A very interesting topic, and one of my long time favorites. I think in this century perhaps we will see that Einstein filled in part of the puzzle, but there are gaps. Einstein himself admitted that he was troubled by missing pieces in his overall concept - something that people are working on now called the unified theory, or grand unified theory. All together it involves matter, anitmatter, and if I remember correctly such things as gravity and anti-gravity, as well as opposing forces of magnetism - it has also been called a unified field theory.
With respect to travel at the speed of light, there are ways to bend the rules to some degree. Warp travel (long the hip buzz word from star trek) is actually based on real concepts. Rather than moving at or faster than the speed of light, you warp the space/time fabric around you as you move - in effect changing the distance you travel as you move. It's easier to grasp if you picture a bubble around a craft. The space/time fabric is distorted - perhaps via a strong gravity or magnetic field. Essentially you compress the distance ahead in your favor, while stretching the distance behind, and thus cross a given distance as though it was unchanged but you were moving much faster. Worm holes on the other hand are best thought of as short-cuts between folds of space/time fabric. Think of ocean waves and then picture yourself riding a boat over the waves. If you entered a worm hole it would be like cutting through the wave crest under water to reach the other side, instead of having to travel the entire distance on top of the water - over the wave top and down the side. Very interesting stuff.
