Question

A spaceship is traveling with a speed of 0.7c with respect to a stationary observer towards the observer. A laser beam inside the spaceship is turned on that is directed away from the observer. What is the speed of the laser light as measured by the stationary observer?

Answer 1

The speed of the laser light is c, for observers in any non-accelerated system of coordinates.

Step-by-step explanation:

The special relativity is based upon two postulates, one of them is the principle of relativity that says that universal laws must be the same for all inertial (non-accelerated) systems of reference.

The second one is the invariability of c (the speed of light), wich states that the light propagates in empty space with velocity c, and this is independent of the state of motion of the transmitter body, and the state of motion of the observer body.

Therefore, in this problem, c is the velocity of light as seen from the stationary point, and also from the spaceship.

The answer in particular, is that for the stationary observer, the velocity of the beam of laser, is c.