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[Scribbler60]

This is a spin-off from another thread:

Human minds struggle to grasp exponentials. A hundred billion galaxies (minimum), each with many billions of solar systems. The total number of solar systems is conservative estimated as a billion trillion. Meditate on that number for a while. There is no way of getting one's head around such odds. lot more is possible in reality than we imagine.

...that I felt was more appropriate here under this Philosophy of Science heading.

It concerns the "rare earth" hypothesis; the idea that intelligent, technological life might be restricted to planets that have an exceedingly rare confluence of circumstances, with the Earth being as possibly the only one in existence that can generate a technological species.

To be clear, this hypothesis does not mean that there isn't life on other planets. There is a high possibility of life in the oceans under the ice on Europa (would we call them Europeans?), possibly similar on moons of other gas giants, and there are indications that Mars may harbour something akin to bacteria. It's my contention that life is ubiquitous throughout the universe; it's just that the circumstances that give rise to technological life are so rare as to be almost non-existent, except for us.

Now, I know that sounds ego-centric, and to be sure, I really really want to be wrong on this. But this is how I see it anyhow:

Earth enjoys a number of circumstances which have been theorized to be necessary for the rise of life. Some of them include:

• Earth is in the habitable zone, meaning that it is the correct distance from our star that surface water can exist. It doesn't stay frozen, it doesn't boil off.
• We have a single moon which creates regular tides.
• These regular tidal forces create tide pools which may have been vital in the development of single-celled lifeforms.
• Our solar system is populated primary by gas giants, which have a tendency to "hoover up" the detritus that flies through the solar system and impact planets
• Earth has a molten core, and as a result of this, the planet has a magnetic field which shields us from coronal mass ejection material and the solar wind. If we did not have this magnetic field, the atmosphere would likely have been stripped away.
• Our planet is alive with plate tectonics which, it has been demonstrated, has been vital in the development of life.
• Our atmosphere contains ozone in the upper atmosphere. This ozone filters out much of the harmful UV radiation which would make life as we know it impossible.
• It is a well-established fact that chaotic interactions and some blind luck were involved in the rise of intelligence. Were it not for an asteroid strike 65 million years ago, the dinosaurs would probably still be the dominant life-form, and our ancestors would still be scurrying about underfoot. There are countless lucky coincidences that had to take place - most importantly, the taming of fire by proto-humans - that were required to bring about a species capable of developing technology.
• There's also the problem of the "great filter" which you can read more about here: The Reason We’ve Never Found Intelligent Life Might be Because We Are Already Going Extinct

Now, Greta's point about there being multiple-billions of planets is well taken. I have difficulty even imagining such a vast number - frankly, I can't really do it.

But another number that is astronomically large is the combinant ratio of the above-noted events, and likely hundreds or thousands additional events, that were necessary for the development of technological life.

So, yes, there are billions of planets. How many planets are in the habitable zone
AND
have a single moon
AND
that moon is at the right distance and size to create tidal forces
AND
is in a system that is populated primarily by gas giants
AND
has a molten core with a magnetic field
AND
has plate tectonics
AND
has a blanket of UV-reducing ozone in the upper atmosphere
AND
had an asteroid impact that "cleaned the slate" to allow for the development of something like mammals
AND
has not been through the "great filter"
AND
the list continues on, and on, and on...

Miss out any one of those variables and, based on the information we have - which, I recognize, is a sample size of one - technological life would not have arisen.

Again, and I want to re-iterate here, I really want to be wrong on this. But, paraphrasing Sean Carroll, we must be very hard on those hypotheses that we want to be true.

I want it to be true that intelligent, sentient, technological life is abundant in the universe. But I just can't get my head around the numbers of happenstances that have to take place, in some sort of order, for technological life to arise.

What are your thoughts? Are we in a universe that is teeming with technological life and we just haven't found it (or it hasn't found us), or is it too far away, or are we the one-and-only technological species?

[Sy Borg]

Thanks for raising this, Scribbler.

It comes down to probabilities. Also, I think it best not to think in terms of the Earth's events so much as the impact of those events. For instance, an unusually large Moon may not be needed to stabilise the rotation of a planet with a less tempestuous history, that was not smashed into near liquidity by Theia. Further, while Jupiter sweeps up much debris, it also slingshots objects into the inner solar system with greater acceleration; the Jovian deity giveth and he taketh away. Whatever, gas giants the most common kind of planet, so that won't be a problem.

