How rare is life in the universe?

[swivel]

I am not a fan of the Drake equation, which Carl Sagan was so fond of. I think you can't have an equation where every variable is a guess pulled from thin air, with absolutely no basis. And I also think that the Drake equation misses way too many small (and rare) features of our solar system.

I am also not a fan of the theistic argument that we are the only ones, and the entire universe was created for just us.

Which leaves me with not much of an opinion at all. Which is why I ask the forum... which direction do you lean? Towards millions of intelligent organisms all listening in the dark from messages from each other... or do you think we are all alone in the universe right now.

If I had to answer, I would say that we are not along, but I would be surprised (with an awareness of how vast our universe is, and how populated with other systems) if there are a dozen other sentient species in the history of the universe. The fact that we are one of them does nothing to impress me. Any sentient species is going to wonder at the lucky splendor of their enviorns and marvel at how fortunate they are, and how alone or in company they must be (depending on their faith).

 

[madanthonywayne]

I can't believe that in the vastness of the universe there aren't many, many worlds that harbor life. Some fraction of them must have intellegent life.

But the very vastness that makes other intellegent species all but inevitable, keeps us seperated. Unless someone developes FTL, if such a thing is possible, we may never meet our interstellar neighboors.

I believe that FTL must be possible. Why make such a big universe if there's no way to get around in it?

 

[swivel]

I can't believe that in the vastness of the universe there aren't many, many worlds that harbor life. Some fraction of them must have intellegent life.

But the very vastness that makes other intellegent species all but inevitable, keeps us seperated. Unless someone developes FTL, if such a thing is possible, we may never meet our interstellar neighboors.

I believe that FTL must be possible. Why make such a big universe if there's no way to get around in it?

You assume:

1. That the universe was created.
2. It was logically designed.
3. Part of that design is to grant the various inhabitants access to most of what is out there.

That is a lot to assume, and 2 and 3 seem to contradict each other when you look around.



I think the Drake equation misses a few biggies.

Jupiter is a huge factor in having intelligent life. A large number of star systems are binary. Ours nearly was, Jupiter has almost enough mass to "turn on" but not quite enough. What it did do, though, was act like a scrubber, with its enormous gravitational influence, sucking up and deflecting the planet-killers that would have made an eternal torment to the process which led to us.

The moon is bizarre. Such a large satellite for such a small planet. Its capture was a very chance occurance (probably due to a glancing impact of two protoplanets). I think we needed a large satellite for intelligent life to form. It aided Jupiter's cause, and it also gave us the severe tides that would have led to organisms leading the dual life, that eventually gave rise to mammals. I think only terestially-based lifeforms are going to wield technology. If only for the limitations of the tech itself, such as ore production.

The universe is changing in chemical structure. Each set of stars is going to be composed of heavier and heavier elements. Which means each set of planets will be as well. It is probably true that there is a window for intelligent life within the lifespan of the universe. The Drake equation ignores this obvious fact as well.

The Drake equation also counts stars, ignoring the fact that the massive number of inner-galactic stars would be inhospitable to lifeforms. The supermassive blackholes, the radiation, the collisions, the debris.... Our location on an outer rim 3/4 of the way to nowhere is our saving grace.

These are just the few I can think of with my own tiny brain, no telling how many other factors the Drake equation misses. I bet quite a dozen more.

 

[madanthonywayne]

You assume:

1. That the universe was created.
2. It was logically designed.
3. Part of that design is to grant the various inhabitants access to most of what is out there.

Can't deny or refute what you say, except for this. A whole universe with only one intellegent species, or a universe teeming with intellegence that can't get at each other, offends my sence of asthetics. It just doesn't jibe.

The above applies whether the universe was created or is simply a random occurence. Now if the universe was created. If their is a God, and the only intellegent life in all the infinite universe resides here on earth; it would be like one of those cartoons where a tree goes into a factory and is cut down to nothing but a toothpick!

