Full transcript
Intro
0:00people often say well maybe with a
0:02sufficient technicality we could build a
0:04Schrodinger cat that was not what
0:06Schrodinger point was he was saying this
0:08is ridiculous you can't really have a
0:10cat which is dead and alive at the same
0:13[Music]
0:17time you suggested that human
0:19consciousness might in some way be the
0:21result of quantum effects could you
0:23perhaps tell us a bit about how you came
On quantum mechanics and consciousness
0:25to that view and how that view has
0:26developed over the years well the story
0:29is a bit long
0:31and involved in many ways I was when I
0:34was a graduate
0:35student in Cambridge after having done
0:38my undergraduate work in London
0:40University College I went to Cambridge
0:42and I was working on pure
0:44mathematics and I sort of thought well
0:46three years from my PhD is quite a long
0:48time I can work on other things which
0:51might interest me so I went to three
0:52courses which were nothing to do with
0:54what I should be doing one was of course
0:56by Bondi on general relativity which was
0:58very influential
1:00very influential on what I subsequently
1:02did other was of course by Paul der the
1:06great physicist which also was extremely
1:09influential in what I did later the
1:11third course was by a man called Steen
1:14who was a mathematical logician and I
1:16leared from his course about touring
1:19machines which gives a general concept
1:21to what you mean by a computation so I
1:24learned about that and then he
1:27described girdle's theorem I had been
1:30worrying a bit about girdle theorem well
1:32when I say girdle theorem there are two
1:34but you can um put them into one theorem
1:37basically it's one one statement which
1:38is the important thing um I'd heard
1:42about it but I didn't quite like the
1:44idea because it seemed to say there were
1:45things in mathematics you couldn't prove
1:47and I was a little bit worried by that
1:49anyway so I went to this course and what
1:52I learned was something very different
1:54and it's if you have a system of rules
1:58which you could use to prove some
2:00theorem and if those rules are such that
2:03you could put them on a
2:04computer and you and it can tell you you
2:08try this theorem and you see is it true
2:10or not you put
2:11it suggest that this set of rules that
2:14can be applied and the computer chugs
2:17through and says yes it's been correctly
2:19applied and therefore the thing is true
2:21that's sort of thing and you have to
2:24believe that the rules do give you truth
2:26that's part of the story I that's the
2:27point of them after all so you've looked
2:29at them each individually you said does
2:31that really do you believe that one yeah
2:32that's okay what about that one yep what
2:35about that uh oh yeah I see that's okay
2:38so that sort of thing yeah yeah yeah and
2:40that's the sort of rules you would use
2:42to prove these are all statements about
2:45infinite numbers of things mhm like if
2:47you add two even numbers you get another
2:49even number right that's a statement
2:51about about an infinite number of things
2:54yet you can prove it in a couple of
2:55steps and using these rules that would
2:57be very easy to prove okay what girdle
3:01does as Steen described and it's very
3:04clever how you can make a statement
3:07which when you look at how it's
3:09constructed it really can be interpreted
3:11as saying I am not provable by those
3:14rules right so then you say well okay
3:18maybe it's false in which case it is
3:21provable by the rules and since you've
3:23built up a trust that these rules really
3:25do only give you truths then you know
3:28it's it must actually be true that it's
3:30not provable by the rules and the
3:32statement is true yeah so this is a and
3:35it's a statement which is really about
3:37numbers ordinary numbers and it's a
3:40statement which you can see by virtue of
3:42your that's the thing that I found
3:44stunning by virtue of your belief that
3:46the rules only give you
3:48truth you can see that this is true
3:51nevertheless it cannot be proved using
3:53the rules right so it tells that there
3:55is these rules whatever they are cannot
3:58encapsulate
4:00one's entire way of proving things in
4:03mathematics I found that absolutely
4:05amazing because it seemed to me that our
4:09understanding transcends any kind of
4:11rules and well I won't go into the whole
4:14story because it's was complicated I
4:16wrote about this in the emperor new mind
4:18I had H numbers of complaints from
4:20various people I wrote about it again in
4:22my books Shadows of mine trying to
4:25indicate all these responses and things
4:26like that so I won't go into the details
4:28of that but it did strike me as rather
4:31remarkable that by our understanding of
4:33what the rules are saying enables us to
4:36transcend the
4:37rules and this struck me as completely
4:40amazing that somehow the understanding
4:42that one has Isn't following the rules
4:46there's something beyond that and this
4:49transcending of these rules is a feature
4:51of our understanding right it seems to
4:53me that whatever understanding is and I
4:55don't know what it is is some quality
