Einstein's Train: Light Travel Time Explained

In summary, Einstein's Train thought experiment shows that an observer, M', will see lightning strikes A and B as simultaneous whether they are actually simultaneous in the Train frame or not. This is based on considering the travel time of light between the strikes and the observer's eyes. However, if the flashes are actually simultaneous in the Train frame, M' will see B before A because he will be closer to B when the light reaches him.
  • #1
David Lewis
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TL;DR Summary
Einstein's Train -- M' will see B before A whether the events are simultaneous in Train frame or Embankment frame.
https://www.physicsforums.com/attachments/269029
Lightning strikes A and B simultaneously in the Embankment frame.
M' sees the flash at B before the one at A.
But if the flashes are simultaneous in the Train frame, does M' still see B before A?
 

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  • #2
If the events are simultaneous in the train frame, then M' sees the events simultaneously(the light from the events reach him at the same time) and M doesn't.
 
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  • #3
David Lewis said:
Summary:: Einstein's Train -- M' will see B before A whether the events are simultaneous in Train frame or Embankment frame.

But if the flashes are simultaneous in the Train frame, does M' still see B before A?
No. Why would they?
 
  • #4
To answer the question in the title ("Does Einstein's train account for light travel time?"):
Yes. The entire argument is based on considering the consequences of light travel time between the strikes and the observers' eyes.
 
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  • #5
If the flashes are simultaneous in the Train frame, does M' see B before A?
Dale said:
No. Why would they?
Because when the light reaches M', he will be closer to B than to A.
I forgot, however, that when an observer sees two equidistant events happen at the same time then they are simultaneous in his frame.
 
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1. What is Einstein's Train thought experiment?

Einstein's Train is a thought experiment used to explain the concept of time dilation in special relativity. It involves a train moving at a constant speed and a person standing on a platform observing the train.

2. How does the thought experiment explain light travel time?

In the thought experiment, the person on the platform sees both the front and back of the train at the same time due to the speed of light being constant. However, the person on the train would see the back of the train first and then the front, leading to a difference in perception of time and distance.

3. Why is this thought experiment important in understanding special relativity?

Einstein's Train thought experiment helps to illustrate the concept of time dilation and how it is affected by the speed of an object. It also highlights the idea that time and space are relative, and depend on the observer's frame of reference.

4. What are the implications of this thought experiment in real-life scenarios?

The thought experiment has real-life implications in fields such as space travel and GPS technology. It helps to explain the effects of time dilation on astronauts traveling at high speeds and the need for precise calculations in GPS systems due to the difference in time between satellites and receivers on Earth.

5. Are there any limitations to this thought experiment?

While Einstein's Train is a useful tool in understanding special relativity, it is a simplified thought experiment and does not account for all the complexities of the theory. It also does not consider the effects of gravity on time dilation, which is a crucial aspect of general relativity.

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