Is there life in the universe, and if so has it visited Earth?

[arildno]

Are you hoping someone will beg you to share your wisdom? Or do you just have a whim to poop on an otherwise perfectly good discussion?

A discussion that at the outset respects the Drake equation as something more than worthless is, quite simply, not a "perfectly good discussion".

And, it is worthless, because most of the parameters involved in it is indeterminable (at present).

 

[arildno]

I agree; our existence might be against all odds, however there is no evidence to suggest that this is true. Also, since there is no reason to believe that we are special, it is entirely possible that intelligent life is nearly as common as planets.

If we randomly select a grain of sand on the beach, is it more logical to expect that grain of sand to be unique, or typical. Does our observation of that grain change the odds? Were the odds for intelligent life on Earth different before we [humans] came to be? Unless we can cite reasons why we are unique, it seems to me that our very existence is evidence that life is common. Again, the only hard evidence for the odds is measured as 1:1, for intelligent life on earth-like planets.

Since the fact that we are alive means that the conditions for life necessarily must be present in our case, HOWEVER RARELY FULFILLED those conditions are, the example of ourselves gives us no clue whatsoever as to the prevalence of those conditions in the universe as such.

 

[Ivan Seeking]

Odds for any planet to be an Earth-like planet;, based on the evidence - 1:9. Correct? And we hope to find life on Europa - a moon, not a planet. So it seems that we also have to include moons in the calculations.

Or should we assume that we are a fluke given no evidence that our system is unique? I don't see the logic in that. Again, it seems to me that what we do know suggests that life may be very common.

 

[arildno]

1:9 is not correct. We have found several other planets as well, none of which are Earthlike.

 

[Ivan Seeking]

Can we detect earth-like planets yet?

 

[arildno]

By occultations perhaps, I dunno.

 

[Ivan Seeking]

I don't think we're quite there yet. The last the I saw, we can only detect relatively large planets, like Jupiter. And I recall the comment being made that this [finding Jupiters] is a very good sign because large planets make life on smaller planets possible by clearing the system. So finding big planets bodes well for life.

 

[arildno]

That I happen to share the same sentiment as you in believing that there are lots and lots of planets out there with life, I'm quite simply stating that we cannot logically extrapolate from a single instance we know of to the probability of its universal occurrence.

 

[Ivan Seeking]

That I happen to share the same sentiment as you in believing that there are lots and lots of planets out there with life, I'm quite simply stating that we cannot logically extrapolate from a single instance we know of to the probability of its universal occurrence.

I realize that. Perhaps I misstated things a bit. My point is that so far there is no evidence to back the agument that life is likely rare. I think we should expect that life is common based on what we know today.

edit: Or, maybe it would be better to say that there is more reason to expect life than not.

Also, with our one example of our solar system, let's not forget about the water on Mars.

 

[DaveC426913]

A discussion that at the outset respects the Drake equation as something more than worthless is, quite simply, not a "perfectly good discussion".

For one, so good of you to join us. For two, you're using circular logic; the discussion is perfectly good until someone steps up and shows why it isn't.

The Drake equation may not be rigorously scientific, granted, but that doesn't make it worthless.

It does not attempt to provide an answer, it attempts to give structure to our educated guesses. Some are more education, some are more guess. But the fact is, we DO know how many stars there are our galaxy, and we are starting to get a pretty good idea of how many of those stars have planetary systems, and we can consider each variable in turn, with increasing speculation on hte way down.

But it is still better at helping us weigh our odds than "somewhere between 1 and 1 billion".

 

[Ivan Seeking]

Of course, as Vanesch was pointing out, this also boils down to the question of the source of life. Is it all in the odds - a one in a trillion chance - or is life raining down from the heavens on comets or other heavenly bodies, in our own primordial past? In our crudest form were we ETs? Or, could life be enevitable given enough time, the correct chemistry, and a source of energy? Also, might there be something else that drives life into existence wherever possible?

 

[DaveC426913]

When I break it down and ask myself about the very beginnings, where amino acids first began forming proteins, it seems to me (irrationally) that, as long as you have the key ingredients, it's a high probability.

key ingredients:
- liquid water (and, by logical induction, energy, usually solar, but also, apparently, electrical)
- organic compounds
- time
An abundance of each of the above.


I guess that abundance thing can't be underestimated. Small or seasonal puddles (as opposed to oceans) would vastly retard the formation of life.