4:58that we have which enables us to
5:01transcend any set of rules that you have
5:03for proving things in mathematics yeah
5:05and they're not enough yeah but you can
5:07see by understanding them you can go
5:09beyond them now what does understanding
5:12involve well it certainly involves
5:14Consciousness in the normal usage of the
5:16words yeah because one says you to
5:19understand you couldn't imagine
5:20something understanding a thing if it
5:21wasn't even aware of it yes so being
5:23aware of something is a necessary
5:25ingredient surely not the whole story
5:28because it doesn't say anything about
5:30the perception of the color blue for
5:31example yeah I mean people complain to
5:34me say well you're only talking about a
5:35very limited thing of course it is but
5:37the point is if what I'm saying has
5:39relevance to our understanding it may
5:42not be relevance to all features of
5:43understanding sure I'm quite happy with
5:45that but nevertheless it seems to
5:47indicate there's something outside
5:49computation in human understanding and
5:53then I start talking about Evolution how
5:54it can happen and what how this it's a
5:56feature of General understanding it's
5:58not a very specific thing that
6:00mathematicians
6:01involve you uh and you can present
6:05arguments in that direction too so then
6:07I began thinking okay well what kind of
6:09I I'm a physicalist so I believe what's
6:11going in in our heads is obeying the
6:15same laws of physics which is going on
6:16around us there's nothing something
6:18special injected into our heads which is
6:21gives us a quality which is beyond the
6:23laws of physics I'm I'm a physicalist I
6:25believe it's the same physics in here as
6:28Out There and Everywhere yeah maybe
6:30different parts of are are emphasized in
6:32different ways so I began to think about
6:35what are the laws of physics as we know
6:37them or knew them at the time I was
6:39thinking about this okay well Newtonian
6:41mechanics you can put that on a computer
6:44there's a little bit of a catch which I
6:45always worried about a little but I
6:47don't think it's the real answer the
6:49catch is that all these laws of physics
6:51depend on the Continuum so you're really
6:53talking
6:55about properties of real numbers ah
6:58right and real numbers are not things
7:00you quite put on the computer you put
7:02approximations to them now is there a
7:04catch in the fact that these are only
7:07approximations I don't think that's the
7:09answer but I'm prepared to admit that
7:11there's another route one might try to
7:13follow right okay I'm not following that
7:15route because I think the computers are
7:17impressive enough you can you can get
7:19approximation as close as you like and
7:22so I don't think that's the answer but
7:24I'm prepared
7:25to uh look at some suggestion which goes
7:28in the other Direction okay then I think
7:31about okay newtonium mechanics I think
7:33about Maxwell's electrodynamics y you
7:37put all those things on the computer I
7:38would think about Einstein's general
7:40relativity I knew that was pretty hard
7:42at the time it had got very far but
7:44nowadays y you can talk about ins
7:46spiraling black holes and you can it's
7:48really very very detailed what people do
7:50yeah yeah yeah so sure then what about
7:52quantum mechanics well Shing equation
7:55you can put that on a computer it has a
7:57problem with how many variables you have
7:59to it's sometimes people regard it as a
8:01difficult problem for a complicated
8:03system but it's not really fundamentally
8:05different so the Shing equation also but
8:09that's not the whole of quantum
8:10mechanics no quantum mechanics involves
8:12not just the evolution of the quantum
8:15State according to the sh equation or
8:17whatever you like to call it unitary
8:19Evolution it
8:20involves measurement and the measurement
8:24problem is violates Shing equation you
8:28evolve a state and it says if you made a
8:31measurement of such and such a type it
8:33would give you a probability of that and
8:34a probability of this if you evolve the
8:37measuring device as well as the system
8:39then you get a contradiction because it
8:42says that the answer of the measurement
8:43is a superposition of this and that
8:46tringo obviously worried about this with
8:48his cat I mean that's why he brought the
8:50cat into the discussion right really to
8:53show that there's something wrong here
8:55there's something in the theory I mean
8:58people often say well maybe with a
9:00sufficient technicality we could build a
9:02Schrodinger cat that was not what
9:04Schrodinger's point was he was saying
9:06this is ridiculous you can't really have
9:08a cat which is dead and alive at the
9:10same time yeah but it was a m
9:12illustration of a wider point right
9:14that's right so so Schrodinger I'm well
9:18in line with Schrodinger's viewpoint on
9:20this Einstein took a rather similar view
9:23in fact duraq did too even though he
9:25didn't he didn't enunciate that you have
9:27to see what his later he didn't say much
9:30about what he thought about quantum
9:32mechanics but he took a rather similar
9:33view you see quantum mechanics is
