# Your opinion about the "Rare Earth Hypothesis" ?



## matt-browne-sfw (Jul 20, 2007)

The authors of the book "Rare Earth: Why Complex Life Is Uncommon in the Universe" by Peter Ward and Donald Brownlee state that while simple life is probably very common, complex life is probably very rare.

There is more information here: Rare Earth hypothesis - Wikipedia, the free encyclopedia

What is your opinion about it?


----------



## gully_foyle (Jul 23, 2007)

Hi Matt,

I agree with the Rare Earth Hypothesis. I have never read a treatise on it, and will seek out the Ward and Brownlee book, but my general knowledge of astronomy lead me to the conclusion that we really are the result of a series of seemingly random astronomical events (e.g. local supernova providing our solar system with heavy metals, large rocky moon, jupiter as the great comet hoover). The chances of sentient complex life are even less if you consider that our own species has only been out of the trees/oceans for a galactic blink of an eye.

I like to think there is someone else out there, but I'm fairly confident they're not in the neighbourhood.

Still, my realist outlook does not hinder me from enjoying a good story.


----------



## areader (Jul 23, 2007)

I think the whole rare earth idea is spot on. I looked into it about two years ago...haven't read the book. There are a few seemingly 'earthlike' planets out there: size, proximity from the sun, similar solar system...scientists are on the hunt. They make interesting reading if you are looking for comparisons or how close we can find a match (I came across three that they were looking at, but were unsure of.) Perhaps not life as we know it *grin*. One of the offshoots is the planet classification debate that resulted in some changes within what we accept as a planet within our own solar system. And a more than keen look at Mars.


----------



## Dave (Jul 23, 2007)

I've not read that book, but I totally agree that the conditions and circumstances that made it possible for us to exist here are extremely unusual and rare. It's a big universe, so maybe they could be replicated somewhere, but it seems unlikely that we would be able to contact that life over that kind of distance. 

Of course, there is that possibility of "life, but not as we know it, Captain". There is also the possibility that life on Earth was seeded by viruses from space.


----------



## The Ace (Jul 23, 2007)

I see the mediocrity hypothesis as being the more optimistic, but we're still groping in the dark.

  We have one theory that states we are on the verge of tripping over intelligent life and another which tells us that this will never happen.   Both are probably flawed and I feel that the answer lies somewhere in between.

In short, until we have more information, I think I'll keep an open mind.


----------



## chrispenycate (Jul 23, 2007)

My opinion? You can't generalise from a single example. It is quite likely, but stating categorically "the edgesof a galaxy will be metal poor" or "there will be enough cosmic radiation to prevent the developement of lif (as we know it, but they don't state that; multicellular life will onle develope on a stony planet , in the temperature zone where water is a liquid, where the balance between carbon and oxygen is such as to make free oxygen available, where there is enough ionising radiation to encourage mutation but not enough to menace continuity…ie somewhere humans could colonise, and likely to produce species we could shake hands with.
But even looking at Earth, where we know there is life (even if the existance of intelligence is sometimes questioned) the range of environments colonised is impressive, and we haven't even  explored the rest of the solar system yet, let alone the nearer stars; and this generalises about te entire galaxy, indeed, galaxies in general.
Gertainly, we're unlikely to have much to say to an organism evolved in the atmosphere of a gas giant, but personally, I don't communicat much with mosquitos, either. It would mean a lot just to know they exist (no, not mosquitos; those I can guarantee)
As a convining explanation it ranks right up there with the proof no chemical powered rocket could achieve escape velocity.


----------



## ice.monkey (Jul 23, 2007)

It seems bizarre to waste your time 'researching' this hypothesis. The layman in the street seems to have a better grasp on this subject than Peter and Donald. We just don't know as there's nowhere near enough evidence to support any kind of claim as to how much intelligent life there is in the universe. It's obvious that you've got the two ends of the spectrum where either life is very rare or it's very common. And then you've got the inbetween. To sit down and write a book about one extreme end based on the extremely limited understanding and actual, factual evidence we have of this universe and life within it just strikes me as an assinine thing to do.


----------



## matt-browne-sfw (Jul 23, 2007)

Thanks, everyone. I'm new around here, so this was my first new thread (finally approved and not considered spam by the moderators).

I think that some of the factors in the Drake equation were too optimistic. So perhaps instead of millions of planets in the Milky Way with intelligent life there is just one: Earth. However, if 1 out of say 500 galaxies features planets with intelligent life on it, that's still a large number of intelligent species.

Before we knew more details about Mars there were a lot of science fiction stories about canals or little green men. This changed later. In Star Trek (which is mostly limited to our home galaxy) there is an abundance of M class planets with breathable atmospheres (also a production cost issue of course), but as science progresses science fiction should perhaps reflect that and keep up with more modern scientific findings... We would find plenty of bacteria but rarely any worms, fish or birds...


