Q&A: Our Universe and How It Works - with Jo Dunkley

[Music] how do we know what the evidence is for inflation that's a really good question so I didn't I didn't yet mention inflation but it's something I work on in my research so so I said that the universe is growing but I didn't see how the growth starts the growth started in the beginning and one of our ideas that's not a completely that's only a partial explanation is that at the very beginning of the universe there was nothing around at all except for this energy in space that we call the Implanon field and the energy in that space grew really fast in this thing we call inflation for a fraction of a second trillionth of a trillionth of a second space grew actually forced in the speed of light and there there are a few reasons why we think that it that it kind of works and one of the one of the our favorite reasons is that it actually produces the seeds of everything we see now so what I didn't get to explain is that you know the the stars and galaxies had to come from somewhere and actually we think that there were tiny features of it in the early universe that maybe were put there by this by this process called inflation that then grew to become the things we see now the all the features we see a week when we look at the we look at both of features in the universe and we look back to actually this light coming from the Big Bang that's what I study it all looks consistent with a story what we're looking for now is actually gravitational waves injected into space at the time of the Big Bang people may have seen results from the LIGO experiment recently were two colliding black holes distort space and make it ripple and send out ripples in time we're actually here actually the room actually would be growing if a gravitational wave passed through us right now then the whole of this lecture room would grow a bit as it passed through so we've seen them from black holes if inflation happened this initial very energetic expansion of space it would also inject gravitational waves so actually believe it or not the experiment that we're building and Chile the Simon's Observatory that's one of its big goals is to look for gravitational waves from inflation okay war in them right in the middle there where can you see there's a light the second row down tell you what you can get microphone to hidden and between that we'll find someone who's a bit closer as I stick your hands up again if you've got another question so will we eventually not be able to see anything because if stuff continues going faster and faster and if at the big bang stuff could go faster than speed like that means it could happen again doesn't that mean that it would eventually start going faster than the speed of light it's a really good question the answer is yes so it's a really good question so if as we think is the case right now things space is growing faster and faster then yeah that does mean that very far in the future all the galaxies that we that the beautiful galaxies we see in the sky they could vanish over this cosmic horizon I mentioned earlier which the things that we can actually have access to and we would then again think that we were alone now for a while our own galaxy would still be there but then it might get ripped apart too depending on how strong the universe is growing so we're not quite sure about that last bit but but yeah it's a genuine isn't it wouldn't happen for a while but it's a really good question okay can we not make this too depressing all the any bits of how hello oh yeah thank you for talking I've got a question aside from dark energy and dark matter what are some of the other big problems in astrophysics that keep you awake at night it's so they're not big enough not big enough my my probably the main questions that keep me up at night are dark matter and dark energy are two of my their main questions my third question actually we just talked about which is why did the universe begin to grow in the first place because we we don't know why and even if this thing that we call inflation which was this energetic expansion in the beginning happens why did that happen and and can we ever what's the furthest we could ever look to try and understand where it came from there are some wonderful ideas right now alternatives to this model for inflation for the beginning of the universe that that talk about something called a cosmic bounce a bounce in cosmology where the Big Bang is just the things shrunk and then and then bounced apart to produce the the growing universe we see now so certainly it's the case that when we talk about the age of the universe we are just talking about the time since the universe we can access began to grow that doesn't mean that there was nothing around before and it doesn't mean that there's not stuff elsewhere that's not really in our universe so we're quite we're quite limited in what we say when we say the age of the universe in the beginnings but those are my those are my main concerns there are other things that I find fascinating but well actually what we're the keeps me up at night is how to make sure I don't have systematic errors in my measurements but that's the truth about science again and then after this is your turn you've been very quiet some questions from over here so we're looking at the rubber were looking at the elastic band when you said that the Big Bang all those little blue dots would join together what would those blue dots actually consist of that's that's a really good question because actually it's quite right that we as you wind time back we don't expect that at the beginning when the blue dots were on top of each other that they were out to galaxies at the time so we think that if we could wind time back that if we could go back to when they were on top of each other that they