9:35incomplete right right because it
9:37doesn't explain the collapse of the wave
9:40function the shinger equation is a a
9:42smooth continuous evolution of the state
9:45but it's not what you get when you make
9:47a measurement yeah when you make a
9:49measurement which are sort of broadening
9:50the system a bit to include the
9:52measuring aerators and all that why
9:54doesn't it follow the Schrodinger
9:55equation and that worried Schrodinger
9:58very much MH
9:59[Music]
10:00and um it seems to me this is the is the
10:04gap that's not present in all the other
10:06theories see all the other theories
10:08right up to the point even including the
10:10Shing equation or the evolution unitary
10:12evolution in quantum mechanics they are
10:15all things you could put on a computer
10:17so where is there something that you
10:19couldn't maybe put on a computer and the
10:22argument I was making here is that it's
10:25in the collapse of the wave function
10:26right so there is some process and I'm
10:29not taking the view as many people did
10:32in the early days of quantum mechanics
10:34that it's the conscious Observer looking
10:36at the system and observing yeah yeah
10:39that's the sort of terminology which
10:40suggests that yeah observing the system
10:44no I don't believe that that you it
10:46doesn't really work when you think about
10:48it in detail I won't into that but but
10:50it certainly doesn't really work so I
10:54don't believe it's that however it's a
10:56different role for conscious almost the
10:58opposite that whatever Consciousness is
11:01depends upon what this currently
11:04unknown but we know something about it
11:08which is to do with seeing how general
11:11relativity relates to Quantum Mechanics
11:14right but it's the other way around it's
11:16not how you quantize general relativity
11:18which is what many of my colleagues try
11:20and do right it's the opposite how you
11:22graviti quantum mechanics you try to put
11:26the principle of equivalence these great
11:28principles of G
11:29into the theory and the Einstein way of
11:32resolving these principles of galile
11:35into a into an overall Theory and
11:38imposing that on quantum mechanics and
11:40you can see when you look at this that
11:41the arguments tell you that with
11:45certain mass
11:47displacements that the the superposition
11:50of it being one position or another has
11:52to go to one or the other in a certain
11:54time scale yeah and that time scale you
11:56can estimate yeah and so this I claim is
12:00what's going on in the brain ah and
12:03there and it where in the brain I had no
12:06idea I learned a bit of neurophysiology
12:09I just couldn't see where in the brain
12:10it could be doing it yeah I rather sort
12:12of Pete it off in my the emperor's new
12:14mind and without knowing the answer but
12:16then uh steuart hamov who was an
12:19anesthesiologist in in Tucson in Arizona
12:22yeah and he wrote to me and said more or
12:25less evidently you don't know about
12:26microtubules he didn't put it quite like
12:28that yeah but he said he suggested
12:32there's something I mean he was very
12:34interested in in in general
12:37anesthesia and he realized that it's not
12:39a chemistry question I mean how you turn
12:42it off is a root into what it is and
12:46what turns it off is not chemistry
12:48because you have many many substances
12:51completely unrelated chemically which
12:54are General anesthetics one of the most
12:56striking being Z Zenon which is an inert
12:58gas or more or less
13:00inert and so it's not chemical processes
13:03it's some physical process and well we
13:06develop these ideas together going off
13:09on different routes and trying to come
13:11back again all the time and uh
13:14formulating a scheme which is referred
13:16to as the orc o proposal yeah yeah yeah
13:19yeah orc means orchestrated it's not the
13:21o means objective reduction so the
13:24reduction means the collapse of the wave
13:27function objective means me it really is
13:29a physical process and then there are
13:32curious
13:33features about when it happens which is
13:37another whole story which is another
13:39question entirely yes it's got very
13:42interesting going back to experiments
13:44which I do describe in the emperor new
13:46man due to Benjamin libbit and there's
13:50some renewed interest in these things
13:52you've already mentioned for example
13:54that you were taught by dur yes who who
13:56are the who are the people that you
13:58enjoy just personally working with or
14:00being taught by the most it's comp well
14:03there's one character when it comes to
Personal idols and friends
14:06physics you see I was in Cambridge as a
14:09pure mathematician right right but the
14:12person I gained a lot of insights from
14:14it the physics was Dennis Sharma now
14:17Dennis Sharma was a good friend of my
14:19brothers my older brother Oliver who had
14:22worked in Cambridge doing graduate work
14:24there on many body systems um different
14:28area from what I worked in but I got to
14:31know Dennis through my brother Oliver
14:34and we rather hit it off Dennis and I
14:37particularly he was interested in
14:38cosmology and I'd listened to Fred