----------



## dustinzgirl (Jul 23, 2007)

Well, here's my ideas (and gully, its so not random, way to perfect to be random)

First off, if complex life is rare, its a massive unending universe we haven't even begun to explore, so rare could mean anything from no other life besides us to millions of other lifeforms. Its a little arrogant to think that life could only occur on Earth, with Earth's conditions, when the universe is so big that many believe it is unlimited in space and time.

Secondly, if humans are the best example of complex life in our universe, then its a sad, sad littel universe. 

Me, I'm holding out for some Autobot action.


----------



## gully_foyle (Jul 24, 2007)

dustinzgirl said:


> Well, here's my ideas (and gully, its so not random, way to perfect to be random)



Agreed. Random is probably the wrong word, but maybe randomized is more correct. I am a supporter of the theory that our current version of the universe creates the conditions that are right for life to take a hold. I think that the existence of life on our planet is probably the result of the convergence of several factors that are necessary for life to occur. I agree with Spock, that 'life will find a way'. Life is probably very common in the universe.

But.... The universe is very big. Very very big. Even our little galaxy is pretty large. There may be life on Mars, but it is either hiding well or it is not complex. And I think it is not complex because Mars does not have, and has not had, the right conditions for complex life. The chances of finding the right conditions in our neck of the woods, to me, seem pretty slim.

And Dusty, there are some beautiful humans out there that make me realise it is not all bad on our little ball of iron and water.


----------



## mogora (Jul 24, 2007)

Well, in a way this book reminds me of a quote from Douglas Adams concerning a sentient puddle of water.  The water is sure the hole it resides in was designed (or in this case, so exceedingly rare it must be unique) because it fits so perfectly...

We have no other data point than the Earth so far and it seems to me that trying to draw conclusions about the universe at large is a case of reaching your conclusion first and then fitting the arguments to it.  

What we do know is that our methods of extra-solar planetary detection can so far only detect solar systems very much unlike our own (and so that's just what we are finding).  We know that life exists in extremely inhospitable places on this planet.  We know that our type of intelligence took a long time to evolve.  What this all means for other planets is unknown.  All we can do is look.


----------



## Dave (Jul 24, 2007)

mogora said:


> Well, in a way this book reminds me of a quote from Douglas Adams concerning a sentient puddle of water.  The water is sure the hole it resides in was designed (or in this case, so exceedingly rare it must be unique) because it fits so perfectly...


While that is very funny, I don't think it's a good analogy. In fact those high surface tension properties of Water as a liquid, along with liquid Water's other very unusual properties only go to illustrate the opposite point further. Water is only liquid at a very small range of temperatures.

I agree that as we haven't yet left our Solar System, we may be making huge assumptions, but the physical and chemical properties of Matter will hold true everywhere. The availability of elements essential for life, such as Carbon and Oxygen, will be the influenced by the same factors.

Then there is the possibility that intelligent life has found us already, but left us well alone. I know I would!


----------



## HardScienceFan (Jul 24, 2007)

http://prelude.bu.edu/publications/Raymond_Segre_Science_2006.pdf

http://prelude.bu.edu/publications/Shenhav_Segre_Lancet_ACS_2003.pdf
http://prelude.bu.edu/publications/Segre_etal_SPIE_1999.pdf
http://www.gps.caltech.edu/~jkirschvink/pdfs/MarsOriginofLifeFinal.pdf
http://rpi.edu/dept/chem/chem_faculty/profiles/pdfs/ferris/Royal_Soc..pdf
Mary Ann Liebert, Inc. - Cookie absent
http://arxiv.org/PS_cache/astro-ph/pdf/0602/0602008v1.pdf


----------



## matt-browne-sfw (Jul 25, 2007)

dustinzgirl said:


> Its a little arrogant to think that life could only occur on Earth, with Earth's conditions, when the universe is so big that many believe it is unlimited in space and time.



There seems to be a misunderstanding. The two authors do not claim that complex life / intelligent life can occur only on Earth. What they are saying is that complex life / intelligent is rather rare than frequent, while simple life could be rather abundant.

Again, instead of thousands of humanoid species in the Milky Way (as portrayed in the Star Trek universe) it might only be a few or just one (us). The authors acknowledge that in other galaxies there might be complex life also. Scientists think that there are at least 100 billion galaxies in the universe...


----------



## Moogle (Jul 25, 2007)

Well put simply it sounds like a lot of things we've heard about before.

Take for instance those who theorized (and I don't know any names, but I'm sure there were a few) that life could not exist in the deep ocean because the pressure was too great. Or that life cannot not exist in the darkest caves because there is no light. There is life in the deep oceans and in the darkest caves, our planet is literally teeming with life in every little nook and cranny! Granted nothing on this planet has evolved into a state that we would classify as "sentient", except perhaps Dolphins? 

