Why Scientists Can't Agree On The Age Of The Universe - Featuring Dr. Becky | Answers With Joe

this video is supported by skillshare the age and the size of the universe go hand in hand and that's something we've been trying to figure out since we first realized that that those lights in the sky are stars just like our own sun so maybe it shouldn't be a surprise that the person who cracked the code was a literal human computer what might be less obvious is that it was a woman and she was deaf at that her name was henrietta swan levin she worked at the astronomy department at harvard even though she couldn't go to school there because harvard didn't allow female students at the time the time being 1898. but yeah back then computers were people that was a job you know the astronomers would give numbers based off their observations to the computers they would go off and do their calculations and come up with the answers there were entire rooms full of math whizzes with slide rules in order to do the things that we can do today on our phones and most of these computers were women because it was considered a non-creative support role so you know they could go crunch their little numbers and leave all the thinking to the men welcome to the world before fairly recently actually real quick there's a corollary to the film industry here because early on in the film industry most of the editors were women because for the same reason it was considered a non-creative support job all right darling all you got to do is cut after we say action and before we say cut you think you can handle that sweetheart here go get yourself some more lipstick there you go but many of these early editors took this support job and made a whole art form out of it and completely changed filmmaking forever you know innovators like thelma shoemaker dede allen andy coats and vernafields they just completely reimagined the art of visual filmmaking and became legends amongst filmmakers similarly henrietta swan levitt took this support role and created the tools that opened up the universe to us officially her job was curator of astronomical photographs at harvard and in this position she was able to gain an insight into certain stars called cepheid variables what she realized is that these stars pulse and they pulse at a rate that tracks with their brightness so if you're looking at a sepia star you can time the pulses and figure out how bright it is so you compare that to the brightness that we actually observe and the difference can tell you how far away that star is this is known as a standard candle and this was a game changer because there was a huge debate going on at the time about the scale of the universe it was the cosmological crisis of the 1920s some people like astronomer harlow shapley believed that the milky way was all there was that there were no other galaxies that our galaxy was the universe another faction led by heber curtis believed that the milky way was just one of many galaxies and those weird spiral nebulas that we're seeing up there are actually whole other galaxies way off in the distance shapley and curtis had a back and forth series of papers that were disagreeing with each other over this topic they were the the diss tracks of their day but ultimately it was edwin hubble who worked with henrietta swan leavitt who was able to put this debate to rest he is leave it's cepheid variable technique to prove that the universe is far more than just our one milky way there are billions of galaxies out there each one made up of billions of stars the universe just kept getting more ridiculous so this pretty much sealed hubble's fate as a legendary figure in astronomy but while solving that cosmological crisis he kind of set up another one the one that we're dealing with right now [Music] the crisis came because while studying these galaxies hubble realized that they were all moving away from each other but not just that they were moving away from each other but the further away the galaxies were the faster they seem to be receding this means the universe is not only expanding it's expanding at an increasing rate and this rate has become known as the hubble constant and it was recognized pretty much right away how important it was to get this number accurate because it not only told us how the universe begins it also tells us how it ends because if the universe is expanding in all directions that means that 10 minutes ago it was a little bit smaller than it is now and it was a little bit smaller 10 minutes before that and a million years before that and a billion years before that it just keeps getting smaller you can see where i'm going with this this was proof of the big bang and that was a big debate that was going on at the time too some scientists believe that it came out like that some believe that it was static and infinite like einstein once upon a time did others believe that it was finite but static there was a lot of debate over it but this changed everything this proved that the universe had a beginning and then it would likely continue to expand forever so hubble put his brain on trying to calculate what this constant might be and he came up with 500 kilometers per second per megaparsec a megaparsec is about 3.3 million light years so basically for every distance of that that you look out beyond that it is expanding 500 kilometers per hour per second more than the distance before it you got that now unfortunately for hubble this couldn't have possibly been right because this would have made the beginning of the universe to be about 2 billion years ago and geologists had already dated the earth at far older than that and it also implied that the milky way would have been a monster galaxy like way bigger than any other galaxy in the universe so he was he was way off but in the 90 years since then hubble's constant has been refined and recalculated over and over again using much better technology including the telescope that bears his name and it began to settle around 72 kilometers per second from megaparsec and then everything changed starting in about 2009 the numbers went from being bang on accurate and agreeing with each other to disagreeing but within the range of error to being fundamentally incompatible assuming everybody was doing their math right and this sets up our current cosmological crisis which i will try to explain the best i can but please