Big Dumb Object

In discussion of science fiction, a Big Dumb Object (BDO) is any mysterious object (usually of extraterrestrial or unknown origin and immense power) in a story which generates an intense sense of wonder just by being there; to a certain extent, the term deliberately deflates this. Probably coined by reviewer Roz Kaveney, the term was not in general use until Peter Nicholls included it in The Encyclopedia of Science Fiction as a joke.

Big Dumb Objects often exhibit extreme or unusual properties, or a total absence of expected properties:

• The object discovered in Quatermass and the Pit was made of a material of extreme hardness, such that diamond-tipped drills and acetylene torches would not damage it. At the same time nothing would adhere to it.
• In the movie based on Michael Crichton's novel Sphere, the eponymous object would reflect everything in its presence except people. If it did reflect someone, they were alone, and the individual was accepted as worthy to harness the device's power.
• In Iain M. Banks' novel Against a Dark Background, the Lazy Guns have a lot of mass and yet little weight, and weigh three times as much upside-down as upright.

Such unexpected properties are usually used to rule out conventional origins for the BDO and increase the sense of mystery, and even fear, for the characters interacting with it.

J.G. Ballard's short story, "Report on an Unidentified Space Station" (1982) may be regarded as an exploration of the metaphor of the BDO: in each successive report, the artifact's estimated size increases, people become lost within it.