Probability of Intelligent Life in Our Galaxy

[bozo the clown]

Can anyone work out the probabality of intelligent life at around our current level exisiting within our galaxy.

 

[force5]

Can anyone work out the probabality of intelligent life at around our current level exisiting within our galaxy.

I recall reading something a few years ago on the subject. I don't remember the person that did the calculations, but, those estimates determined that about 50,000 other planets (in our galaxy) should support organic life that has evolved to the point we have.

 

[Nereid]

Can anyone work out the probabality of intelligent life at around our current level exisiting within our galaxy.

There are a number of PF threads - both current and in the archives - that discuss the many such calculations. Try googling on "Drake equation" for sites.

 

[Rader]

"The probability"

The probability, might be, it is everywhere. It boils down to, where the center of the universe is? If our universe was once a singularity, where are we? We are at the center and so is every other point. Its a question of time frames. All points are the same points, at light speed. If this is so, then only when are tecknology reaches, the ability to travel at subluminal speeds will we make contact. All intellegent life, would develope together simultaniously but that's only if my therory is correct.

 

[pnjabiloafer]

hello, well bozo, i think there were people who thought just like you. There is one guy, and he formed an equation to figure out the probability of life existing in space. you can go here (http://www.pbs.org/lifebeyondearth/listening/drake.html) and check the chances by yourself. hope it helps. ;]

 

[Entropy]

There is about 1 in a trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion chance (I'm exaggerating) that life is exists in our galaxy, outside of Earth. Seeing that about 90% of the galaxy is to chaotic for relatively consistant environments to form or lacks the right elements. You also need a large gas giant in the star system and a large moon orbiting a planet (large moons are super rare) to stabilize it and block asteriods. Along with supernovae sterilizing chunks of galaxies its very doughtful that life exists anywhere in the universe outside of Earth. Sorry but to me aliens are just as ridiculous as fieries, ghosts or leprechauns.

Then again, it did turn out that leprechaun exist...

hello, well bozo, i think there were people who thought just like you. There is one guy, and he formed an equation to figure out the probability of life existing in space. you can go here (http://www.pbs.org/lifebeyondearth/listening/drake.html) and check the chances by yourself. hope it helps. ;]

The Drake equation is horrible incomplete.

 

[Chronos]

Good question and good arguments against the drake premise. Personally, I think extraterrestrial life is virtually certain [I have, however, been known to be wrong]. It pretty much boils down to this

1] Assuming our sun is a fairly common star in this galaxy (it is), some of the others have planets orbiting around them.

2] Some of those planets are similar to Earth in composition.

3] Some earth-like planets have orbits similar to earth.

4] Life will arise on some of those planets.

5] Intelligent life similar to our own will arise on some of those planets.

Assign probabilities to each and you get a non-zero probability that beings such as us have/do/will exist in this galaxy [not to mention the trillion other galaxies in the observable universe]. Whether enough of them exist, are near enough, and can be detected / communicated with at any given time is the most improbable scenario.

I think Dr. Drakes premises are very reasonable. The principle of mediocrity suggests we are not the crown gem of the universe.

 

[Rader]

Always all calculations either in favor or against the existence of extraterrestrial intelligent life, uses the assumption that life has its origins the same as we know it here on Earth. That to me is a very logical assumption and would get a vote from Occams Razor. That assumption is based on evidence from one planet ours. If we find one day life, right handed amino acids, different numeral combinations of amino acids that produce life forms, we would then draw the conclusion that, life is not unique to the parameters in which it had its origin, here on Earth and all the data we use to try and calculate its probbilities would be useless.

 

[marcus]

Can anyone work out the probabality of intelligent life at around our current level exisiting within our galaxy.

Fermi's question

 

[setAI]

I always find these ideas of predicting life [ala Drake] laughably primitive and simple-

there is always this core error of assuming carbon-based biology- it's silly- I think this is assumed because carbon-based biology is the only biology we can be sure about- but the biology isn't as important as the basic dynamics of living systems which only require an adaptable and sustainable energy handling capability and an environment that contains energy-

when one examines the tremendous complexity and specificity of conditions required for heavy-element based life and then compares it to the almost automatic and universal life-like dynamics of say- plasmas [ http://www.newscientist.com/news/news.jsp?id=ns99994174 ] it is clear that we are probably in a very tiny minority of living systems in the universe- with most life living on the surface of- or inside- stars- and in the intersteller medium and in/around nebulae-

we just don't know enough to use something like the Drake equation- especially considering that several of it's variables mistakenly require counts of planets and requirements of carbon biology- when most life may need neither- but every day we find reason to believe that life arises from a multitude of processes/substrates- many of which are far more abundant in the universe than planets and organic compounds-

same thing for the assumptions of the Anthropic Principle- life is going to evolve where it can with what it's got to work with- all a universe has to have is something to allow maleable/adaptable seperations and connections for the flow of energy-

I mean like- didn't anyone watch the Andromeda Strain?

