Astroholic Vlog: Dyson Spheres
Channel: Alfredo Carpineti
Date: 2014-09-05

In this Astroholic Vlog I will be talking about Dyson Spheres. Dyson Spheres are hypothetical megastructures purposely built around stars to absorb most or all of the stellar electromagnetic output.

The idea comes from science fiction, but it was formalised by Freeman Dyson in the 60s as a thought experiment with the energy needs of an advanced civilisation in mind. 50 years later we are not much closer to building a full Dyson Sphere, but we understand better how should it be built, and what the consequences of embarking in this endeavour would be.

A solid Dyson sphere won't work for several reasons. The first reason is physical. A shell around a star would not interact gravitationally with it, and it would lead to the eventual collision with the star. The second reason is structural. The internal strain that the material receives in such a structure would be so great, we don't have anything that even compares. Thirdly there's not enough material in the solar system to build it.

A more feasible way to harness as much energy as possible from a star is the so called Dyson Swarm. This is a series of satellites orbiting a star collecting as much light as possible. They need to be suspended, so we will need those special solar sails I've discussed in a previous blog post. A viable Dyson swarm prototype is still years away but this is the most feasible type that we can achieve in the foreseeable future.

So, what's the astronomical importance of Dyson Spheres? If there are civilisations out there that need that kind of energy, they must undergo a planetary scale mining operation across their stellar system and that is something we would be able to see with our telescopes.

But how much energy would we get out of our Sun? In the last century, Energy consumption has been increasing but in the last few decades the increase comes mostly from developing countries, and I think this suggest we could reach a plateau in the next century. Now, the total yearly output of the sun is 33 trillion times the energy humanity consumed in 1998.

Dyson Spheres are fascinating both as scientific hypothesis and as sci-fi scenarios, but I think it's very unlikely that we will ever need one.

REFERENCES

Freeman John Dyson, Science, Vol. 131, June 3, 1960, pp. 1667-1668.

Sun Fact Sheet http://nssdc.gsfc.nasa.gov/planetary/factsheet/sunfact.html

David MacKay, Without the Hot Air. 2009

The Energy data comes from the World Bank: http://data.worldbank.org/