Cosmology (THE UNIVERSE) Part 1 Encore with Katie Mack

Hey everyone, this is Katie Mack, your friendly neighborhood cosmologist and connoisseur of cosmic catastrophes. It's been a while since I've talked to you on Ologies, and a lot of things have been happening. Since that time, I have published a book called The End of Everything, Astrophysically Speaking, which is all about different ways the universe might end and what those would look like, and I've moved to a new place.

When I recorded this, I was just about to start a job at North Carolina State University, where I was an assistant professor of physics. And about a year ago, I moved to the perimeter institute for theoretical physics in Ontario, Canada. And there I have a really cool job title, which is the Hawking Chair in Cosmology and Science Communication.

And at the perimeter institute, I continue my research on dark matter, and I work on a number of other early universe kinds of questions, and I do a bunch of public engagement outreach things like that. I give a lot of talks, I do radio things, and I'm working on a new book, which will come out in a couple of years that's about particle physics. So this episode is an episode from 2017, The End of 2017, and a lot has happened in physics since then.

In terms of what I talked about on the episode, there's a bit of an update for the LIGO experiment. At the time, there were just a handful of detections of black holes colliding in other galaxies, which is just amazing. But now there have been something like 90 detections of black holes colliding in other galaxies. There will be some discussion in the episode about gravitational waves that we see from those.

Another thing that we talked about is supermassive black holes and what they would look like if you could see them. And in the movie Interstellar, there was a simulation of what that would look like. Since then, astronomers have actually seen that. They've actually seen the light from stuff falling into black holes and the black hole shadow that's produced when the light gets eaten by the black holes.

So there's an experiment called the Event Horizon Telescope Project, where astronomers basically linked together telescopes all over the world and created an image of a couple of supermassive black holes. So yeah, really exciting stuff. Check out those things and I hope you enjoy this little blast from the past of cosmology. Hey, welcome to Allegies. I'm your Ellie Ward, the host. Now, each week I sit down with anologist. I ask,

why do they love what they do? What is your deal? What should we know about it? And this week we cover... The whole fucking universe. Which has existed and it's expanding and you're floating in it. And you're made out of particles and matter and forces. We don't even understand. And maybe there are multiverses. And is this reality? And what are you doing here? And does anything matter? And of course it does. But should you be afraid of wearing bright lipstick or dancing in public?

Probably not. No, in the scope of things. And the scope of things is really... it's giant. It's called cosmology. Now, if you think that you listened to this episode already because you learned some stuff about beard care and facewash, think again suckers. That was cosmology. This week is cosmology. The study of the cosmos. And so when I say this episode is like everything, it's actually everything. It's the whole universe. It's a lot. It's a lot. It's so much, it's a two-parter. It's a two-fer.

So this week we'll get the nuts and bolts of what astrophysics is. And after about an hour, you will walk away cocktail party literate on goddamn astrophysics. Kind of. I don't know. I'm learning here with you. Of all the episodes I've done, this was probably the one I need the least about. So let's learn together. Shall we? Part two of this next week are your questions. Submitted via Patreon and the Allegy's podcast Facebook group. Y'all had good ones. Next week we'll address them.

Now the etymology of cosmology. Cosmos with a K is the kicky little Greek word for world or order. So cosmology is a study of planets and such. Sure. But also why and what and how? Where? What? Huh? It's a study of what? This week's cosmologist is someone I've had a faunting Twitter fascination with for a while. And I met through a group of science friends I love known to some as the nerd brigade or kind of like a gang but with a website.

But I was always kind of intimidated by her because she is in her own words in academic nomad and she continent hops while studying particle physics and black holes and gravitational waves and she hangs out with Stephen Hawking. So when I met her through friends I usually just sat at brunch like a barnacle and tried to look away when she caught me staring at her. So I asked her to be on the podcast. She said yes and I immediately

started perspiring. So she came to my apartment. We sat down and my usual hour interview stretched to almost two hence the two-parter hours before she politely reminded me that we were supposed to be meeting people for a movie and we should stop. I'm so so glad we did this podcast because I got to know her even better as a friend which y'all are gonna be cheesy

and say it's a true honor. So in this episode you'll learn about the things that make you you and the stars that exploded to make the things that make you you and the scale of our existence in space and what it feels like to be heckled by Stephen Hawking and if this is real life and if astrophysicists are just like making bullshit up that the rest of us just accept because we're like man I don't even know how to read these equations so okay so you'll get at the

very least a loose grasp on just the whole of existence and maybe steal yourself to be the biggest you you ought to be and more importantly get to know better one of the world's finest voices in cosmology you know her as astro Katie on Twitter aka astrophysicist Katie Mac

so take me back to defining some stuff because as a layman as a laywoman over here a layhuman yes I don't know the difference between a physicist and astrophysicist a particle physicist an experimentalist a cosmologist and an astronomer I don't know what those are

and I'm either gonna have to Wikipedia this or I can have you give me a run down so these things are they're a little bit like fluid these definitions uh so astronomer is basically somebody who studies space in some way and usually when

people say astronomer versus astrophysicists that usually astronomer is like more on the observational side or sort of describing stuff in space astrophysicist is more about like trying to understand how the physics of the thing in space works so you can be an astrophysicist trying to understand

how galaxies form for example and so you're applying physics to this stuff in space um if you're a particle physicist you're working on like how particle interactions work uh so like you know annum masters and things uh large hydron collider he exposed on um

usually I mean the the the like classic particle experiment is you take two particles and you smash them together and you see what comes out uh that's what the large hydron collider is doing now the LHC that's what you call the large hydron collider when you're all tight so you've maybe heard of it

you kind of know like it's a thing in Europe maybe has something to do with atoms I looked into it the large hydron collider is located near the france swissorland border and it's a circular tunnel it's over 500 feet deep in some parts and it's 17 miles around

it is the largest machine in the world so this thing consists of over 1200 magnets and they're cooled to a temperature colder than outer space and then the magnets accelerate protons to almost the speed of light and then the protons are bashed together it's very punk rock very expensive

the LHC was mostly completed in 2008 over 10,000 scientists and engineers worked on it now in photos it looked kind of like a giant well lit subway tunnel uh but with less pee and rats if you're like I can't remember what a proton is because I'm not required to anymore I'm not in school don't worry

neither did I it had to google like how does an atom work I forgot so I'll brush you up so matter is stuff and molecules are some atoms stuck together atoms are made of a nucleus which is a little cluster of neutrons and protons protons have a positive charge pro electrons

have an equal negative charge and electrons are b-bopping zoom it around whirling derbish style outside of the nucleus so the neutrons and protons which are the ones that are just cuddling in the nucleus those are made of smaller particles called quarks and the quarks come in a

couple different varieties so what gives these particles their mass what are they where do they come from we've got all these little tiny things that make up matter okay so I heard it explained that there's a field called the Higgs field

it's named after one alive and well Scotsman physicist named Peter Higgs and how a particle interacts with the Higgs field gives it its mass kind of like drag in water so Higgs bosons are particles they're an excitation of the Higgs field it's kind of like a drop of water splashing

from an ocean so the large Hadron collider smashed protons together to see if they could prove that the Higgs boson exists and guess what bitches it does you're not bitches some people call this the god particle because it's so fundamental

to all matter in the universe does Dr. Higgs like this name no he's an atheist he thinks it sucks and the guy who coined it the god particle actually wanted to call the god damn particle but as publisher made him change it in a book so the large Hadron collider one of the things it does

smashes these protons together into smaller things to figure out why matter has mass there you go also the large Hadron collider accidentally has its names spelled wrong on its own website as large Hadron collider once would be mortifying but like what if they did it more than

once like twice or five times that's impossible is it because a search on their site revealed they'd spelled it large Hadron collider 165 times thank god particle for that that's just precious so whenever you're like I don't understand this stuff maybe I'm not smart enough just think

someone typed in large Hadron collider over 150 times and they built the thing so how else do people figure this out about very important things that we can't see but there are other ways to do particle physics measuring how particles interact with each other

