# amount of aliens in the galaxy



## megamaniac (Dec 21, 2012)

Given 500Billion planets in the galaxy, 1/10 capable of supporting life = 50B;
of those 1/2 have life = 25B; 1/5 have insects, fish, birds, animals = 5B;
1/5 have mammals and hominids = 1B; 
of those hominids(or other species) 1/10 evolved intelligence = 100m;
%25 die out due to wars, disease, etc. + %25 die due to disasters, natural or other catastrophe such as meteors, left = 50m.
1/10 send ships, probes, signals, lazers, etc. = 5m.
So, we have 5million alien species in the galaxy that could or might or have or will contact Earth.  Is 5m spread out in the entire galaxy enough to have a dialogue or contact or visitations or invasions?  No.  Not enough spread or odds.  
Ifcourse, of those if some species (say 1/100) has a population of 100B, and has lasted 10m years, and has spread all over the galaxy, thus... there are 50,000 super intelligent alien species in the galaxy.
It is possible that atleast 1/100 of the above have evolved beyond their physical form and exist as pure energy.  Or say they have genetically engineered a form of life that is capable of living 1000 years, or be able to hibernate in space, then 500 species in the galaxy are capable of inter-stellar space flight in their life span.  Thus, they live forever, and travel all across the universe no matter how long it takes.

It's just a question if such God-like aliens already do exist, and have existed for millions of years, or if humans are the most advanced species in the galaxy.


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## Victoria Silverwolf (Dec 21, 2012)

The problem is that all these numbers are extremely uncertain.  We don't really know very much about what conditions are necessary for life to exist, and we certainly know almost nothing about the chances of it evolving to intelligence (whatever that means), the chances of technological development, the chances of survival, and so on.  

My hunch -- and it is just a guess -- is that intelligent life exists somewhere else in the universe, probably in great abundance, but that the inability to break the speed of light, combined with the truly unimaginable distances involved, make it extremely unlikely for contact between two different intelligences to take place.

I hope I'm wrong about that!


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## Peter Graham (Dec 21, 2012)

> Given 500Billion planets in the galaxy,


Do we know that to be an accurate figure?



> 1/10 capable of supporting life = 50B;


Do we know that to be an accurate figure.

What is our definition of "capable of supporting life".  Do we just mean life as we know it?




> of those 1/2 have life = 25B


Any evidence for that assertion?



> 1/5 have insects, fish, birds, animals = 5B;


Any evidence for that assertion?


> 1/5 have mammals and hominids = 1B;


Any evidence for that assertion?



> 1/10 evolved intelligence = 100m;


Any evidence for that assertion?



> %25 die out due to wars, disease, etc. + %25 die due to disasters, natural or other catastrophe such as meteors, left = 50m.


Any evidence for those assertions?



> 1/10 send ships, probes, signals, lazers, etc. = 5m.


Any evidence for that assertion?



> So, we have 5million alien species in the galaxy that could or might or have or will contact Earth.


No we don't.  We have a wildly speculative theory, apparently unsupported by _any_ hard evidence, drawing entirely unwarranted conclusions which are themselves entirely hypothetical in nature.  The theory also appears to take no account of the length of time the galaxy has been in existence and seems to presuppose - again without a shred of evidence - that the 5 million species are all active at the same time as we are.




> Is 5m spread out in the entire galaxy enough to have a dialogue or contact or visitations or invasions?  No.  Not enough spread or odds.
> Ifcourse, of those if some species (say 1/100) has a population of 100B, and has lasted 10m years, and has spread all over the galaxy, thus... there are 50,000 super intelligent alien species in the galaxy.
> It is possible that atleast 1/100 of the above have evolved beyond their physical form and exist as pure energy.  Or say they have genetically engineered a form of life that is capable of living 1000 years, or be able to hibernate in space, then 500 species in the galaxy are capable of inter-stellar space flight in their life span.  Thus, they live forever, and travel all across the universe no matter how long it takes.


