Lawrence Krauss : Freeman’s 90th

Lawrence Krauss gave a talk on cosmology at the celebration conference in honor of Freeman Dyson’s 90th birthday.

Let’s review the beginning of the transcript, which I have edited for brevity. Dr. Krauss begins with this quote from Orwell.

To see what is in front of one’s nose needs a constant struggle.

George Orwell

Krauss : “If you have fixed energy density cosmological constant then the universe will expand exponentially.

It is actually quite amusing that Orwell’s quote describes the giant miss of cosmologists so succinctly.

NPQG teaches that cosmology is dominated by galaxy local processes and that galaxies expand INTO one another. We can have eternal inflation and expansion and a flat steady state universe at the same time! On top of that, spacetime aether is made from the same point charges as standard model matter-energy, so think particle rain!

This renders the rest of Dr. Krauss’s talk to be nonsense, sad to say. However it is a good exemplar and summary of the general nonsense that cosmologists have wasted an incredible amount of effort thinking and theorizing about for decades. I’ll leave the rest of the transcript below as an artifact, but it is probably better to listen to the video since the transcription is not perfect.

Krauss : “Operationally that means that velocities d dot of any object will be proportionate the velocity will be proportional to the distance Hubble’s law but only in the case of a cosmological constant will that constant of proportionality remain a constant for all time and that means that if you have a distance D greater than some fixed distance that the recession velocity is greater than light which of course allowed in general relativity and because objects are in the in the exponentially expanding universe all objects are being carried further and further away from us if you wait long enough all objects will disappear and the future in a universe with a cosmological constant is miserable because eventually the rest of the universe will disappear before our eyes and in fact if you plug in the values for the in this obscure set of units for the energy density of empty space you’ll find out that the that the distance beyond which objects are receding faster in light is about 18 billion light years which means though the effects are already beginning to be observable so what will happen is of course objects won’t be seen to disappear as the universe expands exponentially redshifts will become exponentially large and if you take the region of our local supercluster which is perhaps the largest bound region in our universe and compare it to the distant scale where objects are moving away faster than the speed of light it’s about a factor of 5,000 and if you plug that in to an exponentially expanding universe you’ll find out that in a hundred and fifty billion years the redshift for all objects outside our local supercluster will exceed five thousand which means that all the visible light will have disappeared but of course as x-rays and ultraviolet light that will be redshifted in but the great thing about an exponential is it’s an exponential so you don’t have to wait much longer in two trillion years which is not very long certainly not compared to the times I’m going to talk about in a second because main-sequence stars will still be around in two trillion years and therefore you can imagine carbon-based life-forms in two trillion years and an observers and around those carbon-based life forms but in fact and that in two trillion years the redshift for all objects that’s on our local supercluster will see 10 to the 53 and that means even the highest energy gamma rays that we know of in the universe will be redshifted so that their wavelength is larger than the size of horizon and the rest of the universe will literally be invisible there will be no galaxies outside of our own to such observers and those observers will think they live in a universe that we thought we lived in a hundred years ago with a single galaxy surrounded by a dark eternal void with no evidence of expansion and in fact it’s already the objects are already that the objects that are already I’ve read bigger than a redshift of a few will we’ll never see their future it turns out and in fact if we’ve been smart enough to evolve five billion years earlier if the vacuum energy density over the total energy density is bigger than about point seven today which is about the remember it is then the imprison observable region the universe has already been shrinking since the universe was half its present age so if we devolve five billion years ago there would be galaxies we could see then that we can’t see now so the universe is gonna disappear.

