# **Mesklin**

is a [fictional planet](https://en.wikipedia.org/wiki/Fictional_planet) created by [Hal Clement](https://en.wikipedia.org/wiki/Hal_Clement) and used in a number of his [hard science fiction](https://en.wikipedia.org/wiki/Hard_science_fiction) stories, starting with *[Mission of Gravity](https://en.wikipedia.org/wiki/Mission_of_Gravity)* (1954). Alongside the novel's original 1953 [serialization](https://en.wikipedia.org/wiki/Serial_(literature)) in *[Astounding Science Fiction](https://en.wikipedia.org/wiki/Astounding_Science_Fiction)*, Clement published an essay titled "**Whirligig World**" on how he designed the planet to have the properties he wanted. The idea came from an object that was at the time believed to exist in the [61 Cygni](https://en.wikipedia.org/wiki/61_Cygni) system, and which might represent an [extrasolar planet](https://en.wikipedia.org/wiki/Extrasolar_planet).

The planet is distinctive for the interaction of its strong [gravity](https://en.wikipedia.org/wiki/Gravity) with the [centrifugal force](https://en.wikipedia.org/wiki/Centrifugal_force) due to its fast rotation, giving it a [gradient](https://en.wikipedia.org/wiki/Gradient) in the perceived force of gravity from 3 *[g](https://en.wikipedia.org/wiki/Gravity_of_Earth)* on the equator to 665 *g* on the planet's poles. It is inhabited by [native lifeforms](https://en.wikipedia.org/wiki/Extraterrestrial_life), including an intelligent [centipede](https://en.wikipedia.org/wiki/Centipede)-like species, the **Mesklinites**.

Mesklin is considered a prototypical example of hard science fiction [worldbuilding](https://en.wikipedia.org/wiki/Worldbuilding), an exotic milieu that nevertheless accords with known facts and laws of physics. While the planet itself is vastly dissimilar to [Earth](https://en.wikipedia.org/wiki/Earth), its inhabitants are commonly regarded to be noticeably humanlike in behavior if not in appearance. Mesklin is sometimes viewed as the main character of *Mission of Gravity*.

## Description

Mesklin is a fictional planet orbiting one of the stars in the [61 Cygni](https://en.wikipedia.org/wiki/61_Cygni) [binary](https://en.wikipedia.org/wiki/Binary_star) star [system](https://en.wikipedia.org/wiki/Star_system).[[2\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-DictionaryOfScienceFictionPlacesMesklin-2)[[3\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-Raham2004-3) Its mass is sixteen times [that of Jupiter](https://en.wikipedia.org/wiki/Jupiter_mass), or 4,800 times [Earth mass](https://en.wikipedia.org/wiki/Earth_mass).[[4\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-Goswami1983-4)[[5\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-CriticalStudiesHalClement-5): 215  It has a very high [rate of rotation](https://en.wikipedia.org/wiki/Rotation_period_(astronomy)), one day on the planet lasting only eighteen minutes.[[2\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-DictionaryOfScienceFictionPlacesMesklin-2) As a result, the planet is significantly flattened with a large [equatorial bulge](https://en.wikipedia.org/wiki/Equatorial_bulge): the diameter at the equator is 77,000 km while the diameter between the poles is slightly below 32,000 km. By comparison, the [diameter of Earth](https://en.wikipedia.org/wiki/Diameter_of_Earth) is approximately 13,000 km.[[2\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-DictionaryOfScienceFictionPlacesMesklin-2)[[3\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-Raham2004-3)[[4\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-Goswami1983-4) The planet thus has a significantly higher mass than [Jupiter](https://en.wikipedia.org/wiki/Jupiter) within a much smaller volume, and its [core](https://en.wikipedia.org/wiki/Planetary_core) is made up of [collapsed matter](https://en.wikipedia.org/wiki/Degenerate_matter).[[4\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-Goswami1983-4)[[6\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-Pierce1987AliensAndAlienWorlds-6) The [surface gravity](https://en.wikipedia.org/wiki/Surface_gravity) is very high at 665 times [Earth gravity](https://en.wikipedia.org/wiki/Earth_gravity) at the poles, but at the equator the effective gravity is only three times Earth's as the rapid rotation produces a significant [centrifugal force](https://en.wikipedia.org/wiki/Centrifugal_force) that counteracts most of the gravitational force.[[7\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-CloseEncountersMesklin-7)

[![Refer to caption](https://upload.wikimedia.org/wikipedia/commons/thumb/3/3c/Mesklin_fictional_fast_rotating_flattened_icy_giant_planet_3_1_1_1.png/250px-Mesklin_fictional_fast_rotating_flattened_icy_giant_planet_3_1_1_1.png?utm_source=en.wikipedia.org&utm_campaign=parser&utm_content=thumbnail)](https://en.wikipedia.org/wiki/File:Mesklin_fictional_fast_rotating_flattened_icy_giant_planet_3_1_1_1.png)Artist's rendering of Mesklin

