What is the probability of life in Universe?

[DaveC426913]

Personally i don't think we are the most evolved creature in Milky Way. According to wiki there are at least 200 billion stars in Milky Way alone, so what are the chance of Sun/Earth being the most habitable solar system? 200,000,000,000:1?

We are very lucky that Earth is in goldilock zone, but I'm sure there are plenty of planets in goldilock zone, n many of em are probably older and/or have better condition for evolution compared to Earth.

It's not about most habitable, or about conditions for evolution. At least, it deosn't start there.

It's about life spontaneously springing from non-life.

 

[DaveC426913]

I agree. It would be a monumental event to verify living organisms on a planet other than our own. I'd say there's a 100% probability of life in the rest of this galaxy.

What are the chances of using spectrometry to determine if there is life on one of the earthlike exoplanets being observed these days?

You are agreeing with an opinion that is 2+ years old. :-)

 

[Gannet]

Found attached link and remember seeing this thread and not seeing it previously cited.

http://hyperphysics.phy-astr.gsu.edu/hbase/astro/wcearth.html#c2"

It is interesting all the variables which have to be just right for life to exist. But this site is based carbon base lifeforms.

It is my hypothesis that there could be other chemical based lifeforms which we have not discovered yet. My definition of life is it has a beginning and end and in between those endpoints: it consumes resources, produce waste, and reproduce.

 

[DaveC426913]

Found attached link and remember seeing this thread and not seeing it previously cited.

http://hyperphysics.phy-astr.gsu.edu/hbase/astro/wcearth.html#c2"

It is interesting all the variables which have to be just right for life to exist. But this site is based carbon base lifeforms.

It is my hypothesis that there could be other chemical based lifeforms which we have not discovered yet. My definition of life is it has a beginning and end and in between those endpoints: it consumes resources, produce waste, and reproduce.

Yes, there is a possibility that there is some life that is non-carbon-based. Hoever, you will likely have to wade hip-deep in planets with carbon-based lifeforms before finding one that is otherwise.

Think of it this way:

We're sayin' I wonder if this 100-acre wood has any 3-leaf clover in it...
And you're saying Why concentrate on only 3-leaf clover, there's surely some 4-leaf clover out there too, let's throw a wider net.

 

[Dickfore]

It's 1 since there is life on Earth.

 

[DaveC426913]

It's 1 ...

No, that's the probability of you not reading the opening post.

...the probability of having life on other planets..

 

[DaveC426913]

Ahahah. too late. I saw that.

 

[Dickfore]

Ahahah. too late. I saw that.

Did you see the reason for deletion? Instead of the op, I saw the first post on the 3rd page.

 

[Chronos]

I like the idea of a high probability of life anywhere liquid water is found, and an extreme probability where oxygen exists in the atmosphere of an exoplanet. Both are the subject of study by exobiologists. Evidence of liquid water has already been found on the moons of Jupiter and Saturn. An undersea volcano would provide sufficient energy to fuel carbon based life forms. Current evidence suggests this is how life originated on earth. It is unlikely any element other than carbon would permit the complex molecules necessary for life. Silicon runs a very poor second.

 

[ranrod]

Thinking about this makes my head spin!

From the 200 billion stars in the milky way, how many planets on average for each? From the ones with planets, how many are stable solar systems? From those, how many will remain relatively uninterrupted for billions of years (not only the central star(s) but uninterrupted from outside-the-solar-system influences)? From those how many have a 'free' goldie locks area (no asteroid fields, no collisions for billions of years, no gas giants, no highly elliptical or irregular orbits)? From those how many have giant outside planets, such as Jupiter and Saturn that shield the life-bearing planets from asteroids and other planet killers? From those how many have a lot of water? From those how many have the other ingredients for life?

I can see the 200 billion stars yielding zero or a handful of candidates before we even ask if intelligent life can arise in them.

I'd like to know when do we think scientists will be able to come up with a more accurate estimate? 100 years from now? 50? 25?

 

[baywax]

I like the idea of a high probability of life anywhere liquid water is found, and an extreme probability where oxygen exists in the atmosphere of an exoplanet. Both are the subject of study by exobiologists. Evidence of liquid water has already been found on the moons of Jupiter and Saturn. An undersea volcano would provide sufficient energy to fuel carbon based life forms. Current evidence suggests this is how life originated on earth. It is unlikely any element other than carbon would permit the complex molecules necessary for life. Silicon runs a very poor second.

I agree Chronos. Its great that we have such close neighbours to study that are in the infant form of a possible abiogenesis. I am also convinced that panspermia is a definite player in the appearance of (carbon based) life. The liquid water and oxygen atmosphere not only provide good conditions for it but also provide a familiar environment for any visiting bacteria or large virus.