Molten cores and magnetic fields should be common, especially so in so-called "super Earths". That raises another question: is the Earth ideal for intelligent life or only adequate? A somewhat smaller main sequence star might last an extra ten billion years. A slightly larger planet would have more resources, and also note that most of the Earth is uninhabitable, being either ocean, desert or too steeply mountainous or cavernous. A larger planet may have higher gravity, which would male the landscape flatter.

Also note that life brought oxygen to the atmosphere. Until that point, the world was dominated by methanogenic microbes. Interestingly, microbes did not make the connective leap from colony to multicellularity until the atmosphere was oxygenated by blue-green algae.

Re: the asteroid destroying the dinos. Extinctions are periodic and it's the apex predators that are amongst the first to go. In hindsight, dinos were always going to be in danger unless they developed flexibility and adaptability to go with their size and brute strength. Note that, while humans are technically apex predators, we lack the same vulnerability because we are not just carnivores with limited diets but omnivorous hunters, scavengers, gatherers, growers, harvesters and manufacturers.

Still, there are more limits to be applied - the galactic habitable zones. Planets orbiting stars anywhere near the galactic centre are unsuitable for life due to high energies and activity (perhaps some undersea life as postulated in Europe and Enceladus). Further, there are most likely fierce rays emanating from the galaxy's centre, pouring down the spiral arms. The Milky Way resides well away from the dangerous "industrial area" of the galaxy, and between the energetic spiral arms. Further, the outskirts of the galaxy are dominated by hydrogen and helium and lack the heavier elements needed to make life as we know it.

I see intelligent life around the universe as inevitable and will most likely become more prevalent as the universe cools and spreads, reducing impacts and radiation to the point where habitable zones will increase. It's possible that Earth may have the first intelligent life but will surely not be the last, as per Feynman's comment. Observations suggest to me that the universe seems to operate more more like a giant system than a giant one-off random fluke, which is the upshot of the rare Earth hypothesis.

I could go on about this for pages but the post is already plenty long enough :)

[JamesOfSeattle]

2 more cents for the pot:

My view on the subject could be called the oily rags hypothesis. It's a well-known phenomenon that a pile of oily rags kept in a warm place, like a 100 degree Fahrenheit garage, can burst into flames. At some point a chemical reaction happens in some part of the pile, and that's enough to light the whole thing on fire.

So with respect to intelligent life, the question becomes: given just a single source of technological intelligence (us), how long will it take for that intelligence to take over the galaxy? (Not necessarily by us, but by what we produce.). A million years doesn't seem unreasonable (to me).

So the question is, after the first technological intelligence emerges, what are the chances another one will emerge in the next million years? What are the chances that after one spark has ignited in the pile of rags, another spark will ignite before the pile is in flames?

*

[Count Lucanor]

This is a spin-off from another thread:

Human minds struggle to grasp exponentials. A hundred billion galaxies (minimum), each with many billions of solar systems. The total number of solar systems is conservative estimated as a billion trillion. Meditate on that number for a while. There is no way of getting one's head around such odds. lot more is possible in reality than we imagine.

...that I felt was more appropriate here under this Philosophy of Science heading.

It concerns the "rare earth" hypothesis; the idea that intelligent, technological life might be restricted to planets that have an exceedingly rare confluence of circumstances, with the Earth being as possibly the only one in existence that can generate a technological species.

To be clear, this hypothesis does not mean that there isn't life on other planets. There is a high possibility of life in the oceans under the ice on Europa (would we call them Europeans?), possibly similar on moons of other gas giants, and there are indications that Mars may harbour something akin to bacteria. It's my contention that life is ubiquitous throughout the universe; it's just that the circumstances that give rise to technological life are so rare as to be almost non-existent, except for us.

