Possibly habitable exo-planet found- Gliese 581g

[GrandMasterTerwynn]

If they've been swamping the galaxy with high power radio signals for millions of years (a big assumption, but not so unreasonable, they certainly aren't going to use gravity waves or 'psionics') then SETI should be due to find their signals...any time now. There's only so much spectrum to search, especially if the ETI are using the relatively quiet 'hydrogen line'

Or if they're into building dyson spheres, we should be able to detect those on infrared. (unless they are hyper-efficient, using multiple layers operating at ever lower temperatures and using the waste heat of the previous layer for power w/ 'sufficiently advanced technology' then maybe that cloud of 'dark matter' around the milky way is actually all dyson spheres...no idea if this is actually remotely plausible.)

What you're describing is a a Dyson shell, which is a sci-fantasy brainbug based on a complete misinterpretation of Dyson's original concept. Dyson's "sphere" is really more of a swarm of habitats and power-collecting satellites or statites. Spotting a Dyson swarm ought to be easy. Simply look for a star that's surrounded by a uniform shell of warm metallic "dust" which is too old to be naturally surrounded by a uniform shell of warm metallic dust.

But back on the subject of Fermi paradox, the basic point is that while, based on the age of the galaxy, the likelihood of us being first is very, very small, it seems *less improbable* than the case that, every time Natural Selection produces a mind, no matter when or where in the universe it happens, no matter what the selection pressure in the environment is, it produces essentially the same antisocial, short-sighted, superstitious mind; over, and over, and over.

Natural selection would tend to produce a being whose principle foci are immediate survival and reproductive success. Since you can only cram so much into a given volume of brain tissue, the mind that would tend to emerge is
A) Anti-social outside its immediate kin and social group: Outside social/kin groups are competitors for resources that might go to one's own survival and genetic supremacy. Even the most sophisticated eusocial life-forms work in complete harmony to wipe out the competition.
B) Superstitious: Because having a threat-awareness system that reports a lot of false-positives will result in a being that stays alive longer than one whose threat-awareness system is so good at rejecting false-positives it kicks out some actual positives as well. In this case, throwing out an actual positive will tend to result in the positive attempting to eat you. If it succeeds, then you've just won a Darwin Award. If it fails, you'll be a lot more careful next time.
C) Short-sighted: Because having the ability to internalize detailed future plans lasting longer than a fraction of the local year doesn't really buy you anything. Circumstances beyond your control will guarantee that all the fine-grained details will be different from what you were expecting. They will also make it uncertain whether or not you will actually be alive to carry out your future plans. Ergo, it pays to be short-sighted.

You're assuming that a civilization would even want to build a Dyson Swarm, spam interstellar probes, or go beyond a handful of star systems at best. Why?

Because a sufficiently advanced civilization will realize that staying on the home planet until the home star leaves main sequence is just asking for trouble. Once you have one colony, population growth will eventually dictate that two would be better. And then four, and so on. Unless they manage to engineer out that pesky "expand and grow" imperative from their instincts. In which case, they might be happy to mass-upload themselves in the most environmentally-sensitive fashion possible . . . but, it only takes one successful expansionist species to paper the galaxy in their habitats.

"Species survival" is the usual answer, but it's all speculative on how an alien civilization might evaluate such things. With regards to the one space-faring civilization that we know of, "long-term species survival" is an anemic driving force.

We could invoke the Dead Hand/Tentacle/Mouth of the Market. Assuming the Dead Hand of the Market didn't kill them all the first time, eventually a species' demands for energy and resources to drive economic output will push them to want to build swarms of statites.

Until 12,000 years ago, their social organization was virtually unchanged for hundreds of thousands to millions of years. Their technological advancement was very, very slow over the same period. It's not at all unlikely that other intelligent alien species may end up in a similar situation, except that they don't break out of it towards increasingly advanced technological civilization.

Their average brain size was growing during that time. The typical Erectus alive ~100,000 years ago had a bigger brain and better tools than the ones alive ~1,000,000 years ago. Some of the last populations of Neanderthal appeared to have developed a sophisticated culture of tools entirely independent of those who'd been acculturated to Sapiens. Our brains have continued to accumulate genetic changes since that time.

We went from "bipedal ape" (evidence suggests that the common ancestor to humans and currently-extant great apes was a biped) to "force of nature" in a mere seven million years. A mere 65 million since a wayward asteroid wiped out every dinosaur that wasn't small, feathery, and flew well. Compared to timespans of a couple of billion years, that is nothing.

