Re: SpaceTime

Thomas Heger wrote:

>
Am Samstag000001, 01.06.2024 um 15:35 schrieb gharnagel:

>
Tom Roberts wrote:

>
Spacetime is a MODEL of spatial-temporal relationships observed in
the real world.
>
Tom Roberts

 I tend to think of physics that way, too, but I was watching this
episode of How the Universe Works called "The Mystery of Space Time"
and had a few issues with it:
 "Space-time is the fabric of our reality"
 "The universe is made of space-time"
 "Whatever the substance is, time and space bound together, that's
expanding
and creating the universe we see around us.  It's everything.

Space-time

is what the universe really is."

>
Well, sounds good!

Since we don't really understand what "space-time" is, we're not nailed
down to a particular mindset.  I believe that the equations of GR are
more
correct than the notion of space-time.
“spacetime is likely to be an approximate description of something
quite
different.” – Steven Carlip
That's not saying GR is absolutely correct, either.

I had written kind of 'book' about this idea and called it 'structured spacetime'.
>
This can be found here:
>
https://docs.google.com/presentation/d/1Ur3_giuk2l439fxUa8QHX4wTDxBEaM6lOlgVUa0cFU4/edit?usp=sharing
>
The idea behind it is quite simpel:
>
if GR and QM are somehow valid, there must be a way to bring both systems into a consistent relation.
>
My own approach was: start at the GR side and with some sort of real existing spacetime.

Or one could start from the QM side.  Might the virtual particle sea be
the basis of space-time?

The observed world is then the local 'subchapter', which is seen from where we (or any other observer) are placed.
>
This world has to have fewer dimensions than spacetime.

Aren't dimensions just a human way of looking at reality?  Anyway, I
have a hard time dispensing with them :-)  I would say that our
description
of reality probably needs more than four dimensions.

Spacetime must also be coordinates free and having no beginning and no
end.

If you look at the Schwarzschild metric:
ds^2 = (1 - 2GM/rc^2)c^2 dt^2 - dr^2/(1 - 2GM/r) - r^2 dOmega^2
and apply it to the whole universe, rs = 2GM/c^2 is MANY orders of
magnitude
larger than the purported size of the universe.  So the notion that
space-time
is limited to how far the expansion has proceeded is ludicrous.