[drme19811]

Consider a train , its proper length = 375000 km , traveling at a speed of 180000 km/sec (0.6 of speed of light) relative to person (name him B)

Consider a beam of light that travels in the same direction of the train

The train traveler (name him A) will measure the train length = 375000 km , & will measure time required for light beam to travel from the back of the train to the front of the train = 1.25 second (as light travels in a speed of 300000 km/second)

B will measure the length of the train = 300000 km (as length contraction occurs) , & will measure time required for light beam to travel from the back of the train to the front of the train = 1.5625 second (as time dilation occurs for time of A)

B will measure the distance that light beam traveled = 180000 * 1.5625 (the distance that train traveled) + 300000 (the length of train as B measured it) = 281250 + 300000 = 581250 km (B will measure that light travels this distance at 1.5625 second) i.e. B will measure the speed of light = 372000 km/second

Does this prove that light speed is not constant for all observers?

May be I’m intelligent, may be I’m a fool
But I must try , to know what ma I
Even if I’m a fool
I hope you will reply

Thanks

[tucsonmac]

The problem as I see it is that the light is outside of the train, therefore there is no time dilation. The time for the light to reach the front of the train is 2.5 seconds. During this time the train travels 450,000 km. Add to this length to the contracted length of the train, and divide by 2.5 and you get 300,000 km/sec. The postulate is upheld.