Rare Earth

Tal Cohen writes: "It is said that one of the most important skills a physicist needs is the ability to quickly make "back-of-the-envelope" calculations. For example, Jan Wolitzky (in Jon Bently's "Programming Pearls") tells about Enrico Fermi, Robert Oppenheimer, and the other Manhattan Project brass who were behind a low blast wall awaiting the detonation of the first nuclear device from a few thousand yards away. Fermi was tearing up sheets of paper into little pieces, which he tossed into the air when he saw the flash. After the shock wave passed, he paced off the distance traveled by the paper shreds, performed a quick "back-of-the-envelope" calculation, and arrived at a figure for the explosive yield of the bomb, which was confirmed much later by expensive monitoring equipment." Read on to find out what this has to do with the unusual characteristics of Earth, and how they could influence our search for life elsewhere in the universe. Rare Earth: Why Complex Life is Uncommon in the Universe author Peter D. Ward, Donald Brownlee pages 368 publisher Copernicus rating 7 reviewer Tal Cohen ISBN 0387987010 summary Maybe we are alone, after all.

But expensive monitoring equipment which can confirm the calculation does not always exist, and hence in some fields, our entire knowledge is based on back-of-the-envelope calculations and rough estimates.

Take, for example, the following question: "How many intelligent civilizations, capable of radio communications, currently exist in the Milky Way galaxy?". The worthwhileness of search projects (such as SETI) is closely related to the answer to this question. The number of positively known civilizations is exactly one: the human civilization. And yet, many scientists believe, or at least believed until recently, that the actual number is far, far higher.

This belief was based on various estimates, such as the calculation proposed by Frank Drake, now known as "The Drake Equation." This equation was popularized in Carl Sagan's remarkable TV series, "Cosmos". Sagan himself believed the calculation's result, and was one of the founders of SETI.

Drake's equation is easy to understand. Take the number of stars in the galaxy (about 200 to 300 billion, based on generally accepted estimates), and multiply it by: the percentage of stars that are similar to our Sun in the energy output and stability; the percentage of stars that have planets (since not every star has any); the percentage of planets orbiting their star in a proper distance (so they could hold liquid water, a necessity for maintaining life); the percentage of planets with liquid water on which life actually evolved; and finally, the percentage of life-bearing planets in which intelligent civilizations (i.e., those that can communicate by radio) eventually came to be. All in all, there are five or six factors in this product.

(Note: In my own copy of the book (2nd impression), page 267 states that "a good estimate for the number of stars in our galaxy [is] between 200 and 300 million" - one letter misspelled, and wrong by three orders of magnitude. I do hope the authors' actual calculations were based on the correct value.)

But what values should be used for the various percentages? Drake (and Sagan) chose what they considered to be a conservative approach, and estimated that only about 1 in 10 stars has any planets; only 1 in 10 planets is in the proper orbit, and so forth. Despite the conservative approach, the results were encouraging, indicating that there are thousands of intelligent civilizations in the Milky Way, and probably millions of them in the whole universe. Thus they concluded that there is intelligent life out there, in all likelihood; now we only have to look for it.

In their book Rare Earth, published by Copernicus Press in 2000, Peter Ward and Donald Brownlee point at Drake's (and other physicists') mistakes in a long and depressing discussion, a discussion that took the wind out of more than one SF author's sail.

The book presents what the authors call "the rare Earth hypothesis": simple (bacterial) life is very common in the universe; complex life (multi-cellular life forms, or animals -- let alone intelligent life) is very rare. The first part of the hypothesis is easy to understand, and few scientists will argue with it: indications of simple life were already discovered on rocks originating on Mars, and even here on Earth in conditions that were, until recently, considered completely hostile to life (such as temperatures higher than 100 degrees Celsius, in which 'extremophile' bacteria were found to exist). The second part is the interesting one, and it suggests that the existence of simple life does not necessarily lead to the evolutionary development of complex life, for any number of reasons.

Drake's mistake was basically in the assumption that all it takes for a planet to develop life is being in the proper distance from a proper star. The truth, Ward and Brownlee suggest, is that we have to look at each and every attribute of Earth, and re-estimate its importance for supporting life. Drake's equation is a statistical calculation, but with no other example for life, we're doing statistics with N=1.

Well then, what are the special attributes of Earth that we have to take into account when attempting to run this calculation?

