In 1960 Freeman Dyson proposed that a sufficiently-motivated civilization might build an ‘artificial biosphere’ around a star in order to fully exploit its radiated energy. This concept has become known as a Dyson sphere.
The idea of enclosing a star seems incredible, but as Dyson later wrote: ‘there is nothing so big nor so crazy that one out of a million technological societies may not feel itself driven to do.’
He proposed a ‘Search for Extraterrestrial Technology’ to look for characteristic signs of such civilizations, and searches have been done – beginning (I think) with Carl Sagan and Russell Walker in 1966.
More astonishing in some ways than the stellar enclosure is the fact that planets must be torn apart to provide the raw materials for construction.
‘One can think of several feasible methods of disassembling a planet’, Dyson wrote in a 1966 paper describing one such technique, using earth as an example. Nikos Prantzos summarizes:
Dyson proposes accelerating the planet’s rotation about its axis until centrifugal forces become greater than its internal cohesive forces. At this point the object will begin to break up, projecting material into space. Breaking point is attained when the planet’s period of rotation drops to about one hour…
In order to accelerate the spin of a planet, Dyson suggests wrapping it around with an enormous metal grid into which a powerful electric current is injected. This creates an electromagnetic force which, applied in the right direction, would cause a slight acceleration in the planet’s rotation. Slowly but surely the centrifugal force would increase, particularly at the equator. When the rotation period reached breaking point, the first fragments would begin to fly off the equatorial zones of the planet. As the enormous spinning top turned faster, more and more chunks would fly off into space to be captured by a gigantic system of magnetic nets.
In Dyson’s 1966 paper, using our world as an example, he calculates that the earth’s rotation could be doubled or halted in a mere 2,500 years, and that it would take 40,000 years for the planet to begin spinning apart.
From a search for extraterrestrial technology point of view, what aspects of the planeticide process might be remotely detectable?
Off the top of my head, signatures of the disassembling process could include unusual planetary magnetospheres, rotation rates and/or oblateness, and vast quantities of spun-off matter sharing a planet’s orbit … Dyson (1966) envisions a massive array of solar energy collectors large enough to capture 300 x the solar power intercepted by the earth.
I’m not an expert in how much we can tell about exoplanets at the moment, but I think most of these are feasible or may become so. Detecting the array of solar collectors is similar to Luc Arnold’s ideas about detecting transiting astroengineering structures.
Arnold, L. 2005, ‘Transit Lightcurve Signatures of Artificial Objects’, Astrophysical Journal, 627, pp. 534-539.
Dyson, F. J. 1960, ‘Search for Artificial Stellar Sources of Infrared Radiation’, Science, vol. 131, pp. 1667-8.
— 1966, ‘The Search for Extraterrestrial Technology’, in Perspectives in Modern Physics (Essays in Honor of Hans Bethe), R. E. Marshak (Editor), John Wiley & Sons, New York.
Prantzos, N. 2000, Our Cosmic Future, Cambridge University Press, Cambridge.
Sagan, C. & Walker, R. 1966, ‘The Infrared Detectability of Dyson Civilizations’, Astrophysical Journal, vol. 144, no. 3, p. 1216.