Now, I know that sounds ego-centric, and to be sure, I really really want to be wrong on this. But this is how I see it anyhow:

Earth enjoys a number of circumstances which have been theorized to be necessary for the rise of life. Some of them include:

• Earth is in the habitable zone, meaning that it is the correct distance from our star that surface water can exist. It doesn't stay frozen, it doesn't boil off.
• We have a single moon which creates regular tides.
• These regular tidal forces create tide pools which may have been vital in the development of single-celled lifeforms.
• Our solar system is populated primary by gas giants, which have a tendency to "hoover up" the detritus that flies through the solar system and impact planets
• Earth has a molten core, and as a result of this, the planet has a magnetic field which shields us from coronal mass ejection material and the solar wind. If we did not have this magnetic field, the atmosphere would likely have been stripped away.
• Our planet is alive with plate tectonics which, it has been demonstrated, has been vital in the development of life.
• Our atmosphere contains ozone in the upper atmosphere. This ozone filters out much of the harmful UV radiation which would make life as we know it impossible.
• It is a well-established fact that chaotic interactions and some blind luck were involved in the rise of intelligence. Were it not for an asteroid strike 65 million years ago, the dinosaurs would probably still be the dominant life-form, and our ancestors would still be scurrying about underfoot. There are countless lucky coincidences that had to take place - most importantly, the taming of fire by proto-humans - that were required to bring about a species capable of developing technology.
• There's also the problem of the "great filter" which you can read more about here: The Reason We’ve Never Found Intelligent Life Might be Because We Are Already Going Extinct

Now, Greta's point about there being multiple-billions of planets is well taken. I have difficulty even imagining such a vast number - frankly, I can't really do it.

But another number that is astronomically large is the combinant ratio of the above-noted events, and likely hundreds or thousands additional events, that were necessary for the development of technological life.

So, yes, there are billions of planets. How many planets are in the habitable zone
AND
have a single moon
AND
that moon is at the right distance and size to create tidal forces
AND
is in a system that is populated primarily by gas giants
AND
has a molten core with a magnetic field
AND
has plate tectonics
AND
has a blanket of UV-reducing ozone in the upper atmosphere
AND
had an asteroid impact that "cleaned the slate" to allow for the development of something like mammals
AND
has not been through the "great filter"
AND
the list continues on, and on, and on...

Miss out any one of those variables and, based on the information we have - which, I recognize, is a sample size of one - technological life would not have arisen.

Again, and I want to re-iterate here, I really want to be wrong on this. But, paraphrasing Sean Carroll, we must be very hard on those hypotheses that we want to be true.

I want it to be true that intelligent, sentient, technological life is abundant in the universe. But I just can't get my head around the numbers of happenstances that have to take place, in some sort of order, for technological life to arise.

What are your thoughts? Are we in a universe that is teeming with technological life and we just haven't found it (or it hasn't found us), or is it too far away, or are we the one-and-only technological species?

Pretty close to my own reflections on this issue, so I definitely subscribe to this post.

Something else to consider is the Fermi Paradox (why if there are potentially so many civilizations, we never get evidence of them) and the Great Filter put in relation to the scale variables of size and time. What are the chances of any other civilization sharing our own time and space, comparing the vastness of the universe and its age with the insignificant time humans have been on Earth? In other words, instead of a fixed state of probabilities, another coordinate (time) must be taken into account to address the problem of simultaneous existence. Billions of civilizations could have been born and gone extinct, but why would they ever coincide in time with us? We're talking about 13,800,000,000 years against almost 12,000 years that have seen some type of civilization in Earth and just 50 years of modest space technology.

[Sy Borg]

Count, we can at least agree that the vastness of both space and time stands as a significant obstacle to us encountering intelligent life - at least until significant interstellar exploration becomes possible by, as James noted, something that stems from humans. What we think of as human today clearly cannot survive long in space. Then again, for context, we today would seem weirdly alien to Neanderthal and early H. sapiens too, and with some godlike abilities.

[Scribbler60]

Of course, there's "evidence" (I use the term loosely at this point) that the Pentagon has been studying the UFO phenomena for a number of years, though on an extremely limited budget - something like $22 million over the course of five years (bear in mind that the annual Pentagon budget runs in the neighbourhood of $600 billion; $22 million over five years isn't enough to supply the Pentagon with toilet paper).

More here: Secret Pentagon Program Spent Millions To Research UFOs

One also has to bear in mind that there is not, as yet, any causal connection between something that's unidentified and the existence of extraterrestrial technological life. Neil deGrasse Tyson gets into that here: Neil deGrasse Tyson gives take on UFO video

[Sy Borg]

It seems unlikely that alien craft would have air traffic control lights.

[Scribbler60]

It seems unlikely that alien craft would have air traffic control lights.

