Has anyone ever calculated the odds of life on Earth snce the Big Bang? You could either use a simple calculation such as yes or no for each phase or more indepth caluculation such the odds of formation of hydrogen vs other atoms, etc. etc.until the formation of intelligent life.

Life is a certainty on Earth. It has been here for a few billion years, as near as we can tell.

I'm not certain what you're getting at. For example, what do you mean by "phase."

All the hydrogen and helium (plus some deuterium and lithium) were created by the Big Bang, and heavier elements came later via nucleosynthesis and supernovae. Since stars formed prior to life on Earth, I'm not sure what you mean by "the odds of formation of hydrogen vs other atoms, etc. etc. until the formation of intelligent life." Since by "intelligent life" I infer you mean humans or their ancestors on Earth, and since biological life as we know it has water (H2O) as its primary constituent, then the "odds" that hydrogen and other atoms formed prior to such life are 100%.

So I must be misreading your meaning ... ?

I think the odds of life on Earth and in the universe in general are relativly short, but the odds of intelligent life are long.  Why do I think this?  Mainly because life evolved on the Earth as soon as it was cool enough, and may have arisen more than once.  Water is abundant in the universe, and the range of planet sizes that can accomidate life for long times is probably pretty large.  Say from the size of Venus to maybe half as large as Neptune.  Probably most planets in this size range in the habital zone of their stars can evolve life.  My guess is that habital solar systems have stars from maybe 5 or 10% larger than the sun to maybe half as large, and of course they need to be in relativly quite galactic neighborhoods, but not too quite.

As to intelligent life, it is probably pretty rare.  Why?  Because it took about 4.5 billion years, or about one third the age of the universe, for intelligent life to evolve on the Earth.  For the purpose of this arguement one must assume, of course, that there is intelligent life on the Earth.  My guess is maybe 1 to 1000 intelligent life forms, most of the time, in a galaxy like the MIlky Way, but maybe only one or two technological civilizations.

I don't know if this goes back in time enough for your question but here is a neat little bit of info.

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

That was what I was looking for . I had fogotten about Drake's equtsion.

Thank you!

in order to calcaculate the Odds of life as we know it you must consider all the things that make life possible for us on earth.

You must calcaculate the Odds that a planet the (size) of earth to form with the (required gravity )and (density) & ( planetary weight) with a rotating magnetic molten core that spins inside the earth at the (required speed) and produces the (correct magnetic field) to provide protecttion for the earths atmostphere for life to exist the (van allen belt) also known as the (magnetisphere) also the right amount of water, temperature volcanic activity, (atmostpheric gases) and (nitrification for fertile soil and water)., the (correct rotation of the earth) ( the correct distance from the sun), with the (correct type star) that has the (correct gravity, temperature, light emissions) and forms the earth in the (correct orbit for seasonal changes to take place), Also you need a (moon for tides to take place for life in the oceans) to exist this moon must be in the (correct orbit) and have the (correct gravity) and (rotation and size), the earth then must have the (correct conditions atmostpheric ionisation for weather patterns to form to produce lightening that can spark the beginnings of life.

The odds of the earth forming the way it did are very slim to none, unless these consitions are not rare then we should see many other planets like earth, But I think it is very rare for the odds of all these conditions to to exist and that it is very possible the earth is the only garden planet to exist in the entire galaxy, but it is possible that there are other earth like planets meeting all the conditions maybe 2 or 3 in the entire universe.

How many times do you win the lotto?, consider that if all these odds are met that the forming solar system has won a lotto.

We are talking about a set of many conditions to take place for life like on earth to exist.

earth size and orbit distance from star, atmostphere magnetisphere, core rotation, planet rotation ect

moon size and orbit distance from earth

star size, temperature and orbit

ect, once all these consitions are met you still need atmostphereic activity and nitrification to for even the most primitive microbes.

If your in a room with 40 billion people and there is a lotto being held, how many people do you think will win? meaning that all the conditions for a earth like solar system to exist.

There are about 40 billion stars in the Milkyway.

then after you meet all those conditions the planet has to have the correct amount of mineral rescources for a technology based life form to evolve.