We can never determine the future Einstein used to say that geometry was destiny because once when we when I grew up if you knew the geometry of the university knew the future which is why I wanted why went into cosmology I wanted to know the future cuz I wanted to figure out how to determine the geometry of the universe whether was open closed or flat but of course that’s completely irrelevant now geometry is irrelevant it doesn’t matter whether the universe is open closed or flat and in fact nothing short of an infinite number of measurements or a theory of everything could tell us the future because every anything is possible the point is if the as we’ve now discovered if the expansion rate is greater than zero when empty space dominates which it appears to do now then it will mean greater than zero forever whether the universe is open or closed it will go on expanding forever if the vacuum energy dominates while it’s expanding okay now if if the present observation is incorrect it’s let’s say for some reason it is you know all the observations of supernovae are wrong and the vacuum energy doesn’t dominate even if the universe is closed it may expand forever we if there’s no vacuum energy you might say well if the universe is closed then we know it where we collapse but we know that the we know something we know that um I meant to put the numbers in here we know that the Omega the universe is not closed by more than a few percent from president observations omegas one at best 1.05 or one point one and if you calculate if you get rid of the vacuum energy density and calculate when will a closed universe full of matter collapse if they if Omega is one point one today then the universe will expand by a factor of eleven before it begins to collapse but that means the energy density of matter at that point will be since it goes as one over the volume one one thousandth of its present energy density but that means there could be a vacuum energy density which is a thousand times smaller than anything we could measure now which could easily come to dominate so even if we measure universes closed and we measure no vacuum energy density today there’s no way we know there’s no vacuum energy density it’s a thousand times smaller that would stop the collapse of the universe but of course it the same thing is true if the universe is open because while we don’t know that there’s no vacuum energy density now we also don’t know that there isn’t some very small negative vacuum energy density in fact string theorists would like that and therefore once again we can’t show in any way even an arbitrarily small one one millionth of the current energy density as a mat if as a density of matter falls as the universe expands eventually a negative vacuum energy density must take over and the universe must free collapse so even if the observations are incorrect we don’t know if the universe is gonna expand forever or not and even if the observation is correct of course we don’t know that the universe will expand forever because we don’t know the source of the vacuum energy density maybe it’s just a scalar field density it’s going to go away it may look like a cosmological constant but many people it’s quite reasonable to assume it’s actually some stored energy in a metastable field so there’s no way we can determine the future without either living an infinite amount of time to know what the future is or a theory of everything which is which describes not just the current vacuum energy density but all possible vacuum energy densities along the lines of maybe what Henry was hoping for at some point so the future is miserable and we can’t determine the future unless we live forever and we’re not going to live forever I guess I I was filling in ok good now let me talk about the far future and this is where Freeman comes in because Freeman wrote an amazing paper in in 1979 this is a version of it this is the the Big Bang and then the big anticlimax and and and and all of you have probably read it or heard of it but I will make the claim which is different and this is where we he and I have been having a fun dialogue or we’re having a fun dialogue that life and my life I mean consciousness in a way that Freeman defined not some some spiritual person cannot persist forever in any eternally expanding universe okay and bottom line is that life without Freeman won’t be livable as well as I’ll describe

