Is Movement Actually Relative?

[gravity4themasses]

TL;DR

Is movement really only relative to other particles or is movement relative to one’s own reference frame?

I have been struggling with this. We have been told that movement is completely relative, that no particle has a speed in its frame, only a relative speed to other particles. But consider the following.
Ceers-2112 is a galaxy about 11.2BLY away and dark energy is moving that object at .8C away from your coordinate. While at rest you can look at any angle and see objects at 11.2BLY move away at .8C. Now imagine accelerating to .8C in your own frame towards ceers-2112. Now you have zero Doppler shift with respect to that distant patch of your spacetime which is accelerating under dark energy. This makes your dark energy gradient per Hubble’s Constant asymmetrical. You have matched recessional Doppler shift of your frame and naturally you adopt that same clock rate. Everyone you whiz by will agree that you and ceers-2112 have the same amount of redshift, 3. They will also agree you have the same clock rate as ceers-2112.

Dark energy gradient is unique to each particle, every perspective is different from every other particle. And when you “move” you match recessional velocity with your own frame’s dark energy gradient per Hubble’s constant and spacetime moves around you while you are always at rest. If you are matching recessional Doppler shift from the dark energy gradient unique to your own frame, then movement being relative to one’s own frame seems reasonable.

 

[renormalize]

...Ceers-2112 is a galaxy about 11.2BLY away and dark energy is moving that object at .8C away from your coordinate. ...
...Dark energy gradient is unique to each particle, every perspective is different from every other particle. ...

Please cite one or more credible technical references that support these claims about "dark energy" and its "gradient".

 

[PeterDonis]

Ceers-2112 is a galaxy about 11.2BLY away and dark energy is moving that object at .8C away from your coordinate.

No, the overall expansion of the universe is moving that object at .8C away from us on Earth. Dark energy is contributing to the acceleration of that expansion, but it is not the only cause of the expansion itself.

While at rest you can look at any angle and see objects at 11.2BLY move away at .8C.

Actually, if you're here on Earth, you can't, because Earth is not at rest relative to a frame in which the universe is homogeneous and isotropic. For example, the CMBR as it is actually observed here on Earth is not isotropic. Astronomers usually correct for this when quoting numbers without mentioning that they are doing so, but for the scenario you are posing here, it's important to understand that "you" cannot be at rest here on Earth, "you" must be moving at, IIRC, about 600 km/sec relative to Earth in order to see the universe as isotropic around you.

Now imagine accelerating to .8C in your own frame towards ceers-2112.

"In your own frame" is vague. A precise statement would be something like: you drop a beacon before accelerating, and then accelerate in the direction of ceers-2112 until you are moving at .8C relative to the beacon.

Now you have zero Doppler shift with respect to that distant patch of your spacetime which is accelerating under dark energy.

No, this is word salad. A Doppler shift is not relative to a "patch of spacetime". It's relative to a specific light source. In this case, ceers-2112.

You are making other errors with regard to Doppler shift as well; see further comments below.

Also, as already pointed out, dark energy is not the only factor contributing to the expansion of the universe, and your focus on it is misplaced.

But even with that...

This makes your dark energy gradient per Hubble’s Constant asymmetrical.

...this is wrong. Dark energy density is constant everywhere in the universe, in space and in time. Changing your state of motion does not change that.

It is true that you will see the universe around you as highly anisotropic (much more so than we here on Earth do). For example, you will see a huge variation in the temperature of the CMBR with direction. And you will see various relativistic effects on the light coming to you from distant stars and galaxies. None of this in any way changes the fact that "movement is relative"--these effects are all due to your velocity relative to all those other parts of the universe.

You have matched recessional Doppler shift of your frame and naturally you adopt that same clock rate.

Wrong. Spacetime is not flat, and intuitions like this that only work in flat spacetime do not work in this scenario.

Even calling the redshift you observe "Doppler shift" is not correct. It's cosmological redshift. And cosmological redshift tells you nothing about the speed of the distant object relative to you (pop science statements to the contrary notwithstanding--though it is very sad indeed that this crucial point is so often misrepresented). Instead, it tells you by what factor the universe has expanded since the light you are seeing now from that object was emitted: a redshift of $z$ means an expansion factor of $1 + z$. The "recession speed" that astronomers like to quote is not an actual relative speed in the sense of SR. It's just a number that represents a coordinate-dependent quantity which happens to have the units of speed, but with no direct physical meaning as a speed (the direct physical meaning is the expansion factor as just noted).

So your entire scenario is based on a misconception.

 

[PeterDonis]

your entire scenario is based on a misconception

And with that, this thread is closed.