If we are flying to a star 125 lightyears away with speed equal to 2,5*10^8m/s, how this distance will appear to us?

Answer 1

Question: If we are flying to a star 125 lightyears away with speed equal to 2,5*10^8m/s, how this distance will appear to us?

Solution

This a question involving Special Relativity. Presumably, you mean 2.5 not 2,5 x 10⁸ m/s and, if so, this would be 84% the speed of light since 2.99 x 10⁸ m/s is the speed of light. According to Special Relativity, everything in your local reference frame would appear normal, hence you would "see" everything exterior to your reference frame subject to the effects of relativistic velocities: the "distance ahead" would appear foreshortened according to the Lorentz contraction γ: 1/√(1-v²/c²) = 1.843: 125 ly/ 1.843 = 67.82 ly.