Einstein's Train: Does Speed Exceed c?

In summary, the conversation discusses the concept of relative speeds and the limitations of measuring speeds greater than the speed of light. It explains how time dilation, length contraction, and the relativity of simultaneity play a role in the perceived speeds of objects. The conversation concludes that no rules are broken and nothing can move faster than the speed of light relative to an observer.
  • #1
Chris Frisella
76
6
Youtube vid of an Einstein's Train example:

From the perspective of the man on platform, the rear of the train seems to be approaching the front lightning's light at greater than c (train's speed + c). Is this correct? I thought there was a rule against that...
 
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  • #2
That's fine. What is forbidden is that you ever measure speeds greater than c relative to you.

Time dilation, length contraction, and the relativity of simultaneity conspire so that the guy at the back of the train measures the light coming towards him at c (you might want to Google for the relativistic velocity addition formula).

Nothing is moving faster than c relative to you. Nothing is moving faster than c relative to the guy on the train. No rules broken.
 
  • #3
Chris Frisella said:
From the perspective of the man on platform, the rear of the train seems to be approaching the front lightning's light at greater than c (train's speed + c). Is this correct?
Yes, perfectly correct. The "closing speed" of the light and the rear of the train is greater that c.

Chris Frisella said:
I thought there was a rule against that...
No. Note that no one measures anything to be moving faster than light with respect to themselves.
 
  • #4
Well, alright then. Thank you both
 
  • #5
Chris Frisella said:
Well, alright then. Thank you both
I think not the rear of the train but front of the train approaches faster to the front strike and rear of the train "escapes" from the rear strike.
 

FAQ: Einstein's Train: Does Speed Exceed c?

What is Einstein's train thought experiment?

Einstein's train thought experiment is a hypothetical scenario created by Albert Einstein to illustrate his theory of relativity. In this scenario, a train is moving at a constant speed and a person inside the train is conducting experiments to measure the speed of light.

Does the train's speed exceed the speed of light?

No, according to Einstein's theory of relativity, the speed of light is the maximum speed that any object can travel in the universe. Therefore, the train's speed cannot exceed the speed of light.

What is the significance of this thought experiment?

The significance of this thought experiment is that it helps to explain the concept of the speed of light being a constant in all frames of reference, regardless of the observer's motion. It also demonstrates the principles of time dilation and length contraction.

How does this thought experiment relate to Einstein's theory of relativity?

Einstein's train thought experiment is used to illustrate the concepts of special relativity, which states that the laws of physics are the same for all observers in uniform motion and the speed of light is constant in all frames of reference.

Can this thought experiment be applied to real-life situations?

Yes, the principles demonstrated in this thought experiment have been confirmed through various experiments and are used in modern technologies such as GPS. The principles of special relativity have also been applied in fields such as astrophysics and particle physics.

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