Brian Cox - What Was There Before The Big Bang?

[Music] it's interesting this idea of the Big Bang created the universe that's what Einstein's theory says that's textbook cosmology if you like but the current textbook picture is there was a phase in the universe's life before the Big Bang if you define the Big Bang as the hot dense phase from which the universe appeared to sort of burst for 13.8 billion years ago and that phase is called inflation so what we think happened is that before that the Universe was accelerating exponentially fast it means it was doubling and doubling and doubling in size and the

numbers are ridiculous we think that if you started with the universe that was smaller than a single atom then it would be bigger by a long way than the whole observable universe 350 billion galaxies in it in less than a million million million million million millionths of a second so a very rapid exponentially fast expansion and when that stopped all the energy that was driving that expansion got dumped into space it heated it up it produced the particles of matter out of which we are made and all the things that we see out there in

the sky and that's what we see as the Big Bang so that sounds fanciful but that's standard cosmology at the moment the big question then is well what started the inflation what stops the inflation how long did the inflation go on for and the answer to that is we're not sure we don't know in the beginning there was an infinitely dense tiny ball of matter which started to expand and would eventually give rise to the atoms molecules stars and galaxies we see today but what was there before the Big Bang what was the state of

the universe before well everything the universe underwent a breathtaking Cosmic expansion doubling in size at least 80 times in the fraction of a second this rapid inflation fueled by a mysterious form of energy the permeated empty space itself left the universe desolate and cold and only after that did the hot dense conditions of the Big Bang emerge some of those theories suggest that the inflation doesn't stop all at once it stops in patches and every time it stops you get a universe and so some of these Theory they're called Eternal inflation theories suggest that there

might not be just our universe the bit that we can see but there might be many universes perhaps an infinite number of them and they may be being produced all the time so what to make of that but that's where her current modern cosmology is if Cosmic inflation correctly describes what happened before the Big Bang it may push the ultimate answer to the question of where we came from beyond the reach of science but that just pushes the question further because we don't know anything about what came before inflation and it's doubtful that we'll ever

know there are theories now that suggest as I mentioned that there may be more than one universe and potentially an infinite number it's a mind-boggling idea isn't it now I should say one extra thing if that's true then some of those theories say that what we call the constants of nature so things like the strength of gravity the speed of light the masses of the particles can vary from University universe and then you ask the question well why is our universe so perfect for life why do stars make carbon and oxygen the elements that you

need for life why is everything so beautifully balanced so that living things can exist the answer in these cases is because well every Universe exists every possible combination of the laws of nature exist if different universes so the reason we obviously the reason we we have to see a Universe that allows us to exist obviously we could ask the question well How likely is that well the answer there are an infinite number of them is it's inevitable because there's every possible kind of Universe And I stress that this is very speculative stuff but the first

thing I said about inflation the idea there's this exponentially fast expansion before the Big Bang if you want to use that language that's not speculative that's mainstream cosmology but this idea that that may lead to multiple universes is more speculative but it's still scientifically valid and there are people who do research into that and again this is an active area of research inflation tells us that the period of time before the Big Bang was extremely cold and it was empty of everything but empty space and that empty space carried energy that stretched the universe out

to this enormous size and into the initial State before the Big Bang but there are also alternate theories to cosmological inflation which tell us what caused the initial conditions that would eventually give rise to the Big Bang there's a theory there may be extra dimensions in the universe so imagine that we we're just living on a sheet of paper let's say then there are theories where here's our universe floating around and there can be another Universe floating around so there are more spatial dimensions and we're just on a sheet floating around in this bigger Multiverse

and then you can ask the question what happens when they collide together and one of the theories about what caused the Big Bang is that actually what it was was two of these sheets or branes they called so they collide together and separate and when they collide together they heat themselves up and you get something that looks like a big bang on that sheet of space and time if you like so that's another different theory for what happened before the Big Bang branes colliding into each other giving rise to Big Bangs Multiverse theories these statements

might seem extremely speculative and out of touch with reality but they do in fact have mathematical reasoning behind them and moreover theories describing the very early state of the universe do have experimental support the wonderful thing is that we can we're making measurements now I should say the experimental basis for all this is something called The Cosmic microwave background radiation of the CMB so we can look up into the sky and we can see the oldest light in the universe it was released at 380 000 years after the big bang it's when the universe cooled

down sufficiently for atoms to form and at that point the universe became transparent and that light has been traveling through the universe ever since and we have a satellite up at the moment called Planck so European satellite that's been taking detailed pictures of this light and in that light it's like a baby picture of the universe like a scam a baby scan of the universe in a sense and so you can look to the universe as it was in its very earliest days and see different structures and different properties of that light and they give

you the clue as to what happened right back at the beginning of time the beginning of the universe and that's where these theories are getting their experimental support the twin pillars of modern physics are Einstein Stein's general relativity and quantum theory to understand how the big bang emerged and what came before it it is essential to unite Einstein's theory with quantum theory only if we obtain such a theory will we be able to answer the ultimate questions in cosmology like what is space what is time what is the universe and where did it come from

the most distant objects in the universe are 47 billion light years away making the size of the observable universe 94 billion light years across if you are wondering how can the observable universe be larger than the time it takes light to travel over the age of the universe the answer is because the universe has been expanding during this time and this causes very distant objects to be further away from us than their light travel time most scientists think the entirety of the universe extends Way Beyond the observable universe but is there anything beyond the entirety

of the universe is there anything beyond the universe probably not we suspect quite strongly that our universe could well be infinite in extent even now a bit of the universe if you just take our universe it certainly we're sure it exists far beyond the bit we can see so why would I say that well if you think about it the universe is that our bit at least has been around for 13.8 billion years that means that light has only had 13.8 billion years to travel from the bit that we can see to our eye so

we can only see as far as light as had time to travel but we think there's a lot beyond that because of measurements we've made of how the universe is curved and what the structure of the universe is so it undoubtedly extends beyond the little bubble that we can see how far it extends it's another great question we don't know but it could be infinite an extent taking into consideration the latest discoveries and measurements in physics we have attempted to answer the questions what was there before the Big Bang how big is our observable universe

and what lies beyond the bit we can see but are we forgetting something an important question that naturally arrives after we question the beginning of everything how will the universe end well the current best guess or best estimate is that it will carry on expanding forever and the reason I say that is because actually the universe is accelerating in its expansion which is a great mystery because before that Discovery we thought well gravity is always attractive and so it should be we've got all these galaxies in the universe and the universe has been expanding since

the big bang and so it should at least be slowing down and there's even a question as is there enough matter in it to slow it down so much that it stops and recollapses again but this new discovery that the universe is accelerating in its expansion suggests that it will continue to to accelerate unless some new physics appears that we don't understand and so it will just continue to expand forever thanks for watching did you like this video then show your support by subscribing ringing the bell and enabling notifications to never miss videos like this

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