Surface gravity 17.9 – 5.7 m/s², 1.8 – 0.58 g
Day length 7.76 ks, 2.15 hours, 0.090 Earth days
Year length 11.5 Ms, 0.364 Earth years
Month length 233 ks, 64.7 hours, 30 local days
Seasonal change Severe
Atmosphere 924 kPa, composition He (692 kPa), N2 (214 kPa), O2 (17 kPa), CO2(1 kPa)
Minor effects of CO2 toxicity
Fires do not burn
Climate Moderate
Notable features Very fast rotation, gravity varies from poles to equator
Population 3.1 million, primarily Gummis
Wormhole terminus Uuniinlee
Prominent businesses Agriculture, biotech, medicine

A gravity map of Zhiroom, with local gravity measured in m/s² at selected points (indicated with + signs). The spin axis is top to bottom in the page.

Natural Features

Zhiroom is a large world that spins so fast that it is drawn out into a flying saucer shape by the centrifugal force. The centrifugal force combined with the gravitational force and varying distance from the world's center means that the felt gravity varies considerably over its surface. At the poles, the gravity is crushing, while the equatorial gravity is noticeably light.

Zhiroom has two moons, a giant moon in the same class as Luna and Europa of the Sol system, and a smaller rockball moon in the larger moon's L4 Trojan point.

Zhiroom's mass is high enough that it can retain helium gas, resulting in a dense atmosphere of trimix (helium, nitrogen, and oxygen). Fortunately for visitors, helium has nearly no narcotic effect, and there isn't enough partial pressure of nitrogen to cause narcosis – although some visitors may get impaired by alcohol or other drugs just a little bit easier. The low molecular weight of the atmosphere results in a high speed of sound and high thermal conductivity. With the exception of Mants, who make sounds via stridulation, voices sound high and squeaky. The high atmospheric thermal conductivity means cool weather can feel even colder for a given temperature and wind speed.

Unfortunately, the carbon dioxide level of Zhiroom is a touch high. Gummis do not mind, but other species feel that the air is "stuffy" and may suffer headaches, irritability, drowsiness, insomnia, and difficulty thinking straight. Most individuals are able to acclimate after several weeks, and gene surgery is available that allows greater carbon dioxide tolerance. The high level of CO2 does at least keep the planet warm given that it is relatively far from its sun.

The flattening of the world and its moderate inclination means that the arctic (or antarctic) circle covers most of each hemisphere, sparing only the equatorial regions. The high Coriolis force results in many Hadley cells which hinder the transport of atmospheric heat between the hemispheres. As a result, even though the axial tilt is fairly typical for a habitable world, there are large seasonal swings over much of the planet, and the high gravity regions will be in full sunlight for half a year and then in darkness for the next half. Fortunately, the short year prevents the freezing, lightless winter from being too long. The equatorial regions are much more clement, and at around the 9 – 10 m/s² (0.9 – 1 g) latitude lines, the climate is comfortably temperate.

Zhiroom has an active biosphere, from squat lumps covered with photosynthesizing lichen-like crud at the poles to spindly "trees" with feathery leaves near the equator. High gravity regions often feature "rope flora" - tangled masses of liquid containing tubes sprawled across the landscape. In the low gravity areas, the settling rate is low enough that air plankton often bloom in vast reddish clouds, leading to an entire ecology of air filter feeders. Gummiland life adapts well to the conditions of Zhiroom, particularly in the moderate gravity areas, and many species are now established and invasive.

Zhiroom's weather is influenced by the high rate of rotation and consequent high Coriolis forces. Cyclonic storms (hurricanes) are frequent but weak. Tornadoes are also frequent, but strong. The dense atmosphere results in a deep troposphere, resulting in weather systems over a wide range of altitudes and a lot of room for truly towering storm systems to develop. Summer in the temperate and polar regions, and regularly throughout the year in equatorial regions, often sees severe storms with multiple tornadoes, high winds, drenching rain, and frequent lightning.

A massive world like Zhiroom will have plenty of internal heat, leading to extensive mantle convection and plate tectonics. This in turn leads to high mountains along plate boundaries, island arc and continental arc volcanism, frequent but irregular earthquakes, and interesting geology with plenty of dikes, sills, basin and range landscapes, thrust faults, rift valleys, calderas, and so on. In addition, it has a considerable level of hotspot/heat pipe volcanism, leading to large shield volcanoes. Combined with the active tectonic plate movements, this leads to many volcanic island chains.


The last major world explored and colonized before The Bump in the Night, Zhiroom was attractive to Gummis for its comfortable environment. Although it started out with a reasonable seed population, the difficulties following the Verge's isolation limited its growth for a gigasecond or two. Now that Verge society is back on a solid footing, Zhiroom is beginning to see increased growth and development.


As typical of a Gummi dominated world, there is not much of a government to speak of. Local coordination committees of civic-minded citizens suggest voluntary guidelines, which are in turn given suggestions by the global Zhiroom coordination committee.


Zhiroom is largely agricultural, growing Gummiland crops and exporting native spices and intoxicants. Recently, it has attracted investment from biotech and medical firms.


The population of Zhiroom is mostly Gummis. A significant Pirang minority is present, and some Tweechi flocks have settled on the planet. The equatorial regions are popular vacation spots for Tweechi visitors.



The main city and wormhole terminus of Uuniinlee has experienced a recent boom due to the re-location and development of several biotech and med-tech Nogis to the region. Its wormhole station is still a basic, small town affair and will likely need to be expanded soon to allow for the increase in traffic. Uuniinlee is located where the local gravity is 13.2 m/s² (1.3 g). The environment is lightly forested, although the trees are short, thick, and stout. Uuniinlee has a small but growing Gummiland style land reef, which is a popular recreational park.

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