The first third of Arthur C. Clarke’s seminal science fiction novel “Childhood’s End” deals with the arrival of extraterrestrial beings in massive ships to our planet. The actual form of these aliens is not revealed until later, after the book has jumped ahead to a period when the presence of aliens on Earth has been normalized. Humanity needed time before being able to accept them. It’s an understandable response, given people’s typical emotional reaction to the new and unknown. And it’s a concept, one of a few, thrumming through the new film on a similar subject from director Denis Villeneuve, Arrival.