Can anyone think of any other requirements?

 

[fournier17]

When I break it down and ask myself about the very beginnings, where amino acids first began forming proteins, it seems to me (irrationally) that, as long as you have the key ingredients, it's a high probability.

key ingredients:
- liquid water (and, by logical induction, energy, usually solar, but also, apparently, electrical)
- organic compounds
- time
An abundance of each of the above.


I guess that abundance thing can't be underestimated. Small or seasonal puddles (as opposed to oceans) would vastly retard the formation of life.

Can anyone think of any other requirements?

I just learned about chemical evolution in my cell and molecular biology class. Basically it is believed that Earth's ancient atmosphere, contained inorganic compounds such as nitrogen gas, carbon dioxide, water, hydrogen gas, ammonia, and methane. When you apply electricity to these inorganic compounds in a container, you spontaneously get organic compounds, even amino acids. When you add clay into the picture, which there was a lot of in early earth, scientist have seen the spontaneous synthesis of larger molecules like protiens, and small strands of RNA and DNA. The fact that you can get RNA from having the conditions that were believed to be present in early Earth, is AMAZING because it is believed that RNA was the first self replicating molecule, which gave rise to biological evolution. Now if scientist can create organic molecules from inorganic compounds during an experiment, its going to happen in other parts of the universe that has the right conditions

What I believe is needed for life to evolve is:
1.) Inorganic compounds listed above
2.) A source of energy
3.) Water is essential
4.) And a surface
5.) The planet that has potential for evolution, has to be within a certain range of a star.
6.) A large amount of time in between catastrophic events like asteriod strikes. This is were huge planets like Jupiter come into play. It is believed that Jupiter deflected a lot of asteriod strikes which gave life on Earth time to evolve. I think if the Asteriod that took out the dinosaurs didnt strike earth, this planet would have evolved a reptellian intelligent species, or maybe even a bird like intelligent species. If it wasnt for that perticular asteriod strike that took out the dinosaurs, we would not be here today.

 

[Ivan Seeking]

NASA scientists today announced the creation of amino acids, critical for life, in an environment that mimics deep space. The research will be published in the March 28 [2002] issue of the journal Nature.

In a laboratory at NASA Ames Research Center in California's Silicon Valley, the team of astrobiologists shone ultraviolet light on deep-space-like "ices," simulating conditions that are commonplace in interstellar space. Deep-space ice is common water ice laced with simple molecules. The team subsequently discovered amino acids, molecules present in, and essential for, life on Earth.

"This finding may shed light on the origin of life itself," said Dr. Max Bernstein, the first author and chemist at NASA Ames and the Search for Extraterrestrial Intelligence (SETI) Institute. "We found that amino acids can be made in the dense interstellar clouds where planetary systems and stars are made. Our experiments suggest that amino acids should be everywhere, wherever there are stars and planets." [continued]

http://web99.arc.nasa.gov/~astrochm/pr.html
The paper
http://www.astrochem.org/PDF/Bernsteinetal2002.pdf
More reading
http://web99.arc.nasa.gov/~astrochm/reading.html

Also, in addition to Mars and Europa, we need to mention the moon Titan as another candidate in our own solar system that might be capable of supporting life.

 

[arildno]

Also, with our one example of our solar system, let's not forget about the water on Mars.

That is, indeed, a very important find.
Even more exciting, though, will it be to explore Europa.

And, as it happens, we may not need to travel that far to see if life can subsist in water beneath a perennial layer of ice:
There exist buried lakes on Antarctica, it would be thrilling to find out if there is life in them.

 

[Azael]

When you add clay into the picture, which there was a lot of in early earth, scientist have seen the spontaneous synthesis of larger molecules like protiens, and small strands of RNA and DNA. The fact that you can get RNA from having the conditions that were believed to be present in early Earth, is AMAZING because it is believed that RNA was the first self replicating molecule, which gave rise to biological evolution.

Has the spontaneous formation of RNA really been observed or is just a hypothesis that it could happen that way?

 

[Schrodinger's Dog]

Can we detect earth-like planets yet?

Interferometers are meant to be able to detect the wavelength of light (such as the green of clorophyl) That when you filter out the vast light of the sun could indicate life, but there aren't any big enough to do this yet AFAIK.

