[SEQ RERUN] Decoherence is Falsifiable and Testable

MinibearRex

Today's post, Decoherence is Falsifiable and Testable was originally published on 07 May 2008. A summary (taken from the LW wiki):

(Note: Designed to be standalone readable.) An epistle to the physicists. To probability theorists, words like "simple", "falsifiable", and "testable" have exact mathematical meanings, which are there for very strong reasons. The (minority?) faction of physicists who say that many-worlds is "not falsifiable" or that it "violates Occam's Razor" or that it is "untestable", are committing the same kind of mathematical crime as non-physicists who invent their own theories of gravity that go as inverse-cube. This is one of the reasons why I, a non-physicist, dared to talk about physics - because I saw (some!) physicists using probability theory in a way that was simply wrong. Not just criticizable, but outright mathematically wrong: 2 + 2 = 3.

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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 Decoherence is Simple, and you can use the sequence_reruns tag or rss feed to follow the rest of the series.

Sequence reruns are a community-driven effort. You can participate by re-reading the sequence post, discussing it here, posting the next day's sequence reruns post, or summarizing forthcoming articles on the wiki. Go here for more details, or to have meta discussions about the Rerunning the Sequences series.

Today's post, Decoherence is Falsifiable and Testable was originally published on 07 May 2008. A summary (taken from the LW wiki):

(Note: Designed to be standalone readable.) An epistle to the physicists. To probability theorists, words like "simple", "falsifiable", and "testable" have exact mathematical meanings, which are there for very strong reasons. The (minority?) faction of physicists who say that many-worlds is "not falsifiable" or that it "violates Occam's Razor" or that it is "untestable", are committing the same kind of mathematical crime as non-physicists who invent their own theories of gravity that go as inverse-cube. This is one of the reasons why I, a non-physicist, dared to talk about physics - because I saw (some!) physicists using probability theory in a way that was simply wrong. Not just criticizable, but outright mathematically wrong: 2 + 2 = 3.

The guide-wave contains everything. It's never collapsed, there's no fade-away as you recede from the worldline. The rules governing the guide-wave are exactly those of quantum mechanics, which don't mention any worldline. As far as the guide-wave is concerned, the worldline doesn't exist. It's a one-way connection. Right there we've got an oddity - the only entity in physics that would act without a reaction.

But setting that aside, the guide-wave implements the dynamics of branches not taken by the worldline. You see a nuclear decay? Nothing's halting the guide-wave from implementing the portion of that decay that occurred in a different direction at a different time. So it does. So you have the dead cat component as well as the live cat component. Wigner's friend is also still chilling out waiting for something to come up.

The guide-wave doesn't know where the worldline went, so it keeps on ticking, following the time evolution operator - and, if you choose to break it into components, meticulously working out the consequences of every one of those components - whether or not the worldline happens to be anything like that.

If you want me to think something doesn't exist, stop implementing its dynamics!

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