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2 is also unlikely because planetary systems did not all form at the same time.  Even if they did, it's unlikely that out of billions of years of evolution, intelligence and civilization would arise within a million years of each other.

Personally I think 3 is the most likely.  The ingredients and environments that led to the origins of life on Earth (insofar that we understand its origins) are extremely common, so I think life is common.  As for intelligent life similar to ourselves -- who knows.  But interstellar travel is hard, the speed of light is probably not breakable (I don't think warp drives are physically possible), and colonizing other planets may be harder than imagined.  So I imagine most civilizations remain on their planets, and few if any go on to colonize the galaxy.

The question of the number of communicative civilizations out there is also difficult.  We know almost nothing of how many would be communicative, in what manner they would communicate, or for how long they would do so.

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Hmm I also opt for the 3rd possibility. But it is probably much more complicated than this.
Watsisname, said something very interesting:

Watsisname wrote:

As for intelligent life similar to ourselves

similar to ourselves is also an interesting assumption that, if true, can explain why it is very difficult to colonize the galaxy. As we are composed of matter, it is very difficult and energy demanding to travel fast inside space. Now if another sentient life form is composed e.g. of energy it may be easier for them to travel fast. But this needs to be proved that it can exist. And this is even more difficult.
All three possibilities are likely with 1 and 3 the most likely.
I just watched Clara btw interesting movie that is about this topic.

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alfa015 wrote:

Source of the post Drake Equation (Maccone, 2012)

New exoplanets and new solar-systems are being discovered every day, along with advances in biology and technological sociology. Altogether, these new insights refine our models of how life can develop on other worlds, how it can become intelligent enough to form a civilization and what Great Filters apply. Coupling this breakneck pace of revelations with the fact that we haven't really searched for extraterrestrial civilizations long enough to make any assertions of real consequence - the final result is that any claims, even those made by the Drake equation, are outdated as soon as they are published.  

To follow this vein of thought, I will side with Watsisname and the others here on a purely statistical principle: it seems like life inevitably will evolve in some form in our galaxy and elsewhere. Certain strong filters inhibiting it's evolution will apply without exception. The reason we have not detected them is due to a mix of the youth of our searches, extreme light-lag and differing timelines between civilizations, that certain civilizations won't or can't communicate and that maintaining order and even vague hegemony throughout a huge interstellar empire is REALLY hard, harder even then traveling to those distant colonies.

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Out of the countless factors and filters in any calculation for the probability of life being within the range of detectability, if a single one is 10 times less likely that could potentially place it not only outside of our own galaxy but outside the small group of galaxies that will remain within the light travel distance Cosmic Expansion will leave us with.

In other words by the time we could contact them they'll be so far away they could never get a response message to us before they were too far away for light to ever reach us. I'll resist any references to anthropocentric reasons.

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Gnargenox wrote:

Source of the post I'll resist any references to anthropocentric reasons.

For the sake of argument, what would be the core message of your resistance?

Since we really don't have enough data to make any concrete claims about specific extraterrestrial characteristics, we may then as well treat the universe as the one you propose - so what exact conditions would be present in that universe (disregarding for the moment if that universe is indeed the one we live in)?

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Currently what we know isn't enough to rule out so many possibilities or assign probabilities to them.  Exoplanet observations, including of their atmospheres, may change that in a few decades.  I think that wont help us too much to reduce the possibility space, but we will perhaps become able to assign some probabilities.

If advanced life is common, it could still be that Earth is very special in that advanced life evolved on land, in a relatively thin atmosphere and in modest gravity, without which we wouldn't be able to go to space.

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Stellarator wrote:

Source of the post For the sake of argument, what would be the core message of your resistance?

Perhaps I've been watching too many Ancient Aliens TV episodes. Yes indeed, we have only one example of life, but what can we extrapolate from it? What conditions are necessary for us to exists and why are the constraints of such all within large sweet spots, abundantly prosperous for lifeforms like ourselves?

As midtskogen mentions about our atmosphere and oceans, intelligent life could form in a manner that would prevent eventual space travel (or even being detected) such as life that must live underground or under miles thick ice or are immobile lifeforms or in environments that prevent observing anything beyond their home world like life deep within a Gas Giant might be. Things could be taken further. We have convenient stepping stones to space, the domination of our moon and Mars are achievable goals, that make the evolution towards interstellar space travel easier than you would find statistically probable.

I don't know if the word I'm thinking of is Anthropocentric, since I don't mean to say the universe exists only for us, but only that we are the result of more than just simple natural processes. We are in a world where we have near absolute control over our environment and our own biological processes, things not quite necessary for intelligent life to survive. The human brain is extraordinarily expensive Calorically speaking and really not required for survival and or even prosperity or total world domination. This is not to imply we have been guided by outside forces or things where set up intelligently for our benefit. Only that we are luckier than we realize, that things are better than average, better than good, even better than super-fantastic for us. We are winners of multiple lotteries and condition are so good for us that we have the potential to live forever and anywhere in the universe. That seems to be on a scale similar to the Heart of Gold's improbability drive.

