00:00:00.000 David, the laws of physics seem incredible in that they are perceptible to us.
00:00:06.440 We can manipulate them, we can use them for predictions.
00:00:11.160 What does that begin to tell us in terms of their fundamental nature and how can we begin
00:00:16.560 to look at the laws of physics and see what the nature of reality is?
00:00:23.560 It's certainly the case, and I think this is now uncontroversial, that if the laws of physics
00:00:29.000 were very slightly different in almost any way, there could be no life in the universe,
00:00:36.800 no complex chemistry, and no thinking people, and therefore no one who knows the laws
00:00:46.280 So they are somehow almost infinitely special in that they allow themselves to be, as you
00:00:54.540 said, not just known, but also used, and that they were used before humans even existed
00:01:01.080 to create life and then for the human species to evolve.
00:01:06.960 Now that has been for several decades, an unsolved problem at the foundations of physics.
00:01:16.160 Why that is so, called the fine-tuning problem?
00:01:21.840 And it began in a serious way, people began to investigate this in the 1970s, the physicist
00:01:29.880 Brandon Carter, who was investigating the evolution of stars, found that if the charge on
00:01:35.800 the electron had been only a few percent different, either larger or smaller, then there
00:01:40.800 would be no complex chemistry and no opportunity for life to evolve.
00:01:47.160 So the standard take on this is that this is evidence that the laws of physics, as we
00:01:55.880 see them, are not the only ones that are instantiated in physical reality.
00:02:02.400 It's rather like the argument, you know, you win the lottery and you say, why me?
00:02:07.720 And it seems very strange that the lottery should have picked out you, and the solution
00:02:14.480 to that is you'll realize that that's not such a strange thing if you realize that a million
00:02:20.720 people entered the lottery and one of them had to win.
00:02:24.160 Or if you hit a golf ball and it lands on a blade of grass, you say, what are the odds
00:02:29.440 You know, how many blades of grass there are to deal?
00:02:33.400 But the thing that makes the fine-tuning problem more mysterious than just any old random
00:02:39.560 number like a lottery or a blade of grass is that the particular blade of grass that
00:02:44.200 landed on seems to have a purpose, seems to be tuned as they call it for our existence.
00:02:52.200 And this seems to violate the one of the first things that was realized at the beginning
00:02:59.680 of modern science, which is that humans are not especially distinguished by the laws of
00:03:05.400 physics as the center of the universe or as the purpose of the universe or anything like
00:03:10.680 that, but that everything about us is explained by laws that don't particularly refer
00:03:20.640 So the explanations that have been given are that and they're radically different.
00:03:27.680 And these are pretty much the only two explanations is that in one way we have been designed
00:03:33.400 to be special by some creator God that some people would like, or some super intelligent
00:03:40.360 species in which we're assimilate, some sort of a creative process, maybe not necessarily
00:03:45.000 a traditional God, some sort of creative process.
00:03:48.200 The other extreme are multiple universes in a cosmological sense, which each one of these
00:03:53.720 multiple universes, an infinite number perhaps, picks out different laws of physics so
00:03:58.800 that in the process of this randomized approach, one would or more would give rise to us
00:04:05.080 and we're in that universe, so it's the only one we're in, so we're asking the question
00:04:14.480 I think both of those are incapable of solving the problem.
00:04:18.920 The first one, the idea that the laws of physics were designed by someone or something,
00:04:24.520 simply raises the question that that thing also has to be fine-tuned.
00:04:30.120 It also has the very properties that we're wondering about the origin of in ourselves.
00:04:39.480 It's okay to kick the problem up a level if you then have an easier problem, but if you
00:04:43.800 have the very same problem, then that's an infinite regress.
00:04:47.400 Or it might be a harder problem if that's a non-physical thing.
00:04:50.880 Could it even be a harder problem in which case it's worse than an infinite regress?
00:04:54.960 Now the other idea, which is the one that is greatly favored by cosmologists currently,
00:05:01.480 and not entirely sure why, but it has become the prevailing theory in cosmology, is this
00:05:07.320 idea that there's an ensemble, a vast set of different universes.
00:05:12.000 Now the trouble with that, as was pointed out by Richard Feynman many decades ago, is that
00:05:18.760 if that, if the only explanation why the laws of physics seem to favor us is that if we
00:05:29.720 weren't here, we wouldn't be asking, the overwhelming majority of universes in which someone
00:05:35.320 is asking, they are only just asking, that is the universe is only just good enough.
00:05:42.520 There are many, many more universes where, for example, this room and its contents have
00:05:48.720 just sprung into existence and will disappear immediately afterwards.
00:05:54.920 And this idea that the universe could be a just one in an ensemble suffers from
00:06:05.280 the fatal flaw that most such universes that have the property of containing us only
00:06:12.560 just have it, and we're about to die because a sphere of heat is coming in at the speed
00:06:20.440 of light and will extinguish us in the next picosecond.
00:06:24.160 So that means that some principle other than just anthropic self-selection has to be responsible
00:06:35.920 for the fine tuning, and it can't be designed because that just kicks the problem upstairs.
