 One of the key implications for bending of light is its impact on what's physically possible in heavily curved spacetime. Here's a two-dimensional slice of the future light cone that we developed in the previous segment on special relativity. This purple line represents a path by anything with mass. It's called the whirl line and can be anywhere inside the light cone. In this representation whirl lines have to remain between the two arms of the light cone because nothing can travel faster than the speed of light. The speed of light lines are the divider between events that are in your future, if it's your light cone, and events that are not. By in your future I mean that you can be connected to them physically in some way. Now suppose there is a great mass energy density to the left of the cone. The light would be bent in its direction. We see that points that were impossible to reach before now fall inside the light cone and are reachable. And we see that points that were reachable inside the cone now fall outside the cone and are no longer reachable. This is light cone tipping. The closer we get to the source of the gravity, the greater the space time curvature. And the larger the matter curving the space, the greater the curvature. We'll take another look at this when we get to black holes.