• Proper distance from the star. If a planet orbits its sun too closely or too far away, liquid water would not exist. There isn't much margin for error here: a change of 5 to 15 percent in Earth's distance from the Sun would lead to the freezing, or boiling, of all water on Earth.
• Proper distance from the center of the galaxy. The density of stars near the center of the galaxy is so high, that the amount of cosmic radiation in that area would prevent the development of life.
• A star of a proper mass. A too-massive star would emit too much ultra-violet energy, preventing the development of life. A star that is too small would require the planet to be closer to it (in order to maintain liquid water). But such a close distance would result in tidal locking (where one face of the planet constantly faces the star, and the other always remains dark -- as with the moon in its orbit around Earth). In this case one side becomes too hot, the other too cold, and the planet's atmosphere escapes.
• A proper mass. A planet that is too small will not be able to maintain any atmosphere. A planet that is too massive would attract a larger number of asteroids, increasing the chances of life-destroying cataclysms.
• Oceans. The ability to maintain liquid water does not automatically imply that there will be any on the planet's surface. It looks like Earth acquired its own water from asteroids made of ice that crashed here billions of years ago. On the other hand, too much water (i.e., a planet with little or no land) will lead to an unstable atmosphere, unfit for maintaining life.
• A constant energy output from the star. If the star's energy output suddenly decreases, even for a relatively short while, all the water on the planet would freeze. This situation is irreversible, since when the star resumes its normal energy output, the planet's now-white surface will reflect most of this energy, and the ice will never melt. Conversely, if the stars energy output increases for a short while, all the oceans will evaporate and the result would be an irreversible greenhouse-effect, preventing the oceans from reforming.
• Successful evolution. Even if all of these conditions hold, and simple life evolves (which probably happens even if some of these conditions aren't met), this still does not imply that the result is animal (multi-cellular) life. The evolution of life on Earth included some surprising leaps; two worth mentioning are the move from simple, single-cellular life to cells which contain internal organs, and the appearance of calcium-based skeletons. It appears like the first of these leaps took more time than the evolution from complex single-celled life to full-blown humans.
• Avoiding disasters. Any number of disasters can lead to the complete extinction of all life on a planet. This include the supernova of a nearby star; a massive asteroid impact (like the one that probably caused the extinction of dinosaurs, and 70% of all other life-forms at the time); drastic changes of climate; and so on.

There are also a few attributes that seem, at first, to be completely unrelated to life and not required for its development. Ward and Brownlee argue strongly for the importance of the following attributes:

• The existence of a Jupiter-like planet in the system. Apparently, Jupiter's large mass attracted many of the asteroids that would have otherwise hit Earth. Could life evolve in a system with no Jovian planet? On the other hand, too many Jovian planets, or one that is too large, could lead to a non-stable solar system, sending the smaller planets into the central sun or ejecting them into the cold of space.
• The existence of a large, nearby moon. Luna, Earth's moon, is atypically large and close. Both of Mars's moons, for example, are minor rocks by comparison. What does this have to do with life? Well, it turns out that Luna kept (and still keeps) Earth's tilt stable. Without Luna, the tilt would have changed drastically over time, and no stable climate could exist. If the tilt would have stabilized on a too-large or too-small value, the results could also be disastrous; Earth's tilt is "just right."
• Plate tectonics. Surprisingly enough, it seems like plate tectonics are required for maintaining a stable atmosphere. Plate tectonics play an important role in a complex feedback system (explained in detail in the book) that prevents too many greenhouse gases from existing in the atmosphere. No other planet (except maybe for Jupiter's moon Europa) is known to have plate tectonics. Is this a rare phenomenon, but required for life?

The bottom line is that many additional factors must be added to Drake's equation. One must keep in mind that as any term in such an equation approaches zero, so too does the final product. For most terms, we have no way of reliably estimating their true value, but it seems like at least some of these values are extremely low.

Two important things should be noted about this book. First, about what it does not contain: although I am sure many people will see the Rare Earth Hypothesis as another proof for the existence of a god, this notion of a proof is completely unrelated to the authors' ideas. The hypothesis claims that the conditions for creating complex life are rare; but we know for a fact that at least in one case, all the required conditions were met. Additionally, anyone who insists on taking the ideas of this book as a proof for god's existence will also have to accept the authors' prepositions about the age of the universe, the age of planet Earth, and more importantly, the theory of evolution.

Second, about what the book does contain: the book discusses at length all the issues I've listed above, and more. The problem is that sometimes one gets the feeling that these issues are discussed in too much detail, and the authors tend to repeat themselves, or to delve too deep into some of the less-important aspects of their theory. This is certainly not your common popular-science book; it relies on very up-to-date research results (including some results that were not even published when the book went to press). The writing gets technical on many points in astrophysics, biology, chemistry, and geology (as well as the new field of astrobiology, of course). Over 25 pages of bibliography and references are included.

