Atopopolis is a proposed tube-shapedspace habitat, rotating to produceartificial gravity viacentrifugal force on the inner surface, which is extended into a loop around the local planet or star. The concept was invented by writerPatrick Gunkel.
A topopolis has been compared to anO'Neill cylinder, or aMcKendree cylinder, that has been extended in length so that it encircles astar. A "normal" topopolis would be hundreds of millions of miles/kilometers long and at least several miles (kilometers) in diameter.
Topopoles can be looped several times around the local star, in a geometric figure known as atorus knot. Topopolises are also called cosmic spaghetti.
A topopolis with big enoughdiameter could theoretically have multiple levels of concentric cylinders.
Larry Niven (1974) mentioned the idea in a much-reprinted magazine article "Bigger Than Worlds".[1]
Paul Birch referred to this design as the "macaroni habitat". He suggested that, aside from looping around a star, it could instead extend between one star and another, resulting in a habitable area about 100 million times that of the Earth.[2]
In the novelMatter,Iain M. Banks (2008)[3] depicts a topopolis that loops its system star many times in various braidings, and houses trillions of sapient residents. The topopolis was so massive that stray gases from the system collected within the major spacing within the braids by gravitation alone, producing a slight atmosphere between the strands, that the author describes as a "haze".
Dennis E. Taylor (2020)[4] in the bookHeaven’s River features an alien civilization inhabiting a topopolis.
The setting of the worldbuilding projectOrion's Arm has topopoli among the various kinds of megastructures.[5] The system of Cableville is notable for having three topopoli of different sizes and orbits, with names referencing long objects: the innermost isSpaghetti, the one outside it isOuroboros, and the outermost isWyrme.[6]
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