Hi everyone, Today a strange thought came into my mind. We know that the mass of an object increases as it gets closer to the speed of light so it is often stated we would require more and more fuel to accelrate it further. However the mass of the fuel would also increase. What could be done now is you say build a nanospaceship filled with fuel, accelerate it so close to the speed of light so that it it's mass would be say ten times the original mass, with repect to the external environemnt, and so would be the fuel now. So now the remaining fuel is providing TEN times as much as kinetic energy to the nanoship AGAIN with repect to the external environemnt. By us whor out of the spaceship letting it get bombarded now we could derive appx ten times the energy which we originally provided by the fuel. by reconverting that energy into another fuel and repeating this process over and over one could then require infinite energy. But doesnt this violate the law of conservation of energy. Can somebody explain this?