The theory's weakest point, however, is obvious. The authors admit (after 281 pages of discussion) that their base assumption was that every complex life-form would be similar in many ways to life on Earth: "We assume in this book that animal life will be somehow Earth-like. We take the perhaps jingoistic stance that Earth-life is every-life, that lessons from Earth are not only guides but also rules. We assume that DNA is the only way, rather than only one way" (p. 282).

For me, reading this book was a fascinating and awe-inspiring experience. The most important conclusion (apart from SETI being a huge waste of resources) is an unavoidable cliché, which the authors avoided presenting directly, even though it stares into the reader's face from every page and each paragraph: What we have here is rare, maybe even unique. We should try a little harder to make sure it survives.

Post Scriptum: A news item in the November/December 2001 issue of the Skeptical Inquirer (Vol. 25, No. 6) states that "David Darling, an astronomer who is a critic of the Rare Earth hypothesis, has revealed that one of the strongest influences on the authors, a young [...] astronomer who they acknowledge in their preface 'changed many of our views about planets and habitable zones', has a hidden, Earth-is-unique agenda motivated by strong 'intelligent design' religious views." That astronomer, Guillermo Gonzalez, published several articles in Connections, a quarterly newsletter published by Reasons to Believe, Inc. In one of these articles, co-authored with the creationist scientist Hugh Ross, Gonzalez writes: "The fact that the Sun's location is fine-tuned to permit the possibility of life [...] powerfully suggests divine design."

Darling published these findings, along with a detailed point-by-point scientific critique of the Rare Earth hypothesis, in his book Life Everywhere: The Maverick Science of Astrobiology . Skeptical Inquirer quotes Darling as saying, "What matters is not whether there's anything unusual about the Earth; there's going to be something idiosyncratic about every planet in space. What matters is whether any of Earth's circumstances are not only unusual but also essential for complex life. So far we've seen nothing to suggest there is."

For more about this book, please see this page. For additional book reviews, please visit Tal's bookshelf. You can purchase Rare Earth from bn.com. Want to see your own review here? Just read the book review guidelines, then use Slashdot's handy submission form.

Comments

Another factor?

[the_consumer]

How about the magnetic field of the earth? Is it known yet whether most other earth-like planets have as intense a magnetic field, or is this property rare as well? I understand that the surface of our planet is shielded from a lot of bad radiation by the magnetic field.

Re:Another factor?

[Steve B]

Earth's magnetic field rises, falls, and reverses quite often (on a geological timescale). This makes it unlikely that it's terribly critical for the continued existence of life, since the periods of near-zero field are long (on the timescale of human, to say nothing of other critters', generations).

Re:Another factor?

[Alien54]

How about the magnetic field of the earth?

If you have a large enough rock, the compression and radioactivity in the core will kept the core molten. This combined with the spin of the planet will generate as rotating mass of metal. This, with other factors, is generally enough to get a magnetic field going. So, with a big enough planet, you get the whole deal, magnetic field, gravity, sustained atmosphere, etc.

Yes, the core is radioactive to some degree.

I suspect that part of the problem with Mars is that the core cooled down, shutting down plate techtonics before it really had a chance to get going well.

If Mars took, say, 4 billion years to cool down, since the Earth is roughly twice the diameter, it will take about 8 times as long to cool off. We have plenty of time.

Re:Another factor?

[Simon Hibbs]

Well, as we know from the excelent classic film "Daleks - Invasion Earth", a planetary magnetic field is essential to preserve indiginous life forms from conquest by Dalek forces.

How this important factor has been overlooked by so-called serious scientists is a mystery to me.

Simon Hibbs

Re:Another factor?

[mcfiddish]

I understand that the surface of our planet is shielded from a lot of bad radiation by the magnetic field.


The atmosphere blocks most of the bad radiation. The magnetic field deflects energetic particles, which are mostly from the solar wind. Even if we didn't have a magnetic field, the atmosphere would block those too; only uncommonly energetic particles would make it to the ground.

A magnetic field is important over long timescales as it protects the atmosphere from the solar wind. Without it, the atmosphere would be slowly eroded away.

Re:Another factor?

[GunFodder]

The proportion of metal in a planet should relate to the relative age of the star it orbits and the distance from this star. Older stars formed from primordial hydrogen and are therefore relatively poor in heavy elements. Newer stars contain more heavy elements created in the supernovas in old stars.

Closer planets get more solar energy and are therefore hotter than farther planets. This heat gives lighter elements like hydrogen the necessary energy to escape from the atmosphere, leaving behind the heavier elements to dominate the planets composition.

That said, most stars that are similar to the sun in mass will be no more than 4 billion years older or younger than our Sun. This should lead to a similar proportion of heavy elements. And since the distance requirements for an Earth-like planet are so precise this is unlikely to be a factor. So a similar metal core is almost a given.