___________________________

/:set\AI transmedia laboratories

http://setai-transmedia.com

 

[Ontoplankton]

One of the assumptions behind the Drake equation is that no interstellar colonization ever occurs, by anyone. That's way implausible.

 

[nolachrymose]

I mean like- didn't anyone watch the Andromeda Strain?

Don't you mean *read* the Andromeda Strain..?

 

[Chronos]

NASA apparently thinks extraterrestrial life is fairly probable, judging by the projects planned over the next decade.

http://www.universetoday.com/am/publish/search_for_more_Earth's.html?1272004

 

[Entropy]

but every day we find reason to believe that life arises from a multitude of processes/substrates- many of which are far more abundant in the universe than planets and organic compounds-

Actually no. We don't have a clue how most of the processes/substrates of life as we know it arose.

same thing for the assumptions of the Anthropic Principle- life is going to evolve where it can with what it's got to work with- all a universe has to have is something to allow maleable/adaptable seperations and connections for the flow of energy-

Life can only evolve where it can arise.

 

[setAI]

Don't you mean *read* the Andromeda Strain..?

no because the book sucks- but the film is quite lovely indeed! the book is pretty mediocre and not well written- but the film experiments with cinematography/score/script in very effective and important ways

___________________________

/:set\AI transmedia laboratories

http://setai-transmedia.com

 

[Nereid]

no because the book sucks- but the film is quite lovely indeed! the book is pretty mediocre and not well written- but the film experiments with cinematography/score/script in very effective and important ways

___________________________

/:set\AI transmedia laboratories

http://setai-transmedia.com

I thought the film was way too cavalier with the science (more a problem of the medium, not the director per se), and the book much, much better in that regard. Of course, film is a far better medium for characterisation, plot, visual experience, etc.

 

[nolachrymose]

I've never seen the movie, but I did quite like the book.
I've always found it irresponsible to make films, but that's totally irrelevant...

 

[Nereid]

I always find these ideas of predicting life [ala Drake] laughably primitive and simple-

there is always this core error of assuming carbon-based biology- it's silly- I think this is assumed because carbon-based biology is the only biology we can be sure about- but the biology isn't as important as the basic dynamics of living systems which only require an adaptable and sustainable energy handling capability and an environment that contains energy-

when one examines the tremendous complexity and specificity of conditions required for heavy-element based life and then compares it to the almost automatic and universal life-like dynamics of say- plasmas [ http://www.newscientist.com/news/news.jsp?id=ns99994174 ] it is clear that we are probably in a very tiny minority of living systems in the universe- with most life living on the surface of- or inside- stars- and in the intersteller medium and in/around nebulae-

we just don't know enough to use something like the Drake equation- especially considering that several of it's variables mistakenly require counts of planets and requirements of carbon biology- when most life may need neither- but every day we find reason to believe that life arises from a multitude of processes/substrates- many of which are far more abundant in the universe than planets and organic compounds-

same thing for the assumptions of the Anthropic Principle- life is going to evolve where it can with what it's got to work with- all a universe has to have is something to allow maleable/adaptable seperations and connections for the flow of energy-

Nice vignette of the problems of doing science here.

The Drake approach (ditto Fermi's question) explicitly assume 'life like us', and to fault it because it ignores entirely different (potential) kinds of life is like saying that economics can't tell you anything about nuclear reactions in the core of the Sun - it's way outside its intended domain of applicability. Ditto the anthropic principle (tho' for different reasons).

How can we go about estimating – even to 5 OOM! – the probability of ‘life-not-like-us’? Based on solid science please, not unbridled speculation.

