(February 19, 2017 at 11:33 pm)Alasdair Ham Wrote: I mean if we are defining 60 seconds as 60 seconds then... I mean.... any amount of time whatever that amount of time is is still that amount of time regardless of speedThat's true, to the person in the same reference frame as the 60 seconds, but not necessarily to someone outside that frame.
Let's say we run a little test. We get together with perfectly timed and synced watches. At exactly noon, 12:00:00, I will instantly accelerate to the speed of light. I'll watch my watch and as soon as it hits 12:01:00, 60 seconds, I decelerate back to "normal" speed. If we compare watches, you're saying you would expect both of them to read 12:01:00, is that correct? But they wouldn't. Your watch would read 12:10:00. As far as you're concerned, I've traveled for 10 minutes, but to me, I've only traveled for one minute.
Same principle goes for speed.
If I'm on a train going 50 mph and I throw a ball at 10 mph in the same direction the train is traveling, how fast is the ball going? First reaction might be, 60 mph. That's true, if you're on the ground watching the train go by. If you're on the train with me the ball is going 10 mph. If you're in a car going 60 mph in the same direction, the ball isn't moving. If you're in a car going 60 mph in the opposite direction the ball is going 120 mph. All of the answers can be correct at the exact same time.
So in the watch test, asking what the "real" amount of time that went by was, would be akin to asking which speed is the "real" speed of the ball.
