00:00:00.000 Welcome to Topcast episode 25, the multiverse part 2, a reading from chapter 11 of the
00:00:28.200 beginning of the infinity by David Deutsch, and we're moving slowly through
00:00:33.080 understanding quantum theory, literally understanding quantum theory, applying
00:00:38.760 realism to quantum theory, not denying that aspects of reality are not real,
00:00:44.600 simply because we find that what the science is telling us is to a standing. As I've
00:00:51.040 said in previous episodes, many things are astounding or surprising or
00:00:55.240 amazing, that's no reason for rejecting them. At the time when evolution was
00:01:00.280 first proposed, that seemed to be astonishing, but astonishment alone is not a
00:01:06.240 reason to reject something. I'm not sure who said something to the effect, I'm
00:01:10.320 sure I could Google it right now, but I won't bother, words to the effect that
00:01:13.960 I cannot refute an incredulous stare, and so when it comes to the multiverse and
00:01:19.480 the very many people who reject it out of hand, even professional physicists
00:01:23.800 working in the area, it seems to me that they're trying to use the argument from
00:01:29.560 incredulity, so they are incredulous that this thing could possibly be correct.
00:01:35.640 Now in the readings today, we're going to learn more about fungibility and the
00:01:40.320 significance of that to the multiverse. We're also going to hear a
00:01:44.760 description of the, well, the solution to some of these entanglement problems
00:01:51.760 that we sometimes hear about, and how people try to claim that quantum theory
00:01:56.640 seems to violate special relativity, the prohibition on fast and the speed of
00:02:01.280 light travel, and David's going to explain how that cannot be so. There's also a
00:02:05.800 little hear about personal identity as well, and as always, there's simply
00:02:10.080 some just amazing explanations of what's going on, so I'm just going to dive
00:02:14.880 straight into it. We got up to the part where we were comparing, well, we were
00:02:18.920 discussing fungibility in the context of finance, and how money of certain kinds
00:02:24.240 is fungible. Now we've just learned about how money is legally fungible, and
00:02:29.600 what this means is if the, if you owe someone a dollar, they've lent you a dollar,
00:02:34.000 a dollar note, or a dollar bill, I think it's called in America, or here we have
00:02:38.760 dollar coins in Australia. If you owe someone a dollar, they've lent you a dollar,
00:02:42.160 you do not have to return that specific dollar to that person. Money is
00:02:46.840 fungible. You can return any other dollar, or in any other form, pretty much
00:02:52.520 that you like, to 50 cent coins here will do just as well as a dollar coin
00:02:57.520 here in Australia. So money is legally fungible. That's where we're coming from,
00:03:02.600 where we're going to, is right here, where David writes, quote, it so happens in
00:03:08.320 some situations, money is not only legally fungible, but physically too, and
00:03:12.840 being so familiar it provides a good model for thinking about fungibility. For
00:03:17.120 example, if the balance in your electronic bank account is $1 and the bank adds a
00:03:20.720 second dollar as a loyalty bonus, and later withdraws a dollar in charges, there
00:03:24.600 is no meaning to whether the dollar they would drew is the one that was there
00:03:28.400 originally or the one they had added or is composed of a little of each. It is
00:03:32.760 not merely that we cannot know whether it was the same dollar, or have decided
00:03:37.240 not to care, because of the physics of the situation, there really is no such
00:03:41.240 thing as taking the original dollar, nor such a thing as taking the one added
00:03:45.480 subsequently. Dollars in bank accounts are what may be called
00:03:49.040 configurational entities. They are states or configurations of objects, not what
00:03:54.920 we usually think of as physical objects in their own right. Your bank
00:03:58.440 balance resides in the state of a certain information storage device. In a
00:04:02.800 sense, you own that state. It is illegal for anyone to alter it without your
00:04:06.760 consent. But you do not own the device itself or any part of it. So in that
00:04:12.120 sense, a dollar is an abstraction. Indeed, it is a piece of abstract knowledge,
00:04:16.800 as I discussed in Chapter 4. Knowledge, once embodied in physical form in a
00:04:21.080 suitable environment, causes itself to remain so. And thus, when a physical
00:04:25.800 dollar wears out and is destroyed by the mint, the abstract dollar causes the mint
00:04:30.160 to transfer it into electronic form or into a new instance in paper form. It
00:04:35.000 is an abstract replicator, though unusually for a replicator, it causes itself
00:04:39.720 not to proliferate, but rather to be copied into ledgers and into bank
00:04:43.880 backups of computer memories. So I'm skipping a bit here because I've described
00:04:49.480 this section in a previous episode. David talks about the fungibility of
00:04:55.280 energy and physics. So for example, if it takes you 20 jewels of energy to
00:04:59.800 ride to the top of a particular hill, and then we say that you've gained 20
00:05:04.840 jewels of gravitational potential energy, roughly speaking. I'm ignoring things
00:05:08.920 like friction and the fact that your muscles aren't efficient and all that sort
00:05:11.320 of stuff. Now, if you decide to roll your bike back down, if you're sitting on
00:05:15.880 the bike and you're not pedaling and you're rolling down the hill and you get
00:05:18.760 halfway down and halfway down, you've lost 10 of those 20 jewels of
00:05:23.000 gravitational potential energy. And in theory, with everything's working
00:05:27.640 perfectly and there's no friction and all that sort of stuff as we like to
00:05:29.960 assume in physics, then you've gained 10 jewels of kinetic energy.
00:05:36.440 Now, it doesn't make sense, which of the 20 jewels originally that you
00:05:41.240 gained as gravitational potential energy, which of those 20 will
00:05:46.040 lost as gravitational potential energy, and we're
00:05:48.920 gained as kinetic energy. And so this kind of fungibility is known as
00:05:54.520 configurational entity. And he also mentions that a
00:05:58.600 configurational entity also includes particles in the quantum field.
00:06:03.160 Quantum field theory is this idea that particles are excitations of
00:06:08.680 something more fundamental, still the quantum field.
00:06:12.040 And that would probably require a whole other series of podcasts, not mine,
00:06:18.280 more than likely, to explain. So that's quantum field theory.
00:06:22.680 The more fundamental, in a sense, a version of quantum theory.
00:06:30.280 So I will continue reading after that brief interlude.
00:06:34.280 And David Wright's quote, if the two universes of our fictional multiverse
00:06:39.480 are initially fungible, our transporter malfunction can make them
00:06:43.240 acquire different attributes in the same way that a bank's computer can
00:06:46.600 withdraw one of two fungible dollars and not the other
00:06:50.040 from an account containing two dollars. The laws of physics could, for
00:06:53.560 instance, say that when the transporter malfunctions, then in one of the
00:06:57.480 universes and not the other, there will be a small voltage surge in the
00:07:01.560 transported objects. The laws being symmetrical could not possibly
00:07:04.680 specify which universe the surge will take place in.
