m. c. de marco: To invent new life and new civilizations...

BDO of the Day: Dyson Shell

Today’s Big Dumb Object (BDO) is a Dyson shell, otherwise known as a Type II Dyson sphere. (A Type I Dyson sphere is big and dumb, but not an object: it’s a swarm of smaller objects in separate orbits, enough to use and block all the light of a sun.) A Dyson shell is impossible to make with any technology we know of; the gravitational stresses on it are too great for any known materials to withstand. In addition, a Dyson shell has no gravity to hold land, atmosphere, or inhabitants to its inside (see the shell theorem for proof), and negligible gravity on its outside. (These issues are usually solved using technology that’s indistinguishable from magic.)

"SHield World Construction" by Adam Burn, used with permission image by Adam Burn

The usual size of a fictional Dyson shell is 1AU in radius, giving it a surface area of a hundred quadrillion square miles—the equivalent of 550 million Earths. That’s big. Very, very big. So big that if you were inside it, it would not look curvy (as it is so often illustrated) but absolutely flat. You would not see the continents above you (as it is so often described) because the ones overhead would be astronomically far away, and there would be immense quantities of atmosphere between you and any “nearby” land. Peeking in through a hole or airlock (as is so often done) would require the same instrumentation as looking a quarter of the way around a solar system does.

One begins to see why Dyson regretted naming the lot of them, wishing instead that Olaf Stapledon would get the credit he deserved. (They first appeared in 1937 in Stapledon’s novel Star Maker.) Nevertheless, the impossible shells are quite popular with fiction writers, and even made it into a particularly execrable episode of Star Trek: The Next Generation. Dyson spheres loom over the Orbitsville series, the Cageworld series, and the two Farthest Star books, and are seen in passing in many other works, such as Across a Billion Years.

Note: The BDO series will be appearing less frequently from now on, although I still expect to post several times a week and not to run out of notable BDOs before NaNoWriMo at the earliest.