Civilizations in our Universe

Halc 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. We barely made it here on Earth, evolving civilization only near the end of our window. 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.

Size matters little if at all. Water (and carbon) is wonderful for our kind of life, hence the need for a 'habitable zone', but that seems common enough that there is at least one other planet with liquid water on it just in our solar system. Avoiding asteroids is part of the stability thing.


Here I have my doubts, since the center of a galaxy, especially early on, tends towards very unstable conditions. Sure, life might take hold on some planet in a habitable zone, but with so many rocks to wipe things out, and so many large objects (passing stars and such) to disrupt stable orbits, planets simply are not likely to stay habitable for any length of time. It's way out here in the boondocks that stability is to be found, and more likely with a smaller star with a far longer lifetime than that of our sun.


Let's suppose that we would notice, that we could detect a civilization by looking for radiation that would not otherwise be emitted, so we could say see them even in Andromeda if they were there. What are the odds that a civilization would be thus detected?
Nobody has mentioned the 'great filter', which is a frequent solution to the Fermi paradox. It says that a civilization like ours is fleeting, and pretty much ends when the non-renewable resources run out, or until we wipe each other out. Either way it happens in an amazingly short time, so not only do we have to look in the right direction to see them, but we have to look at exactly the right time, and the odds of doing that are pretty much nil.

Here's a picture of the universe:
t16_three_distances_4.gif

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.
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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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Pinball1970 said:
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.
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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.

Pinball1970 said:
"We barely made it here on Earth"
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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.

Pinball1970 said:
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.
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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.

Perhaps we would not be here at if it was not for the KT?
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What is a KT?

Pinball1970 said:
what are the chances both civilizations evolve, survive together and are close enough.
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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.
 
Halc said:
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.
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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.

Halc said:
What is a KT?
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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.
 
DaveC426913 said:
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.
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Some birds - which are dinosaurs - are highly intelligent and can manipulate tools.
 
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.
 
Pinball1970 said:
Do you have a source for that?
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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.
 
Ken Fabian said:
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.
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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.
Today the search for intention is represented by a still-coalescing field of cosmic “technosignatures,” which encompasses the search for structured electromagnetic signals as well as a wide variety of other evidence of intentional manipulation of matter and energy—from alien megastructures to industrial pollution, or nighttime lighting systems on distant worlds.
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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
Which approach will discover the first evidence of extraterrestrial life? Will technosignatures or biosignatures confirm our hypothesis that life exists outside our watery, shimmering planet and that, indeed, we are not alone?
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https://www.seti.org/event/technosignatures-vs-biosignatures-which-will-succeed-first
 
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