Imagine the following scenario. There is a long train moving at very fast speeds (approaching light speeds), one man stands at the back of the train with a watch and another at the front. A third man stands exactly halfway between them with some gunpowder and a match. The men at the back agree to set their watches to 1 o clock when the light from the gunpowder reaches them (I said fast and long train so that it will actually take a reasonable time to reach them). A forth man watches from outside the ground. The gunpowder goes off, and both men set their watches. The third man views this and says it was a fair timing and both had set their watches to the same time. However the man from the ground sees the light reach the man at the back of the train 2 seconds earlier (since relative to him the man at the back is moving towards the light and man at the front away). So he thinks the clocks are set to 1:00 and 1:02. The train slows down and the man from the ground goes and sees the watches. What will they say? I'm having a bit of trouble coming up with an answer for this because I know both views are both equally valid views, but the clocks can only say one thing when they all look at it togeather.