Roger Penrose: Infinite Cycles of the Universe Punctuated by Big Bang Singularities
Chapters
0:0 Intro3:20 MC Escher Circle
3:48 Infinity
6:5 Clocks
7:45 Conformal Structure
00:00:00.000 | - But where does the conformal cyclic cosmology of starting to talk about something before
00:00:07.680 | that singularity?
00:00:08.680 | - Yes, well I began, I was just thinking to myself, how boring this universe is going
00:00:14.560 | to be.
00:00:15.560 | You've got this exponential expansion, this was discovered early in this century, 21st
00:00:23.560 | century, people discovered that these supernova exploding stars showed that the universe is
00:00:31.040 | actually undergoing this exponential expansion.
00:00:35.540 | So it's a self-similar expansion.
00:00:38.880 | And it seems to be a feature of this term that Einstein introduced into his cosmology
00:00:44.980 | for the wrong reason.
00:00:46.600 | He wanted a universe that was static, he put this new term into his cosmology to make it
00:00:51.840 | make sense, it's called the cosmological constant.
00:00:54.680 | And then when he got convinced that the universe had a big bang, he retracted it, complaining
00:00:59.320 | that this was his greatest blunder.
00:01:01.320 | The trouble is it wasn't a blunder, it was actually right.
00:01:04.840 | Very ironic.
00:01:06.000 | And so the universe seems to be behaving with this cosmological constant.
00:01:10.040 | Okay, so this universe is expanding and expanding, what's going to happen in the future?
00:01:14.520 | Well, it gets more and more boring for a while.
00:01:16.920 | What's the most interesting thing in the universe?
00:01:18.600 | Well, there's black holes.
00:01:19.860 | The black holes more or less gulp down entire clusters of galaxies.
00:01:25.120 | It'll swallow up most of our galaxy, we will run into our Andromeda galaxy's black hole,
00:01:29.520 | that black hole will swallow our one, they'll get bigger and bigger, and they'll basically
00:01:33.740 | swallow up the whole cluster of galaxies, gulp it all down.
00:01:38.160 | Pretty well all, most of it, maybe not all, most of it.
00:01:41.840 | Okay, and then that'll happen to, there'll be just these black holes around, pretty boring,
00:01:45.460 | but still not as boring as it's going to get.
00:01:47.600 | It's going to get more boring because these black holes, you wait, you wait, and you wait,
00:01:50.960 | and you wait, and you wait, an unbelievable length of time, and Hawking's black hole evaporation
00:01:56.840 | starts to come in.
00:01:57.840 | And the black holes, you just, it's incredibly tedious, finally evaporate away.
00:02:04.400 | Each one goes away, disappears with a pop at the end.
00:02:07.720 | What could be more boring?
00:02:08.940 | It was boring then, now this is really boring.
00:02:11.840 | There's nothing, not even black holes.
00:02:14.840 | This gets colder and colder and colder and colder, and I thought, this is very, very
00:02:19.240 | boring.
00:02:20.240 | Now that's not science, is it?
00:02:22.560 | But it's emotional.
00:02:23.560 | So I thought, who's going to be bored by this universe?
00:02:27.680 | Not us, we won't be around.
00:02:29.000 | It'll be mostly photons running around.
00:02:32.180 | And what the photons do, they don't get bored because it's part of relativity, you see.
00:02:36.760 | It's not really that they don't experience anything, that's not the point.
00:02:41.040 | Photons get right out to infinity without experience any time.
00:02:46.640 | It's the way relativity works.
00:02:49.080 | And this was part of what I used to do in my old days when I was looking at gravitational
00:02:52.480 | radiation and how things behaved in infinity.
00:02:55.920 | Infinity is just like another place.
00:02:58.100 | You can squash it down, as long as you don't have any mass in the world, infinity is just
00:03:03.280 | another place.
00:03:04.500 | The photons get there, the gravitons get there.
00:03:07.800 | What do they get?
00:03:08.800 | They run to infinity.
00:03:09.800 | And they say, "Well, now I'm here, what do I do?
00:03:12.360 | There's something on the other side, is there?"
00:03:14.680 | The usual view is just a mathematical notion.
00:03:16.600 | There's nothing on the other side, that's just the boundary of it.
00:03:19.680 | A nice example is this beautiful series of pictures by the Dutch artist M.C.
00:03:24.280 | Escher.
00:03:25.280 | You may know them, the ones called Circle Limits.
00:03:27.200 | They're a very famous one with the angels and the devils.
00:03:30.520 | And you can see them crowding and crowding and crowding up to the edge.
00:03:34.040 | Now the kind of geometry that these angels and devils inhabit, that's their infinity.
00:03:40.440 | But from our perspective, infinity is just a place.
00:03:44.040 | Okay, there is-
00:03:45.040 | - I'm sorry, can you just take a brief pause?