00:07:07.960 But precisely because the universes are initially fungible,
00:07:11.000 they do not have to. It is a rather counterintuitive fact that if objects are
00:07:15.400 merely identical in the sense of being exact copies,
00:07:18.760 and obey deterministic laws that make no distinction between them,
00:07:21.880 then they can never become different. But fungible objects, which on the
00:07:26.040 face of it are even more alike, can. This is the first of those weird
00:07:29.800 properties of fungibility that leave let's never thought of,
00:07:32.280 in which I consider to be at the heart of the phenomena of quantum physics.
00:07:36.120 So just pause there. This is my reflection. I'm just
00:07:39.960 catching mine back to the Mark Zender interferometer and it contained that
00:07:44.920 thing called the half-silvid mirror. And if a photon strikes the half-silvid
00:07:48.840 mirror, it's got a 50% chance of going through,
00:07:51.640 being transmitted through the mirror, and a 50% chance of bouncing off the
00:07:54.760 mirror. And in terms of the multiverse, I'm getting it way ahead of what
00:07:58.760 David is in this chapter, of course. But our understanding of what the
00:08:03.880 physics of that situation is, is that the photon being a multiverse object
00:08:09.320 contains uncountably infinite numbers of fungible instances. And so when it
00:08:15.640 strikes the half-silvid mirror, literally 50% of the instances
00:08:19.400 go through the mirror, are transmitted through a 50% bounce off.
00:08:22.680 And so this is the sense in which we can have perfectly deterministic laws,
00:08:27.640 which cause universes to act differently. Okay, back to the book.
00:08:33.160 David writes, quote, here is another, suppose that your account contains $100
00:08:40.200 and you have instructed your bank to transfer $1 from the account to the tax
00:08:44.440 authority on a specified date in the future. So the bank's computer now
00:08:48.520 contains a deterministic rule to that to that effect.
00:08:51.880 Suppose that you have done this because the dollar already belongs to the tax
00:08:55.320 authority, say it had mistakenly sent your tax refund and has given you a deadline
00:08:59.720 to repay it. Since the dollars in the account are fungible, there is no such
00:09:03.320 thing as which one belongs to the tax authority and which belong to you.
00:09:07.720 So we now have a situation in which a collection of entities,
00:09:11.800 though fungible, do not all have the same owner.
00:09:14.840 Everyday language struggles to describe this situation. Each dollar in the
00:09:18.920 account shares literally all its attributes with the others,
00:09:21.960 yet it is not the case that all of them have the same owner.
00:09:25.240 So could we say that in this situation they have no owner?
00:09:28.440 That would be misleading because evidently the tax authority does own one of them
00:09:31.960 and you own the rest. Could one say that they all have two owners?
00:09:36.200 Perhaps, but only because that is a vague term.
00:09:39.720 Certainly there is no point in saying that one cent of each of the dollars is
00:09:43.000 owned by the tax authority because that simply runs into the problem,
00:09:46.360 that the sense in the account are all fungible too.
00:09:48.920 But in any case, notice the problem raised by this diversity within
00:09:53.080 fungibility is one of language only. It is a problem of how to describe some aspects of
00:09:58.520 this situation in words. No one finds the situation itself paradoxical.
00:10:03.640 The computer has been instructed to execute definite rules
00:10:06.280 and there will never be any ambiguity in what will happen as a result.
00:10:10.120 Diversity within fungibility is a widespread phenomena in the
00:10:13.080 multiples, as I shall explain. One big difference from the case of
00:10:16.360 fungible money is that in the latter case we never have to
00:10:19.320 wonder about or predict what it would be like to be a dollar.
00:10:23.560 That is to say what it would be like to be fungible
00:10:26.520 and then to become differentiated. Many applications of quantum theory
00:10:30.440 require us to do exactly that. But first, I suggested temporarily
00:10:35.720 visualizing our two universes as being next to each other in space.
00:10:39.800 Just as some science fiction stories refer to doppelgäin universes
00:10:43.240 as being in other dimensions. But now we have to abandon that image
00:10:47.880 and make them coincide. Whatever that extra dimension was supposed to denote,
00:10:53.320 it would make them non-fungible. It is not that they coincide in anything,
00:10:58.120 such as an external space. They are not in space.
00:11:05.400 That they coincide means only that they are not separate in any way.
00:11:10.200 It is hard to imagine perfectly identical things coinciding.
00:11:13.160 For instance, as soon as you imagine just one of them,
00:11:15.960 your imagination has already violated their fungibility.
00:11:18.840 But although imagination may balk, reason does not.
00:11:22.920 Now our story can begin to have a non-trivial plot.
00:11:25.480 For example, the voltage surge that happens in one of the two universes
00:11:28.920 when the transport of malfunctions could cause some of the neurons
00:11:32.760 in a passenger's brain to misfire in that universe.
00:11:36.120 As a result in that universe, the passenger spills a cup of coffee on another
00:11:39.640 passenger. As a result, they have a shared experience with
00:11:43.160 which they did not have in the other universe, and this leads to romance,
00:11:48.120 The voltage surges need not be malfunctions of the transporter.
00:11:51.560 They could be a regular effect of the way it works.
00:11:53.640 We accept much larger unpredictable jolts during other forms of travel,
00:11:59.160 Let us imagine that a tiny surge is produced in one of the universes
00:12:09.800 or unless it nudges something that happens to be on the brink of changing,
00:12:16.120 In principle, a phenomena could appear unpredictable to observers
00:12:22.440 The first is that it is affected by some fundamentally random
00:12:25.720 indeterministic variable. I've excluded that possibility from our story,
00:12:29.480 because there are no such variables in real physics.
00:12:32.280 The second, which is at least partly responsible for most every day
00:12:35.960 unpredictability, is that the factors affecting the phenomena
00:12:39.640 though deterministic are either unknown or too complex to take account of.
00:12:44.600 This is especially so when they involve the creation of knowledge
00:12:49.640 The third, which had never been imagined before quantum theory,
00:12:53.400 is that two or more initially fungible instances of the object become different.
00:12:57.640 That is, what those transporter and jolts bring about,
00:13:01.560 and what makes their outcomes strictly unpredictable,
00:13:04.680 despite being described by deterministic laws of physics,
00:13:08.440 pause their my reflection. This is the thing that I emphasized last time as well,
00:13:14.600 and I love that. That's just the powerful way that David Deutsch
00:13:23.960 the misconception that so many people have about this particular point.
00:13:29.560 People who think that determinism must mean predictability.
00:13:33.000 And so I'll just read that sentence again, because it's
00:13:39.160 That is what those transporter and jolts bring about,
00:13:42.600 and it makes their outcomes strictly unpredictable,
00:13:46.120 despite being described by deterministic laws of physics,
00:13:51.320 and I'll keep going. These are remarks about unpredictable phenomena
00:13:54.920 could be expressed without ever referring explicitly to fungibility,
00:13:58.360 and indeed that is what multiverse research is usually doing.
