I know light behaves oddly compared to normal matter, I haven't really delved into the math of GR, and that's why I'm here to ask these questions. 1) If all of our observations of the universe are based on light, what determines that the speed of light is the maximum velocity? I'm sure its somewhere in the math I haven't been taught/tried yet. 2) (> i've heard in a another thread that light will just redshift if this happens I think so this is probably wrong) If something is traveling one way at 1000 m/s and from that something is launched in the opposite direction at 400 m/s the net velocity of the launched object is in the direction of what it was launched from if dark matter is traveling FTL away from us and behaves similarly then the light would never reach us hence why we cant see it? (but the speed of light is constant, and light behaves weirdly and whatnot so :/ ) sort of unrelated question: since a black hole has mass and we can't see them are they considered dark matter? i'm prepared for the million reasons why i'm wrong to be yelled at me xD.