 

[Fraggle Rocker]

I think it's reasonable to say that it's not impossible that life exists elsewhere in the universe. I think it's also reasonable to say that it's not impossible that life does not exist anywhere else in the universe. Beyond that is pure conjecture.

This is the fundamental statement upon which all science is based: "I don't know."

 

[swivel]

This is the fundamental statement upon which all science is based: "I don't know."

Brilliant. I love that.

I guess I'm just into the manipulation of the famous Drake equation based on knowledge of biology and planetary astronomy. Just like I exercise only to look good, not because I'm actually going to use the muscle for anything in particular, I also love discussing things for which there is no easy answer.

I'm like the bastard son of Sisyphus and Narcissus! (if that were somehow biologically and mythologically possible)

 

[Pete]

Vey much agnostic on this issue. The idea of ETI is interesting in the same way that God or gods are interesting.

I think that until we have some kind interaction, it's irrelevant to me whether they exist or not.

 

[superluminal]

Based on some of our thoughts here on how relatively early and robustly life arose on the earth, under what we might today deem as utterly inhospitable conditions, I'd say it was highly likely that life of some form (probably microbial) was fairly abundant.

 

[madanthonywayne]

Based on some of our thoughts here on how relatively early and robustly life arose on the earth, under what we might today deem as utterly inhospitable conditions, I'd say it was highly likely that life of some form (probably microbial) was fairly abundant.

I'd be willing to bet that we'll find life elsewhere in this solar system. Be it on the moons or Jupiter, or in underground caverns on Mars.

 

[swivel]

I'd be willing to bet that we'll find life elsewhere in this solar system. Be it on the moons or Jupiter, or in underground caverns on Mars.

Agree. I was sloppy and should have specified "Intelligent Life". My species-specific hubris and laziness got the best of me. That is why I criticized the Drake equation only in ways that affected the likelyhood of technology-weilding organisms to evolve.

I'm with you in assuming that anyplace warm and wet probably has life of some sort.

 

[leopold]

The idea of ETI is interesting in the same way that God or gods are interesting.

i heard an interesting quote today in a movie i was watching, it went like this:
' humanity exists and god exists, the question is who created who? "

 

[Boss Foxx]

With an infinite amount of space out there, there's seemingly an infinite number of possibilities for life on other planets. That being said, "life" can be a relatively vague or broad term. I'm certainly not inclined to think there's an intelligent life out there plucking hillbillies off of backroads in Arkansas to conduct anal probes however.

 

[Theoryofrelativity]

If I had to answer, I would say that we are not alone, but I would be surprised (with an awareness of how vast our universe is, and how populated with other systems) if there are a dozen other sentient species in the history of the universe.

So this non Earthly sentient being, any reason why it didn't exist before us and be consdierably more evolved?

Any reason why a more advanced species couldn't be viewing our activities and occassionally interefering?

Hmmmmmmm you will reply no as it suits you not to consider the ramifications of your 'belief' that there is sentient life beyond earth.

NO one that believes life exists elesewhere can deny the possibility that what we are going to do in our distant future (which is attempt to terraform a planet and seed it with life) has already been done.

 

[spuriousmonkey]

NO one that believes life exists elesewhere can deny the possibility that what we are going to do in our distant future (which is attempt to terraform a planet and seed it with life) has already been done.

Makes no sense.

 

[Sarkus]

So this non Earthly sentient being, any reason why it didn't exist before us and be consdierably more evolved?

Please try and avoid the idea of something being "more evolved". They can be more advanced in certain things - but evolution is not a matter of advancement or not - it is a matter of fitness for the environment - and you can not get "more evolved" than any lifeform that survives in its environment.

Any reason why a more advanced species couldn't be viewing our activities and occassionally interefering?

Nope.
It's a possibility.
But so is the FSM.

has already been done.[/B]

Deny the possibility? Of course not - it is indeed POSSIBLE. A lot of things are possible - but that doesn't mean they have happened - or will happen - or won't happen.

