Our perception of the implications of a "Dyson Sphere" seems fundamentally flawed in my opinion. The idea is that a growing civilization will
eventually achieve total power requirements comparable to the output of the local star. If so, then surely such a civilization would not construct a
Dyson Sphere. One doesn't simply, for instance, double power requirements over night for an entire established planet. So then the consideration for
the necessity of undertaking the project of a Dyson Sphere would sooner be brought on by a 0.1% global energy deficit, which is in itself critical. If
the technology, resources and anticipated eventual need for a Dyson Sphere exists, then some idealists may imagine it's value, only to at best lose
out to apparent short-term impracticability and society's imprudence, or sociology. In other words, the energy infrastructure already exists for this
theoretical society and though their power requirements approach the output of the local star, we can't anticipate that they'd scrap their existing
energy production and replace that infrastructure with an eventual Dyson Sphere.
I can't imagine a reason for a civilization to construct such a device, unless they were doing so in a star system which isn't already established, in
preparation for introducing an immediately extensive colony, like how the Chinese build entire metropolises for later inhabitation. However, this
would imply a "Type 3 Civilization," not the "Type 2" others have suggested. The only alternatives I can conceive seem less likely. For instance, an
envisioned scientific endeavor of great prominence in their culture, with tremendous and unprecedented power requirements, could potentially inspire a
project as this.
I imagine the concept of a Dyson Sphere could also be adapted to allow for a military purpose, such as harnessing the stars output to power a massive
directed energy weapon and/or for propulsion. This would imply either a "planet buster" heavy weapons platform, if not a "galaxy buster" as observed
from 3C321, or a literal "Death Star." The concept of a Dyson Sphere could also be updated to allow for a star to be utilized as an Active-SETI or
other beacon, perhaps not unlike the myriad pulsars we've discovered, especially those that don't appear to operate at a pattern, or which operate at
patterns that don't seem to make sense if they're naturally occurring. Lastly, a a more mundane motivation may exist, such as deep space telemetry.
They may want to scan as much of the surrounding universe as possible, or it might have a less general purpose, such as scanning for incoming threats
from very deep space, be they hostile craft, asteroids, GRBs, or other inbound destructive forces.
Whatever the case, ET doesn't seem likely to construct a Dyson Sphere to offset a civil energy deficit. In fact, I wouldn't expect them to construct a
Dyson Sphere at all. By the time they achieve the need, technology and resources for such a project, I'd anticipate that they'd have arrived at a more
practical solution to their power needs. That may not always be the case though. A seemingly infinite universe seems to imply that everything should
happen, at least once. Still, it seems unlikely that a Dyson Sphere should be common, and if not, it seems unlikely that we should detect one, and if
so, it seems unlikely that we observe a Dyson Sphere.
Not to mention the resources necessary just to maintain such a large and massive object. Conventionally, it should attract catastrophic damage on a
constant basis, as that's the nature of massive objects in space. They're magnets for everything destructive. I'd highly suggest leveling the moons
topography then practicing keeping the surface of our moon smooth before taking the leap to Dyson Sphere. Or have we forgotten the ESA
edit on 10-2-2016 by Navarro because: (no reason given)