Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

Possible Duplicate:
Double light speed
Someting almost faster than light traveling on something else almost faster than light

Well I've been wondering quite a long time about this problem. If you had let's say 10 rockets, each of them having a length enough to provide space for an acceleration of another rocket inside. Each rocket would accelerate from 0, to 1/10 of speed of light. From the observers point of view, wouldn't the last rocket achieve the speed of light (since the speeds add up).

share|cite|improve this question

marked as duplicate by Qmechanic, dmckee Sep 21 '12 at 20:43

This question was marked as an exact duplicate of an existing question.

I know that you need infinite energy to accelerate an object of a certain mass to the speed of light, but the rockets, are not even approaching the speed, so that doesn't work here. – Bartlomiej Lewandowski Sep 21 '12 at 20:36
so what you are saying, that comparing the speeds of rocket 9,10 ,their speed difference would be much smaller than 1/10 of the speed of light, but from the rocket nr 10 point of view, the difference would be exactly 1/10 speed of light – Bartlomiej Lewandowski Sep 21 '12 at 20:42