If you're traveling at the speed of light, then time stops

In summary, the conversation discusses the misconception that time stops when traveling at the speed of light. It is clarified that this is not possible and that time appears to slow down when traveling close to the speed of light. The confusion is resolved by explaining that the perception of time is relative to one's speed and position.
  • #1
gamow99
71
2
I think my understanding of STR might be wrong. I was watching a documentary where they said that if you're traveling at the speed of light then time stops. Now let's say I'm traveling through intergalatic space from the Milky Way to the Andromeda at 99.9% the speed of light. I also have my laptop and I am picking up signals about the events that are occurring in both galaxies. I can understand that those events that are occurring now in the Milky Way are events that I will never learn about. Any signal emitted to me from the Milky Way travels at the speed of light or less and since I am traveling at 99.9% the speed of light that signal will never reach me just as a car one mile behind me going 30 miles will never reach me if I am also going 30 miles an hour. I do not understand however why time should stop with respect to those events that take place in the Andromeda Galaxy. I am traveling towards it and am capable of absorbing bosons coming from that region of space. So why should the time in the Andromeda Galaxy stop?
 
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  • #2
This is common nonsense in pop-sci. You cannot travel at the speed of light and there IS no frame of reference that is co-moving with light so saying that time stops is not meaningful. There is a FAQ entry about this on this forum but I can't seem to find it at the moment.

EDIT: here's one: https://www.physicsforums.com/threads/rest-frame-of-a-photon.511170/
 
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  • #3
gamow99 said:
I think my understanding of STR might be wrong. I was watching a documentary where they said that if you're traveling at the speed of light then time stops.
Didn't they also say that you couldn't actually travel at the speed of light for some reason like it would take an infinite amount of energy or some such thing? I'm wondering because next you say in your example that you aren't traveling at the speed of light but just 99.9% the speed of light.

gamow99 said:
Now let's say I'm traveling through intergalatic space from the Milky Way to the Andromeda at 99.9% the speed of light. I also have my laptop and I am picking up signals about the events that are occurring in both galaxies. I can understand that those events that are occurring now in the Milky Way are events that I will never learn about.
Why are you saying that? Aren't those signals actually some form of light signals, like radio signals? Wouldn't they travel at exactly the speed of light and eventually get to you since you are going slightly slower than the speed of light?

gamow99 said:
Any signal emitted to me from the Milky Way travels at the speed of light or less and since I am traveling at 99.9% the speed of light that signal will never reach me just as a car one mile behind me going 30 miles will never reach me if I am also going 30 miles an hour.
Those signals are traveling from the Milky Way at the speed of light, not less, so they will always be able to catch up to you. Your analogy with the cars should be that you are traveling at 29.9 mph and a car behind you going 30 mph will eventually reach you.

gamow99 said:
I do not understand however why time should stop with respect to those events that take place in the Andromeda Galaxy. I am traveling towards it and am capable of absorbing bosons coming from that region of space. So why should the time in the Andromeda Galaxy stop?
I think maybe you are thinking that it's your perception of events stopping that is the same as time stopping and if you were traveling at the same speed as the signals, then those coming from behind you would appear to stop while those coming from in front of you would appear to be going at very high speed. Is that right?

But since you cannot travel at the speed of light, you will see those events coming from behind you in slow motion and the ones coming from in front of you in high speed. Does that resolve your problem?
 
  • #4
ghwellsjr said:
But since you cannot travel at the speed of light, you will see those events coming from behind you in slow motion and the ones coming from in front of you in high speed. Does that resolve your problem?

That's what I needed to know. This clears up my confusion and this makes sense. Thank you for helping me out.
 
  • #5


Your understanding of special relativity is correct. According to the theory of special relativity, as an object approaches the speed of light, time slows down for that object relative to a stationary observer. This is known as time dilation.

In your example, as you travel at 99.9% of the speed of light, time would appear to be passing slower for you compared to someone who is stationary in the Milky Way galaxy. This means that events that are happening in the Milky Way would appear to be happening at a slower rate for you. However, this does not mean that time has stopped for you. It simply means that the rate at which time is passing for you is different from the rate at which time is passing for someone who is stationary.

Additionally, as you travel towards the Andromeda galaxy, time would also appear to be passing slower for you compared to an observer who is stationary in the Andromeda galaxy. This is because you are moving at a high speed relative to the Andromeda galaxy. This means that events in the Andromeda galaxy would appear to be happening at a slower rate for you. However, this does not mean that time has stopped in the Andromeda galaxy. Time is still passing, but at a different rate for you compared to someone who is stationary in the Andromeda galaxy.

It is important to note that time dilation is only observed by an observer who is moving at a high speed relative to another object. For you, time would appear to be passing normally, but for someone who is stationary in the Milky Way or Andromeda galaxy, time would appear to be passing slower for you.

In summary, while it is true that time slows down for an object as it approaches the speed of light, it does not stop. Time is a fundamental aspect of the universe and cannot be completely stopped. It can only appear to be passing at a slower rate for an object that is moving at a high speed relative to another object.
 

1. What is the theory behind time stopping at the speed of light?

The theory of relativity states that time and space are relative to the observer's frame of reference. As an object moves closer to the speed of light, time slows down for that object relative to a stationary observer. This is known as time dilation.

2. Does time actually stop at the speed of light?

No, time does not physically stop at the speed of light. However, it appears to stop for an object that is traveling at the speed of light relative to an observer. This is due to the time dilation effect mentioned in the theory of relativity.

3. How does time dilation affect a traveler at the speed of light?

For a traveler moving at the speed of light, time would pass normally for them. However, from the perspective of a stationary observer, time would appear to slow down for the traveler. This means that the traveler would experience less time passing than the observer, even though they are both moving at the same speed.

4. Can anything actually travel at the speed of light?

According to the theory of relativity, only massless particles, such as photons, can travel at the speed of light. However, it is currently impossible for any object with mass to reach the speed of light due to the immense amount of energy required.

5. How does time dilation affect the aging process for a traveler at the speed of light?

Because time appears to slow down for a traveler at the speed of light, they would age slower than a stationary observer. This means that a traveler could potentially experience a shorter amount of time passing while aging significantly less than someone who remained stationary. However, this effect would only be noticeable for extremely high speeds and would not be significant for everyday speeds.

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