Brian Cox debunked the Big Bang! Wait, what?

what happened before the Big Bang I got this question on Twitter and thought well the answer is that we don't know now I'm quite fond of short videos but that's a little too short even for my taste then I saw that Brian Cox has supposedly debunked the big bang with a creation story and I thought he did what then I watched the clip that's narrated by Brian Cox and I think I know what happened there let me explain [Applause] [Music] observations tell us that the Universe expands if we use those observations and take the equations that Einstein gave us we can calculate what happened in the distant past since the universe expands in the past mattera must have been more concentrated indeed if we trace the equations back then the density of mattera just increases and increases until it's infinitely large this infinite density happens at a finite time of about 13.8 billion years and is what we usually refer to as the Big Bang mathematically this big bang is a singularity in several measurable quantities like the energy density of matter but also the curvature of SpaceTime the first relevant thing to note is that it doesn't mean there wasn't anything before the Big Bang it's just that if there was something before the Big Bang it isn't in any way connected to what happened after so we never know of it to see what I mean take a super simple example of a singularity that in the function 1 /x squared when X goes to zero it's not like there's no curve for X smaller than zero it's just that there's no connection between the two parts the same could be the case for The Big Bang Singularity there was something before it but it's not in any way connected to us so we'd never know that said most physicists don't think that The Singularity is even there to begin with that's because in all other cases where we have a singularity in a physically measurable quantity it just means that the theory breaks down and we need to use a better one a good example is hydrodynamics that describes how liquids behave surfaces of drops can have points with infinite curvature like when a drop of water pinches off a to that pinch off point is the singularity but of course if you look at the drop on the scale of a single atom there's nothing singular about it it's just that if we approximate all those atoms with a smooth fluid that those singularities appear they're a consequence of this approximation that's why physicists think the Big Bang Singularity just tells us that we need a better Theory we don't have that theory so the smart thing to do would be to just leave it at that but of course that's no fun so physicists have come up with a lot of specul ulations for what might have happened instead of a big bang Singularity and there's very little data in the way of their speculations the young galaxies that the web telescope sees were probably created a few hundred million years after the big bang the cosmic microwave background was created approximately 300,000 years after the big bang and we have no observations from earlier on physicists have used particle colliders to study what highly compressed matter does and we can use this data to extrapolate back to somewhat before the creation of the cosmic microwave background to around the time when the hick field condensed but this still doesn't get us anywhere near the Big Bang this is why in theoretical physics you find many alternative ideas for the beginning of the universe depending on how you change the equations because there's no data to tell those ideas apart and this brings me back to Brian Cox's supposed debunking of the Big Bang in this clip from the BBC he's clearly talking about the currently most popular theory for what happened before the Big Bang it's called Eternal inflation in Eternal inflation the creation of our universe is not singular so strictly speaking there isn't any bang according to this Theory our universe is created by a Quantum fluctuation in a field called the inflaton the inflaton creates this fluctuation and that creates a bubble which then rapidly inflates hence the name at some point the inflation stops and all the energy from the inflaton field is converted into matter all the matter around us is created only at that point when the inflaton field dumps its energy in the literature this event is usually referred to as reheating what happened with Brian Cox's explanation is that he made a sound as if the reheating is the big bang I mean listen to it yourself as inflation ended the ocean of energy was converted into matter and the Big Bang so basically he just used the word big bang for something completely different it's somewhat of a disease among science communicators that I've complained about before because it causes a lot of confusion but let me not go there again maybe more importantly even leaving aside that we don't know whether Eternal inflation is even correct it doesn't remove the Big Bang per se it just removes the Big Bang in our universe you see in Eternal inflation there are infinitely many of those Quantum fluctuations and each gives rise to a new universe this entire Multiverse of Eternal inflation however must also have had a beginning at finite time and then you can ask well what happened before that so Eternal inflation just moves the problem elsewhere and of course there are other ideas for the beginning of our universe besides Eternal inflation for example there's the idea of a big bounce in which there was an earlier phase of the universe which contracted mattera became very dense but not infinitely so and now it's expanding again if those bounces repeat it's called a cyclic Universe you can also just push the Big Bang all the way back to minus infinity and say that for half of infinity very little happened and then the universe suddenly started expanding it's not a very popular idea probably because the entire point is that it's infinitely lame or there is the hle Hawking no boundary proposal that says before the Big Bang there was no SpaceTime there was just a four dimensional space and then One Direction of that space turned to time these these ideas are all more or less compatible with observations because you can always make sure that the deviations from Einstein's equations are unmeasurably small this doesn't mean these ideas are wrong it's that we can't tell whether they're right or wrong so what happened before the Big Bang physicists have a lot of speculations but the short answer is that we don't know and since there's so little information left over from whatever happened we might never know so it's not like Brian Cox said something wrong it's just that communication is difficult which is why I always try to learn a few words in the local language when I'm traveling as I've mentioned before we're planning to go to Paris and I've been learning some French with Babble who've been sponsoring this video I've made some progress excuse but let me tell you something about Babel first it's one of 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Channel: Sabine Hossenfelder

Views: 628,069

Keywords: science without the gobbledygoook, hossenfelder, science humor, science news sabine, brian cox, big bang, brian cox big bang, brian cox big bang wrong, big bang theory, what is the big bang theory, big bang debunked, big bang wrong, cosmology, astrophysics, science news, physics, physics news, science short video knowledge, short science video

Id: B4I68xZ6dCc

Length: 9min 4sec (544 seconds)

Published: Mon Jan 29 2024