Mission of Gravity
Reviewed date: 2008 Sep 15
The planet Mesklin is heavy--700 gs at the poles. The equator is an airy 3 gs due to intense centrifugal force. The titanic planet spins so fast it is an oblate spheroid, more like a pancake with a center bulge than like a sphere. Mesklinite life is methane-based and the atmosphere is mostly hydrogen. The intelligent natives are mutli-segmented centipede-like creatures.
The hapless humans have dropped a probe onto Mesklin, but it broke and won't send back any precious data. They make contact with a Mesklinite trading expedition, whose captain agrees to locate the probe and recover the data. The Mesklinite captain, Barlennan, has his own agenda: before he releases the data he demands that the Earth men teach him the principles of science so that he can jumpstart a technological revolution on his world.
That whole subplot is boring. The real fun is seeing the different ways heavy gravity changes the world. Hollow boats don't work, for example: the intense water pressure (methane pressure, actually) crushes the hull. Only solid lighter-than-methane rafts are feasible. Under 700 gs even the tiniest fall is deadly. The Mesklinites have no concept of jumping, flying or throwing. The thought of an unsupported object is incomprehensible.
Hal Clement is a master worldbuilder, and Mission of Gravity shows off his talents. The plot and the characters are secondary, which is just as well because they are not good enough to keep the book interesting. It is Mesklin itself that makes Mission of Gravity worth reading.