Max Tegmark's Multiverses

Max Tegmark

one of my favourite posts from two years ago...
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Our Mathematical Universe by physicist Max Tegmark is a popular science book in which he unpacks his theory of the level 1,2,3 and 4 multiverses and then in the last third explains his theory of the mathematical universe. I understood the multiverse idea (the first 3 multiverses anyway) but I didn't really get his concept of the mathematical universe (he's either saying that all the laws of physics depend upon fundamental mathematical concepts which isn't very interesting, or he's saying that everything in the universe (suns, planets, you, me, our conscious minds,) is mathematics itself, i.e. we are living in a platonic universe of numbers that only thinks it's a physical universe - this is a very interesting concept indeed but seems completely crazy to me.) I don't have the competence to judge the last third of the book but I do want to talk about the multiverse idea which is fascinating.
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The level 1 multiverse is very easy to understand. All Tegmark is saying here is that space is infinite and beyond the visible light boundary of our universe there must be other shit out there. Indeed there must be entire universes out there. This is the cool part: since space is infinite and the different way atoms in a universe can assemble themselves is huge, but, crucially, finite, then there must, logically, be universes out there with an exact replica of you reading this and me typing this. Indeed there are an infinite number of universes out there with exact replicas of you and me, and an infinite number of universes where we are slightly different, or you became President or we both swam the Hellespont or I ended up playing rugby for Ireland (I still believe this cd actually happen). Infinity is a very powerful concept and creates some surprising results. Like I say, cool stuff. 
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The level 2 multiverse is also easy to comprehend. In the expansion phase of our universe just after the Big Bang a 'baby universe' was formed that became our universe, an infinite number of these formed, some with completely different laws of physics than our own, but sentient entities like you and me could only exist in one like ours, the Goldilocks one where gravity, Plancks constant, the electro-magnetic force etc. balance perfectly. But again because an infinite number of these multiverses formed there are other yous and mes out there in slightly different physical realities.
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The level 3 multiverse is a trickier beast to grasp. Tegmark and what he claims are "an increasing number of quantum physicists" are beginning to reject the Copenhagen interpretation of quantum physics that has been the dominant interpretation of quantum physics since the 1920's. If you remember the infamous "double slit experiment" from high school you'll recall that when an electron is fired through a piece of metal with a double slit in it sometimes the election acts like a wave and sometimes like a particle. No understands why this is so and it is deeply mysterious to this day. The Copenhagen interpretation basically says that the electron both goes through one slit and does not go through the same slit at the same time. When the election is "observed" by a conscious entity or by a machine (like a camera) its probability wave collapses and it picks one slit to travel down. This has lead to the Schrodingers Cat paradox wherein a cat is both dead and alive at the same time until it has been "observed" - a thought experiment meant to ridicule the Copenhagen Interpretation itself, which I think it did. One alternative to the Copenhagen Interpretation is the Many Worlds Theory. Here there is no need for dead-alive cats, because when the cat experiment is done 2 worlds are created, one in which the cat is dead and another in which it is alive. When you open the cat's box you don't collapse the cat's probability wave you just find out which universe you are in. Similarly when the quantum double slit experiment is carried out, many worlds are created full of scientists carrying out the same experiment. This, some people say, (smart people like David Deutsch) is how quantum computers work - an infinite number of computers exist in an infinite number of many worlds. I know this sounds crazy but I found this part of Tegmark's book very convincing and I now think that the Many Worlds interpretation of quantum physics invented by Hugh Everett is more logical than the Copenhagen Interpretation. Which would mean, if Tegmark, Everett, Deutsch etc. are correct, there is an infinite number of yous and mes existing in what is called Hilbert Space who can interact with one another at a quantum level. If you want to interact with another you in Hilbert space you can do so, here. 
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The level 4 multiverse is the multiverse of Platonic mathematics that I didn't really understand. You can read Tegmark's short explanation of it on his MIT website here. Like I say, I didn't follow this in the book or on the website.
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I would like to offer an an alternate level 4 multiverse that exists temporally rather than physically. Consider Paul Steinhardt and Neil Turok's idea that the universe goes through an infinite number of big bangs, expansions, heat deaths, brane collapses and big bangs...(This is not mentioned in Tegmark's book but I just thought I'd throw it in here. If this is true then not only have I typed this sentence before and you've read it before, but we've all done this infinitely many times in the past, which I for one find depressing. (As did Nietzsche when he thought about the similar notion of eternal recurrence.)) Another possible Level 4 or maybe Level 5 multiverse is Nick Bostrom's idea that we are probably all living in a simulated universe anyway, which he proves from 2 assumptions and then a statistical argument. 
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Scott Aaronson

