(01-25-2011, 09:27 PM)James02 Wrote: Point being, make the observation first, then draw your conclusion. With your observation, I conclude light is acting just like a sound wave.

No, waves are acting like waves, but the comparison breaks down there. These are not the same types of waves. Sound waves are mechanical waves, and only the energy is propagating. No matter is being moved anywhere, except being displaced in a direction perpendicular to the direction of wave propagation. It's like a wave in a pond when you drop a rock in. The wave spreads out, but none of the substance of the water is actually moving in the direction of the wave. It's just going up and down as the wave goes through it. Light, on the other hand, is an electromagnetic wave. It's not propagating though a medium and displacing matter as it goes. Rather, it IS matter that is itself moving, but also contains wave-like properties. And that's what we're talking about - matter moving. If you throw a baseball 50 miles an hour, and I'm watching you from the side, it looks to me like it's moving at 50 miles an hour. If you then do it again when standing on a truck that is moving past me at 60 miles per hour, you will still see the ball as moving at 50 miles per hour, but I will see it as moving at 110 miles per hour. So the velocity measured is relative to the observer. That's basic observation.

Except it turns out that that doesn't hold up at high speeds. The faster something is moving, the LESS relative that measurement is. So if instead of throwing a baseball, you turn on a flashlight, it's not relative at all. You measure the light as moving at 186000 miles per second on the truck, and so do I, standing on the side. I do NOT measure it at that plus an additional 60 miles per hour. But it doesn't even have to be light or anything with obvious wave properties. If you had a heck of an arm and threw that baseball at 99.99% the of speed light, you would measure it at 99.99% the speed of light, but I still would not measure it at 99.99% plus 60 miles an hour. I would measure it as moving faster than you would, but not by 60 miles an hour - somewhat less than that. In fact, if we measure things with extreme precision, we would find that even in the original example of throwing the baseball at 50 miles an hour, I do not measure it as moving 110 miles per hour - it is very slightly less than that, but so slightly it is never noticeable.

So if we are measuring things at different speeds, that can mean only one thing - either we are measuring time or distance differently. In fact it is both - the difference in the time measurements is not quite enough to account for the difference in speed measurements - the distance is also being measured differently. So for objects moving relative to one another, each sees time moving slower for the other AND each sees length contracted for the other. This is Special Relativity, and the math for this is relatively simple.

The math for General Relativity, on the other hand, is not so simple. General Relativity solves the same problem for non-inertial frames. In other words, when objects are not moving at a constant velocity, but accelerating. Which it turns out applies to objects being affected by gravity. Being closer to or further from a heavy object exerting a gravitational influence also affects the measurement of time and distance.