okay the challenge is the following it turns out there exists and this is quite remarkable there exists only a finite recoverable energy within the horizon for any any eternally expanding universe this is highly non-intuitive it Glenn stark when I sort of tried to work this out in 1999 Freeman that implicitly worked it out in his own head in his famous 1979 paper which I referred to somewhere in 1979 Freeman wrote a paper interviews in modern physics arguing asking the question in an eternal expanding universe could life exist forever and came up with the answer yes and I’ll summarize his arguments in a moment but part of their part of the surprise here is that you’d think in an eternally expanding universe if the longer you wait the more energy you could get and therefore that you’d have access to an infinite amount of energy but it turns out that’s it that’s not true because the energy density of accessible material decreases as the universe expands and it decreases faster than you can get it and so you always end up with a finite amount of time I’m finally I’m a matter this is one example let’s say you wanted to harvest planets and turn it into energy well the best way to parvis matter is to use gravity because it’s a long-range field but it turns out that structure formation stops in any university isn’t closed and therefore you can no longer use gravity clustering to pull things in and therefore even using gravity gives you access to only a finite amount of material now obviously in a universe dominated by cosmological constant this is clearly true because there’s a finite horizon but the same thing is true for any universe which is surprising and as I say we we tried to think of lots of different ways and Freeman didn’t even know it had worked out in his own head beforehand and he had in 1979 and then and then we thought redefining it and partly in response to her our paper I guess had come up with a solution if there’s only a finite amount of energy then any civilization can access even over an if amount of time what do you do and he and this is Freeman’s wonder he said well it’s very simple you live forever on a finite amount of energy that may not seem possible but he came up with a very Freeman like solution and and this is how he this is the the the gist of the 1979 paper reinterpreted in 1999 in a simpler way I think to assume that life intelligent life is consciousness and consciousness is nothing other than information processing okay and also assume that life is independent any specific metabolism ignore the death of the Sun or proton decay you could imagine electron positron fares forming life you could so get rid of any practical worries you might have of what life might be assume that life can be anything that’s around okay so be as optimistic as you possibly can then Freeman pointed out he would define what living forever meant define a subjective time which is a total number of thoughts that any civilization could have and the answer therefore was that a civilization could live forever if it gotta have an infinite number of thoughts and so he said how can you how can you have an infant number of thoughts well he’s point out that the free energy used to process information is proportional the amount of information I and also to t the system’s temperature and they defined a quantity called the quality of life which is the rate of processing information and he argued that for humans quality factors 10 to the 23 bits per second it’s the amount of information processed you need to process in order to say cogito ergo sum I think therefore I am and understand what that means so there’s some there’s some quality of life factor which determines when you’re conscious and and below that you’re not conscious we don’t know what the number is we know that my Mac is more conscious than the PC next to it but we know that it’s not yet conscious but there’s some value okay then the question can you process an infinite amount of information as you point out just said it can be can the total information process diverge namely the number of thoughts or the bits of information processed be infinite but the free energy be finite that’s a well-defined physics question part of the beauty of the way Freeman does things and there are two answers to that yes and no now his answer was quite simple so if you think of the free energy which is the temperature times the rate of processing of information and then and then the total number of thoughts should just be the rate of processing information integrate over time then you can see that the only way you can satisfy that F be finite and I not be finite is if life forms cool but as he pointed out the best you can do is cool in general as one over time and if the energy process goes as T to the fourth power then it turns out that the temperature goes down as t then minus one third power and he showed that F will converge and I will diverge if and only if Q of T goes like T to the N where n is some positive power but that means of course that as the temperature goes down Q goes to zero that’s what’s required but if fuel goes to zero life forms must become unconscious so a lesser man would have given up at this point but not Freeman so it appears that the only way for this to be the case is to lose consciousness but he came up with another solution which is particularly appropriate on his 90th birthday I think which is which is to hibernate almost academics are familiar with this solution if you if you if you said imagine that you have some constant rate of activity when you’re active but zero when you’re inactive then you can show that if the period of inactivity increases as the universe expands this is what I’m talking about academics getting older then it will work because if if the period of inactivity increases that turns out the fourth power of time then this quantity will converge the fraction of time your any civilization awake is an increasingly small fraction so a civilization you go to sleep you sleep for some time you wake up then you sleep for a longer time you wake up the fraction of time you’re awake is a smaller and smaller fraction of the age of the universe but the total number of thoughts will diverge brilliant so so this is the way that Freeman could have us live forever hibernate a wonderful beautiful solution in principle the question is is it possible and this is where we got