|MadSci Network: Physics|
Hello Vitalii. Gravity, according to Einstein's principle of relativity, does more than just attract objects toward one another. It curves the very fabric of space and time. To an observer inside a black hole, light is moving at light speed. This is because a really massive gravity well makes space-time warp so much that a clock inside a black hole moves very slow and a measuring stick becomes very small. But since our observer is moving slow himself, and has shrunk to the same dimension as the measuring stick, he would still say light moves at 300,000,000 kps. Now for the complicated part of the question - we need to imagine a ship sailing the oceans of Earth. It can sail in two dimensions, toward the horizon ahead or behind, or to the horizon on the left or on the right. It can sail all around the three dimensional world. But it never leaves sea level, which is two dimentional. With that image in mind, let's consider the event horizon of a black hole. Light can travel along the curve of an event horizion just as a sailing ship can travel along the curve of the Earth. But just as gravity keeps our ship from flying away from the Earth, gravity keeps light from escaping the borders of an event horizon. This does not limit the speed of light, just the available directions it can go. Due to the relativistic nature of the universe, the light inside a black hole appears to always travel in a straight line, just as a ship sailing west appears to always travel in a straight line. But from a sufficently distant observation point, it can be seen that both the light within an event horizion and a ship sailing west are both circling their own worlds. In other words, it's all relative. Where you are when you're watching makes a world of difference in what you see. Layne Johnson
Try the links in the MadSci Library for more information on Physics.