Brian Cox - Is The Universe Infinite?

does the cosmos go on forever is an  age-old question in philosophy and   science the observable universe is finite in  that it hasn't existed forever it extends 46   billion light years in every direction from us  but what lies beyond the observable universe   what we know for certain is that the  universe is bigger than we observe it to be   essentially because the farthest edges of the  universe we can see don't look like edges at   all the observable universe is still huge but  of course it has limits that's because we know   the universe isn't infinitely old we know the  big bang occurred some 13.8 billion years ago   we have a thing called the sloan digital sky  survey which maps the positions of galaxies   so you know how much of the sky you've surveyed  and you know how many galaxies you've counted   and then you can spread that across the wider  universe and you get this picture of a vast   and possibly infinite universe we know that the  universe are very strongly suspect the universe is   much bigger than the piece we can see so we have  good reason to think that's the case whether it's   infinite or not is another question can you pitch  your infinity well no one can pitch your infinity   we say the universe began 13.8 billion years ago  so that's a measurement because we can measure   the speed that all the galaxies are flying away  from us essentially it's that you can run time   backwards if you like so to find out when  they're all on top of each other it's quite   a simple measurement and we've done that so we  say the universe began 13.8 billion years ago   but actually all we know really was the universe  was very hot and very dense at that time   and we have some theories that the universe was  in existence before that and perhaps some sort   of circumstantial evidence and that means that  actually the universe could have always been there   eternal when i talk to people sometimes they get  a bit some people get upset about that some people   would rather it had a beginning the idea that it  might have been around forever is more frightening   somehow than the fact that it began now it's  interesting the way that people's minds work   the universe is huge but it is only with  recent discoveries that we can realize how   inconceivably immense the universe or even  multiple universes may actually be eternal chaotic   inflation which generates multiple universes  builds from the theory of cosmic inflation   although inflation is generally eternal  into the future it is not eternal into   the past alan guff detailed in a paper  published in 2007 new inflation does not   produce a perfectly symmetric universe due  to quantum fluctuations during inflation   the fluctuations may cause the energy and matter  density to be different at different points in   space quantum fluctuations in the hypothetical  inflation field produce changes in the rate   of expansion that are responsible for eternal  inflation those regions with a higher rate of   inflation expand faster and dominate the universe  despite the natural tendency of inflation to end   in other regions this allows inflation to continue  forever modern physics has radically changed our   picture of the gnome cosmos it has offered us not  only glimpses of what the future of the universe   may look like but it has also offered us a view  for the overall shape of the universe itself   from the theory of inflation the best way to  explain the universe the properties that we see is   that it's very much bigger than the piece we can  see so for example we measure space to be what's   called flat so if you imagine slices of space  let's imagine slices of them at different times   so you just slice the universe and it can have  a geometry right it can be flat like a table top   or it could be curved like a sphere or it could  be curved in the opposite direction sort of like   a saddle or a bowl and we can measure that and  when we measure it we see it's absolutely flat   and that's a very unusual thing for it to be  like because what einstein's theory says is   that the shape of space that the curvature is  basically determined by the stuff that's in it   that's basically einstein's theory of general  relativity puts stuff in space and it curves it   and bends it and warps it and stretches it and so  on and what we find is that there's precisely the   right amount of stuff in the universe to have  a completely flat universe the explanation the   most favored explanation for that is the universe  is way bigger than the piece we can see [Music]   because we cannot observe space beyond the edge of  the observable universe it is unknown whether the   size of the universe in its totality is finite or  infinite estimates suggest that the whole universe   if finite must be more than 250 times larger than  the observable universe astronomers calculate the   age of the universe by assuming that the  lambda-cdm model accurately describes the   evolution of the universe from a very uniform  hot dense primordial state to its present state   and measuring the cosmological parameters which  constitute the model over time the universe and   its contents have evolved for example the  relative population of quasars and galaxies   