Then lets say you do find another planet like earth with only animals on it, that has been evolving for millions apon millions of years, longer then the earth, there is no gurantee man could live on this planet even if all the conditions for man to live are met.

Virus's and bacteria also evolve, and we may find that the planet's microbiology wont let us live there because were not immune.

Man has evolved from a life supporting template that exists on earth, this template of life supporting functions may not exist anywhere else in the universe.

And, with all of the complex preconditions Sage mentions, life has apparently started only once on earth.  It seems that all organisms on earth have a common ancestor.  This implies (although doesn't prove) that life only started once on earth.  The probability that this planet, which is seemingly a pristine incubator for life, has only seen it happen once makes me pessimistic about even microbes exisiting anywhere else.

A clarification or two ...

Sage:

The odds of the earth forming the way it did are very slim to none, unless these consitions are not rare then we should see many other planets like earth, But I think it is very rare for the odds of all these conditions to to exist and that it is very possible the earth is the only garden planet to exist in the entire galaxy, but it is possible that there are other earth like planets meeting all the conditions maybe 2 or 3 in the entire universe.

Your last quote assumes there are fewer stars in the universe than there really are. If there are hundreds of billions of stars in a galaxy like the Milky Way, and many billions of such galaxies in the Universe, then the odds improve greatly. Read on ...

If your in a room with 40 billion people and there is a lotto being held, how many people do you think will win? meaning that all the conditions for a earth like solar system to exist.

Actually, depending on the way the lotto is conducted, there could be quite a few. A billion is a very large number. If someone says "the chances are a million to one against" and the pool is 40 billion, then something like 40,000 people could be winners. That's a lot more than one or two.

 

There are about 40 billion stars in the Milkyway.

It's at least several times that. Current estimates range from 100 billion to 200 billion. As to the number of galaxies, I've seen estimates that range from about 15 billion to 120 billion. I think the first estimate is low, but I have no clue whether 120 billion is high, very high, etc.

   First, the old number thrown around for stars in the milky way was about 200 billion.  Recent studies suggest the galaxy is twice as large--about the size of Andromeda--so 400 billion!

  So, whatever the base chance was, it is now doubled.

   It really gets down to some basic fundamentals.  Either you belief that earth as a home for life is special (not demonstrated), or that it is relatively common as far as terrestrial planets go (plausible, but not demonstrated).

  We do not have the technology (giant telescopes!) to easily survey stars for planets and atmospheric signatures.  However, as we are able to get early numbers on planetary systems and begin to describe them, statistical inferences tell us that other earth-lke planets should be abundant. as a % of total terrestrial planets (lets say 2% is abundant!). 

  The Copernican mediocrity principle suggests that the corner from which we observe the universe is not unique, and that similar conditions prevail in the galaxy and universe.  This principle has been reinforced as our knowledge of the universe has grown, not undermined.

  Only hubris, religous belief, and stubborness can account for maintaining that a planet orbiting an average G star in an unremarkable sector of a common galaxy type is the sole repository of life, or even intelligent life.

  Enrico Fermi calculated (and he was mighty good at that) that the galaxy should be vibrant with intelligent life.  His paradox  (c. early 1950's) asked why they weren't visible.  Revisiting his thinking, we should probably assume he was right about the former.   Which leads to the conclusion that our search strategies are flawed--we aren't looking in the right places/modes.

  Or at least some of us aren't.  Rude awakenings are in the cards...

cyberpatzer:

   First, the old number thrown around for stars in the milky way was about 200 billion.  Recent studies suggest the galaxy is twice as large--about the size of Andromeda--so 400 billion!

  So, whatever the base chance was, it is now doubled.

Actually, this news is not yet generally accepted. There is some debate over whether the more recent estimate of "size" means more mass, more volume, or both -- and in what mix. In other words, there may well be more stars, but it's too early to determine by what number.

I accept your point, however, and it puts a reasonable upper bound to the problem (in my view).

...  We do not have the technology (giant telescopes!) to survey stars for planets and atmospheric signatures. 

We can't yet do this well enough to "nail" it for more distant systems, but current technologies have revealed some tantalizing clues in nearby systems.

We need the Terrestrial Planet Finder or similar technologies, in my opinion, to "nail it."

Earth-based inteferometric scopes coming online soon will get very close ...