Can we expect conditions elsewhere to also be as positively skewed for other lifeforms as we see for ourselves? How close in space and time are we to these other multiple lottery winners and are they also capable of and intelligent enough to communicate their presence to us? Chances seem slimmer and slimmer the more we learn about ourselves, making things appear Anthropocentric.

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Gnargenox wrote:

Source of the post I don't know if the word I'm thinking of is Anthropocentric, since I don't mean to say the universe exists only for us, but only that we are the result of more than just simple natural processes.

From the Merriam-Webster dictionary:

"ANTHROPOCENTRIC"
adjective
an·thro·po·cen·tric | \ ˌan(t)-thrə-pə-ˈsen-trik
https://www.merriam-webster.com/dictionary/anthropocentric?pronunciation&lang=en_us&dir=a&file=anthro03

Definition of anthropocentric:
1 : considering human beings as the most significant entity of the universe.

2 : interpreting or regarding the world in terms of human* values and experiences.
*As a species in this context.

Yes, you are using the word correctly, at least in context with the second definition. But it is easily one of the weakest Fermi Paradox arguments; that our circumstances are so special that a) we are alone and unique in that regard or b) we as well be because the conditions are so rare and the distances are so vast. It mistakenly assumes that the processes that resulted in our existence apply to the universe in its entirety, and suffers from single-sample bias. Our existence is not evidence of anything aside from the possibility that these things are possible in the universe. This is really assuming that Earth is the best possible host for life just because we are on Earth and we think we are so special. I also dislike the term 'cosmic lottery'. It entails that even in a random system (which an ecosystem is not) intelligence in life-forms is a 'goal' for evolution in some way and is a very arrogant stance. Evolution has no goals, and this ignores the examples of 'intelligence' in other Earth organisms that could have a shot at technological societies - like certain species of avian. We also do not know if intelligent life existed at some point in Earth's prehistoric past. Obviously not high technology, but at least stone age. Evidence of that would not fossilize very well if older then some millions of years. We have not discovered any animal lineages that resulted in intelligence, but the possibility remains.

Therefore, we can consider ourselves a statistically AVERAGE sample of the universe's life pool. To state the opposite is essentially an argument from ignorance, even if it is based on scientific observations suggesting that the conditions suitable for technological intelligent life-forms are rare. Those observations do not say that technological life *is* rare or non-existent, they only mediate the factors that lead to intelligent life. That is it. We don't have enough of these observations to say with even 50% confidence that humanity on Earth is extremely fortunate or rare. Many people would say "Glass half-empty, glass half-full" if confronted with this rough probability game, but if we consider the vast wilderness of the Milky Way alone, taking into consideration galactic habitability zones and star type, a brute-force application of probability skews the likelihood of life being present at some evolutionary stage in a plethora of environments.

That is my counter to your resistance (on principle alone), and may contain points you've probably heard of before, and will inevitably dismiss.    

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Stellarator wrote:

Source of the post Therefore, we can consider ourselves a statistically AVERAGE sample of the universe's life pool.

I agree with most of what you've said, but this part seems problematic.  For a sample size of 1, the very notion of doing statistics on it is nonsensical.  For example, the standard deviation would be undefined (as in it would involve a division by N-1 with N=1).  

I would instead argue that we cannot make any strong conclusions about where to place ourselves in the context of life elsewhere in the universe.  Maybe we are "average", or maybe we are exceptional outliers.

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I don't mean to sound as if I am espousing the Rare Earth Hypothesis, that we are alone because the circumstances needed for life to occur happen so seldom that only once every billion light years we would find life. I'm not even considering what else could possibly be out there. My only argument is that things are too good for us here. One thing I've learned from Space Engine is there are no planets prettier or better for us than Earth is. Others come close to an ESI of 1, but none will be free of volcanic eruptions or be room temperature year round or rain down Skittles once a day.

Earth might be the best place to be, for us, but it could also be alot worse and we would still be here. We could have evolved exactly as we did with no difference in our environment, but there could have been nearby stars ready to go supernova and destroy us in the blink of an eye. We might have appeared on a planet in a galaxy on a collision course with another galaxy that was going to happen alot sooner than our destiny with Andromeda and would be dodging stars in a few more million years. We might have developed on a planet as rich in metals as Earth but are inaccessible due to different geology and we never would leave the stone age. We might have developed on a continent such as Africa and found monstrous dinosaurs on other continents that would have isolated us to one place stifling any growth beyond hunting and gathering. To me it seems there are many factors that are in our favor to not only survive but to excel. Is it really just an average thing that we have the potential to live on other worlds?

