Mission Of Gravity

Author: Hal Clement

If you want to know what hard sf is really all about, then this is the novel you have to read. Hal Clement didn't believe in having human antagonists in his novels, he reckoned that the universe is big enough and bad enough as it is to provide all the opposition you need to make a gripping story. And when you read this, you'll see why. Antagonists don't come much bigger or badder than the planet Mesklin.Mesklin is highly oblate, which means it is flattened at the poles. This affects gravity, which is three times earth normal at the equator, but a massive 700g at the poles. So when a human probe is lost near the pole, the only way they can recover it is with the help of the locals.They hire a trader, Barlennan, to find the probe in return for vital information about the planet's weather, which can be dangerous for the Mesklinites. These are low, centipede-like beings who have learned to move slowly and carefully, and who are terrified of a fall under any circumstances. The novel follow's Barlennan's journey, and is mostly devoted to exploring how it is affected by the different conditions shaped by the varying gravity along the way. Mission of Gravity is one of the definitive examples of worldbuilding. It's a story we trust because we trust all the scientific thinking that went into devising such a planet. Still today it is the novel you'd point to as an example of how to do hard sf properly.

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Hal Clement wrote two further novels set on Mesklin, Close to Critical and Star Light, which form a loose trilogy with continuing characters. But it is still the original that is the most startling and effective of the three.

His other novels tended to follow the same pattern, with a competent hero (who may be human or alien) solving the problems inherent in an extreme environmental situation. For instance, Cycle of Fire, which may be read as a precursor of The Helliconia Trilogy by Brian Aldiss, is set on a world where the seasons each last forty years.

Other examples of hard sf include Cities in Flight by James Blish, in which flying cities powered by a kind of antigravity device known as a spindizzy tour the universe looking for work and encountering a variety of conditions. Or Tau Zero by Poul Anderson, in which a ship incapable of faster than light travel finds itself, as a result of an accident, incapable of stopping acceleration. The novel is full of the technical ramifications of issues like time dilation and relativity.