Alan Guth - How Vast is the Cosmos?

Allen you have written down a number that has been the most emotionally effective number that has I have ever seen in my life you have said that the observable universe what we can see today which is if you look out you see about 13.7 billion light years and if you understand the expansion of the universe the whole universe diameter may have 40 billion light years as big as that is but all of that if you compare it to the minimum that all reality is that all reality is ten to the 23rd power bigger than what we see in our observable universe that's that's a hundred billion trillion times bigger than what we see it's astonishing yeah one of the things that one finds in cosmology that hits one right at the very beginning is that the universe is just plain unbelievably big even the observable universe which you've sort of treated this trivial is an incredibly big every galaxy has on the average maybe a hundred billion stars and then there are a hundred billion galaxies in the visible part of the universe but as you're quoting me if a theory called inflation is correct the observable universe is really only a tiny speck in a much bigger reality this idea called inflation is a twist on the Big Bang Theory and it proposes that there was a period of exponential expansion in the early part of the universe and by exponential expansion and what of course we mean is that there's a certain time in which the universe doubled in size and then if one weights the same amount of time it doubles again same amount of time it doubles again and so on the successive be doubling and that leads to an unbelievably fast expansion it surprises people how that works you you tell this story of chess in ancient India to explain how doubling the power of doubling it how does that work yeah well I actually took that story from from George gamma who used it the story is that a king of India wanted to reward somebody for inventing game of chess and ask the person what he would like for his reward so the person was fairly clever mathematically and said well why don't we take a chess board and all I would like is maybe one grain of rice on the first square - on the second for on the third and just keep doubling it and the King thought no that's trivial don't you want any more than back now that would be fine but then when you do that it turns out that the last square which has two to the 63 power grains of rice is far more rice than exists in all of India compared to nine times 10 to the 18th 9 quintillion grains of rice + completely beyond what was possible so this is the enormous power of doubling that that is really beyond our initial intuition that's right now an enormous power in inflation I think you said you have a minimum of a hundredfold in a very short period of time well within the first microsecond of the time of the universe that's correct that you need at least about a hundred doubling times of inflation to make the theory work in this number 10 to the 23 comes from saying we don't really know how much inflation there was there was at least this much let's guess that there was maybe twice that length of time why not and that's all the exponential expansion for this twice the minimum when you gives you a hundred extra doublings and 100 extra doublings is about a factor of 10 to the 23 larger than the size of what we say Wow I mean that that is an incredible an incredible number that that is and as you said I didn't mean to trivialize the current universe but I mean how can you not in the in the light of that that enormity and and an inflation took place in an extremely small time period that's right that's right we do not know for sure what the time scale and energy scale inflation really was but a very plausible guess is that it happened at the energy scale of what particle physicists call grand unified theories and if that's true then this doubling time was only about 10 to the minus 37 seconds it's a decimal point 3601 at the very end an unbelievably small number and then and then if you needed about 100 of them to say then you were finished but before 10 to the minus 35 second that's correct a lot of people get that arithmetic hundred times 10 to the minus 37 yes that's right only 10 to the minus 35 right you don't want to say it's just 100 100 times 37 multiple sets you need 100 in your and you're still at minus 35 so yeah it's enormous so let's now reflect on the scope of reality what is this what does this tell us if if there's so much reality beyond what we see what what could that be right and maybe before we go on to that I should even emphasize that the number that we just gave the sort of the reasonable estimate for the minimum of the region that we're sort of part of if again if inflation is right it suggests that there may in fact be an infinite number of these what I call pocket universes so the real number might actually be infinite not even 10 to the 23 as far as what it means I think one of the sort of moral lessons of cosmology is that at least if if mass and volume are relevant then we are a totally insignificant part I mean we were the times for all this before all of this that's right that we really change but it makes it more emphatic it really drives the point home it's really does that mean that we are insignificant I don't think I think it means that we are significant to ourselves that we give life its significance you use the term pocket universe so what's the pocket how big is this pocket well the pocket would refer to basically the region we just talked about that would