More and more effort is required to move a smaller and smaller weight as it gets closer and closer to lightspeed. As speed approaches C, the amount of effort required to get to lightspeed approaches infinity. That's if my understanding of Einstein is correct.
The way I've heard it expressed by some folks and I wish I could give references here, but my memory is shoddy and I'm not any good at math there may be some sort of loophole involved. That is, one may not be able to get to lightspeed because of the difficulty on the approach. That doesn't necessarily mean that one can't go faster than lightspeed if one can find a way of getting there without passing C first.
That sounds a bit odd to me.
Of course that would depend on how much of the theory depends on something like linear acceleration, which is how I tend to think about speed, and how much may depend on geometry. I'm told that a lot of relativity has to do with geometry in some fashion, and that in the Einsteinian universe space is not to be considered a dimension involving only length, breadth and height but also time as a geometric consideration, and that mass distorts space in predictable ways.
I can imagine speed between two points, but when you toss in distortions of mass and time, my brain simply goes on strike.
It would be nice, however, if we were able to access speeds greater than light and survive the process. It would make star travel at least a possibility, and that would be something marvelous indeed.