Again, one tiny shred of reliable, peer-reviewed and robustly tested evidence that any of these assertions might be true would be nice.  You are simply piling hypothesis on assumption on opinion on presupposition on speculation.  I can do the same thing:-

"Britain is clearly the best country in the world to live in due to the fact that we have a massive economy, a temperate climate, enormous diversity of flora and fauna, gun control leading to very low murder and crime rates, a proud heritage and the fact that we gave the world the English language, the best legal system, the industrial revolution, the greatest literature and the greatest thinkers and scientists."

"The best part of Britain is England.  It might not be as dramatic as the other parts of the UK in scenery terms, but it's where the money and the jobs are."

"The best part of England is the north.  The south is one enormous housing estate and carpark, full of w**kers who tie their jumpers round their necks and talk about money all of the time."

"The best part of the north is Cumbria.  Beautiful and unspoilt."

"The best part of Cumbria is the south east of the county, which is easily accessible to the rest of the country, is affluent and has some of the lowest crime rates and unemployment stats in the whole UK."

"The best part of south east Cumbria is Kirkby Lonsdale.  Ruskin himself wrote that there was no lovelier place.

"The best part of Kirkby Lonsdale is the old, central core."

"The best part of the old central core is Slobbergate (not it's real name!).  Pretty and near the shops."

"The best house on Slobbergate is number 21, where, coincidentally, I happen to live."

Therefore, as we have seen, I live in the best house in the world.

Hypothesis first, by all means.  But then gather in, assess and _understand_ the evidence before stampeding  to the conclusion.......

Regards,

Peter


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## Bowler1 (Dec 21, 2012)

It seems everywhere we go in space organic compounds have been found. This could just be our local area of space and it could be life from Earth infecting local space but I find that unlikely. The only other conclusion is that space is full of these organic compounds. That being the case the seeds of life must be everywhere.

Now galaxies are densely packed at the centre and that for the majority of planets in any galaxy, life will be zapped to a radioactive sludge before it has a chance to start by close proximity to all these suns. However, not all planets are going to be in this densely pack region of the galaxy, which is usually the core/centre of the galaxy. Oddly enough, Earth is not in the centre of the galaxy and we’re way out on the edge on a spiral arm. I’m going to plant my flag and say life would normally develop in the safer edges of a galaxy, well away from the very nasty cosmic radiation.

That still leaves quite a lot of material knocking around for life to get going on. The assumption that we’d be able to spot other intelligent life has lots of problems with it. We’ve only really been looking for life in the last 100 years or so, you could change that number, it’s not that important. Human life has existed, us the Homo Sapiens, for around 250k years, with 50k years for human culture. Our technology has only evolved to the point where we can peer into the depths of space with some understanding in the last 100 years or so. If a human from today went back in time just 2,000 years ago, landing in a jet plane and jumping out to say hello to the Romans they’d have thought us gods. So yes, we are looking into the depths of space, but do we know what we should be looking for? 

So I think life will be falling out of the trees all over, with every 20th to 50th sun (away from the galaxy core of course) having a planet with life. Intelligent life will be there as well, but we have to assume intelligent life is a quirk of nature, as life has been on earth for eon’s and it’s just been us so far. So evolution it would seem does not like big brains or we’d have furry neighbours eating banana’s fighting with the lizard next door over the state of their lawns. This has not happened, it’s just us I’m glad to say. So, planting my flag again, there will be lots of life out there but intelligent life will be rare. 

So before I head off to find PG's house, which sounds like a great place to be for Christmas, I like to finally consider the question posed. I don't think we're alone, that would just be silly. The problem is the distances involved, but we've come on a lot in the last 100yrs so never say never. The chances of us developing at around the same time as another alien race, high due to the number of planets/stars around. The chances of them being close to us, almost nil I think. Are super advanced aliens out there, I guess, space is vast enough for this to occur. Will we ever meet them, maybe - but more likley they'll have had their time and long since passed on like the dinosaurs before us. Or it could be Star Wars out there, aliens all over, who knows. A good question in my book and I think it will be lonely and cold out there, but we're not alone...


