The latter follows from that c is a limiting velocity in relativity ( with units in which c = 1 ).
2.
Another would put a radio-controlled device on an auto's throttle sensor, limiting velocity with a beam put out by a transmitter in a low-speed zone.
3.
Since astronomic measurements also contain additional assumptions like the unknown conditions at the emission or along the path traversed by the particles, or the nature of the particles , terrestrial measurements provide results of greater clarity, even though the bounds are wider ( the following bounds describe maximal deviations between the speed of light and the limiting velocity of matter ):
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