00:06:43.280 It sounds like there's no solution because I don't got one, I'm waiting for, I'm waiting
00:06:48.080 I don't pretend to have a solution, but I think I have an argument why there can be a solution
00:06:57.120 If the solution isn't either of those two, then the solution is a law or physics.
00:07:02.360 It's a law or physics that applies in our universe, or perhaps in our universe and a
00:07:09.040 But just having, as I said, just having multiple universes doesn't solve the problem.
00:07:13.800 They would have to be multiple universes that are tuned so that most things in them don't
00:07:24.920 I think the key is that the laws of physics, as we currently conceive them, are based
00:07:31.760 on atoms and working out everything that happens from a microscopic level, but if we admit
00:07:39.560 into fundamental physics, laws about emergent properties, such as computation, one of those
00:07:47.160 may imply that we exist without being anthropocentric.
00:07:50.640 David, as we consider the laws of nature, we always try to find those which are the most
00:07:58.040 fundamental, and physicists would have us go deeper and deeper in a reductionist sense
00:08:05.040 to try to find those laws, how do you look at even approaching the problem?
00:08:11.400 What I take to be a fundamental law is one that is implicated in many other explanations,
00:08:19.080 and the most fundamental laws in physics happen to be reductionist laws, quantum theory
00:08:25.320 and the theory of relativity, although there are non-reductionist laws like the second
00:08:29.840 law of thermodynamics, even in physics, but there are other laws, the principle of evolution,
00:08:36.800 for example, which says that adaptive complexity can only arise through variation and selection
00:08:43.320 is a rigid law of nature and yet is intrinsically emergent, so that's another law, the laws
00:08:49.880 of epistemology that say that knowledge is acquired by conjecture and criticism.
00:08:57.560 So now you've given three radically different kinds of laws from fundamental physics
00:09:02.240 to biology of species, to approach to knowledge that you're saying are all fundamental,
00:09:12.200 but are radically different even in their categories.
00:09:15.560 Yes, they are all fundamental in that they are needed to explain many things, and we can't
00:09:21.080 explain everything in terms of just one of those strands.
00:09:25.160 And therefore, do you explanation is an organizing principle that can unite those?
00:09:33.320 And one of the things that looking at it this way helps with is that we can see that
00:09:40.760 laws at different levels of emergence actually mesh together into what I call the fabric
00:09:48.520 of reality into a sort of unified worldview, which we can then extend.
00:09:53.240 One of the things I'm trying to work on now is extending the theory of computation into
00:09:58.560 the theory of not just what can and can't be done with abstract objects, but the theory
00:10:05.000 of what can and can't be done with any object, which is a way of looking at physics
00:10:11.840 in the manner of the quantum theory of computation.
00:10:15.440 And remarkably, that connects not only physics and computation, but it also has all sorts
00:10:21.080 of philosophical implications, such as optimism, comes out of that theory.
00:10:26.200 Well, we certainly need some optimism, so, but I'm in a loss to see how we can get optimism
00:10:38.840 It's the generalization of the theory of computation to the rest of physics.
00:10:43.400 And the way it is linked to optimism is very simple.
00:10:46.680 If you imagine the set of all transformations, we want to transform the world into a better
00:10:54.680 Now, some of those transformations are permitted and some are not permitted by the laws
00:11:01.040 So the question is, which ones of them can we actually achieve in real life?
00:11:07.080 And the answer to that must be, according to constructor theory, that the ones that we can
00:11:12.560 achieve in real life are precisely the ones that are not forbidden by the laws of
00:11:19.960 So, if the laws of physics say we can't travel faster than speed of light, then we never
00:11:25.360 But if there isn't a law of physics that says you can't live to be 500, then living to
00:11:36.760 So what are the limitations of physical laws that will give us those ultimate constraints?
00:11:43.280 Because anything within those constraints is ultimately achievable.
00:11:49.120 So the laws of physics are not actually very onerous in regard to achieving what humans
00:11:57.840 Even traveling to another galaxy, although you can't do it in the time, fortunately,
00:12:03.560 in relativity means that your time will slow down if you travel very fast.
00:12:07.080 So if you really wanted to travel to another galaxy in your lifetime and you had the right
00:12:17.320 The things that we are accustomed to calling evils, even the ones that are deemed to be
00:12:24.440 inevitable evils like death, are actually just a matter of technology to solve.
00:12:30.600 So you look very optimistically in terms of what technology can achieve.
00:12:36.640 And this, as I said, follows from very fundamental considerations within physics.
00:12:41.200 The thing is, if there were a thing that we can't achieve, no matter what knowledge we
00:12:45.880 bring to bear, let's say it was living to 500 or something, there's no law of physics,
00:12:51.440 suppose that there's no law of physics that we can't, but we still couldn't achieve
00:12:55.480 And then if we can't achieve that, no matter what knowledge we bring to bear, then there
00:13:00.760 is another law of physics that says that we can't do that.
00:13:03.320 And that's a testable law, a testable regularity in nature is a law of physics.
00:13:10.080 So as we push forward, as we push knowledge forward, as you would like to say infinitely
00:13:15.760 forward, as we do this, as we do this, we will either make progress or discover new laws
