratory and you told people what it said, but they were lectures about it and so forth,
>> but no one else had access to your data. Right
>> now everything is digital and is the point being you've got a lot of people crosschecking and checking democratization of science through these facilities. And so what I will say is in the past when errors are made and errors absolutely happen the baseball kind of errors our community is so good at jumping on those right that I would say within weeks or months that is found when something lasts 10 years when the data was public when people could scrutinize it um then those become the things that are real things. So,
>> and you want to also watch out for whether there's group think
>> and if multiple teams who are otherwise competitors
>> find agreement in what your measurements are. That's a good place to be. Like there were two two groups last in the last couple weeks that were using uh JWST and this method called tip of the red giant branch and they got 74 and 75. They're unrelated to the the more traditional groups that were working. And so the more you see these groups that are independ the value of the Hubble count
>> does the 7475 versus visa v 727 does that trouble you is that down with the 60 no right I mean it's look the full range of measurements people make locally is about 70 to 75 and so that's normal that's kind of a bell curve distribution so people you know the middle is probably around 73 but some people get 75 and some get 70 but the point is
>> you expect that in any random distribution the question is why are why is everybody getting something higher than the early universe at 66 or 67 and that would I don't see how that happens by chance there is this theorist Thomas Burkett and sort of has another explanation for all of this and I wanted to get your thoughts on that
>> so he is a theorist he's not making measurements and he has had a theory for a long time that when we look out in space we we use this approximation we say everything is smoothish ish. Okay. And we can use Einstein's theory of relativity as though if I have a certain amount of matter, it's kind of uniformly distributed in space. In reality, space is quite chunky. And he is saying that the mathematics of calculating Einstein's general relativity through chunky space won't be the same as calculating through the same amount of matter smoothly distributed. And I know a lot of people disagree with him. He's sort of
>> uh on an island about this. uh the they're devilishly difficult calculations to do analytically. So people have done it numerically with computers where you just kind of trace a particle and you have it go through all this and people who do that say they don't get what he gets this way. But I'm open to it. Look, I mean if if things are not fitting, you have to be open to a lot of possibilities.
>> Yeah. Yeah. The more things don't fit and the longer you're in that state, the kind of more
>> you know you say, "Oh, who's got
>> what do you got?"
>> Yeah. What do you got? What do you got? What do you got? Yeah. I mean like for example when we discovered dark energy there was uh something called the age crisis where uh there were stars that appeared to be older than the age of the universe and that was a problem and uh the solution to it was actually dark energy because when we said the age of the universe we were assuming that the expansion had been slowing down the whole time. And so when we said how long ago was everything on top of everything, we would get a young age for the universe, 10 12 billion years. Once you realize, oh no, the rate we have right now is a fast rate. That's not the average expansion rate of the universe. Now let's do the proper calculation. It pushed the universe to be older, 13, 14, 15 billion years.
>> Adam, I don't know if you're a betting man, but what would you bet would be the solution to this?
>> I wouldn't bet. And the reason is because I
>> That's not fun. I like to think of myself as part of the crew of umpires in this game, right? So, we're calling the balls and strikes. We're saying, "Oh, this thing's traveling this fast. This is so far away."
>> You can't fix the game a little bit.
>> I mean, you know, that would be the problem.
>> If you're umpire, you can say this is an unusual game. This is not
>> finger on the scale as the mafia likes to do.
>> So, I you know, my bet is that there's something interesting going on, but what it specifically is, I don't know.
>> Okay. But it's like we've got two thermometers. You're taking my temperature. One says it's dying 98.6 and the other says I'm at a boiling point and you're the doctor going it could be new physics. I don't know. I'm going to charge sick. I'm willing to go and say that you're sick.
>> You would be a terrible doctor. One of the more fascinating dimensions of the moving frontier of science is when you don't have an answer to questions that have been posed or you have data, you can't make sense out of it based on our understanding of how things should be or even could be. Then you got to scratch your head and say, do I have to give up some prior expectations? some prior assumptions that went into this understanding of the universe because the puzzle pieces don't fit until capernicus our understanding of the world the universe had earth in the center and how else do you explain planets going forward and backwards in the night sky forward and then retrograde and then forward again they have epic cycles we got that we got that explained explained. And then Capernicus comes along and says, "I got a new idea. Earth is not in the middle. That's pretty serious. The sun is in the middle and Earth is just another planet and we're all going the same direction around the sun." You say, "Okay, the math is a little simpler, but the idea doesn't sit right." The epicycle thing that kind of matched the data. And so now, what did they do? They said, "Let's check the model." So they checked the model and it turns out the planetary orbits were not as precisely predicted as they were for the epicycles. Do we throw away the whole thing because epicycles were giving better predictions than a sun-entered universe? Do we just throw it all away? Or maybe there there's adjustment on the edges of this. Maybe the idea that the sun in the middle is what's fundamental. And oh, Capernicus assumed, presumed that orbits were perfect circles. Why wouldn't they be? It's the heavens. It's where God is, and a circle is a perfect shape. But they weren't. Discovered by Johannes Kepler 50 years later, he shows that they're ellipses. You keep the sun in the middle, put the planets on elliptical orbits, you perfectly predict and understand the motions of the planets. We're in this interesting precipice in cosmology where, you know, the Big Bang is pretty secure in spite of what newspaper headlines with clickbait might have been implying over the last couple of years. Big bang in trouble. We I think it's pretty secure. If I'm betting, I'm betting we're going to have the big bang throughout this. But we're gonna have to understand something else about how we interpret the early universe, how we're understanding the expansion in the modern universe. Is there some missing piece that'll make it all come together? Missing piece of understanding that'll make the puzzle pieces of cosmology come together in a resurrection of the challenge that confronted Capernicus. We kept the sun in the middle and we found out what else needed adjustment. And at each turn of those discoveries, we had a deeper understanding of the operations of nature. And that's what makes it all so beautiful. And that is a cosmic perspective.
>> Adam, has it been a delight to have you come through town?
>> Thank you.
>> I I don't know how often you get through New York. I know there's a lot of good fertile brain activity in the Baltimore. sister lives here. Shout out to her sister.
>> Here's the excuse.
>> Shout out to her.
>> Shout out to your sister. And let that be an excuse we can exploit going forward to get you back here and catch up
>> on whatever is the latest thinking.
>> Can I have your prize? I want to show it to my son. I'll give it back to you. I promise.
>> Is he here?
>> He's under my seat.
>> Dude, thanks for
>> Absolutely. This is so fascinating. I learned a lot and honor to meet you. Seriously.
>> Yeah. Great.
>> All right. This has been Star Talk. Neil deGrasse Tyson here, your personal astrophysicist. As always, keep looking up.