Asked by M Johnson
First of all it is worth noting that, as far as we understand, only light can travel at the speed of light. For a spacecraft to do it, under our current knowledge of how physics works, an infinite amount of energy would be required. While this remains a physical impossibility it certainly doesn’t stop us thinking about the implications of light-speed travel.
As Albert Einstein’s theory of general relativity shows, as an object approaches the speed of light its mass also increases. An object’s mass determines its gravitational influence. In fact all things have a gravitational field, it is just that gravity is so weak we only feel it from very massive objects, like planets.
As we increase our spacecraft’s speed and therefore its mass, its gravitational effects would also increase. In general relativity mass and energy are equivalent and so as we approach an infinite amount of energy and equivalent mass, the spaceship’s gravitational influence would also increase to be higher than its usual field.
Faster than light travel has been something that has attracted a great deal of interest from both the science fact and science fiction communities. If we could find a way to travel faster than the speed of light, wide spread exploration of our galaxy may be possible. With current technology any attempt to explore outside of our Solar System would take a phenomenal amount of time, the next nearest star taking around 80,000 years to reach in our most modern rockets.
Answered by Josh Barker from the National Space Centre