throwing particles at other things accelerating stuff and seeing what happens all of that kind of stuff on the experimental side and on the theory side it's a lot about trying to understand like the fundamental forces of nature so like how how atoms hold together how you know

particles can change in other particles in certain conditions how gravity fits into all that which it doesn't at the moment theoretically okay it doesn't it's it's very hard to get gravity and particle physics to work together this is kind of yeah it's it's sort of

this may be another topic but like this is the the reason string theory was invented real quick what a string theory well in a very corksized tiny nutshell the premise of string theory is that basic objects are not point like but they're string like

so a quark might be made of a loop that kind of vibrates and moves around every kind of particle is like a different wiggly string so why does anyone care why are people so horny for string theory well number one it's from the 80s and maybe this is like the scrunchy of particle physics I don't know more importantly string theory is a theory that works with both Einstein's general relativity

and that mr. Einstein posed that what we perceive as the force of gravity is is the curvature of space and time more on that in a minute and quantum mechanics which is the physics of the tiniest building blocks that exist so remember those quarks that made up protons and neutrons what are those

made of maybe these string like loops of matter every time I hear string theory mentioned I think of string cheese I cannot and I was writing and researching this episode and my I found myself on a website like 2.30 in the morning learning that string cheese as we know it was invented in

Wisconsin in 1976 and the way they get it to string is to heat it to 140 degrees Fahrenheit and that aligns all the milk proteins also the first iterations of string cheese or bigger and chunkier and served to drunks and bars should we get back to physics okay I'm sorry and this is

like the big question in physics is that like so there there are a few sort of fundamental forces of nature right there's electromagnetism there's that and that's like light and you know like static cling and and all of those kinds of things right and and magnetism

and then there's the weak nuclear force which has to do with like how particles decay in radioactivity that kind of thing and how particles can change into other particles under certain conditions there's the strong nuclear force and that holds particles together in the centers of

atoms okay and those all kind of make sense together theoretically like you can write down equations that make those all fit in some way more or less when Katie says you can write down equations that make those all fit I appreciate her being inclusive with this second person

but I I cannot write down equations to make those all fit in some way I cannot do that but then there's gravity and gravity just doesn't follow any the same rules it's like it's very hard to put together a theory that includes those the fundamental forces of particle physics and

gravity so like so it's gravity like the bad boy in a teen drama it's just like it's just not following any rules it's weird it's like like gravity is all about space time you know so gravity like so the theory of gravity that we have is Einstein's theory of relativity so general relativity this is the theory of gravity where okay get ready here's Einstein here's how the universe of which you're a part works the the basic picture is that you can think of space as this malleable thing and if

you have something that has mass it creates like a dent in space it sort of bends space around it okay and and so other things moving past will respond to that and like fall into that dent and that's like how gravitational attraction works you can think of it in this geometric way okay and it works

really well like geometrically to think of it like that but then there are fundamental principles that happen in that like the speed of light as a limiting factor and all sorts of things like that so only certain paths things can follow and

and everything but then the particle physics stuff like all the equations of particle physics are done without thinking about gravity because on those scales like gravity is it important it's a really really weak force okay um but also like there are the way that

the particle physics is formulated in the standard model of particle physics which is what we use to talk about all these interactions um it doesn't have the same like it doesn't follow the same rules as gravity like there are ways in which the whole like speed of light

thing is violated in one way that you can formulate how particles move around um which is kind of like there's kind of like there's this way of formulating it where a particle going from point eight to point B passes through every possible path on the way between point A and point B and

it's only by by using that idea that you get the right answer for how that particle is moving in the particle physics point of view and that doesn't work with relativity um so there are a couple of things like that where like quantum mechanics and relativity just do not like each other

really and and it gets especially problematic when you get to black hole because a black hole is this very like intense gravitational system it's basically a dent in spacetime that's so deep that like everything falls into it if it gets close enough um but at the edge of a black hole they

have an horizon you have this weird quantum mechanical thing happening where you can have like particles evaporating off of it and that sets like a sort of scale of the black hole and that means there's quantum mechanics happening in a strong gravitational system and then just everything breaks

it just goes totally haywire because um if you look at it from a gravitational point of view like a relativity point of view you should see nothing at all interesting happening when you when you fall into the black hole like aside from like you're you're killed by the gravity but like you don't see

like nothing weird happens when you pass the horizon but from a particle physics point of view like there there might be like this like firewall like there might be like a sort of like boundary of intense radiation there because of the way you have to think about how the particle physics

works this is a complicated story but um but basically there's like astrophysics typically is yeah I'm not explaining it very well um but but basically like like basically when you get to that point when you have a black hole it has an evaporation happening where particles are coming off the edge

of the event horizon um one way of looking at it says that that that means that whatever you fall through into the black hole you can't ever find out what it was that information is destroyed but quantum mechanics so like the particle point of view says you can't do that and so there has to be some kind of loophole and then gravity doesn't like that and you just you just end up with chaos and so there's this there's this um big problem called the black hole uh information paradox which has

been around forever and every once in a while somebody's like oh I solved it and then it's really complicated and people don't really understand how that works has anyone actually solved that I mean I so technically I'm just not qualified to know that for sure because it requires understanding

quantum gravity in a way that I do not um but there have been some solutions suggested but in in general there's still a lot of discussion um so I don't know okay wait so what does a cosmologist do the cosmologist just means you study the universe as a whole right so you study maybe the beginning

of the universe the end of the universe how it changes over time um but you can be a physicist cosmologist or an astronomer cosmologist and those are different um and and it's culturally different like but the so if you're if you're a physicist if you if you hang out with particle

physics people and you say you're a cosmologist then then the implication is that you work on like the the beginning of the universe and the forces of nature and um maybe the end of the universe something like that hanging out with astrophysicists and you say you're a cosmologist then you just

study things that are really far away or you study you know um some something you know more fundamental but like you can be a cosmologist in astrophysics and you're a cosmologist because you study very very distant galaxies the reason that counts as cosmology is because that means you're studying the very distant past of the universe so there are different flavors of cosmology but they're all kind of linked at least in my opinion by like oh where are we what are we what are we what do we made of

a k a it's a branch of astronomy that involves the origin and evolution of the universe that's a less panicky way to put it and so so that so then you're studying like how the universe has changed over time so there are kind of different ways of doing it and I've done all of those

different kinds of cosmology I guess um because I've spent my time kind of bouncing back and forth between the particle physics and the astrophysics communities so I've worked on you know the the big bang and like theories of the early universe and I've worked on distant galaxies and how galaxies

form and I've worked on black holes and weird stuff like cosmic strings and just all sorts of things what is a cosmic string a cosmic string is kind of like a uh a sort of line or wiggly line of energy that stretches across the cosmos might not exist probably doesn't exist but there could be

this like whole network of strings of like it's it's it's it's kind of like if you think of like a black hole but you like stretch it out across the whole universe you get it's kind of like that um what does it do what it so really interesting things so if you have two cosmic strings and they

cross each other um they collide they can like reconnect in a different way so you can have two cosmic strings that are about to collide and then they they like change so that now you have two sort of loops of cosmic strings they're going in opposite directions like so they sort of pass

through each other by branching off in this weird way so cosmic strings may or may not exist now if they do exist some theorists have used them to maybe sketch out some stuff about time travel please forget that out please fix some stuff thank you and you can make a loop of cosmic string

and then that loop of cosmic string will like wiggle around and make gravitational radiation and um and uh disappear into nothingness and if you have a cosmic string like if you have a cosmic string between you and some distant galaxy um then you might see two pictures of that galaxy

because it like splits the space kind of what it's really cool um now how much do you think about all of this in your day-to-day life and like when you're deciding if you should upgrade your rental car and like if you should cut bangs and what happens to your molecules after you die like how much

do you let this kind of get to your own existence uh yeah somebody asked me that the other day like how much do I like get sort of just overwhelmed by these ideas or whatever um it's not very often like most of the time this is like this is fun stuff to work on but like most of this time it

