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

BDO of the Day: Orbitsville

Today’s Big Dumb Object (BDO) is Orbitsville, the Dyson sphere appearing in the eponymous novel by Bob Shaw and its sequels. I gave a brief review of the first two in a recent post.

Orbitsville is a traditional Type II Dyson sphere of the sort that made Dyson regret his association with them: made of a thin shell (“only a few centimeters thick”, later upped to 8cm) of magic material (“ylem”), magically radiating no heat or other energy from its central sun, with an environment magically clinging to the inside of the shell in violation of the shell theorem.

Orbitsville is the name used by its discoverers, but it is officially called Lindstromland, then later Optima Thule, by the wider human society. Human explorers first detected Orbitsville because it does have the expected amount of gravity for a Dyson shell enclosing a sun. Its reported diameter is “some 320,000,000 kilometers”, giving it a radius of “just over” 1 AU. Its outer surface is described as perfectly smooth (yet with “a reasonable index of friction”), perfectly spherical, and impervious to all forces possessed by humanity, which got there with a faster-than-light drive based on some invented post-Einsteinian physics.

The sphere rotates at 70,000 kilometers an hour at the equator, which is not the tangential acceleration required to produce gravity (4 million kph); at some point the humans note that the gravity is, instead, “synthetic”. The sphere blocks all radio signals with a (magical) dampening field, as well as the humans' interstellar drive (apparently not by magic but only for lack of the interstellar dust it uses for fuel). The explorers prove able to travel inside the sphere by more primitive means such as airplanes and the like.

The inside surface is “625,000,000 times the total surface of Earth”, which the characters estimate is about “equivalent to five billion Earths” worth of usable land (since most of the area of the Earth isn’t useful, whereas most of Orbitsville is). A rotating shade structure around the sun—a “globular filigree of force fields”, which even the author put in scare quotes—produces both seasons and alternating bands of day and night.

The sphere has a single circular opening at the equator, plus more blocked openings discovered and reopened later in the story. The first opening is about a kilometer in diameter and is protected by a (magic) force field through which a person (or a ship) can pass.

The sphere appears to be a classic abandoned BDO, with several species unrelated to the builders having come across it over time and settled within. More details about the builders and the apparent abandonment are revealed in the sequel, but BDO-wise we only get the added detail that there are 207 openings at the equator spaced about five million miles apart, plus a ring of 173 in the northern hemisphere and 168 in the southern hemisphere; all “vary a little in sizing and spacing”.

The first sequel is, frustratingly, mainly set mainly on Earth, but there is some BDO action at the end, and Orbitsville does loom over the human race thematically for the entire series. Earth was overpopulated with a constant stream of emigrants heading to its one colony world when humanity found Orbitsville, which becomes their new destination. Even in the first book, the characters voiced dark suspicions about the ultimate purpose of the BDO and the risk of humanity’s devolving to a primitive agricultural level within it as many races had apparently done before. But such misgivings don’t slow the exodus one bit; by the second book the Earth is nearly abandoned, and the true purpose of the BDO is revealed.

I didn’t find the notion that vast croplands would turn humanity back into subsistence farmers particularly convincing, but that’s not for any want of effort on the author’s part. His theory is at least superior to that of other authors who project our current interests and lifestyles onto a BDO setting infinitely, perpetually, and thoughtlessly.

The third book is harder to find and I haven’t read it yet, but reviews indicate that there isn’t much more there about the BDO qua BDO.

BDO of the Day: The Chindi

Today’s Big Dumb Object (BDO) is the chindi, a mysterious alien ship in Jack McDevitt’s eponymous book. It’s a little small by my own standards, but has occasionally been mentioned as a BDO (e.g., in this review by Russ Allbery).

Chindi was first published in 2002, but I reread it recently and it definitely holds up as a science fiction novel, though perhaps not so much so as a BDO novel. The novel falls around the middle of McDevitt’s Priscilla “Hutch” Hutchins, or Academy, series. (Spoilers follow for Chindi, but not for the rest of the series.)

