Tegmark's latest

[spoonless]

I've been wanting to sit down and write something about my recent LA trip... but things have been pretty busy since I've gotten back, especially since my processor burnt out and I ended up having to upgrade to almost a completely new system. (I still need to get everything fully into the case, as parts of it have been sitting around on the floor running.)

Instead of writing about LA, which I intended to do at some point soon, I'm going to link to Max Tegmark's latest paper which argues that the External Reality Hypothesis (the idea that there exists an external reality independent of human minds) implies what he calls the Mathematical Universe Hypothesis (that physical reality is entirely a mathematical structure). This is, in my opinion, the most powerful argument against the Copenhagen Interpretation of quantum mechanics (ie, antirealism) as opposed to the Many Worlds Interpretation (ie, realism). He goes into mathematical platonism, Godel incompleteness/undecidability, the halting problem, various multiverses, and the Simulation Argument (the idea that we're living in a computer simulation run by beings living in some other reality outside of our "Matrix"). Many of the points he makes, especially regarding the simulation argument, have been stuff I have also been thinking lately, and meaning to write down and explain. But since he's beat me to the punch, I'll just link to his paper rather than writing them out:

Tegmark: The Mathematical Universe

I do have a few more things (well, a lot more) to say on this besides what he says in this paper, and a few things I might have said slightly differently. But to write that out would delay my post on LA even further, which I don't want to do. So it'll have to wait.

I leave you with Tegmark's poetic closing two paragraphs:

"[The Mathematical Universe Hypothesis] is arguably extreme in the sense of being maximally offensive to human vanity. Since our earliest ancestors admired the stars, our human egos have suffered a series of blows. For starters, we are smaller than we thought. Eratosthenes showed that Earth was larger than millions of humans, and his Hellenic compatriots realized that the solar system was thousands of times larger still. yet for all its grandeur, our Sun turned out to be merely one rather ordinary star among hundreds of billions in a galaxy that in turn is merely one of billions in our observable universe, the spherical region from which light has had time to reach us during the 14 billion years since our big bang. Then there are more (perhaps infinitely many) such regions. Our lives are small temporally as well as spatially: if this 14 billion year cosmic history were scaled to one year, then 100,000 years of human history would be 4 minutes and a 100 year life would be 0.2 seconds. Further deflating our hubris, we have learned that we are not that special either. Darwin taught us that we are animals, Freud taught us that we are irrational, machines now outpower us, and just last year, Deep Fritz outsmarted our Chess champion Vladimir Kramnik. Adding insult to injury, cosmologists have found that we are not even made out of the majority substance. The MUH brings this human demotion to its logical extreme: not only is the Level IV Multiverse larger still, but even the languages, the notions and the common cultural heritage that we have evolved is dismissed as 'baggage', stripped of any fundamental status for describing the ultimate reality."
"The most compelling argument against the MUH hinges on such emotional issues: it arguably feels counterintuitive and disturbing. On the other hand, placing humility over vanity has proven a more fruitful approach to physics, as emphasized by Copernicus, Galileo, and Darwin. Moreover, if MUH is true, then it constitutes great news for science, allowing the possibility that an elegant unification of physics, mathematics, and computer science will one day allow us humans to understand our reality even more deeply than many dreamed would be possible."

Comments

[moonaysl.livejournal.com]

I actually helped Matt get his invitation to PI, so I know what he's been up to. I think he made a mistake choosing Caltech over PI for the postdoc, but I'm sure either way he's going to do well.

But ... he is doing something very different from what Anthony wanted me to do. If Anthony had given me that project, I probably would have stayed.

Anyway, Max was here at PI so I chatted with him for a while and then went to one of his dinners.

[moonaysl.livejournal.com]

oh yeah so at the dinner, he and a couple of other people tried to corner me and attack me for saying that if all the big problems in cosmology were solved, i might not continue in physics anymore. i think that's honest, and it's not such a horrible thing to say. but they were claiming that meant i wasn't a real physicist or something.

anyway, i think the whole thing is silly because i think their response was predicated on the belief that the big problems in cosmology will be solved on the time scale of a human lifetime, which i think is a bit ridiculous. that would mean solving quantum gravity, anthropic questions, dark energy, dark matter, and various galaxy evolution questions.

not likely to all happen while i am still around ...

[spoonless.livejournal.com]

I've always found it intriguing how different people are interested in different questions in physics. For the most part, I feel much the same way about particle physics... if we found out exactly what the theory was from here all the way up to the Planck scale, I'd probably quit physics. Even though there are a lot of unsolved problems in condensed matter, atomic physics, biophysics, etc.

For me, cosmology is mainly interesting because it gives us a way to test particle physics which is (in my opinion) where all the really fundamental foundational questions lie. In other words, I see the early universe as interesting primarily because it's the only time when things got hot enough to where low energy physics breaks down... something that would be too expensive to build an accelerator to do. But I'm aware that some (maybe most) cosmologists see things kind of in reverse. From things you've said, I gather that you're one of those who sees things in reverse from me, and that's fine... if that's where I thought the interesting questions were, I'd do the same thing.

[moonaysl.livejournal.com]

actually, probably where we differ is that i don't see a distinction between particle physics and cosmology, for the most part. obviously the details are different for people working with data ... like i am not concerned with the specific properties of the b particle or whatever. but for me, the fundamental questions in particle physics and the fundamental questions in cosmology are the same. and to me it is all cosmology because cosmology is about everything :)

this is something that lee and i regularly whine about other people not agreeing with :)

[spoonless.livejournal.com]

I see the biggest difference between you and I as a reductionist versus holist perspective. I see particle physics as encompassing everything, since everything reduces to particle physics at some level. I would not say that about cosmology, since there is no way to determine the microscopic physics from looking at the large-scale structure of the universe. However, if you're a die-hard holist, or are simply uninterested in the small-scale structure of things, then I suppose that view would make sense.

this is something that lee and i regularly whine about other people not agreeing with

I would agree with you that the boundries between cosmology and particle physics are getting less and less clear. And anyone who studies quantum gravity should certainly be familiar with both, as it involves both. But would lee smolin say that "cosmology is about everything"? That's really the part I disagree with the most. I would say cosmology is about gravity, and particle physics is about everything else... which is starting to include gravity too :)

[spoonless.livejournal.com]

oh, and I agree with you that there are probably many cosmological questions that will not be solved in our lifetime. dark matter I expect to be solved... the rest I think people will be arguing about for a long time. But more importantly, new questions will arise as the old ones are solved.