would just be fundamental particles at the very very first instant they might be particles we don't know of yet but just after a fraction of a second they would be protons neutrons rays of light neutrinos and we think these mysterious dark matter particles and it would just be this sea of those things and then what would happen is that they would form hydrogen and helium atoms and then over millions of years little lumps in that soup of particles would be pulled together by gravity until after a few million years hundreds of minutes of use those big lumps could ignite to form the first stars and then they pull together to become bigger galaxies so the galaxies we know of these blue stickers have been around since you know half a million sorry half a billion to a billion years into the universe's history it's a good question okay your turn questions from this yeah we got sorry you're far away up there is dark matter and dark energy related in any way that's we don't know good question there's no reason beyond their name no they they seem to be quite different things are what this is interesting idea the simplest explanation right now although maybe it's not simple is that lips that simply dark matter is a particle we haven't discovered yet whereas the simple explanation for dark energy is the energy of empty space so we think they're quite different but you know when you don't understand 95% of the universe's energy which I sure didn't quite mention this the dark energy takes up 70% today of all the energy in the universe it's pretty big when you don't understand that much you have to have in your heads that maybe you've understood maybe you've got a bigger problem right so I think it's not inconceivable that we will find they're connected and maybe we'll end up with a big paradigm shift where a whole picture of the universe and how it works changes significantly I don't think we've got wrong what we're seeing now but our interpretation of it might have to change and maybe they are connected so don't you be you've been you've had you end up for a while I down the front here is the possible you could give us an idea of how fast these things in the universe are changing so we saw the Eagle Nebula yeah I mean how how long ago was that taken and then if we were to look in the same area space would it look vastly different there oh yeah no that's that's true this this the timescale would be well it's interesting so there okay so the timescale is kind of a bit related to how the life cycle of stars just for context so it's so for example again I said that stars like ours will live for 10 billion years and won't change but but more massive stars actually go through their life cycle much quicker in you know hundreds of millions of years so you might have lots of big heavy stars exploding and disturbing those kind of environments so the time scale of that would be then millions of years now there are other events that happen much quicker you know the single explosion of a star takes place in just you know seconds hours days but in terms of disrupting these things it would be more like millions to millions of years yeah okay yes yeah and then there's another one on the balcony after that it's bear in mind how long this takes and then really think about what it means for something to be a hundred million light years away so essentially you mentioned that it would take about four light years to get from Neptune for the light to get from Neptune to here right five hours five hours yeah sorry now let's say that if you manage to build a spacecraft for example that could approach the speed of light or reach the speed of light right time would be relative wouldn't it so if that's the case how much time would pass for the people that are on the ship in comparison to people that on earth and would it still be the same amount of time and keeping that in mind yeah would we be able to go even further considering that their time would be a much slower that is a good question and so it is true and I think this is one of the most marvelous things about physics is that you do discover that time passes differently how quickly you're traveling or how how massive an object you're near you know for example if you go near a black hole your time will pass slower and you won't age so much as if you're not near a black hole but you could you wouldn't survive very well but and so yes time will pass differently to a traveler near the speed of light it wouldn't pass differently to us observing it from here on earth because we're stationary so I think it's worth it's it's an interesting idea but the idea of getting us to near the speed of light is a technology far beyond where we are right now so yeah yes yes you're right time would pass differently and there's this famous twin paradox if you send a twin off on a rapid spaceship and and it comes back it will be a different age to the twin station on earth but I think our technology is not such that we are anywhere near that kind of speed has anyone worked out how different the time on Voyager is to our time here on earth you said that dark matter passes through us yeah all the time and so do neutrinos I always pass through us and I read this article in like the New Scientist which said there might be another type of Nishino other than three we already know code like a ghost neutrino they can't think of a better name yeah but how likely do you think that these ghost neutrinos exist it's a really good question it's actually was something I'm doing right now in my research so one of the things that I do is I try and actually measure the number of neutrinos through their impact on the behavior of the universe and so we're looking this there's one possible addition to one that's there maybe ghosts ones as well there's one that's called a sterile neutrino it doesn't interact we