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assuming a none moving system exist, can a point of reference be made to determine the relevant momentum we share with our star and our galaxy.

like the ligo experiment that detected gravitational waves, using two laser spread 4 kilometers long. a point of reference was made to determine the difference between our cosmic system and a ripple in peacetime. so an advance form of my question is.

could ligo instruments be used to determine a none moving system to our cosmic speed?

Qmechanic
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Miguel Guerrero
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2 Answers2

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There is no such thing as a none moving system. i.e., this question does not make sense if you want it to be answered with real Physics. The reason for the non-existince of a frame of reference at absolute rest is the Galilean Principle of Relativity, which states that any frame of reference is equally valid to the study of Mechanics. Although this may seem too "faithful" and unreliable, experimentation has agreed with this statement so far.

I am afraid I can't give an argument about the LIGO experiment itself, since it envolves General Relativity in its conception. However, most probably there is some effect related to Special Relativity which would make it impossible to detect any difference at all.

Níckolas Alves
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  • Incorrect. The non-moving frame does exist. It is known as the CMB frame (Cosmic Microwave Background) or the frame relative to the distant stars. – safesphere Sep 23 '17 at 19:02
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    @VictorStorm Careful! The CMB defines the average rest frame of all the matter in the universe, but this is no more special than any other reference frame. Velocities defined with respect to the CMB are not absolute velocities. – John Rennie Sep 23 '17 at 19:16
  • @JohnRennie: I don't think absolute velocity has a physical meaning in an infinite universe other than "the average rest frame of all matter in the universe". Does it? – safesphere Sep 24 '17 at 02:47
  • @VictorStorm Aren't you assuming that the Universe is infinite? Besides, an absolute velocity reference frame would be more important than other frames of reference, thus breaking the Principle of Relativity – Níckolas Alves Sep 24 '17 at 03:36
  • @NickolasAlves: Not my idea. In the current FLRW model, the universe is infinite, if space is flat. The space curvature has been measured by satellites as flat within a margin of error. So many believe the universe is and has always been infinite. Also the Principle of Relativity does not necessarily apply to the universe as a whole. – safesphere Sep 24 '17 at 03:50
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The speed of our galaxy relative to the non-moving frame of the Cosmic Microwave Background has been measures as 627 km/s:

CMBR dipole anisotropy

The answer to the second part is no, laser interferometers cannot be used to measure the absolute speed, because the speed of light does not depend on the speed of the source.

safesphere
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