A quick science-y (though probablly more science-fictiony) thought:

[capri0mni]

Icon illustrations for this post, 'cause one is not enough:


One of the arguments I've seen against the existence of advanced technological species beyond Earth is:

No use of energy is ever 100% efficient, thanks to this thing called "Entropy." So if there were advanced alien species on other planets, we'd expect to see extra infrared radiation coming from those planets (and if aliens pointed their detectors toward Earth, that's what they'd see). But we haven't found any, so, therefore, there must not be any advanced civilizations out there...

BUT:

What if an alien civilization figured out how to use dark energy to fuel their work? There does appear to be an excess of that...

Just a thought...

Comments

[davidgillon]

That I <3 Science icon is wonderful!

WRT dark energy, I don't think I've ever seen a discussion of how it fits into the standard laws of thermodynamics.

But thinking about that no IR signature=no-one out there, there are other possibilities:

What if they have morphed to a low energy economy, would we see it against the background? (We used to say we'd see the radio signature rather than IR, but then communication went wired and predictions for the radio signature of any advanced society turned out not to be valid)

What if they have a low population density, and ditto?

What if their civilisation was very slow paced, with the equivalent energy expenditure spread out over a longer period.

What about an unevenly developed society, largely agrarian, but with islands of high-tech on a sort of philosopher kings model.

There are several SFnal alien civilizations where technology has developed in a biological rather than mechanical direction, I think those would tend of be lower energy in general.

And so on. The predictions for a specific IR output actually seem to be largely dependent on assuming a civilization arranged in a comparable manner to ours, and that isn't necessarily valid.

[jesse_the_k]

Good what-ifs, and the whole question is intriguing.

My favorite no-IR-signature is they did use it, but so long ago it's long past earth.

Now they communicate telepathically, having grown very capable mind-reading____s, who conveniently live in _____ on the edge of each dwelling place, serving as amplifiers or relays.

[capri0mni]

There are several SFnal alien civilizations where technology has developed in a biological rather than mechanical direction, I think those would tend of be lower energy in general.

One word: Plants. After all, it turns that trees in a forest have remarkably sophisticated and subtle means of communication and resource sharing. And their repertoire of chemical signals is on the level of our repertoire of words.

In a few of my daydreams, advanced aliens have been communicating with Earthlings for centuries. But to the trees, and they assume we humans are too simplistic to be interesting.

Also, if the advanced tech is biologically based, I don't think the tech signature would be visible beyond: "Yup. This planet has life on it."