Transcript: Visionaries have imagined leapfrogging over current or even planned technologies to the forms of rocket propulsion that can reach relativistic speeds, rocket speeds close to that of light. One form of energy release is matter-antimatter annihilation. Antimatter is rare on Earth. It naturally doesn't occur, but it can be created in the lab and potentially in a rocket engine. Matter-antimatter annihilation liberates the entire mc2 of trapped energy in matter with an efficiency that’s more than a hundred times that of nuclear fusion within the Sun. A second technology is a ramjet which would gather diffuse hydrogen from the interstellar medium itself as the rocket traveled. Imagine a huge scoop many kilometers across gathering the diffuse hydrogen. The hydrogen would then be fused to helium within the rocket to create the energy source. Using either of these technologies, neither of which have ever been prototyped, it would be possible to travel to the stars in times much less than a human lifetime.