1. According to Relativity theory, NOTHING with mass can go faster than the speed of light----"c"----because to do so would require an infinite amount of energy. So it is an effective, universal speed limit. 2. Now, there IS a possibility that one can find a "loophole" in this, by the fact that SPACE itself is believed to be able to expand/contract at speeds that are faster than light. (See "Inflation theory"). So one could---theoretically---achieve supra-luminal spaceflight if one could find a means by which to warp/fold/bend space itself. This shortening the "distance" an object would need to travel. Sort of like Star Trek's "warp drive". 3. Compared to the level of technological advancement that would be required to support a civilization that is capable of of long range intersellar flight.....think Star Trek at a minimum, more like Star Wars and its galactic civilization more likely.....our technology and civilization are both very primitive. So a very good reason why we aren't seeing any space travelling aliens, is that we have NOTHING they would be interested in...and don't have the technology to listen in on their communications....or even understand it if we stumbled accross it. Besides, NONE of the communication signals our civilization has put out has gone farther than about 75 light-years. The Milkway Galaxy...our home....is one hundred THOUSAND light-years across. IOW. Think small inkspot on a piece of paper. Anyone listening to radio waves would have little chance of noticing us...and any civilzation capable of coming here has probably LONG since progressed past using radio (and TV) for communication.