it feels more like some kind of combination of science fiction and a fun puzzle you know um so like I'm trying to solve a problem I'm trying to calculate something uh and trying to come up with a new idea for how to do something and so it's like a puzzle it's like some kind of neat thing to work out

and I don't think of it as connecting to my own life or existence because it's way far away or way in the past or you know probably doesn't exist or whatever right um but then every once in a while like I'll be I'll be thinking about this stuff and I'll be like oh my god like there's like I'll be thinking about black holes or gravitational waves or like the inflation period in the early universe or something like that and I'll be like I'll have to like hold on to something and be like oh

god because these are huge like mind-bendingly intense forces and massive things and like the kinds of energies and the kinds of like force and and just I don't know the explosions and everything it's just we cannot comprehend this stuff I mean the earth is is really tiny and really

unimportant like in a big way so so okay you know there's there's this there's this famous photograph uh the pale blue dot yes uh yeah so this is a picture that was taken by the Voyager spacecraft so the pale blue dot photo was taken on Valentine's Day in 1990 as Voyager 1 was leaving

the solar system it was like bye bye I'm out and astronomer Carl Sagan said yo let's turn that lens around let's take a pic of all of us far away what do you say might as well and it was 3.7 billion miles away it's little galaxy's longest range selfie this photo itself it looks like you

accidentally took like a blurry image of a few Christmas lights and there was like a speck of dust on your lens those lights are just a few scattered rays of sun and someone would have to point out that that dust is our planet is such a tiny speck and I'll let Carl Sagan

put this in context he's the pro here that's here that's home that's us on it everyone you love everyone you know everyone you ever heard of every human being whoever was lived out their lives the aggregate or joy and suffering thousands of confident religions ideologies and economic

doctrines every hunter and forager every hero and coward every creator and destroyer of civilization every king and peasant every young couple and love every mother and father hopeful child inventor and its plurr every teacher of morals every corrupt politician every superstar

every supreme leader every saint and sinner in the history of our species lived there on a mode of dust suspended in a sun beam the earth is a very small stage in a vast cosmic arena sometimes when I give talks about cosmology I'll end with this picture and I'll be like

you know just thinking about how vast the universe is and how really insignificant we are and it's and the insignificant it's is even deeper than just what you see from that picture because in that picture you see like there's a whole lot empty space and then there's a little tiny rock

and we're on that little tiny rock right oh boy and there's a lot of space but it's even worse than that because because like not only are we not the center of like the universe or galaxy or a solace or anything like that the matter that we're made of is also really unimportant because because like

just the kind of stuff that we are and that we can understand and interact with regular matter is like five percent of the universe so most of the universe is something called dark energy that we really don't understand but it's some sort of mysterious stuff that's making the universe expand

faster and faster and it's going to take over eventually and then there's dark matter which is some kind of invisible matter that is most of what the galaxy is made of and most of what all galaxies are made of so like our galaxy you know we think of it as like this pretty disc of

stars but it's actually embedded in this invisible blob of extra stuff that we can't see and that blob is way bigger than the stuff that we can actually see so dark matter is like 85% of the matter in the universe or something like that oh my god and then dark energy is like 70% of all of the

stuff in the universe like so so then we're this like little tiny five percent size and that's just the kind of matter that we can understand that we can do experiments on that we can see or touch or interact with in any reasonable way and then it's like not only not only are we like a

tiny speck of dust on a tiny speck of dust like it was you know like we are so insignificant like the universe doesn't even it doesn't even matter that were like that are kind of stuff is there you know the best thing about this conversation is yeah I'm I'm having a with a cosmologist

and like an astrophysicist but I could also be having the same conversation with any of my college roommates who had like a seven foot bong in the in the garage when astrophysicists and cosmologists get together yeah is it just kind of like a round robin of like stoner existentialism like

because they're feeling there's such a fine line like and then you're either incredibly incredibly smart and thoughtful and knowledgeable about this stuff or you're just like you've just numbed yourself enough for you allow yourself to think about it and then it's like the bell

carb this is big wide swath of people who are like I can't even think about it it's too much you know I mean so when when I do get together with other cosmologists and we talk shop it's usually very very technical and so we don't get into this stuff at all like where it's it's usually you know

we're just talking about we're talking in in a lot of jargon about like some measurement or something and we're throwing out numbers and we're trying to like figure out like is this a reasonable measurement to make or whatever like what what kind of plot can we make to to you know

to illustrate this point or what kind of calculation should we do or like what's the important variable it it would not be interesting to somebody who is not in the field um so it's really only when I'm talking about people are not in cosmology where like I have these moments of like oh god

you know um but the thing I mean it's it's a little bit dangerous to talk about that stuff though because then sometimes people get the idea that we really are just gotta sit around making stuff up you know like and so then people think like oh I can be a cosmologist like what if the universe

is shaped like a football you know right and I think that the the the sort of disconnect there is that like the ideas themselves if they're not backed up by the data or by like a very rigorous model are really not that important um like once we have data and we have some kind of

unifying theory that says that this is probably the way things are then it's like super cool right um but if somebody had said like oh you know maybe the universe is like this like we don't really know what to do with that and it does it's not really helpful until like yeah yeah exactly like

like you have to it has to be connected to something we can test or or or write down mathematically or else it just it it's kind of not helpful which is you know it's a bummer but but once you do have the sort of mathematical tools and stuff and you can speak that language you know um then you

can get really creative and then you can just do really fun things um so like I have a I have a project I'm working on that has to do with um have a few interesting projects actually um so I have one so here's one that that that could be fun so okay has to do with black holes and

galaxies and the bending of space okay so um so every time there's a massive object it bends space around it and so that means that light when it goes past bends around so like a lens like the massive object acts like a lens for light and so light gets bent around so there's this way

to study like what galaxies are made of by having a very bright light behind the galaxy like really far away and looking at how that light like bends around inside that galaxy and like how the light fluctuates as things move and stuff like that and uh that's called gravitational microlensing in

this case the kind of thing I'm working on but the details aren't important but it's it's um it's this thing where like the thing that's making the bright light is also a black hole because it turns out when you have a super massive black hole like billions of times as massive as

the sun um those things can be pulling matter into themselves and that matter lights up like a whirlpool of of stuff what and it can make this incredibly bright light that you can see like across the universe and so so we use that as like a backlight to study the stuff in a more nearby galaxy

to find out how many black holes there are in that galaxy so black holes make light sometimes it's supposed to be confusing yeah it's like I think I mean I think it's like it's one of these things it's like the biggest misconception about black holes is that they're dark usually they're not

like the ones we know about are usually not dark and it's it's yeah it's because they're not it's it's because like technically the black hole itself can't be seen but it's doing so much that it like affects everything around it and so usually you can see black holes because they're like

really destructive and like the stuff is falling into them kind of like if you um if you had a drain at the bottom of a bathtub uh-huh um like you might not be able to see the drain through like the you know bubbles or something but you can see that there's like a whirlpool

of stuff falling in at that point oh man and that's how we see black holes in space usually is we see that they're they're pulling in a lot of matter and so they lie that matter lights up and so once it goes into the black hole we can't see it but it spends a lot of time whirling around really fast

it's like an intergalactic uh garbage disposal yeah yeah yeah and it can be it's some of the brightest things in the universe are are black holes we call them quasars when they're when they're the supermassive ones and they're pulling matter in um like that and and we have so so that's like

um those are for black holes that are like millions or billions of times as massive as the sun and how far away are those puppies all right well um okay supermassive black holes the one the ones I was just talking about millions or billions of times the mass of the sun um those

seem to exist at the centers of pretty much every reasonably sized galaxy we know about at the centers yes so including ours yes really yes so our galaxy okay quick note let's do a few cosmological basics our galaxy is Milky Way right and this next analogy I got right off of NASA's