The problem with all these equations...

[bravehamster]

is that they assume that any life that develops will be similar to us in basic body chemistry, and thus have the same requirements to develop. That's a huge assumption on our part. There may be forms of life out there that have nothing to do with amino acids or DNA or even liquid water. We really know nothing about the basic processes of life and how it develops. All we know is how we developed, and from there we assume that anyone else has to develop in the same way. If we just admit that we don't know what the hell we're looking for, we'll find a lot more than we will if we focus on terrestial planets in an earth-life orbit, 3/4 the way towards the edge of the galaxy. We need to keep our eyes and ears open and not make any assumptions about what we'll find out there.

Re:The problem with all these equations...

[taliver]

I'm so glad I clicked reload before making this exact comment.

One additional thing, however, if what we even consider to be alive. Andromeda Strain really piqued by interest when one of the scientists showed a watch, a lit candle, and a rock, and claimed that each could be considered alive (the rock is just moving very slowly, the flame certainly has all the proper characteristics).

I'm betting we'll end up calling anything "alive" if we can't predict it's future behavior exactly. This would also mean that once we understand simple cells, we might not consider them "alive" anymore.

Re:The problem with all these equations...

[Rupert]

I agree. The odds of "another earth" - a planet so strikingly similar to ours that it would be amazing if intelligent humanoid life *didn't* develop - are so low that N=1 is a reasonable assumption. However, we know so little about the possible environments in which intelligent life can develop (because our sample size is one), it is not possible to assert that this is the actual result of the Drake equation.

Re:The problem with all these equations...

[mikeee]

It's not that big an assumption. Sure, anything is possible, but:

Water is common and a great solvent for organic (carbon-chain) molecules.

Carbon-based compounds are really the only ones that form huge, complex molecules.

More important, if there are all these aliens out there, why haven't they visited us? Either

a) They can't. (starships impossible)
b) Nobody wants to. (Prime directive, or 'They're made of meat!')

And the earth's moon is certainly freakish; it appears to be the result of an *astoundingly* unlikely collision with a large body at just the right angle. It seems more plausible to me that such a moon is necessary for life than that our planet just happens to be a billion-to-one oddity, especially (as noted above) given the lack of flying saucers.

Re:The problem with all these equations...

[bravehamster]

More important, if there are all these aliens out there, why haven't they visited us? Either

a) They can't. (starships impossible)
b) Nobody wants to. (Prime directive, or 'They're made of meat!')

I think far more likely is:

c) They don't think anyones here, because they assume nothing could live in a atmosphere full of such a corrosive poison gas as oxygen.

It's quite possible that they've checked our solar system out and dismissed it, because they had their own "Drake Equation". Maybe they also are working from a dataset of 1 and assume that life must develop like them.

Re:The problem with all these equations...

[the_consumer]

There's another option both of you are overlooking:

d)Not only have they visited us, but they are us!

Re:The problem with all these equations...

[mikeee]

They wouldn't be confused about that for that long.

Anybody near to our solar system could hardly fail to notice us. If they saw the oxygen in our atmosphere, they'd notice the radio waves, too, if not also the nighttime lighting! That would at least be considered an interesting natural phenomena to check out.

And remember, the galaxy is billions of years old; if you're assuming thousands of civilizations, many of them will be millions of years older than us. They've had time to get here with *non-FTL* ships and for that matter colonize the whole galaxy.

Either it can't be done, or nobody wants to for some reason. Or there's nobody to do it.

(Or, alternately, advanced life is common but we just happen to be the first....)

Re:The problem with all these equations...

[bluGill]

I've always favored a slihgtly different answer: We are the first. that is the universe is billions of years old, but the average lenght of time for intellegence to come about is trillions of years. It happens that we got there first, and we will die out, after leaving lots of artifacts for future archiolgists to study. Today there is only one civialization in the universe, and we will likely die out before the next comes even close, but eventially there will be many different ones out there. Eventially they all die out, and sometime, latter that will be a finial lone civializtion that is just starting to study the remains of the previous when the universe completely loses the ability to support life. (over thousands of years...)

Of course the above depends on some assumptions that I don't nessicarly agree with. still I like to think that sometime. If nothing else it gives me more want to build quality. I can just see archiologists saying "Look, this anchient civialization built to last, here is this radio trillions of years old still in working order that can communicate with our home planet. too bad it is at slower than light speeds, and thus useless. (Yeah, I know it is unlikely, but it sounds good)

Re:The problem with all these equations...

[xtal]

There may be forms of life out there that have nothing to do with amino acids or DNA or even liquid water. We really know nothing about the basic processes of life and how it develops. All we know is how we developed, and from there we assume that anyone else has to develop in the same way.

