I am reading a book called Simply Einstein...it wonderfully helps a novice understand Einstien's theory or relativity. But I am stuck and need some help here! He gives an example in which you have a spaceship uniformly moving at 0.8c and as soon as it passes the earth a clock on the ship reads 0 as does a clock on the earth and a star 20 light years away (to which the ship is travelling.) Now, in a discussion about simultaneous time...he says to a person on earth and the star, time will read 0 but from the space ship...the supposedly synchronized time on earth-star time will be different! Quoting a part of the book the author says: Ship is at rest in its respective frame and objects of interest (earth and star)are moving towards it from the right. Events that are simultaneous in one reference frame (like the Earth-star frame) are not simultaneous in another frame (such as on the ship) and, furthermore, the event that is on the right occurs first. That means the event of the star clock reading 0 occurs BEFORE the Earth clock reads 0 as observed from the ships frame of reference. In other words, the star clock reads a later time. Here, as oberved in the ship frame, Earth (heading to the left) passes the ship at the instant the ship and Earth clocks both read 0. But the star clock is ahead, so it reads a later time. I won't go through the math, but the later time is, in fact, 16 years! Somebody please explain!!!