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ghostowl657 t1_j1j7bzk wrote

Reply to comment by EGP22 in Are people in the international space station experiencing time faster than us? by [deleted]

Your misunderstanding comes from your thinking there is such a thing that "actual time has elapsed". Not everyone's second ticks at the same rate, and there's no way to say that mine is more valid than yours. But to the person actually on the ship they still feel like time moves "normal" since every physical process is dependent on the local flow of time.

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EGP22 t1_j1j8if2 wrote

Is not a second a unit of measurement and constant, thus one second is equivalent anywhere? This is the concept that I don’t understand.

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dazb84 t1_j1jw1nm wrote

It is, in the same way that light speed is the same for all observers. For example you travelling at the speed of light and turning on a flashlight results in the light emitted from the flash light moving forwards at lightspeed relative to you and we know that you can't go 2x the speed of light which is what would be happening from a 3rd perspective.

So the only way to reconcile this impossibility and maintain causality throughout the system, since nothing can go faster than light relative to any observer, is with time dilation.

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ghostowl657 t1_j1j8pvs wrote

It is a consistent unit of measure, but what everyone measures as a second is relative. The same thing is true for lengths.

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