There you have it right there, how do we classify intelligence and sentient? How can we possibly know what an alien species considers to be sentient? Perhaps it's utterly possible that extra-terrestrial sentients have already visited us and yet deemed us NOT up to their standards of sentience. Or maybe they couldn't recognize our sentience by their own standards?

Life, to me, seems to be able to adapt to almost anything. For all we know, for all our technological prowess and ingenuity, it's quite possible that there are other sentient life-forms within our own solar system that we just can't even fathom as being life at all! Maybe the planets themselves are sentient on a level that we will never be, maybe we are unique... as parasites on an intelligent orb.

The beauty of hypotheses like this one, is that we define the parameters in what we call intelligent life. Basically if it can't contact us, it doesn't matter eh?


----------



## matt-browne-sfw (Sep 23, 2007)

Moogle said:


> Well put simply it sounds like a lot of things we've heard about before.
> 
> Take for instance those who theorized (and I don't know any names, but I'm sure there were a few) that life could not exist in the deep ocean because the pressure was too great. Or that life cannot not exist in the darkest caves because there is no light. There is life in the deep oceans and in the darkest caves, our planet is literally teeming with life in every little nook and cranny! Granted nothing on this planet has evolved into a state that we would classify as "sentient", except perhaps Dolphins?
> 
> ...



I totally agree about your views on the difficulty of defining intelligence. The Rare Earth Hypothesis however is about the issue of complex (also unintelligent complex) life and simple life (your examples of extremophiles fall into this category).


----------



## Delvo (Sep 23, 2007)

matt-browne-sfw said:


> In Star Trek (which is mostly limited to our home galaxy) there is an abundance of M class planets with breathable atmospheres (also a production cost issue of course), but as science progresses science fiction should perhaps reflect that and keep up with more modern scientific findings... We would find plenty of bacteria but rarely any worms, fish or birds...


There would be little reason for humanoid characters to go to a planet of nothing but extremophiles.

And remember not to mix up "abundance" and "frequency". The Star Trek world has the galaxy divided into quadrants (fourths), with all of our major players coming from some part of one of them, so let's call it half of the quadrant, which is an eightth of the galaxy. Dividing that up into fifths to roughly follow the political divisions (Federation, Romulan, Klingon, Cardassian, Everybody Else) gives somewhere around a fortieth of the galaxy to each major political unit. What did they say is in the Federation, 150 planets (so probably fewer than that number of sentient/sapient species), or 150 species (so probably more than that many planets)? Either way, each of those 150 species or planets, being a hundred-&-fiftieth (1/150) of a larger group which itself constitutes a fortieth of the galaxy, would have one six-thousandth of the galaxy to itself... a sixth of a thousandth... a sixtieth of one percent... that's a pretty small fraction, right? But in a galaxy of a hundred million stars, that's still 16,667 stars apiece.


----------



## Ursa major (Sep 23, 2007)

In a vast observed universe (and there's no telling how big the _actual_ universe is, or whether there's a mulitiverse), rare can be no more than a relative term. And so, apart from ecomomic reasons, there's little point in books like this; I suppose the best that could be said of them is that they're very hard, non-narrative SF that merely claim to be ("popular") science.

As to what other life may be like, it's hard to say. I'm sure there are many evironments where only microscopic life can exist; once there is a possibility of multicelled life, though, there's no end to what may be there.

It's a while since I read *Wonderful Life* by Stephen Jay Gould, but what I do vaguely remember is the number of _types_ of life existing 600 million years ago, only a few of which have so far been found to exist at the current time. It seems that the kind of life we're used to (based on DNA, RNA and all the various bits and bobs that are rarely mentioned) is capable of great diversity. If it turns out that the likelihood of coming up with something analogous to DNA and its support structures is very small, then _any_ sort of life will be scarce. If, however, this likelihood is not so small, then there ought to be many habitats teeming with a variety of life-forms.

Whether any of these would be intelligent, who knows? The jury is still out for this world.


----------



## matt-browne-sfw (Sep 28, 2007)

Ursa major said:


> If it turns out that the likelihood of coming up with something analogous to DNA and its support structures is very small, then _any_ sort of life will be scarce. If, however, this likelihood is not so small, then there ought to be many habitats teeming with a variety of life-forms.



The authors assume that DNA or DNA-variants are widespread across the universe (for whatever reasons like frequency of certain complex molecules in space, panspermia). And since extremophiles on Earth demonstrate their resilience, extremophile-like organisms should be widespread. However, they claim that almost never will evolution lead them successfully to complex life like insects or fish.


----------

