I'm trying to understand a few things about the speed of light.
From what I've read, nothing can travel faster than the speed of light.
If anyone takes a spaceship and accellerates it to the speed of light © (which I've read is not possible with anything that has a mass, but let's just pretend it is possible), the time outside slows down (from the persons inside the spaceship's point of view) and would reach its destination immediately, but for an observer outside the ship would still travel at 300000km/s.
Ok, I think I got this.
But now for the questions:
1. First of all, how did we figure out the speed of light in the first place? Did we measure its velocity in some way or...? If we did not measure it, how do we know the light actually travels at 300000km/s, and that this number is just a constant we use that has nothing to do with the actual speed of light?
2. From what I've read, when matter accellerates towards the speed of light, more and more energy are required to push it just a little faster because the mass of the traveling object is getting higher and higher until it reaches infinity at the speed of light. Ok, this is WHAT that is happening, but why is it so? How can an object gain mass "just by" accellerating towards the speed of light? Isn't the mass of an object constant (assuming there's no outside interference)?
3. I've also read that first when matter reaches approximately 1/3 of light speed, it starts to gain mass and needs more and more energy to accellerate it any more (like I mentioned above). Why this particular speed? Are the "time dilation" that comes with objects moving at near the speed of light present also at lower velocities, but the effects are so small that they are just insignificant before 1/3 of light speed?
4. Everything is moving at a speed relative to an other object, right? But what about the speed of light: Let's say we got TWO space ships that are capable of travelling at the speed of light. We place them at the opposite end of our solar system, and they accellerate to the speed of light towards eachother. When they meet, both ships are travelling at 300000km/s. But then, if you take one of the pilot's point of view, you are moving towards the other ship at 600000km/s, because that ship also travels at 300000km/s towards you. But what then happens to the "nothing-can-travel-faster-than-C"-rule?
I hope someone can enlighten me a little on these questions, as I really do wonder.. I've read a little about this subject, but the more I understand of it, the more questions seems to pop up :P
Well, thanks in advance for any answers.