A topopolis is a tube-like space habitat, rotating to produce gravity on the inner surface, which is extended into a loop around the local star. Topopoli can be looped several times around the local star, in a geometric figure known as a torus knot

Torus knot

In knot theory, a torus knot is a special kind of knot that lies on the surface of an unknotted torus in R3. Similarly, a torus link is a link which lies on the surface of a torus in the same way. Each torus knot is specified by a pair of coprime integers p and q. A torus link arises if p and q...

. The concept was invented by Pat Gunkel and mentioned by Larry Niven

Larry Niven

Laurence van Cott Niven / ˈlæri ˈnɪvən/ is an American science fiction author. His best-known work is Ringworld , which received Hugo, Locus, Ditmar, and Nebula awards. His work is primarily hard science fiction, using big science concepts and theoretical physics...

 in "Bigger than Worlds" (1974). Topopoli are also called cosmic spaghetti.

A topopolis has been compared to an O'Neill cylinder extended in length so that it encircles a star

Star

A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...

.

A normal topopolis would be hundreds of millions of miles/kilometers long and at least several miles (kilometers) in diameter.

There is a somewhat well described example of a topopolis in the book Matter

Matter (novel)

Matter is a science fiction novel from Iain Banks, under the name Iain M. Banks in his Culture series. It was published on 25 January 2008.Matter was a finalist for the 2009 Prometheus Award.- Creation :...

 by Iain Banks

Iain Banks

Iain Banks is a Scottish writer. He writes mainstream fiction under the name Iain Banks, and science fiction as Iain M. Banks, including the initial of his adopted middle name Menzies...

. This particular topopolis looped its system star many times in various braidings, housing trillions of sentient 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, described by the author as a "haze".

External links

• Cableville, a fictional topopolis at Orion's Arm
• http://lib.luksian.com/textsfnf/engl/129/