00:00:00.000 David, there seems to be a fad in physics today that information is the most fundamental thing in the universe.
00:00:08.700 It's not just that information describes matter and energy and feels, but at the bottom of matter is information.
00:00:19.200 And as a consequence, the universe itself is not a metaphor like a computer, but in fact is a computer, and that's what reality is.
00:00:34.700 It misses the lesson of what is really important about the link between computation and physics.
00:00:41.700 Computation and with it information is indeed very fundamental, but it's not the most important thing.
00:00:49.200 It's not the thing that the universe is made of, as it were.
00:00:53.000 So there are various, there are variants of this theory like the universe is a computer, or that the universe is a program running in God's computer or something like that.
00:01:04.400 It seems to me that those theories all missed the point about the universality of computation, which is the way that computation links with physics.
00:01:16.700 Through the existence of a universal computer, a computer that can compute anything that can be computed and can therefore simulate any physical object.
00:01:26.400 If this computer were outside the universe, it wouldn't be very remarkable that you can always imagine some kind of computer with some kind of way of operating that would simulate any laws of physics, no matter what they were.
00:01:42.000 And so you lose the fact that our actual laws of physics are intimately connected with computation.
00:01:49.800 It's not that there's a computer outside the universe, it's that we can make universal computers inside the universe.
00:01:56.800 That is a token of the computability of the laws of nature.
00:02:01.400 It's the reason why it's the reason for the unreasonable effectiveness of mathematics in the natural sciences.
00:02:08.700 It's the reason for the existence of life and the possibility of science.
00:02:13.400 Those things are explained by the existence of computers in the universe, but wouldn't be explained if the universe was in a computer.
00:02:22.900 If that is true, how do you account for this growing sense that at the bottom, the bedrock of reality is information that it stuff comes from bit information?
00:02:39.900 It's perhaps a natural mistake to make, given the fundamentalness of computation. And perhaps the reason for the mistake, now that I can think of it, is that we are accustomed to explaining things in reductionist terms.
00:02:56.900 So instead of explaining things in terms of space, time, atoms and forces, we explain it in terms of qubits or bits or qubits and computations.
00:03:09.900 But that is not an advance in explanation for the reason that I just said. And the real connection is the computability of the laws from within the universe.
00:03:29.900 And so that makes information part of the process of the universe, but not sitting at the fundamental nature of the universe.
00:03:38.900 Well, its existence is indeed fundamental, but it's not fundamental in the reductionist sense.
00:03:45.900 It's fundamental in the sense that there is a law of nature that the universe is computable or that a universal computer exists.
00:04:00.900 And would this computation, this information work on various levels in a hierarchical sense, or would it only exist on the most fundamental level as you understand information?
00:04:05.900 Computers are emergent objects. There is no such thing as a computer at the subatomic level. Or if you did make a computer at the subatomic level, it wouldn't be universal, and therefore wouldn't be fundamental.
00:04:20.900 The fundamental computers are the ones that are universal, and they are the ones that are quite big. They're like the universe, the computers that we actually have and use in everyday life.
00:04:29.900 But information could operate on the most fundamental level. It could and does, but that, as I have argued, can't underlie that that's just an alternative way of talking about atoms.
00:04:42.900 But this concept of information, even if it's not at the most fundamental level, when it exists, as you see, it does it exist at each level of the hierarchy of the laws of nature, or is it only existing at the level of physics?
00:05:00.900 Yes, a good question. Information exists at every level, including at the fundamental level of atoms, whether an atom is there or not, is a fundamental thing.
00:05:12.900 But at the level of laws of nature, information comes in at a particular level of explanation, namely the level at which there are computers, and the level at which there are people thinking about stuff, that level of explanation.
00:05:28.900 How then does it, that way of thinking allow us to understand reality better?
00:05:34.900 Because almost all ways that the laws of physics could be do not have the property that a universal computer could exist.
