I have a few queries regarding achieving/overcoming the speed of limit: 1. There are three spaceships X, Y and Z. X moves away from Y at 0.9c and Z moves away from Y at 0.9c in the OPPOSITE direction. Relative to X, wouldn't the speed of Z be 1.8c? 2. Has the limit "c" been physically observed or is it only theoretical? That is, have we actually tried accelerating particles and noticed that their speed always stays below c? 3. Recently, during an experiment at CERN, some scientists claimed that a certain particle was accelerated to such an extent that it moved faster than c. However, later there appeared to be some discrepancies in the data. I wasn't able to gather what was the final verdict..was the scientists' claim correct or not?