IMPLAUSIBLY high energy demands and insurmountable engineering difficulties haven’t stopped people fantasising about “warp drives” that could propel spaceships across the Universe faster than the speed of light. But now a Portuguese mathematician says he has proved that the idea is impossible.

Although Albert Einstein’s special theory of relativity says nothing can travel faster than light, Mexican mathematician Miguel Alcubierre found a way round the problem in 1994. He showed that a bubble with walls made of negative energy would distort the space around it. In theory, if the bubble contracted the space immediately in front of it and expanded the space behind, it could travel …