[SEQ RERUN] Reductionism

MinibearRex

Today's post, Reductionism was originally published on 16 March 2008. A summary (taken from the LW wiki):

We build models of the universe that have many different levels of description. But so far as anyone has been able to determine, the universe itself has only the single level of fundamental physics - reality doesn't explicitly compute protons, only quarks.

Discuss the post here (rather than in the comments to the original post).

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 Qualitatively Confused, and you can use the sequence_reruns tag or rss feed to follow the rest of the series.

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Today's post, Reductionism was originally published on 16 March 2008. A summary (taken from the LW wiki):

We build models of the universe that have many different levels of description. But so far as anyone has been able to determine, the universe itself has only the single level of fundamental physics - reality doesn't explicitly compute protons, only quarks.

you cannot construct a particular configuration of subatomic particles that will fly, rather than bark or crawl, using just the laws of QFT.

Saying "you cannot" is awfully gutsy. Are you familiar with renormalization groups? They're a mathematical tool for getting high-level laws out of low-level laws. The only theoretically unsolved problem I know of between QFT and predicting planes is the prediction of a periodic solid as the ground state of your structural metal, though there are probably a few more.

Saying "you cannot" is awfully gutsy.

True, let's say that I'd bet my house on it not being done in my lifetime.

Are you familiar with renormalization groups?

Yes, in the HEP context.

They're a mathematical tool for getting high-level laws out of low-level laws.

Not quite. You can use renormalization to help explain some of what you observe at lower energies from a HE model point of view. I am yet to see an RNG prediction of a new low-energy effect, though I suppose it might happen for one-level-up problems, but not for any kind of multi... (read more)