So I'm reading a book called "The Elegant Universe" and here is a part of it
Imagine two countries that have been at war are sitting down to sign a treaty ending hostilities while traveling aboard a train that is moving at a constant velocity. The catch is that neither country's delegate wants to sign the treaty before the other delegate and thus, a simple system is devised to ensure that both delegates sign the peace treaty simultaneously. The solution involves setting a light bulb at the center of a table in such a way that the light bulb is exactly between the delegate from Forwardland (who is facing the direction the train is traveling) and the delegate from Backwardland (who has her back to the direction the train is traveling). When the light bulbs lights up, that is the signal for both delegates to sign the treaty.
This setup is agreeable to all parties on the train and to both security councils in the countries' respective capitals. Once the bulb lights up and the delegates have simultaneously signed the peace treaty, everyone on the train celebrates the cessation of hostilities, but they are perplexed to discover that fighting has broken out anew between the two countries. The reason given is that the delegate from Forwardland was tricked into signing the treaty before the delegate from Backwardland! How can this be? So, since the speed of light is constant how are the people on the train viewing it otherwise? How do they see light at the same time when really forward land was moving TOWARD the light and therefor saw it first. Why don't they see it like this? And how are the people off the train seeing it like it IS. (With forward land approaching the light and therefor seeing it like t is) and how does frame of reference affect this? Please don't use too many technical terms in an explanation