About half the novel is devoted to investigating smaller stuff than the BDO: a mysterious signal that turns out to be a mysterious spy satellite, that itself turns out to be part of a mysterious network of such satellites, leading a group of human explorers from star system to star system. The systems are inhabited, formerly inhabited, or otherwise interesting, and space is dangerous, leading to plenty of drama before the BDO is revealed.

In one of these star systems they find the ship responsible for producing and sending out the satellites, whose purpose turns out to be spying on primitive alien cultures (alien to the makers of the chindi, so including humanity back when we were primitive). The ship gives itself away by having made its own red spot (well, a white spot) on a gas giant in order to suck fuel out of its atmosphere. It’s an asteroid-looking thing that is 16.6 kilometers long by 5.1 kilometers wide by 0.8 kilometers high, but it has exhaust tubes.

They choose a Navaho word for spirit to refer to it and decide to board it (one of a series of risky decisions the explorers have been making throughout the novel, leading to an ever-diminishing number of explorers, not to mention ships, involved in this expedition). But the exploration is predictably interrupted by the start of the high-speed trip the chindi has been gathering fuel to make, and much of the rest of the novel is devoted to the physics and gymnastics of rescuing (or losing) people in this predicament, rather than to the interior of the chindi per se.

The humans discover a warren of corridors inside the ship; off of each corridor are countless rooms ready to be filled, or already filled, with archaeological exhibits assembled (how, we never discover) by the chindi in its travels. Careful examination is made of a few of these chambers. The ship has artificial gravity; during an adventure involving an antigravity shaft, Hutch estimates that the ship is about 80 decks high in both directions; despite extensive exploration, no estimate is ever given of the number of chambers found on these 160 decks.

A few robots haunt the halls, ignoring the interlopers, but the engine room isn’t mentioned and no living aliens are found inside. The source and ultimate purpose of the chindi is not discovered in the novel, so it retains an air of mystery appropriate to a BDO.

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.

BDO of Talk Like a Pirate Day: Virga

Today is International Talk Like A Pirate Day, so I’ve picked a pirate-themed BDO for the Big Dumb Object of the day: Virrrrrga—I mean, Virga—is a carbon-nanotube sphere 5000 miles in diameter, enclosing 65 billion cubic miles of volume. It’s is a weightless environment filled with a breathable atmosphere circling a real sun at some distance, in which smaller habitats are rotated for gravity and artificial suns provide light and heat. It’s the steampunk setting for Karl Schroeder’s eponymous airship series beginning with Sun of Suns and including Pirate Sun:

The science behind Virga is explained on his website. Schroeder explains why he gave Virga a relatively modest size, though a balloon environment like his with an Earth-like atmosphere could be almost 22,000 miles across (5.5 trillion cubic miles of space), while a lighter atmosphere permits a sphere about 250,000 miles across (8 quadrillion cubic miles). Plenty of rrroom for pirates!

BDO of the Day: Bernal Sphere

A Bernal Sphere is the space habitat cousin of the most famous BDO of all: the Dyson sphere. First proposed by Bernal in 1929 with a 10 mile diameter, it reappeared in smaller form in the 70s as two of O'Neill’s space colony proposals: Island One (1600 foot diameter), and Island Two (a mile in diameter). The total inner surface of such spheres is about 300 square miles (Bernal), a quarter of a square mile (Island One), and 3 square miles (Island Two), respectively.

Bernal sphere exterior (public domain image from NASA)

A Bernal sphere rotates to provide gravity, and as a result only an equatorial band has adequate gravity to be inhabited, with the remainder of the sphere devoted to windows, trees, and other purposes. This reduces the usable area, making it a relatively impractical layout compared to cylinders and other shapes (even though it photographs well).

Bernal sphere interior (public domain image from NASA)

Note that a real Dyson sphere is far too large for the curvature of the sphere to be visible.