Mission of Gravity is a science fiction novel by Hal Clement. The novel was serialized in Astounding Science Fiction magazine in April–July 1953. Its first hardcover book publication was in 1954, and it was first published as a paperback book in 1958. Along with the novel itself, many editions (and most recent editions) of the book also include "Whirligig World", an essay by Clement on creating the planet Mesklin that was first published in the June 1953 Astounding.
Clement published three sequels to Mission of Gravity: a 1970 novel called Star Light, a 1973 short story called "Lecture Demonstration", and a 2000 short story, "Under". Mission of Gravity was nominated for a "Retro Hugo" Award for the year 1954.
The story is set on a highly oblate planet named Mesklin, which has surface gravity that varies between 700 g at the poles and 3 g at the equator. The story is told from the points of view of one of the local intelligent life forms and a human explorer. The locals are centipede-like, in order to withstand the enormous gravity, and terrified of even small heights (because in 700 g even a tiny fall is fatal). (See Mesklin for a more comprehensive description of the planet's characteristics.)
The native protagonist, Barlennan, captain of the Bree, is on a trading expedition to the equator, where the gravity is a tiny fraction of what his culture is used to. Prior to the story's opening, a human scientific probe has become stranded at one of the planet's poles, and team member Charles Lackland is dispatched to the equator where he has met Barlennan by chance. Lackland is barely able to survive (machine-aided) what to the captain is the incredibly light gravity, but has managed to teach the Mesklinites English, and enlist the Bree to journey to the pole and recover the probe, in return for information about the violent weather which often plagues such expeditions. Communication is achieved through an audio-visual radio built to function in a high-gravity environment, which is treated as magical by other intelligences encountered on the planet.
Along the way to the pole, the ship encounters and overcomes a variety of obstacles, some of which the humans help with using their superior scientific knowledge, and some of which rely on the cunning of Barlennan and his crew. They are captured by various lifeforms similar to themselves, but who live in the lower-gravity areas and have developed projectile weapons and gliders. Gradually, with human help, they gain an understanding of these and manage to escape.
Barlennan has been dissatisfied with the humans' efforts to seemingly avoid explanation of anything scientific, and almost withholds the probe when they finally reach it; but the humans convince them that a scientific background is needed to understand the advanced equipment in the probe, and a deal is reached whereby the humans will slowly educate the Mesklinites. The novel provides an exposition on how the weather, geology and atmosphere of the seas and the pole are affected by the local conditions, and sees the Mesklinites overcoming their fear of gravity as they learn to view it scientifically, eventually harnessing aerodynamics to make the Bree fly at the poles.
Mission was the runner-up for the 1955 International Fantasy Award for fiction. Boucher and McComas found Mission "compact and unified, with a good deal of adventurous excitement" and characterized it as "a splendid specimen of science fiction in the grandest of grand manners."
Wayne Barlowe illustrated the Mesklinites in his Barlowe's Guide to Extraterrestrials.
A significant theme of the novel is the universality of physical law; regardless of the exotic nature of the location, the underlying rules of the universe are constant. Even in an environment of hundreds of gravities, the story states, a boat will still float (assuming structural integrity), because even if the weight of the boat is considerably greater than it might be, for instance, at Mesklin's equator, the weight of the fluid it displaces is also greater. A secondary theme deals with the scientific method, and the necessity of proceeding one step at a time. The trading ship's captain, originally skeptical of the human explorers' claim that teaching him to make the various devices they use would take prohibitively long, gradually grows to accept this explanation, and sees the value of walking before he can run, as it were—a theme not at all surprising in a work by Hal Clement, a high school science teacher.
It is most often praised for the thoroughness and care with which Clement designed and described Mesklin — even today, it is considered one of the definitive examples of worldbuilding. Although Clement has stated that his original calculations concerning the polar gravity of Mesklin were inaccurate (he later estimated the polar gravity should have been ~250 g instead of 700), the exploration of what existence might be like in such extreme conditions is detailed, convincing, and persuasive. The novel is frequently invoked in discussions of the sense of wonder, the sensation of dawning comprehension and understanding of a larger context for a given experience, that many readers of science fiction point to as the reason why they pursue the genre.
The personalities of Clement's alien characters have been criticized as being "too human" or not "alien enough", as failing to be, in the words of John W. Campbell "something that thinks as well as a man, but not like a man".Chinese (Simplified): 重力使命, 2006 (first edition)
Finnish: Painovoima 700, 1983 (first edition)
French: Question de poids, 1971 (first edition)
Turkish: Ağır Görev
German: Unternehmen Schwerkraft, 1959 (first edition)
Hebrew: שליחות כבדת-משקל, first edition: 1981
Russian: Экспедиция «Тяготение», 1972 (first edition, translated by Arkady Strugatsky).
Italian: Stella Doppia 61 Cygni, 1954 (first edition)
Dutch: Een zaak van gewicht, 1971 (first edition)
Hungarian: Az elveszett rakéta, 1978
Swedish: Uppdrag av vikt, 1983
Korean: 중력의 임무, 1996