So reading about how it's impossible to accelerate an object to the speed of light relative to another, I thought of this hypothetical situation:
What if you had this row of rocks, floating in space at the speed of 10m/s relative to another row of rocks (let's call the rocks going at 10 m/s row 2, and the ones floating at a relative speed of -10m/s row 1). In this situation, let's say these "rows" are infinite. Then you get another row of rocks and accelerate it to the speed of 10m/s relative to row 2 (row 3). Now row 3 should have a speed of 100 m/s relative to row 1, right? If you continue this, until you have a row going at the speed of 100 000 000m/s relative to row 1, and you get another row and get it to go at a speed of 10m/s relative to that, would it not be moving away from row 1 at a speed greater than the speed of light?. Because relative to row 2, it would just be going at 1/3 of the speed of light, and that should be possible.
Or what about this, you have this row going at a speed of 100 000 000m/s relative to row 1, and then you accelerate row 1 by 10m/s in the opposite direction. What would happen then? Because the speed at which they are moving away from the rock rows with the "in between speeds" is FACT. Isn't it?