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Boltzmann’s brains

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• Is the world eternal? YES
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• Is hell other people? YES
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• Are numbers real? NO
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Here is a bit of material for philosophical reflection, from yesterday’s NYT.

The basic idea, as I understand it, is this. Scientists think that the universe’s level of disorder, as a rule, never decreases. What this means is that things decay, disperse, and lose any non-uniform distribution of qualities over time. You can’t unscramble an egg; you can’t unswirl the cream in your coffee; you can’t make the universe, as a whole, warm up, or even stay the same temp. This is the second law of thermodynamics: disorder (entropy) never decreases.

That’s a law for the universe as a whole.  It doesn’t preclude little isolated burps of increasing organization, so long as, over the long haul, there is a net loss in order. So the universe can tolerate isolated exceptions to the second law. But, since nature seems to always choose the simplest path, these exceptions should be kept to a minimum.

Here comes Boltzmann. Suppose the universe had two choices. One is to allow the great big exception to the second law known as the history of human evolution and civilization. The second is to allow the comparatively minor exception which would have you spontaneously come into existence, for a few seconds, with all the memories, perceptions, and expectations you are experiencing right now. Case number two is the smaller breach of entropy. So we should believe that that’s the truth: you think you are part of a great big exception to entropy, but you’re not. You’re something like a one-second-old brain in a vat.

What do you think?



  1. Mike says:

    Well said, Vince.

    This conversation reminded me of this quote from a random “fundamentalists say the darndest things” site:

    One of the most basic laws in the universe is the Second Law of Thermodynamics. This states that as time goes by, entropy in an environment will increase. Evolution argues differently against a law that is accepted EVERYWHERE BY EVERYONE. Evolution says that we started out simple, and over time became more complex. That just isn’t possible: UNLESS there is a giant outside source of energy supplying the Earth with huge amounts of energy. If there were such a source, scientists would certainly know about it.

    You’d hope the NY Times would be better but I guess that’s the world we live in.


  2. Huenemann says:

    Well, maybe I misrepresented the article; if you’re interested, have a look yourself.

    But I do agree with Vince that the argument is hogwash. To me, it seems that the sudden appearance of a brain with memories intact would be a violation of 2ndLaw; to make it not be a violation, you’d have to embed that appearance in a much bigger system of causes and conditions and energy which, as a whole, is gaining entropy. Et vioila! Our world.


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