Mesklin orbits its star in an elongated ellipse, completing a full revolution in 1,800 Earth-days.[[7\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-CloseEncountersMesklin-7)[[8\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-Barron1979MissionOfGravity-8): 1424–1425  The high [orbital eccentricity](https://en.wikipedia.org/wiki/Orbital_eccentricity) combines with a pronounced [axial tilt](https://en.wikipedia.org/wiki/Axial_tilt) to result in an uneven [seasonal cycle](https://en.wikipedia.org/wiki/Season). In the southern hemisphere, the springs and summers are very lengthy (at 28 Earth-months each) and the autumns and winters much briefer (2 months each); the pattern is reversed in the northern hemisphere. The two hemispheres thus have significantly different [climates](https://en.wikipedia.org/wiki/Climate).[[8\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-Barron1979MissionOfGravity-8): 1425 [[9\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-Hassler1982-9): 87  The planet is cold, with average temperatures ranging from −50 °C at the [closest approach to its star](https://en.wikipedia.org/wiki/Periapsis) to −180 °C at the furthest point in its orbit.[[7\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-CloseEncountersMesklin-7)[[10\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-HalClementHardScientist-10)[[11\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-NaturalConceptualWorlds-11): 73  Mesklin is itself orbited by two small [moons](https://en.wikipedia.org/wiki/Natural_satellite) and has a large [ring system](https://en.wikipedia.org/wiki/Ring_system).[[3\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-Raham2004-3)[[5\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-CriticalStudiesHalClement-5): 215 

The surface is covered mostly by [methane](https://en.wikipedia.org/wiki/Methane) (CH4) and [ammonia](https://en.wikipedia.org/wiki/Ammonia) (NH3), both mainly in the [liquid](https://en.wikipedia.org/wiki/Liquid) state; the oceans are primarily made up of methane, while the ammonia is also present as snow.[[2\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-DictionaryOfScienceFictionPlacesMesklin-2)[[3\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-Raham2004-3) The atmosphere is principally composed of [hydrogen](https://en.wikipedia.org/wiki/Hydrogen), and its density decreases with increasing altitude to such a degree that [atmospheric refraction](https://en.wikipedia.org/wiki/Atmospheric_refraction) through the successive layers produces the [optical illusion](https://en.wikipedia.org/wiki/Optical_illusion) that an observer on the surface perceives the ground as curving upwards, as if living on the concave inside of a bowl rather than the convex surface of a [spheroid](https://en.wikipedia.org/wiki/Spheroid).[[3\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-Raham2004-3)[[12\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-StanwayPeculiarPlanets-12)

The planet is [inhabited by various lifeforms](https://en.wikipedia.org/wiki/Extraterrestrial_life).[[2\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-DictionaryOfScienceFictionPlacesMesklin-2)[[9\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-Hassler1982-9): 89  The [intelligent native inhabitants](https://en.wikipedia.org/wiki/Extraterrestrial_intelligence), the Mesklinites, resemble [centipedes](https://en.wikipedia.org/wiki/Centipede) or [caterpillars](https://en.wikipedia.org/wiki/Caterpillar).[[2\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-DictionaryOfScienceFictionPlacesMesklin-2)[[3\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-Raham2004-3)[[8\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-Barron1979MissionOfGravity-8): 1424  They are 40 cm long and 5 cm wide, with eighteen pairs of legs ending in [suckers](https://en.wikipedia.org/wiki/Sucker_(zoology)) as well as a forward pair of [pincers](https://en.wikipedia.org/wiki/Pincer_(biology)) for manipulation and a rear pair for attaching to the ground.[[3\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-Raham2004-3)[[5\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-CriticalStudiesHalClement-5): 218 [[13\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-BarlowesGuideToExtraterrestrialsMesklinite-13) They have four eyes and [mandibles](https://en.wikipedia.org/wiki/Mandible_(arthropod_mouthpart)).[[3\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-Raham2004-3)[[13\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-BarlowesGuideToExtraterrestrialsMesklinite-13) They have a tough [exoskeleton](https://en.wikipedia.org/wiki/Exoskeleton) that allows them to withstand the planet's strong gravity.[[9\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-Hassler1982-9): 88  They have no lungs but breathe hydrogen by absorbing it directly from the atmosphere in a manner similar to that used by the [respiratory system of insects](https://en.wikipedia.org/wiki/Respiratory_system_of_insects), whereas [oxygen](https://en.wikipedia.org/wiki/Oxygen) is toxic to them.[[3\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-Raham2004-3)[[5\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-CriticalStudiesHalClement-5): 216, 218 [[14\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-Allen1974-14): 107–108  They are able to survive while submerged for extended periods of time by breathing dissolved gases.[[14\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-Allen1974-14): 107–108  Their lifespan is much longer than that of humans.[[9\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-Hassler1982-9): 89  They have a strong [fear of heights](https://en.wikipedia.org/wiki/Acrophobia) and of being underneath objects, owing to the danger posed by such things in a high-gravity environment.[[2\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-DictionaryOfScienceFictionPlacesMesklin-2)[[8\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-Barron1979MissionOfGravity-8): 1425 [[9\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-Hassler1982-9): 88–89 [[14\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-Allen1974-14): 108  For similar reasons, they have no concept of flying or throwing things.[[8\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-Barron1979MissionOfGravity-8): 1425  Their society is [pre-industrial](https://en.wikipedia.org/wiki/Pre-industrial_society) with rudimentary technology including seafaring vessels.[[2\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-DictionaryOfScienceFictionPlacesMesklin-2)[[3\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-Raham2004-3)[[8\]](https://en.wikipedia.org/wiki/Mesklin#cite_note-Barron1979MissionOfGravity-8): 1424