have changed and space itself has expanded due to  this expansion scientists on earth can observe the   light from a galaxy 30 billion light years away  even though that light has traveled for only 13   billion years the energy from the big bang drove  the universe's early expansion since then gravity   and dark energy have engaged in a cosmic tug of  war gravity pulls galaxies closer together dark   energy pushes them apart whether the universe is  expanding or contracting depends on which force   dominates gravity or dark energy besides dark  energy there is also dark mysterious stuff that   fills the universe that no one has ever seen this  hypothetical form of matter thought to account   for approximately 85 percent of the matter in the  universe is also known as dark matter but we have   yet to understand what it actually is so we look  into the universe and we see that there's a lot of   stuff there that's interacting gravitationally but  is not interacting strongly with the matter out of   which we are made and the stars are made so it's  almost certain that that's some form of particle   that fits beautifully and we see lots of different  observations the way galaxies rotate and interact   and even the oldest light in the universe the  so-called cosmic microwave background radiation   we see the signature of that stuff in that light  as well so we think that there's some other   particle out there and to be honest we thought  we would have detected it i think at lhc we have   lots of theories called supersymmetric theories  that make predictions for all sorts of different   particles that would interact weakly with normal  matter and yeah i think it's broadly seen as a   surprise that we haven't seen them at lhc so that  just may well mean that either they're a bit too   massive so we need more energy to make them and  we just haven't quite got enough are we not making   enough of them often enough to see them which  is one of the reasons we're upgrading the lhc   we may never have the answer to the question  is the universe infinite or if it does have   an actual boundary what we do know however is  that the observable universe is stupendously   large in volume the vast amounts of space includes  anywhere from 200 billion to a trillion galaxies   according to varying estimates and each galaxy  has on average about 100 billion stars these   gargantuan numbers boggle the mind and are  all inspiring when we look into the night sky   and try to grasp the ungraspable volume of the  universe this is the picture that hubble took and   you see that it's anything but empty it's called  the hubble deep field image it's one of the most   important and fascinating images in the recent  history of astronomy it's not empty it's got   lots of structure lots of points of light in and  virtually every one of them over 10 000 of them   are actually galaxies distant galaxies so they're  not stars they're galaxies now those galaxies on   average have 100 000 million stars like our sun in  them at least so a hundred thousand million stars   in each one of those ten thousand blobs the most  distant object in that image is 13.2 000 million   light years away now light travels at 300 000  kilometers per second 186 000 miles a second and   at that speed it's taken over 13 billion years  to travel from the most distant objects in that   image to earth to the hubble space telescope  now when you think that the earth is only   just under 5 billion years old it means that  most of the light from most of the galaxies in   that image began their journey began its journey  to earth before there was an earth and for some of   the most distant galaxies there they were over  halfway here when the solar system was just a   cloud of gas and dust it hadn't yet coalesced into  the sun and planets and moons of the solar system   so imagine what that looks like imagine what that  looks like when you extend it over the entire sky   well this is a beautiful map of the observable  universe every dot on that map is a galaxy   with 100 billion stars like our sun in it at least  there you see that the structure in there they're   not randomly distributed it's very interesting  we're beginning to understand where that structure   came from just to get some sense of scale that  little line up there that's the 1 billion light   year line so light takes a billion years to travel  from one end of that line to the other this is the   observable universe this is the number of stars  we know from observation are in the observable   universe at the moment 30 000 million million  stars just like our sun some big s and smaller 350   billion large galaxies 7 000 billion smaller dwarf  galaxies that's the observable bit of the universe thanks for watching did you like this video   then show your support by subscribing and  ringing the bell to never miss videos like this [Music] you

Channel: Science Time

Views: 1,056,266

Keywords: brian cox, universe, brian cox is the universe infinite, infinite universe, cosmos, space, time, how big is the universe, observable universe, cosmology, big bang, stars, galaxy, astrophysics, quantum physics, physics, science, science time, infinity

Id: xYlf8ZXeCiA

Length: 10min 41sec (641 seconds)

Published: Sat Feb 05 2022