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Can the human body withstand travelling at the speed of light?




Image: Boris Štromar, CC BY 3.0

The problem here is that travelling at light speed happens in a totally different physical world to the one we are used to.
When we travel by car, bus or aeroplane, we’re in Newton’s world. This means that, providing the acceleration is not too great, we humans can survive fast car journeys, fast aeroplane journeys and even rocket launches unscathed. It all depends on the magnitude and speed of the acceleration. In a car, that would be how much you put the “pedal to the metal”. If you had a car that could keep getting faster, you could theoretically reach speeds of up to tens of thousands of kilometres per hour (the International Space Station travels at 28,000 km/h). But even at just several times the speed of sound, i.e. several thousand km/h, the forces acting on your body would be enormous.
As we get close to the speed of light, however, we find ourselves in an entirely different physical world – that of Einstein’s theory of relativity. If an object were to travel as fast as light, it would become infinitely heavy and it would take an infinite amount of energy to move it. Given our everyday experiences of how acceleration and gravity work, it is almost impossible for us to imagine that. Then of course, there is the fact that travelling at the speed of light would completely alter the way time passes for us (this phenomenon is described in the twin paradox).
From a physiological perspective, therefore, travelling at the speed of light is still just a dream.

This question was answered by Jens Hauslage of the Institute of Aerospace Medicine at the German Aerospace Center (DLR).