00:14:01.960 Nevertheless, as I have said, I believe that fungibility is essential to the
00:14:05.880 explanation of quantum randomness and most other quantum phenomena.
00:14:10.760 Pause their just my reflection. There's just a side note as well.
00:14:14.200 Quantum randomness. When we talk about quantum randomness,
00:14:18.760 what we mean is that things seem subjectively random,
00:14:24.520 and what subjectively random means is that from your perspective,
00:14:29.640 it seems like what happens is random in certain situations.
00:14:46.120 and everyone else on planet Earth, from their subjectivity as well,
00:14:50.120 the outcome is random. It could be heads or it could be tails.
00:14:54.200 That's what subjectively randomness is about. No one knows.
00:14:57.640 No one could possibly predict with perfect accuracy.
00:15:01.640 Indeed, the randomness that we get from coin flips or from dice rolls,
00:15:08.360 or roulette wheels, etc., etc., those random events,
00:15:13.640 by the way, probabilistic as well, because we know what the possible outcomes are.
00:15:19.080 Knowledge won't go affecting the fact that if you flip a coin, it's 50-50,
00:15:23.400 or you roll a dice, it's 1 and 6 for each face if it's a fair dice.
00:15:27.320 And so on. When we know what all the possible outcomes are, we can do probability.
00:15:32.200 Legitimately. I mentioned that because of course there are
00:15:39.160 calculating the likelihood that civilization will survive over the next century,
00:15:45.160 because we don't know the possible outcomes. Knowledge creation will affect that outcome.
00:15:49.080 So subjective randomness is about this idea that we can't predict the outcomes
00:15:56.360 Or even like whether or not something will go wrong with your car, that kind of thing.
00:16:01.720 Now, in terms of the multiverse as a whole, however, nothing is random.
00:16:06.840 There is no objective randomness. Nothing truly on the scale of the multiverse,
00:16:12.280 according to the laws of physics, that is truly random, because everything that can physically
00:16:17.640 possibly happen actually does happen. And if you could possibly get outside of the multiverse,
00:16:23.160 if you were an omnipotent god looking down, you would see that everything is simply unfolding
00:16:28.760 as the laws of physics determined. Nothing was random. In other words,
00:16:32.440 nothing violated the laws of physics. Quantum theory doesn't give us randomness
00:16:38.840 in the objective sense that most people think, just a subjective sense,
00:16:43.160 because you don't occupy all of the universes. If you were some sort of entity
00:16:47.480 that was able to occupy all of the universes simultaneously and have a consciousness
00:16:50.920 that occupied all of the universes simultaneously, then nothing would seem random to you.
00:16:55.000 You would just see the unfolding of all the possible events.
00:16:58.120 And so you would see when you flipped a coin, you know that you would see both heads and tails,
00:17:02.280 which would be a weird thing to experience, I suppose.
00:17:06.120 We'll get into an entity like that in the next episode, I think. Anyway, so look out for that one.
00:17:13.240 I keep promising that, by the way, that there's coming up. We will be talking about a test
00:17:18.760 of quantum theory, which is going to be linked to consciousness.
00:17:23.080 But I digress. Let's go back to the book, David Ratz.
00:17:29.400 All three of these radically different causes of unpredictability could, in principle,
00:17:33.560 feel exactly the same to observers. But in an explicable world, there must be a way of finding
00:17:39.240 out which of them, or which combination of them, is the actual source of any apparent randomness
00:17:44.120 in nature. How could one find out if that is fungibility and parallel universes that are responsible
00:17:49.160 for a given phenomena? Okay, pausing there, and I'm skipping a quite substantial part of this
00:17:56.280 chapter. Just to remind you, this is one of the longest, yes, so this chapter has 47 pages
00:18:06.760 substantially greater than any of the other chapters. I think chapter three, the spark,
00:18:14.280 was the second longest at 36. So it's 11 pages longer than the second longest chapter if I've
00:18:22.200 counted the pages correctly. And so I just highlight that for you because there's no substitute
00:18:29.720 for reading the book. You should buy the book if you haven't. I am skipping a lot of this chapter,
00:18:36.520 in order to explain around it. Now, the bit that I'm skipping here was about
00:18:43.240 the prohibition on communicating between universes. So remember David's telling a science fiction
00:18:50.280 story about these Doppelganger people, one of whom spilled some coffee on another. Now,
00:18:58.280 in a spaceship using a transporter. Now, could the universes, after they differentiate, communicate,
00:19:04.040 and he explains all the reasons, all the things that could happen if they could, but they can't.
00:19:10.040 And so I'm going to skip that part and I would urge you to read that part, read the entire chapter,
00:19:15.960 I suppose. But yes, I am just highlighting the fact I'm skipping significant parts of the book as
00:19:22.280 I go through these chapters. Okay, so David writes, since there is no inter-universe communication
00:19:28.760 in real quantum physics, we shall not allow it in our story. And so that specific route to
00:19:33.960 applicability is not open. The history in which our crew members are married and the one in which
00:19:39.160 they still hardly know each other cannot communicate with each other or observe each other.
00:19:45.160 Nevertheless, as we shall see, there are circumstances in which histories can still affect each other
00:19:49.480 in ways that do not amount to communication. And the need to explain those effects provides the
00:19:54.520 main argument that our own multiverse is real, cause they're just my reflection. So of course,
00:19:59.080 the reason why David has made a point of talking about the prohibition on inter-universe communication
00:20:07.720 is because if there was inter-universe communication, then we wouldn't have to spend
00:20:14.520 47 pages. He wouldn't have to spend 47 pages and give many talks and other philosophers and
00:20:22.440 physicists like David Wallace wouldn't have to write vast books, defending the thesis,
00:20:28.680 because we would all be communicating with these other universes. We would see them directly,
00:20:34.680 you know, it would be easier to convince people of the existence of these other universes.
00:20:41.720 If it was as easy to communicate with these other universes as it was to communicate between
00:20:46.840 cities or nations, but the laws of physics themselves prohibit prevent inter-universe communication.
00:20:54.520 And so we have to be a bit more subtle in the observations that we interpret in order to establish
00:21:02.440 that the multiverse is correct, is the way of understanding quantum theory back to the book.
00:21:09.640 After the universe is in our story, begin to differ inside one Starship.
00:21:13.880 Everything else in the world exists in pairs of identical instances. We must continue to imagine
00:21:19.960 those pairs as being fungible. This is necessary because the universes are not receptacles,
00:21:25.400 there is nothing to them apart from the objects that they can tame. If they did have an independent
00:21:29.800 reality, if they did have an independent reality, then each of the objects in such a pair would
00:21:34.680 have a property of being in one particular universe and not the other, which would make them
00:21:39.240 non-fungible. Typically, the region in which the universes are different will then grow.