How much organic chemistry did you take? I would bet dollars to donuts that ANY life in the whole entire universe - at least, "naturally" occuring life and not an artificial intelligence created by something which is itself alive - is based on organic chemistry. Carbon is a very, very special atom. I read a quote once that stated life may one day be reclassified as a property of the carbon atom, because carbon and carbon alone can form long polymer chains. These chains are needed for forming DNA and encoding the infomation that makes you who and what you are. There is no other mechanism in the natural world for doing this, and if you were to propose one, you would likely get a nobel prize.

We evolved out of the same matter and same periodic table as everything else in the universe might. If you showed an alien a periodic table, they'd probably know right away what it was. Organic chemistry is unique, and life is enexoriably tied to it's ability to spontaneously form long, complex chains. Not life as we know it. ALL natural life. There is no other atom with the same characteristics. Period. The fact our brains can flexibly reconfigure themselves is a property that organic chemistry enables, and is absolutely necessary for intelligence and learning.

Now, that rant completed, it is also likely in the grand scheme of things, carbon based life is a step in making more complicated artificial life forms that are based on more efficient information processing which cannot naturally develop - for example, within the guts of a bank of FPGA circuits. People like to think what we do is outside nature, but everything we do - destructive, constructive, or creative - is part of a natural process, too. So perhaps the moniker artificial intelligence isn't so good.

That said, please think before you say life elsewhere would need the same requirements. Would life be different? Absolutely. But IMHO it'd be based on DNA or a similar encoding structure; and it would certainly absolutely require the prescence of water. Those are two characteristics all life - from bacteria in the crust, to hydrothermal vents. Water and Carbon.

Re:The problem with all these equations...

[the phantom]

In that case, you have done quite well.

I was raised in a family of anthropologists, and I am now pursuing a degree in archaeology. Back in the day, I was given Chariots of the Gods by my parents. Basically, they said "If you every do any thing like this, we will disown you." Anyway, the book is fun as fiction, right?

Re:The problem with all these equations...

[benwaggoner]

Of course, the big problem with the "Earth's life was seeded from Beyond the Stars!" is that it begs the question of how the life that seeded us evolved. It'd be interesting to know, but wouldn't answer any fundamental questions.

Of course, the same could be said about Intelligent Design arguments. "So, where did God come from, and why did he want to create life? Would other possible gods have behaved differently? And why are you building that man-sized bonfire, and walking towards me with that rope?"

Re:The problem with all these equations...

[rho]

is that they assume that any life that develops will be similar to us in basic body chemistry, and thus have the same requirements to develop. That's a huge assumption on our part.

I would suppose that this is because to go the other direction leads to a teflon-covered slope of "maybe ifs"--"Maybe if life was silicon based", "Maybe if life encoded genetic information in a single helix", "Maybe if life was based on tapioca pudding and whipped cream".

What kind of life do we know? Pretty much the carbon-based life here at home. What other kinds of life are out there? It's probably best not to start guessing.

T(H)GSB

Re:The problem with all these equations...

[km00re]

It's also possible that we are the most advanced civilization to develop so far. How's that for a depressing thought?

Re:The problem with all these equations...

[Kintanon]

Hmmm, my opinion would be that Occam's razor cuts the other way. The simplest solution is that if it happened once, it will happen again. There is no such thing as a completely unique event (Or the opposite, every event is completely unique, which is really the same thing) hence the occurance of intelligent life on earth must be replicated somewhere else in the universe given that the number of possibilities of that occurance approaches infinity.
Intelligent Life other than us is almost certain, when and where, that's the mystery.

Kintanon

Re:The problem with all these equations...

[Kintanon]

Sample size is equal to this planet and life on this planet. This is not necessarily indicative of the chemistry of every other planet in the universe. We by no means have catalogued every element that exists and there's nothing to say that some element we discover in the future won't be capable of everything Carbon can do and more.

Kintanon

Re:The problem with all these equations...

[GMFTatsujin]

We are the first. that is the universe is billions of years old, but the average lenght of time for intellegence to come about is trillions of years.

So what you're saying is either that we're older than the universe, or that we still have billions of years to go before we achieve true intellegence?

One of those possibilities, I'm ready to believe... :)

GMFTatsujin

Re:The problem with all these equations...

[renard]

We by no means have catalogued every element that exists

On the contrary, we most certainly have (I suggest you check out an encyclopedia entry on "nuclear physics" if you doubt this). The only elements yet to be discovered will have half-lives measured in microseconds, at best... not exactly conducive to life, liberty, and the pursuit of happiness.

Sample size is equal to this planet and life on this planet.