 

[turbo]

We have (right here on Earth) life that is carbon-based, but very unlike us. For instance there are fast-growing dense populations of animals (huge tube worms, mollusks, crabs, etc) that are totally dependent on the sulfur-rich columns of water spewing from volcanic vents on the ocean bottom. If those animals were sentient and developed their own version of the anthropic principal, they would say that the universe could not have developed without providing for their existence, including a very cold, dark, high-pressure aquatic environment with lots of sulfur and no competition from light-loving photosynthesis-exploiting organisms.

Of course, we know that such a "sulfurphilic" principal would be ludicrous, and that those creatures developed incrementally and adapted to fit their very strange environment. I have a huge problem with the anthropic principle for this very reason. Knowing what we know about the adaptability and variety of life on earth, it would be foolish to rule out the possibility that organisms have evolved to exploit the energy-gradients and "food sources" that exist in the atmospheres of gas-giant planets, on the surfaces of volcanically active moons, in partially frozen hydrocarbon lakes, etc. The organisms need only manage to exist and propogate, and they needn't be carbon-based, either. I know of NO way to calculate the probability that such organisms exist, but since there are living things all over the Earth in even the most hostile, forbidding (to humans, that is) environments, we should be open to the possibility that environments which would kill us instantly can support life - just not human life.

 

[Entropy]

they would say that the universe could not have developed without providing for their existence, including a very cold, dark, high-pressure aquatic environment with lots of sulfur and no competition from light-loving photosynthesis-exploiting organisms.

Why? We don't say that life developed on land just because we live on it. We predict where life will occur by using our knowledge of the universe.

The organisms need only manage to exist and propogate, and they needn't be carbon-based, either. I know of NO way to calculate the probability that such organisms exist, but since there are living things all over the Earth in even the most hostile, forbidding (to humans, that is) environments, we should be open to the possibility that environments which would kill us instantly can support life - just not human life.

Its not that simple. Life must also be able to "arise" there. Make a controlled environment with a hydrocabon puddle or a simulation of Jupiter's atmosphere (wind, lightning and all) and life doesn't form. Just because they can survive there doesn't mean a second genesis will occur.

 

[turbo]

Why? We don't say that life developed on land just because we live on it. We predict where life will occur by using our knowledge of the universe.

My point is that the creationists and others who cite the "anthropic principle" not only cite physical characteristics of the universe (as we understand them) to claim that the universe was designed for humans - they also usually cite a lot of non-cosmological conditions that are specifically necessary for the existence of human life, which is an incredibly narcissistic viewpoint. If a supernova exploded near the Earth several million years ago and sterilized the Earth of all life, would the existence of the universe somehow become suspect or void from that point on? That's the implication of the anthropic principle, since the only way that the human race can be here is if we haven't suffered a recent supernova extinction.

Its not that simple. Life must also be able to "arise" there. Make a controlled environment with a hydrocabon puddle or a simulation of Jupiter's atmosphere (wind, lightning and all) and life doesn't form. Just because they can survive there doesn't mean a second genesis will occur.

It is just that simple. How old was the Earth when life arose here? A billion years? That leaves well over 3 billion years for life to develop to the stage we are at now. Has any scientist done any billion-year-long experiments to see under what conditions life can arise, or in which environments? Probably not. We cannot make a few rudimentary attempts to produce what WE regard as precursors to life (like an amino acid) and on the basis of that negative result rule out the existence of extraterrestrial life. That is not science - it is a comforting bit of anthrocentric orthodoxy dressed up in a lab coat.

 

[Chronos]

I guess there are different interpretations of the anthropic principle. I do not agree with any interpretation that confers it causality. That quickly devolves into circular logic. The sensible interpretation is that observations that forbid our ability to make that observation have either been misinterpreted or are inaccurate. So, if you were to plot the course of a nearby star and then deduced it had collided with Earth 5,000 years ago, something is wrong. Obviously, the Earth is still here and most of us are pretty confident it has been here for more than 5,000 years. You can therefore conclude you observations, or calculations used to arrive at your deduction are flawed.

Footnote: The tubeworms would be entirely justified to question any observation that led to the conclusion deep sea sulfur columns cannot exist.

 

[Chronos]

Regarding the Fermi objection. Does the Fermi objection preclude 'life like ours'? Obviously not. We are very similar to 'life like ours' and we have not colonized other star systems, astro-engineered the solar system, or done anything else inhabitants of other star systems would necessarily find noticeable. Perhaps incredibly advanced civilizations would have no need or reason to do anything noticeable by our primitive technology. Those tube worms in the depths of the ocean could just as easily apply the Fermi objection to our existence.

