The problem with interstellar space travel is the vast amount of distance between stars. The speed of light is approximately 186,000 miles per second. The closet star in our galaxy is approximately 4.5 light years away. That means traveling 186,000 miles per second continuously for 4.5 years. There are at least two challenges I have read about traveling at or near the speed of light. The first challenge is the enormous amount of energy required to get to and maintain the speed of light. The second problem (of many problems I presume) is the closer you get to the speed of light, the more the mass of the object comes into play. It would be impossible (using modern physics) to travel at the speed of light because you would be crushed from the weight (mass). Therefore, if you can reduce the mass of an object, the closer you can get to the speed of light. If you can lower the mass enough, theoretically you could go faster than the speed of light. This is why we have observed UFO's and USO's moving so quickly above and below water...somehow the extraterrestrials have figured out how to change the mass of their vehicles. It also explains why they can change direction without being affected by gravity or requiring wings for lift. They have perfected the anti-gravitational propulsion system. The Truth is out there.