Monday, November 30, 2009

Quote Of The Day

Max Tegmark is a prominent cosmologist at MIT. (It turns out he is a really nice person as well.)

He has the ultimate Occam's Razor quote for defense of a multiverse.   Occam's Razor being the idea that, given two theories that seem to be equivalent up to experiment, choose the simpler theory:
A skeptic worries about all the information necessary to specify all those unseen worlds. But an entire ensemble is often much simpler than one of its members. This principle can be stated more formally using the notion of algorithmic information content. The algorithmic information content in a number is, roughly speaking, the length of the shortest computer program that will produce that number as output.
For example, consider the set of all integers. Which is simpler, the whole set or just one number? Naively, you might think that a single number is simpler, but the entire set can be generated by quite a trivial computer program, whereas a single number can be hugely long. Therefore, the whole set is actually simpler.
Similarly, the set of all solutions to Einstein's field equations is simpler than a specific solution. The former is described by a few equations, whereas the latter requires the specification of vast amounts of initial data on some hypersurface. The lesson is that complexity increases when we restrict our attention to one particular element in an ensemble, thereby losing the symmetry and simplicity that were inherent in the totality of all the elements taken together.
In this sense, the higher-level multiverses are simpler. Going from our universe to the Level I multiverse eliminates the need to specify initial conditions, upgrading to Level II eliminates the need to specify physical constants, and the Level IV multiverse eliminates the need to specify anything at all... A common feature of all four multiverse levels is that the simplest and arguably most elegant theory involves parallel universes by default.
To deny the existence of those universes, one needs to complicate the theory by adding experimentally unsupported processes and ad hoc postulates: finite space, wave function collapse and ontological asymmetry. Our judgment therefore comes down to which we find more wasteful and inelegant: many worlds or many words. Perhaps we will gradually get used to the weird ways of our cosmos and find its strangeness to be part of its charm.
Now, don't get me wrong, this is a very speculative quote.  I am not trying to sell this as mainstream at all.

However, it is one of the more interesting applications of Occam's Razor I have seen. :)


  1. Is this similar or can it be applied to probablility? The odds of drawing a specific hand of 10 cards is unlikely but drawing 1 of any possible hand of 10 cards is 1.

  2. It is true that the simplest thing is not obvious, but a multiverse is quite easy to imagine because there can be a lot of variations which could be taken into account.

  3. Ooh, that's lovely!

    Of course, there are many other possible objections to many worlds, but that's an elegant parry of the complexity attack.


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