 

[SqrachMasda]

there should be
i can't even imagine a 4th dimension
and dolphins don't seem to recognize out existence

haha
pretty much if there is something else
it may be right in front of us, or watching us and know everything about us
and we have no clue about it

 

[DaveC426913]

What I believe is needed for life to evolve is:
1.) Inorganic compounds listed above
2.) A source of energy
3.) Water is essential
4.) And a surface
5.) The planet that has potential for evolution, has to be within a certain range of a star.
6.) A large amount of time in between catastrophic events like asteriod strikes.

1] Unless I'm mistaken, CO2 and methane are both organic compounds.

2]
IMO, you're over-complicating it the requirements.
- For water to be liquid, there must be enough energy to make it so. Sufficuent energy is a given.
- No surface is needed. Oceans work nicely.
- The range from the parent star is covered under the "liquid water" requirement. It is not in-and-of-itself a requirement.
- I don't think a large amount of time betwwen catastrophes is a requirement. We're just talking about the origin of life for now, not the evolution of complex organisms. I doubt the biggest asteroid could wipe out ocean life across a planet.

 

[fournier17]

Has the spontaneous formation of RNA really been observed or is just a hypothesis that it could happen that way?

Follow up experiments of the Urey and Miller experiment, were conducted with clay added into the mix of gases. RNA did polymerize spontaneously, but only in the presence of specific clay. In the presence of certain minerals, amino acids formed at least 50 monomer protiens. Some of the protiens that formed had catalytic activity such as ATPase, catalase, and perixodase.

 

[imaplanck]

The way I see it, is even if we even get to plug actual figures into the drake equation: The distances will in all likelihood be too restrictive for us too ever be able to reach the percentage of life that has reached technological civilization, and the reverse is also true.

 

[Ivan Seeking]

I agree; our existence might be against all odds, however there is no evidence to suggest that this is true. Also, since there is no reason to believe that we are special, it is entirely possible that intelligent life is nearly as common as planets.

If we randomly select a grain of sand on the beach, is it more logical to expect that grain of sand to be unique, or typical. Does our observation of that grain change the odds? Were the odds for intelligent life on Earth different before we [humans] came to be? Unless we can cite reasons why we are unique, it seems to me that our very existence is evidence that life is common. Again, the only hard evidence for the odds is measured as 1:1, for intelligent life on earth-like planets.

I wanted to clarify what I meant here a bit: As far as we know, we earthlings are unique or could be a rare event, but most likely, we couldn't possibly know otherwise as yet. By "unique" I am referring to our solar system, our part of the galaxy, the chemistry of our sun and the planets, etc. In this sense it appears that we may be a typical system with no particularly notable features. In this sense, considering our system may be like considering any other typical system. However, the selection of our system for consideration is certainly not random.

 

[imaplanck]

As a UFO believer, how do you feel about the upcoming interferometry missions and other scientific searches for life?
Are they just a complete waste of time to you, seeing as a few retired pilots (with a interest in making a few bucks) have reinforced your fantasy that Aliens have visited earth?

 

[DaveC426913]

That seems a bit harsh.

 

[fournier17]

1] Unless I'm mistaken, CO2 and methane are both organic compounds.QUOTE]

CO2 is inorganic carbon compound, and methane is an organic compound. However, the vast majority of the gases, which were believed to have composed the Earth's early atmosphere, were inorganic compounds. These inorganic compounds were needed for chemical evolution to occur, which gave rise to the organic building blocks that make up the macromolecules of the cell. Earth did not start off with organic molecules such as nucleotides, or sugars. However after reading an article linked to by Ivan Seeking, it seems that our planet may have been seeded with amino acids. Amino acids alone arent enough though for the evolution of life. You would still need chemical evolution to provide the Earth with sugars, nucleotides, and lipids for the biological evolution of life.

2]
IMO, you're over-complicating it the requirements.
- For water to be liquid, there must be enough energy to make it so. Sufficuent energy is a given.QUOTE]

-The formation of life is like a cooking recipe. If you want to talk about the ingredients and steps needed for the formation of life, its best to use as much detail as possible.
We should consider energy and the sources of energy. Just because water is liquid does not mean that there is enough energy for many of the reactions that preceded biological evolution to occur. If only the minimal amount of energy required by water to be in a liquid phase was present, the reactions that took place in early Earth would have occurred very slowly. Water in early Earth was bombarded by ionizing radiation which provided energy for a lot of the reactions, since there wasnt very much ozone in our atmosphere at that time. In todays earth, which has abundant amounts of liquid water, the rate of the reactions that occurred in the past, would occur today at an almost infinitly smaller rate. This is due to almost all of the high energy radiation being absorbed by the ozone layer.

