Speed of light, eh? Now we're getting into some Einstein type shit.
He noticed the same thing you did. Namely, light moves at the same relative speed as an observer on the train and an observer on the ground. It was kind of controversial at the time, since the only way that could be true is if time was relative.
Think of it this way - we express speed as an integer, but it's actually a fraction - speed is our way of measuring distance divided by time taken to traverse it. Normally and prior to Einstein it was assumed that the bottom number - the per hour, per second or per minute part - never changed. An hour was the same whether I was going 100 mph, 1000 mph or 1 000 000 mph. The hour was always the same; the only part that changed was how far I managed to get. That works for relatively small numbers of the sort we use in our day to day lives (often referred to as Newtonian physics, because they use Isaac Newton's less accurate but 'good enough' formulae), but when we get up closer to the speed of light, it starts to become less true. Finally, at the speed of light itself, the distance is the number that never changes; no matter where the person seeing it is or how fast they're going, the top number is always the same (299 792 458 m/s, or about a bit under 700 000 000 mph). That's tricky, since in order for the top number to stay the same and for the equation to still work, the bottom number has to change - so an hour is no longer an hour. Or rather it is, but my hour at 100 000 000 mph and yours at 1 mph aren't the same length of time.
This, again, leads to some funky stuff. For example, time passes faster at the top of a mountain than it does at the base, since the top of the mountain is moving faster due to the Earth's rotation. The difference is very small, but it's enough that a sufficiently accurate clock can measure it; this is one of the tests that was used to verify the theory, substituting a convenient water tower for a mountain since physicists aren't generally known for their mountaineering abilities.
Does that help you make sense of it?
EDIT -
Quote:
|
Originally Posted by Dilbert1234567
or if you throw it at the observer, you can hit him with it at 150 kph (ouch)
 |
This is true, sort of. In order for your throwing the ball at 30 km/h to give it a total velocity of 150 km/h, you'd have to throw it off the front in the same direction the train is going. In that case, for the ball to hit the observer at 150 km/h he'd have to be directly in front the train; I'd propose that if this is the case the ball is really the least of his problems.