Story set inside a sphere

Question

This is a story with a civilisation whose "planet" is the inside of a sphere, like an inverted/hollow world (or Dyson sphere but that's not quite the same thing). The physics in the story is made up.

I think they try digging and the conclusion is that they are surrounded by a large or infinite amount of rock/soil.

Their "sun" is at the centre of the sphere, but it is a fire that goes off at night and relights the next day.

I think they have oceans and continents. And there is flight but it works differently in their world.

It was science fiction (rather than fantasy). In particular, why the "sun" goes out and relights, and how the flight works, were explained.

I read it in the 1990s so it wouldn't have been published after that. I think it was a short story or novella. I don't remember what the plot was though.

Answer 1

The Straight Dope has a thread with examples of stories set on just about every shape of planet imaginable, including "the inside of a spherical void within infinite solid matter" (post #39) in Ring of Truth by David Lake.

That description and the very limited reviews of the book on the web (Amazon, Goodreads) seem consistent with what I remember.

However, I don't recognise the title, author or cover pictures at all. So I've ordered a copy and will update this to confirm whether it's the right book.

(The hollow sphere idea is mentioned on page 102 of Science Fact and Science Fiction: An Encyclopedia By Brian Stableford, with other examples, but they seem less likely.)

Edit: I've read it now, and it was the book I was thinking of. It is a 192 page sci-fi novel, not a short story. It has some nice alternative physics that seems consistent and somewhat plausible. The fact that they are in a sphere is a plot spoiler.

The characters are not initially aware of the shape of their world and, although there are clues for the reader to guess, it isn't revealed to the characters until the end. The plot follows a prince with wanderlust who is initially tutored with the current state of knowledge about the world and then goes on a quest to find out more. Gravity works by light being repellent (rather than masses attractive) so, for example, you weigh less indoors and at night. However, they use other means to achieve flight.

Answer 2

This might be the planet Mesklin (en.wikipedia article, contains spoilers) in one of Hal Clement's novels. The planet first appears in Mission of Gravity (1953), then in other novels by Hal Clement.

(This one paragraph is an update.) You can find almost all the details you asked about from the very first chapter of Mission of Gravity, so it is possible that what you remember is based on that.

Mesklin is a world with very high gravity. It is inhabited by the Mesklinites, an intelligent species that looks a bit like worms, and are adapted to the high gravity.

The Mesklinites never go far from the ground, have a fear of objects falling on them, and build only single-level buildings with very light roofs. At least, this is the situation near the poles. The gravity is much lighter near the equator, where gravity is light enough that Mesklinites can actually fly with the aid of gliders.

The inhabitants have science, and believe they live on the inside surface of a bowl (half of an oblate spheroid). That is, until one day, when a spaceship of humans arrives from outside Mesklin. The Mesklinites learn about the outside world for the first time, but what's more disturbing though is what they learn of their own world.

Mesklinites are living on the outside of a flattened sphere, not the inside. I hide the explanation for their false belief below, which is revealed in chapter 15.

Mesklin is actually a super-dense giant planet. The atmosphere of the planet is dense, but concentrated very close to the surface, and gets less dense as you go up. This bends light in such a way that the ground appears to curve upwards. The inside of a sphere was a good enough approximation for all purposes, because they never go far from the surface of the planet.

There are indeed oceans, and the Mesklinites can travel them on ships, though they rarely do so.

I don't remember anything about digging or what they believe about the Sun, but I have only read Mission of Gravity.

The plot of that novel is the following. The spaceship of humans had arrived (a little before the start of the novel). The humans are co-operating with the Mesklinites to recover a human rocket that has crashed on the planet.