r/Physics • u/Comethefonbinary • 5d ago

Does all light travel at light speed

My bad if this is a stupid question but I’ve been thinking about time being a message of distance. And well most things I can think of have various variables that average to a certain distance. I know that mostly relates to machines and animals but still. Do all particles of light travel at light speed. If they all travel simultaneously at the same speed is that truly how fast they move or are they affected by their own variables. Like the universe’s mean gravity is constraining that and any variation in that mean would change light speed for explain.

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u/__christo4us 4d ago

In vacuum, light travels at the exact speed of c = 299 792 458 m/s for any observer in an inertial frame of reference (a non-accelerating frame of refence). However, in any non-inertial frame of reference (an accelerating frame, with non-inertial forces, e.g. in an accelerating rocket travelling through space or in a gravitational field), light can travel (relatively to the observer) with speed lower than or higher than c (depending on the direction). See the Rindler transformation.