Oh, I don't know about that. If I were an alien visiting a foreign world, I'd want to blend in an look like local aircraft.

But I suppose that's out-of-context from this thread anyway.

[Sy Borg]

It seems unlikely that alien craft would have air traffic control lights.

Oh, I don't know about that. If I were an alien visiting a foreign world, I'd want to blend in an look like local aircraft.

But I suppose that's out-of-context from this thread anyway.

Any entities (my money is on AI :) with the technology to travel interstellar distances in a practical period of time could easily cloak themselves against radar, or perhaps even against vision. They would be intelligent enough to know that air traffic control would note unauthorised flights.

Still, the Fermi paradox says precious little about the chances of intelligent life being present elsewhere. Even if we build huge telescopes that peer ever further into the cosmos, we are only seeing what happened billions of years ago, and the universe was a more tight knit and tempestuous place then, more hostile to life. A distant alien would need to be less than a 100 light years or so distant from Earth to detect humanity's early radio waves, and even then they would not find any signs of today's modernity. Note that our galaxy is 100,000 light years across, so we can only peer into our local neighbourhood to a small degree without looking at periods before modern humanity.

The Earth does appear to be quite rare, but the probabilities against it being unique are huge and, as above, there is no meaningful evidence against the existence other planets stable enough to host intelligent life. It's akin to checking out your local neighbourhood and then assuming that the rest of the world, history and future will probably be roughly the same as observed in one's local area today.

[Count Lucanor]

Maybe we should redefine "uniqueness" in this context. As Greta has pointed out, given the distances and limitations of space travel, we can barely "peer into our local neighborhood". Imagine an ant living in your backyard and its very, very low chances of ever meeting another ant possibly living in Pluto. Since it is practically impossible that the Earth ant does something to meet the Pluto ant, its existence becomes irrelevant. The Earth ant could go on with its life in your backyard, completely disregarding the problem of a possible ant in Pluto, and rightly feeling somehow "unique".

[Present awareness]

You may considered yourself, one of billions of humans living on Earth. Earth may be considered one of billions of planets, orbiting a star. The Sun may be considered one star among billions in a galaxy and our galaxy one of billions in the universe. However, before you begin to feel insignificant, you must realize the the entire universe is dependent on your own existence, from your own personal point of view! The perceiver and the perceived are dependent on each other and that Is why the universe did not exist from your own personal point of view, until you were born. Like Lucanor says, it matters not whether we are alone, or if the universe is teaming with life, because of the vast distances involved, we will never know.

[Eduk]

How many planets are in the habitable zone

A quick google says there are 50 sextillion in the universe. Which is 50,000,000,000,000,000,000,000 written down. Certainly that is number with no meaning to me, you could remove a 0 from it (or 6 0s) and I wouldn't even notice.
Also remember the universe is quite old. Again a quick google says there have been habitable planets around for about 10 billion years.

So given the number of planets and the length of time then I would say the probabilities of technological life elsewhere in the universe are probably pretty good. At worst I would be agnostic on the proposition as, to be fair, I have very very little real information to base any guess on. I certainly would not be sure of myself either way and I don't understand why you are Scribbler?

[Steve3007]

...my money is on AI...

It does seem overwhelmingly likely that if there ever is a first physical contact with an alien civilisation, here in the solar system rather than at their home, then it won't be with them directly but with their AI representatives, provided that alien life forms share some characteristics with humans:

1. Finite, short individual life spans.
2. Boredom.
3. Bodies that aren't naturally adapted to spending a long time in space (a reasonable assumption).
4. Individualism - i.e. wanting to experience things within one's own life span rather than regarding oneself as part of a collective and therefore being content for one's distant descendants to do all the fun parts.

I wonder if the initial evolution of intelligent life (as opposed to the continued "evolution" of intelligent life as it replaces itself with AI) always results in the above characteristics. Clearly artificially created machines (at least as we currently understand them) don't need to have any of them, so they can be sent on space missions lasting thousands of years.

Another thought: Perhaps, when deciding how best to design these space-faring artificial representatives, intelligent life might actually decide to use the powerful principles of evolution and natural selection. They/we could then send loads of probes out into space, but deliberately give them the ability to make similar copies of themselves and then let natural selection choose which ones are best adapted to the environment of long space travel. In this scenario, interstellar space would be littered with the remains of dead space probes that weren't up to the job, while possibly some of the surviving probes pondered the cruelty of life and discussed it with each other across the emptiness of space.

