How does time changes at speed of light?

Answer 1

At speeds approaching the speed of light, time slows down in two ways, which in actuality are the same way observed from two frames of reference. If you're standing still and something is moving close to the speed of light relative to you, time is slower for it. If you're moving at close to the speed of light and everything else is standing still, time is still slower for everything else. Why? Because if you change reference frames from the objects that are standing still's point of view back to your point of view, then it is no longer you that is traveling close to the speed of light, but is in fact everything else that is.

This effect is called time dilation, and has been experimentally verified time and again. The equation to measure how much slower time passes for different reference frames is actually quite simple:

Δt' = Δt/√[1 - (v2/c2)], where v is the relative speed of what's moving compared to that of a stationary observer, c is the speed of light, Δt is the time elapsed by the observer's watch, and Δt' is the time that has elapsed by the object that is moving's watch.

Answer 2

If you watch a clock that is moving, you seeit run slower than it should.

The faster it moves, the slower you see it running. If it could move at the

speed of light, then you would see it stop.

The important part is that you're watching the clock move, and you see it

running slow. If somebody is traveling along with the clock, then he doesn't

see anything unusual. (Even though you also see his heartbeat slowing down.)

Answer 3

As an object approaches the speed of light, time appears to slow down from the perspective of an observer in a stationary frame of reference. This phenomenon, known as time dilation, is a consequence of the theory of relativity. As an object's speed approaches the speed of light, time dilation becomes more pronounced, eventually leading to the famous "twin paradox" where one twin ages less than the other after a journey at near-light speeds.