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## Vertigo (Dec 21, 2012)

Yes there are organic compounds out there in space but there is no evidence that they are either caused by life or likely to cause life. They might be useful material if life does get going but there is no evidence that they would actually assist in that genesis.

I'm afraid I have the same doubts about the basic assertions as Peter. In particular the first couple. I'm not sure where the 500 billion planets in the galaxy figure comes from; it feels like it is just plucked from thin air (space?).

The second figure of one in ten capable of supporting life seems even less likely. We have 8 planets (now Pluto has been relegated to dwarf - does your count of planets include dwarves?). Of those only one - Earth - appears capable of supporting life. So if our solar system is moderately typical in terms of numbers of planets then that would suggest that almost every star system in the galaxy should have one planet in its collection capable of supporting life. Sadly that's not how things are really looking as we begin to discover exoplanets.

Then, as Bowler points out, most of the stars in the galaxy and their associated planets are close in to the centre of the galaxy, where the concentration of stars means that all of those planets would be bathed in such intense radiation that it is considered highly unlikely that any kind of life could evolve. And please don't say that maybe there is some sort of life that can take (or even thrive in) those conditions. These sort of levels of radiation are likely to alter (mutate) the properties of inert matter (creating isotopes etc.) never mind what it would do to any molecule sufficiently complicated enough to be reliably and consistently self replicating (rather a necessity for life). I would add to bowler's points that further out than we are there is also very little chance. Further out the stars are much younger resulting in a gross lack of heavy elements. Without these rocky planets are unlikey to form and you would probably only have gas giants.

Then as far as communications go you really do have a big problem. Everyone seems to think that all our (and maybe their) radio and tv would be detectable in other systems. But actually our radio and tv broadcasts are estimated to be detectable out to only a very small distance (hardly beyond the limits of the solar system).



> Detection of broadband signals from Earth such as AM radio, FM radio, and television picture and sound would be extremely difficult even at a fraction of a light-year distant from the Sun. For example, a TV picture having 5 MHz of bandwidth and 5 MWatts of power could not be detected beyond the solar system even with a radio telescope with 100 times the sensitivity of the 305 meter diameter Arecibo telescope.


 
Not very promising! Of course a tight beamed signal such as a radar pulse would be detectable much further out; thousands of light years in fact. However how do you know where to point it. This is the dilemma facing SETI; even if some alien race is beaming signals out into space they are not exactly going to pick our system and only point them at us. Rather they are going to do much the same as SETI does with its listening and scan lots of different systems. The only problem is, what are the chances of us pointing our radio telescope at just the right point in the sky and at just the right time to catch a signal sent hundreds maybe thousands of years previously, and probably only beamed at us for a few hours at most? Sadly I think the answer is slim to negligible.


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## Gordian Knot (Dec 22, 2012)

Well, according to Universe Today:

The Milky Way has about 200 billion stars. The dwarf galaxies between us and the Andromeda Galaxy contain around 10 billion stars. The Andromeda galaxy is much more massive than our own and is estimated to have 1 trillion stars.

http://www.universetoday.com/24325/how-many-stars-are-in-galaxies/

As to the chance for life on a planet comparable to our own. Probably very, very good indeed. There has been life on Earth for almost as long as there has been an Earth! But how many Earth like planets are out there? That is the real question, one for which there is no clear answer at this time.

As to intelligent life. Chances to my way of thinking is that those chances are very slim. The earth has been around for 4 1/2 billion years, and far as we know we are the only intelligent species the planet has ever known. And we've been around a few million? Those are pretty dang long odds. The roll of the intelligence dice seems to be a very tiny one indeed.

Certainly not impossible odds though. There very likely exists other intelligent life out there. But, and this is the really BIG BUT. The chances of that intelligent life being alive right now, at the same or better development than we are right now, at a distance that we could communicate with at our level of development right now - those chances are miniscule.

A super civilization could have had its zenith a hundred years ago, and we wouldn't have had any way to become aware of them. Somewhere else, life could develop a hundred years from now to where we are now, and could possibly even pop up fairly near to us but who knows if we will still be around to talk to them.

