Can a photon arrive before an observer traveling at the same speed?

In summary, if two observers were travelling at the same speed, the observed photon would not be able to arrive at its destination before the observer.
  • #1
_PJ_
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15
I am curious as to how a photon traveling at 'c' is described by an observer also traveling at 'c'.

Elementary education tells us that photons, always travel at the same average speed in the same medium, regardless of the motion of the observer.
However, if both were traveling at 'c', from point A to B, could the observed photon cannot arrive at B before the observer? I don't think it should, because then it would indicate that information could be transmitted to B faster than light.

My only 'solution' to this comes from the lorenz contractions of time seem to suggest that in a photon's lifetime, from its own 'experience' the entire distance traveled on its journey (including A and B) are contracted as though it travels no distance at all. The observer in the example above, would also be subect to these contractions. Therefore traveling 0 distance at ANY speed would always take the same time (also 0 )

How accurate is this hypothesis? Am I missing something or confused somewhere?
 
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  • #2
An observer cannot travel at c. More specifically, we cannot define an inertial frame traveling at c relative to another inertia frame. Therefore, your question is moot.
 
  • #3
Thanks for the response. The impracticalities of massive ojects moving at 'c' aside, I was merely curious as to the 'what if' scenario.
Your statement regarding inertial frames, though, I think is more crucial and certainly would nullify the possibility of being able to provide a real answer. This helps a lot, because it ironically does answer te problem by highlighting its impossibility!
 
  • #4
Hootenanny said:
An observer cannot travel at c. More specifically, we cannot define an inertial frame traveling at c relative to another inertia frame. Therefore, your question is moot.

Yes, it can travel at c or faster if c means the light velocity v in a transparent medium. In a transparent medium the light velocity v is smaller than c but particle velocity V can be equal or exceed v. In the latter case the particle arrives earlier than the light. Remember the Cherenkov's effect for charged particles.
 
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  • #5
Bob_for_short said:
Yes, it can travel at c or faster of c means the light velocity v in a transparent medium. In a transparent medium the light velocity v is smaller than c but particle velocity can be equal or exceed v. In the latter case the particle arrives earlier than the light. Remember the Cherenkov's effect for charged particles.

What do you mean when you say "it"? Are you saying that you can define an inertial reference frame with a velocity v > c as measured from the lab frame?

You should note that the OP specifically mentions observers traveling at c, rather than observers traveling faster than light. If the OP would have stated the latter, then of course it would be appropriate to discuss Chenkerov radiation. However, since the question was related to the former, Chenkerov is irrelevant here.
 
  • #6
_PJ_ said:
Thanks for the response. The impracticalities of massive ojects moving at 'c' aside, I was merely curious as to the 'what if' scenario.
Basically, you are saying "If relativity were NOT true, what would it say about this situation"! And the answer, of course, it that if it were NOT true, it would NOT say anything meaningful.

Your statement regarding inertial frames, though, I think is more crucial and certainly would nullify the possibility of being able to provide a real answer. This helps a lot, because it ironically does answer te problem by highlighting its impossibility!
 

1. What happens to an observer when they reach the speed of light?

According to the theory of relativity, an observer cannot reach the speed of light. As an observer approaches the speed of light, their mass would increase infinitely and it would require an infinite amount of energy to accelerate them further. This is why it is impossible for an observer to reach the speed of light.

2. How does time dilation affect an observer traveling at the speed of light?

Time dilation is a phenomenon that occurs when an observer is moving at speeds close to the speed of light. As an observer's speed approaches the speed of light, time appears to slow down for them relative to an observer who is stationary. This means that time would appear to pass slower for an observer traveling at the speed of light compared to an observer on Earth.

3. Can light speed be exceeded by an observer?

According to Einstein's theory of relativity, the speed of light is the maximum speed at which anything in the universe can travel. This means that no observer or object can exceed the speed of light. However, there are some theories that suggest the existence of particles called tachyons that can travel faster than light, but they have not been proven.

4. How does the concept of mass-energy equivalence apply to observers at light speed?

The concept of mass-energy equivalence, famously expressed as E=mc², states that mass and energy are interchangeable and can be converted into one another. As an observer approaches the speed of light, their mass would increase infinitely and it would require an infinite amount of energy to accelerate them further. This shows that the energy required to reach the speed of light is equivalent to the infinite amount of mass that the observer would have at that speed.

5. How does the speed of light affect the concept of simultaneity for observers?

In classical physics, simultaneity is the concept that events happening at different locations can occur at the same time. However, according to the theory of relativity, an observer's perception of simultaneity is relative to their frame of reference. This means that an event that appears simultaneous to an observer at rest may not appear simultaneous to an observer traveling at the speed of light. In fact, an observer traveling at the speed of light would experience all events in the universe happening at the same time.

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