00:21:44.440 For instance, when the couple decide to marry, they send messages to their home
00:21:47.880 planets announcing this. When the messages arrive, the two instances of each of those
00:21:53.000 those planets become different. Previously, only the two instances of the Starship were different,
00:21:58.760 but soon, even before anyone broadcasts intentionally, some of the information will have leaked out.
00:22:04.520 For instance, people in the Starship are moving differently in the two universes as a result
00:22:08.360 of the marriage decision, so light bounces off them differently, and some of it leaves the
00:22:12.760 Starship through portals. Marking the two universes, making the two universes slightly different
00:22:17.720 wherever it goes, the same is true of heat radiation in for red light, which leaves the Starship
00:22:23.240 through every point on the hull. Then, starting with the voltage happening in only one universe,
00:22:28.280 a wave of differentiation between the universes spreads in all directions through space.
00:22:33.880 Since information travelling in either universe cannot exceed the speed of light,
00:22:38.360 knock on the wave of differentiation, and since, at its leading edge, it mostly travels at,
00:22:44.120 or near that speed, differences in the head start that some directions have over others
00:22:48.600 will become an increasingly smaller proportion of the total distance travelled, and so,
00:22:53.000 the further the wave travels, the more nearly spherical becomes, it becomes. So I shall call it
00:22:58.440 a sphere of differentiation, pause there, just my reflection. So this is one of the subtle
00:23:05.720 and difficult, I guess, parts to really understand. So all we've got is a quantum event happening
00:23:17.800 here in the Starship. The transport has been used, and it causes a voltage surge in one of
00:23:23.960 the universes are not the other. That's our little quantum event, a little voltage surge
00:23:29.400 caused by electrons doing something or other. Now, that voltage surge magnifies up to cause
00:23:36.840 in the universe where it happened, but not in the universe where it didn't, in the universe
00:23:40.040 where it happened, someone to spill their coffee, they got zapped and so they spilled their coffee,
00:23:45.720 and they spilled their coffee on someone else. And so automatically, we've magnified the quantum
00:23:50.920 event to something larger, and the person upon whom the coffee fell has then talked to the person
00:23:58.600 who spilled the coffee, and they've developed a romance and decided to get eventually get married.
00:24:05.720 Now, as soon as the coffee gets spilled, maybe the person stands up, and so automatically,
00:24:10.520 they're moving differently in that universe compared to the other, where they're still probably
00:24:13.560 just sitting beside each other or something. And so, because they're moving differently,
00:24:18.920 the light reflecting off them differently. And so, to first approximation,
00:24:23.320 what happens is that that light that's been reflected off them is going to strike the walls of
00:24:27.720 the Starship in slightly different ways, and could indeed cause the heating of the Starship in
00:24:32.280 slightly different ways, and that heat leaks out is infrared radiation. Now, there's a lower
00:24:36.520 limit on that that we're going to learn about, which goes to the photoelectric effect there,
00:24:41.480 which we talked about in a couple of episodes back. If you recall, the photoelectric effect
00:24:45.960 talks about how there is a lowest possible energy of light, namely the photon. And if you don't
00:24:53.160 exceed that lowest possible energy, then perhaps nothing happens. That's a possibility that nothing
00:24:59.720 happens. Over time, however, the fact that people get married in one universe, but not the other,
00:25:08.760 causes the entire universe there to gradually change. But in what sense are the two universes
00:25:15.480 kind of different? They differentiate. So initially, the only difference is that in one
00:25:22.440 universe, coffee is spilled and the other, coffee is not spilled. The remainder of the entire
00:25:27.720 universes are perfectly fungible. But over time, at approximately the speed of light, as David
00:25:35.160 has said there, this wave of differentiation spreads out from the coffee spilling incident,
00:25:40.360 causing all sorts of differences. But in particular, it has changed due to the knowledge,
00:25:47.240 namely, if they decide to get married in one universe, then they're going to send messages to
00:25:51.560 their home planet or whatever to their families. And that's going to cause big changes.
00:25:56.920 Well, big changes within the lives of those people. But the rest of the universe might only
00:26:02.360 subtly change. And in fact, some in some areas, barely at all. But as time goes on, those changes
00:26:10.280 do affect something, the size of the classical universe. But it will take a long time for that to
00:26:16.920 happen clearly, because light only travels at 300,000 kilometers per second. And it's going to take
00:26:23.640 some billions of years to get from one side of the side, I say, from one part of the universe to
00:26:29.240 another very, very distant part of the universe. And so this is how differentiation happens.
00:26:34.360 And it is why David Wallace called his book, The Emergent Multiverse, because the multiverse
00:26:43.480 is a theory not simply to explain small things that are happening. That's a great misconception.
00:26:51.880 It's a theory to explain the differences between whole universes, between large-scale structures.
00:26:58.120 Okay, back to the book where David's saying kind of the same thing that I just said there,
00:27:04.680 but better. So I'll read that quote. Even inside the spirit differentiation, there are comparatively
00:27:11.800 few differences between the universes. The stars still shine, the planets still have the same
00:27:17.160 continents, even the people who hear of the wedding and behave differently as a result retain most
00:27:21.880 of the same data in their brains and other information storage devices. And they still breed the
00:27:26.760 same type of air, eat the same type of food, and so on. However, although it may seem intuitively
00:27:32.920 reasonable that news of the marriage leaves most things unchanged, there is a different common sense
00:27:38.200 intuition that seems to prove that it must change everything, if only slightly. Consider what
00:27:44.200 happens when the news reaches a planet, say, in the form of a pulse of photons from a communication
00:27:49.880 laser. Even before any human consequences, there is the physical impact of those photons,
00:27:55.160 which one might expect to impart momentum to every atom exposed to the beam, which would be
00:28:01.240 every atom in something like that half of the surface of the planet, which is facing the beam.
00:28:06.920 Those atoms would then vibrate a little differently, affecting the atoms below through
00:28:10.520 interatomic forces. As each atom affected others, the effect would spread rapidly through the
00:28:16.040 planet. Soon, every atom in the planet would have been affected, though most of them by
00:28:21.240 unimaginably, unimaginably tiny amounts. Nevertheless, however small such an effect was,
00:28:28.040 it would be enough to break the fungibility between each atom and its other universe counterpart.
00:28:33.480 Hence, it would seem that nothing would be left fungible after the wave of differentiation at
00:28:39.320 past. These two opposite intuitions reflect the ancient dichotomy between the discrete and
00:28:46.440 the continuous. The above argument that everything in the sphere of differentiation must become
00:28:51.960 different depends upon the reality of extremely small physical changes. Changes that would be
00:28:57.800 many orders of magnitude too small to be measurable. The existence of such changes follows inexorably
00:29:03.880 from the explanations of classical physics, because in classical physics, most fundamental
00:29:09.240 quantities, such as energy, are continuously variable. Pause the edges. This is just my reflection.