are so I'm that's one of the numbers I try and measure as a cosmologists is how many it is and at the moment we're kind of down to the fact that it's 3 plus or minus 0.3 well plus or minus means how uncertain I am so right now when I look at the cosmology data that I collect from my telescopes we don't think there's room for a whole other regular neutrino particle but this room for maybe a little bit of one that behaves a bit differently and that she would telescope I'm building now in Chile we're trying to narrow down any extra neutrino to to figure out what it is but it's a very interesting idea these are the lightest particles in the universe billions of them are going through your hand right now more than probably even this heavier dark matter and we don't understand it very well at all so that's that's something that I think is fascinating okay where are the microphone so it's pick someone that's close to the microphone to anyone Oh on the back row right next to you there anyone else from this side oh yeah I get that next time beep yes what's your favorite explanation for Doc Martin doc ng like you're personally what you oh yeah speculatively what do you think is more well likely well I think for dark energy I think the energy of empty space is the most likely because it's already kind of in our equations you know so oh yeah ok so this is a question so here because there's a problem I said that this is it might be the energy of empty space there is a problem that if you try and work out so empty space isn't really empty quantum mechanics tells us that this constantly energy being created and annihilating in any bit of empty space 70 space actually is like bubbling with little bits of energy creating an vanishing again and if you try and work out how much of vacuum energy there should be in empty space then the amount is many many many times different to what we observe and so the fact that we see this specific amount today we don't have a good theory to explain it so I don't have we don't definitely don't have a good theory to explain why empty space should have this amount but my sense is that it probably is that and that we need a better idea about why and that's partly based on observations well this this this is related to okay so if if this dark energy is something different from empty space then it will kind of feck the way that the universe is growing and the way that big clusters cosmic structures grouped together and we're increasingly improving our measurements of those and we're not finding anything that indicates anything different from just the energy of empty space but it may still be there but that would be my favorite idea for dark matter um and now I used I would have used it five years ago I would have said to you oh I think it's this supersymmetric particle there's a theory that comes out that says every all of our particles should have a super partner and this whole sector of particles we haven't found yet I would have said that five years ago but we haven't seen it at the Large Hadron Collider so I think it's something different and I think that probably it's a particle but it might be a whole family of particles so yeah right now I'm a little bit stumped on that one save room on the family tree yeah who's gonna go next where's the microphone that was up there oh it's over there is it okay what we see is in the solar system matter is concentrated in small areas hmm in the in the galaxies it's concentrated you know where it's very concentrated so the universe is completely heterogeneous it's homogeneous at all okay and we can look out from all different into all different directions from was but we are still stuck in this area in this in the region of the universe around us yeah and you know that has a certain density mm-hmm and that's different to all the other areas of the universe well actually on average no so this is something that this is something that on average yes we're seeing some regions that are more dense or less dense and others this holes between these calyxes and process of galaxies but an average of averages out over the observable universe is being approximately average but they're also the thing that I I didn't really have a chance to talk about this the thing that I look at is actually if you go back and you can see the universe as we're able to do at she when it was very young only 400,000 years old which is a picture that I take with the telescope I showed you at the beginning if you go back to that point the universe almost featureless it's the same density everywhere has features that are only one part in a hundred thousand its uniform and so we actually can see back to the point at which the were no features and the whole of the universe that we can see was just the same everywhere so we actually can trace the growth of these tiny features to these big you know some some parts of space end up as a big void empty of stuff some parts up end up as a big heavy part but we've done that now and we've seen that evolution and I that to me that's you know it's it's extremely compelling because we've got other people waiting to ask okay up here where's that microphone gonna fear yeah slightly different question I've decided that this is what I would do so are there any British universities you would recommend all of them yeah there's no physics going on in many departments I think I mean the way I would look around is is is look on websites and see what the researchers are doing because there are courses in many of the universities and in the UK mostly you would start with physics you can start doing astronomy I start and he'll and started doing doing physics and then you can specialize in a given area I think that's great because even if even if I'm biased and I say yes do astrophysics I think actually if you like doing physics you should