I have read, that as a rocket approaches light speed, objects in front of it become blue shifted and also intensity of light increases. Does this mean that at some point any rocket will be destroyed, just because the blue-shift will cause impacting photons to become gamma rays of arbitrary high energy - so high in fact that no material could withstand it?

  • $\begingroup$ When I first read the title to this question, I thought it was about the unruh effect, which is something else to consider. It says that if you are accelerating, you will see blackbody radiation, even in empty space. You would have to have a very large acceleration for this effect to be noticeable though. $\endgroup$ Nov 19, 2013 at 14:00

1 Answer 1


The intensity will not increase (of course you have to be careful in the definition of intensity because it's trivial that intensity depends on the speed of shuttle since it's, in its simplest form, defined as the rate of flow of photons per unit time), but the frequency will change, and all the photons from the Cosmic Microwave Background (CMB) will become gamma rays, which could more kill the people in the shuttle more likely than affecting the ship itself.

However, the rocket will be destroyed not because of the photons, but more likely because of the atoms scattered in the universe, which will turn into projectiles hitting the rocket with the speed of light. I think that's a bigger problem that photons which can be shielded by lead.

Urlich Walter has published many articles about this, and gave a seminar I attended in PSI (Paul Scherrer Institute in Switzerland). Take a look at his publications.

  • $\begingroup$ Maybe intensity is not the right word. I was thinking about the headlight effect - a relativistic aberration, that causes rays of light to be tilted towards the direction of motion of the observer. But when I think about it now, it shouldn't have any effect on the energy received by the rocket. $\endgroup$
    – Eiver
    Nov 19, 2013 at 11:56
  • $\begingroup$ Fast atoms will not necessary do any damage. Since they go fast the damage that they can produce in a given material thickness will be negligible. Am I missing something? For example, en.wikipedia.org/wiki/Stopping_power_%28particle_radiation%29 $\endgroup$
    – alfC
    Jun 25, 2014 at 22:36

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