The vastness of the cosmos and the huge time frame for which intelligence could have existed then vanished is so large that the chances are statistically near zero.

Which really stinks!


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## Dave (Dec 22, 2012)

> Given 500Billion planets in the galaxy,





> Do we know that to be an accurate figure?


That was the only assumption that is possibly accurate. Studies on extremely small fluctuations in light intensity from nearby stars is finding that almost all those looked at have planets, and not just one, but a similar number to our solar system in a similar variety of sizes. I think it is safe to assume now that this is in fact, the norm.

As for the other assumptions, there is no basis for them whatsoever.



Bowler1 said:


> It seems everywhere we go in space organic compounds have been found. This could just be our local area of space and it could be life from Earth infecting local space but I find that unlikely. The only other conclusion is that space is full of these organic compounds. That being the case the seeds of life must be everywhere.


Not the seeds, but the raw materials. It is still a step from organic compounds to life. The 'seed' would be to find viruses. Artificial cell membranes have been created in the lab - that was once thought to be difficult. Once you have self-replication, given mutation over enough time you can produce anything, just like the monkeys and a typewriter producing Shakespeare.

Though I agree that another civilisation being alive now and within a distance that we can contact looks increasingly unlikely, the more we search for one and find nothing.


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## megamaniac (Dec 23, 2012)

Peter Graham said:


> Do we know that to be an accurate figure?
> 
> Any evidence for that assertion?


 
No, we dont know any figure to be accurate; just guesses.

Just like if you have 1:175m odds of winning the PB $530m jackpot, and there are 320m people in the U.S., and if each lottery player buys $5, thus 32mx5 = 160m covering the odds... so, that's why we had 2 winning tickets.

Now given hundreds of billions of planets in just this galaxy, odds are good that atleast 1:1,000,000 will have life.


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## Dave (Dec 23, 2012)

Think of tossing a coin and calling heads or tails. The odds are 1 in 2 you will win. A lottery works in the same way, that you do at least have some chance, small though it may be, of winning.

You are not comparing like for like with life in the galaxy. There is no mathematical law that says that life _must_ exist, and so there may be zero chance. We still may be the only example of life. If it can actually be proven that life occurred spontaneously from self-replicating chemicals then that would be a different thing. A chemical reaction will occur under precise conditions, and the chances of those conditions being present can be measured and odds can be given. Abiogenesis is still merely a theory.

What you are proposing is better known as The Drake Equation. While the equation holds true any of those variables could still be zero.


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## TheTomG (Dec 23, 2012)

There is indeed a difference between knowledge and conjecture, even informed conjecture. The second is just a "best guess" and could of course be massively wide of the mark in either direction, no matter how well informed it is.


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## Gordian Knot (Dec 24, 2012)

There is no mathematical law that says life must exist? Aren't we life? I'm confused. Are you suggesting it happened here, but it is not possible for it to happen elsewhere?????


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## psychotick (Dec 24, 2012)

Hi,

From memory there are two hundred billion stars in our galaxy and coincidentally, two hundred billion galaxies. Some of those galaxies will have more stars, some less.

Next the planets? No idea of the true number, but it's highly unlikely that one in ten of them will be capable of supporting life, or at least life anything like we know it. You have to remember that the most common stars are red dwarfs of various types, and worse a large number of stars exist in groups of two or three or more. Alpha and Proxima Centauri for a start. Then of course there are white stars etc. Many of these stars will have planets, none of them will be anything like Earth. G type stars like our sun number at a guess one tenth or less of all stars.

So as for one in ten planets being capable of supporting life, I don't think so. At present we've discovered 854 exoplanets http://exoplanet.eu/ and there are only a couple that could be candidates for any form of life like ours.

Yes, given the sheer number of stars out there it is almost certain that there is other intelligent life out there, but the numbers are complete guesswork.

Cheers, Greg.


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## Vertigo (Dec 24, 2012)

Gordian Knot said:


> There is no mathematical law that says life must exist? Aren't we life? I'm confused. Are you suggesting it happened here, but it is not possible for it to happen elsewhere?????


