Question: In [Iain M. Banks'](https://en.wikipedia.org/wiki/Iain_Banks), fairly rockin' [Culture novel](https://en.wikipedia.org/wiki/The_Culture), [*Consider Phlebas*](https://en.wikipedia.org/wiki/Consider_Phlebas) a good third of the book takes place on what is called the **"Vavatch Orbital"**. An orbital is apparently a massive artificially created megastructure, similar to the [Death Star](https://en.wikipedia.org/wiki/Death_Star) or the titular [Halo](https://en.wikipedia.org/wiki/Halo_%28megastructure%29).

At one point in the book the Vavatch Orbital is described as a minor orbital, not as big as a ring or a sphere. Then later it is almost directly described as having a ring shape. Still earlier in the story it is described as a bucket being swung in circles, though this description maybe used only to describe how the orbital uses centrifugal force instead of actual gravity.

Whatever the size, the orbital has to have enough sea space for a Megaship (a city sized ocean ship) to travel for more than a century before reaching land again.

[Wikipedia tends to suggest that all orbitals are rings](https://en.wikipedia.org/wiki/Orbital_%28The_Culture%29), but then why the mention of a sphere, or that Vavatch is not big enough to be a ring?

Answer: 
Here's how Banks describes Orbitals himself, in his essay [*A Few Notes On The Culture*](http://www.vavatch.co.uk/books/banks/cultnote.htm) :

> 
> Perhaps the easiest way to envisage an Orbital is to compare it to the idea that inspired it (this sounds better than saying; Here's where I stole it from). If you know what a Ringworld is - invented by Larry Niven; a segment of a Dyson Sphere - then just discard the shadow-squares, shrink the whole thing till it's about three million kilometres across, and place in orbit around a suitable star, tilted just off the ecliptic; spin it to produce one gravity and that gives you an automatic 24-hour day-night cycle (roughly; the Culture's day is actually a bit longer). An elliptical orbit provides seasons.
> 
> 
>
[Look to Windward](https://en.wikipedia.org/wiki/Look_to_Windward) contains a description of an Orbital in chapter 12

> 
> 'It is what they call an Orbital; a band of matter in the shape of a very thin bracelet, orbiting around a sun - in this case the star Lacelere - in the same zone one would expect to find an habitable planet.
> 
> 
> 'Orbitals are on a different scale from our own space habitats; Masaq', like most Culture Orbitals, has a diameter of approximately three million kilometers and therefore a circumference of nearly ten million kilometers. Its width at the foot of its containing walls is about six thousand kilometers. Those walls are about a thousand kilometers high, and open at the top; the atmosphere is held in by the apparent gravity created by the world's spin.
> 
> 
> 'The size of the structure is not arbitrary; Culture Orbitals are built so that the same speed of revolution which produces one standard gravity also creates a day-night cycle of one of their standard days. Local night is produced when any given part of the Orbital's interior is facing directly away from the sun. They are made from exotic materials and held together principally by force fields.
> 
> 
> [...]
> 
> 
> 'Each Orbital is different and each Hub has its own personality. Some Orbitals have only a few components of land; these are usually square parcels of ground and sea called Plates. On an Orbital as broad as Masaq' these are normally synonymous with continents. Before an Orbital is finished, in the sense of forming a closed loop like Masaq', they can be as small as two Plates, still three million kilometers apart but joined only by force fields. Such an Orbital might have a total population of just ten million humans. Masaq' is toward the other end of the scale, with over fifty billion people.
> 
> 
>