night sky website which I think is for children but it's so helpful so okay imagine our sun it's one star among hundreds of billions of stars in our Milky Way right so if we shrink the sun down to smaller than a grain of sand our little solar system Venus Mercury Earth all of those would be

small enough to fit the whole solar system in the palm of your hand now on that scale with our solar system in your hand the Milky Way galaxy would be the size of North America and the Milky Way's big but our next our neighbor and drama the galaxy it's about twice as big as the Milky Way

scale is important here I suppose but at the center of our galaxy there's a black hole so the Milky Way is like a disk of stars and gas and dust and stuff and we're sort of out toward an edge and um at the center there's a bulge of stars and gas and dust and then at the middle of that

there's a black hole it's four million times as massive as the sun I didn't know that do we have a name for it yeah yeah we have a name for what we call it Sagittarius A star okay which is a silly name it's because it's a kind of I think it was like um I think a radio source and because

it was pulling in some matter and so it was lighting up in the radio a little bit and so ours is not pulling in very much matter at all okay very occasionally it'll eat a little blob of gas and the astronomers get super excited um but like there's very little happening with it but it does

it is really big and it's got a bunch of stars orbiting really closely around it and so you can actually go online and see like data um follow like tracing out the paths of some of these stars and you can see them like whip around as they go really close to the black hole in their orbit so

some of them have these orbits that they're really far away and then they come and really close and they go boom like that right around the black hole and so you can figure out exactly like how big it is and where it is by watching these stars go around it really quickly so I did a little looking

and if you google European Southern Observatory and S is in SAM 2 you'll find this oh my god like a rimshot nabaskable game like yeah yeah yeah like that except it comes back around you know that's on the orbit so yeah so there's stuff orbiting really close to that black hole that one is

like well let's see it's 8,000 parsecs away I don't know how much that is in light years a parsec is about three something light years so light years how far how far take how far light travels in a year right so light moves very quickly so that's a very long way so for example

light travels uh it takes light eight minutes to get between the sun and us um there's a rule of thumb actually if you want to know how far how fast light speed is it goes about a foot per nanosecond a foot per nanosecond yes oh that's easy to calculate yeah just upon just zero right yeah

just put a zero on it yeah yeah yeah it's easy and now but it's kind of cool because then you can like you can say like if somebody is like 10 feet away from you they are 10 nanoseconds in the past they're 10 nanoseconds in the past yeah oh man I'm gonna trip out I'm just

can't move the film like we're like three nanoseconds apart right now that's so weird it's so weird it's great though and I I learned this recently and I've already forgotten it which is embarrassing the distance between us and the sun is a certain what is the you oh that's um

astronomical unit astronomical unit yeah okay this is a distance between us and the sun I just learned that and then completely forgot it all in this fan of a couple of weeks that's okay no reason to know that stuff I want to know a little bit more about when you were a kid by the time Katie was about 10 years old she was inspired to pursue some form of cosmology and she was already a fan of British cosmologist and theoretical physicist Stephen Hawking she was already hip to him she's

like I know the student now if you need a quick brush up on him as a person after this podcast watch the 2014 Eddie Redmain film The Theory of Everything or you can just watch the trailer start crying like somebody you know now if thinking about living on a dust moat floating in a sun beam

wasn't inspiration to do what you want to do in life consider a human who's figuring out the mysteries of the cosmos doing computations and cracking theories about which I can't even comprehend the first paragraph of the Wikipedia page also while living with ALS Katie is one of

several billion people inspired by Stephen Hawking what was it that Stephen Hawking did or or what did you how did you become aware of him and how did you kind of absorb what he did I'm not sure how I became aware of him I think that you know he was on TV every once in a while and I had a brief

history of time the book and I read that and I just like I don't know like I was interested in black holes and I was interested in like the Big Bang the Big Bang Theory being that the universe began those 13 odd billion years ago with high temperatures and high density it's continued to

expand also note if you google Big Bang Theory all roads lead to Sheldon so just becash call it Big Bang as far as Wikipedia is concerned and so I would read about that stuff and Stephen Hawking was a big figure in those those areas and he was he was doing a lot of science communication and

he would he would visit Caltech every once in a while and I was growing up in LA and sort of long beach and so I would sometimes like my mom would take me to see talks by my physicist because I was super excited about these things and so I remember seeing talk by him I remember seeing

I've talked by Paul Davies and like you know just prominent theorists would give talks sometimes and somehow my mom would find out about them and take me along and because she's she's really into science and science fiction and physics and everything so have you gotten to meet have you

gotten to meet Stephen Hawking yeah yeah so when I was at Cambridge so I spent a year at Cambridge during grad school just kind of visiting and working with people on some research and I was mostly based in his department and my office was like directly below his yeah and we were in the

same like research group basically I mean like we didn't talk like we weren't I wasn't in his research group but we're in the same is the center for the article cosmology and like we're both based there so there were you know half a dozen professors we were involved with that he was one

of them and I was a grad student visiting and so I would go to all these like you know meetings and the coffee and stuff and shortly after I was shortly after I started being a visitor there somebody asked me to do one of the like lunch seminars so basically if you're a physicist and you're visiting

another department you're kind of obligated to give a talk that's kind of how it works so they say hey can you give a talk she's like yeah I'll give a talk for the Thursday lunch seminar so she does it and it turns out that it was the lunch seminar that like Hawking goes to I'm getting ready

to give the talk and I see like several of my professors in the audience like looking expectantly at me and I'm like this when I'm like freaking out but he but he he wasn't there Hawking wasn't there so I was like it's fine it's fine and I'm getting ready to give the talk and then I hear this

like beep beep beep oh my god my stomach is cramping just hearing this and he shows up oh get so much worse oh god um so I told this story before but it's it's still it's still like is it makes me like sweat so so I was I was getting ready to give the talk and so I start the talk like I put up

the title side and I was the tie the topic was Promodial Black holes which is a concept that Hawking came up with along with some other people and pressure yeah um and as I'm starting like as I after I introduced the title and stuff um I hear this this voice say thank you and it was his voice

and I was like and everybody kind of laughed you know and I thought maybe he was like thanking me for talking about the thing that he invented you know but I don't know and you can't ask him to elaborate because he his speech is very like slow so he uses this machine thing and it

just it's very slow um it tracks his eye movements uh yeah okay well no not exactly it tracks there's a little sensor that looks at his cheek okay and so he kind of winks and that like selects words on this like list and it takes a couple minutes per word sometimes right so you weren't like

I couldn't be like yeah yeah so I had so so I just kept going and then eventually like I heard it again yes or later on no or I don't know or just random things as I'm going and every time like I'd look at him and I'd be like you know but he would just kind of look blankly at me and the person

who was like taking care of him is a lunch seminar so the person who was taking care of him was like feeding him and she just kind of looked blankly at me and like I had no idea it was going on and so I would just kind of pause and then continue I guess like what am I gonna do with the heck

we knew what was happening here I had no idea and I was so nervous and like all the professors were there and and already one of the other professors had been like asking a whole bunch and a really tough questions on like the second slide so I was already like freaked out just imagine

being in this situation it's a nightmare it's like the best nightmare ever but like I answered the questions and he seemed to be okay with it so I finished the talk and Hawking left and he hadn't asked any questions and I asked one of the seminar organizers like what what was that and he was like

oh well when he eats the machine oh my god oh my god oh my god it's chewing and it just picks random stuff from like the quick select menu oh so and nothing to do with me at all it was just like it was just like here's the you know here's the most common phrase yes no maybe I don't know I don't think so oh my god this is like the worst deodorant ever like this is the most stressful situation you could possibly ever be oh my god and like they could have told me yeah they could have

given you all heads up every time oh my god they just did like they just didn't mention it any word on whether or not he liked your talk I have no idea oh my god you ever tell him that you went into cosmology because of him um I I don't well so the first time I met him when I was

