Inspired by a conversation with a friend, and my growing interest in Erik Verlinde’s entropic construction of gravity, here is a video of Raphael Bousso of UC Berkeley giving a fairly non-technical lecture explaining the holographic principle. Dr. Bousso does a good job of building up to concepts like Planck length and Schwarzschild radius (a term I don’t recall him actually using in the video) from simple principles.
An aside: I don’t recall having been explicitly introduced to the idea that the density of a black hole decreases as its mass increases before. In fact I’m not sure that black hole density ever came up at all in my modern physics class, which is the only place I worked with Swarzschild radii. It’s obvious once presented, but when I got to that part of the video I was shocked to find I had been completely unaware of such a fundamental characteristic of black holes.