bear in mind i'm not like a phd in astrophysics from oxford or anything like that so what i did was i got somebody who exactly is that and that's dr becky smith hurst from the dr becky youtube channel and we talked about it she sent me straight and she's going to chime in in this video dr becky smithers hello i say that right did you see your last name yeah you said it perfectly actually all right so there are two methods we can use to find the hubble constant there's actually several different methods we can use but i'm going to focus on two today there's the distance ladder method and the cmb method the distance ladder method is based on the standard candle thing that i talked about a minute ago so it's basically like you figure out the distance to a nearby object and then use that to figure out a distance to a further object and then on and on and on like a ladder for instance one method you can use to calculate a nearby star is a simple parallax method so when the earth is on one side of the sun you take a measurement and then you take a measurement on the other side of the sun do a little bit of triangulation you can figure out how far away it is and that works pretty well up to about 10 000 light years away so you can think of parallax as the first rung of the ladder and then maybe red shifting might be the the second rung of the ladder it gets way more complicated than that i'm simplifying it very much for this but over time this method has been used to more and more accurately get to a hubble constant but in 2003 a new method entered the scene and this was being done using the cosmic microwave background radiation or the cmb the cmb it's come up quite a bit on this channel i don't need to go too into detail on it but it's basically the imprint of the big bang yeah energy created in the big bang got redshifted over time into the microwave range and we can measure that and in fact you can hear some of that in the static over a radio antenna or tv signals the cmb is super cold only 2.725 degrees kelvin and you've probably seen this map of the cmb around but what you don't realize at least i didn't realize this is that the hottest and coldest parts of this map are only .0002 degrees kelvin difference it's kind of amazing that we're able to do this small though they are these variations can tell us a lot about the early composition of the universe and the distribution of energy that then turned into the first atoms and matter and we can kind of calculate back from there and figure out what happened in between so when we first started using the cnb to calculate the age of the universe and the hubble constant we were using the w map telescope which was by far the most accurate way of doing it at the time and the first calculations that we came up with thankfully we're right in that same range around 72 kilometers per second for mega parsec so it lined up perfectly with the distance lighter method and the scientists were like yes that's it that's my beautiful belissima that's what you that's the gesture you make when things work out the way they're supposed to right yeah that didn't last long because with every technological advancement our numbers became more accurate but they also began to drift away from each other and by 2014 they weren't compatible at all anymore everything that we do that's very local around us always comes out in sort of the 14 and a half ish pile of evidence and then everything that's done with the cosmic microwave background comes out in the 13.8 ish billion years evidence pile and so we've got these two growing powers of evidence and everyone's a bit like um and we don't know if it's going to turn out that there's something wrong with one pile of evidence or not and then that'll bring the two piles together or if there's some new physics some new hypothesis that explains why we're getting two different answers and if we can account for that new physics then that brings them together everyone was either working with the two bits of data and sort of ignoring each other and saying no no the other team must be wrong there must be something wrong with what they're doing um or they weren't considering any necessarily new physics but then after that paper came out it really was sort of like a kick up the book basically for everyone to you know say okay now we this has gone too far now we need to actually figure out what is wrong here and i think that's sort of the supernova people were like yeah they'll just find something wrong with their data eventually it'll be like you know there's nothing wrong with ours we've been doing this for hundreds of years you know yeah that's that's pretty new right yeah so that uh comes sort of from the last couple of decades when we managed to get my creative telescopes into space and we could get which is sort of like the kobe satellite the wmap satellite the planck satellite have all done this and so with that we were able to get much more precise measurements that we needed and the thing was there was these two separate satellites wmap and planck doing the same thing and they both found similar results so that would mean they both had a systematic somewhere in their data as well so it it's pointing towards it could be new physics that could bring those two evidence powers together it also changes when the universe will end which seems like a good thing to know because whatever this hubble constant turns out to be this expansion rate determines the fate of the universe now by all accounts the universe is expanding much faster than the gravity could possibly pull it back together so that kind of rules out the idea that gravity would slow the expansion and bring it back down to a big crunch and then you know a singularity and big bang over and over again a cyclic universal model basically that went out the window a long time ago we now know that galaxies will continue to spread further and further apart the light slowly going out as all the stars go out over time until eventually it's just nothing but a bunch of black holes radiating out hawking radiation for google years the dreaded big freeze the hubble constant determines how that's going to play out as well so this has created the cosmological crisis that we're currently dealing with and like i said before these are just two ways of measuring it there are many others there's one that involves red giants that produce its own number they started