16 oh just my 14 14 baby baby I did tell him then that I was a big fan so Hawking was at Caltech and Candy got her mom to drive her and a friend there to hear him speak and afterward they were walking the same way that he was going when they were leaving and she was too nervous to say hi

my friend went up to him and said my friend would like to speak to you she had a wing man so I went up and said that I was a big fan and I enjoyed his work and I thanked him and he said thank you very much oh now what happens to you when you get that because you're really

I mean I'm not gonna fan girl right here I'll do it in the intro but you're like a very big voice and science communication you're like you're a very well-known astrophysicist cosmologist what what how do you feel when people come up to you and say I was inspired to study this or you've

changed my course like what kind of reactions do you get it's I mean it doesn't so it's not I'm not like Stephen Hawking like I'm not that level of famous and I'm not that level of like important in physics and stuff and and you know so it's it's kind of a different thing but I do you know

sometimes people do like tell me that they like a so one of the messages I've gotten a couple of times is a like a teenage girl will say that she didn't think she could do astrophysics but she really loved it and then she saw what I was saying on Twitter or something or she saw me speak

and then she decided she was gonna go for it wow so I do get that sometimes and I like my feelings don't know what to do with that but it's really it's really sweet and throw them in a black hole and you're feeling here I mean it is really sweet it's really like rewarding when that happens and

and it it makes me feel like maybe like the stuff is maybe the stuff I'm doing is is worthwhile when people say stuff like that or like a little kid will sometimes say that they want to be an astrophysicist or something and they'll be really excited to meet me like I was I was in Raleigh

a couple weeks ago and I was I was sitting in a cafe and I was wearing my NASA jacket with a little NASA badge on it that I got it JPL JPL by the way is NASA's jet propulsion laboratory and it's nestled in the golden hills of Pasadena California and it's responsible for things like

rovers on Mars and according to press materials JPL's function is to engineer and fabricate cool ass shit that's like so dope that's very bold NASA I also do not fact check that part it is not true and this little girl came up to me and she was probably like eight or something and she asked

me if I work for NASA and I said I don't work for NASA but I am an astrophysicist and and so we'd like talk a little bit and she said that she really is into space and stuff and I was like well I'm giving a talk at the museum in a couple days you can come and hear my talk and so she and

her mom came to my talk and she asked a question and it was just really sweet and I was like oh what was your question um I think her I think her question was about like what's inside a black hole which is a good question you're like a bunch of space garbage well yeah so it's I mean it's

not a straightforward answer really because once stuff goes inside the black hole it has to go straight to the singularity and I can't do anything else and so then it does it really exist to that point like that's kind of subtle but anyway it's a good question and apparently like she

was talking about the talk later on and I was like oh yay I inspired somebody she's gonna be in your department later and give a talk while you're lunch baby um she's playing the singularity oh yeah so singularity is so it comes up in the context of the big bang and in the context of a black hole

a singularity is like a point of infinite density okay um usually in physics when you have a singularity I mean it's singularity basically means it's a point where something infinite happens okay where things diverge in some way um and usually when that happens in physics it means

you've done something wrong okay and it's a sign that the theory is broken and you just can't deal with that because there's none of the another theory like really works at a point of infinite anything okay um in the black hole like the way that black holes are defined and the way that we

understand how the gravity works there really should be a singularity at the center of the black hole and everything has to move toward it so so the you know the black hole has this is this thing that like the way you make a black hole you know get back up yeah no back up because they're like where

they come from what's the deal yeah so the way you make a black hole is you take a really massive star and you wait a while million spheres and the star will explode and the core of the star will collapse on itself and if it's massive enough then um I mean the reason that the star didn't collapse before is because it had nuclear burning happening it was kind of keeping it puffed up okay right um and

so you had this energy source that's sort of pushing against it kind of like if you have like a balloon in the air inside is pushing the the um plastic the rubber out right um when the star explodes there's nothing to keep it from collapsing under its own gravity um the the you know you you get to

a point where there's you can't do any more nuclear fusion so nuclear fusion is when atoms join to become a different kind of atom and they give off energy in the process like two hydrogens becoming a helium and giving off energy now this happens with atoms up to the size of iron

at which point that fusion starts to take energy you can't get any more energy out of those processes because you've gotten to a point where you've just the whole center of the star is is iron basically and it can't go farther than that and so then you have this like huge chunk of iron

that's not being held up by anything and so it starts to collapse under its own gravity like that stuff just falls in and it has to go toward the center and it has to keep going toward the center and it can't go any other direction and so you end up with the singularity this point of infinite

density technically um what is the shape like is it like an ice cream cone that has an infinite tail or what what is it I mean you can visualize it that way if you think about it in terms of like a 2D analog like usually when we think of space time like the pictures are always like a big

rubber rubber sheet the rubber sheet visual is so helpful for comprehending space time um but also when I think of rubber sheets usually the situation is not comfortable it's either like an awkward green school summer party explanation or some suburban dungeon kink that sounds

exasperating at best but for space rubber sheets thumbs up and you have this big rubber sheet and you put a bowling ball in one spot and that bends around and so then when you take your tennis ball and you try and roll it past the bowling ball it makes a little orbit and falls in right

ah this is the usual visualization for space time um but that doesn't have the right number of dimensions because space space is three-dimensional and then you can think of time as another dimension but that's kind of separate thing I am curious about time is a fourth dimension okay we can talk

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a ton of money to them so thanks for listening and thanks sponsors okay I'm sorry I have so many questions but anyway so if space is three-dimensional then the way gravity like works on it is that it kind of like pulls space inward toward itself so like a massive thing kind of pulls space

inward toward itself so in the context of a black hole it would be like a place where space gets really scrunched up right but it's easier to think about it in the two-dimensional case so it would be like you have your rubber sheet and you pinch a piece of that rubber sheet and you just pull it

down and you just keep pulling it down and it just goes to a point and it's like you know forever and it gets deeper and narrower or whatever right so you can think about it like that but then you think about like a three-dimensional analog and your brain kind of breaks and it's right but yeah

so it's basically a place where space is really super curved okay really super bent inward and so there's a point so if you think again about the 2D kind of thing the rubber sheet you can you can still move past like if you if you have your like little hole that you've

pulled down on your rubber sheet you can still take your tennis ball and roll it past that and it'll keep going but if it gets too close it'll fall in and there's nothing you can do about it and it'll always go toward the the deepest point and so that's like there's this horizon this distance

from this from that singularity where if you get closer than that you will fall in no matter what and you will just keep going and you can't ever escape and light itself will fall into because light follows the curve of space and so if space is curved enough then light will just follow that

curve all the way down oh man so once you know so you throw a flashlight into a black hole like that light never comes out again it just keeps it goes that that light beam no matter which direction the flashlight is facing the light beam will bend toward the center and what is that danger zone

called the event horizon okay that is the event horizon yeah that's the event horizon I mean you should probably stay farther than the event in general because other bad things can happen to you if you get close to the black hole if you listen to allergies episode one volcanology and thought

jumping into a volcano was intense like hang on to your butts right now I mean so for one thing the most of the most of the ones that we've seen directly with light are pulling in matter right yeah and so that means that there's a lot of hot stuff falling into the black hole in a form of a

disc and so that'll radiate you to death yes if you get too close and then if you if you get close if it's a small enough black hole then when you get close the tidal forces will kill you so tidal force is where you have like it's where you have more more grab the gravity is pulling stronger on

part of you than another part oh no like if like if you imagine you know you're falling fate the feet first toward a black hole the gravity goes the strength of the gravity goes up so steeply because it's such a compact steep thing uh-huh then your feet will be pulled on much more tightly than your head and you'll be stretched out and it's there's a word for it it's called spaghettification no it's actually called that yeah yeah so so you have to want out for spaghettification

if you get too close to black hole who the hell made that I don't know I don't know I mean Hawking uses it I don't it maybe he came up with it I'm not really sure oh my god of all of the things to call it yeah of all the things like turns you to spaghettie I don't know like that's

