Brian Cox - What's The Biggest Mystery in The Universe?

[Music] our universe is a beautiful elegant and strange  mysterious place at the same time it has baffled   curious minds since the very first humans gazed  into the night sky and wondered what's out there   could they ever have imagined future  generations would have a comprehensive picture   and explanation of how our universe began  probably not but that picture just as our universe   is expanding and we are learning new stuff about  the cosmos every day so this is an island there's   a hundred thousand million perhaps two hundred  thousand million stars like our sun there are   perhaps a billion stars in the center of this  galaxy shining brightly this looks like a star   that must be closer to us than that galaxy because  it's so bright it actually isn't it's actually   something called a supernova explosion this is a  star in the galaxy it's on the edge of the galaxy   it's the same distance away as the billion or  so suns in the center and the hundred billion   also stars in the disc same distance away but it's  going bro as brightly as a billion suns how could   that be one star growing as brightly as a billion  well it's something called a supernova explosion   the death of a massive star but it's actually a  very interesting one what we think that is it's   called a type 1a supernova it's something called a  white dwarf so that's the ultimate fate of the sun   it's a star that's burnt out all its fuel and is  just sitting there in space gradually fading away   but it's a white dwarf that had a companion star  orbiting around it now the white dwarf the dying   star sucks mata off the companion star until it  gets too big to support itself too massive to   support itself and then it collapses and it  explodes and we know that process very well   it was a process that was predicted actually  from quantum mechanics from our theory of atoms   and molecules back in the 1930s so it's a very  specific process and we can calculate precisely   how brightly that explosion should be because we  understand the mechanism beautifully so we know   how bright that is we know how bright it looks  because we've taken a picture of it so we can work   out how far it is away and this is the second bit  of evidence you need so we've got two things now   we've got that you look out into the sky and you  see that things are speeding away from us because   you can measure the shift in the light and we know  exactly how far those things are because we can   look for things like this supernova explosions  in the distant galaxies now these are rare   you get on average about one supernova per century  per galaxy so very rare but there are a lot of   galaxies supernova in hundreds of galaxies have  been measured and we've made a map of the universe   we've got the distant galaxies we know how far  away they are we know how fast they're receding   modern physics has given us a glimpse of what the  true nature of the universe is there is still so   much more to explore one big mystery in science  today is the mata antimatter asymmetry problem   but to better understand this complex issue  we have to grasp the nature of antimatter cern have managed to capture atoms of  antimatter hydrogen now antimatter i   should say gets made all the time it gets made  in these cosmic ray collisions we've been using   it for years in particle physics experiments  but we've never been able to build atoms of it   so get an anti-proton and put an anti-electron in  orbit around the proton for any length of time so   the great advance is that we've worked out how  to do that and that's interesting because once   you've got a hydrogen atom a hydrogen atom is  the best understood probably the best understood   system in the universe we understand how hydrogen  atoms work with extremely high precision because   they're very very simple so by building  anti-hydrogen atoms we can look in detail   at the way the differences in behavior if there  are any differences between matter and antimatter   and that's an enormous question because we don't  know whether they behave in precisely the same way   or whether there are tiny differences  we think there may be tiny differences   because we need to explain why there isn't  really very much antimatter in the universe today   when it was probably made well it must have  been made in equal amounts of the big bang   so that's a big question could it be dark matter  so that matters the other great question which   is a bit more perhaps a bit easier to see that  we might get an answer to is that another 25   26 of the universe is made up of something called  dark matter there's a lot of stuff we can't see   and we don't know what it is and it's something  like 96 of the universe so that's kind of a bit   embarrassing in a complete theory of the universe  some of it we think is in the form of dark matter   we don't think we're very sure actually there  isn't antimatter because you'd see it bumping   into matter and giving out lots of energy and  light and we don't see that so we think it might   be something else it must be something else and we  think there are certain kind of particles we think   we might find at the large hadron collider  which are very strong candidates for that   so it's not dark matter but it's interesting  because we want to see if there are differences   in behavior between antimatter and matter at cern  physicists make antimatter to study an experiment   the starting point is the antiproton decelerator  which slows down anti-protons so that physicists   can investigate their properties scientists are  also eagerly waiting for other experiments at the   large hadron collider particularly the discovery  of new particles which will hopefully give us   a better understanding of our universe this is  why there's tremendous excitement now at the lhc   there are hints of interesting particles a  particular one what we call around 750 gv 750   times the mass of the proton which is a signal  which is not statistically significant enough   as we saw in the supernova results actually the  dark energy results not significant enough yet we   need more data that's why the lhc is running now  to take it but those signals have caused already   just preliminary results that may go away with  more data and i don't know because we're analyzing   the data so i don't have any secret knowledge  i'm hiding away but if it's there it would be   a heavy particle a new heavy particle 750 times  the mass of the proton decaying into two photons   two particles of light that's that's what it would  be if the signal stands up it could be one of the   particles for dark matter could be one of those  could be though if you go more speculative and   exciting it's one of the signatures for extra  dimensions in the universe so-called collusion   graviton signals there are ideas around that  so it could be that at lhc we're on the verge   of making a breakthrough but that's the key the  points of the large hadron collider it was built   because we knew we could confirm or deny the  higgs model but it was also built because it's   operating in an energy regime in which we've never  operated before so it is certainly not ruled out   that there is new physics in that energy regime  while physicists can confidently say what happened   a billionth of a second after the big bang  the vast majority of the universe remains   unknown in fact we only understand about five  percent of the total composition of the universe   which is ordinary matter the other 95 percent  which consists of dark matter and dark energy   remains in the realm of unexplained cosmic  phenomenon 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 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 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 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   so we also look for them by the way directly so  we have experiments on the mountains and we're   looking for the rare occasions when these dark  matter particles bump into the particles of matter   in the detector the galaxy is swimming with dark  matter as far as we can tell but it interacts very   weakly with this matter so it doesn't bump into  us very often so we're looking for the direct   detection of it so it's five times as much matter  as dark matter than is normal matter then the   number is 25 percent of the universe so roughly  speaking about five percent of the universe is   normal matter the stars fives normal matter about  25's dark matter and about 70 is dark energy   so einstein's theory which works spectacularly  well says that if you put stuff into the universe   as we said before then it warps and deforms and  stretches and it very precisely tells you given   the stuff that you put in it how much does  it stretch and how does it stretch the thing   we observe is how the universe is expanding and  how that expansion rate is changing and how it's   how it's changed over time so we have very  precise measurements of that so then we can   use the theory to tell us what's in it given that  we know what how it's responding to that stuff and   that's how we discover dark energy so we noticed  that the universe's expansion rate is increasing   so the universe is accelerating in its expansion  which is exactly the opposite of what we thought 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

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Keywords: brian cox whats the biggest mystery in the universe, brian cox, brian cox universe, brian cox antimatter, antimatter, brian cox dark matter, dark matter, brian cox dark energy, dark energy, cosmos, universe, space, physics, particle physics, LHC, large hadron collidor, quantum mechanics, quantum physics, new particle discovered, dark matter particle, antimatter assymetry, astrophysics, biggest mystery in the universe, time, spacetime, science, science time

Id: _KaFl3SRnxQ

Length: 10min 23sec (623 seconds)

Published: Sat Sep 03 2022