  Yes, it looks like 2015-2020 might be the opening salveo of the golden era of astronomy, with several titanic scopes online and able to easily sniff out planets and analyze atmospheres.

  I just hope I'm around and we still have t.v and/or computers and/or print media ( we could be back to cans and string, and smoke signals...).

cyberpatzer:

It really gets down to some basic fundamentals.  Either you belief that earth as a home for life is special (not demonstrated), or that it is relatively common as far as terrestrial planets go (plausible, but not demonstrated).

What about the vast middle ground where Earth-like planets exist, but are rare?  That would cut into the "abundent" numbers dramatically.  The only thing our planetary discoveries have shown, so far, is that the structure and nature of extraterrestrial systems are erratic and wildly varried.  None so far has demonstrated a morphology like our system.  I know that our tools right now are crude and only capable of detecting extreem planets, and that is exciting stuff, but not sufficient evidence to support a statistical inference of an abundance of Earth-like planets.

cyberpatzer:

Only hubris, religous belief, and stubborness can account for maintaining that a planet orbiting an average G star in an unremarkable sector of a common galaxy type is the sole repository of life, or even intelligent life.

If by stubboness you mean waiting for scientific proof instead of jumping to unsubstantiated conclusions, then I guess I'm guilty.  I believe that we will find evidence of life on other planets.  I believe that intelligence may exist (or have existed, or will exist) elswhere, but that it will be extreemly rare, and more rare yet that two intelligent species would exist at the same time.  No religous doctrine I'm aware of states that Earth is the sole repository of life in the universe.

cyberpatzer:

Or at least some of us aren't.  Rude awakenings are in the cards...

I think most people expect us to find evidence of life somewhere else in the universe.  So finding an Earth-like planet with an atmosphereic signature which hints at, or even confirms life isn't going to "rudely awaken" many people.  I don't see this as a competition between "believers" and "non-believers". 

  Fair enough.  What can a person say?  Could Earth -like planets be rare? Psshh. Maybe.  As someone has pointed out, nature seems to like repeating experiments in the millions, billions, trillions, and so on.  Not 1,2,12, 15.  She doesn't seem to know when to quit in this regard.  Jeff Marcy put the number of terrestrials in our galaxy at 60 billion, as a guestimation.  With the new size estimate of the galaxy, logic would increase this to 120 billion, but lets say 100 billion +/- 20 billion.  In our own solar sytem, it appears that at one juncture 1-3 billion years ago, conditions were right for life on TWO planets in one solar sytem.  One fizzled out, one produced sentience.

   In grand scale particulars, there is nothing that appears special about our solar system's formation ( as you have indicated, our detection methods as of now currently are only good at detecting outliers--extremes in solar system dynamics/planetary orbits...). 

  Again, there is no evidence, hence the discussion, but inference and reason will and should be leading the pursuit to final evidence.

  As to why two intelligent species couldn't; evolve in the same neck of the cosmic woods, I see no evidence that would discourage this possibility beyond basic probabilities (i.e.:  two G stars forming at approximately the same time, and with an uneventful wind-up to produce stable near-circular orbits....).  Local conditions and the amount of matter a star gathers appear to be more important than if life occured somewhere nearby-- some sort of galactic NIMBY!  (That said, I wonder what homo sapens has done to Orion arm neighborhood planet prices?!)

    Soon we will be able to directly image many different types of systems and all will be made clear.  My basic point was that chances of other life in the galaxy besides Earth, both intelligent and simple, are likely--both 100%.  Claims of human uniqueness on philosophical grounds are throwbacks to the middle ages.  Claims of human mediocrity would be tending towards the scientific assumption, albeit early assumption.

  All of this, and NO evidence. 

  It will be interesting to watch the swing from impossible, to possible, likely, and finally "I knew it all along"...

  The piece on proliferation of complex pre-organic molecules (non-proteins but including amino acids) in the interstellar medium reinforces the CP.  It also strongly suggests a panspermia hybrid of some sort, where many of the preconditions of life are met in gas and dust clouds of the galaxy.  This gives evolution a 5-10 billion year head start before our planet's formation, and would suggest that life forms quite readily in any corner of the galaxy that is hospitably to it, with earth-like conditions as a minimum standard.

