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The required characteristics of a standard is consistency from time to time. Its value in the past should be the same as its value in the future.
Quote from: hamdani yusuf on 30/04/2024 22:18:20The required characteristics of a standard is consistency from time to time. Its value in the past should be the same as its value in the future.As far as I am aware, there has been no good evidence to date that the speed of light in a vacuum has changed over the lifespan of the Universe. All that has changed is the precision with which we have measured it.
Even making good standards is just an instrumental goal, serving to help achieving the common terminal goals among the users of the standards.
Perhaps it's because the speed of light is defined to be a constant, and spacetime is defined so that its expansion doesn't change the speed of light.
Not so. If the speed of light had changed over the course of the Universe's history, we would be able to see differences in the behavior of distant galaxies and stars compared to closer galaxies and stars.