- No surface is needed. Oceans work nicely.QUOTE]

-What does the ocean rest on top of? A surface is needed. Your not going to see biological evolution in gaseous planets.

- The range from the parent star is covered under the "liquid water" requirement. It is not in-and-of-itself a requirement.QUOTE]

-The range of the planet to a parent star is important, if a planet is to close, it would be like Venus, which would be to hot for life, to far and its to cold.

- I don't think a large amount of time betwwen catastrophes is a requirement. We're just talking about the origin of life for now, not the evolution of complex organisms. I doubt the biggest asteroid could wipe out ocean life across a planet. QUOTE]

Life needs a stable environment in order to start. If there is continuous bombardment of asteriods into a planet, your not going to see the formation of life.

 

[imaplanck]

That seems a bit harsh.

Why is it?

There is absolutely no forensic evidence to back up these alien stories, but plenty of evidence of ulterior motives i.e. a desire to cash in on the impressionable dreamers.

 

[fournier17]

The way I see it, is even if we even get to plug actual figures into the drake equation: The distances will in all likelihood be too restrictive for us too ever be able to reach the percentage of life that has reached technological civilization, and the reverse is also true.

What about worm holes. We could theoriticaly bend space/time and use a worm hole to punch through space/time. Heres some food for thought. Our planet has been around for about 4.5 billion years, it took about a billion years for the formation of the first prokaryotes. What if life began somewhere close to the beggining of the universe. Let's say life began somewhere when the universe was 1 billion years old, and that it took life there about 3.5 billion years to evolve an intelligent civilization. That civilization would be 10.5 billion years older than ours. Look how much we have done in the past 100 years, what if there is a civilization out there that has had 10.5 BILLION years to advance. I am sure if worm hole travel is possible, they would be using it. This hypothetical civilization would be almost god like compared to us, with their technological capabilities.

 

[imaplanck]

What about worm holes.

What about if fairies magic us across the galaxies/clusters/universe?

Heres some food for thought. Our planet has been around for about 4.5 billion years, it took about a billion for the formation of the first prokaryotes. What if life began somewhere close to the beggining of formation the Universe. Let's say life began somewhere when the universe was 1 billion years old, and that it took like there about 3.5 billion years to evolve an intelligent civilization. That civilization would be 10 billion years older than ours. Look how much we have done in the past 100 years, what if there is a civilization out there that has had 10 BILLION years to advance. I am sure if worm hole travel is possible, they would be using it. This hypothetical civilization would be almost god like with their technological capabilities.

The bigbang itself is estimated to be around ten billiuon years old, and didnt settle down to well in on that time.

 

[fournier17]

What about if fairies magic us across the galaxies/clusters/universe?



The bigbang itself is estimated to be around ten billiuon years old, and stars and planets didnt come about to well in omn that time.

-People use to think human flight was impossible as well. Given enough time, what do you know, we humans are in the sky. Now we can travel across the Alantic in less then a day when it took our ancestors months.

-I read some where that our universe is 15 billion years old, but that besides the point. What if there is a civilization out there that is billions of years older than ours. Dont you think they would be FAR more advanced then us? I think they would be able to do a lot of things that we think is impossible.

 

[imaplanck]

-People use to think human flight was impossible as well. Given enough time, what do you know, we humans are in the sky. Now we can travel across the Alantic in less then a day when it took our ancestors months.


-I read some where that our universe is 15 billion years old, but that besides the point. What if there is a civilization out there that is billions of years older than ours. Dont you think they would be FAR more advanced then us.

Yes you are right its 15(sorry). `


Yeah I think they would be FAR in advance of us, but (given the vast improbability of abiogenesis) I also think they could quite possibly be billions, if not trillions of light years away, if they exist at all. Never the less- Wormholes are purely a hypothesis, and even so how would one pinpoint a single inhabited star in 10^9999999999999 stars, say?

 

[Schrodinger's Dog]

I don't think we're quite there yet. The last the I saw, we can only detect relatively large planets, like Jupiter. And I recall the comment being made that this [finding Jupiters] is a very good sign because large planets make life on smaller planets possible by clearing the system. So finding big planets bodes well for life.