00:29:15.240 Okay, so just to emphasize that. So there's this thing called the inverse square law,
00:29:20.760 okay, and it works for the intensity of light. It's a classical law, and it says that
00:29:27.720 as you move away from the source of light, like the Sun, the intensity of light that you receive
00:29:34.120 from the Sun, usually measured in something like the number of watts, okay, that's the power,
00:29:39.320 the number of joules of energy per second that you've received from the Sun.
00:29:43.160 Well, that decreases as the square of the distance. So if you are here at Earth and you're
00:29:51.160 receiving a certain amount of energy from the Sun, by the way, here at the Earth, it's something
00:29:57.000 like, if I remember, 1,600 watts per meter squared. So if you've got 1 meter square, you get 1,600
00:30:06.200 watts approximately, I think above the atmosphere, by the way, at right angles to the Sun,
00:30:11.720 under perfect conditions. But if you are twice the distance away from the Sun,
00:30:18.440 then the square of that is 4, okay, so you've doubled the distance. So the intensity is
00:30:24.360 4 times less than the 1600 watts, so it would go down to 400 watts. And then if you go still
00:30:31.800 further away again, so you double your distance again, then it's a quarter of that,
00:30:36.120 you know, down to 100 watts. And so this is what the inverse square law is, which would say that
00:30:42.200 it doesn't matter how far away you go from the Sun, they will never come a point where the light
00:30:49.640 disappears completely, or is unable to affect you whatsoever, because it's just a continuous
00:30:57.320 beam of light, all right, it just gets more and more dim, the further and,
00:31:02.440 if it gets more and more dim, the further and the further you get away. It never actually disappears,
00:31:07.080 but we already know, don't we, that light has made a photon. So there must come a distance where
00:31:13.240 you're not going to get a continuous stream of light, eventually the light will go out,
00:31:17.880 it'll disappear, and then it will start, will start to flash at you. And the flashes will become
00:31:23.640 less and less frequent, and that's what the photon theory of light is all about.
00:31:29.720 Okay, so I'll just go back and read forward a little bit. So David wrote and writes, quote,
00:31:38.680 the existence of such changes follows inexorably from the explanations of classical physics,
00:31:43.240 because in classical physics, most fundamental quantities, such as energy, are continuously
00:31:48.520 variable. The opposing intuition comes from thinking about the world in terms of information processing
00:31:54.600 and hints in terms of discrete variables, such as the contents of people's memories. Quantum theory
00:32:01.560 adjudicates this conflict in favor of the discrete. For a typical physical quantity,
00:32:07.800 there is a smallest possible change that it can undergo in a given situation. For instance,
00:32:13.080 there is a smallest possible amount of energy that can be transferred from radiation to any
00:32:16.920 particular atom. The atom cannot absorb any less amount, which is called a quantum of energy.
00:32:22.600 Since this was the first distinctive feature of quantum physics to be discovered,
00:32:26.760 it gave its name to the field. Let us incorporate it into our fictional physics as well,
00:32:31.960 pause there, just my reflection. One might also say it was an unfortunate first discovery,
00:32:39.720 this idea of the quantum, because people now think that quantum physics is really
00:32:46.520 only about the very small, but of course it's not. It's about everything. It's a physical theory
00:32:54.120 that explains the behavior, not only of small things, but of all things, to some extent.
00:33:02.920 It's not going to explain why history happened the way that it did. It's not going to explain
00:33:08.760 whether you should get married or not. It's not going to explain areas of mathematics and biology,
00:33:13.640 but it is going to explain the fact that physical reality, on even the larger scales,
00:33:19.960 is constituted of many different universes. That's the biggest structure that we know of in
00:33:27.640 reality is the entire multiverse. So far from being a theory of only the very small,
00:33:33.960 it also happens to be an explanation of the very larger structure that we have ever invoked in science.
00:33:40.440 Okay, let's keep going. David writes, hence it is not the case that all the atoms on the surface
00:33:46.920 of the planet are changed by the arrival of the radio message. In reality, the typical
00:33:52.280 response of a large physical object to very small influences is that most of its atoms remain
00:33:57.160 strictly unchanged, while to obey the conservation laws a few exhibit at a discrete,
00:34:02.200 relatively large change of one quantum. The discreteness of variables raises questions about
00:34:07.640 motion and change. Does it mean that changes happen instantaneously? They do not, which raises the
00:34:13.720 further question. What is the world like halfway through that change? Also, if a few atoms are
00:34:19.640 strongly affected by some influence and the rest are unaffected, what determines which of the ones
00:34:24.520 to be affected? The answer has to do with fungibility as the reader may guess and as I shall
00:34:29.480 explain next. The effects of a wave of differentiation usually diminish rapidly with distance. Simply
00:34:37.960 because physical effects in general do. Of course, they're my reflection. This is the inverse
00:34:43.000 square law thing. So I'll skip past that. Oh, and then he writes. So let me just continue here,
00:34:54.600 okay? David writes. Even the most violent of quasarjets when viewed from a neighboring galaxy
00:35:00.600 would be little more than an abstract painting in the sky. There is only one known phenomena
00:35:05.480 which, if it ever occurred, would have effects that did not fall off with distance and that is
00:35:10.920 the creation of a certain type of knowledge, mainly a beginning of infinity. Indeed, knowledge can
00:35:17.560 aim itself at a target, travel vast distances, having scarcely an area effect, and then utterly
00:35:24.440 transform the destination. That's absolutely worth reading again because many people who have
00:35:34.440 become enamored by this book and who talked about it in large forums have rightly
00:35:44.440 fixated on that amazing observation by David Deutsch. So again, he says,
00:35:51.720 knowledge can aim itself at a target, travel vast distances, having scarcely any effect,
00:36:00.200 and then utterly transform the destination. End quote. So this is truly astounding
00:36:10.040 because it means that knowledge is very much a kind of physical force, not in the strict sense
00:36:17.320 that the way physicists talk about what forces are. But certainly a quality of nature,
00:36:25.240 force of nature, I think that exists in the universe, that is up there with things like gravity.
00:36:33.240 If you had a god's eye view of the universe and you were trying to explain what the things are
00:36:42.280 that are in that universe causing it to behave the way that it did and to pee the way that it did,
00:36:46.920 you would certainly cite gravity as being of key importance, why planets spherical,
00:36:55.080 why so many objects in the universe spherical, approximately speaking, stars, planets, moons,
00:37:02.680 or because gravity pulls things into spheres, it causes things to take on spherical shapes.
