Something that's been on my mind from time to time is the speed of light, it's often referred to as a constant.
The escape velocity of a black hole is greater than the speed of light, so light can't escape it. In my mind, this means that light is travelling at zero mps because it's trapped within the event horizon.
The escape velocity of a neutron star is less than the speed of light, so light can escape it at it's normal constant velocity.
After a supernova from a star with enough mass to become a black hole, as the dust collapses on itself, there is a point where the gravity exceeds the escape velocity of light. At that point, does the speed of light change make a sudden change or is it gradual?