I think the current smallest planet is in the order of ten or eleven times the size of Uranus, but that's from memory it might be a bit larger.

 

[russ_watters]

-People use to think human flight was impossible as well. Given enough time, what do you know, we humans are in the sky. Now we can travel across the Alantic in less then a day when it took our ancestors months.

That is a very commonly used strawman. The huge difference between flight and ftl travel is that there never was a scientific theory that ruled-out flight. Flight was always a technological problem, not a theoretical one.

Look forward a couple thousand years and compare it to the view the ancient Egyptians would have had of us. Since the Egyptians knew about birds, I don't think they would be terribly surprised to see us flying. Flight fit with what they knew about reality. But looking forward, and seeing ftl travel a few centuries from now would require a scientific framework incompatible with the reality we see around us today.

That all said, I don't think the distance problem is very big one, though I'm not one who is looking forward to seeing a flying saurcer land on the White House lawn and taking day-trips to the Vegan system (I'm a meat eater anyway, so I'd hate that place). I believe it is possible with technology currently under development to prove to a level of certainty acceptable to scientists (but not laypeople or True Believers) whether or not there is life in any system within a thousand light years or so. Once that is done, communication becomes a relatively straightforward (if ultimately pointless) exercise.

 

[fournier17]

To get elements for life (Carbon/Oxygen and all the other elements of the periodic table), you need these made in a first-generation star which creates these as the products of nuclear fusion. This star then has to explode to create the dust/gas for a second generation star (like our Sun). QUOTE]

Is it known at what age of the Universe, the first second generation stars started to appear?

 

[imaplanck]

Very constructive of you to just say someones point of view is a 'fantasy'. Although the 'evidence' at present is certainly far from conclusive, it's not all totally dismissable (IMO).
Personally, I find less than a few percent of cases to have some merit to them, but that few percent is what makes the difference.
Any further scientific effort is always welcome.

At least you make a point here:



I partly agree with you here as I know a lot of people are in it for the money ( and publicity) and I haven't seen any physical evidence so far. But there also a lot of people NOT in it for the money and any real evidence COULD have been put out of public view by governments.
[As a sidenote, I remember seeing a clip of Stanton Friedman on a UFO program a while back (He's an ex-nuclear physicist who now seems to make a living doing the UFO-talk circuit and is a pro-UFO beleiver) . Anyways , he got filmed doing a behind-the scenes book-signing at one point and my impression was that he was very happy to talk to people if they bought his book, but wasn't interested at all otherwise!]



The timescale of our evolution:
Universe started approx 13Billion years ago (+/- a couple of billion).
The Earth/ Solar system is approx 5Billion years old.
To make life you need complex elements, that is, higher elements than Hydrogen/Helium.
To get elements for life (Carbon/Oxygen and all the other elements of the periodic table), you need these made in a first-generation star which creates these as the products of nuclear fusion. This star then has to explode to create the dust/gas for a second generation star (like our Sun).
So sometime during the first 8Billion years of the Universe our 1st generation progenetor star existed.
When our Earth started to form, after the first Billion years or so, basic single cell life forms existed for the next 3 Billion years and only the complex life (multicellular) started 4Billion years after the Earths formation. All the larger scale life forms have only been around for the last 600Million years or so.
So small and large differences in evolution time could exist between different alien races and hence in different levels of advancement and understanding.
.

I have studied the big bang to a degree, from the forming of hydrogen onto more complex elements etc, and the supernova event and the subsiquent settle down etc. I just fail to remember the details. Anyway I concede that life elsewhere could possibly be billions of years ahead of us.

It was only a few hundred years ago that the leading scientists of the day stated it would be impossible for people to travel faster than on horseback as the force-fullness of the air would make it so people would be unable to breathe.
If you were to tell a stone-age man that you could speak instantly to someone anywhere in the known world or fly like a bird or go to the moon I think he would say your point of view would be a 'fantasy'.

That is crap! the steam locomotive is 200 or so years old. Also one the flight front- Cayley invented the glider(heavier than air flight) over a century before the wright brothers famous flight, and I refuse to believe the rubbish touted, that no one could have thought powered heavier than air flight was possible before the Wright bros.

At any rate this type of naive analogy(used to allude that anything you can possibly conceive of, will eventually be achieved), is perilously foolhardy to say the least.

