View Full Version : Episode 9: Einsteinís Theory of Special Relativity

2007-Mar-02, 05:37 PM
In this episode where they are talking about light bouncing between two mirrors while on a train, what would keep the light in tune with the mirrors. What I mean is, lets say the train was going at extremely high speeds like >50% of the speed of light, why would the light even travel back to the first mirror instead of just hitting the ceiling somewhere else further back. I suppose you might just have to have long enough mirrors to reflect the light back to its source . . . I guess the analogy was just not feasable to me.

2007-Mar-02, 09:29 PM
Why wouldn't the light hit the mirror? If it hits in one frame, it needs to hit in all inertial frames.

Someone on a train tosses a ball straight up, and they see it drop straight down. Someone on the ground sees the ball travel in a parabola; it has a transverse velocity component along with the vertical one. Same basic concept, except the speed of the ball isn't constrained to be the same in all frames.

2007-Apr-12, 11:21 AM
It wasn't mentioned in the show but as the speed of Gravity is the same as for Light, it's [gravity] information also appears to slow down in an inertial system [train] when viewed from the field.

I was thinking about a sort of clock like the one used in the show except imagining a wave-front of Gravity instead of Light, though the gravity couldn't bounce back off the second mirror of course. If a mass is at mirror #1 it would be constantly propagating Gravity towards mirror #2 (and in every other direction as well). This force (and the information) would also appear to slow down just like the Light beams when viewed from the field.

2007-May-20, 09:44 PM
well,concerning the momentum part of the podcast, i couldn't understand it, so i'd like anyone to help me witrh it.