The largest of them have hearts the size of compact cars, with a beat that can be detected two miles away. A small child could crawl through their larger blood vessels. Yet the subjects of the new IMAX film Whales manage to be remarkably elusive and mobile in spite of their immense girth. The humpbacks, one of several species profiled, make an annual pilgrimage from Hawaii to Alaska in search of a square meal. Photographed by Al Giddings (The Abyss, The Deep) and narrated by Star Trek’s Patrick Stewart, Whales is the first IMAX feature sponsored by the National Wildlife Federation. Ultimately, the film raises more questions than it answers. It states, for instance, that little is known of the routes these giant mammals take on their globe-spanning migrations. So why not tag them with radio transmitters? (A “News of the Weird” item a few weeks ago reported that scientists have even developed a microprocessor for attaching to cockroaches!) However, as a primer on the largest creatures ever to inhabit the earth, Whales may float your boat. At 6:30 p.m. Friday-Sunday at the National Air & Space Museum’s Langley Theater, 6th & Independence Ave. SW. $5. (202) 357-2700. (Greg Kitsock)