Today a friend of mine posed me a paradox involving black-holes, one that I couldn't solve.
Suppose we have planet, with a density such that it is almost to the point of turning into a black hole, armed with a powerful laser on the surface (kind of like Star War's Death Star) capable of shooting down any star ship. Now I, on a really fast spaceship (for the sake of discussion let's say around 10% of the speed of light) approach this planet.
Now, because of relativistic effects, from my point of view the planet will shrink, keeping mass constant, therefore increasing its density and finally turning in a black hole. Because of that the laser will never be able to escape the planet, and I'll be fine.
Instead, from the planet's point of view, nothing as really changed, only a puny space-ship is flying into its direction, the laser will shoot and take me down.
How is this possible?