Re: Relativity Allows Us To Measure Absolute Motion?


"Simon G Best" <simon.g.best@xxxxxxxxxxxxxx> wrote in message
news:S9-dnbdeFpp3ltLanZ2dnUVZ8u-dnZ2d@xxxxxxxxx
Hello!

Thinking about the supposed lack of absolute motion one day, I thought:
Hang on, what about the cosmic microwave background radiation (CMBR)?
Isn't that a dead give-away?

Nope. The POR says the laws of physics are the same. That does not mean
you can't tell a frame that have been painted red from one that isn't. The
same with the CMBR - the fact the laws of physics must be the same does not
imply you can't tell a frame at rest wrt the CBMR from one that isn't. To
easily see this, since the CBMR is EM radiation, it can be readily screened
out. An aether, if it existed, could not, without drastically changing the
laws of physics as we currently know them eg EM would be out the window so
matter could not exist since electrons and protons are charged.

Thanks
Bill


The CMBR does a very good impression of being ideal black-body radiation.
What's more, there are only very slight variations in its apparent
temperature across the sky - except for a rather prominent bit of Doppler
shifting, that is. Measure its temperature in different directions, and
it's as if you can measure your own motion relative to the source of the
CMBR (the surface of last scattering, if I remember correctly). But
doesn't this look very much like detectable, even measurable, absolute
motion?

It puzzled me. Here we are in a universe which, we are told, does not
have absolute motion included. And yet, when we measure such things as
mean velocities of galaxy clusters, the apparent CMBR temperature in
different directions, and stuff like that, there really does seem to be
something very much like a special velocity. It's as if there is such a
thing as absolute rest.

How, in a universe free of such absolute motion, could we end up with such
a special, absolute-rest-like velocity emerging? It looks suspiciously
like the universe is blatantly contradicting the idea that absolute
motion's undetectable!

I also pondered the shape of the universe, and ended up considering a
simple, contrived scenario.

Imagine a flat space-time, with two dimensions of space, and one of time.
Imagine, also, that the space is toroidal, like the surface of a ring
doughnut, so that it's like the screen of that Asteroids video arcade game
from years ago. (The screen is rectangular, and when you go off the left
hand side, you come back on the right hand side, and when you go off the
top, you come back on the bottom. It wraps around in those two ways.)
Keeping it simple, this space-time is flat, Euclidean, no gravity, no
curvature. We can just use Special Relativity.

Now imagine laying down a line of measuring rods, all of equal length,
just as Einstein might. Eventually, because of the orientation of these
rods, we end up back where we started. We also place synchronised clocks
at the ends of these measuring rods, where they meet.

Now, next to that line of rods and clocks, we move at high speed relative
to them, in a parallel direction. As we move, we lay down rods and
clocks, like before, but moving with us. Eventually, we'll wrap round,
and get back to where we started.

Lorentz transformations and all that, and we find that we needed more of
the moving rods before we got back to where we started. Also, while all
the moving clocks were synchronised relative to the moving rods as we laid
them down, we find that the last clock and first clock are unsynchronised
when compared via the last rod. But, when comparing those two clocks the
long way round, we find they're synchronised.

So what?

Well, there's one, special velocity in that space-time at which the
minimum number of rods would be needed, and at which all such clocks would
be synchronised, regardless of which route along the rods they're compared
along.

While Special Relativity itself doesn't provide any such special velocity,
the combination of Special Relativity and a suitable space-time does
involve such a special velocity. It's as if Special Relativity itself
isn't enough to establish absolute motion, but the combination of Special
Relativity and a suitable space-time can establish something that looks at
least a bit like some kind of absolute motion. What's more, Relativity
enables us to measure velocities relative to that special velocity.

Am I now a heretic? :-D

But seriously, I then wondered if the combination of General Relativity
with the space-time of our cosmos would similarly give rise to a special,
absolute-rest-like velocity, and if this might explain the apparent
detectability of something like absolute motion courtesy of the CMBR.

I also Googled, and found that a Dr Evan Harris Walker had already looked
at this. For example, there's the following mailing list post:-

http://listserv.arizona.edu/cgi-bin/wa?A2=ind9905&L=quantum-mind&P=2898

I gather he's now deceased. I did have what I gathered was his website
bookmarked, but that site's now gone :-(

To me, absolute motion seemed, well, not as neat as a lack of absolute
motion. I thought more about it, and the following occurred to me.

Overall, with the expansion of the universe, it seems there's no,
particular, special rest-like velocity for the whole universe. Instead,
it seems to be a different rest-like velocity at each point in space. That
still looks like some kind of absolute motion, though. There's no
special, central point in space for the whole universe, though, and so
there's still no special, rest-like velocity for the whole universe.

It seems that there's no universally special velocity, and there's no
universally special point in space, but there is a special point for each
velocity (where that velocity is rest-like), and there is a special,
rest-like velocity for each point. It's kind of like having it both ways
with whether or not there's absolute motion, depending on what we define
"absolute motion" to mean.

So, my questions are:-

1. Have I gone wrong somewhere?

2. I'd imagine this is nothing new, so: does this sort of thing have a
name?

3. What else should I be asking about it?

:-)

--
Simon G Best
...
What happens if I mention Leader Kibo in my .signature?


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