- #1
JustinTime
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I have a question about a thought experiment I read about. I think the question or a similar was asked, and I'm sure others have asked this question, but I'm asking it in this way so it can be answered through the framework of my question. The framework of how I'm understanding it, and so that if there is a flaw, I can be shown what that is. I don't have a math or physics background, but have found what I've read about relativity fascinating. I got a book called Einstein's Relativity by Max Born and a lot of it is over my head but I understand bits. The thought experiment I'm listing wasn't in this book.
The thought experiment is a train is moving forward and on the top and bottom are mirrors which reflect a light up and down. It is said that for the person on the train, they will see the light go straight up. But an an observer positioned outside of the train will see it traverse diagonally. What I don't understand is this: If the speed of light is constant, it moves independent of the train. So when the light is first reflected to the opposite mirror, why wouldn't both observers see the light bounce and hit the other mirror slightly *behind* where it hit the other? I understand that if a person in a train throws up a ball, to him it appears to go straight up but to the person outside it is seen as an arc. But with light, it travels independent of the speed of the train. In order for the person in the train to see the light travel a straight path, wouldn't the beam of light have to shift or travel additionally in the direction he's going?
Thank you in advance to anyone who takes the time to answer.
Justin
The thought experiment is a train is moving forward and on the top and bottom are mirrors which reflect a light up and down. It is said that for the person on the train, they will see the light go straight up. But an an observer positioned outside of the train will see it traverse diagonally. What I don't understand is this: If the speed of light is constant, it moves independent of the train. So when the light is first reflected to the opposite mirror, why wouldn't both observers see the light bounce and hit the other mirror slightly *behind* where it hit the other? I understand that if a person in a train throws up a ball, to him it appears to go straight up but to the person outside it is seen as an arc. But with light, it travels independent of the speed of the train. In order for the person in the train to see the light travel a straight path, wouldn't the beam of light have to shift or travel additionally in the direction he's going?
Thank you in advance to anyone who takes the time to answer.
Justin