[SEQ RERUN] Where Experience Confuses Physicists
Today’s post, Where Experience Confuses Physicists was originally published on 26 April 2008. A summary (taken from the LW wiki):
It then turns out that the entire planet of Ebbore is splitting along a fourth-dimensional thickness, duplicating all the people within it. But why does the apparent chance of “ending up” in one of those worlds, equal the square of the fourth-dimensional thickness? Many mysterious answers are proposed to this question, and one non-mysterious one.
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This post is part of the Rerunning the Sequences series, where we’ll be going through Eliezer Yudkowsky’s old posts in order so that people who are interested can (re-)read and discuss them. The previous post was Where Physics Meets Experience, and you can use the sequence_reruns tag or rss feed to follow the rest of the series.
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One problem with Mangled World and similar explanations is that it just shows that the Born probabilities are actually a result of another true Born probability. For example, if some of those planes in that story get destroyed so that the probability of one surviving is proportional to the square of its thickness, you now have to wonder why you’re equally likely to be in each of the worlds.
Don’t get me wrong. Being equally likely makes a lot more sense than the likelihood being proportional to the square of the thickness, but the likelihood being proportional to the thickness would also make some sense.