00:03:48.040 | - Yes.
00:03:49.040 | - In just the words you're saying, infinity is just a place.
00:03:52.080 | So for the most part, infinity, sort of even just going back, infinity is a mathematical
00:03:58.220 | concept.
00:03:59.220 | - I think this is one of the-
00:04:00.220 | - But there's an actual physical manifest, in which way does infinity ever manifest itself
00:04:06.300 | in our physical universe?
00:04:07.700 | - Well, it does in various places.
00:04:09.780 | You see, it's a thing that if you're not a mathematician, you think, "Oh, infinity, I
00:04:13.340 | can't think about that."
00:04:14.340 | Mathematicians think about infinity all the time.
00:04:16.660 | They get used to the idea and they just play around with different kinds of infinities
00:04:20.060 | and it becomes no problem.
00:04:22.220 | But you just have to take my word for it.
00:04:25.460 | One of the things is, you see, you take a Euclidean geometry.
00:04:28.300 | Well, it just keeps on, keeps on, keeps on going and it goes out to infinity.
00:04:32.660 | Now there's other kinds of geometry and this is what's called hyperbolic geometry.
00:04:37.260 | It's a bit like Euclidean geometry, it's a little bit different.
00:04:40.260 | It's like what Escher was trying to describe in his "Angels and Devils."
00:04:45.380 | And he learned about this from Coxeter and he think that's a very nice thing.
00:04:50.700 | I try and represent this infinity to this kind of geometry.
00:04:54.220 | So it's not quite Euclidean geometry, it's a bit like it, that the angels and the devils
00:04:58.420 | inhabit.
00:04:59.420 | And their infinity, by this nice transformation, you squash their infinity down so you can
00:05:06.060 | draw it as this nice circle boundary to their universe.
00:05:11.220 | Now from our outside perspective, we can see their infinity as this boundary.
00:05:17.900 | Now what I'm saying is that it's very like that.
00:05:21.100 | The infinity that we might experience like those angels and devils in their world can
00:05:27.180 | be thought of as a boundary.
00:05:29.940 | Now I found this a very useful way of talking about radiation, gravitational radiation and
00:05:35.980 | things like that.
00:05:37.900 | It was a trick, a mathematical trick.
00:05:40.600 | So now what I'm saying is that that mathematical trick becomes real.
00:05:45.480 | That somehow the photons, they need to go somewhere because from their perspective,
00:05:53.560 | infinity is just another place.
00:05:56.200 | Now this is a difficult idea to get your mind around.
00:05:58.680 | So that's one of the reasons cosmologists are finding a lot of trouble taking me seriously.
00:06:05.200 | But to me it's not such a wild idea.
00:06:08.000 | What's on the other side of that infinity?
00:06:10.120 | You have to think, why am I allowed to think of this?
00:06:13.640 | Because photons don't have any mass.
00:06:17.020 | And we in physics have beautiful ways of measuring time.
00:06:21.600 | There are incredibly precise clocks, atomic and nuclear clocks, unbelievably precise.
00:06:27.620 | Why are they so precise?
00:06:29.840 | Because of the two most famous equations of 20th century physics.
00:06:34.860 | One of them is Einstein's E equals MC squared.
00:06:38.060 | What's that tell us?
00:06:39.400 | Energy and mass are equivalent.
00:06:42.880 | The other one is even older than that, still 20th century, only just.
00:06:46.520 | Max Planck E equals h nu.
00:06:50.720 | Nu is a frequency, h is a constant again like c, E is energy.
00:06:56.320 | Energy and frequency are equivalent.
00:06:59.600 | Put the two together, energy and mass are equivalent, Einstein.
00:07:03.160 | Energy and frequency are equivalent, Max Planck.
00:07:05.320 | Put the two together, mass and frequency are equivalent.
00:07:10.000 | Absolutely basic physical principle.
00:07:12.120 | If you have a massive entity, a massive particle, it is a clock with a very, very precise frequency.
00:07:21.480 | It's not, you can't directly use it, you have to scale it down.
00:07:24.160 | So your atomic and nuclear clocks, but that's the basic principle.
00:07:27.160 | You scale it down to something you can actually perceive.
00:07:30.240 | But it's the same principle.
00:07:31.880 | If you have mass, you have beautiful clocks.
00:07:35.920 | But the other side of that coin is, if you don't have mass, you don't have clocks.
00:07:42.840 | If you don't have clocks, you don't have rulers, you don't have scale.
00:07:48.200 | So you don't have space and time.
00:07:49.440 | You don't have a measure of the scale of space and time.
00:07:54.560 | You do have the structure, what's called the conformal structure.
00:07:58.840 | You see, it's what the angels and devils have.
00:08:00.760 | If you look at the eye of the devil, no matter how close to the boundary it is, it has the
00:08:05.240 | same shape, but it has a different size.