If indeed there are an infinite number of multiverses out there it raises some interesting questions. First of all it makes what I call Strong Atheism philosophically untenable. With an infinite number of universes there must, logically, be at least 1 universe in which a universal God spontaneously came into existence. It is impossible to say whether we are living in that universe or not. Its unlikely that we're in the universe with the God in it, but its impossible to rule it out. An atheism which denies the existence of all gods is therefore logically mistaken; however a more tempered form of atheism (Soft Atheism) which merely denies that there is any evidence for the existence of God works just fine. There are other really fun consequences of living in a multiverse that this dude has catalogued here. (Seriously click on that link and it will blow your mind.)
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Max Tegmark's book really gave me food for thought. I didn't get all of it, but I enjoyed reading it and I would recommend it for any of you who have ever, Douglas Adams fashion, wondered about the big questions of life, the universe and everything. It got good reviews in the Guardian and The New York Times among many other papers. The best take down I've read of Tegmark's thesis was done by Scott Aaronson on his vastly entertaining and informative computational science blog Shtetl-Optimized.(Tegmark himself gets sucked into the really rather geekily clever comment thread.)

Richard Dawkins Is Not Really An Atheist

I've said this before and I'll say it again. Richard Dawkins, the most famous atheist in the world isn't actually an atheist at all. This is what he said in an interview with the New York Times this week:
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In one essay, Professor Dyson casts millions of speculative years into the future. Our galaxy is dying and humans have evolved into something like bolts of superpowerful intelligent and moral energy.

Doesn’t that description sound an awful lot like God?

“Certainly,” Professor Dawkins replies. “It’s highly plausible that in the universe there are God-like creatures.”

He raises his hand, just in case a reader thinks he’s gone around a religious bend. “It’s very important to understand that these Gods came into being by an explicable scientific progression of incremental evolution.”

Could they be immortal? The professor shrugs.

“Probably not.” He smiles and adds, “But I wouldn’t want to be too dogmatic about that.”

This is not the first time Dawkins has said stuff like this. In a universe 13 billion years old with trillions of Earth like planets, it's not only possible that these god-like entities have evolved but it's much more probable than not that they're out there right now observing us. You can't prove that they exist but logically it seems like a safe bet. Is it beyond the realms of possibility that they have intervened in our planet's history over the last few thousand years? Not at all. Why wouldn't they? Possibly they'll intervene again. Something like prayer then wouldn't be a waste of time then would it? And belief in something like an Afterlife wouldn't be so absurd either. I am not sufficiently brilliant to understand Dawkins's parsing on this. He refuses to believe in god but he accepts the possibility, even probability, that there may be gods or god-like entities watching us. What's the difference? If a Christian were to accept that his god didn't come before the universe but evolved from it would Dawkins accept him as a fellow believer/non believer? 

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I'd also like just one interviewer to ask Dawkins what he thinks of his fellow Oxford professor, Nick Bostrom's work, in which he claims that almost certainly we are living in a Sim universe.

Iain Banks's Ontological Difficulties

Like most of his previous sci-fi novels the new Iain M Banks book Surface Detail deals with the liberal galaxy wide civilization "The Culture" and its attempts to improve human rights throughout the universe. This time The Culture is determined to wipe out the various Hells which lesser cultures propagate in virtual reality to punish their citizens after death. The Hells are awful places where Sim creatures can feel actual pain for all eternity. The way this works is that at the moment of death a copy of a sentient creature's brain pattern is taken and then transmitted into the Sim world and there they are tortured for their crimes in the Real. The Culture - who are opposed to all forms of torture - don't like this and the book follows the Culture agents who have been sent out to stop it.

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Banks's problem is that he is not a philosopher and hasn't thought through the ontological consequences of "taking a copy of someone's brain state" at the moment of death. He seems to think (and crucially for the book everyone in the galaxy seems to think this also) that this cloned virtual entity is still somehow the actual person who passed on. It isn't. It's just a copy. When the real person dies, his consciousness becomes extinguished. A clone of that person will not be that person. There is a well known philosophical conundrum called Searle's Chinese Room which partially deals with this idea and the whole concept of an artificial consciousness in general. People like Searle and Roger Penrose wonder if an artificial consciousness is even possible but let's say for the sake of argument that a machine could replicate consciousness, I still find it hard to believe that civilizations who had acquired this extraordinary technology would have fallen for so obvious a philosophical blunder as to punish a person's clone for something they themselves did not do. You might as well punish a cat in China for something a teenager did in Des Moines.

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Banks generally avoids hard sci-fi and high ideas preferring action scenes but it's a shame he doesn't push himself more and at least have his characters discuss some of these metaphysical concerns. It would force him to try that little bit harder. Banks himself seems wearied by churning out the same old fight scenes page after page to such an extent that at the very end of Surface Detail he seems to have lost interest in the novel completely, wrapping up all the story lines in a final two page character summary. Even the appearance of an old fan favourite seems tacked on and perfunctory. Maybe - like one of the virtual people in the Surface Detail - Banks needs to take a break from writing for a year or two and spend his time in a retreat reading, meditating and thinking instead.

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This blog post also gives me the opportunity to link (again) to Professor Nick Bostrom's page where he quite convincingly argues that all of us are living in a Sim right now and that our consciousnesses are indeed simulated. Of course if this is true then atheism is false and ghosts, gods and afterlifes are all probably real which is not a pleasant prospect.