Civilizations in our Universe

You said,

"None of that is a requirement for life or 'civilization'. One could as easily argue that life managed to evolve despite these instabilities, and it is stability after all that tends to favor life, especially advanced life."

This is speculation, take away the moon, it's gravitational effects, tides and tilt and we could have had a very different planet not necessarily favouring our evolution.

"We barely made it here on Earth"

No Idea what you mean by this or "we."

Homo sapiens? Seven billion individuals is hardly "barely making it."

" evolving civilization only near the end of our window. "
What window? We have been around for about 100,000 years or so that is no time at all geologically speaking.

"Took 5 billion years to get here from the earliest life, and yet in another billion it seems conditions here will not support multicellular life at all. That's cutting things pretty close."

Yes and no. Life evolved on earth after about a billion years, after the formation of the earth at least once, a few billion years of single cells then multicellular about 400 million years ago.
The timing from there to vertebrates, mammals to primates and us seems long winded. Perhaps we would not be here at if it was not for the KT?

"We are at the 'here and now' point. Put this picture (a nice poster size one) on a wall. Throw a dart at it. That's the alien civilization. If the dart doesn't land exactly on the red line, we cannot see it. Only an enduring civilization would have a significantly extended worldline long enough to possibly cross the red line, and it appears that such enduring civilizations (certainly not our own) are exceedingly improbable. That's a good reason we don't see them. The dart throws are simply not on that red line, and we only see stuff that is."

Another illustration is the spherical area covered by our current (and past) technology in terms of EM waves transmitted. A tiny area of our own galaxy which itself is 100,000 light years across.
Our EM waves have reached 100 light years out?
We can "see" distant stars and galaxies of course but only as they were in the past.
That was the point of my UAP posts, what are the chances both civilizations evolve, survive together and are close enough.

 

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Yes, and that is a big 'if'.

This is one of the solutions to the FP. But it's based on a assumption for which we have zero evidence.

 

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It's not like humans are inevitable given the initial conditions on Earth. Do you mean not necessarily favouring the evolution of any 'inteligent civilization'? That's just as much speculation as my comment. Yes, this is all speculation, as is any discussion of the Fermi paradox.

Yes, there are seasons and tides, and predictably, life that has evolved on Earth often leverages one or both. The same abiogenesis would have evolved differently in the absence of seasons and tides. I see no reason why something akin to human civilization would be more or less likely in such an environment since what forced our eventual selection for intelligence had little to do with seasons and tides. Granted, women do have menstrual cycles that are in sync with moon phases, so there is that.

Instability tends to set things back. Calamities happen, resulting in mass extinctions. Each of these extinctions cost time, but also helps. There's one going on right now, with an expected 85% loss of all species (possibly including us). Does it help clear the way for what's next? Maybe, but time is running out for that. Only so many calamities allowed.

I mean we, the human race, came about very near the end of the gilded period (the window) for complex life on Earth. About 85% of the time had been used up already, after which Earth will not really support multicellular life anymore. Back to simplicity then. Earth life will go on for 3-4 billion years after that, but will eventually blink out entirely.

I read that multicellular forms appeared some 1.5 BY ago, but the Cambrian explosion took place more or less at the time frame you indicate.

What is a KT?

Close enough in time is what I was trying to get across. Sure, there might be a civilization on some star 20 LY away, but we can't see it unless it's here at the same time as us, and that's an incredibly narrow window to hit.

 

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There are very compelling physical and chemical reasons to suspect that boundary areas such as tide pools nurtured life and vastly accelerated evolution.

While it's conceivable that complex life might crop up in the open ocean or the open plains, the tribulations of such an existence will greatly reduce the chances of it flourishing.

Complex life needs access to a lot of chemicals that won't be found in any concentration in the open ocean or on the plains. And it needs protection from the elements so it can husband these resources. This is very simplistic, but there's a lot to it.

KT boundary. Essentially, the geologic evidence of the catastrophic extincton event of the dinosaur age and the resultant rise of mammals.

There's some pretty compelling argements that intelligent life would not have arisen without the extinction the dinosaurs. They ruled for 200 million years and squandered it on big teeth and dummy thicc thighs.

 

Some birds - which are dinosaurs - are highly intelligent and can manipulate tools.

 

True. Although, arguably they too owe their existence due to the KT event

 

Don't recall where I read it but it was suggested our solar system viewed from afar would appear brighter than expected in microwave bands that have very low natural levels. Not a signal but a signature.

 

Do you have a source for that?

 

No, which is why I said I don't recall where I read it. I am not even claim it is true. More like I am mentioning the idea (whilst mentioning I got it from somewhere) that a technological civilisation produces a lot of radio, microwave or other emissions, that aren't intentional signals, yet might be detectable by intensity.

 

Natural phenomena give off radiation and particles including us (IR) so it is a matter of sifting through the noise to find those signals.
The goal of SETI

 

Technosignatures.

https://www.scientificamerican.com/article/the-origin-of-technosignatures/

Having read that, I wonder if we could teach them how not to pollute a planet??

SETI

https://www.seti.org/event/technosignatures-vs-biosignatures-which-will-succeed-first