00:37:11.560 And the thing that stops them from collapsing of gravity as pulling them in
00:37:14.440 are often some kind of other chemical force pushing outwards in the case of the earth
00:37:20.760 and rocky type planets, it's the chemical forces, the electrostatic forces stop the thing
00:37:26.520 from collapsing any further than it does. So you would invoke these physical forces to explain
00:37:31.480 the appearance of the universe. But looking at the surface of the earth, you can't invoke
00:37:41.400 only the physical forces. Yeah, here's a picture of Sydney, it's beautiful city.
00:37:49.000 Now, the Sydney Harbour basin there, it's made of sandstone, can't see the sandstone here though,
00:37:56.840 but the harbour is there because it has slowly eroded away over time through the sandstone.
00:38:03.400 And that's been washed out into the ocean, the sandstone, and forms out lovely beaches, in fact,
00:38:08.520 the erosion of the sandstone below beneath Sydney. But the bridge, the opera house, the buildings,
00:38:17.880 they're not natural formations, they're a consequence of knowledge. And indeed,
00:38:24.280 knowledge being transmitted from one place to another. Some of this knowledge was created here,
00:38:29.080 but vast amounts of it were inherited from Europe or the United States.
00:38:36.360 In the future, we're going to have a moon base or a base on Mars. That will be caused by
00:38:44.600 knowledge from the earth aiming itself at that place and transforming that planet.
00:38:53.560 And in the far distant future, when we look at the galaxy as a whole, one would hope
00:39:00.360 that on galactic scales, when we look at certain features of the galaxy,
00:39:05.000 we're going to see some areas far brighter and some areas far more dim than galaxies that are not
00:39:11.640 populated by people. They will simply look different on gross scales and at finer scales,
00:39:20.440 they will look exceedingly more different. We might be able to roughly predict what planets
00:39:28.280 on the other side of the galaxy look like now. They're probably going to look similar to the
00:39:33.160 planets that are here in our solar system, gas giants with pretty clouds, rocky planets that are
00:39:40.440 barren like Mars or Mercury. Perhaps now and again, we'll get an interesting one like Earth,
00:39:45.800 which has oceans and maybe some bacteria or something like that. More or less, within certain
00:39:52.280 limits, we can probably guess what the planets are going to look like. They're going to be spherical,
00:39:57.560 they're going to in general be orbiting stars. What we can't possibly predict is what parts of
00:40:05.320 the galaxy will look like if people get there. If there are places in the universe where there
00:40:11.080 are people, not like us, aliens, we can't predict what they're going to be like. We can't predict
00:40:17.560 what life forms will be like if they've evolved there as well. Some science fiction writers
00:40:22.920 have talked about the possibility of silicon life forms. There's good reasons to think they won't
00:40:28.200 happen. They won't exist. But if they did, if they were able to evolve, evolution brings knowledge
00:40:33.480 into reality in such a way that it can transform it in ways that are unpredictable. But the
00:40:39.000 explanatory type knowledge, it can be taken from one place like the Earth and perhaps in the
00:40:46.440 distant future, aim itself, let's say, to a planet orbiting a star, a hundred light years away,
00:40:54.440 and utterly transform that planet. And in between us and that place, it might have scarcely any
00:41:03.720 effect, as David says. And it will only have an effect, the desired effect at that planet,
00:41:09.160 by transforming it, causing the people that are there, or the robots or whatever, to take the
00:41:17.800 resources that are there and rearrange them, to construct new things, new kinds of ways of creating
00:41:27.480 knowledge there, civilizations and so on. So that is a really, really profound sentence, as
00:41:35.720 always, buried here in the beginning of infinity, which sometimes you can just skim over without
00:41:42.840 realizing the import of. Okay, let's go back to the book, David writes, quote, in our story too,
00:41:50.760 if we wanted to transport a malfunction to have a significant physical effect at astronomical
00:41:55.160 distances, it would have to be via knowledge. All those torrents of photons streaming out of
00:41:59.960 the Starship and carrying intentionally or unintentionally, information about a wedding will have a
00:42:04.760 noticeable effect on the distant planet only of someone there cares about the possibility
00:42:09.240 of such information enough to set up scientific instruments that could detect it.
00:42:14.600 Now, as I have explained, our imaginary laws are physics, which say that a voltage surge happens
00:42:19.560 in one universe, but not the other, cannot be deterministic unless the universe is a fungible.
00:42:25.640 So what happens when the transporter is used again after the universe is a no longer fungible?
00:42:30.520 Imagine a second Starship of the same type as the first and far away. What happens if the
00:42:36.120 second Starship runs its transporter immediately after the first one did? One logically possible
00:42:41.480 answer would be that nothing happens. In other words, the laws of physics would say that once
00:42:46.040 the two universes are different, all transporters just work normally and never produce a voltage
00:42:50.520 surge again. However, that would also provide a way of communicating faster than light, albeit
00:42:55.000 unreliably and only once. You set up a voltmeter in the transporter room and run the transporter.
00:43:00.600 If the voltage surge is you know that the other Starship, however far away, has not yet run its
00:43:05.080 transporter because if it had, it would have put a permanent end to such surges everywhere.
00:43:10.200 The laws governing the real multiverse do not allow information to flow in that way.
00:43:15.160 If we want our fictional laws of physics to be universal from the inhabitants point of view,
00:43:19.240 the second transporter must do exactly what the first one did. It must cause a voltage surge in
00:43:24.200 one universe and not in the other. But in that case, something must determine which universe the
00:43:30.280 second surge will happen in. In one universe but not the other is no longer a deterministic
00:43:35.400 specification. Also, a surge must not happen if the transporter is run only in the other universe.
00:43:41.800 That will constitute inter-universe communication. It must depend on both instances of the
00:43:47.320 transporter being run simultaneously. Even that could allow some inter-universe communication
00:43:52.520 as follows. In the universe, where a surge has once happened, run the transporter at a
00:43:57.000 pre-arranged time and observe the voltmeter. If no surge happens, then the transporter and the other
00:44:01.320 universe is switched off. So we are at an impasse. It is a remarkable amount of subtlety that can
00:44:05.800 be in the apparently straightforward binary distinction between the same and different
00:44:09.720 or between affected and unaffected. In the real quantum theory too, the prohibitions on
00:44:13.880 inter-universe communication and faster than light communication are closely connected.
00:44:18.040 There is a way, I think it is the only way, to meet simultaneously the requirements that our
00:44:23.240 fictional laws of physics be universal and deterministic and forbid faster than light into
00:44:29.400 inter-universe communication. More universes. Imagine an uncountably infinite number of them,
00:44:35.800 or initially fungible. The transporter causes previously fungible ones to become different,
00:44:42.440 as before, but now the relevant law of physics says the voltage surges happen in half the
00:44:48.600 universes in which the transporter is used. So if the two starships, both run their transporters,
00:44:54.520 then after the two spheres of differentiation of overlap, there will be universes of four
00:44:59.240 different kinds, those in which our surge happened only in the first starship, only in the second,
00:45:05.560 in neither and in both. In other words, the overlap in the overlap region, there are four different
00:45:10.920 histories, each taking place in one quarter of the universes. Pause their mind reflection.
