Relativity Allows Us To Measure Absolute Motion?

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?

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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