using gravitational waves now that we can detect gravitational waves as a method and that's produced its own numbers and none of these are agreeing with each other and nobody knows why but there are theories and one of the theories has to do with a quirk in the geometry of the universe the question of whether the universe is flat or curved has been debated for decades now and i'll be honest this is where my brain starts to melt so how about i just uh let dr becky take this one yeah so when we talk about cosmology we're always talking about you know fitting this cosmological model to the data that we have coming up with the model that how much stuff is in there and what shape is the universe so that we go from cosmic micro background to what we see now and the the shape of the geometry of the universe is actually a big factor now there's a lot of evidence locally that says suggests that the the universe has what we call flat geometry which means that if we set two parallel lines going they'll never meet ever in the universe they will always remain parallel but the paper that came out back in 2019 that was like crisis in cosmology tried to fix the crisis by saying okay the universe doesn't have to be flat what if the geometry of the universe was closed or had this idea of positive curvature which would mean that if you set two parallel lines going they would meet eventually because of the shape that they're traveling over so like on a sphere like on earth for example longitudinal lines they're parallel at the equator they meet at the poles right my brain's starting to melt i knew this would happen basically in a curved universe lines would eventually cross each other whereas in a flat universe they would never cross they would stay parallel forever but if the universe is expanding then wouldn't those lines go away from each other which wouldn't that be negative curvature my head hurts these are just ways of saying that the geometry of the universe would affect the way the hubble constant gets measured maybe even differently in different places so that's an option now there is one other explanation and that's just that maybe there's some new physics we just haven't discovered yet you know newton revolutionized physics with his laws of motion einstein created another revolution with relativity and maybe there's another revolution out there just beyond the horizon of our knowledge that could put an end to all this and explain it all and create a whole new field of science in the process a whole new field of science that would probably open up a lot of doors to new opportunities and technologies that we can't even think of now jet packs finally i'll let dr becky chime in on this i thought she had a really interesting thing to say here but in terms of like you know why bother in the first place um my thing is always like well just curiosity like why did we cross that ocean why did we climb that mountain like because you want to know right you want to expand the boundary of human knowledge but also i think the secondary thing is you just don't know what's going to come out of that kind of research right like by pushing to have say better telescopes or better ways of analyzing the data or better image reduction there are so many things that can that can come out of of that digital cameras like ccds these these chips that go in digital cameras were pushed forward by astronomers being like we don't want to use film anymore it's not good scientifically you can't record the exact brightness of something you only record like a like a difference in brightness across a plate kind of thing uh and also you know better ways of transferring data and wi-fi came out of that you know like that all came from astronomy and now we're in an era where especially in radio astronomy where they're taking data at a faster rate then they can get the data off the servers and onto their computer oh wow you know because they're pushing like a computer people can you sort this out because we literally can't get the data fast enough that's going to increase you know data transfer times which i'm sure everyone will be happy before you know it'll speed up many transactions across the world in terms of like finance or even calls like this analyze that data the image techniques might go into medical imaging or they might go into sort of like analyzing cctv footage you know all this kind of stuff that astronomy really is the an imaging science so anything to do with imaging might somehow benefit from people saying i want to know the age of the universe which i think is a fun thing to say like you don't know necessarily you can't call it now what it's going to be but indirectly they will somehow benefit so as crises go the cosmological crisis is probably not the most important one going on out there right now but it means a lot in the world of astrophysics and by finding an answer to it it could open up some amazing opportunities for the future so i want to say thanks again to dr becky for setting me straight on this it was a really fun time talking to her i am going to release the entire interview on thursday so if you're watching this in the future i'll link it up down in the description or put a little thing up here but uh definitely go check that out we go further into depth on this topic but also just other things like just what it's like to be an astrophysicist and whatnot it was a really good time and and uh i really enjoyed talking to her and also while you're ready go check out our youtube channel she does a really great job of breaking down these big science topics into chunks that you and i can actually understand it's it's a rare talent for somebody who actually has a phd in this kind of stuff to be able to do that but yeah however we find an answer to this it's likely to be a huge aha moment in science you know a moment where somebody was able to connect disparate ideas that hadn't been connected before and come up with a new idea that blows everybody's minds but aha moments are important in any job so if you would like to 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Channel: Joe Scott

Views: 333,732

Rating: 4.9132848 out of 5

Keywords: answers with joe, joe scott, dr becky, hubble constant, cosmological crisis, henrietta swan leavitt, cosmic microwave background, age of the universe

Id: RdJx34szLjs

Length: 19min 28sec (1168 seconds)

Published: Mon Jul 27 2020