On 18 Apr 2016, at 01:37, John Clark wrote:
On Sun, Apr 17, 2016 Bruno Marchal <[email protected]> wrote:
.
>> It's not just that you don't have to, you CAN'T do
theoretical physics from a viewpoint that CAN NOT EXIST because
the result would be ridiculous and useless.
>It does not exist physically, but it can still exist
mathematically, logically, etc.
If the multiverse contains everything that there is
"is" in which sense? Some multi or multimulti verses could be
everything physical that there is, but not everything needs to be
physical (exemple: the natural numbers, the complex numbers, the
differentiable varieties, the topological groups, the Kripke
relational structures, etc.).
many cosmologists try to figure out what could be the complete picture
of the physical reality, and some people serach this for the whole of
reality: physical and non physical.
then there is nothing logical about talking about what things would
look like for somebody standing outside the multiverse looking
back at it. It's a ridiculous waste of time, a complete dead
end.
Yet the term "multiverse" itself refers to such an object.
here you assume some realm which cannot belong to itself, which I
appreciate (actually), but logically, it is conceivable to have
structure containing themselves, and that is the case for some set
theories, where the universe of all sets is itself a set (like with
Quine's NF).
You are just choosing a special philosophy among an infinity which
suits your point, but that is not proving anything, and certainly not
a rebuttal of what I said.
>> if you start with a unphysical premise then you will reach a
unphysical conclusion and that does neither mathematicians nor
physicists any good.
> That would make disappear a lot of thought experience which
have play an important role in the advance in physics (in Galilee,
Einstein, Maxwell, etc.).
If the works of Galilee, Einstein or Maxwell were built
on unphysical foundations then today nobody would remember
their names, instead they are among the most famous physicists
of all time. In fact Einstein came up with relativity by trying to
imagine what the viewpoint would be of somebody moving at the speed
of light and discovered that viewpoint would produce logical
contradictions, and therefore CAN NOT EXIST.
No, he put itself at the place of a photon which does move at the
speed of light, and concluded to the laws of relativity and to the
fact that the photon can't have a mass non null. I think.
Many works of many physicists are built in part (at least) on
unphysical foundation: mathematics.
Bruno
John K Clark
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