 

[Ontoplankton]

We are very similar to 'life like ours' and we have not colonized other star systems, astro-engineered the solar system, or done anything else inhabitants of other star systems would necessarily find noticeable.

We've only had the technology for a few decades, if at all (as opposed to thousands or millions of years).

 

[marcus]

I agree with what Onto just said
we haven't got the technology yet----and certainly haven't had a colonization program in operation for a million years. Not sure what this proves.

I have never till now heard of Fermi's Question called by the name
of Fermi's objection.
I think it is a good question and has a number of stimulating possible answers. I would not call it an objection.

To what is Fermi's Question an objection?
What precisely is the proposition you think Fermi was objecting to.

the way I heard it, they were all at Los Alamos and used to eat breakfast together and Fermi sometimes had already had breakfast and gone to work. So he left them a note on the breakfast table that morning and the note just had 3 words:

WHERE ARE THEY?

it strikes me as an invitation to think

maybe someone else has a more authoritative version of the story

 

[Chronos]

We've only had the technology for a few decades, if at all (as opposed to thousands or millions of years).

That presupposes 'they' would do the kind of things we think we would do with sufficiently advanced technology. Fermi correctly observed there is no compelling evidence of anyone else out there. No green dudes landing on the white house lawn, no alien radio stations blasting weird music at 500 terawatts, no stars winking out of existence as they are being mined. But, to conclude no one 'else' is out there on that basis, seems a bit hasty. There are other explanations that appear to be at least as reasonable.

No evidence of Earth landings, colonization, etc? We do not have, or know of any practical way to traverse the gulf between the stars. Who is to say anyone 'else' has figured it out? Maybe there is no way to beat or get around the speed of light barrier and subliminal transportation is so impractical it is only attempted in cases of absolute desperation. That would make it a pretty rare event, so it would seem.

No extraterrestrial EM signals. Have to wonder how long that kind of technology would last before something better and less detectable by our technology would replace it. It seems reasonable to doubt we could detect signals from civilizations with technologies more than about 100 years ahead or behind of our own. That only infers that civilizations within 100 years of our own, technologically, are pretty scarce, or too recent for the signals to have yet arrived. That does not seem particularly improbable. For that matter, who is to say we would even recognize the signal pattern was artificial? Our concepts of pattern recognition and communication may not be shared by community at large.

 

[marcus]

for me it invites to think about a 1% colonizing civilization
spreading gradually thru our galaxy at 1% of speed of light
with a pause of a couple of hundred years at each colonized star
to build up strength before sending out the next wave
and taking around 10 million years to hit most of the habitables

if this had ever happened they would probably have left beercans
or some other junk as civilizations do, and we didnt see any

so this has never happened in Milky, in all the 10 billion years that
Milky has been cranking out metal-rich stars

there never has been a 1% of light speed civilization that had the impulse to colonize----at least not a beer-drinking one----not in the whole
9.99 billion years that is the lifetime of Milky minus the past 10 million.

So

I don't know. that seems like a really interesting idea. Milky's virgin.
Wow. Why?

 

[marcus]

That presupposes 'they' would do the kind of things we think we would do...

Hi Chronos, I am personally not presupposing anything in particular.

What I am wondering is why you call Fermi's Question by the name
of "Fermi's objection"?
do you know something about Fermi's frame of mind that I do not?
Do you know a more detailed version of the story?
Who else, what author, calls it an objection?

 

[Entropy]

If a supernova exploded near the Earth several million years ago and sterilized the Earth of all life, would the existence of the universe somehow become suspect or void from that point on? That's the implication of the anthropic principle, since the only way that the human race can be here is if we haven't suffered a recent supernova extinction.

I don't understand your point.

It is just that simple. How old was the Earth when life arose here? A billion years? That leaves well over 3 billion years for life to develop to the stage we are at now.

Well from what I know life has only been around 2 billion years, but that doesn't matter. The point is that life around 2 billion years ago was basically the same as it is now, carbon-based, DNA, cells, etc.

We cannot make a few rudimentary attempts to produce what WE regard as precursors to life (like an amino acid) and on the basis of that negative result rule out the existence of extraterrestrial life. That is not science - it is a comforting bit of anthrocentric orthodoxy dressed up in a lab coat.