 
No Dave's not suggesting that. He did *not* say there _*is*_ a rule saying other intelligent life *cannot* exist; of course that is possible. What he said is there is *no* rule saying intelligent life *is inevitable* and that does not say it is not possible. The fact remains that life has been around on Earth for over 3 billion years; in that time there have been billions of different forms of life come and gone and yet, so far, we are the only example of 'intelligent' life that has appeared, and we only evolved to our current levels of intelligence some 200,000 years ago. That means that in all that time intelligent life has only appeared once (that we know of) and has been present for less than 0.01% of the time life has been present on the planet (approx 3.6 billion years).

As the only hard example of data on life that we have, that represents pretty low odds for intelligent life. Not impossible, maybe, but certainly low.


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## RJM Corbet (Dec 24, 2012)

Exactly. At the risk of labouring the point, _Gordian Knot_, what's lost in these debates is the fact that the chance of life having spontaneously _originated_ (not evolved) is so vanishingly tiny that lottery comparisons don't come close. Google it: you'll find that the chance of life having originated spontaneously is something like one to all the atoms in the universe.

Yet it did.

From there, the evolution to intelligence is reasonably predictable, given enough time.

But that doesn't mean it's a given fact that just because the (finite) universe is so huge and so ancient, that life will have originated elsewhere too.

Perhaps life on earth was seeded from elsewhere. Perhaps life has spread throughout the universe, to other goldilocks locations like our own. But we shouldn't just EXPECT to find it ...


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## Bowler1 (Dec 25, 2012)

Dave said:


> Not the seeds, but the raw materials. It is still a step from organic compounds to life. The 'seed' would be to find viruses. Artificial cell membranes have been created in the lab - that was once thought to be difficult. Once you have self-replication, given mutation over enough time you can produce anything, just like the monkeys and a typewriter producing Shakespeare.


 
But the monkey only has to get it right once for life to take off. Eon's of time give the monkeys plenty of time to hone those typing skills.

We've only really being looking at our local stars for planets over the last 10 to 20 years, even being generous. So far we've only been able to find the big planets around stars because we're really only taking baby steps when exploring our local stars. So the truth is we don't know what's out there. I still think that life will be out there and be fairly common. Intelligent life is still the hard question, but we should have lots of room to explore if we ever get there, the neighbours fence will be a long way away - or so I think.


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## RJM Corbet (Dec 25, 2012)

Yes Bowler. Even the Spitzer telescope is very limited in it's ability to detect smaller (Earth size) planets. We can really still only detect the really big ones, just the fact that they're there, and then surmise conditions by their size, distance from their own star, etc.

We can't detect a spectrum signature, because we only know they're there because they block the light from their own sun as they pass in front of it.

It's not much to go on, yet amazing how much can be construed from the little information available.

I sometimes think we're like (very clever) fleas trying to understand the dog ...


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## Victoria Silverwolf (Dec 25, 2012)

RJM Corbet said:


> Exactly. At the risk of labouring the point, _Gordian Knot_, what's lost in these debates is the fact that the chance of life having spontaneously _originated_ (not evolved) is so vanishingly tiny that lottery comparisons don't come close. Google it: you'll find that the chance of life having originated spontaneously is something like one to all the atoms in the universe.


 
I have heard this claim made before, generally from those who support "intelligent design." From what I can tell, it is true only if you are calculating the odds against life spontaneously arising _in the exact chemical form as it did on Earth_. This is somewhat misleading.

As an analogy, consider a deck of cards, arranged at random. What are the odds that this _exact_ arrangement came about through random shuffling? The answer is 52! to one. This is about 8 followed by 67 zeroes to one; an unimaginably gigantic number. Yet, clearly, the cards must be in _some_ arrangement, even though _every_ arrangement is incredibly unlikely!