In terms of life, yes (so far...). In terms of chemistry, no. We are not limited to our own creativity here: radio astronomers routinely detect the signatures of organic (carbon-based) molecules in interstellar space.

If there were any new sorts of molecules out there, they would give unusual radio emissions that would be of great scientific interest... we have yet to see any such evidence.

-Renard

Re:The problem with all these equations...

[Kintanon]

If there were any new sorts of molecules out there, they would give unusual radio emissions that would be of great scientific interest... we have yet to see any such evidence

This is still based only on the size of the area we can scan, which has just recently begun to reach beyond our own galaxy. And we aren't even able to take a close look at our own galaxy yet. We are also limited by our scanning methods. There is still an entire universe of near infinite capacity that we haven't even begun to get data on, don't go ruling everything out just yet. After all, if we're at the limit of all natural chemistry and physics we're pretty much confined to this planet completely, aren't we?

Kintanon

Re:The problem with all these equations...

[shawnseat]

I would bet dollars to donuts that ANY life in the whole entire universe - at least, "naturally" occuring life and not an artificial intelligence created by something which is itself alive - is based on organic chemistry....

You're right so far.

I read a quote once that stated life may one day be reclassified as a property of the carbon atom, because carbon and carbon alone can form long polymer chains.

Not really. It's very well known that silicon and oxygen together (in -SiOSiO- links) can form high polymers as well. However, the silicons need two more bonds, and invariably the atoms the Si bond to are carbon atoms.

The much weirder example of something that concatenates readily are metal atoms (especially in liquid ammonia). In NH3, one MIGHT conceive of a redox system that has various "living" metal clusters interacting, and solvated electrons would be the general reducing agent. This is the only system I can imagine that would permit a totally non-carbon life to occur (and high metals are much rarer than carbon in the cosmos, which makes this even less probable).

Re:The problem with all these equations...

[Kintanon]

And sometimes the answer is "Try Harder".

Kintanon

Re:The problem with all these equations...

[TMB]

Actually, the biggest problem here really struck me when I was at a colloquium that Peter Ward gave. The talk itself was interesting. During questions, one of my colleagues asked the obvious question: What are the expected correlations between these additional factors? To take one example, having a large moon and having active plate techtonics for a long time are certainly correlated. So while each of these factors may be very small, how much does finding a planet that satisfies one of them improve the chances that it will satisfy the others?

His response was essentially to shrug it off and say "we don't expect that there are any important correlations." Whereas it ought to be the most important question!

So I would say that while they bring up some interesting things that people need to be thinking about, their attitude makes me highly suspect of any number they try to assign.

[TMB]

Re:The problem with all these equations...

[budgenator]

probably no one want's to excluding a method of changing velocity without accelerating, relativity makes any significant space travel strickly one-way, millions of years would pass back home.

any one who did would have to stop periodicaly to reprovision, make hostile contact if other life already existed there ala indepenance day.

I suppose that you could turn a solar system into a bussard ram ship and actualy go some where by building a ring world arround your star, but if you have to drag a whole solar arround with you, why bother, anything you were trying to escape would be dragged along with you

Re:The problem with all these equations...

[budgenator]

Actualy we even knew where the elemants that we had'nt discovered would be in the periodic table and enough about there properties that we could predict what they would be like so we could recognise them when we did.

silicon is the only element that even come close to carbon versatility in make polymer chains any life form that uses silcon would only have a smaller percentage in it's polymerchains; they'd still be mostly carbon based.

hmm. not sure about this...

[PsiPsiStar]

>If a planet orbits its sun too closely or too >far away, liquid water would not exist. There >isn't much margin for error here: a change of 5 >to 15 percent in Earth's distance from the Sun >would lead to the freezing, or boiling, of all >water on Earth.

What about subterranian water?
The ground is constant at about 60 degrees, summer or winter. On a planet with thinner atmosphere, that water might be liquid even when surface water boiled

Re:hmm. not sure about this...

[MrGrendel]

That's exactly right. And furthermore, the "scientist" who came up with that estimate is apparently unaware of all of the planetary research that has been done in our solar system over the past 30 years. Mars is much farther from the Sun than Earth (more than 15%) and there is overwhelming evidence that it once had liquid water on the surface. Why isn't it there now? Because Mars does not have enough mass to retain a thick atmosphere. It once had a thick atmosphere and most of it evaporated into space and the planet cooled. The density and composition of the atmosphere is far more important to the temperature of a planet than its distance from a star. Just look at Venus -- it's the hottest planet by far even though it is not closest to the Sun. The dense CO2 atmosphere makes it hot and keeps it hot (the night-time temperature only falls by 3 degrees and night there lasts for over a hundred days).

