>If we can't travel faster than the speed of light

using existing understanding of Nature - we can. At least the Universe provides the example of galaxies traveling with faster than the speed of light relative to each other. The same machinery is suggested in the

http://en.wikipedia.org/wiki/Alcubierre_drive

The opponents state that the energy requirement of the drive is higher than the whole Universe's energy. Obviously it is wrong statement as we already have whole galaxies mentioned above and whose faster than light speed obviously takes less than the whole Universe's energy.