This has been an interesting thread so far, but let me bring it back to
topic for the Everything List. It has been assumed in most posts to this
list over the years that our current state must be a "typical" state in some
sense. For example, our world has followed consistent laws of physics for as
long as anyone has been able to determine - the old "no white rabbit worlds"
observation. In the face of ensemble type theories such as the MWI of QM,
this is seen as presenting a problem: if "anything that can happen, does
happen", why does our experience of the world include only a very limited,
orderly subset of this "anything"?
There have been many attempts to answer the above question, eg. see Russell
Standish' paper "Why Ockham's Razor?" But does our current orderly world
imply that most possible worlds are orderly? It seems to me that there is an
asymmetry between (a) what we can expect for the future, and (b) what we can
deduce about the probability implicit in (a) from what actually does happen.
Suppose that according to X-Theory, in the next minute the world will split
into one million different versions, of which one version will be the same
sort of orderly world we are used to, while the rest will be worlds in which
it will be immediately obvious to us that very strange things are happening,
eg. dragons materialising out of thin air, furniture levitating, the planet
Jupiter hurling itself into the sun, etc. I think it is reasonable to expect
that if X-Theory is correct, we will very likely see these bizarre and
frightening things happen in the next minute.
Now, here we are, a minute later, and nothing bizarre has happened after
all. Does this mean that X-Theory is probably wrong? Perhaps not. After all,
the theory did predict with 100% certainty that one version of the world
will continue as before. The objection to this will no doubt be, "yes, but
how likely is it that WE end up in that particular version?" And the answer
to this objection is, "it is 100% certain that WE end up in that particular
version; just as it is 100% certain that 999,999 copies of us end up in the
bizarre versions". Those 999,999 copies are not continuing to type away as I
am, because they are running around in a panic.
The above is simply a version of the Anthropic Principle as applied to
intelligent life in the universe. A particular ensemble theory may predict
that it is overwhelmingly unlikely that a particular universe will allow the
development of intelligent life. Does the fact that we are here, appparently
intelligent and alive, count as evidence against that theory? No, because
the theory predicts that although unlikely, it is certain to happen in at
least ONE universe, and obviously that universe will be the one we find
ourselves in.
Stathis Papaioannou
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Received on Thu Oct 07 2004 - 20:23:46 PDT