into the discussion and as I say there are two answers to this question is it possible the first is no and that’s what Glenn and I argued and the other one is yes which is what Freeman that’s argued and I wanna I want it turns out remarkably what’s come down in this debate which was so interesting is the quite imagine all the question is life is intelligence quantum mechanical all of this comes down to that question and you might not have imagined it was the case and I want to explain to you how it is so we had this we started to discuss whether whether this was possible that systems could hibernate and Glenn and I would write Freeman and come up with and say no this is the reason why you can and then he’d come back with a smarter answer why it could and it was a lot of fun I’ll just give you a few examples so so we came up with some intermedia arguments thing well look if you want to wake up you gotta have an alarm clock but alarm clock has energy and therefore you have an infinite amount of energy that’s required to have an infant member wake up so we thought that was a pretty good one and we also said well you know as the universe becomes colder and less dense system living systems will not be in thermal equilibrium they’ll eventually stop interactively the background and their radiate the probability of radiating their way will be greater than zero and then of course we also said all alarm clocks will eventually fail and once they fail and then have this experience you sleep in in this case you you just leave forever and so we you know we gave these yeah I just want to give you an example of the beauty and brilliance that it’s how much fun it is to argue with Freeman so the first one standard alarm clocks were great advanced energy well Freeman said no no because all you have to do is is arrange an alarm clock that that’s this way you have these two masses you arrange them to be an orbit around a bigger mass and two collide now it turns out you just have to move them out a little bit to make them have a basically an exponentially longer period before they collide again and a little bit more so you don’t require an infinite amount of energy to have an infinite number of wake up’s so this was a beautiful classical alarm clock involving two masses around the things and okay but the problem is if you think about it there’s a quantum mechanical problem here so this was his this was his alarm clock you put masses in orbit and then they collide and then you reset the clock move them out a little bit and it’ll take a lot longer to collide again the problem of course is that to make them collide you have to when you get it out you have to know their momentum better and better and eventually quantum mechanics is going to kill you because the uncertainty principle tell you they get it wrong and they’ll miss so this gift this began to give us an idea that maybe as Riemann already argued quantum mechanics might be important and then we came up with an argument we thought was airtight for why life would end now the interesting first aspect is argument which you may even discuss later in this meeting is that one of the nice things which Fineman and others first argued about a lot is that in fact unlike what people have thought you can actually do reversible computations computations do not dissipate energy or entropy you can do a completely reversible computation a quantum computer as one example of such so that’s great the problem is however that what energy is erasing the registers and so erasing the registers cost KT and that means you could do the sit you could stare at your navel and go on for all eternity and have the same thought forever and if you want to call that eternal life it’s alright but if you want to have new thoughts you have to erase the registers and that takes that dissipates energy and therefore the new computation is done at a lower energy now the interesting thing is no finite size quantumatic chemical system has an infinite number of states accumulating above the ground state there’s always an energy gap and therefore if you take a civilization and consider it a large but finite quantum mechanical system and then you have it you and and you have a thought and then you erase the registers you doe down in the next korma state and then you erase the registers and after the next thought and the next saw next time but you always only have a finite number of states above the ground state and eventually you get the ground state no more thoughts end of story so we said look this is unimpeachable life if it’s quantum mechanical if thought think process thinking prosthetic want mechanical life must end and we said aha ok but Freeman is Freeman and among other things he’s also read a lot of science fiction and he read he read a famous story but the black cloud fred hoyle wrote a wonderful story which he introduced me to with you introduced me to which is a wonderful story about an astronomer who measures a cloud and it turns out the cloud is actually a life form now the point is how can you avoid the quantum-mechanical that the key question is is life quantum mechanical what does it mean to be quantum mechanical it me you are quantum mechanical when the available energies to you are comparable to the quantum spacing if the available energy is much bigger to you than the quant was facing you behaved classically so you could avoid the quantum mechanical limit if you had a system whose energy levels decreased faster than the need for for using energy and and he gave an example of the blob of in fact the black cloud and as he said you make life analog not digital so imagine that that you you embody a life-form in a cloud of gas and then he showed if the cloud is of size Allen and expands with the universe the temperature goes down like one over L and the phase space V and P go down like one over L to 1/2 and it turns out the information you can store in the classical motion of particles is n log L whereas the quantum information is n so classically if L increases in size that the amount of information you can store in the classical phase space of moving particles increases and he said aha so I can make a life-form that avoids the quantum mechanical limit what it does is it squeezes those energy levels down fast enough so that you’re always you’re the available energy is always bigger than the spacing of the quantum mechanical levels ok so