Larry Niven is a science fiction who has been writing since the 1970s??? He is classified as 'hard' science fiction, as real science plays an important part in his stories, rather than just being a background detail.

In Niven's early works, he described unusual planets where people lived. In later books, he described vast engineering projects in which constructions bigger than planets were made and lived in as worlds. Finally in 1990, he described a 'world' in which people float in zero gravity in a cloud of air. This entry gives a summary of the more unusual worlds.

Plateau

Described in the book 'A Gift From Earth', Plateau is one of the earliest strange worlds. This planet was discovered by an exploratory probe looking for a planet suitable for human colonisation. The probe measured local conditions and decided this planet was ideal for life. When the colonisers arrived after a long, hazardous and one-way journey, they found that the probe was resting on the top of an enormous mountain, twenty miles high. Although conditions on top of the mountain were in fact ideal, the mountain top was only about 40 square miles in area. The entire rest of the planet was uninhabitable, being hot and with very high atmospheric pressure. The resultant society was very strange, and reminiscent of the peculiare practices on Easter Island in the South Pacific, where the natives had a similar problem.

Jinx

Jinx is an elliptical planet, or more technically an ellipsoidal planet. The planet got to be this shape because it was in close orbit around some sort of massive gravity source with huge tidal forces when it solidified. The upshot is that now, the atmosphere has normal thickness at the ends but is extra dense around the middle, which is an enormous hot jungle, inhabited by giant slugs called 'bandersnatches'. What about surface gravity?

The Puppeteer Migration Fleet

The puppeteers are an alien race much older than humanity. They get their name from shamelessly manipulating all other races to their own ends. The puppeteers sent an exploratory faster-than-light ship to the centre of the galaxy and made a frightening discovery: that the core of the galaxy has exploded. In 20,000 years, the shockwave will arrive at our region of the galaxy and all life will be wiped out. The puppeteers didn't waste any time. Before the exploration ship had even returned, they had packed up and left. Rather than building a ship, they launched five planets together. The five planets are arranged in a pentagon and all orbit at the same rate about the common centre of gravity which is the centre of the pentagon. Niven called this system a 'Kemplerer Rosette', an apparent mispelling of the term 'Klemperer Rosette', although a true Rosette is something slightly different.

Ringworld

Niven's greatest invention was the Ringworld, in his book of the same name. This is a world built in the shape of a wedding ring, with a radius of 1 astronomical unit and with a sun positioned at the centre. That is, the ring is the same size as the Earth's orbit around the Sun, so each part of the Ringworld is the same distance from its sun as we are from ours. People live on the inside surface of the ring. The whole thing rotates to simluate gravity. The great thing that you get with Ringworld is lots of room to live: the surface area is the equivalent of a million planets.

The most obvious problem is that the sun shines all the time, and is always directly overhead. Niven's solution was to position a sequence of flat panels in orbit between the ring and the sun, which would block off the sunlight to simulate day and night. He called these plates 'shadow squares'.

After the publication of the book 'Ringworld', it was pointed out that a ringworld exerts no net gravitational pull on the sun at its centre, so there is nothing to keep the sun centred. The ring may wander and eventually the sun will strike the ring, destroying it. Niven's second book about the ringworld ('The Ringworld Engineers') attempted to solve this problem by adding attitude rockets to the ringworld, a somewhat inelegant solution.

The Smoke Ring

The most elaborate of Niven's imaginary worlds is described in his books 'The Integral Trees' and 'The Smoke Ring'. Niven admits he did not design this world himself: it was the brainchild of XXXX. The smoke ring consists of a doughnut-shaped volume of air in orbit around a very small, very massive star - a neutron star. There is a large planet within the smoke ring, also orbiting the neutron star, and the whole shebang orbits around a sun-like star, which to the inhabitants is called 'The Sun'.

That doesn't sound very interesting, but the upshot is that there is a vast volume of air with zero gravity. People float in that air and can live, providing they can get food and drink. The book describes in detail what it is like and the complications. The story is crap, by the way.

Other worlds

Niven wrote a short article about the design of massive worlds. In it, he mentions megaspheres (Dyson spheres), cosmic macaroni and other things.