[Sy Borg]

...my money is on AI...

It does seem overwhelmingly likely that if there ever is a first physical contact with an alien civilisation, here in the solar system rather than at their home, then it won't be with them directly but with their AI representatives, provided that alien life forms share some characteristics with humans:

1. Finite, short individual life spans.
2. Boredom.
3. Bodies that aren't naturally adapted to spending a long time in space (a reasonable assumption).
4. Individualism - i.e. wanting to experience things within one's own life span rather than regarding oneself as part of a collective and therefore being content for one's distant descendants to do all the fun parts.

I wonder if the initial evolution of intelligent life (as opposed to the continued "evolution" of intelligent life as it replaces itself with AI) always results in the above characteristics. Clearly artificially created machines (at least as we currently understand them) don't need to have any of them, so they can be sent on space missions lasting thousands of years.

I am imagining everlasting, phlegmatic conformist aliens each chillin' out in an identical way (maybe laying back on deck chairs?) while the AI covers the details of their thousand year space cruise :)

If they are Borg, then there would not be individuals but perhaps arrays of dumb terminals in a mobile hub (ie. space ship), that can be charged and controlled by a "central hub".

#4 reminds me of interviews I've seen with people who state that they would be keen to undergo a one-way trip to Mars, or wherever. As far as they are concerned, exploration is the ultimate experience. Diversity and general eusocial tendencies come into play here. An entire species doesn't need the characteristics needed for space travel, only a small minority. As always in nature, the environment effectively decides on the characteristics of its denizens.

In that sense, and given findings in epigenetics, the notion of nature/nurture is an uneven dichotomy. "Nature" is essentially just accumulated historical "nurture", driven by environmental conditions of the past. So entities in space will surely share many characteristics just as entities in oceans are often streamlined and airborne animals will be aerodynamically shaped and be relatively lighter than their terrestrial counterparts.

What if we met aliens and found them repulsive in odour, appearance, aesthetics, ethics and manners? (until they became trendy ;). That may help us to better understand our similarities and kinship as Earth beings.

[Steve3007]

I am imagining everlasting, phlegmatic conformist aliens each chillin' out in an identical way (maybe laying back on deck chairs?) while the AI covers the details of their thousand year space cruise

If you mean they'd be watching the TV coverage of the AI's adventures, they would have to be very chilled and phlegmatic compared to us flighty humans. Most humans these days would switch channels within 5 seconds. I remember, long before the Spirit Opportunity and Curiosity rovers started trundling around Mars finding all those sedimentary rocks and tantalizing possibilities of martian fossils, Carl Sagan excitedly imagining how when it happened the whole world would unite in the excitement of remotely exploring Mars together. Some of us are still very interested in Curiosity's tweets, but hardly the whole world. Sorry Carl. Celebrity Big Brother is more interesting, apparently.

...An entire species doesn't need the characteristics needed for space travel, only a small minority. As always in nature, the environment effectively decides on the characteristics of its denizens.

Yes, that's true. I guess that's one of the advantages of massive human over-population of the globe.

In that sense, and given findings in epigenetics, the notion of nature/nurture is an uneven dichotomy. "Nature" is essentially just accumulated historical "nurture", driven by environmental conditions of the past.

Yes, that is a good point. Just as comedy is tragedy plus time, so Nature is Nuture plus time and selection.

On the theme of aliens sending self-replicating and evolving AI space probes out to make contact with other civilizations: I can imagine philosophical/theological discussions between those intelligent space probes, as they drift apart from each other on their separate missions, with two camps arguing over whether they evolved spontaneously with no objectively existing meaning to life or whether their creators imbued them with a purpose to seek out new life and new civilizations. Some of them might dispute whether these supposed biological life forms with which they're supposed to be making contact really exist at all.

What if we met aliens and found them repulsive in odour, appearance, aesthetics, ethics and manners? (until they became trendy . That may help us to better understand our similarities and kinship as Earth beings.

I'd never really considered before that of all the problems we might face if we finally came face to face with aliens, body odour might be one. Or what if we just found them boring? Like a seldom-seen distant relative who, on the occasional family gatherings, spends the whole time talking about the car journey there. ("We had terrible trouble at those road works near Alpha Centauri...")