Evolution not having goals also shows me we are more than a fluke. Evolution seems geared towards constant turn over yet our lineage as brought us to the point of being able to over throw Natural Laws, and it has happened extraordinarily fast in evolutionary terms. Understandably biology is one of the most complex organizations matter could form, the step from prokaryotic life to eukaryotes took billions of years but the step from humans using fire to using nuclear power happened fairly quickly, but it is possibly just as complex of a task. Not only has humanity busted though Great Filters of the Fermi Paradox, but we've done so with flying colors.

I don't see how we can say we are average with only one sample. (I see Watsisname picked up on that too). I think the chances could be the same that we appeared on a world favorable to space travel or unfavorable to it. I think things are more favorable for us than an average would give us. I guess if we are average we should expect other life to be average for its environment, but that's pretty meaningless since we don't know other ways life could evolve. Whether they are in our own galaxy or not is impossible to say too.

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An extreme example to serve as food for thought:  

Suppose that many technological civilizations last for thousands of years, and many others last billions of years, but few last for millions of years.  Perhaps because most either wipe themselves out in the rapid technological advancement phase, or they manage to "safely harness their destructive powers" and become interstellar.  Then a plot of civilization lifetimes would form a bi-modal distribution.  In this scenario, most civilizations would not be average!  Civilizations that die out after millions of years would be average, but also the outliers.  

What will we be?

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Gnargenox wrote:

Source of the post We might have appeared on a planet in a galaxy on a collision course with another galaxy that was going to happen alot sooner than our destiny with Andromeda and would be dodging stars in a few more million years.

If we live through that collision, it would likely be pretty uneventful.  The distances between stars are so great that it's not very likely that passing stars would disturb our solar system much.

We ourselves are undetectable outside our solar system with our current technology, and I'm not sure if it really makes sense to judge the probabilities for life more advanced than us, since it would force us to make so many assumptions.  Historically we've pretty consistently been wrong about future technology.  Perhaps more advanced technology is undetectable.  Perhaps advanced life, before becoming detectable by less advanced life like us, discovers the meaning of life, the universe and everything, gets so disappointed and stops progress.  We can make an endless list of possible reasons why we don't see more advanced life.

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Watsisname wrote:

Source of the post I agree with most of what you've said, but this part seems problematic.  For a sample size of 1, the very notion of doing statistics on it is nonsensical.  For example, the standard deviation would be undefined (as in it would involve a division by N-1 with N=1).

I would instead argue that we cannot make any strong conclusions about where to place ourselves in the context of life elsewhere in the universe.  Maybe we are "average", or maybe we are exceptional outliers.

Ah, forgive me. I was rushed when I typed this out and so didn't get the point across properly. I was (rather clumsily now that I read it again) trying to invoke the Principle of Mediocrity here in regard to our presence on this planet, communicating the idea that if we represent a certain outcome (intelligence in organisms), then that outcome should statistically be pervasive throughout the cosmos. If it was not, then we wouldn't be here, or at least make it this far in our development. An opposing counter to this would be the anthropic weak principle; that we observe the universe in the first place because a certain environment was fined tuned for us to observe it, via survivor bias (or a supernatural force, if one is religiously inclined, which of course is not the case here). This just strikes me as a very narrow view of the universe.  A neutral stance would be the one you pointed out (and to be honest I lean toward as well), that there is only 1 sample and so not a lot of predictive implications can be made.

Gnargenox wrote:

Source of the post I don't mean to sound as if I am espousing the Rare Earth Hypothesis

Not at all. It seems like you are arguing from the extremist side of the Great Filters theory (something that I follow as well): certain factors inhibit life in the universe from developing intelligence that can achieve space travel and communicative abilities with other alien species. That is all well and good, but if you couple the effects that natural filters of cosmic and planetary environments (Great Filters) have on life on the extreme side of that theory (that the Filters knock down life more then we expect) with human-centered confirmation bias, you can end up manufacturing an elaborate world-view that results in you seeing all events leading to the existence of intelligent life as humans being the ONLY way we (or other lifeforms) can evolve. You admit this here:

Gnargenox wrote:

Source of the post I'm not even considering what else could possibly be out there.

Gnargenox wrote:

Source of the post One thing I've learned from Space Engine is there are no planets prettier or better for us than Earth is.

A good point, and SE is very useful for exploring this concept. But I hope that you are aware of the fact that the game engine's generation of exoplanetary environments in v0980 and prior editions is NOT very realistic. An obvious example would be the lethal amounts of SO₂ and CO₂ in the atmospheres of planets with life. You and I both know about the huff on this forum concerning these ridiculous ratios of gas. Thankfully, SE 0990 appears to have remedied this - if Harbinger's streams are anything go by.  Inaccuracies go deeper then that of course, but in time SE will more accurately match geological, chemical and even biological models for exoplanets.