 

[Theoryofrelativity]

Deny the possibility? Of course not - it is indeed POSSIBLE. .

Then we are in agreement

 

[imaplanck.]

Please try and avoid the idea of something being "more evolved". They can be more advanced in certain things - but evolution is not a matter of advancement or not - it is a matter of fitness for the environment - and you can not get "more evolved" than any lifeform that survives in its environment.
.

It is most common for species to carry on evolving even without environment change to necessitate. i.e. there is a constant race to out-do your fellow species and grab a bigger share of the food resouces and thus more efficient means to procure this are evolved. Evolution never stops when there is equilibrium with the environment- if a more efficent way to act on the same environment is possible. You can indeed get more evolved than a lifeform that survives its environment.

 

[Dinosaur]

I have made at least one post similar to the following to another thread or threads.

Instead of just expressing opinions, why not try an analytical approach to the subject of intelligent life elsewhere in the universe? The only evidence on which to base an analysis is the history of the Earth and our knowledge of how solar systems form.

When was it first possible for life to exist somewhere in the universe? Current theories indicate that the early universe contained almost no elements other than hydrogen & helium. Our current knowledge of stellar evolution indicates that stars “cook” elements like carbon, oxygen, nitrogen, iron, et cetera, and spew them into space during their death throws when cataclysmic explosions (nova) occur.

I think it takes about a billion years for a gaseous cloud to gravitationally collapse and form a solar system. Ordinary stars last for 5-10 billion years. Massive stars last for about a billion years before a nova event spews heavy elements into interstellar space. Extremely massive stars can burn out sooner.

The first or second generation solar systems did not have enough heavy elements for life to form. I do not know much about the time scales involved, but would guess that life of any kind was not possible in the first 2-3 billions years of the universe’s existence, and perhaps not likely in the first 5-6 billion years.

On Earth, intelligent life did not appear for about 4.6 Billion years after the formation of the solar system. Various estimates of the age of the universe run from 8 to 20 billion years, with 12-14 being a recent estimate. At any rate, it looks reasonable to assume that intelligent life did not exist for the first 7-10 billion years or so (2-3 billions years to “cook” the necessary ingredients and another 5-7 billion years for solar system formation and evolution). For 50-80% of the life of the universe, intelligent life probably did not exist.

Next, consider the history of our planet, which contains the only evidence we have for the existence of life in general and for intelligent life in particular. Imagine compressing the history of the Solar System into 1000 days. This is easier than comparing billions, hundreds of millions, et cetera.

Solar system formed -------1000 ---- days ago (4.6 billion years)
First life appears ----------- 804 ---- days ago (3.7 billion years)
Dinosaurs appear ------------ 54 ----days ago (250 million years)
Dinosaurs disappear --------- 14 ---- days ago (65 million years)
First man-like ape shows up --10 ---- hours ago (2 million years)
Early Homo Sapiens ---------- 2 ---- hours ago (500,000 years)
Modern man appears -------- 40 ---- minutes ago (130,000 years)
Beginnings of civilization ------ 3 ---- minutes ago (10,000 years)
Modern technology ----------- 2 ---- seconds ago (100 years)

I do not claim that the above are precise values, but they are fair approximations. There is controversy over most of these numbers, so precision is not possible.

Note that life appeared almost as soon as it was possible for it to exist. For the first “100-150 days” or more, conditions were too hostile for life to evolve. This suggests that life probably occurs whenever/wherever conditions are suitable. The above makes me optimistic about the existence of some kind of life elsewhere in the universe. I would expect life to exist in many places, and perhaps to be a common phenomenon. .

Note that dinosaurs existed for a long time and disappeared without evolving what we would call intelligence. Furthermore, it is believed (with fairly good evidence) that they were wiped out by a freak accident, not because they were an unsuccessful species. This suggests that the evolution of intelligent life is not necessary for a complex and successful life form.

