I am an Italian student of Cosmology and it is the first time I write
something in this mailing list. I didn't have the time to read all your
messages, so I don't know if my thought about multiverses is a new one or
not. Anyway I would like to propose you my reflection about this topic.

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.

But we can go further, considering another example. According to
Heisembergís principle of indetermination of time and energy, anything can
originate from nothing provided that it lowers itself soon after and
immediately desappears. For instance, there can be the effetcs of the
creation of particles and antiparticles living for very few moments and
soon after desappearing. But a macroscopic object might originate from
nothing, too: also in this case, it is just a very improbable event. Letís
consider then the following absurd thought. There may be an Hubble sphere
identical to ourís but in which, as soon as a living being on the Earth
mentions any objects, they appear immediately. Also in this case, the
above-mentioned event has some chances to take place, so that we are sure
that this event necessarly has to happen in infinite different places and
times.

 At this point we can draw some conclusions. Letís consider the case of an
observer (there must be infinite observers) living in a world in which a
gas never spread in all the available volume, or maybe it spreads only on
Friday. Even though moved by the same techniques and methodologies we
have, what would that observer think? May he be unlucky because he lives
in a part of the universe in which anything improbable happens regularly?
Well, this is a possible event, so infinite observers will think like
that. But as many infinite observers, reasoning as we would, would think
that entropy lowers. And what about the people living in a world in which
any time you mention anything, it appears immediately? Probably all the
infinite observers reasoning as we do would create a completely different
physics in which, among the other things, the principle of relativity
would not be valid. According to this principle, it is impossible to
overcome the speed of light; but if these people mention any objects and
they immediately appear (by chance!), the above-mentioned principle would
not be valid for them.

 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?

 At last we could object that all of this is admitted by our own model
and, if this absurdity really happened, we should only notice that we live
in a very improbable universe. But if it was true, it would be completely
unuseful for us to keep our mathematics and physics. For instance, if we
started, by chance, to obtain number 6 any time we throw a die, and if
this would be like that till the end of time, it would be unuseful for us
to go on considering the theory of probability as valid. There would be no
sense for us to think of having 1/6 of chances to obtain number 6, seen
that we would obtain it in any case. Unfortunately, it is obvious at this
point to draw the following conclusion: we should give up all the physics
we have got to know so far! But, once more, there is a nonsense. We have
proved that the whole physical system is wrong, but we have been able to
draw this conclusion because we have considered the hypotesis of applying
the physical system itself. But if it was wrong, the conclusions would be
wrong, too. Here we have the paradox.

Federico Marulli







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