Comments on: Short Explanations of Observations in Physical Worlds https://ordinaryideas.wordpress.com/2011/12/15/short-explanations-of-observations-in-physical-worlds/ As advertised Wed, 17 Dec 2014 04:51:36 +0000 hourly 1 http://wordpress.com/ By: jsteinhardt https://ordinaryideas.wordpress.com/2011/12/15/short-explanations-of-observations-in-physical-worlds/#comment-31 Tue, 24 Jan 2012 06:57:03 +0000 http://ordinaryideas.wordpress.com/?p=21#comment-31 What do you mean by “scored by their average performance in our universe”? Is there some implicit prior in the background?

]]> By: paulfchristiano https://ordinaryideas.wordpress.com/2011/12/15/short-explanations-of-observations-in-physical-worlds/#comment-29 Mon, 23 Jan 2012 20:25:52 +0000 http://ordinaryideas.wordpress.com/?p=21#comment-29 It requires a huge amount of randomness to pick you out of the universe (as opposed to one of the astronomically many “near misses” residing in nearby Everett branches). This fact provides some intuitive resistance to to the claim that saying “pick an observer from a universe with simple physical laws” is a good way to describe your experiences.

But my point was that conditioning this distribution on agreement with your observations so far is actually (and tautologically) the best predictor for your future observations, scored by their average performance in our universe. Consequently, in the long run this is going to be the shortest description of most observation sequences in our universe.

Of course, because so much randomness is used, these descriptions aren’t actually very short at all. So it is very hard to rule out the possibility of shorter descriptions for particular sequences of observations (except by this sort of argument in the aggregate).

]]> By: jsteinhardt https://ordinaryideas.wordpress.com/2011/12/15/short-explanations-of-observations-in-physical-worlds/#comment-28 Sun, 22 Jan 2012 04:02:11 +0000 http://ordinaryideas.wordpress.com/?p=21#comment-28 I don’t understand the last bit of the post:

“it is now more likely that a sequence won’t contain enough surprises to rule out simpler models.

Returning universe, and consider a human’s sequence of observations. Even fixing the laws of physics, all you can conclude from your observations is that you belong to the reference class of observers who have shared your experiences (and your cognitive architecture etc.)”

Can you clarify?

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