Well I'm pretty sure that examining results, negative or not, and observations and drawing conclusions is science. But I know what you're basically saying: "We know so little about the universe how can we make such bold assumptions?"

I think the real thing we need he is a proper definition of what life is.

 

[Chronos]

Here is a source [not a ufo site, btw] regarding the Fermi paradox [the common use terminology]

http://www.space.com/searchforlife/shostak_paradox_011024.html

Plenty of busted pottery to sort through to find any meat on this topic. My principal objection to the Fermi paradox is the 'divide and conqueor' assumption. It seems logical to assume that philosophy and technology must evolve at compatible rates to avert self destruction. Too much power is ultimately lethal to the user if they don't have enough sense to know how and when to use it. I would like to think any society a million years or more advanced than ours is also far more civilized and environmentally sensitive than us. Heck, even at our primitive level of development, were we to discover an entirely new life form on this planet, we would go to great lengths to avoid disturbing it or it's environment.

 

[marcus]

Can anyone work out the probabality of intelligent life at around our current level exisiting within our galaxy.

one

it exists: we observe life at around our level exists within Milky,
therefore it is a certainty and the probability is one.


now why don't you ask about Andromeda?
that would be interesting to try and estimate:
the probability of life at around our current level existing within Andromeda

 

[Chronos]

Hi Chronos, I am personally not presupposing anything in particular.

What I am wondering is why you call Fermi's Question by the name
of "Fermi's objection"?

Careless usage. Just a characterization of what it implies: an objection to ET. In polite society, it is usually referred to as 'Fermi's Paradox'.

do you know something about Fermi's frame of mind that I do not?
Do you know a more detailed version of the story? Who else, what author, calls it an objection?

This is as detailed as it gets, far as I know.
http://www.fas.org/sgp/othergov/doe/lanl/la-10311-ms.pdf

 

[Rader]

for me it invites to think about a 1% colonizing civilization
spreading gradually thru our galaxy at 1% of speed of light
with a pause of a couple of hundred years at each colonized star
to build up strength before sending out the next wave
and taking around 10 million years to hit most of the habitables

if this had ever happened they would probably have left beercans
or some other junk as civilizations do, and we didnt see any

so this has never happened in Milky, in all the 10 billion years that
Milky has been cranking out metal-rich stars

there never has been a 1% of light speed civilization that had the impulse to colonize----at least not a beer-drinking one----not in the whole
9.99 billion years that is the lifetime of Milky minus the past 10 million.

So Fermi thought this was possible, if there is no evidence, then what are the reasons?
01-We are alone.
02-They have not reached us yet.
03-They consider us ants.
04-They are here, we do not realize it.
05-All civilization devope at same time, we are and all are at the center of the universe. None are not m more advanced, than us, but many could be, equally or less advanced in there technologies.

1% of light speed civilizations, over a period of 10,000,000 years would develope in theory light speed craft.

01-I seems so.
02-Maybe if 5 is a possibility.
03-If 4 is a possibility.
04-If 3 is a possiblity.

What do you think about 5?

 

[selfAdjoint]

So Fermi thought this was possible, if there is no evidence, then what are the reasons?
01-We are alone.
02-They have not reached us yet.
03-They consider us ants.
04-They are here, we do not realize it.
05-All civilization devope at same time, we are and all are at the center of the universe. None are not m more advanced, than us, but many could be, equally or less advanced in there technologies.

1% of light speed civilizations, over a period of 10,000,000 years would develope in theory light speed craft.

01-I seems so.
02-Maybe if 5 is a possibility.
03-If 4 is a possibility.
04-If 3 is a possiblity.

What do you think about 5?

I don't think it's necessary for all civilizations to develop at the same time for us not to see them. Just that they don't develop very far beyond where we are. No interstellar travel, even by robots, sems to be the requirement.

 

[Nereid]

I know of NO way to calculate the probability that such organisms exist, but since there are living things all over the Earth in even the most hostile, forbidding (to humans, that is) environments, we should be open to the possibility that environments which would kill us instantly can support life - just not human life.

Its not that simple. Life must also be able to "arise" there. Make a controlled environment with a hydrocabon puddle or a simulation of Jupiter's atmosphere (wind, lightning and all) and life doesn't form. Just because they can survive there doesn't mean a second genesis will occur.

