The Physics of "Gravity" and "Interstellar"

Hanukkah is a Jewish holiday celebrating a miracle whereby oil sufficient for just one day burned for eight.  Over this past week, an entirely different miracle took place: I, a father of two young girls watched two movies, none of which contained a single princess.

I really got my nerd on: I rented "Gravity" and then went to the theater to see "Interstellar".  Both films feature a lot of physics, but they could not be more different.  "Gravity" is a ninety minute expedition featuring orbital mechanics, while general relativity weaves its way through the three hours of "Interstellar".

You are probably expecting me to dissect these two films and expose all of their scientific inaccuracies.  In truth, I enjoyed both of them immensely, but would like to address one major problem with each one.