Thursday, April 22, 2021

The Search For Intelligent Life Other Than On Earth

It would be a worldview and Copernican perspective revolution if we discovered intelligent life somewhere other than Earth. The Drake equation is the leading way of trying to estimate how common such a possibility might be.

One related question that receives less attention, is what the likelihood is that if we encounter evidence of intelligent life outside Earth that this form of life will be extinct when we encounter it.

Without doing formal math, my intuition is that the probability of us encountering evidence of an extinct form of intelligent life before we encounter intelligent life that is not extinct is rather high.


neo said...

navy already found it and i'm entirely seriously believed it

andrew said...


neo said...

seriously how do you explain this ?

Graham Dungworth said...

I attended the 1st British Planetary Science conference at Leicester University in 1973.Early Spring the conference hall was subzero for ca. 3 days. As a post graduate I was employed as a post doctoral fellow in the Department of Exobiology at Nijmegen University. It was an international gathering and by luck and chance I sat next to a group of scientists that included John Oro from Houston, Carl Sagan well before his media fame , Bill Schopf back from a sabatical in Russia, armed with a personal gift to me of their cigarettes- aargh!, Phil Abelson,then 65+ and still very fit with a several mile run every day with enthusiasts before breakfast, Bart Nagy from Tucson, Alan Schwartz, ex Los Alamos.

By 1973 only 50 years had passed by since it was realised that our own galaxy was but one of countless other island universes out there. Currently we now observe as many galaxies as stars within our own galaxy. 50 years ago there wasn't a shred of evidence for the existence of extra solar planets. The Drake postulates couldn't have been addressed in 1923. By 1973 the most likely probability of our discovering intelligent life elsewhere was far less than the likely survival of the human race; there are some ancient forms that have co-existed for the whole of Phaneroic time ca. 600 million years. Although homo sapiens have been around for ca. order 10^6 year;6; and could be regarded as intelligent for hundreds of thousands of years,the time scale is minute when compared with-

the age of the sun and planets ca. 5 billion order 10^9 ; 9 year

the ages of other stars that condensed much earlier eg. 10 billion or 10^10 year

The Drake postulates are applicable for the previous ca. 10^2 year.

10 years prior to 1973 I commenced university education at a time when the human population surpassed 2 billion souls. Some 40 billion humans had preceeded us in the the evolution of our species. The consensus that Phil Abelson made was that the most probable scenario was that the human race would be extinct before we ever found evidence of extra solar sapient life. One particpant thought that they were here now, silently observing our every move, covertly. The background of most participants was extremely diverse with many a strange glance from a surprising number of scientists.

The average life of a species was ca. 6 million years yet even though intelligent? the human race was technologically capable for a scant 50 years. Intergalactic data transmission is of order 10^6 years.By the time an extragalactic observers receives our transmissions and replies we will most likely be extinct, replaced by nano particles of silicon, more sapient and smaller than a grain of salt that can more easily skip through wormholes of their own fantasies.

We arrived rather late on the scene of universal history. For those who now pass by and rest awhile on their travels, Tell them the glorious past has long decayed, no more prophetic laurels, the gods are dead,those sacred springs are dry and speak no more.

Ryan said...

I remember from my astrobiology course in university that if we make reasonable assumptions for Drake's equation, and assume a detectability window of 2,000 years (ie detectable civilizations either destroy themselves or become incomprehensible to the point of not being detectable) then the nearest detectable civilization should be about 2,000 light years away.

That's always stuck with me as a good rule of thumb.

The reality is our search techniques are so weak right now though that the there could be a peer civilization on Alpha Centauri and we wouldn't know unless they specifically targeted us with a message.

My bet is once we start getting better atmospheric data from habitable worlds we'll eventually find hints of intelligent life thanks to pollutants like CFCs or fallout from nuclear tests. I don't think these sort of atmospheric markers will persist long though which makes me think the first will detection of another intelligence will be of a living civilization, albeit a distant one that will take a few generations of telescopes before we even have a hope of finding it. I'm thinking something like 1/10,000,000 planets hosting intelligent life (maybe ~1,000 living civilizations).


Graham Dungworth said...

Yes- I remember that argument. A new planet is an every day discovery now.It might prove difficult to find a star without at least one planet.So Alpha Centauri is a good start.

