I think Freeman Dyson was dead wrong. Why would we search for infrared-heavy emissions from so-called advanced societies in other systems if the theory behind the whole idea is bogus?
Structurally, Dyson Spheres just doesn’t make sense — it would take a high-density material to construct something that would need to be constantly stabilized, using more matter than exists in our solar system, for purposes that don’t make sense. And the fact that it’s assumed to be 1 AU from the Sun is strange — Earth has a tall atmosphere that blocks varying forms of radiation — so you’d probably want the energy-gathering elements closer and the habitations farther — completely wrecking any sphere-ish shapes.
Besides… getting back to energy here for a minute. Just think of what you’d be doing in creating a Dyson Sphere — using enormous amounts of energy to move and shape matter — into a structure designed to collect energy so that people can use it. On a small scale, this works, but we’re talking about an effort larger than any civilization would want to undertake.
The two assumptions that are required in order to start thinking about a Dyson Sphere:
- Overpopulation of a home planet or abandonment of that world for a space-based living area, extrapolated over a much longer period of time to the point where necessity dictates full encapsulization of a star for energy-gathering purposes
- A need for a lot more per capita energy than we can currently fathom
It would be foolhardy mostly from a return-on-investment perspective — I guess a civilization advanced enough to collect all the matter from a system and build a huge structure may have the ability to keep a star up and running reliably, but the progression of technology doesn’t logically dictate such a thing.
Doesn’t it make more sense that humans with sufficient technology to build even the most rudimentary Dyson structure would probably find solutions to travel between star systems (after all, many systems closest to Sol are also second-generation stars, meaning that there is likely cooled dense material near the stars, even if not in planetary form), master the use of atomic power (such as, for example, controlling nuclear fusion), and find an equilibrium of survivability on their home planet based on resources?
I think we were taught in middle school about an island with bunnies, or how viruses and bacteria could easily take over the world, if not for the scarcity of resources. You can argue that technological change is constantly changing what the definition of human overpopulation on planet Earth is, but I’d think that with the rate of technological progress that interstellar travel would be feasible well before we reach that point. Besides, even if that’s not the case, humans and the earth will have to reach an equilibrium eventually.
So even if you take the simpler Dyson structures, which would relatively be more likely — what would the true differential be between a system with or without those structures in terms of infrared radiation? If he was not arguing for an all-encompassing shell, then why search for infrared as a sign of life in the first place?
It would be a big let-down if SETI found something — because we’d only be hearing or seeing a society many light-years away. It may not be “We are not alone” when that day comes, but rather “We were not alone.”