just what else are you gonna call it like oh my god it's tidal disruption but I love it now the most yeah spaghettification was indeed coined by Hawking in his book a brief history of time and if you happen to google image search this you will find a bounty of Photoshopped images of

astronauts being tapered into space noodles by cosmic forces I'm so impressed by this astrophysical whimsy yeah there are a lot of there are a lot of really silly names in in astronomy who gets to name this stuff uh whoever comes up with it I mean people who come up with a name it but like sometimes

the community names it like the big bang that that was the joke like that was the word was a joke the term the big bang like somebody came up with the idea that you know the universe started small and has been expanding um and somebody was like oh the big bang and that that stuck no it was

a throwaway yeah it was like it was mocking did that person get pissed at it stuck uh I'm not sure okay so English astronomer Fred Hoyle coined the term big bang it was during a radio broadcast in the late 1940s and it was kind of on accident now the story is he's so bent that it stuck but

apparently he denies that so drama in terms of what in terms of what your output is you're you're a professor you give talks you travel over the world like what is your big goal as a cosmologist like do you want to write an encyclopedia about cosmology like what's your what's your endgame

so what about my goal uh I mean I want to figure stuff out but I don't have like there's not like one thing where it's like I must solve this problem I kind of like uh just working on whatever fun stuff comes up which is not what you're supposed to do but it's what you like it's always what I

like I mean so the big thing I'm working on right now has to do with dark matter so dark matter is this invisible stuff you know um and it's possible that dark matter has this weird property where if you take a dark matter particle and another dark matter particle and you you like collide them

into each other in just the right way they'll annihilate and create other kinds of particles what so that's a possibility um and if that's the case if that's a thing that happens then it can mess with how the first stars and galaxies form because those form in these like blobs of dark matter

and the formation of those is kind of delicate um because you have to get the right balance of the gravity and the gas and all this stuff so if dark matter is going and like annihilating all the time then that sort of messes with that balance huh and so it can change the way the first stars and

galaxies form and then we can look for evidence of that with telescopes so this is the kind of problem that I like where you have like a sort of fundamental particle physics problem and then you try and figure out how to look for it with telescopes so what is your working vault do you have like a mole skin that's just filled with like gobbledy gook equations or are you working on a computer with data sets like where when you're like when you get down to work yeah what does that look like so I do

have my mole skin with the full of equations over there um I brought it with me uh so I have that um I also have a whole bunch of code that I've written to try to solve some of these equations that are in the mole skin I mean so the so the usual thing is like okay you talk to people

who work on similar things and you try and come up with like what is it what is it how can we answer this question or what is a question we can answer with this observation or like what would be a cool thing that might happen that we could find out if it does happen so then physicists talk to

each other and write stuff down and look at papers and write down more equations and I was kind of surprised to realize how collaborative this could be I always imagine physicists needed to be like sequestered in a well-appointed lab or a classy den to just think clearly but no there's

like a lot of chatting happening and then um once you figure out like what equations you need to solve and what things you need to calculate then you then you go to the computer and you write code um to calculate those things and to put out numbers and draw graphs and then you see if you have the

thing interesting or not if it all kind of clicks yeah yeah and you see if like you know does this tell us that this is going to be an interesting technique to test the theory or not and then depending on you know because this is all theoretical work sometimes um sometimes you find well

this is just really uninteresting and nobody's gonna care so I'm not gonna write it up um sometimes you're like well you know it turns out you can't measure this thing with this technique but we should write that down anyway because people might have tried otherwise and then sometimes it's like

oh we we can measure this thing with this thing and that would that'll be a really interesting result and we'll get a better answer than anybody's gotten before so we're gonna write it up and be really happy about it and then you go toward writing it up and publishing it yeah yeah and then

then you write the paper and then you publish the paper and then you know or you send it to the journal and the journals the editors or the referees are like yeah you should do this differently and so you do that differently and then eventually it gets published what is the craziest paper that

you've ever had published when the title of the craziest paper because just looking at paper titles is yeah so funny to me because they're so specific and wonderful I mean I guess it depends on what you mean I wrote a paper um called known unknowns of dark matter annihilation over cosmic time

that sounds like the best like Norwegian middle album ever it was like well yeah so that was all about like what we know we don't know about this problem um I've calculated a bunch of stuff um um I've I had some papers about like axions and and those are theoretical particles that are

super cool um is there an upper limit to how many words your paper title can be yeah you don't want to I mean you kind of wanted to be punchy right like like the whole known unknowns thing is I wanted it to be like I catching right um it's good marketing yeah yeah so so you got to think

about marketing to some degree um and you don't want it to be a long title because people are going to be skimming it this part is crazy it's like trying to buy Beyonce tickets so the way that people find papers to read is every day every weekday the website it's arxiv.org there's

like a hundred new papers about astronomy and physics and math and stuff so so the way that people find papers to read is every day every single day every weekday um the archive website it's arxiv is how it's spelled but we call it the archive the archive website um displays like

a hundred papers new papers about astronomy um and there's just a list and the titles this are those the titles and the authors and maybe like the abstract depending on how you read the archive and if you're a responsible astronomer um then every morning you wake up and you read the archive

and you skim the papers and the and the abstracts and you see which ones are relevant to your work and then you you know open those and read you know skim those papers and find out if like they tell you something interesting you get information this is how you keep up with the field

that's so much work it's so much work it's like a lot of work and if you're somebody who maybe does you know particle theory stuff as well then there's a whole other archive for like particle theory and then particle phenomenology which is more like the phenomenology is like where you try and figure

out what you would see in this in the universe that's closer to what I do so then if I if you're trying to read particle theory and phenomenology and astronomy you can get like 150 papers or something every day it's a black hole it's just it's impossible to give up oh my god but anyway so because of that you want your paper title to be punchy and eye catching but the other thing so there's a this is like so totally inside baseball but there's there's this ridiculous thing that happens so the

order of the papers as they appear on the website is determined just by what time they were sent in and after not too long these are literal geniuses they were like duh there's a cutoff time of like 4 p.m. and sometimes on I don't remember which one where if you get your paper in as close as

possible after that time it will appear at the top of the archive and so there's this if you can people have written papers about like the spike in submission times or like everybody's trying to get like four you know a clock zero zero one second like they all want to get it like exactly

at that moment so that their paper will be on the top of the list because a lot of people you know like they open the archive and then they just get like exhausted by the time they've gone through five papers and so they don't get to the end of the list and so there's this ridiculous like

this ridiculous ritual of when you're when you submit your paper to the archive you're trying like you watch the clock and you try and hit the submit button at exactly the right moment that makes me so anxious it's like when someone people comment first on youtube video it should be randomized

because it's also like it's also been shown that it does matter in terms of like citations that's not right it's not right oh my god yeah um oh wait what was a question that I had right on top of that it was definitely a stupid question um I don't think any questions are stupid are you sure I

think these are good questions these are important questions because like what it doesn't like you know these are like if you're asking questions about something because you're not an expert in that field like you can't be an expert in every field if I ask questions about endomology I'm

gonna have no idea what's going on okay I'm like I'm still trying to remember what the difference is between a bug and not a bug right like I don't know um I'll give you some clearance on that okay but the problem is is you study the universe yes so could your field be any broader like no

no it could not literally everything yeah and this this can be a problem too like when I give talks I have to be prepared for anything like that and that used to freak me out a lot and now I just feel like like I just have to I have to read as widely as possible and sometimes I'll be like

