So today I had the following question:

If photons have no mass, then how why can't they escape the gravitational pull of a black hole?

So basically the answer I got was pretty cool and comes down to the idea that in the theory of special relativity, gravity isn't a "pull" like we think of it...instead things with large mass distort the idea of a "straight line", so a photon continues to travel straight, but straight is no longer straight because of the large mass of the nearby black hole.

For a better explanation, check out this video.