Re:hmm. not sure about this...

[PsiPsiStar]

Our whole ecosystem is not based off of light. There are plenty of organisms that live near sulfur vents and metabolize the chemicals from that.

What I'd like to know is whether you can get an organism to utelize x-rays or some other shortwave light source that would be more prevalent on atmosphere-less worlds. The creature would live underground, the ground would be it's 'ozone layer' and it would be safe and snug

Fermi...

[Anonymous Coward]

should have made a few 'back of the enveloppe' calculations BEFORE sitting a few thousand yards away from a nuclear blast. And then WALKING around the blast area.

This is a sign of high intelligence?

Re:Fermi...

[Coward, Anonymous]

My grandfather was a guard at the Manhattan Project. After the test blast, he and many of the other guards took molten sand from the blast as a souveneir. There were quite a few people walking around the blast area.

Re:Fermi...

[Bearpaw]

should have made a few 'back of the enveloppe' calculations BEFORE sitting a few thousand yards away from a nuclear blast. And then WALKING around the blast area.

Um. Before the blast, there was nothing to do the back of the envelope calculations about. They'd already done whatever calculations they could've done based on the theories they had. Doing more calculations without any real data would definitely not have been a sign of high intelligence.

The clever thing was not really the caculations, it was the improvised data-gathering.

Influences, agendas shouldn't matter with facts

[stoolpigeon]

It seems interesting to me that someone critical of this idea uses the fact that they were influenced by the work of a creationist as a method of arguing against them.

What in the world does this have to do with anything?

Isn't this the very worst kind of thinking?

"You're idea can't be correct. There are other people who share this view and I don't agree with other things that they think."

Guilty by association.

Look at the argument for the argument.

Why did that deserve a footnote? I am guessing to fair warn those who might be terrified to find they had been suckered into 'agreeing' with a creationist.

The evolution/creationism debate on many fronts has devolved into a mess. There is a lack of honest exchange in favor of turning one's back to any argument or information.

Not very scientific.

Oh- and I predict this thread for the most part turns into a major conflagration.

.

Re:Influences, agendas shouldn't matter with facts

[Jbrecken]

It seems interesting to me that someone critical of this idea uses the fact that they were influenced by the work of a creationist as a method of arguing against them.

What in the world does this have to do with anything?

It calls into question the validity of the creationist's work. If a scientist has a personal agenda, he's more likely to grab a zebra hypothesis that supports his position.

Re:Influences, agendas shouldn't matter with facts

[stoolpigeon]

The idea that a person does not have an 'agenda' is preposterous when put into such broad terms.

The assertion basically is that his world-view is his agenda. You cannot live and act without some world-view. (regardless of whether or not you are conscious of it)

All human beings have basic presuppositions that they work with. In this kind of theorizing this is especially so as 90% of the work (as is mentioned in other posts) is guess work.

This guy is no more apt to 'go after' something than anyone else. And hopefully as facts come to light- those will prove of disprove his hypothesis. Opinions can influence research but they cannot change facts.

.

Re:Influences, agendas shouldn't matter with facts

[jaoswald]

A creationist has more of an agenda because he rejects scientific inquiry as a method for establishing "truth," whereas an evolutionist likely has scientific criteria for discussing whether something is true or not.

A creationist's view of evolution is that it isn't true. An evolutionist's view of creationism is that there is no reason to believe it is true, other than the belief itself. The creationist is more radical.

Skeptics, *yawn*

[mblase]

one of the strongest influences on the authors, a young [...] astronomer who they acknowledge in their preface 'changed many of our views about planets and habitable zones', has a hidden, Earth-is-unique agenda motivated by strong 'intelligent design' religious views.

So what? Science is science, and all that anyone is doing in this subject is educated guesswork. If an author or influence had a 'hidden, Earth-is-random agenda motivated by strong atheistic and humanist views,' would that make his science automatically invalid as well?

Just because someone's science is motivated by pre-existing beliefs doesn't automatically make his science bad. This is just prejudice, end of discussion.

Re:Skeptics, *yawn*

[katre]

Just because someone's science is motivated by pre-existing beliefs doesn't automatically make his science bad.

The problem here is not having pre-existing beliefs. It's having pre-existing beliefs and then using them to filter what you observe. Science is about observation. If your beliefs keep you from observing accurately, then yes, that is bad science. And when people who habitually practice bad science (yes, I'm looking at you, creationists and flat-earthers) try and horn in on other fields, it's quite justified for others to warn people to watch their science just a little bit more.

Re:Skeptics, *yawn*

[Zathrus]

Of course, Mr. Darling isn't filtering what he observes to support a non-deity influenced view, right?

