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Constant Velocity Motion In Train Car

  1. Oct 5, 2009 #1
    One of the scenarios that I've come across while reading about special relativity is the scenario of a person riding on a train undergoing constant velocity motion, such that the person in a train car with all windows drawn is unaware that their train car is moving at all. The car is not accelerating, there are no bumps in the road. The suggestion is that the person in the car cannot perform any experiment that allows them to determine whether they are undergoing motion or not.

    My question is whether this is a thought experiment, or whether it holds true in reality? If a person could measure sub-atomic particles like neutrinos, wouldn't they be able to conduct an experiment that determines their motion? Some particles travel through the train compartment's walls. So we should be able to determine motion relative to those, right?

  2. jcsd
  3. Oct 5, 2009 #2


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    When the experiment says "windows drawn" it really means that the train is isolated from all outside stimulus.
  4. Oct 5, 2009 #3
    How do you tell if it's the particle moving or the train moving? Assuming you are just sitting their with with no other reference point how can you know?

    How could you conduct an experiment to deduct that? I also think that example wasn't meant to be seen so rigorously. Yeah you could use a particle to say that either or condition is true, knowing that trains travel a specific speed relative to the earth or the ground, you can deduct that way, but if there is no other reference, you will always get stuck at having to refer to another point to compare. Imagine a single object in empty space moving at constant velocity, Is it moving or stationary?

    At least that what I got from my readings....I could be totally wrong and make a fool out of myself.
  5. Oct 5, 2009 #4
    There is no easy way to do anything that is difficult. Someone can not teach a fast way around, putting in the time
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