be at least as big as what we see and more likely something like 10 to the 20 something so it's not just our observable universes that's not the pocket yeah it's the pocket is much bigger incidence the pocket that underwent this inflation that's right and we're just limited by the speed of light of what part we could see exactly exactly I'm using the word pocket to mean a piece of space that inflated together yes right right and and and and the implication is is that if there's this pocket universe there may be other pocket universes of which we came from or which came or in some other way that there may be lots of others infinite is a possibility that's right that's right I think the bottom line here is that in essentially all theoretical models of this phenomenon called inflation once inflation starts it never really completely stops what happens is it stops in places and produces these pocket universes but in other places it's always still going on just in more and more pocket universes and that that sounds so shocking but IIIi think the way it works is something like that that the inflation shuts off but everything is expanding so fast at the part that hasn't sure off keeps getting bigger and energy gets added to it and and you never you never run out exactly right exactly right you're always running faster than the closure curves exactly exactly if I could repeat what you said a little bit differently the ending of inflation is itself an exponential process that is it has a half-life the stuff that's doing the inflation so if you wait for one half-life on average half of it will disappeared turned into normal matter and pocket universes but meanwhile while it's decaying it's continuing to undergo this exponential expansion which is in fact much much faster so that when you wait one half-life and half of it has decayed the half that remains is that vastly larger than what you started with and that just continues forever in these theoretical models and in the inflation process when it expands energy is is created in the process that's right energy does not impose any limitation here it's rather shocking for even most physicists to accept that that the total energy of our universe is actually consistent with being zero and if inflation is right it is if not exactly zero unbelievably close to zero and the reason is because the reason is because gravity makes a negative contribution to the total energy of the universe and as far as we can tell the negative energy of gravity cancels perfectly the positive energy of all the matter in the universe which enables inflation to to add energy cuz it's not really adding energy it's just adding it's adding the energy and mass which are the same but the gravitational energy balances it out so everybody's books are happy that's right that's right each new pocket universe that's created has a total energy of exactly zero so one doesn't need extra energy to produce more pocket universes how does the pocket universe which which is what expanded in the inflation that we're part of at least how does that articulate with the concept today of multiple universes and multiverse is that just one part of that or there is that the multiverse how does it work well I guess that's personal not fun are we flowing around that's right that's right I think from my point of view this is the multiverse although people do talk about other levels of multiverses based on slightly different hypotheses but this seems to be a fairly firm part of the inflationary picture and in turn the inflationary picture seems to do a very good job of describing what we actually observe it's a rather wild extrapolation to talk about these infinity of pocket universes and maybe it's all nonsense it's hard to know for sure but nonetheless when the theory works as well as it does to describe the observed part of the universe I think it certainly makes sense to at least explore the implications that the theory suggests for the part of the universe that you don't see and all of this enormity and there's no word in any human language that can describe it numbers can help you feel it but nothing can describe it all came from a miniscule amount of matter energy in the most early universe prior to inflation that's right inflation is not a theory of the ultimate beginning you're right that one has to start with a little bit of to start inflation going people have speculated about there is the ultimate origin but inflation is not bad but the starting fashion at a minimum one really only needs a very small amount of matter something that comes out to be on the order of a gram and then everything else is produced spontaneously once this process get started and that word everything else which you sort of kind of throw out there everything else is this enormity where our observable universe the hundred billion galaxies of a hundred billion stars or more in each one is is less than one over ten to the 23rd of what the theory says all reality is that's right that's right and and that even that 10 to the 23rd is really just our pocket universe if this bigger picture that I'm talking about is also correct there'd be an infinite number of these pocket universes

Channel: Closer To Truth

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Keywords: Alan Guth, Cosmos, Universe, Closer to Truth, infinity, immensity, space, Cosmology (Field Of Study), Physics (Field Of Study), education, university, college, knowledge, STEM

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Length: 12min 0sec (720 seconds)

Published: Mon Jul 14 2014