this was the level of the debate and the system becomes more and more classical over time and therefore avoids the quantum mechanical limit and therefore this kind of life form could live forever and he defeated us but the question is will universe allow this and this is this is a debate we sort of lingered on and never quite resolved because in fact there’s lots of problems with this because this this system becomes more and more dilute and if it’s more and more dilute the different parts of the system have a harder time communicating with one another in fact electromagnetic radiation will in general the cross-section will go to zero and the system won’t be able to be coherent ok but the good news is that for the moment the universe has answered this question because we all agree including Freeman that if the universe has a vacuum energy density then we’re screwed because if the universe has a vacuum energy density eventually of course this system will go outside its own horizon because it will begin to expand exponentially so the so if the universe has a vacuum energy density it’s bad news ok now as I pointed out to you we don’t know for certain that that vacuum energy density will remain forever but if it is the case then life must end if it isn’t the case then we have to decide if that black cloud will work and we haven’t figured that at least I don’t know if Freeman has capitulated in that regard yet but if the universe has a dark energy and that dark energy remains constant then life and no civilization can have an infinite number of thoughts and it’s bad news now the question is will therefore as Freeman put it the future of life depends upon whether it’s analog or digital so you gotta get rid of of your iPods and go back to LPS in the long run because of what is amazing about this whole discussion and what I found so fun about it and it began with Freeman is that this we don’t have to know what life is you don’t even have to define the biology in a if quantum mechanics utterly governs a universe starved of energy consciousness will end for an eternally expanding universe and what I love about that is it’s physics not biology you didn’t have to define consciousness you didn’t have to define living systems or anything the quite the question is as he put it will life be analog or digital and the future of life that there is going to be life is analog but even analog life will die in a universe with a cosmological constant now I want to in the last few minutes point out another aspect that we followed up with this which is you know copy consciousness we don’t even know what it is so it’s all right to talk about quality factors but computation we know what that is a little bit more and even that’s pretty much so art does the same argument provide limits on computation and the answer is yes in a way that I’m amazed with so let’s consider that we live in a universe with a cosmological constant which is probably universe we live in then you can ask how much energy can you access in the universe for the cosmological constant and the way you do it is you sort of like the board from Star Trek you go out at the speed of light and you destroy stars and your being the energy back to you okay so you can you can do a calculation you can do some conformal time diagram where you go out of the speed of light and you keep beaming all the energy back to you at the source out until you get to the horizon okay and you could calculate how much energy you can get in such a universe by going out destroying things and beaming the energy back to you and you can do the calculation and it’s kind of interesting turns out if the universe is exactly flat with a cosmological constant the answer is this it becomes a little more complicated if it’s not exactly if the cosmological constant isn’t everything if there’s Matter density but the answer interestingly enough is that the total energy accessible to us in the entire future of the universe by going out and destroying every system we see and beaming its energy back it’s 3 times 10 to the 67 joules which happens to be about the total baryonic rest mass within today’s horizon ok so that’s that’s a limit on the total amount of energy we’ll ever be able to get in the future now interestingly however there’s a problem if you want to if you want to process information down a noisy Channel at finite temperature T then to do error correction everything else you have to dissipate energy KT log 2 and if there’s a cosmological constant then there’s a Hawking temperature to the universe so the minimum temperature below which you can’t cool things it’s a very low temperature now it’s about 10 to the minus 40 electron volts or some number but it’s not zero and therefore you can calculate how much information you can pump down noisy channels therefore how many computations you can do in a universe with a Hawking temperature and the number is quite interesting this is about 2 times 10 to the 120 now you can ask I live in Arizona now where an Intel is there and Gordon Moore is there and and and and and and and and you can ask if information processing systems improve by a factor of 2 in their computation ability and their speed over every 12 to 18 months how long will it be before you’ll process 2 to the 10 to the 120 bits it turns out to be not a cosmological time it’s 400 years and I find this remarkable because it means that in a finite time we will and any civilization would would utilize would do all the computations that are possible and I think this is interesting from a scientific fiction perspective because it means people when they talk about SETI often talk about civilizations that continue to improve exponentially over billions of years but if this is true then we may have only 400 years of exponential improvement on information processing capability and and and then we may have to just slow down so this is the first time I’ve seen where cosmology puts a a time limit or which is actually not cosmological in in in its amount and I think that that means that’s why I tell my students don’t waste calculations because we only have a finite number. now Freeman always looks on the bright side of life so it’s clear to me that if Freeman is right which is that there’s all there’s always hope the only hope is that the dark energy isn’t a cosmological constant and it probably won’t be.”

J Mark Morris : San Diego : California