I have no idea but like I gave the talk about gravitational waves in rally the other week and one of the questions was uh tell me about the great red spot on Jupiter and I was like gill it's a storm it's been shrinking uh there's a there's a spacecraft looking at it you should maybe talk to somebody

who studies studies about that the great red spot by the way that's a actual name it's a little on the nose also people mix it up sometimes with the great dark spot which was near Jupiter's northern pole so y'all call me let me name some of these things also how did Katie feel about the detection

of gravitational waves this was the LIGO project you may have heard about in 2016 the detection of gravitational waves by the LIGO instrument um it was probably the biggest discovery in physics in my lifetime damn yeah that's a big deal it's a super big deal um I win the announcement so the first

the first detection was last year sometime or well the detection was the end of 2015 and it was announced I guess um during 2016 um the the announcement was in I don't remember what time zone it was or whatever but it was such that it was gonna be 2 a.m. local time in Melbourne and so a bunch of us

got together and like had a party yes in in a university department like we brought food and booze and like we watched videos and like we took like we took selfies it was really late um but we were just like we got to see this live you know and and there were there were two people in the room

who were who were part of the collaboration um so they they already knew what was gonna be done but the rest of us like we'd heard rumors but we didn't know for sure what was what that was gonna be announced um and yeah it was it was just a huge party and it was a we were really excited

and like we just everybody was like clapping and stuff when it happened and I mean it was it was a huge deal the way that it was announced was like a press conference from like an awesome 80s movie yeah ladies and gentlemen we have detected gravitational waves we did it

I mean how cute is that so that was Dave Wrightsy he's a laser physicist and he's director of the Lego lab and I love that audio so much it's just like pure triumph like the last scene of a Schwarzenegger movie or something we have detected gravitational waves yeah yeah yeah no I

remember that very clearly so explain to me why the detection of gravitational waves is such a big deal okay so so first gravitational waves are are ripples in this fabric of space time so you know the space space can be bent around massive objects and when massive objects are moving through space

if they're moving in an accelerated way which could be in an orbit an orbit as a kind of accelerated motion that creates ripples in in this sort of space time fabric which is kind of hard to visualize and explain but it ripples through space and so like when you have really massive objects moving

really quickly that can make large disturbances relative to other things I mean if I wave my hands I'm making gravitational waves but like that's not detectable so so so two black holes orbiting each other make really big detectable gravitational waves especially when they get so close that

they're about to merge into one thing so you can have two black holes in a binary orbit orbiting each other and then as they get closer and closer the signal gets stronger and stronger you know the waves get stronger and stronger and then they merge and that makes this big sort of burst

of gravitational waves and the way that gravitational waves work they're not like ripples on a pond usually when you see a visualization it's like ripples on a pond but that's that two-dimensional analog you know again and they're not like if you're if you're standing there the gravitational wave

like moves your space that you're in but it doesn't just like move you up and down what it does is it stretches and squeezes the space that you're in so let's say that you're standing there and a gravitational wave comes and hits you in the face what that does to you is it stretches your

space a little bit so you get a little bit taller and at the same time a little skinnier and then a little bit shorter and a little wider and like it oscillates back and forth so as the waves are coming at you each wave is giving you that like that stretch and squeeze stretch and squeeze

and so it's actually distorting your shape oh my god this is happening this is like a big boy or a young and it's it keep like for everything that creates gravitational waves is it's doing this to us all the time micro micro basis yeah yeah so so the LIGO experiment is built to detect

these things they have two detectors and each detector is like it's an L-shaped thing each arm is four kilometers long now if you've seen photos of this you might think from a distance is some shit that we built like on Mars because there's just this treeless

ochre landscape in the desert it seems to look lonely in every direction but no it's just Washington state and they shoot lasers back and forth along these two arms they meet at the center and and they're measuring the lasers are just there to measure the length of those arms

basically and when a gravitational wave comes and hits that detector it makes one of the arms a little longer while the other one gets a little shorter and vice versa depending on the direction and the you know phase and everything so if it if it does that then the detector can detect that

the length of the arms has changed and and then that's the signal is the changing of the length of the arms and the level on which that happens so this is four kilometers right yeah that's about two and a half miles America the first detection when it was detected the the length that four kilometer

arm changed in length by a thousandth the width of a proton oh my god yeah that's a teensy tiny that's really small and this was a huge collision yeah yeah this was like it was a 1.3 billion light years away so it was very far but it was like the black holes were around 30 times as massive

as sun and they provided and so it was a pretty strong signal like it was a surprisingly strong signal like if you actually looked at the data raw data like you could see it which is not usually the case in in this kind of field usually like you have to do lots of processing but like you can

see the signal is very strong so but yeah thousands the width of a proton so the you know your own height is changing much less than that right because you're not four kilometers long sure I'm so I'm getting a little bit not quite as tall and not quite as skinny and not quite as short

as fat as it's yeah not noticeable in a photograph say yes yeah yeah it's really it's a really subtle effect but but yeah so that's the gravitational wave it's the detection of that that change in length that sort of stretching and squeezing of space time and each time the black holes you know

black holes or or something collide you get this kind of like the the wiggles will come faster and closer together and so the frequency of this changing of shape is going up and the amplitude is going up and so it makes this kind of rising sound if you transmit it if you change it into sound

it's like a sort of like and the like end part is when they collide and the reason people change it to sound a lot is because the frequency of these waves coming like how how quickly the stretching and squeezing happens is about the same frequency as like sound waves okay so it is kind of audible

like if you change it to sound it's kind of audible and that was like the the boop heard round the world right yeah yeah it's called a chirp a chirp yes just a little yeah chirp a chirp okay you ready for this this isn't the sound of history so what does that mean going forward

for astrophysicism yeah and like how many more have we heard since then uh so there have been oh gosh I didn't even know the number like something like five um seen now uh and the most recent most recent one was it was two black holes but the one before that was a neutron

there was two neutron stars and those were a big deal because those when they collided also created a gamma ray burst a gamma ray burst super energetic explosion so we can't see gamma rays but the pack a punch and a burst and so we were able to see the collision from the the gravitational waves but

also from light and that was a huge deal and I can talk about that for hours um but it's it's a big the the whole thing is a big deal for a bunch of reasons one is that this like the existence of gravitational waves was kind of known indirectly because we'd seen systems where like you had two

pulsars orbiting each other so pulsar is a kind of neutron star a neutron star is like the core of a dead star um it's so we'd we'd seen things orbiting each other where the the changing of the orbit could only really be easily explained by gravitational waves kind of radiating energy away from the

orbit and so the orbit got smaller because gravitational waves were pulling energy away how um and sort of shrinking that orbit so so we had indirect evidence the gravitational waves existed but we'd never seen them directly and seeing like directly like detecting like feeling the

gravitational wave is a huge deal right and the gravitational waves were like the last the the last prediction of Einstein's relativity to be confirmed Einstein's theory of relativity remember our perception of the force of gravity is a bendy spacetime thing I'm very paraphrasing a

lot um so he predicted them 500 a hundred years about a hundred years before the first detection was made um so it was it took a long time right to see these things but so it was confirmed that and it's just this incredible laboratory for for relativity for physics um because by detecting

the gravitational waves um and looking at the signal we were able to determine that gravitational waves traveled the speed of light wow we didn't know for sure before that was part of the theory but we didn't know for sure so we we figured that out um it told us stuff about how black holes

are made like what black holes are made of sort of like the properties of black holes by examining very closely how they come together and and merge um how much energy the gravitational wave bursts creates you know um a lot of stuff about about that and then because now we can we can watch

black holes colliding uh in the distant universe we can learn about how black holes grow you know by when they collide with each other and that tells us something about how black holes grow it tells us something about how galaxies grow it tells us something about how stars form because black holes

are the end results of stars when you are a kid were you ever hoping that this that we would be able to detect gravitational waves um so like i've been waiting since i was a little girl um so so i didn't know a lot about gravitational waves when i was a little kid but there was there was a really

beautiful moment um during one of the the detection of the neutron star collisions when one of the scientists um was he was he was talking about the neutron star collision and the neutron stars when they collide they make a slightly different kind of like chirp sound okay here's a sound of the

neutron stars booping themselves together so the the black hole one is actually a lot quicker than what i said but the neutron star one goes like ooh it takes it which takes a while and it does it um so and there'd been simulations of this for

years i mean the scientists who was talking about the discovery said that he'd been waiting to hear that sound from nature for 20 years and he just did uh um and it was really touching i mean so for me i i knew about LIGO because it was um it was partly um headed by people at Caltech and