 

[Ivan Seeking]

As a UFO believer, how do you feel about the upcoming interferometry missions and other scientific searches for life?
Are they just a complete waste of time to you, seeing as a few retired pilots (with a interest in making a few bucks) have reinforced your fantasy that Aliens have visited earth?

That was intended for me?

First of all, I don't know what you mean by a UFO believer. You will have to explain to me what I believe.

Next, you will need to explain exactly what my fantasy is.

Also, keep up the insults and you will be penalized.

As for SETI and the question: What if ET was here? You can be the judge of the implications.

Psssssst: I ran SETI@Home on multiple computers for seven years.

Oh yes, to say that the entire UFO phenomenon boils down to a few retired pilots shows that you have no knowledge of the facts.

 

[russ_watters]

You think a stone-age man would have believed in people flying?

I absolutely do. It is known for certain that people have dreamed of imitating birds for thousands of years. They knew even then that there was no theoretical limitation: what prevented humans from imitating birds was always known to be a matter of power to weight ratio. History of flight: http://www.ueet.nasa.gov/StudentSite/historyofflight.html

And remember to differentiate flight from powered flight. The ancient Chinese flew kites (which is one way the Wright bros tested their designs).

It was only a few hundred years ago that the leading scientists of the day stated it would be impossible for people to travel faster than on horseback as the force-fullness of the air would make it so people would be unable to breathe.

Scientists? do you have any quotes? The wind blows faster than a horse runs and people certainly knew that hundreds of years ago.

Regardless, lack of understanding of a scientific principle is not the same as having a working scientific theory that forbids a phemonena.

I said this was a strawman before, but it is really half straman and half misunderstanding of the difference between science and technology.

Another important concept here is that as science progresses, we gain a better understanding of what we don't know. Ie, at one time, the speed of light was thought to be infinite. But that was only because the ability to measure it didn't exist. Now, we can measure it to a known and ever increasing level of precision. This provides an [ever decreasing] margin for error in our theories. The potential for them to be wrong exists in those shrinking margins for error and any theory that replaces an existing theory will have to incorporate the theory as footnotes or limited/special cases in the same way that for many applications Newton's theory of gravity still works depending on the case and margin for error required.

There may be unusual ways to circumvent theories like SR (and FYI, things like wormholes do not provide those avenues - they have properties that forbid it as well), but we certainly will never be able to go through it, meaning an action-reaction rocket will never travel faster than C. How can I be so sure? Because we've already put lots and lots of energy into particles and found that we can't accelerate them to a speed above C.

 

[DaveC426913]

Also, keep up the insults and you will be penalized.

From the strike through his name, I guess he did.

 

[DaveC426913]

Just because water is liquid does not mean that there is enough energy for many of the reactions that preceded biological evolution to occur. If only the minimal amount of energy required by water to be in a liquid phase was present, the reactions that took place in early Earth would have occurred very slowly.

Granted, and conceded. So,
4] Energy.

What does the ocean rest on top of? A surface is needed. Your not going to see biological evolution in gaseous planets.

Why do you bring up gaseous planets? We've already placed the requirement for liquid water; it could be a rocky planet or gaseous - as long as there is sufficient liquid water. Again, no surface is needed.

- The range from the parent star is covered under the "liquid water" requirement. It is not in-and-of-itself a requirement.QUOTE] [/B]
-The range of the planet to a parent star is important, if a planet is to close, it would be like Venus, which would be to hot for life, to far and its to cold.

Again, covered under liquid water. Any planet that's too close or too far will not have liquid water. The corollary holds true as well: if it does have liquid water, it is (by our current understanding of life) the right temp for life.

Life needs a staple environment in order to start. If their is continuous bombardment of asteriods into a planet, your not going to see the formation of life.

I disagree.
Life needs a stable environment to evolve to complex forms.
If a planet is continuously bombarded, you're not going to see complex life.

My point here is that a planet will be no less interesting for us to study just because it has "merely" the simplest kinds of life that could evolve on its battered home.


And my bigger point is that only the 4 requirements are required for us to examine a target in earnest for life. Any of the requirements you mention above should NOT disqualify a target for a search.

 

[Ivan Seeking]

Iam feeling rather ill after writing out a full page reply to Russ_watters and having it disappear when trying to post it. I can't face writing that out again. I haven't the will.