Note how long it took for something vaguely man-like to appear. This suggests that intelligent life might be a lucky fluke. It certainly suggests that intelligent life is much rarer than life in general.

While I believe that intelligent life exists elsewhere, I consider it possible that none exists. I would not be surprised to learn that none exists elsewhere in our galaxy.

The talk about how the vast number of stars encourages optimism about the existence of life. Note that in our Solar System, there is a narrow habitable zone. Mars and Venus are at or likely beyond the limits. A galaxy also has a habitable zone. Closer to the center, radiation and rapid stellar motion make the environment too hostile for life. Farther from the center, the interstellar gas is not rich enough in heavy elements. Our Solar System is at a fortuitous distance from galactic center. While it seems likely that life exists elsewhere in our galaxy, we might be the only planet with intelligent life in this galaxy.

 

[swivel]

Dino:

Great, great post. I agree with almost everything you say. Very refreshing read. Nice to see some of my list on yours as well.

 

[Mr Anonymous]

I must confess, I'm not exactly a great fan of Drake myself. A snap shot of life here on this planet informs us only of the what may possibly have happened here, on this world. It shows shows us that life can exist where ever it can, but as to the evolution of Intelligent Life demonstrates equally that even amongst other species of hominids, life such as ourselves was a one off.

There were other species of Human. They didn't go the way our species did. Even with the development of larger brains and having been around longer than ourselves - thick as two short planks the lot of them in comparison to Modern Humans.

Evolution doesn't work with either design or intent in mind - much as with everyday life, Evolution only appears wise in retrospect and only in the minds of a species such as ourselves smart enough to discern the underlying principal in the first place. Evolution is reactive, not proactive in the slightest. One can no more predict its exact course beforehand than one can predict the exact path a single drop of water will take down the face of a pane of glass.

One can guess. One can anticipate. On can not know.

When it comes to speculation regarding Intelligent Life such as our own existing elsewhere out there in the Galaxy, one may as well ask - "How many fairies can dance on the head of a pin?"

As many as one likes, or as few as one likes, depending on whether or not one believes in such things as fairies and the existence of pinheads to dance upon.

That we exist remains beyond question. This says absolutely nothing whatsoever regarding the evolution of life on a single planet in the Universe other than this we find ourselves upon. If I recollect correctly, Drake pegs the number of advanced civilisations existing out there in the Galaxy alone at being something in the region of 10,000 or so. Actually quite conservative when you consider the sorts of numbers involved.

What criteria justify that conclusion though?

Nothing contained in Drake dictates whatsoever the exact nature of catastrophe that will be visited upon life on so much as a single world as likelihood may dictate, including this one. Drake takes into account precisely nothing regarding when in the evolution of these extraterrestrial life forms such calamity as will shape their subsequent development will occur. One can't even look at life on the one biosphere in the Galaxy we do know exists for an absolute fact and predict what will happen over the course of time to the forms of life one see's in the present day - we can anticipate apparent trends, but what we cannot predict is precisely when the next meteorite will fall nor in predicting at all predict accurately precisely in which progressive shift in global environment such consequences will occur.

It is these forces, random, arbitrary, catastrophic which fix the eventual course life will take - when and at what point.

Drake doesn't take any of these factors into account, because it can't. Nobody and nothing can. Considering the notion of life in general as an ongoing process occurring elsewhere in the Galaxy, itself, remains not in the slightest an unreasonable proposition - but to expect the likelihood of that process yielding results similar to those which occurred on our world is to either expect:

a: That in starting exactly similar climatic, geological and astronomical catastrophes remains in some way predetermined to occur at exactly the same points in that evolutionary development as occurred here on this world, or else:

b: Some mechanism exists governing the determination of Evolutionary process towards distinct and certain outcomes.

The likelihood of a remaining true buck the odds astronomically. As to the notion of b existing at all - it remains a presumption not in anyway borne out by observable fact.

Drake, frankly, has never seriously thought the proposition through. That however never prevent anyone else in the slightest from simply giving it a go....