It is entirely probable that Mars seeded Earth or that Earth seeded Mars with life during the last 4.5 billion years. Especially since Mars shows signs of having been hit and having lost half her crust and all her oceans. At least some of her ejected bacteria or megaviruses could have made it here and began to colonize again.

 

[baywax]

Thinking about this makes my head spin!

From the 200 billion stars in the milky way, how many planets on average for each? From the ones with planets, how many are stable solar systems? From those, how many will remain relatively uninterrupted for billions of years (not only the central star(s) but uninterrupted from outside-the-solar-system influences)? From those how many have a 'free' goldie locks area (no asteroid fields, no collisions for billions of years, no gas giants, no highly elliptical or irregular orbits)? From those how many have giant outside planets, such as Jupiter and Saturn that shield the life-bearing planets from asteroids and other planet killers? From those how many have a lot of water? From those how many have the other ingredients for life?

I can see the 200 billion stars yielding zero or a handful of candidates before we even ask if intelligent life can arise in them.

I'd like to know when do we think scientists will be able to come up with a more accurate estimate? 100 years from now? 50? 25?

Like Dr. Stephen Hawking says, intelligence may not be the ultimate result of evolution and may actually be a mutation that hinders the survival of our species. This may not bode well in the search for other intelligent beings. He does hold out hope of finding life on other planets mind you.

 

[ranrod]

Like Dr. Stephen Hawking says, intelligence may not be the ultimate result of evolution and may actually be a mutation that hinders the survival of our species. This may not bode well in the search for other intelligent beings. He does hold out hope of finding life on other planets mind you.

That statement may work locally, but bacteria (used in his example) can't see the giant asteroid that will wipe out the planet. Intelligence allows us to protect Earth, as well as make other homes elsewhere in the galaxy (though we may not be doing a good job at either). Besides, on what grounds could we claim there's an ultimate goal to evolution? I can make the converse case - what good are all the amazing wonderments of the universe if there's no one out there to comprehend them?

 

[baywax]

That statement may work locally, but bacteria (used in his example) can't see the giant asteroid that will wipe out the planet. Intelligence allows us to protect Earth, as well as make other homes elsewhere in the galaxy (though we may not be doing a good job at either). Besides, on what grounds could we claim there's an ultimate goal to evolution? I can make the converse case - what good are all the amazing wonderments of the universe if there's no one out there to comprehend them?

Its true that there is, in all probability, no ultimate goal of evolution... except that it seems to be "survival". With regard to "what good are all the amazing..."... "good" is only relative to an observer, if and when there is one.

 

[Dmitry67]

My view is pessimistic: We exist, and probability of life in INFINITE Universe is 1, and there are infinitely many inhabited planets, however, probably even in the whole observable Universe there are no other planets with life.

There is a BIG GAP between complex molecules and primitive cell organisms. Very likely first bacteria was created by PURE CHANCE - in any case, nobody AFAIK was able to split that big gap into simpler steps

 

[Gannet]

Here is another site I found on this subject which I like. http://www.tufts.edu/as/wright_center/cosmic_evolution/docs/fr_1/fr_1_chem.html"

In section Qualities of Life it makes the following profound statement

... The reason is that living systems are so much more complex than any inanimate objects; a potted plant is more complicated than the most splendid galaxy.

 

[TubbaBlubba]

Here is another site I found on this subject which I like. http://www.tufts.edu/as/wright_center/cosmic_evolution/docs/fr_1/fr_1_chem.html"

In section Qualities of Life it makes the following profound statement

That's a bizarre statement in every imaginable way. I'm not even sure what they mean by it... By galaxy, do they mean everything that happens on every cosmic body at any given time? Just the shape? The gravitational forces keeping them together? The shape?

Any way, Milky way. I think we can consider the statement irrefutably disproved now.

 

[ranrod]

My view is pessimistic: We exist, and probability of life in INFINITE Universe is 1...

That is a very depressing statement

I would think if that "PURE CHANCE" you were talking about was 1 in 1,000 trillion, there would still be other planets with intelligent life. I guess that makes me optimistic

 

[DaveC426913]

I like the idea of a high probability of life anywhere liquid water is found, and an extreme probability where oxygen exists in the atmosphere of an exoplanet.

Can you clarify? It seems you are saying that life should have a high probability of forming where there is oxygen.

IIRC, oxygen is not a requirement for life; life on Earth started in a CO2 and ammonia atmo.

The reason exobiologists are interested in it is because its presence in an atmo is a sign of life - but it is a waste product.