To continue in the theme of "it's not that simple":
1) If, after another 200 years or so of detailed searching, we find that there never was life on Mars, that would cause a bigger upset to astrobiology than finding evidence of extinct life. Why? Because we know life was well established on Earth within a billion years of its formation; indeed, we can't do any more to directly determine (by fossil evidence) how much earlier - than ~3.5 billion years ago - life flourished on Earth because there are no rocks on Earth older than this (at least, none that could retain fossils). We also know that there is regular exchange of material* between Earth and Mars (and between several other pairs of planets too), and that plenty of earthly bacteria could survive a trip between the two planets. So, if there was a time when the Earth had life and Mars was hospitable to life, then it's highly likely Mars was seeded by Earth. It may be that life originated on Mars and we are all the descendants of martians.
2) There are potential biospheres (for carbon-based life) that we haven't explored yet - the warm, deep biosphere of Gold, the >400C 'aquifers' below the oceanic crust (what are those filmy white things which are sometimes seen to come out of the boreholes of such aquifers?), even the ecologies of clouds! Perhaps life originated in one of these unexplored niches? Or another niche that we have, at present, no knowledge of? If there is flourishing warm, deep biosphere, it may be that we surface creatures are merely trivial, 0.00001% deviations.
3) Where life originates may not be where life is comfortable today.
4) What about interstellar panspermia?
5) Maybe our simulations are missing a key ingredient? Maybe they need to run for ~>1 million years before life could arise?

 

[marcus]

...
This is as detailed as it gets, far as I know.
http://www.fas.org/sgp/othergov/doe/lanl/la-10311-ms.pdf

My sincere thanks to Chronos for posting this link about Fermi's Question.

there are a lot of eyewitness accounts here
It was 1950 or so
(dated by a newyorker cartoon they discussed)
It was at lunch
He said something like "where is everybody?"
and they all understood and laughed.


And I must confess that obviously it doesn't matter much whther you call it a Question or an objection or a paradox or, even you might say, a Quip.

I think it points out an odd thing for which AFAIK there is no one right explanation. If I yell and rant about this (which I hope doesn't hurt anybody's feelings) it is because of a sense I have that those Quips are the best---the leave it open. they do not prescribe a logical context in which they are always to be interpreted. they are questions pointing in lots of directions.

somebody could write a book with 5 chapters each picturing a different one of Rader's 5 possibilities, one could have a book called "Fermi's question" that explores and visualizes the different possible answers---a SciFi book I would think (unless science has gone out of style in SciFi)

 

[turbo]

Aunt Nettie gave the most convincing explanation of the origin of life on Earth 'way back in 5-3-2001. I'm surprised nobody here has cited her work.

http://www.dearauntnettie.com/archives/archives-0105.htm

 

[turbo]

somebody could write a book with 5 chapters each picturing a different one of Rader's 5 possibilities, one could have a book called "Fermi's question" that explores and visualizes the different possible answers---a SciFi book I would think (unless science has gone out of style in SciFi)

There have been tons of entertaining stories written about these very scenarios, mostly in the '40s through the '60s. In more recent years, the genre has shifted pretty hard toward fantasy, though. People actually refer to "hard" science fiction to denote that the author has tried make his storyline at least conform to possible physics, and not resort to miracles as plot devices.

There have been a number of stories actually that address advances in propulsion technology in the following way: A fast high-tech ship leaves for Proxima Centauri (for instance) and in a matter of months or years, it chances upon a chemically fueled ship that was sent out centuries before and was presumed lost. The crew of the new ship board the old one and find that over the intervening generations, the inhabitants have lost technological knowledge and skills, developed new ship-centered belief systems, forgotten all about Earth and the fact that they are on a colonization mission, etc, etc.

 

[marcus]

Aunt Nettie gave the most convincing explanation of the origin of life on Earth 'way back in 5-3-2001. I'm surprised nobody here has cited her work.

http://www.dearauntnettie.com/archives/archives-0105.htm

thanks for the Nettie link.
this is potentially a great source of information
and I will hereafter keep the link handy at all times

the poem about the man who
was asphyxiated by his own flatulence is inspiring
or expiring as the case may be

 

[Rader]

To continue in the theme of "it's not that simple":
1) If, after another 200 years or so of detailed searching, we find that there never was life on Mars, that would cause a bigger upset to astrobiology than finding evidence of extinct life. Why? Because we know life was well established on Earth within a billion years of its formation; indeed, we can't do any more to directly determine (by fossil evidence) how much earlier - than ~3.5 billion years ago - life flourished on Earth because there are no rocks on Earth older than this (at least, none that could retain fossils). We also know that there is regular exchange of material* between Earth and Mars (and between several other pairs of planets too), and that plenty of earthly bacteria could survive a trip between the two planets. So, if there was a time when the Earth had life and Mars was hospitable to life, then it's highly likely Mars was seeded by Earth. It may be that life originated on Mars and we are all the descendants of martians.

