This is definitely a nice, intuitive way to introduce people to the theory of gravity. However, I was a little confused about how he tried to model dark energy.
I think his dark energy illustration doesn't work. Dark energy is the inflation of spacetime, not mass warping spacetime (well at least we don't know what is causing the inflation). To make the illustration work, he needs to pull the whole sheet out along the rim, making the whole sheet bigger.