14:40Hall's radio talks and was puzzled by
14:42them right right and this led to and
14:45Dennis decided that he was wanting me to
14:47switch subjects and work in cosmology I
14:50never did that I kept going with my what
14:52I was doing yeah but I learned a lot of
14:54physics and I learned Dennis was very
14:57good at at and knowing physics and
15:00knowing the right people to talk to too
15:01it's all the skills that he had were
15:05very influ very important to me it sort
15:08of made me into a physicist basically
15:11well I mean maybe that takes us to a
15:12question of how it is that you
15:14approaches the work that you do so
15:17you've said in the past that you're
15:18quite a visual thinker what is what is I
15:20mean so from everything from penr tiling
15:23all the way through to you know CCC you
15:26know views on cosmology views you know
15:29questions about human consciousness what
15:30what is the unifying theme of being a
15:33visual thinker how does that feature in
15:35the way you do your work it certainly is
15:37an
15:38important element to my thinking and I
15:41remember when I was at school I sort of
15:44thought I was better than most of my
15:45colleagues at mathematics and then I
15:48thought well I feel like a bit of an
15:49oddball and when I go to university I
15:52will found people who think like me that
15:54was not true right what I found was
15:56there were more different ways of
15:58thinking about mathematics than I'd ever
16:00encountered before but the main division
16:02clearly was whether you tended to think
16:05visually or in terms of equations right
16:08and I was clearly one of the fairly
16:12small fraction of the class who was
16:15definitely a visual person right it
16:18actually it didn't do me too well in a
16:20sense because in at University College
16:23they had this way of doing the mass that
16:25to the first two years you actually took
16:29the exam the main exam at the end of two
16:31years it was a three year course and the
16:33third year was to spe do your special
16:35topics okay now my third year I
16:37specialized in the two geometry topics
16:41right but when I learned later how well
16:43I did my geometry papers were not my
16:46best papers the reason was that in
16:49algebra it's easy because you you can I
16:52don't know if it's the real answer but
16:54it's something like always you're using
16:55one side of the brain rather than
16:57crossing over from one to the other I
16:58don't know if it's as simple as that but
17:01with the doing the geometry papers I can
17:03see how to do the problem then I have to
17:05translate that into words write it out
17:07in words and then do it again so it's
17:11all this going from one to the other and
17:12one to the other and I was a slow writer
17:14and I didn't finish the papers whereas
17:17in algebra you can see so you don't have
17:19to switch around in that way this is the
17:21qu problem this is the answer and you
17:22just go like this and so I did much
17:25better in my algebra paper than I did in
17:26Geometry so you you spoke talking about
17:28some of the people that you worked with
17:30and some of the people who taught you
17:32yes um maybe now I could ask if there
17:35was anyone from the history of
17:36mathematics or physics or science more
If you could meet anyone from the field of science, who would it be?
17:38broadly that you would have liked to
17:40have meet but never got the opportunity
17:41to who would you choose well if we're
17:43talking about people from the whole of
17:46History I probably well I don't speak
17:49Italian but I choose I choose galile if
17:52it wasn't a and why is that I don't know
17:56I always had a i people say you new and
17:58all that but I mean Maxwell would have
18:01been a good person too whether I could
18:02have understood his Scottish accent had
18:04a very strong brogue I
18:06believe but but Galileo I always had a
18:10feeling I don't know if it was how much
18:12of it was his trouble with the church
18:14and all that and try battle the the
18:17current views but there were so many
18:19things which he understood which people
18:23didn't I mean obvious things I think now
18:26I what why people one reason why people
18:28didn't believe in the capern theory is
18:31why don't you feel it swishing through
18:32this great speed yeah yeah you hanging
18:35on the chair yeah yeah yeah and so
18:37Gallow points out no no you don't feel
18:39anything yeah g and the principle of
18:42equivalence I like the one with the
18:44fireworks he imagines the fireworks and
18:47they make this beautiful sphere of
18:48Sparks and it drops and it remains a
18:51sphere as it drops you can cancel out
18:54Gravity by Falling freely I mean these
18:57beautiful principles Paul said really so
19:00fundamental to physics and this coupled
19:02with his fight against the
19:06authoritarian role of the of the church
19:09and and that I think that a lot of that
19:12was why he was my particular hero well
19:14Roger I'm afraid we're going to have to
19:16wrap it up there though I wish we didn't
19:19because I have quite a lot more
19:20questions than I started with oh
19:23dear but thank you very much that was
19:26hugely
19:27enjoyable