 Why of these is not a reason Houlihan agreed to help the little people?
But its small, mischievous pilots had a rendezvous with destiny—on Earth. It was in a park near the nuclear propulsion center—a cool, green spot, with the leaves all telling each other to hush, be quiet, and the soft breeze stirring them up again. Perhaps you had better take my word for it that without this equation—correctly stated, mind you—mankind would be well advised not to make a first trip to the moon. Not children, but a group of little people, hard at work. I had seen them first as a boy of eight, and then, very briefly again, on my tenth birthday. "And mine's Houlihan, as I've told you.
 He figured he was the only one with knowledge to help them solve their problem
 He saw it as an opportunity to clear his head about his own work  He figured their ship could act as a test case for his work  He felt a kinship with them because of his family's history  He figured he was the only one with knowledge to help them solve their problem