00:45:16.280 This is the full mark zendy interferometer type thing where you end up with these four different
00:45:20.600 possibilities. If you've got two half-silven mirrors, because you get transmission transmission,
00:45:26.840 transmission reflection, reflection transmission reflection reflected. So you get that in if you
00:45:32.680 want to know more about that. Go back a couple of episodes and have a look at the mark zendy
00:45:37.160 interferometer explanation that I gave. So you end up with this one event, so to speak,
00:45:44.360 causing this differentiation into four different kinds. Okay, I'll just, let's go back to the book,
00:45:51.320 David writes, quote, our fictional theory has not provided enough structure in its multiverse
00:45:56.280 to give meaning to half the universes, but the real quantum theory does. As I explained in
00:46:01.160 chapter 8, the method that a theory provides for giving a meaning to proportions and averages
00:46:05.560 for infinite sets is called a measure. A familiar example is that classical physics assigns
00:46:10.920 lengths to infinite sets of points around general line. Let us suppose that our theory provides
00:46:16.040 a measure for universes. Now we are allowed storylines such as the following. In the universes
00:46:21.880 in which the couple married, they spend their honeymoon on a human colonized planet that the
00:46:25.880 spaceship is visiting. As they are teleporting back up, the voltage surge in half those universes
00:46:32.280 causes someone's electronic note pad to play a voice message suggesting that one of the newly
00:46:36.760 words has already been unfaithful. This sets off a chain of events that ends in divorce.
00:46:41.000 So now our original collection of fungible universes contains three different histories.
00:46:45.480 In one, comprising half the original set of universes, the coupling questioner still single.
00:46:50.680 In the second, comprising a quarter of the original set, down married, and in the third,
00:46:55.000 comprising the remaining quarter, that divorced. Thus, the three histories do not occupy equal
00:47:00.120 proportions of the multiverse. There are twice as many universes in which the couple never married,
00:47:04.440 as there are in the universes in which they are divorced. Pause down my reflection. Mark's
00:47:08.040 enderings from it again. Similar kind of number of break up proportions, okay? It's a half a
00:47:14.760 quarter a quarter. Back to the book, David Wright's quote. Now suppose that the scientists on
00:47:21.480 the Starship know about the multiverse and understand the physics of the transporter,
00:47:25.160 though note that we have not yet given them any way of discovering those things.
00:47:28.680 Then they know that when they're on the transporter, an infinite number of fungible instances
00:47:32.600 of themselves all sharing the same history are doing so at the same time. They know that a
00:47:36.840 voltage surge will occur in half the universes in that history, which means that it will split
00:47:40.760 into two histories of equal measure. Hence, they know that if they use the voltmeter, capable of
00:47:47.000 detecting the surge, half of the instances of themselves are going to find that it has recorded one,
00:47:52.440 and the other half are not. But they also know that it is meanings to ask, not merely impossible,
00:47:58.760 to know, which event they will experience. Consequently, they can make two closely related
00:48:04.360 predictions. One is that despite the perfect determinism of everything that's happening,
00:48:08.600 nothing can reliably predict for them whether the voltmeter will detect the surge.
00:48:14.520 The other prediction is simply that the voltmeter will record a surge with probability one half.
00:48:18.600 Thus, the outcomes of such experiments are subjectively random from the perspective of any observer,
00:48:24.840 even though everything that is happening is completely determined objectively.
00:48:28.600 This is also the origin of quantum mechanical randomness and probability in real physics.
00:48:33.480 It is due to the measure that the theory provides for the multiverse, which is in turn due
00:48:39.480 to what kinds of physical processes the theory allows and forbids. Notice that when
00:48:45.400 a random outcome, in this sense, is about to happen, it is a situation of diversity within
00:48:50.920 fungibility. The diversity is in the variable, what outcome they are going to see.
00:48:57.000 The logic of the situation is the same, as in cases like that of the bank account I discussed
00:49:01.480 above, except that this time the fungible entities are people. They are fungible yet half of
00:49:07.960 them are going to see the surge and the other half, not. In practice, they could test
00:49:13.400 this prediction by doing the experiment many times. Every formula purporting to predict the
00:49:19.320 sequence of outcomes will eventually fail. That tests the unpredictability. And in the
00:49:24.760 overwhelming majority of universities, the surge will happen approximately half the time.
00:49:30.280 That tests the predicted value of the probability. Only a tiny proportion of the instances of
00:49:34.920 the observers will see anything different. Pause their my reflections. There is a hint at the
00:49:40.120 testability of the multiverse. And against classical rivals. So classical physics says the
00:49:49.560 same thing can happen over and over again. This is classically what science says. The whole point
00:49:53.960 of repeating your experiment to find out whether or not it is reliable is to see whether you get
00:49:58.840 the same outcome each time. Well here, if we repeat the experiment, we should find that we won't
00:50:06.280 get the same result every single time. If there's a situation in which it's 50-50, then we should
00:50:14.440 get different results every single time, not every single time. We should approximately
00:50:22.280 we should approach the 50-50 limit. Okay, so I'll just my reflection here. I'm going to skip
00:50:30.520 another substantial part here. And David talks about how the sphere of differentiation as it spreads
00:50:35.240 out. It too can cause differentiation in probabilistic ways. Okay, or ways that subjectively random.
00:50:47.400 And so although the first thing that happened was this quantum event, this voltage surge and
00:50:50.840 the spilling of coffee, the wave of differentiation that spreads out can then differentiate at
00:50:56.920 each time a thing could have happened one way or the other or in many different ways. All the
00:51:04.200 possible outcomes happen. And so that causes, quote from the book, the number of histories
00:51:12.760 continues to increase exponentially. And soon, there are so many variations on events that several
00:51:18.040 significant changes have been caused somewhere in the multi-versal diversity of the Starship.
00:51:23.080 So in the total number of such histories, so the total number of such histories increases
00:51:26.840 exponentially too, even though they continue to constitute only a small proportion of all histories
00:51:31.880 that are present. Soon after that, in an even smaller but still exponentially growing number
00:51:37.400 of histories, uncanny chains of accidents and unlikely coincidences will have come to dominate
00:51:42.920 events. I put those terms in quotation marks because those events, namely the accidents and the
00:51:49.640 unlikely coincidences. Those events are not in the least accidental. They've all happened
00:51:55.800 inevitably, according to deterministic laws of physics. All of them are caused by the transporter.