I know the feeling all too well. This is especially likely to happen when you have spent a great deal of time writing a response. If I'm not using Word as an editor, what I do is highlight the entire response and hit [Ctrl C] before hitting the post button. That way you can always paste it back in if the post fails.

 

[vanesch]

That I happen to share the same sentiment as you in believing that there are lots and lots of planets out there with life, I'm quite simply stating that we cannot logically extrapolate from a single instance we know of to the probability of its universal occurrence.

Yes, that was exactly my point. The fact that intelligent life developed on Earth is *no indication at all* that intelligent life has a relatively high probability to develop, because it is a totally biased statistic. The only thing that it indicates is that it is not totally impossible. It would be like me being on a desert island, assuming that there must be a serious fraction of all human beings with the name patrick van esch, because that's my name, and it is the only name I know off.

Now, the day that we find other, independent life somewhere is a totally different issue. From that moment our set of un-biased observations is non-empty. But as of now, we haven't gotten any clue, and the fact that WE are here doesn't mean anything.

EDIT: I should maybe clarify. I'm not thinking that the entire universe is completely devoid of life, or the opposite. I'm totally agnostic about it. I only wanted to point out that Carl Sagan kind of reasonings are very romantic, but they are not scientific per se, because of the inherent bias. In fact, the same applies to that part of biological evolution that is in our direct ancestry: it is also potentially biased. Even if there would be a totally improbable step in the evolution that leads up to us, that is no reason to discard it, because it has been "post-selected" by our very presence.

 

[DaveC426913]

Yes, that was exactly my point. The fact that intelligent life developed on Earth is *no indication at all* that intelligent life has a relatively high probability to develop, because it is a totally biased statistic.

Right, but the other side of the coin is that, if we are given a planet that has virtually the same parameters of Earth, temp, chemical makeup, etc. is there any logical reason WHY the same processes would not occur?

One could argue that, in the vast array of the galaxy, there will be a number of planets that are very Earth-like. I'm sayin' a probability of ~1.0 that there is at least one.

If you start that Earth going on its path, the likelihood that it will develop life is ~1.0 - MINUS the accumulating ways its future deviates from Earth (impacts, solar disturbances, etc.)

Looking at it this, way, we CAN deduce the likelihood of ET, based on what we DO know could happen.

 

[Schrodinger's Dog]

Now this is the sort of debate that the Drake equation is supposed to promote, well minus the insults, worthless my foot.

OK can we agree that the galaxy has 100billion stars then

 

[russ_watters]

Yes, that was exactly my point. The fact that intelligent life developed on Earth is *no indication at all* that intelligent life has a relatively high probability to develop, because it is a totally biased statistic.

Basically, it is the same as trying to construct a line (or curve) from a single data point.

 

[russ_watters]

Right, but the other side of the coin is that, if we are given a planet that has virtually the same parameters of Earth, temp, chemical makeup, etc. is there any logical reason WHY the same processes would not occur?

Sure: probability. We don't know whether what happened on Earth was a guarantee based on the starting conditions or a one in a quadrillion shot.

 

[Ivan Seeking]

Sure: probability.

False. We have no idea of the probablity. It could be 100%.

Edit: Okay, actually, Dave's post could read either way. I see what you meant.

Probability could be a limiting factor, but we don't know that it is, and there is no evidence to say that it is, but there is some probability that probability is a limit...

 

[Ivan Seeking]

In order for life in the univserse to be rare, the events that led to life would have to be phenomenally rare given the number of atoms and molecules that make up the biosphere; not to mention the millions or billions of years that they have to occur. How rare would the events leading to life have to be in order to be rare on the grand scale?

 

[Schrodinger's Dog]

TOO CLARIFY THESE ARE PARAMETERS FOR INTELLIGENT LIFE.

OK maybe it might be better to analyse this from the point of view of what we know to start and then extrapolate, for example what do we think are the basic requirements for life, I'll start with a basic list feel free to add to it.

A planet who's gravity is not so high or two low so as to preclude the formation of life forms and which has a stable surface, ie rock.

A sun formed hopefully of a size and energy output which promotes a good amount of planetary formation and is hot enough to sustain life but not too hot.

Water at higher than freezing point, ideally at a temperature where more chemical reactions can happen more quickly.

Inorganic compounds such as Cyanide and a good supply of minerals (PolyAromatic Hydrocarbons)PAH's and so on. Perhaps a second or so generation star, so there are more basic elements.

