Roger Penrose: Infinite Cycles of the Universe Punctuated by Big Bang Singularities

Duration: 12:52 2098 transcript words EN summary

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Roger Penrose introduces his theory of Conformal Cyclic Cosmology, a model describing an infinite series of universes punctuated by Big Bang singularities. He begins by noting that modern observations in the 21st century revealed the universe is undergoing exponential expansion driven by Einstein's cosmological constant—a term originally introduced to force a static universe but later vindicated as correct despite being retracted by Einstein himself, whom he called his "greatest blunder." As this expansion continues over eons, black holes will eventually consume most of matter in galaxy clusters. Eventually, even these massive objects will evaporate via Hawking radiation until the universe becomes devoid of mass and extremely cold, a state Penrose describes as emotionally boring but physically inevitable for photons that experience no passage of time or scale. Penrose argues that infinity should not be viewed merely as an abstract mathematical boundary but as a physical place accessible to massless particles like photons and gravitons. Drawing on the work of Dutch artist M.C. Escher, he explains how hyperbolic geometry can represent this infinite space where shapes remain constant while sizes scale infinitely up or down without changing form; this is known as conformal structure. In his view, because massive objects act as precise clocks due to their mass-energy equivalence ($E=mc^2$) and frequency relations ($E=h\nu$), they define a specific scale of space-time. However, in the remote future when all matter has evaporated, only this conformal structure remains, allowing the geometry of the distant past to be mapped onto the far future through a transformation that squashes infinity down into itself. The core mechanism of his theory posits that the extremely hot and dense conditions at the Big Bang are mathematically equivalent to the cold, empty state of the remote future via this conformal scaling. Essentially, the end of one universe's eon—where only massless radiation exists—is identical in structure to the beginning of the next Big Bang. This cyclical process implies that signals from previous universes can propagate through these singularities into subsequent ones. Specifically, Penrose highlights gravitational waves generated by black hole collisions as a primary carrier of information across these cosmic boundaries, suggesting that data from one eon could be detectable in the next after passing through the singularity. This cyclic framework also offers a novel perspective on the Fermi paradox regarding extraterrestrial intelligence and communication. While traditional speculation focuses on civilizations existing earlier than ours, Penrose suggests looking for signals generated by highly advanced future civilizations that have successfully solved global crises like climate change and survived to propagate messages across eons. These hypothetical transmissions would not come from predecessors but from successors who mastered their environment long enough to harness the conformal geometry of space-time itself. Consequently, if intelligent life exists in other cycles or manages to survive indefinitely within our own, we might eventually detect these signals once they traverse the infinite expanse between singularities, challenging current limitations on how far and when we should search for alien contact.

