Full transcript
Intro
0:00Some advice for a future Nobel Prize
0:02winner.
0:02>> Oh, gosh.
0:04The trouble is when people ask me this
0:05sort of question, I say the most
0:07important thing that I find when I look
0:09back at my life and the great sort of
0:12good ideas I've had from time to time,
0:14the best thing to be is lucky.
0:18I couldn't share an office with anybody,
0:20but it happened to be with Engelbart.
0:22>> [music]
0:22>> And it was two things I learned from him
0:24that I happened to put together, and
0:26they were really important in later
0:27life.
In your Conformal cyclic cosmology theory, what kicks off and ends the chain of aeons?
0:35>> Hello. Uh thank you very much for this
0:36talk. My name is Daniel Hermel. Um I'm
0:39just wondering uh in your theory
0:42um what happens at what kicks off this
0:45chain of eons, and what ends this chain
0:48of eons, or is that the wrong question?
0:49>> No, it's good to say call it chain of
0:51eons, it's fine.
0:52Well, you see, there needn't be
0:54anything.
0:55Maybe it keeps on going forever.
0:58I don't know. I have no answer to that
0:59question. But it's perfectly reasonable
1:02within this picture to say this chain is
1:05just eternal.
1:06There is no beginning, there will be no
1:08end.
1:09>> What what's the what's the um how do you
1:12dodge We talked about Stephen's
1:14singularity theorem based on your
1:16singularity theorem earlier. What how
1:19does how is that dodged? What why does
1:21there not have to be a singularity in
1:23our past?
1:24>> Well, you see, the singularities
1:27that particular one, you see, is only
1:30You have to distinguish the ones in
1:31black holes.
1:33Because the singularities in black holes
1:35basically
1:38uh irrelevant in the sense that they're
1:40in the black holes.
1:42The black holes evaporate away. Okay,
1:45there might be a little tiny singularity
1:48when the black hole goes pop at the end.
1:51But that's so tiny. I mean, it all gets
1:53a bit of a pop, it might not be good to
1:55be too close to that pop. But
1:58But it's not
1:58>> It's quite a big pop, isn't it?
2:00>> Yes.
2:00Um
2:01well, depends on
2:03>> [laughter]
2:03>> what kind of scale you're using. It's
2:04been a nasty one to go off in this room,
2:06that's true.
2:07>> Yeah.
2:07>> But um
2:09but it's a pop on the sort of
2:11cosmic scale. Yeah.
2:12But um
2:14it's not important from this point of
2:16view. There is a different It's a
2:18interesting question.
2:20And it's not even clear they happen. You
2:22see, that does depend on the
2:23on the uh Hawking evaporation, which I
2:26do believe in. I think it's correct. But
2:29you could take a negative view to
2:31Hawking evaporation and say that it
2:32doesn't really happen.
2:34There's no direct evidence for it.
2:36It's just the theoretical evidence. I
2:38think the theory is pretty good. I think
2:40it does. I agree with Hawking that there
2:41should be that radiation. But it doesn't
2:44come in
2:45until Well, look, think about the
2:47the temperature. You see, there's a
2:49Hawking temperature to a black hole,
2:51which is ridiculously cold.
2:53The bigger the black hole, the colder is
2:56this ridiculous Hawking temperature.
2:59Okay, we're talking about black holes
3:00which are much bigger than any we've
3:02ever observed. I mean, already now
3:05most of the material in the universe is
3:07in black holes.
3:09They're pretty big, but they're trivial
3:11but compared with these things start
3:13swallowing each other up and the whole
3:15galac- galactic clusters form these huge
3:18black holes.
3:20And they sit around and they sit around
3:22and they sit around.
3:24And that Hawking temperature is
3:27ridiculously cold, much colder than the
3:29temperature in the universe. And it sits
3:31there and it waits and it waits and it
3:33waits until the temperature of the
3:36universe gets colder and colder and
3:38colder until it's colder than that
3:41ridiculously cold temperature of the
3:42black hole. And then it starts to
3:44radiate away and radiate away for
3:47something like 10 to the hundred years.
3:50Think of one followed a hundred zeros
3:54that number of years.
3:56More than that, actually, before this
3:58effect kicks in.
4:00Pretty long time.
4:02>> [laughter]
4:03>> But that is the argument that after that
4:05length of time, the Hawking evaporation
4:08takes it to black holes where and
4:09they're gone after that time.
4:11It doesn't make much difference whether
4:13that's right or wrong in my picture.
4:16I mean, it's just true. I wrote a paper
4:17with some Hungarian uh
4:20Polish, I should say, Polish colleagues
4:23where we talk about what we call Hawking
4:24points.
4:26And these are these little points coming
4:28through from the previous eon.
4:30And they're the spots.
4:32We call them Hawking points because they
4:33probably are the Hawking radiation. So
4:36late, but they're little tiny points.
4:39And then by the time you see them, they
4:40spread out to about
4:43Well, I'm forgetting if it's 4° or 8°
4:45across in the sky. So, it's a little
4:47little spot in the sky. Not all that
4:49small, actually.
4:51It's bigger than the full moon.
