Monday, March 24, 2014

Aaronson says Tegmark devoid of content

Scott Aaronson reviews Max Tegmark's book on the Mathematical Universe Hypothesis (MUH):
Briefly, I think it’s a superb piece of popular science writing — stuffed to the gills with thought-provoking arguments, entertaining anecdotes, and fascinating facts. I think everyone interested in math, science, or philosophy should buy the book and read it. And I still think the MUH is basically devoid of content, as it stands. ...

Putting the two points [about the laws of physics] together, it seems fair to say that the physical world is “isomorphic to” a mathematical structure — and moreover, a structure whose time evolution obeys simple, elegant laws.   All of this I find unobjectionable: if you believe it, it doesn’t make you a Tegmarkian; it makes you ready for freshman science class.

But Tegmark goes further.  He doesn’t say that the universe is “isomorphic” to a mathematical structure; he says that it is that structure, that its physical and mathematical existence are the same thing.
I am glad to see that Aaronson does not believe in any of Tegmark's multiverses, but this review is nonsense.

When Tegmark says that the universe is a mathematical structure, that is just a shorthand for saying that the universe is isomorphic to a mathematical structure. So Aaronson takes two versions of the same statement, accepts one as trivially obvious and rejects the other one.

And why is Aaronson promoting a book whose main point is such a dopey idea?

I think that the MUH does have content, because I believe that it is false.

The public face of physics is largely shaped by popular books written by big-shot MIT professors like Tegmark and Aaronson. I expect more from these guys. Tegmark apparently bet $100 on the success of BICEP2. Maybe he could be explaining that to the public.

Aaronson responds:
As far as falsifiability goes, please help me understand how the string landscape is any more falsifiable than MUH?

Well, the string landscape has well-known falsifiability issues too! But if (hypothetically) you could build a particle accelerator the size of the universe, capable of reaching the Planck scale, then you could at least imagine doing experiments that would definitively confirm or rule out string theory. Whereas even with such resources, it seems to me that the MUH would remain just as empirically inaccessible as before.
This is like talking about the equipment to count how many angels can dance on the head of a pin.

Update: Here is another answer:
Nex Says: English language describes the World so well that it cannot be a coincidence. And it’s not. But the right conclusion is not that the World and the English language are one and the same thing, rather the language was tailored to serve that purpose.

Same thing with mathematics.

Scott Says: Nope, try again! The view that analogizes math to the English language seems totally unable to account for things like complex numbers, linear algebra, Riemannian geometry, or group representations, which were all developed decades or even centuries before anyone thought of any applications to physics, but then turned out to be exactly what physicists needed.

Which English words were coined decades or centuries before anyone needed them?
That is an argument, but thousands of English words were coined before being applied to physics. Those math concepts were all needed when they were developed, just not needed by physicists. So both English words and math concepts were developed long before being applied to physics.

1 comment:

  1. The ultimate scientific theory bullshit detector is 'hypostatization'. If your theory of 'whatever' depends upon a theoretical abstraction somehow becoming (hand waving magic) an actual physical anything to allow it to function, it's a fallacy and it's wrong. In essence, to use a counterfactual, 'if wishes were horses then beggars would ride', but wishes are NOT horses or even remotely close to horses (wishes = wistful abstraction, horses = actual things), and so beggars hoof to speak. Math is not physical reality, it is a descriptive abstraction that like all abstractions requires a mind to reside within in order to have any meaning, purpose, or function, exactly like any other human language. The question I have is, why do mathematicians feel so qualified to spout such nonsense about physical extension and existence when they don't seem to even know what the words actually mean? Confusing or conflating abstraction and actuality is pretty sloppy conceptualization. If you have sloppy language skills, your mathematical ability will be severely hindered by your mind's inability to logically manage and manipulate abstract concepts which are necessary preconditions before further abstraction can be extrapolated.