Nereid, what would you say if we found ACDTZ on Mars? This will be the most interesting find, if something `life`is different. The chances would be against this as you say but then if it was so, energy requirements and conditions, would be the only things necessary for life to pop up anywhere. We have only now a short time now to find this out.

 

[kurious]

More intelligent Life will exist where the most time has elapsed relative to where we are in the Milky Way.We have to consider time dilation from special relativity and time dilation from general relativity.So, for our galaxy greatest probability of more intelligent life than us is given by the planet in the Milky Way that has the smallest value
of gravitational field strength + speed relative to us.

 

[Rader]

I don't think it's necessary for all civilizations to develop at the same time for us not to see them. Just that they don't develop very far beyond where we are. No interstellar travel, even by robots, sems to be the requirement.

No, it is not necessary, I agree, it could be 2=3=4. What I want to do is explore the possibility of 5, using facts we know about cosmology. Let us assume we are alone here in the Milky Way. The closest Galaxy is M31 2.2 million light years distant. The diameter of the universe 15,000 million años luz. When we observe a Quasar, we see it in the past, if we could instantaneously be there and look to here, where is the Quasar? We would see the same past, for the Quasar would be the future. So no matter which direction we look in we see the past in the present. If we could be anywhere instantaneously, then we would be nowhere except the present and center of the universe. If the singularity of the Big Bang is to be taken as fact and all evidence to present, seems to indicate that. In one time frame all points are the same, at light speed. The Milky Way and Andromeda are for all practical measurements at the center of this universe, although local measurement indicates 2.2 million light years distant. According to Marcus it would take a 1% of light speed civilization, 10,000,000 years to explore and colonize the Milky Way. The Milky Way is 100,000 light years across. The closest star systems with any possibility of life are much farther than the amount of time we have been trying to locate with light signals, inside the Milky Way. Even if, signals would have to be exact, received, understood and sent back. To do this with M31 we need 4.4M light years. 1% of light speed craft, out of the question, it would be better to stay home and have a beer and wait for subluminal craft to be fabricated.

Putting all this in prospective we just might not notice them yet, because give or take a reasonable amount of time to evolve, there not here yet nor are we there until our technology develops.

In the old west 20 miles was a long way to travel, what was the radius of that traveler’s knowledge?

Maybe 5?

01-We are alone.
02-They have not reached us yet.
03-They consider us ants.
04-They are here, we do not realize it.
05-All civilizations developed at same time, we are and all are at the center of the universe. None are not more advanced, than us, but many could be, equally or less advanced in there technologies.

 

[Entropy]

and that plenty of earthly bacteria could survive a trip between the two planets.

I dought that. It gets over 1000 degrees C when something enters the atmosphere and the blast that threw a rock from Earth to Mars would have killed all organism on it. A meteoric blast is like a nuke.

 

[Chronos]

I dought that. It gets over 1000 degrees C when something enters the atmosphere and the blast that threw a rock from Earth to Mars would have killed all organism on it. A meteoric blast is like a nuke.

Not all meteors explode like a nuke. Most just break into pieces. While it is true the outer surface can get mighty hot, the heat does not conduct very deep into rocky meteorites [the ones most likely to carry stowaways]. Furthmore, fragments from those that break up may not get hot at all. A lot of material was blasted off the surface of planets in the early solar system when asteroid collisions were commonplace [and they are still uncomfortably common these days].

Here is an article about a meteorite found in antarctica that is believed to have originated from mars.

http://www.sciencedaily.com/releases/2001/02/010227073558.htm

Here is a link to the NASA site with a related article and links to info about other meteorites believed to originate from mars

http://nai.arc.nasa.gov/news_stories/news_detail.cfm?ID=85

 

[Nereid]

I dought that. It gets over 1000 degrees C when something enters the atmosphere and the blast that threw a rock from Earth to Mars would have killed all organism on it. A meteoric blast is like a nuke.