4:53>> So, another observable prediction in the
4:55cosmic microwave background.
4:56>> Oh, yeah, but they've been seen.
4:57>> Undoubtable feature.
4:57>> We've seen them.
4:59With a 99.84%
5:02confidence level.
5:03Nobody believes us, of course.
5:05>> [laughter]
5:06>> No, well, in particle physics, that's
5:08not good enough, is it? 99%
5:10>> [laughter]
5:10>> But in cosmology, that's pretty good.
5:14>> All right. We have another question.
5:16There's one right at the front here.
5:18I'm going to do that thing where I make
5:20I guess one at the front, one at the
5:21back, one at the front, one at the back,
5:22and you have to
5:24do a lot of exercise.
What triggers the next aeon?
5:26>> Um I was just wondering,
5:27um so
5:29what triggers the Big Bang when
5:32everything's
5:34photons just floating around and and
5:36gravitational waves? What actually
5:38triggers that?
5:39>> Well, the infinity, you see. That's
5:41right. I mean, it's a good question to
5:43ask, and people do ask that question.
5:45What is it that triggers the next eon
5:47Come on. Well, it's a good place to to
5:49trigger it because it's infinity. You
5:51see
5:53You see, I'm in I'm a bit biased here
5:56because a lot of what I used to do in
5:57cosmology and general relativity was
6:00applying a a nice little trick
6:03which was to talk about infinity
6:06from the conformal picture. You see, you
6:08can draw a nice picture of infinity and
6:10I used to draw these pictures. They're
6:11called tend to be called Penrose
6:13diagrams for some reason. But anyway, I
6:15draw these little pictures. Infinity,
6:17you can draw it. It's a nice place. It's
6:19a
6:20And it joins on to something else and it
6:22might be joining the future of somebody
6:23else's past infinity or something.
6:26But in these little pictures, it joins
6:28on to the Big Bang.
6:29And you can't say when it is. Well,
6:31yeah, it was infinity, but infinity
6:33isn't that far off really because
6:36you have to think of how do you you have
6:38a clock who's saying this is my clock
6:40say how long is infinity? Well, the
6:41clock
6:42it depends on mass because
6:45clocks depend on mass being there. If
6:47you didn't have any mass, you wouldn't
6:49have any clocks.
6:50So, if the mass sort of fades out
6:53you don't have any clocks.
6:55So, infinity isn't that far along.
6:57That's not so far off.
6:58I mean, it's a bit of a stupid thing to
7:00say, I agree. But
7:02But But it's it's the picture. You have
7:04to get used to it.
7:06And I have got used to it by playing
7:07around with these things such a long
7:09time that I don't think infinity is that
7:11far off, you see. Cuz you draw pictures
7:13and it's a good thing to talk about and
7:15I just as good a place as singularities
7:18really. Would another way of phrasing it
7:20be to say how does mass return? So, how
7:23do the clocks return? Yes, you do need
7:25the mass.
7:27The mass fades in a way. It has to come
7:30back. That's quite right.
7:32And that needs a good theory of mass and
7:35we don't have a good theory.
7:37You see
7:38there's not really a good theory.
7:42I think I used to have a slightly
7:44different argument for that than I do
7:45now.
7:47You see,
7:50I used to think that particle physics
7:52was important in this what I call the
7:54crossover from one eon to the next. And
7:57I wrote a book
7:58called Cycles of Time.
8:01And I was quite flattered because a lot
8:02of Chinese people wanted to buy Chinese
8:04translation of this book. I wouldn't
8:06going to say don't read it.
8:09What I should say is don't read any of
8:11the appendices. Read the book, that's
8:13fine, but don't read any of the
8:15appendices. They're all wrong.
8:19Well, not so much that they're all
8:20wrong, but they're all irrelevant.
8:23Because I tried to think in particle
8:25physics,
8:26how do you try to make the mass
8:28disappear? I'm just your question here.
8:30But my view is no, that's the wrong way
8:32of thinking about it. Particle physics
8:34doesn't come in
8:35until much later.
8:37But the crossover from one eon to the
8:39next is is driven
8:42by gravitational radiation. That is the
8:44main thing which gets through from one
8:46to the side to the other.
8:48There are certain other things which get
8:50through.
8:51Photons get through as long as they're
8:53big enough wavelength. So,
8:55magnetic fields get through.
8:58Broad enough
9:00electromagnetic photons, ordinary light
9:03wouldn't. They would get scattered cuz
9:04when they get to the other side, they
9:06the the there's so much
9:08temperature, so enormous that they just
9:10scatter all over the place. They don't
9:12but the energy will get through.
9:14The gravitational waves get through.
9:17The general energy
9:19of a of a galactic cluster as it makes a
9:22little point and comes through. Then
9:23what we see this points,
9:25and I say that with my Polish
9:27colleagues,
9:29and we have a paper on this which people
9:31don't seem to pay much attention to.
9:33>> [laughter]
9:35>> Uh
9:36what what do we go right to the back for
9:38I was [laughter] you went to the back
9:40yeah. So someone right in the back
9:41corner cuz back corners never get a
9:43question, do they?