Look at the length of the Mesozoic and Paleozoic Eras, though. That's a considerable amount of time for a species to develop sentience and even technological civilization that might survive a mass extinction, yet so far as we can tell, it did not occur.

The average brain size of dinosaurs slowly increased with time, though. And dinosaurs of the Mesozoic and Paleozoic eras were very small-brained. The best of them, Troodon, was about as brainy as an ostrich. The best dinosaurs (pronounced "birds") of the Cenozoic are just as brainy as the great apes, albeit a bit on the small side. Quite conceivably, without the K-T event wiping them all out, dinosaur species would've evolved with increasingly large and complex brains (just as they have now.) They might've done so faster and gotten further (since there's only so much you can pack into the head of a raven or a parrot, compared to a troodontid.) They were just starting to overlap with modern birds by the end of the Cretaceous. It is not inconceivable that this trend would've continued.

[Lord of the Abyss]

One interesting speculation I've heard for why we don't see evidence of other intelligent life is that Earth may be unusual for life bearing planets in not being a water world. Add a bit more water and you have little to no land, and even if intelligence arises it will likely never develop technology. Earth is "Just Right" when it comes to water; enough so that we aren't a dead or near-dead desert planet, but little enough that we have land to live and build on.

[Guardsman Bass]

Because a sufficiently advanced civilization will realize that staying on the home planet until the home star leaves main sequence is just asking for trouble.

Hence why I specified neighboring star systems. A civilization settling in its home system plus maybe 1-2 neighboring systems is effectively immortal, barring supernova, universe heat death, or more powerful civilizations wiping them out. Why go to the trouble of spreading across the galaxy, particularly if it means your civilization will fragment a millionfold due to light-speed lag?

Once you have one colony, population growth will eventually dictate that two would be better. And then four, and so on. Unless they manage to engineer out that pesky "expand and grow" imperative from their instincts. In which case, they might be happy to mass-upload themselves in the most environmentally-sensitive fashion possible . . . but, it only takes one successful expansionist species to paper the galaxy in their habitats.

Again, this is speculating on hypothetical alien psychology. But look at humanity - population pressure is actually declining as a driving force. Barring societal collapse or immortality drug in the next century, humanity's population is going to level off, then decline. We've seen birth rates decline and level off in the Developed World, and it is happening in the Developing World as well.

Which is not to say that aliens will be like that, just that we shouldn't count on population pressure to push a civilization into interstellar space. Particularly if it's an Uploaded Species, who can presumably engineer themselves and reproduce simply to meet their needs at will.

It's one of the reasons why I'm pessimistic that we'll see significant human off-world colonies any time in the next couple of centuries, outside of (maybe) Low Earth Orbit. The prime factor for colonization throughout human history - population pressure - is falling off, the economic incentives are dismal, and there's no political will to divert the money to support such long-term projects.

[Zaune]

One interesting speculation I've heard for why we don't see evidence of other intelligent life is that Earth may be unusual for life bearing planets in not being a water world. Add a bit more water and you have little to no land, and even if intelligence arises it will likely never develop technology. Earth is "Just Right" when it comes to water; enough so that we aren't a dead or near-dead desert planet, but little enough that we have land to live and build on.

That's a fairly wide Goldilocks zone given that we had fairly advanced cultures come into being independently on both sides of the Atlantic, especially since the limiting factor isn't so much the percentage of land total as the percentage of land that's suitable for habitation and eventually agriculture.

[Flameblade]

One interesting speculation I've heard for why we don't see evidence of other intelligent life is that Earth may be unusual for life bearing planets in not being a water world. Add a bit more water and you have little to no land, and even if intelligence arises it will likely never develop technology. Earth is "Just Right" when it comes to water; enough so that we aren't a dead or near-dead desert planet, but little enough that we have land to live and build on.

That's a fairly wide Goldilocks zone given that we had fairly advanced cultures come into being independently on both sides of the Atlantic, especially since the limiting factor isn't so much the percentage of land total as the percentage of land that's suitable for habitation and eventually agriculture.

I believe that he meant that most other Earth-like worlds would be totally covered in oceans, with no dry land available. Either that or be a little too hot or have too weak of surface gravity to retain enough water over billion year timespans. It's entirely possible that without the impact that created Luna, the Earth would have had planet-covering oceans.