Hello Frederico,

I've recently been taking part in a discussion on very similar lines on the Fabric of Reality mailing list (yahoo groups).

Federico Marulli wrote:

My reasoning is rather simple. Dealing with an infinite level 1
multiuniverse, if an event, even an improbable one, doesn't violate any
pshysical laws, it necessarly has to happen infinite times and in infinite
different points of the space.
So we can try to reason upon some examples which has a meaning from a
physical point of view. For instance, we can think about the second
principle of thermodynamics, according to which the entropy of a closed
system necessarly has to increase. That means that, for instance, a gas
put into a container of volume V will tend to spread by occupying all the
available volume. This way we get the most possible disorder and the state
is the most probable. Anyway the state in which all the gas is firmly in a
v < V volume is not forbidden by thermodynamics; it is just a rather
improbable state. But this event, having some chances to take place, has
to happen in infinite places and times in our multiverse. So there will be
infinite Hubble spheres in which everything happens exactly as in our own
sphere, but in which any time you put a gas into a container, it will
never occupy the whole volume. At the same time, there will be infinite
spheres in which some day the gas will occupy all the volume and some
others not. And so on.


Yes, this is predicted to happen (in very rare universes) in the Many Worlds Interpretation (MWI). It's also predicted to happen under the Copenhagen Interpretation (CI), you'd just have to wait a very long time to expect to see such a violation of the 2nd law of thermodynamics.

<snip>

From all these examples we should deduce that, if all the infinite
observers we have considered took advantage of the same approach we have,
they would obtain very different interpretations. So the model seems to
admit in itself the chance of being wrong. It is consistent with its
foundamental hypotheses the fact that it is inconsistent. So here we have
the paradox. But shall we put into discussion our experimental method just
because some unlucky observers are not in the condition to understand the
universe and the way it works?

To answer this question I have tried to go even further with my
reflection. I believe we have no reason to think of being privileged
observers just because we observe the universe moving according to our
physical laws. Moreover, physics has been formunlated just starting from
our observations, so it is clear that our models come out to be consistent
with them. If these observations were not like that, we would discard
them. But the same thing would be valid for all the other infinite
observers and any of them could think of being privileged. Besides, from
one day to another, we could also realize that all our models are no
longer valid. What would happen if we lived in an Hubble sphere in which,
by chance, entropy began to lower all of a sudden?


We can call these universes where strange things that seem forbidden by our statistical laws of physics (which are not fundamental) happen regularly through shear chance 'magical'. I believe your question could be rewritten, is there any evidence that we are not living in such a 'magical' universe ourselves?

You are quite right that any particular physical law you could construct *could* be the result of observing quantum statistics which have been skewed in one way or another. For instance, you could be in a 'magical' universe where gases don't expand in line with the predictions of our statistical mechanics/thermodynamics. Instead, you would draw up your own set of laws to describe this behaviour, assuming that the deviations happen in a systematic way. Or you could be in another 'magical' universe where even fundamental particles obey totally different equations of motion, as a result of skewed sampling on every microscopic observation of the wavefunctions concerned.

In order to formulate these laws, the deviations would have to be systematic. Universes admitting such 'magical' laws would be very much rarer than those where the deviations do not permit systematic modelling to occur.

The evidence that we are not in such a 'magical' universe is this. Though our laws describing the behaviour of gases etc. were originally derived from observations of large amounts of gases - macroscopic investigation - we have since found that they are 100% bconsistent with our observations of single particles of gas - microscopic investigation.

In 'magical' universes, we would not expect this consistency. Observations of large amounts of gas would not be consistent with measurements made on individual particles in the vast majority of these universes. The fact that these two sets of laws of physics are consistent indicates that we are not in a 'magical' universe with very high confidence - because if we were in a 'magical' universe we would be far more likely to have inconsistent macroscopic and microscopic physics.

I should point out that there does remain a vanishingly small possibility that we could be in one of the extremely 'magical' universes where both macroscopic and microscopic laws of physics are skewed in a mutually consistent way, however given the tiny probability of this being the case I think it is quite safe to ignore it.

Hope this helps,

Matt.

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When God plays dice with the Universe, He throws every number at once...

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