study it and then decide what you want to do because there may be something that you haven't come across that you think is truly fascinating so but I did I recommend as well looking on websites and seeing what the researchers are doing and see what grabs your interest but yeah it's that's great and building instruments as well everyone always yes that you can only do with the science I'm an experimentalist does it show and because people build the instrument and one thing we do have in the UK as a huge amount of expertise at satellite but I mean you can probably say it's more about that yeah no that's I think that's really true and I and and and that's exact and that that building stuff and I feel because I am nice data from telescopes and the only reason I can do that is because my colleagues like developed these extraordinarily sensitive cameras and the telescopes to do it and I kind of been slightly regretful that I can't do that myself right I just take the data and turn it into numbers and it's so that yeah okay heard from the balcony in a while up there and thank you very much for your talk um I was just wondering you said earlier about the limit of the oh sorry the limit of the observable universe being much larger than the age of the universe yeah and I was wondering just how that was how about oh you know that's a really good question so if the universe weren't growing at all and it's just static then then the then the radius than the distance that light can travel in 14 billion years is 14 billion light years but actually if space is actually growing at the same time then the distance actually gets to be bigger because the space in between as the light is traveling the space is getting bigger and bigger as the lights traveling so it ends up having further to travel than it would have done if the universe we're not growing so it's kind of a neat calculation that we get our undergraduates to do when they first do cosmology is work out the distance of something in the expanding universe and for a simple universe just full of dark matter not that simple regular matter it turns out to be 3 - exactly 3 times the age of the universe and that would give you like 45 billion years but then this dark energy makes it a bit more yeah I'd never thought that's what he's saying bolt was doing before but now I'm never gonna see that again ok we got questions bright lights up here there's microphones up here I think that last question was probably my question which was I was going to ask you to expand on what you said during your lecture that although the universe is 14 million years old it's actually 50 million years old oh it's not no no no no no but I'll expand on that sorry ask him it so I expand on that yes the question is you said that the universe is 14 billion years old but then you said well actually it's 50 million years let me let me be clear yes the universe is 14 billion years old give or take a bit but the radius the distance to the edge of the observable universe is more like 50 billion light years and that's because the distance to the edge of the universe is the distance to the edge of a universe as it's been growing as an aside the definition of distance is a little complicated in cosmology and other thing we teach our undergraduates is distances don't really mean you have to be very careful you mean my distance if the distance you're measuring is growing as you're measuring it and maybe your ruler is growing as you measure it as well so it's it's kind of fun but it's but the broad picture is that I'm not saying I'm definitely saying it's 14 billion years old but I'm saying the distance in a growing universe that light can travel in 14 billion years is further than 14 billion years it's roughly three times further yeah brilliant talk thank you is the universe expanding into anything and are there any clues from the early universe as to what potentially is on that border no it's not expanding into anything it's a good question so there's a limitation to my model of the 1d universe one-dimensional universe which is that this elastic clearly has some ends but we think that the real universe is if it were one-dimensional has two options the two options are either this piece of elastic is infinitely long it stretches on forever each direction or it's connected up like this okay quite possible and and so when we go to three dimensions it's possible that the universe is connected up in three dimensions to now you need a four dimensional brane to picture as three-dimensional universe sketched up but we can do a little bit so imagine you had imagine you're connected bit like a doughnut it so doughnut is the next level up in two dimensions you connect it if you take a piece of paper you can wrap it up into a tube and then you can wrap it round into a doughnut and that would be a two-dimensional space that is kind of fine the surface of a doughnut is finite and so it's possible that the whole three-dimensional universe is finite to such that I wrap up each end which means that I connect up these bits and I connect up these bits and I connect up these bits the fun thing about that is that any direction you set up in your spaceship you'll eventually come back to where you started and we don't know which it is what we do know and is something again that I do my research is that we know that if it's connected up like this that the size of the universe that's connected up is bigger than our observable universe because if it was smaller this wonderful thing would be true which would just be awesome is that we could it be like to be living in a Hall of Mirrors we could see the same thing in our universe multiple times because we'd see an image it comes from something it would go all the way around the universe come back and I'd see it again as it was further in the past so it see the same