In addition, just because an alien environment is inhospitable to our organism, doesn't mean that it is the only possible environment for life to develop. Indeed, I predict that the rule of thumb for the galaxy will be that each life-bearing planet will have enough chemical dissimilarities between them that biology on one couldn't function on the other. I discussed this idea elsewhere on the forum. 

Also, Earth is not all that great for life. I know, that seems an idiotic statement, but the idea is based on actual observations, and we must remember the several times life was almost shook off our world. But back to the theory: Astronomers know two things about the universe: that K dwarf stars are far more common in the universe then our homey G-dwarf stars (both are outnumbered by M-dwarfs, but that isn't relevant here) and that super-earth worlds are far more common then 1 Earth-mass planets (it is worth noting that this is a selection bias on our part, because we can't detect far-out Earth-mass planets as well as super-earths). K-dwarf stars (and lower-class G-stars) are calmer then our sun, and have potentially double the lifespan. They don't flare like their smaller M-dwarf cousins, and many support solar-systems. If even a fraction of these have some gas-giants in their outer systems, then debris interrupting developing life on an inner super-earth would be averted. The super-earth would need just the right mass to support tectonics and not drown in a global ocean or become desert. Further, it wouldn't need a moon, because tides would be offered by its closer star. A larger, geologically active planet would have stronger magnetic fields, so solar-radiation would not be a big an issue as it is here on Earth, coupled with a thick atmosphere. This, combined with a stable, long-lived sun, would give life a comfortable and safe home. Jump to intelligence evolving on that planet, and Dirigible technology could be more effect because of the thicker atmosphere. That would be your 'stepping stone' to high atmospheric exploration, then to low-earth orbit and beyond. There are a lot of nuances to this premise, as other forum readers will be quick to point out, but you get the picture. Earth is just good enough to let us live. 

Gnargenox wrote:

Source of the post Not only has humanity busted though Great Filters of the Fermi Paradox, but we've done so with flying colors.

Not really. Yes we have survived, but for context 99% of all life that has existed on this planet went extinct over 4 billion years, including most of our closest relatives in the hominid group. Homo sapiens itself came VERY close becoming extinct several times. "Barely scraped by" would be a term I'd use, not "flying colors". If we were so successful and lucky, it stands to reason that other species on Earth would have too, regardless of intelligence. Again, this is a survivor-bias fallacy. Do bear in mind that we are not out of the woods yet and a lot of things in the universe could kill us or knock us back into the stone age, permanently.

Well Gnargenox, this post turned out longer then I expected, so humor me. I think when the James Webb and other instruments turn starward, we can answer some of these questions with more concision. Then we can debate this more! It's pretty fun .

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Wat I like this idea a lot!

An extreme example to serve as food for thought:  

Suppose that many technological civilizations last for thousands of years, and many others last billions of years, but few last for millions of years.  Perhaps because most either wipe themselves out in the rapid technological advancement phase, or they manage to "safely harness their destructive powers" and become interstellar.  Then a plot of civilization lifetimes would form a bi-modal distribution.  In this scenario, most civilizations would not be average!  Civilizations that die out after millions of years would be average, but also the outliers.  

What will we be? [img=24x24]http://forum.spaceengine.org/images/smilies/icon_e_smile.png[/img]

I do think there are probably other space faring species in our own galaxy but our galaxy is huge and we are a very rural part of the galaxy, we probably wouldn't detect them- our technology is still relatively primitive in this regard.

A small amount of time biologically or geologically, can be a huge amount of time technologically- imagine how much more advanced life could have become on our planet had the K-T event not occurred, perhaps a 65 million year head start!

Lol what was this I saw about passing through Great Filters with flying colors?  We've wrecked our environment and poisoned ourselves with our greed and pollution.  Our largest Great Filters lie ahead of us and we wont pass them with the type of political and economical systems we currently have- nor will we survive long enough to colonize space with a greed-based short sighted system.

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A-L-E-X wrote:

Source of the post A small amount of time biologically or geologically, can be a huge amount of time technologically- imagine how much more advanced life could have become on our planet had the K-T event not occurred, perhaps a 65 million year head start!

Or not.  One can argue that the K-T event was the start of the age of mammals, and here we are.  Whether it was necessary that the dinosaurs went away for something like us to evolve is certainly debatable, and so is what the outcome of evolution would be if there had been no K-T event, but without it, life on Earth would certainly be very different.  Catastrophic events aren't necessarily bad for evolution.  Bad for some species, but change opens niches to be filled by others, and evolution speeds up.  Some change is good.

So, if life starts on a planet around a quiet sun and in a quiet solar system for billion of years, would advanced life evolve, or would life simply evolve into a stable configuration and then stall?