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From: Martin Brown <'''newspam'''@nonad.co.uk>
Newsgroups: sci.electronics.design
Subject: Re: Expedition to Europa
Date: Mon, 1 Jul 2024 15:54:28 +0100
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On 29/06/2024 12:04, Don Y wrote:
> On 6/28/2024 10:08 PM, bitrex wrote:
>> On 6/27/2024 5:17 PM, Don Y wrote:
>>
>>>> Most big librarys carry AW.
>>>>
>>>> .<https://europa.nasa.gov/mission/about/>
>>>>
>>>> If it turns out that there is life in the ocean of Europa, which has
>>>> existed for something like four billion years, it supports the general
>>>> idea of "random but inevitable" theories of Abiogenesis.
>>>
>>> _Remembrance of Earth's Past_ has an interesting take on the whole
>>> notion behind an "empty" universe.  It's a tedious read (mainly for
>>> me coming from a non-chinese culture... just keeping track of the
>>> characters is difficult) but has some good ideas to chew on at its core.
>>
>> My guess: The Universe is mammoth, the technological and energy 
>> requirements of even short-distance interstellar travel are immense, 
>> the lifespan of technological civilizations is highly time-limited 
>> before such a civilization destroys itself, technological 
>> civilizations are very rare to begin with, and no technological 
>> civilization ever survives long enough to attempt it.
> 
> That wouldn't explain why there are no *signs* of intelligent life.
> 
> *We* can't (yet) travel interstellar distances in single lifetimes
> but I'm sure anyone with technology comparable to ours would be able to
> *detect* our presence (given that we seem to make no attempt at "hiding")

The Fermi paradox of why aren't they here yet is somewhat tricky to 
explain. Our star is nothing like the oldest it could be so there are 
potentially technological societies that are billions of years ahead of 
us - plenty of time for robotic probes to visit anywhere in the galaxy.

I suspect that unless there is some clever shortcut using physics we 
don't yet know about human inter stellar travel is just a pipe dream.

> _If the Universe Is Teeming with Aliens ... WHERE IS EVERYBODY?_ gives some
> interesting takes on the Fermi paradox.

One potentially very interesting way a technological civilisation may be 
detectable from Earth by spectroscopy is the presence of CFCs and HCFCs 
in their atmosphere. Once they master fluorine chemistry their discovery 
and utility is inevitable until they realise the damage to the ozone 
layer. Then they get phased out. Planets in transit across their suns 
are now being checked and so far nothing unusual has been seen.

Key point here is that fluorine is so reactive and calcium so abundant 
that you can't really get any fluoro-organic chemistry going without a 
technological civilisation. A handful of desert plants have mastered it 
to make monofluoracetic acid on Earth (extremely effective rodenticide).

It takes industrial scale manufacture before CFCs would be visible from 
afar. SF6 is another common one but it's scale height works against 
seeing it high in the atmosphere (its molecule is rather heavy).

-- 
Martin Brown