In the early 60's I recall a cartoon, I forget the American author, that appeared in Melvin Calvin's book on Chemical Evolution. The scene was on some extra solar planet, whereon a desert plain, underneath a hot sun, the authordepicted an alien quadruped, totally deamoniased, breathing his last. The caption from his blistered mullet depicted his last words "Ammonia, Ammonia!". I can imagine a future extra solar probe heading for our closest solar neighbour; outbound at perhaps nine tenths of light speed leading a flotilla of similar craft, no bigger than a pinhead yet equipped with terbytes of AI.

The future of exploration is silicon.

Guy said...

Hum... there was a paper a while back that took all the Drake equation papers they could find and randomly sampled their coefficients, put those into a Monte Carlo and then sampled the output to form a density function. The most probable outcome was that we were the only intelligent life in the Milky Way with a non-significant possibility that we were the only intelligent life in the visible universe. Makes you feel... alone? With a lot of responsibility on your shoulders?
In addition the SETI folks have pushed the range of finding a civilization like our out a fair number of light years... can't find the numbers right now. And a significantly larger sphere has been search for more energetic civilizations. Cheers,

Ryan said...

Guy - got a link to that paper? Because that is contrary to everything I was taught in university. Anyone making that claim about the visible universe is also plainly not very numerate.

Guy said...

Hi Ryan,

I read the paper and it's pretty straight forward. From Wikipedia.

An analysis by Anders Sandberg, Eric Drexler and Toby Ord, suggests "a substantial ex ante probability of there being no other intelligent life in our observable universe".[83]

Sandberg, Anders; Drexler, Eric; Ord, Toby (6 June 2018). "Dissolving the Fermi Paradox". arXiv:1806.02404 [physics.pop-ph].

Ryan said...

Thanks Guy. Hadn't seen that paper before.

The results of that paper seem to be driven by their choice of probability distribution - the reciprocal (or log-uniform) distribution. So for example, they are assuming that it is 5x more likely that the fraction of stars with planets is 0.1 than 0.5.

And that happens repeatedly for all parameters.

This does not seem to me to be a reasonable assumption (and as far as I can tell I have more training astronomy than the authors do). It is replicated across all parameters.

So the paper could be summarized as "assuming intelligent life is rare, intelligent life is rare."

For anyone interested.

Graham Dungworth said...

The real goal is not the search for intelligent life elsewhere in the cosmos. As such we are a highly toxic species that has evolved from a close community relationship and a common language with a distrust of strangers of foreign languages and different cultures. Yet we have all conspired to exterminate most other predators.

What we really want to know is what makes the universe "tick" the what's it all about headbanger of a beginning and end. Is it infinite in extent, is there a a multiverse, what about trans infinities? The search for the Theory of Everything has run its course but is periodically resurrected.

Doug Adams postulated or at least I paraphrase " Once some intellect figures out just what the universe is all about it will instantly transform itself into some form even more incomprehensible than the last. Some say it has already happened before."

I favour evolutionary models in the Wallace/Darwinian sense that is anathema to astronomers. They often talk about galactic feeding frenzies yet disfavor Darwinian interpretations of the origin(s) of such systems. Awkward questions are dangerous, an easy food source for predators. All theories of origins can be tested by a thermodynamic approach; current models appear to contradict thermodynamic law. It lies at the base of all theories but who ordered it? Was it pure chance? but that is what chance and change is all about.
St Augustin argued a special place in hell is reserved for those who ask such questions, a case actually argued recently by the president of the European commission on the hell of Brexit! an English epidemic.
Infact, what about the English language? It's creole, a pidgin tongue. In Shakespeare's England it wasn't even spoken overall. Draw a 50 mile circle around London-well it happened there in will's timeframe. There were no English dictionaries. Infact, the first book on English grammar appeared in Shakespeare's early youth. It was written in Latin! So why did Latin perish? It was a hell of a difficult language to write. From hindsight it should never have persevered or become so dominant a world language. Did George W actually believe the commandments were written in English!?
Higher Math(s) has similar problems, even basic maths for most. Is a formal math approach to origins of ancestry and the what's it all about syndrome? I prefer a graphic. If it can't be handled by bog standard Inglish it aint worth a can of beans. If we ever find an intelligent alien I'm certain it's maths is better than mine. And if it's extinct hopefully it left a message on its tombstone, like "Kilroy was here".