Apollo 11

Pete Mao (Caltech) sent me a note for Newton's birthday, pointing out that all sensible transfer orbits to and from the Moon ought to have half-periods (transfer times) of about 5 days. And yet, as he also pointed out, Apollo 11 came back in 2.5 days. What gives? Did NASA waste fuel to improve the filmic value of the mission, or does the enormous tidal effect of the Sun change the sensible set of transfer orbits for some reason I don't understand?

(His note on this subject also had a nice discussion about what a 5-year-old wants when he or she asks a scientific question, and why just answering it is the wrong response.)