00:52:00.600 And David's pausing there, just my reflection, and this is where I think I'll end up today
00:52:07.320 because we'll get to this. David does write about this or not in these words.
00:52:15.080 When I was learning about the multi-verse version, David introduced me to
00:52:23.240 so-called Harry Potter universes. So I'll give you my take on what Harry Potter universes are like.
00:52:28.120 They kind of follow this idea here. Because you can have these chains of extremely unlikely events
00:52:38.760 in a very small measure of universes, but still exponentially increasing in number,
00:52:48.440 what could happen is this? There could be literally a universe in which you have
00:52:54.440 some teenage bespeckled boy who carries a wooden stick. And each time he does this with the
00:53:05.160 wooden stick and says, abracandabra, a spark comes out of the wooden stick. That's perfectly
00:53:11.480 consistent with the laws of physics. Electrons can gain enough energy to come out of wooden
00:53:18.600 sticks. They can just happen. Quantum theory says things very bizarre. Here's a simpler example.
00:53:31.400 Here's a glass of water. Now, interesting thing about water is that at sea level, it has a boiling
00:53:39.480 point of 100 degrees Celsius. If we heat this water on a stove, then 100 degrees Celsius starts
00:53:46.360 to bubble away. And it will all disappear if you continue to boil it. That's not surprising.
00:53:51.320 So if water has a boiling point of 100 degrees Celsius, an interesting question is,
00:53:56.920 why should it evaporate right now? If I leave this here for long enough, at a mere temperature
00:54:01.800 in this room right now of about 23 degrees Celsius, eventually after a long enough time,
00:54:07.640 it will all evaporate away. But it's not boiling. So how does evaporation work? Because evaporation
00:54:13.720 can happen at any temperature. The solution to that is that the 33 degrees Celsius water that's
00:54:22.440 in here, let's say, that's the average. Temperature is a measure of the average kinetic energy roughly
00:54:29.560 speaking of the particles of water in here, the H2M molecules. An average means that some of them
00:54:37.240 have much less energy than 23 degrees Celsius. And some of them have energy much higher than
00:54:44.360 23 degrees Celsius. Some of them have a temperature, effectively, have a motion that corresponds to
00:54:53.160 a temperature above boiling point. And so those ones boil away. And so as they boil away, in fact,
00:54:58.920 it causes the temperature to go down because you're losing the highest energy ones.
00:55:03.080 But you can't possibly take away all the high energy ones because although the average might go
00:55:07.000 lower and lower, it's still getting heat from the environment as well. So this is how evaporation
00:55:12.600 in general works. Now, it is consistent with the laws of physics that because it's an average,
00:55:20.200 it could just happen that all of the particles, why does any one particle have a temperature or a
00:55:26.680 motion that corresponds to a temperature above 100 degrees Celsius? Why should any one of them have that
00:55:31.640 by chance? Could more than the average have a temperature above 100 degrees Celsius? Yes.
00:55:38.200 Could all of them, according to what we know about physics, could all of them just by chance
00:55:43.800 have a temperature above 100 degrees Celsius? Yes. Exceedingly unlikely. Exceedingly unlikely.
00:55:50.200 You would never expect, I would never expect to be drinking this and suddenly to be scolded and burnt
00:55:55.160 because the proportion of universes in which that happens is so exceedingly small.
00:56:02.840 But that's the principle, right? The principle is that randomly,
00:56:08.760 all of the molecules in this glass of water could, extremely, exceedingly rarely,
00:56:17.080 become, start moving so fast that the entire glass of water here boils.
00:56:22.360 What's that got to do with Harry Potter universes? Well, the boy in some universe somewhere
00:56:29.640 that a speckled boy with his wand, a say wand with his stick goes abracadabra and a spark comes
00:56:38.040 out. That's exceedingly unlikely, but it could happen, it could happen once. According to
00:56:44.200 the quantum theory, it could continue to happen. It's not the fact that the spark is caused by the
00:56:52.840 boy doing this or saying abracadabra, uttering the magic words. There's no causal effect
00:56:58.920 between those things. It's perfectly consistent with the laws of it. It just happens by chance
00:57:03.480 that these electrons go flying out of the end of the stick, but in his head and all people around
00:57:10.360 him, they think, wow, Harry Potter has the ability to actually do magic. Perhaps he keeps on doing
00:57:17.320 this thread his entire life and every time he does that, the spark comes out. And so he apparently
00:57:22.760 is a wizard who is able to have lightning come from his wand. And so he appears to be a wizard,
00:57:31.160 but he only appears to be a wizard. It only appears to be the case that magic works.
00:57:36.520 Magic doesn't actually work. And in fact, if there is a universe in which, and there is,
00:57:43.320 where a boy has gone abracadabra and the spark has come out, the overwhelming majority of
00:57:48.600 universes then are such that the second time he does it, it would never happen again. It won't
00:57:53.720 happen or the third time or the tenth time or the millionth time he does it. It's just not going
00:57:59.400 to happen again. But in some universes, it will happen once in a lesser number of universes.
00:58:06.680 It happens twice. In a lesser still number of universes happens three times. You get my point,
00:58:12.600 there will be some exceedingly small number of universes where every time he does it, it works.
00:58:18.920 Well, I say works. It appears to work or that event happens, the spark comes out. And so we
00:58:24.760 termed these universes such universes, Harry Potter universes, where exceedingly rare events happen.
00:58:33.720 And the people in those universes could concoct the story about how magic works.
00:58:38.600 And so there are places, as David will explain in the part that I'll read next time,
00:58:42.680 where bizarre fiction appears to be true. Or in fact, it in certain bizarre types of fiction
00:58:49.320 are true. But that doesn't mean that the things are causal there. So this has to do with
00:58:59.720 whether or not the knowledge they have there is valid. And this goes deep into the idea of
00:59:03.720 information flow. So there we've got a whole bunch of chance coincidences, okay, that the saying
00:59:09.720 of the abracadabra, the spark flying out of the stick, and therefore people referring to the
00:59:15.240 stick as a wand and to the spark as magic and Harry Potter in that universe as a wizard.
00:59:20.920 Even though the stick is just a stick, the spark is just a spark. It's not magical lightning.
00:59:28.280 Harry Potter is just a kid with spectacles. He's not a wizard, but people in those universes,
00:59:35.000 they don't know because it's just been freak coincidences. But that's an exceedingly
00:59:40.760 small number of universes. One would expect a number of universes smaller than the number of
00:59:47.560 universes in which suddenly all of the water in all of the oceans on planet Earth has boiled away
00:59:53.880 instantly. It's happened somewhere in the multiverse, but the measure of universes where that's
1:00:00.280 happened is so tiny as to not really be of anything other than purely academic interest. Okay,
1:00:07.800 so more on that next time I hope this one was enjoyable. Until next time, see you, bye.