Another example of the real universe turning out to be richer than the imaginations of scientists!

It has been known for quite some time that the only part of a meteor that gets really hot is the fusion crust; the insides remain quite cool, say 40C. In fact, carbonaceous chondrites wouldn't be recognisable as such if they were heated uniformly to 1000 C!

More surprising was how easy it is for a large meteor impact on Mars (or the Moon) to accelerate surface rocks to escape velocity, and maintain the integrity of the rock itself. IIRC, it took the recognition of some meteorites here on Earth as being unequivocally martian to convince folk to re-examine their understanding of impact mechanisms; when they did, lo and behold, yes it was easy.

Of course, homo sap, or even a cockroach, would certainly be killed by the acceleration, but bacteria are a great deal tougher. Even if a 'big' critter could survive the blast off, the hard vacuum and radiation of interplanetary space would do it in; not so bacteria, some of which can withstand truly extraordinary dosages, can 'hibernate' inside a rock in a hard vaccuum, and can be revived after dormancy of (hundreds of) millions of years.

 

[turbo]

05-All civilizations developed at same time, we are and all are at the center of the universe. None are not more advanced, than us, but many could be, equally or less advanced in there technologies.

That would be a tough condition to meet. Stars form at different epochs in the life of a galaxy, and who knows when conditions might will arise that would allow life to arise. There may have been civilizations that have already been cut short by their sun going off main sequence and expanding. Their planets could have already been swallowed by their red-giant host. Conversely, there could be lots of planets that "will" be amenable to life in another billion years. Our species may or may not turn out to be very transitory. We have been on Earth for a VERY brief time, and if we do not become more cognizant of our effects on the Earth, we could very well kill our biosphere and ourselves, like a virus that is self-limiting because it kills its host before it gets a chance to infect another host.

 

[Nereid]

Nereid, what would you say if we found ACDTZ on Mars? This will be the most interesting find, if something `life`is different. The chances would be against this as you say but then if it was so, energy requirements and conditions, would be the only things necessary for life to pop up anywhere. We have only now a short time now to find this out.

Please excuse my ignorance, what is 'ACDTZ'?

 

[Entropy]

Not all meteors explode like a nuke. Most just break into pieces. While it is true the outer surface can get mighty hot, the heat does not conduct very deep into rocky meteorites [the ones most likely to carry stowaways].

Any blast that is going to launch a rock from Mars to Earth or visa versa has to have power around that of a nuke, so yes it would be like a nuke. I think more accurately you ment: "rocks can be accelerated by the shockwave [of the blast] into space without being cought in the fireball of the actual impact."

Here is an article about a meteorite found in antarctica that is believed to have originated from mars.

About that, isn't a little weird that the gas in the meteorite matched Mars's atmosphere exactly? The rock is suppost to be billions of years old right (not since it impacted Earth)? Strange that it's atmosphere would be so unchanged.

It has been known for quite some time that the only part of a meteor that gets really hot is the fusion crust; the insides remain quite cool, say 40C. In fact, carbonaceous chondrites wouldn't be recognisable as such if they were heated uniformly to 1000 C!

Err... I find that hard to believe. How exactly does it not conduct heat to the center of the meteorite? Do you have any sources I can go to? I want to learn more on this.

 

[Chronos]

Any blast that is going to launch a rock from Mars to Earth or visa versa has to have power around that of a nuke, so yes it would be like a nuke. I think more accurately you ment: "rocks can be accelerated by the shockwave [of the blast] into space without being cought in the fireball of the actual impact."



About that, isn't a little weird that the gas in the meteorite matched Mars's atmosphere exactly? The rock is suppost to be billions of years old right (not since it impacted Earth)? Strange that it's atmosphere would be so unchanged.



Err... I find that hard to believe. How exactly does it not conduct heat to the center of the meteorite? Do you have any sources I can go to? I want to learn more on this.

Check out the NASA site and report back.

 

[Nereid]

Err... I find that hard to believe. How exactly does it not conduct heat to the center of the meteorite?

In a few words, many kinds of rock are excellent insulators, the meteorite spends only a short time in the air, the fusion crust ablates (carrying off a lot of the heat generated by friction with the air), and volume increases as the cube of the size while surface area only the square.

Do you have any sources I can go to? I want to learn more on this.

See Chronos' reply.