The event horizon represents the gravitational point of no return. Once past the event horizon, the gravitational pull of a black hole reaches a strength that is inescapable, and not even light can reemerge from the prison of the singularity. Another way of thinking about the event horizon is as the finite point in space where the escape velocity is exactly equal to the speed of light. Some very interesting geometrical properties arise from this point in space. To an outside observer, the horizon is believed to appear as a static, unmoving spherical surface (as portrayed in these images). In reality, the event horizon is actually moving outward at the speed of light, and it is this outward movement that does not allow light to escape. Since the horizon is moving away from the singularity at the speed of light, it would be necessary to exceed light-speed to escape, which as far as we know is impossible. The motion of the event horizon may not make sense, and that is because it doesn’t in our normal understanding of how things move through space. The movement of the horizon is similar to Alice having to run as fast as she can just to remain stationary in “Through the Looking-Glass”.
Once past the event horizon, all matter is doomed to fall towards the singularity (center of the black hole). The extreme distortion of spacetime near the center of a black hole has interesting mathematical consequences regarding general relativistic time. As the radial distance (r) from the singularity decreases, Einstein’s mathematics tell us that the time coordinate (t) grows larger and larger (as r↓, t↑). Eventually, all matter inevitably reaches the singularity (r=0), theoretically sending time to infinity. Time stops.
The stoppage of time is a phenomenon that does not seem possible. The intuitively backwards and seemingly impossible conclusions that are derived from general relativity, combined with more recent philosophical and mathematical work, are exposing possible flaws in our understanding of space and time. I want to dedicate the next few posts to exploring these potential flaws and hopefully spark discussion on our perceptions of the cosmos vs. its reality.