In regards to the "speed" in which an object travels through space. On earth we determine speed by how fast an object is moving in relation to the ground. The speed of the earth is determined by it's relation to the sun. The speed of the sun is determined by it's relation to the center of the galaxy. etc. etc. How is the speed of an object determined in the vacuum of outerspace? Light obviously travels at a constant speed in relation to it's source, but all light sources in the universe are themselves "moving". How do we know what "stationary" is in outerspace to identify the true "speed" of an object? And how does this factor into setting limitations on how 'fast' matter can "travel'. I guess what I'm trying to figure out is whether or not "the speed of light" is actually a barrier when it comes to how "fast" matter can travel. Any thoughts?