i was an undergrad at Caltech and so when i was an undergrad there um people were talking about a lot and there was there was a famous bet between like kip thorn and steven hawking or something kip thorn by the way is a theoretical physicist the 2017 noble laureate um about whether or not

gravitational waves would be detected by the year 2000 um i started a caltech in 99 um so they were not detected by the year 2000 so that bet was lost um but it was a funny thing because when i first got to Caltech they were building LIGO and it was this big deal and everybody's like we're going to

detect gravitational waves it's gonna be amazing and then um you know and LIGO was being built and i was like oh it's any minute now and then i i left Caltech and i went to grad school and then after a while i was like i haven't heard anything about this for a while you know and and i realized that

like they kind they'd kind of like they'd been like yeah we're gonna detect gravitational waves and then kind of got quite for a while and i found out like they'd were all asked about and they were like oh no it's advanced LIGO is so there are some upgrades of the years from initial LIGO

to enhanced LIGO to advanced LIGO it's kind of like the the tall gronday and venti gravitational wave detectors just then maybe you need a little more to get the job done really gonna do the detection the initial LIGO was like maybe it would get lucky but advanced LIGO will really see

something i'm like really and so like for a while i was like i don't know what i feel like i don't know if i believe that this is really gonna happen but then you know as soon as they turned advanced LIGO on like within like a week or something they they saw this thing so that's like

they really they really did it and it's the most like it's the most precise instrument ever built by humans um i think i read that somewhere it's like the the i mean you're measuring something so tiny it's crazy it's it's impossible i use it's incredible how like what went into it

in terms of the engineering and you know just the the physics and like they had to count they had to correct for things like the like how much the photons hitting the mirrors would move them oh my god oh my god that's a big part of the the noise in the signal like this is that's called the

photon shot noise they have to deal with that yeah so stuff like that i mean it's it's incredible that they were able to do this so can you get the chirp as a ringtone i believe you can you can i believe so yes would you get the the neutron whoop or would you get the well the black hole and

the black hole when you have to speed it up to make it sound cool um so you can still hear it but it's more like a like so so in the actual data it's like that that's kind of what it sounds like but then when you when you speed it up it goes whoop whoop but it's very quick whereas the neutron

star one it's like whoop i feel like yeah i feel like that's the way to go yeah yeah let's say someone is interesting cosmology but doesn't know a lot about it and is intimidated by it what is the best book to pick up i actually and this is i i don't know if you've ever read this but i was

i was in Thailand and i was staying in a hut and there were some there was a free book pile oh yeah and i picked up a book called quantum mechanics can't hurt you this book was actually called quantum theory cannot hurt you it's by Marcus chone and it's delightful i found my copy it's still

moldy from a monsoon it was good it was very it was very lay person's terms excellent but um i clearly don't didn't retain any of it but is there a book or a documentary or something that's just a good primer because like in this episode there's no way to describe everything but like

what's a good go to like astrophysics for dummies what are we talking here is there a pamphlet so i i wish i had a really good answer for this um i think we feel like you don't you're winsing the thing is like i don't i don't read a lot of popular level stuff and

there's a couple of reasons for that so number one she doesn't have much time to read non-papers because there's like a billion papers and when she does she likes to read about spaceships okay to when something is written for the general public astrophysicists have to take

that lay information and kind of back translate it to a more technical version in their head so it's like if you were a bartender and someone writes she drank a whiskey but you're distracted wondering a whiskey will do is it like a bourbon is this a single malt scotch was it a rye

Tennessee whiskey this is on the rocks was in a cocktail there's so much detail in it i mean shankerls written several books that are really good um so take a look at those um there's a physicist Katy freeze uh catherin frees who's a dark matter uh theorist like me oh uh she's a dark

matter cosmologist and she's written a book called uh cosmic cocktail and it's all about um about dark matter and also like some autobiographical stuff it's really cool uh what about what about movies do you have a favorite or at least favorite movie about space or cosmology you're like and

could i not answer some of them yes yes yes um okay so so favorite yes um so there aren't a lot of movies where i feel like the cosmology like cosmology is hard to have as a topic of a movie because it's just too big a topic and like stuff happens on cosmological time skills which is like

incredibly long times and so having something happen within a movie time frame is really hard um but uh there's a movie that i really liked for how it portrayed the scientist and it had some some some cosmology ish stuff in it um uh so that was sunshine okay which the science is wrong

just putting that out there it's it's about the sun has like burned out or is burning out and they have to fix it and none of that can happen all of that's false all that's fake but it's done really well in terms of like they have physicists who who acts like a physicist and and like they

have people who talk like scientists and i kind of just enjoyed it okay um so i thought that and then there's like a monster thing so anyway but i thought that was done really well um i really enjoyed gravity there's also bad physics and gravity in some places but i thought it was a beautiful

movie um and it portrayed space very well how do you feel about space balls i think it was funny it was a it's been a long time how hell yes that was good yeah other space movies like the Martian was fun interstellar had a very pretty black hole in it okay that's that you were being

you were being very complimentary and that is duly noted you are being a very nice person the black hole in the wormhole and interstellar were very beautifully done and done with um with proper relativistic equations it was very clever because what they did is they they they had

these simulations that are very very difficult and take a very long time on super computers and they gave them to the the um the people who do movie graphics who have really powerful super super computers and they're like no we need to do this black hole properly so they calculated it

and now they got some like papers out of it because the result was such such a good calculation that they were able to get actual science out of the the calculation done for the graphics in the movie because movies are better funded than yeah yeah yeah so it was it was a it was a very good move

but but you should you should know that the black hole in in interstellar although there are some aspects that are done very faithfully they did they did tweak some things so it actually would look pretty different um if we saw an actual black hole in real life so there are a couple of

things that were tweaked that were a bit different so speaking of movies Katie and I were supposed to go to one after this interview and we did but we barely made it because this is all really great information we hadn't even gotten to the wrap of fire round of all of your questions so

I asked your questions we raced to the showing and this poor woman had to smuggle a burrito and eat it in the theater I'm so sorry by the way we saw murder on the orin express it features a very bizarre mustache I will give it that so stay tuned it's a first two-parter

inology's history when we resume with your questions so you now have a solid base tune in next week to hear astro Katie address your questions including is there a name for the disorientation and panic one feels when considering the vastness of the universe there is are any of the sci-fi

movie methods to save the planet plausible or are we basically doomed if an asteroid uses us as a target will the universe expand forever what's the deal with multiverses are there aliens and speaking of your submissions I wanted to let you know I totally see the reviews you write on iTunes and

it's so appreciated rating and reviewing and subscribing is free it takes very little time and it helps allergies stay up there in the science charts so more folks know about it so thank you so much Katie is at astro Katie on twitter where she has approximately one billion trillion

followers and she has academic nomad on instagram so thank you to all you allegites for tweeting and grahamming and meaming at us and to all the folks on patreon who make the show possible it is currently 4 a.m. on a Friday night and I'm recording this to send it off to Stephen Ray Morris

he's going to help edit it and your funding is making this dream project possible and putting a lot of facts in a lot of human minds um you can also keep the show going by stopping at oligee's merch dot com and I also want you to know that yes it's super late at night and I'm recording this partly

because uh the mass of porridge that occupies the space where a brain would be had to spend a little longer trying to understand and explain these concepts that I thought and uh right now as I record this mill the night my neighbors had been blasting techno christmas pop songs for four hours while I

was learning about wormholes the world feels very surreal also congratulations to anyone who made it to the end of this episode man you stuck it out I appreciate that um as a special thanks I'm going to tell you secret that no one in the world knows earlier tonight I ate cereal I bought

from a gas station and I loved it so if you listen to the end of this episode feel free to holler analogies or alleyward I'm sure I'll have a new secret for you next week at the very end when we are back with Katie max Q&A so until then ask smart people dumb questions because I love it and we're just tiny meat blobs on a dust spec so let's just live can we live okay bye bye