I believe that spacefaring life is relatively rare in our neighbourhood to the point where it's entirely possible we're the only one.
As for signs of alien civilization being everywhere, here I have to respectfully disagree. I'll summarize why.
I firmly believe the likely future of humanity is not on planets but in orbitals. Planets are a great way of storing mass. They're a poor way of creating living area. I think the estimate is that 1% of the mass of Mercury could fully encompass the Sun in a Dyson Swarm of orbitals with no material stronger than stainless steel. I believe humanity will be capable of this within 1,000 years and that's super-conservative.
Objects in space that absorb Solar radiation heat up. The only way of releasing that is by radiating it away. That radiation is of a wavelength solely determined by the temperature of the object. For any reasonable temperatures, that's in the infrared spectrum.
So a Dyson Swarm will have a very particular spectrum. They'll be IR lanterns. Sure one star we may not see out of a whole galaxy but the barrier between doing this to one star to the whole galaxy is only a matter of a relatively short amount of time (cosmologically speaking). One million years for the Milky Way (out of 10B+ years).
There are a bunch of assumptions in this and each would be their own topic. But as a solution to the Fermi Paradox, it only takes one.
Recycling waste heat is a common objection but that just reduces your emissions, it doesn't eliminate them. If it did, that would break thermodynamics.
This argument is strengthened by this article: over time more mass is becoming unreachable. For truly long-lived civilizations it makes the most sense to grab as much mass as you can and sequester it. Again, it only takes one.
>> The signs of alien civilizations are everywhere, but humans cannot perceive or understand it
> As for signs of alien civilization being everywhere, here I have to respectfully disagree.
This is all speculation, of course, but that's all we have. This particular answer to the Fermi Paradox goes like this:
Human reasoning and interests are entirely circumscribed by our perception. We are capable only of dimly imagining that other kinds of perception and reasoning exist, but not imagining what or how that might be. Our fictional aliens are (necessarily) only ourselves in disguise.
If other strategies or sentient processes are possible, we will be unable to recognize them as such*. It's not necessarily that alien civilizations are "smarter" or more "advanced", but so different that we wouldn't even recognize them as sentient.
We humans will no doubt, assuming our current state of knowledge endures, create Dyson swarms all over the local cluster, but that is a strategic inevitability given the best of our current understanding; an understanding that, again, is circumscribed by our bodies and minds and perceptions, which in turn are the result of specific evolutionary pressures. There is no reason to expect that these specific pressures uniquely equip us to grasp the entirety of this vastly complicated cosmology in which we find ourselves.
"Assuming our current state of knowledge endures" is doing a lot of heavy lifting, though. How likely is it that 1,000 or 10,000 years of research and increasingly sophisticated understanding of ourselves and our Universe would lead to Dyson as being our best option? Personally, I think unlikely, but who knows?
There are too many mysteries and unknowns for us humans to be too certain about anything cosmological or metaphysical. Way, way too many unknown unknowns.
* Unless aliens are close enough "like us" to be recognizable, but this is exactly my argument: this answer to the Fermi Paradox is that our perception and reasoning ability gives us such a thin slice of understanding the Universe that we have less chance of grasping "alien civilization" than grasshoppers have of understanding how bats "hop". Our dominance of Earth gives us a kind of provincial self-confidence that we understand everything important, but really, that is unlikely.
Let's assume as true (because we're speculating) that we are not among the first, and that some beasts already have situated themselves in the best possible position to take advantage of the future. Why, then, cannot we perceive them?
Materials absorb some quantity of IR radiation. This will heat them up. What you're talking about is essentially a variation of recycling heat. It's imperfect so there'll be some IR signature.
As for signs of alien civilization being everywhere, here I have to respectfully disagree. I'll summarize why.
I firmly believe the likely future of humanity is not on planets but in orbitals. Planets are a great way of storing mass. They're a poor way of creating living area. I think the estimate is that 1% of the mass of Mercury could fully encompass the Sun in a Dyson Swarm of orbitals with no material stronger than stainless steel. I believe humanity will be capable of this within 1,000 years and that's super-conservative.
Objects in space that absorb Solar radiation heat up. The only way of releasing that is by radiating it away. That radiation is of a wavelength solely determined by the temperature of the object. For any reasonable temperatures, that's in the infrared spectrum.
So a Dyson Swarm will have a very particular spectrum. They'll be IR lanterns. Sure one star we may not see out of a whole galaxy but the barrier between doing this to one star to the whole galaxy is only a matter of a relatively short amount of time (cosmologically speaking). One million years for the Milky Way (out of 10B+ years).
There are a bunch of assumptions in this and each would be their own topic. But as a solution to the Fermi Paradox, it only takes one.
Recycling waste heat is a common objection but that just reduces your emissions, it doesn't eliminate them. If it did, that would break thermodynamics.
This argument is strengthened by this article: over time more mass is becoming unreachable. For truly long-lived civilizations it makes the most sense to grab as much mass as you can and sequester it. Again, it only takes one.