Perhaps a good amount of Cometary material to bring more water to the planet, and or seed it with more chemicals, although not essential.

Conditions so that a stable atmosphere of some sort can form.

A distance from the sun that does not mean a runaway greenhouse effect forms and is not too cold to inhibit life forming. Ie a temperate zone.

Large gaseous giants to help soak up some of the meteors flying around amongst the suns left overs.

If you agree these are the basics, what do you think the likelihood is of finding these types of conditions?

 

[Newbie says Hi]

OK maybe it might be better to analyse this from the point of view of what we know to start and then extrapolate, for example what do we think are the basic requirements for life, I'll start with a basic list feel free to add to it.

A planet who's gravity is not so high or two low so as to preclude the formation of life forms and which has a stable surface, ie rock.

A sun formed hopefully of a size and energy output which promotes a good amount of planetary formation and is hot enough to sustain life but not too hot.

Water at higher than freezing point, ideally at a temperature where more chemical reactions can happen more quickly.

Inorganic compounds such as Cyanide and a good supply of minerals (PolyAromatic Hydrocarbons)PAH's and so on. Perhaps a second or so generation star, so there are more basic elements.

Perhaps a good amount of Cometary material to bring more water to the planet, and or seed it with more chemicals, although not essential.

Conditions so that a stable atmosphere of some sort can form.

A distance from the sun that does not mean a runaway greenhouse effect forms and is not too cold to inhibit life forming. Ie a temperate zone.

Large gaseous giants to help soak up some of the meteors flying around amongst the suns left overs.

If you agree these are the basics, what do you think the likelihood is of finding these types of conditions?

Sorry Schrod, but I don't think I can agree with 1 of the points on your list (specifically #7). Computer models of Europa show that it may have a liquid water ocean under it's ice crust. Europa is far from the sun to maintain liquid water where it is too cold. It is not using the sun's energy to maintain liquid water (if it infact has liquid water) but using tidal heating thanks to Jupiter. So if Europa has liquid water, it opens up the possibility, I think for life that is NOT in the "habitable zone" of the parent star.

 

[Schrodinger's Dog]

Sorry Schrod, but I don't think I can agree with 1 of the points on your list (specifically #7). Computer models of Europa show that it may have a liquid water ocean under it's ice crust. Europa is far from the sun to maintain liquid water where it is too cold. It is not using the sun's energy to maintain liquid water (if it infact has liquid water) but using tidal heating thanks to Jupiter. So if Europa has liquid water, it opens up the possibility, I think for life that is NOT in the "habitable zone" of the parent star.

Agreed but the life there is liable to remain stuck in the water, I know the volcanic activity could lead to a water based life form evolving, given a thin layer of water and an ice crust on top, but there it stays, I think without land your liable to get only "sea" based creatures, and given it's almost lightless environs, life isn't likely to develop beyond a certain stage.

Point taken though.

 

[DaveC426913]

OK maybe it might be better to analyse this from the point of view of what we know to start and then extrapolate, for example what do we think are the basic requirements for life, I'll start with a basic list feel free to add to it.

A planet who's gravity is not so high or two low so as to preclude the formation of life forms and which has a stable surface, ie rock.

A sun formed hopefully of a size and energy output which promotes a good amount of planetary formation and is hot enough to sustain life but not too hot.

Water at higher than freezing point, ideally at a temperature where more chemical reactions can happen more quickly.

Inorganic compounds such as Cyanide and a good supply of minerals (PolyAromatic Hydrocarbons)PAH's and so on. Perhaps a second or so generation star, so there are more basic elements.

Perhaps a good amount of Cometary material to bring more water to the planet, and or seed it with more chemicals, although not essential.

Conditions so that a stable atmosphere of some sort can form.

A distance from the sun that does not mean a runaway greenhouse effect forms and is not too cold to inhibit life forming. Ie a temperate zone.

Large gaseous giants to help soak up some of the meteors flying around amongst the suns left overs.

If you agree these are the basics, what do you think the likelihood is of finding these types of conditions?

Again I disagree. I think you are being way too limiting.
It really only requires 4 ingredients:
- liquid water
- organic molecules (and inorganic material)
- energy
- time
+ sufficient quantities of the above

eg. You don't even need a solid surface. Life on Earth formed in the oceans.