repeated image out in the universe we don't see that so we know that if it's finite it's got to be that big if it's not finite it's infinite doesn't have edges and this is this thing that that so we think and the connection to that is that often people think of the edge because they think of the big bang as coming from somewhere and shooting out to an edge but we really think that the stretching of space of the Big Bang produced is a stretch that really did happen everywhere like the elastic isn't growing from one place so we can just imagine shrinking an infinite universe down it's it's infinitely smaller but it's still in discussions if you worried about a thing question ask it anyway because you won't be the only one we've definitely got one up there and see a lot of waving going on over where is it can't see ask away have we moved away from just the explanation of a single inexplicable event I'll be looking at multiverse things a little bit there I heard there was a an anonymity and non-normal normally in the Cosmic Microwave Background we know does that so could show a connection possibly to another universe there's a good question so they have the worst some some kind of there were some ideas a little while ago that maybe whistling features in this in this very old light from the beginning of the universe those are not there convincingly and there was some and and there were some claims that they were there they're not there I work on this data and but there is definitely still the answer I'm looking I didn't see where the question where the question was coming for spotlight I know it came out of light came out of nowhere Oh up there cool great okay so it's quite possible and I know I didn't get to mention this that it's possible that like part of the universe inflated quickly to become an expanding quickly to become the bit of the universe we live in our whole observable universe and perhaps far further it is another idea is that other pieces of the universe very far away from us would have started expanding at different times to ours and this is one of the ideas that we call the multiverse which is that there actually many different you can get some inflation happening a growth of the universe happening at different times in different places and they would have different conditions inside them and they would then be kind of their own universes that is still a possibility it's it's actually one of the reasons that some scientists don't like the idea of inflation because the argument goes that you would then get so many bits of the universe blowing up to produce kind of arbitrary range of physics physical laws that the possibility of getting one that looks like ours becomes very unlikely but I think the answer is that that could be the case and we don't know and it's going to be hard to find evidence for it we do look in their closet microwave background for it but I'm not convinced by any evidence yet I think what time for one more question is someone over here on the edge here yes very interesting is there an explanation for the disparity in the age of the universe calculator from the cmbr and from Hubble's constant that is a really good question and something I'm working on right now so so right now okay when you look at the galaxies expanding around us with these Cepheid stars we get a number for how fast the universe is growing and it's a number that's 73 kilometers per second per megaparsec what does I mean it means that a galaxy galaxies are typically separated by about a million light years or so about something that we call a mega parsec in units of astronomy is one of us like it means that typically a galaxy that's one galaxy over from ours would be moving away from us at 73 kilometers per second and one that's twice as far moving twice as fast when we go and study the data this this this relic light that we can see actually from the Big Bang itself where we're actually doing the biggest I told her big triangles when we look back at the edge of the observable universe 214 billion years back we actually measure triangles that are 14 billion what no 50 billion light years long and doing that we end up with a number that's 67 or 68 kilometers per second per megaparsec and they differ by more than the uncertainty in the measurements and and it's fascinating to us in cosmology right now we're not sure whether it's different because these two different numbers are different because one of the experiments has an error that they haven't accounted for and uncertainty that they haven't properly included which i think is reasonably likely having worked on one of them so I work I worked on the Planck satellite which made them one of measurements or it's actually that we have the model for our universe wrong which should be fascinating and the possibilities that could there were there are things that could happen like neutrinos could behave differently to expect or there could be extra particles we haven't come across yet or something weird is happening actually the telescope I showed at the beginning right now what I'm doing right now is I'm trying to make an independent measurements of the expansion rate from the CMB from a different experiments to see if there's anything we can understand more on that so I think it's yeah it's exciting times well that's a great point to finish on so Joe will be outside immediately after this with copies of her book so I encourage fabulous I think not I encourage you to buy that get Jays to sign it and before you go please join me in congratulating Joe [Applause] [Music]

Channel: The Royal Institution

Views: 17,391

Rating: 4.8650603 out of 5

Keywords: Ri, Royal Institution, universe, jo dunkley, expansion, inflation, cosmic radiation, cosmos, planets, astronomy

Id: 2kdk_I0fKPE

Length: 31min 13sec (1873 seconds)

Published: Wed Jun 12 2019