The way that substances came together when life arose on Earth was, in a similar way, unlikely beyond description; but they had to come together in _some_ way. Of the unimaginably many different ways they could have come together (and the lesser but still huge number, during the immense age of the Earth, that they actually _did_ come together), how many of them would lead to life? Nobody really knows, but I would tend to think that, even if the fraction of such arrangements is extremely small, that still leaves us with an extremely large number of ways that life could come about.

(If I sound confused, and even contradictory, it's because the vastness of the numbers we are dealing with are utterly mind-blowing!)

Anyway, here's a good article which explains this point much better than I could.

http://www.science20.com/stars_planets_life/calculating_odds_life_could_begin_chance


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## RJM Corbet (Dec 26, 2012)

Victoria Silverwolf said:


> ... As an analogy, consider a deck of cards, arranged at random. What are the odds that this _exact_ arrangement came about through random shuffling? The answer is 52! to one. This is about 8 followed by 67 zeroes to one; an unimaginably gigantic number. Yet, clearly, the cards must be in _some_ arrangement, even though _every_ arrangement is incredibly unlikely!
> 
> The way that substances came together when life arose on Earth was, in a similar way, unlikely beyond description; but they had to come together in _some_ way... even if the fraction of such arrangements is extremely small, that still leaves us with an extremely large number of ways that life could come about...



I don't know. Perhaps it's more like flipping a coin headsup 8 x 10/67 times in unbroken sequence, to create the requirements of life as defined.

Here's the Wiki definition of life. It's not a simple one-line definition ... _'life is a process, not a pure substance.'_

http://en.wikipedia.org/wiki/Life#Definitions

If all the little information-storing _pits_ on a common DVD disc were expanded to the size of a pinhead, the DVD would be 300Km in diameter -- covered with pinheads. Or look at the technology of the _LHC._ Our scientists are pretty smart. But even knowing what to aim for, without the element of chance, and with all the materials available ...


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## RJM Corbet (Dec 26, 2012)

Sorry for double posting, but before anyone jumps on me that Craig Venter has _created_ artificial life -- he himself denies it:

*The Craig Venter Institute maintains the term "synthetic bacterial cell" but they also clarify "...we do not consider this to be "creating life from scratch" but rather we are creating new life out of already existing life using synthetic DNA."*

From:

http://en.wikipedia.org/wiki/Synthetic_biology


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## Dave (Dec 26, 2012)

I think that is the problem here - unless and until we know how life began, and can have a clear definition of life, and a pathway from self-replicating chemicals to living thing - then we will go around in circles about this.

There are clay-minerals that can self-replicate but they are not life. Viruses can self-replicate and can change living cells to manufacture themselves, but they are not living themselves. We can create synthetic artificial cells but they are not living. It is very complicated.


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## Gordian Knot (Dec 27, 2012)

RJM Corbet said:


> Exactly. At the risk of labouring the point, _Gordian Knot_, what's lost in these debates is the fact that the chance of life having spontaneously _originated_ (not evolved) is so vanishingly tiny that lottery comparisons don't come close. Google it: you'll find that the chance of life having originated spontaneously is something like one to all the atoms in the universe.



More curiosity on my part. Since we have no idea how life originated here, how can someone make a determination that the chance for it originating elsewhere is vanishingly small?

I'm not clear how someone could make that statement when we don't know "how" life does get started. Here, or anywhere else.


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## Vertigo (Dec 27, 2012)

In fairness they can't, GK. The fact is that we do not have enough knowledge to make an accurate assessment of the probablities; we each might have our own beliefs as to what we think is most likely and, indeed, we can and do discuss those theories. 

But until we have more data they can never be more than that. For example, suppose in the future we have thoroughly explored all the star systems within a 100 light year radius of the solar system, and suppose we have found no life whatsover. Chances are people will start saying that we are alone. However our galaxy alone can encompass 2.5 million areas of space of that size and that is only in our own galaxy, so an area 100 light years in radius would still only be a very, very small sample (and a fairly low density one at that).

So the best we can do is try and figure out what the requirements for life are likely to be (and we only have our own example to draw on for that) and then try and figure how common those conditions are likely to be. With all the discoveries of new planets we are possibly _*just *_beginning to get some useful data for that calculation, however it is still very incomplete; we are still struggling to detect the smaller rocky planets.