00:08:08.880 | So you can scale up and you can scale down, but you mustn't change the shape.
00:08:14.480 | So it's basically the same idea, but applied to space-time now.
00:08:18.840 | In the very remote future, you have things which don't measure the scale, but the shape,
00:08:24.320 | if you like, is still there.
00:08:26.520 | Now that's in the remote future.
00:08:28.040 | Now I'm going to do the exact opposite.
00:08:30.040 | Now I'm going to go way back into the Big Bang.
00:08:32.720 | Now as you get there, things get hotter and hotter, denser and denser.
00:08:38.840 | What's the universe dominated by?
00:08:41.440 | Particles moving around almost with the speed of light.
00:08:44.760 | When they get almost with the speed of light, okay, they begin to lose the mass too.
00:08:50.000 | For a completely opposite reason, they lose the sense of scale as well.
00:08:54.920 | So my crazy idea is the Big Bang and a remote future, they seem completely different.
00:09:01.540 | One is extremely dense, extremely hot.
00:09:04.100 | The other is very, very rarefied and very, very cold.
00:09:07.800 | But if you squash one down by this conformal scaling, you get the other.
00:09:12.400 | So although they look and feel very different, they're really almost the same.
00:09:18.420 | The remote future on the other side, I'm claiming is that, where do the photons go?
00:09:23.560 | They go into the next Big Bang.
00:09:26.720 | You've got to get your mind around that crazy idea.
00:09:29.400 | Taking a step on the other side of the place that is infinity.
00:09:32.880 | Okay, but...
00:09:33.880 | So I'm saying the other side of our Big Bang, now I'm going back into the Big Bang.
00:09:38.680 | Back, backwards.
00:09:39.680 | There was the remote future of a previous eon.
00:09:42.200 | Previous eon.
00:09:43.200 | And what I'm saying is that previous eon, there are signals coming through to us which
00:09:48.340 | we can see and which we do see.
00:09:51.900 | And these are both signals, the two main signals are to do with black holes.
00:09:57.600 | One of them is the collisions between black holes.
00:10:01.200 | And as they spiral into each other, they release a lot of energy in the form of gravitational
00:10:06.120 | waves.
00:10:07.260 | Those gravitational waves get through in a certain form into the next eon.
00:10:12.320 | That's fascinating that there's some, I mean, maybe you can correct me if I'm wrong, but
00:10:17.240 | that means that some information can travel from another eon.
00:10:21.400 | Exactly.
00:10:22.400 | That is fascinating.
00:10:24.360 | I mean, I've seen somewhere described sort of the discussion of the Fermi Paradox, you
00:10:33.400 | know, that if there's intelligent life, communication immediately takes you there.
00:10:40.200 | So...
00:10:41.200 | We have a paper, my colleague Vaheguru, who I worked with on these ideas for a while,
00:10:47.820 | we have a crazy paper on that, yes.
00:10:49.760 | So looking at the Fermi Paradox, yes.
00:10:51.720 | Right, so if the universe is just cycling over and over and over, punctuated by the
00:10:58.960 | singularity of the Big Bang, and then intelligent, or any kind of intelligent systems can communicate
00:11:05.840 | through from eon to eon, why haven't we heard anything from our alien friends?
00:11:12.760 | Because we don't know how to look.
00:11:15.120 | That's fundamentally the reason.
00:11:16.120 | I don't know, you see, it's speculation.
00:11:19.120 | I mean, the SETI program is a reasonable thing to do, but still speculation.
00:11:25.000 | It's trying to say, okay, maybe not too far away was a civilization which got there first,
00:11:32.560 | before us, early enough that they could send us signals, but how far away would you need
00:11:37.880 | to go before...
00:11:38.880 | I mean, I don't know.
00:11:39.880 | We have so little knowledge about that.
00:11:42.520 | We haven't seen any signals yet, but it's worth looking.
00:11:44.960 | It's worth looking.
00:11:45.960 | And what I'm trying to say, here's another possible place where you might look.
00:11:50.600 | Now you're not looking at civilizations which got there first.
00:11:54.240 | You're looking at those civilizations which were so successful, probably a lot more successful
00:11:59.080 | than they were likely to be by the looks of things, which knew how to handle their own
00:12:05.240 | global warming or whatever it is, and to get through it all, and to live to a ripe old
00:12:10.720 | age in the sense of a civilization, to the extent that they could harness signals that
00:12:17.160 | they could propagate through, for some reason of their own desires, whatever we wouldn't
00:12:22.640 | know, to other civilizations which might be able to pick up the signals.
00:12:28.200 | But what kind of signals would they be?
00:12:29.840 | I haven't the foggiest.
00:12:30.920 | [laughs]
00:12:31.920 | [silence]
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