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roystgnr comments on Rationality Quotes February 2014 - Less Wrong
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Laws of physics are not some deep mysterious algorithms built into the universe when it was created, they are human approximations of the infinite complexity we observe. As long as the universe is at least somewhat predictable and not completely random, it is possible to construct a series of increasingly accurate ways to predict its behavior. If the universe included predictable dragons after half a second, these approximations would, too. In fact, the Navier Stokes equations happen to describe so many dragons, there is still an open Millennium problem related to them. If the dragons appear unpredictably... well, then, it's just like the universe we already live in, where the unpredictability is everywhere (if you doubt that, please tell me the results of tomorrow's lottery).
So no, our universe is not particularly simple. It's mostly, to quote a historian, "one damned thing after another".
Perhaps "Navier-Stokes" and "complexity" and such are (ironically) overcomplicating things. Let's try to simplify:
I just walked out of a room with blue walls.
Is there a mathematically consistent universe in which, when I walk back in, the walls will have spontaneously turned red? Yellow? Plaid? (hint: for a universe with a set of physical rules S, is there anything mathematically inconsistent about the set "S union that-room-spontaneously-turns-red-in-2-minutes"?)
If all mathematically consistent universes exist and there is no special probability distribution preferring some over others, what subjective probability should I assign to the expectation that I will see the same shade of blue walls?
In the real world, what subjective probability should I assign?
If the previous two answers are different (for example, if the first probability is epsilon and the second is one minus epsilon...), why is that so?