Will humans ever be able to travel at the speed of light in space?

It was discovered some time ago that Proxima b would be the closest planet to which life is possible so far. This planet is 4.22 light years or 40 trillion kilometers away from us. With today’s technology, we would never get there in a lifetime. So I wondered if we would ever be able to make a spaceship that could travel at the speed of light. Then we would be there in a good 4.5 years, right? And can a human being able to travel at the speed of light?

Asker: Glen, age 35


No, traveling at the speed of light is impossible for a human being. There is nothing anthropocentric about that, the same goes for any being with a finite (different from zero) mass. When a mass is accelerated to the speed of light, an infinite amount of energy is needed, and it doesn’t exist. Only particles with a rest mass of zero, such as photons, can and must move at the speed of light. We’re not there. But accelerating us to any speed that is just short of the speed of light is possible. It also has to go gradually, which takes some time.

In principle, you can accelerate any mass to a speed close to the speed of light. Then you arrive a little later at Proxima b. How much later, depends on the energy you want to invest in it. And also what you want. Because going to Proxima b is one thing, staying there is another. Because if you want to stay there and watch, you have to use (and therefore have) the same amount of energy to slow down there again. Otherwise you just fly on, into the interstellar void.

In principle, it is possible to quickly send a small device to Proxima b, and have it send back to the next generation what it has seen there. It seems to me to be against Human Rights for many reasons to use human testing for that. Using other detection technology for this may become the subject of a social debate. And then the next generations will have to decide whether they think it’s worth taking it a step further.

Answered by

Prof. dr. Christopher Waelkens


Catholic University of Leuven
Old Market 13 3000 Leuven


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