So the cause-effect relationship is the other way 'round: first life, then oxygen.

 

[baywax]

Can you clarify? It seems you are saying that life should have a high probability of forming where there is oxygen.

IIRC, oxygen is not a requirement for life; life on Earth started in a CO2 and ammonia atmo.

The reason exobiologists are interested in it is because its presence in an atmo is a sign of life - but it is a waste product.

So the cause-effect relationship is the other way 'round: first life, then oxygen.

True Dave... however, the oxygen content of H2O is not a waste product and as someone or some paper has already pointed out in this thread amino acids are hydrophobic which probably coaxes them to bond together and form a primitive VRNA, RNA or DNA.

 

[Chronos]

Agreed dave, oxygen is the byproduct of life, not a prerequisite. Almost no other explanation is known that can account for free oxygen in a planetary atmosphere. Water, on the other hand, is a necessary precursor for life [as we know it]. It's presence is merely makes life a reasonable possibility.

 

[Dmitry67]

In infinite Universe the probability is irrelevant. I suspect that probability of life is about something 10**-200. But even in such case there are infinitely many planets with life - beyond the cosmological horizon

 

[brother time]

I suspect that life is fairly likely (75%) to exist. But I am wondering what is the definition that classifies as life? And isn't life not requiring oxygen and can form based on any element? I did a report on diatoms and found that some in the Antarctic only require sulfur and iron to live.
Cheers, BT

 

[Gannet]

In the section Prospects for Life in the {Milky Way} Galaxy
http://www.tufts.edu/as/wright_center/cosmic_evolution/docs/fr_1/fr_1_future.html"

The following chart is shown (see attachment)

 

[phyzguy]

The problem with this figure is that the size of the boxes are complete guesses. We have a pretty good idea of the number of stars with planetary systems, but most of the other probabilities, such as:
(1) the probability that a planet is habitable, or
(2) the probability that if it is habitable that it has life, or
(3) the probability that if it has life that it has intelligent life

are complete guesses. Today we have no idea if these probabilities are 1 in 100 or 1 in 10^100.

 

[DaveC426913]

The problem with this figure is that the size of the boxes are complete guesses. We have a pretty good idea of the number of stars with planetary systems, but most of the other probabilities, such as:
(1) the probability that a planet is habitable, or
(2) the probability that if it is habitable that it has life, or
(3) the probability that if it has life that it has intelligent life

are complete guesses. Today we have no idea if these probabilities are 1 in 100 or 1 in 10^100.

Well not quite. We know that the worst the odds can possibly be at the highest level are 1 in 10^11 (one example in 500 billion stars).

 

[phyzguy]

Well not quite. We know that the worst the odds can possibly be at the highest level are 1 in 10^11 (one example in 500 billion stars).

How do we know that? Are you basing it on the fact that there is intelligent life on Earth? We cannot draw conclusions of the probability of an event based on one example.

 

[DaveC426913]

How do we know that? Are you basing it on the fact that there is intelligent life on Earth? We cannot draw conclusions of the probability of an event based on one example.

Your wording was a bit ambiguous.

You were suggesting that the chances of any given planet in our galaxy being habitable could be as low as 1 in 10^100. I am simply saying that the odds for life on a a planet in the galaxy cannot be worse than 10^11, because in the sample 500 billion so far, we've found one example.

i.e. There are 10,000 clover plants in a field. You claim the odds that one of them is a four-leafed variety could be 1 in 10,000,000,000. I'm saying "Nope, I already have one from this field. That means the odds at worst are one in 10,000."

I think what you are trying to say is "the odds of finding another four-leafed variety could easily be 1 in 100,000,000." Which is true, it's just an odd way of calculating probabilities. Kind of like every time you get a positive hit, you toss it away and start counting again.

 

[Dmitry67]

You were suggesting that the chances of any given planet in our galaxy being habitable could be as low as 1 in 10^100. I am simply saying that the odds for life on a a planet in the galaxy cannot be worse than 10^11, because in the sample 500 billion so far, we've found one example.

?
This is true only if most of galaxies have life at least on one planet!
You are assuming that the choice of our galaxy is random, which is not of course (anthropic principle) - the sample is not fair - even worse, for obvious reasons this sample is guaranteed to be unfair until you find planets except our own

I claim that that probablility is 10**-200
This number is not only consstent with the data we have, but it is even supported by the observational data - http://en.wikipedia.org/wiki/Fermi_paradox - so called 'Great Silence'

 

[DaveC426913]

This is true only if most of galaxies have life at least on one planet!
You are assuming that the choice of our galaxy is random,

It hasn't been an assumption. We have been talking only about our galaxy.