End of the day the best we can do is say "based on the available data *I believe* that..."

By the way an interesting point that I came across in the book I'm reading at the moment is that maybe the rarest event in the genesis of life is not the first life but the first multicellular life. As Dave says there are quite a few self-replicating molecules and the polulation growth of a single celled organism is 'simply' a case of replicating exact clones of yourself. However when you have multicellular organisms the cells have to not only replicate but then they have to adjust their structure to a particular _and different_ task to other cells in the organism, possibly different even to the cell that it just divided from, yet in such a way that it continues to cooperate with all those other cells. That is in many ways a much bigger jump than the creation of the first self-replicating cell.


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## Bowler1 (Dec 27, 2012)

Vertigo said:


> By the way an interesting point that I came across in the book I'm reading at the moment is that maybe the rarest event in the genesis of life is not the first life but the first multicellular life. As Dave says there are quite a few self-replicating molecules and the polulation growth of a single celled organism is 'simply' a case of replicating exact clones of yourself. However when you have multicellular organisms the cells have to not only replicate but then they have to adjust their structure to a particular _and different_ task to other cells in the organism, possibly different even to the cell that it just divided from, yet in such a way that it continues to cooperate with all those other cells. That is in many ways a much bigger jump than the creation of the first self-replicating cell.


 
Working as a team is a clear advantage when compared to going it alone. Sponges and slime are good examples where specialist functions don't really exsist in the cells. So simple banding together to occupy space against the competition, I think would happen quickly. The rest would be simple evolution. So once life starts it spreads bacteria  like and grows. I think the first baby step is the killer step (getting life started), after that the baby stampedes away.... Or so I think anyway.


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## paranoid marvin (Dec 27, 2012)

As Eric Idle once so aptly put it:

*...pray that there's intelligent life somewhere up in space,
'Cause there's bugger all down here on Earth.*


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## Vertigo (Dec 27, 2012)

Bowler1 said:


> Working as a team is a clear advantage when compared to going it alone. Sponges and slime are good examples where specialist functions don't really exsist in the cells. So simple banding together to occupy space against the competition, I think would happen quickly. [Agree with that...] The rest would be simple evolution. [...but disagree with this] So once life starts it spreads bacteria  like and grows. I think the first baby step is the killer step (getting life started), after that the baby stampedes away.... Or so I think anyway.


 
There is a huge difference between a cell splitting into two identical cells and one that splits into different cells that then integrate their different behaviours. I'm not alone in thinking this is an exceptionally big hurdle; I have come across this view being expressed a number of times and it does make sense to me. It seems to me that basic single organism life is really not a lot more than a complex form of self replicating molecules. And we do have other examples of those. However getting a bunch of related but different cells to cooperate and form a consistently repeatable structure, now that seems like a much step to me.

However, I'm no expert in the evolution of life, so them's just my thoughts 

Oh and I'd definitely echo PM's quote from Mr. Idle!


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## Bowler1 (Dec 27, 2012)

Hell, I don't know either, Vertigo. Competition would be the key or some external extinction stage to force the next big step on life. These seem to appear on a regular basis, but I guess that's not really a recipe for success. Once past that point, easy or hard, life should trot on happily.


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## mosaix (Dec 28, 2012)

Vertigo said:


> There is a huge difference between a cell splitting into two identical cells and one that splits into different cells that then integrate their different behaviours.



I believe there is an intermediate stage, Vertigo, where cells 'co-operate' rather than 'integrate' to form an organism. If my memory serves me correctly the jellyfish is an example.


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## Vertigo (Dec 28, 2012)

That wouldn't surprise me, Mosaix, and it would be logical that the process would move forward in small steps. But no matter how small the steps I still think the progression from single to multicellular life is of more significance than the initial creation of reproducing cells. I think the timeline bears this out as well. We have 'only' had around one billion years of multicellular life on Earth, but before that there were around two and a half billion years where there was only single celled life and that life first formed only a few hundred _million_ years after the Earth formed. So pretty much as soon as the Earth had cooled enough, after a few hundred _million_ years, the first single celled life appears and then it takes two and a half _billion_ years to get to multicellular life.

