Why is it that light cannot escape from black holes? Is light made of matter? Does gravity affect light?
Hi. Light always travels in a straight line. Gravity distorts space so the line, although still straight , seems curved. In a black hole the curve closes in on itself.
Light is not made of matter, but gravity does affect light anyway.
When a object collapses , its gravity and density increases and if radius of the object tends to zero, its density and gravity tend to infinite. The escape velocity in these regions, becomes so large and it will be higher than the speed of the light. So nothing, including light can escape from these regions known as black holes.
Photons travel through space, and space is curved by gravity. In 1905, Einstein predicted that during an ecclipse, we should see a particular star that was, in fact, *behind* the sun. Sure enough, when the ecclipse occured, the star was visible - appearing just a little to the north west of the sun. The sun's gravity curved the star's light around, so we could see the star - even though the sun was physically in front of it. In a black hole, or more accurately - inside a black hole's Event Horizon - the speed needed to escape is above the speed of light - indicating that gravity has bent space so much that light itself cannot escape.
Light is not made of matter, and is not itself affected by gravity as Newtonian physics would suggest. In Einstein's model, gravity is actually a warp or bend in spacetime. Light travels in straight lines through space, but if space itself is warped then the light will follow the resulting curve. In the case of a black hole the space is so warped that the light ends up doubling back on itself and just cannot escape.
