Hello. I have been studying a lot of physics on my own through the internet (I am 16 years old, I intend to keep studying physics when I get older), and I get the most of Einstein's theories and quite a lot of the quantum mechanics, but there is something I don't understand about special relativity; According to special relativity, a particle with mass can't reach the speed of light, c, because its mass would just keep increasing. Fine with me. BUT, the theory also states that speed is just something relative, and is different according to what you compare it to. But my question is then, if a particle is approaching c, let's say 99% of it, what is it traveling relative to? Space itself? Is there a theoretical "map" of space wich objects can travel across, or is speed only relative? Another example: How can a particle with mass be at rest, since everything in the universe is moving? Let's say we take a stone. We put the stone on a table, and let it lie there on the table. The particles would then be at rest, but not according to an observer standing outside of our solar system, or outside our galaxy. To that observer, the stone would be traveling really fast, and therefore not have a rest mass. Please help me out on this, I really don't get it.