After that, as Bowler says, life pretty much tore away!


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## RJM Corbet (Dec 28, 2012)

Bowler1 said:


> Hell, I don't know either, Vertigo. Competition would be the key or some external extinction stage to force the next big step on life. These seem to appear on a regular basis, but I guess that's not really a recipe for success. Once past that point, easy or hard, life should trot on happily.



As _mosaix_ says, in combination with survival of the strongest, comes it's opposite: co-operation. Symbiosis. Like the Portuguese man-of-war, where a bunch of jellyfish come together to form an organism, some act as the stomach, others as the 'eye' and so on. Like bees. or ants, or like a human army. The whole becomes greater than the sum of the parts: the herd instinct, both to enhance the chances for individual survival, and to promote the species.

And the initial realization of the value of the power of 'togetherness' would probably first come from the most basic act of 'life': procreation. One and one makes three. Or perhaps thirteen, if you're a bunny ...


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## Bowler1 (Dec 29, 2012)

To be fair, Vertigo, the only example we have of life is Earth like life. It could be we were slow getting it on; the dunce of single cell development. 

Not likely, but I enjoying being a stubborn git.


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## Vertigo (Dec 30, 2012)

That's always going to be the problem with these discussions. Our available data sample of 1 is really too small to do anything other than speculate. But we can sure do that


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## Harpo (Dec 30, 2012)

The 1 intelligent race that we will have contact with are outnumbered 100-to-1 by those we'll become aware of but never have any contact with, and those in turn will be outnumbered 100-to-1 by the unintelligent races we'll contact, which themselves will be outnumbered 100-to-1 by those we'll find evidence of only after they've died out, and those in turn will be outnumbered 100-to-1 by those that'll developed after we have died out ourselves, and so froth.....


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## Bowler1 (Dec 30, 2012)

Candles in the darkness, Harpo.


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## paranoid marvin (Dec 30, 2012)

If they have any sense , alien races will steer well clear of us.


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## Mirannan (Jan 23, 2013)

Life-bearing planets and moons per solar system is a fairly wild estimate. The number of planetary systems looks to be around 60% or so, from the admittedly small amount of evidence we have - at least for systems likely to be able to support life otherwise. (Blue giants probably don't have planets, but they won't support life anyway - not enough time.)

Planetary systems with planets in the life zone is a different matter. It appears that, of the exoplanets so far discovered, most of them are far too close to the star - but that might be observational bias.

For the system we have some knowledge about, we have at least one life-bearing world - obviously! However, there are at least two more and perhaps up to five more, at least one of which might have two completely independent and wildly different life systems.

Details, not including Earth:

Mars: Maybe bacteria deep underground. There is precedent for this on Earth, BTW.

Europa: 60km deep liquid water ocean, almost certainly with vulcanism. By analogy with deep-ocean ecosystems on Earth powered by hydrogen sulphide and the like, a possibility. Possibly complex life.

Ganymede: Some evidence of an ocean like Europa's.

Enceladus: Underwater lakes at the very least, confirmed by water vulcanism. Probably conventional vulcanism deeper down.

Titan: The interesting one. Titan has cryovolcanoes, so there is probably liquid water beneath the surface and therefore possibly similar to Europa. In addition, there is a complete hydrological cycle on the surface using liquid methane/ethane mix as the fluid; there is some possibility of seriously odd biochemistry using liquid methane as a medium and completely different chemistry from Earth's. Doing experiments on pre-biological chemistry at those temperatures is very difficult for us. Temperature is a problem; so is the fact that liquid methane is actually rather dangerous - explosion hazard.

That makes five possibles right here in Sol system. Admittedly, two or three of them are a little speculative, and it's pretty certain there are no technological civilisations other than us. Multicellular or similarly complex forms are, however, known on at least one (no s**t, Sherlock!) and possible on as many as three of them.


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