I recently watched a documentary on Albert Einstein that said the inspiration (or epiphany I guess) for the slowing of time as speed increases occured to him while he was on a bus. It said that one of Einstein's day dreams, was that he would imagine himself riding on a beam of light. Well, while he was on the bus, he was having this day dream, and he was watching a clock tower out the back window, leading him to theorize that because he was going the spped of light, the light from the clock tower wouldn't be able to reach him, so the image of the clock would remain the same as when he started going light speed, thus stopping time. I was confused by this. Yes, the image of the clock would remain the same, so if you were to read it, it would never change. My question is, how is that actual time dilation and not just the image staying stationary (like taking batteries out of a clock- time would still pass, the clock just wouldn't show it)? Sorry this may sound stupid, because I don't know much about the subject- I'm still in high school; but I just don't understand how time is linked to light. Does this have something to do with the increase in mass that occurs at that speed, therefore causing a greater impact in the fabric of spacetime with greater gravitational forces etc.? I know that supermassive objects like blackholes create that event horizon that bends space and time but I have no idea if that's in any way relevent haha. Again, sorry if this all sounds like nonsense- because maybe it is- but I don't understand this concept very well.