Do you believe in the multiverse?
9:45>> Can you hear me? Do you believe in the
9:47multiverse?
9:49>> I suppose that you might be which one is
9:51>> It's a good It's a good question. If I
9:53can remember what the multiverse is. You
9:55see the multiverse is that you got lots
9:56of different universes sitting around.
9:58And I think people like it because they
10:00want might say in some of them you got
10:02different constants of nature. And our
10:04particular one has certain values for
10:06the constants of nature. I mean very
10:08fundamental things like
10:10Well, I won't say what they're like, but
10:11they're a particular numbers which are a
10:13bit mysterious. Dirac points out these
10:15things are in his early
10:17stages of this discussion.
10:19And yeah, there's some very puzzles
10:21about where these numbers come from. You
10:22might say there are different universes
10:24which have different numbers. I don't
10:25know about that.
10:27Is the multiverse where you say there
10:28are all these different sort of parallel
10:30universes sitting around like this?
10:32That's not my picture. I don't know
10:34whether they're around or not. I don't
10:36like them very much. I prefer them this
10:39way rather than that way if you like.
10:41When I say this way, I mean in the
10:42temporal direction
10:44they keep on going. In the spatial
10:47direction, no, I don't see why you need
10:49other ones.
10:50My tentative view, and this is just
10:52speculation, I don't really know,
10:54there really is probably a good theory
10:57for why the numbers have to be why they
10:59are. And that there is some deep piece
11:02of mathematics hiding there which we
11:04don't know yet. Which tells us why these
11:07strange numbers that we find in physics
11:09have to have the values they have.
11:11>> So that would be the weakness of
11:12gravity.
11:13>> That's one of them. Yes. To say why do
11:15we have such a small
11:17See, gravity is weak when you're talking
11:19about small things and you're putting
11:20power, but when you have big things it
11:22dominates.
11:24And it's not just gravity, it's that
11:25other part. It's the lambda. It's the
11:28thing that people
11:29the dark people call dark energy.
11:31Dreadful term. But they call it dark
11:33energy. I just call it the cosmological
11:36constant. I mean, that's the term in
11:37Einstein.
11:38>> Okay, we've got time for one more
11:39question. Yeah, just one more one more
11:41one right in the middle. Why don't we do
11:43one right in the middle cuz I haven't
11:44done anything in the middle.
11:46Yeah, and
11:47>> Someone in the gallery stood in the
11:48middle, no?
11:51>> Who else could possibly be coming on?
11:54>> [laughter]
11:58>> Yeah.
11:59>> [laughter]
What was the most important thing that you learnt in physics?
12:03>> Uh I I'm a student and I just wanted to
12:06ask like
12:07um what was the most important thing you
12:10learned in physics that helped you gain
12:14the Nobel Prize?
12:16>> [laughter]
12:18>> Some advice for a future Nobel Prize
12:20winner.
12:20>> Oh gosh.
12:22The trouble is like people ask me this
12:23sort of question. I say, the most
12:25important thing that I find when I look
12:27back in my life with the great sort of
12:30good ideas from time the best thing to
12:33be is lucky.
12:35It's not much use to tell people that be
12:38lucky. That doesn't help.
12:40But I realized that a lot of things
12:41which were very important and came
12:43together because of things which I'd
12:44learned at different times in my stages.
12:47I shared an office with Engelbert
12:49Schucking and I learned various things
12:51from him. He was a great figure. He He
12:53knew uh
12:55He was a very
12:56important role in my life cuz he knew
12:58everything. That was important that He
13:00knew everything and everybody. He was
13:02also quite original which was unusual.
13:04People who know everything and everybody
13:06don't usually do original things, but he
13:08was good in that respect. His original
13:10ideas weren't all that great, I have to
13:11say.
13:13But he was a great person to have shared
13:15an office with.
13:16I could have shared an office with
13:17anybody, but it happened to be with
13:19Engelbert.
13:20And it was two things I learned from his
13:23that I happened to put together and they
13:24were really important in later life. I
13:27wouldn't have known that otherwise if I
13:28hadn't shared this often
13:30office with Engelbart.
13:32How do I tell people to share their
13:34office with the right person?
13:36That's not much of a piece of advice,
13:38isn't it?
13:39I think that perhaps is a important role
13:41here is not is to be
13:44respectful. You see, you have to be deep
13:47and broad at the same time.
13:50In your specialist area, you have to go
13:52deep. So, you have to
13:54learn a lot about what your particular
13:56area is and learn what's going on, what
13:58other people have been doing, and go
14:00deep into that. But, at the same time,
14:03keep an eye on the breadth of it. So, I
14:05like to think of this sort of funnel
14:07that goes out like this.
14:08So, you keep your eye on other topics
14:12and learn don't be
14:14too single-minded.
14:16Be
14:19Keep keep keep an eye open on what's
14:21going on outside your particular topic
14:23as well as being deep at the same time.
14:25It's difficult to do, but
14:27that's perhaps the best advice I can
14:28give.
14:30>> I think that's a a wonderful place to
14:32finish. So, please thank Roger Penrose.
14:35>> [applause]
14:39[applause]