   Exciting empirical evidence, confiming reasoned hypothesis.  Life, most likely, is everywhere.  Between our efforts on Mars, study of exoplanets, and the interstellar medium, it seems that things are coming to a crescendo.  I would be very, very suprised if the empirical confirmation doesn't arrive before 2020...

2-17-09:

  The BBC online reports today that a professor at the Carnagie Insitute estimates 100 billion earth-like planets, many supporting microbial/bacteril life similar to what was on Earth 2-3 billion years ago.  The post also reports that researchers at Edinburgh University estimate that there may be thousands of intelligent species in the galaxy.

  This is interesting for two reasons: first, it reinforces earlier work, and also, it is evidence that academics are examining this issue at the present time, integrating recent exoplanet and biology findings.

  'Tis a grand day for woos everywhere.

cyberpatzer:

2-17-09:

 

  The BBC online reports today that a professor at the Carnagie Insitute estimates 100 billion earth-like planets, many supporting microbial/bacteril life similar to what was on Earth 2-3 billion years ago.  The post also reports that researchers at Edinburgh University estimate that there may be thousands of intelligent species in the galaxy.

  This is interesting for two reasons: first, it reinforces earlier work, and also, it is evidence that academics are examining this issue at the present time, integrating recent exoplanet and biology findings.

  'Tis a grand day for woos everywhere.

Estimates and opinions do not reinforce anything, evidence does.  Did you also see this article in the same BBC on-line edition?

http://news.bbc.co.uk/2/hi/uk_news/england/norfolk/7352181.stm

This is the one which discusses the probability, and reasoning, that intelligent life is rare, and that humans will not be around long enough to find it.

So, this professor disagrees and is in the rare-Earth camp.  His (educated) opinion vs. others' educated opinions.

  Sort of like a parallel of our trailor, low rent debate on this forum. And indicative of the fact that the data set is incomplete enough to invite many viewpoints.

  Obviously, there is a considerable dissonance between 100 billion Earths and (barely, it seems) one.  Someone is clearly very, very wrong.

  I myself think it is the guy who's idea flies in the face of the Copernican principle, and who favors a universe where the incidence of life --or anything!--could occur once.  One in a multiple billions of chances. 

  But, no doubt about it.  One of these two camp is very, very wrong.

  I might point out that a lot can happen in the billion year interval this fellow speaks of.   Also, we should assume we are a part of a cohort of systems that have evolved in this epoch of the galaxy, amid many other cohorts that evolved both before and after.  We are in the midst of this flux. We might assume that some evolutionary processes were MORE difficult, and some LESS difficult.  This is reasonable, with insufficent empirical evidence to confirm specifics.  Again, perhaps we are at a midling value.  Fermi's prediction came from this sort  of thinking, contrary to professor, hmm, whatshisname.

  Maybe the dogmatics are right, and the universal atman placed homo sapiens on this eden of the cosmos, Earth,  to propogate wisdom and sentience as the sole intelligence in the galaxy.   At one level, this would be very exciting to see.  One thing is for sure.  THIS scenario will not be in my, or my child's children's lifetime!

   Also, you might be shocked to see how much science is actually consensus of opinion, so when academics chime in on the side of plurality, I give it due weight, for what it is, and assume the "opposition" is the majority    It is, after all, only when a sizeable minority of professionals get together and assert something that governments, funding sources, and the public take note.

  I am only pieceing together the argument for plurality, and observing the dialog unfold.  For whatever psychological reaons, this appeals to me.  Most likely my fondness for underdogs and anti-establishment bent.  However, the argument are real.  Its great that we can pick our teams.

cyberpatzer:

Fermi's prediction came from this sort  of thinking, contrary to professor, hmm, whatshisname.

Just for clarity's sake, Fermi's position was against the existance of a plethora of inteligent species.

  Oh yeah, well, well, he argued against intelligent life not because it was implausible, but because we see no signs of it where it should be READILY evident based on probability. ("They should already be here...")  Hence the term "paradox". 

  He then concluded there is no intelligent life in the galaxy besides homo sapiens.  Others--SETI and U** folks included--took the position that we simply aren't looking in the right places/modes.  This is another logical possiblity, and historically the great parting of ways.