On: Ways to travel at nearly the speed of light

[p-schultz]

There is no difference between you moving with velocity X and the other party moving with velocity -X; or you moving with velocity 2X and the other party being stationary; or you being stationary and the other party moving with velocity -2X. There is no experiment you can perform that will tell the difference.

[ars → p-schultz]

You missed the point that both parties accelerate, we are not talking about constant velocity here.