We live in a truly vast universe with 100 billion galaxies (give or take a few), each of which houses 10-100 billion stars (give or take a few).
IF there are other forms of intelligent life out there, then it seems reasonable that, like us, they will also suffer energy crises. As on Earth, they may consider using solar energy to supply their world’s energy needs.
At some point they may find that building solar panels on their alien roofs supplies woefully little energy in return. If so, then they may think bigger and decide to harness the energy from their entire sun.
How? Perhaps some civilizations will be just powerful enough to disassemble some nearby orbiting moon to use as raw material to build solar energy panels that surround their star. Such a complete solar energy structure is called a “Dyson sphere,” named after physicist Freeman Dyson at the Institute for Advanced Study in Princeton who first came up with this concept.
Were a civilization to choose to build a Dyson sphere, then an observer far away looking at such a star with a telescope (say on Earth), we would not see that star anymore. The star would be covered up by all those panels, and would seemingly ‘disappear.’
Interestingly, it is well known that solar panels also radiate in the mid-infrared. Astronomers could still hope to detect the presence of a Dyson sphere by its mid-infrared heat.
Now imagine an alien civilization that has still bigger energy demands and decides that harnessing all the light from one star is not just not enough for them. Instead, they would encase the entire galaxy with its billions of stars in a gigantic Dyson sphere (or equivalently, encase every one of its stars in Dyson spheres). Again, this civilization would be detectable despite its invisibility in the optical colors by looking for its radiation in the mid-infrared.
Recently astronomers have undertaken a search of 100,000 galaxies for any signatures of such civilizations. They found none. That possibly means that “Star Trek” dramas may not literally be playing out in nearby galaxies as we speak. At the same time, Professor Dyson comments that an all-encompassing Dyson sphere is not the only way for a significantly advanced civilization to signal its presence. Perhaps advanced alien civilizations may not all feel the need to be quite so energy-hungry? What would/will we do?