Time stopped for a photon travelling at the speed of light?

In summary: However, the photon itself would not be in any of these frames. It would only be in the frame of reference from which it was traveling. So, as the photon approaches the speed of light, it would be in a shorter and shorter period of time. But, as it approaches the speed of light, it would also be in a frame of reference where time would stop for it.
  • #1
mildpiranha
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time "stopped" for a photon traveling at the speed of light?

Is time "stopped" for a photon traveling at the speed of light? Or is this a nonsensical question?
 
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  • #2


From the photon's point of view, it arrives at its destination immediately after leaving, in zero time. It can travel through the entire universe in no time at all, literally, which is logical since in its frame of reference it also travels zero distance.

From our point of view, obviously, it's just traveling at the speed of light so it may take millions of years to reach its destination.

It's a bit like the space traveler who leaves on a long space trip. As he accelerates to nearly the speed of light, space around him shrinks (in the direction of movement) so that distant galaxies suddenly become so close that he can reach them in a few years. Same thing for the return trip. However, as seen from the earth, he will have been away for millions of years. In fact, the Earth may not even exist anymore when he tries to come back.

The photon is just the same, only it travels AT the speed of light, so lengths are shrunk to zero and travel takes no time at all, in its frame of reference.

If I'm not mistaken, this also means a photon, or any other particle traveling at the speed of light, will never decay since it doesn't have time to do so.
 
  • #4


This is really a nonsensical question, since the rest frame of a photon is not a valid reference frame.

As the article posted by michelcolman points out, we can ask what happens as we get closer and closer to the speed of light. This question makes sense, since all the reference frames we would be in would be valid.
 

1. How can time stop for a photon?

According to Einstein's theory of relativity, time is relative and can be affected by an object's speed and gravitational fields. As the speed of light is the fastest possible speed, time essentially stops for a photon traveling at that speed.

2. Does this mean that time does not exist for a photon?

No, time still exists for a photon, but it experiences it differently than other objects. Time is a measurement of change, and since a photon does not experience any change in its speed or direction, it appears to not experience time.

3. How does this concept of time for a photon affect our understanding of the universe?

Our understanding of the universe is shaped by the fact that the speed of light is constant and that time can slow down or stop for objects traveling at that speed. This concept is crucial in understanding the behavior of objects at the speed of light, such as stars, galaxies, and even the expansion of the universe.

4. Can anything else experience time stopping?

No, only objects that can travel at the speed of light or reach it can experience time stopping. As it is physically impossible for matter to reach the speed of light, time can only stop for objects like photons, which are massless particles.

5. Is there any evidence of time stopping for a photon?

While we cannot directly observe time stopping for a photon, there is evidence of its effects. For example, cosmic rays, which are high-energy particles traveling at almost the speed of light, have a longer lifespan than expected due to time dilation, a consequence of time stopping for objects at the speed of light.

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