Re: the Ultimate Frame of Reference
- From: Tom Roberts <tjroberts@xxxxxxxxxx>
- Date: Sun, 26 Jun 2005 21:42:14 GMT
Steven wrote:
Supposedly there is no ultimate frame of reference.
Well, nobody has ever found one using local measurements, and our current theories of physics reflect this fact.
Globally, there quite clearly are at least two "ultimate frames of reference" -- the local dipole=0 frame of the CMBR, and the frame in which the distant galaxies are on average moving isotropically away. The first is moving about 370 km/s relative to the sun, and the second is moving fairly close to it. Note each of these depends on one's position in the universe, so they may not be "ultimate" in the sense you intend.
If two objects A and B are moving closer together, one could say A is moving toward B or B is moving toward A. It's all relative.
Not everything is "relative", but yes, you can validly describe this from either A's or B's point of view.
If A is moving toward B at .95c, the Doppler Effect will make A appear
to move at almost 20 times the actual speed.
Why would you think that? Note that B cannot measure A's speed geometrically, but must use the Doppler effect. Whether that is done using light emitted by A or using radar reflections from a round-trip B->A->B, the measurement will yield the answer that A is approaching B at 0.95 c. In analyszing this measurement, B must of course use SR.
Perhaps you are thinking of a similar situation in which A is far from B, and is moving close to but not exactly on the line-of-sight from A to B. If B simply measures the angular displacement of A's image over time and multiplies by the distance to A, B can obtain a speed of A that exceeds c in the direction PERPENDICULAR to the line-of-sight. This is caused by the rapidly decreasing distance to A, and is not really a speed exceeding c.
From A's perspective, B
will not be moving at more than twice the actual speed.
Why would you think that A's view of B would be different from B's view of A?
So it seems possible to determine which is moving and which is stationary. If that is true then it should be possible to determine what is Truly Stationary. The Doppler Effect could be used to find an Ultimate Frame of Reference. Is that true?
None of that is valid.
Tom Roberts tjroberts@xxxxxxxxxx .
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