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but word is the conformal cyclic cosmology of yeah we're starting to talk about something before yes that's singular a big and I was just thinking of myself how boring this universe is going to be you've got this exponential expansion this was discovered early in the in this century aged my dear 21st century people discovered that these supernovae exploding stars showed that the universe is actually undergoing this exponential expansion so it's a self-similar expansion and it seems to be a feature of this term that Einstein introduced into his cosmology for the wrong reason he wanted a universe that was static he put this new term into his cosmology and to make it make sense it's called the cosmological constant and then when he got convinced that the universe had the Big Bang he retracted it complaining them this was his greatest blunder the trouble is it wasn't a blunder it was actually right very ironic and so the universe seems to be behaving with this cosmological constant okay so this universe is expanding and expanding what's going to happen in the future well it gets more and more boring from well what's the most interesting thing in the universe well as black holes the black holes more or less gulped down entire clusters of galaxies the class it'll swallow up most of our galaxy we will run into Andromeda galaxies black hole that black hole will swallow and they will get bigger and bigger and they'll basically swallow up the whole cluster of galaxies golf it all down pretty well or most of it maybe not all most of it okay that'll happen too there'll be just these black holes around pretty boring but still not as boring as it's going to get it's going to get more boring because these black holes you wait you wait and you wait and you wait and wait and unbelievable thing for time and Hawking's black hole evaporation starts to come in and the black holes you just it's a clarity Deus finally evaporate away each one goes somewhere disappears with a pop at the end what could be more boy that it was boring men now this is really boring there's nothing not even black holes it's colder and colder and colder and colder than ever this is very very boring now that's not science is it but it's it's emotional so I thought who's going to be bored by this universe not us we won't be around it'll be mostly photons running around and what the photons do they don't get bored because it's a part of relativity you see it's not really that they don't experience anything that's not the point photons get right out to infinity without experience anytime it's the way for where your relativity works and this was part of what I used to do in my old days when I was looking gravitational radiation and how things behaves infinity infinity is just like another place you can squash it down as long as you don't have any mass in the world infinity is just another place the photons get there the gravitons get there what do they get they run to infinity they say well now I'm here what there's something on the other side is there the usual view it's just a mathematical notion there's nothing on the other side that's just the boundary of it a nice example is this beautiful series of pictures by the Dutch artist MC Escher you may know them the ones called circle and it's a very famous one with the angels and the devils and you can see them crowding and crowding and crowding up to the edge now the kind of geometry that these angels and devils and habits that's their infinity but from our perspective infinity is just a crime as a place okay there's a clause and the in just the word you're saying infinity is just a place oh I have for the most part infinity sort of even just going back yeah infinity is a mathematical concept I think this is what I think there's an actual physical manifestation in which way does infinity ever manifests itself in our physical universe well it does in various places you see it's the thing that if you're not a mathematician you think oh I'm finished yeah I can't think about that mathematicians think about it finish me all the time they get used to the idea and they just play around with different kinds of infinities and it becomes no problem but yeah you just have to take my word for it now one of the things is you see you are taking Euclidian geometry well it just keeps on keeps on keeps on going and it goes out to infinity now there are other kinds of geometry and this is a what's called hyperbolic geometries but like euclidean geometry is a little bit different it's like what aja was trying to describe in his angels and devils and he learned about this from coxeter and he think that a very nice thing I trying to represent this infinity to this kind of geometry so it's not quite York Lydian John which is a bit like it that the angels and the Devils inhabit and their infinity mind this nice transformation you squash the aver infinity down so you can draw it as this nice circle boundary to their universe now from our outside perspective we can see their infinity as this boundary now what I'm saying is that it's very like that the Infinity that we might experience like there's angels and devils in their world can be thought of as a boundary now I found this a very useful way of talking about radiation gravitational radiation and things like that it was a trick mathematical trick so no what I'm saying is that that mathematical trick becomes real that somehow the photons they need to go somewhere because for their from their perspective infinity it's just another place now this is a difficult idea to get your mind around so that's why cause one of the reasons because mom's just are finding a lot of trouble taking me seriously but to me it's not not such a wild idea what's on the other side of that infinity you have to think why am I allowed to think of this because photons don't have any mass and we in physics have beautiful ways of measuring time there are incredibly precise clocks atomic and nuclear clocks unbelievably precise why they be so precise because of the two most famous equations of 20th century physics one of them is Einsteins e equals mc-squared what's that tell us energy and mass our equivalent the other one is even older than that still 20th century only just max planck e equals H nu nu is a frequency H is a constant again Lexie E is energy energy and frequency are equivalent put the two together energy and mass equivalent Einstein and in frequency equivalent Max Planck put the D together mass and frequency are equivalent absolutely basic physical principle if you have a massive entity a massive particle it is a clock with a very very precise frequency it's not you can't directly use it you have to scale it down so your atomic and nuclear clocks but that's the basic principle you scale it down to something you can actually perceive but it's the same principle if you have mass you have beautiful clocks but the other side of that coin is if you don't have mass you don't have clocks if you don't have clocks you don't have rulers you don't have scale so you don't have space and time you don't have a measure of the scale of space and all scale you have is if you do have the structure that what's called the conformal structure you see it's what the angels levels have if you look at the eye of the devil no matter how close to the boundary it is it has the same shape but it has a different size so you can scale up and you can scale down but you mustn't change the shape so it's basically the same idea but applied to space-time now in the very remote future you have things which don't measure the scale but the shape if you like is still there now that's in the remote future now I'm going to do the exact opposite now I'm going to go way back into the Big Bang now as you get there things get hotter and hotter denser and denser what's the universe dominated by particles moving around almost with the speed of light when they get almost with the speed of light ok they begin to lose the mass to therefore a completely opposite reason they lose the sense of scale as well so my crazy idea is the Big Bang and a remote future they seem completely different one is extremely dense extremely hot the others very very rarefied and very very cold but if you squash one down by this conformal scaling you get the other so although they look and feel very different they're really almost the same the remote future on the other side and claiming is that one of the photons go they go into the next Big Bang you've got to get your mind around that crazy idea taking a step on the other side of the place that is infinity ok but I'm saying the other side of our Big Bang now I'm going back into the Big Bang that was the remote future of a previously on previously on and what I'm saying is that previously on there are signals coming through to us which we can see and which we do see and these are both signals the two main signals are to do with black holes one of them is the collisions between black holes and as they spiral into each other they release a lot of energy in the form of gravitational waves those gravitational waves get through in a certain form into the next DeYoung that's fascinating that there's some I mean maybe I'm maybe you can correct me if I'm wrong but that means that some information can travel yes from another eon exactly that that is fascinating I mean I've seen somewhere described sort of the discussion of the Fermi paradox you know that if there's intelligent life yes being you know communication me immediately takes you there so we have a paper I have my my colleague waha Gossage on who I work with this on these ideas for a while we have a crazy paper on that yes so looking at the family paradox yes right so so if the universe is just cycling over and over and over punctuated by have the punctuated the singularity of the Big Bang and then intelligent or any kind of intelligent systems can communicate through for me on T on why haven't we heard anything from our alien friends because we don't know how to look that's fundamentally the reason is we I don't know you see it's it's speculation I mean the SETI program was a reasonable thing to do but speculation it's trying to say okay maybe not too far away with a civilization which got there first before us early enough that they could send our signals but how far away would you need to go before I mean I don't know we with so little knowledge about that we haven't seen any signals yet but it's worth looking it's worth looking what I'm trying to say here's another possible place we might look now you're not looking at civilizations which got there first you're looking at those civilizations which were so successful probably a lot more successful than we're likely to be by the looks of things which knew how to handle their own global warming or whatever it is and to get through it all and to live to a ripe old age in the sense of a civilization to the extent that they could harness signals that they could propagate through for some reason of their own desires whatever we wouldn't know to to other civilizations which might be able to pick up the signals but what kind of signals would there be I have a foggiest you