Uh huh.

It goes on on both sides. I'll happily admit that I routinely dismiss highly religious people because I feel that it blinds them to what I consider fundamental truths. But I'm bet they feel the same way about atheists too.

Yes, believing in a "deity-influenced" universe means that you have put some blinders on. You will look for proofs that support your position (which is basically looking for very low percentage odds on certain things, or non-sensical behavior in creatures or systems).

By the same token, being a staunch atheist means you will look for any reason to refute the existance of a deity.

Me? I rather think the latter is more sensible, but I'm an atheist and thus biased.

Re:Skeptics, *yawn*

[jnik]

Here's the problem. Once upon a time Thomas Aquinas wrote about how wasn't it really nifty and cool that the science of the time and the theology of the time just really meshed in a fantastic way and they all got together so beautifully and pointed to each other and supported each other.

Then the science started changing, or more accurately progressing and refining itself. And the theologians felt threatened and tried to push down the science.

Now along comes Hugh Ross. Who's saying isn't it so wonderful that our modern understanding of the cosmos gets along so great with "our" theology and points the way to...

I think it's understandable why a lot of people are very, very nervous about him and anyone who's backing his institute. I don't entirely discredit the argument from design, but it's really more of an interesting philosophical twist on things than anything else. Scientifically I dislike Ross' approach because it potentially restricts scientific inquery to "approved" channels. Religiously I dislike it because it tries to pigeonhole god into a particular "gap" in the cosmos and when our scientific understand expands to fill the gap, suddenly god seems useless. I sorta think of god as having better things to do than hanging around as a mystical incantation to fill holes in our scientific knowledge, and I think science has better things to do than trying to back up a theological perspective.

This doesn't preclude discussion and research into the scientific/theological interaction, but I'm highly suspicious of checking scientific research against theological conceptions.

Hummel's Galileo Connection is a pretty good read on the subject, BTW.

Re:Skeptics, *yawn*

[daeley]

By the same token, being a staunch atheist means you will look for any reason to refute the existance of a deity.

Bzzzt. Nope, wrong. Being a staunch atheist means there not *being* evidence to prove the existance of a deity.

Re:Skeptics, *yawn*

[Mr.Intel]

Yes, believing in a "deity-influenced" universe means that you have put some blinders on. You will look for proofs that support your position (which is basically looking for very low percentage odds on certain things, or non-sensical behavior in creatures or systems).

Being someone who believes in a deity-influenced universe, I wish to make it clear that not all of us put blinders on. Indeed, I make it a point to examine as much as possible all points of view. This not only allows me to see a bigger picture, it helps me understand what motivates and inspires people. Which incidentally is far more important to me than possible 'alien' life forms. Of course I look for evidence to support my views, but I do not dismiss evidence that seemingly does not. Isn't that the mark of a good scientist? Collect, examine and categorize all available information. Maybe it's just me...

Re:Skeptics, *yawn*

[Faux_Pseudo]

I just want to warn anyone who is thinking of reading St Thomas Aquinas that they might want to think of doing something else. The book he is talking about is Summa Theologica. I have read it and I must say that if you love doublthink's and the same thought process that caused Aristotle to say that the Earth had to be the center of the universe becasue it was perfect and all perfect things belong in the midle then you will love this. Otherwise you will find about 200 questions that are asked in the negative form with each of those haveing many more subquestions also phrased in the negative form. i.e. Qustion XXII artical 8 "It seems that predestionation cannot be furthered by prayers of the saints". Then he gives some very well resoned thoughts that back up the question and then he goes and uses extreamly bad logic to refute each of these points.

Its not something I would put on the "must read list"[0]. If you are looking for a good book on the same types of subjects I would recomend Augustine's The City of God which is written less than 5 years after the sacking of Rome by the Goths and is a much better read that wont make you pull your hair out.

While we are at it lets give a plug for Carl Sagan's Demon Haunted World which is the antithasis of Summa Theologica.

Disclaimer: I can't spell,

[0] Unless you want to be a very well read athiest or theologin, or in my case both.

If there were intelligent life on other planets...

[Stephen]

... they would be here. (Fermi)

seti

[Anonymous Coward]

apart from SETI being a huge waste of resources

I disagree with your statement. The people at Seti are investigating an area of science that simply has a low probability of success in a given lifetime. Does this mean it should not be done? It kinda reminds me of the people who play the lottery, you have a low chance for winning, but hey, if you do, it changes everything. and the longer you stay at it, and the more wavelength-space you cover, the better your chances get. Besides, SETI gets alot of money from private sources these days.

My personal opinion (and thats all this is, MY OPINION) is that SETI is not a waste in time and resources. Are they "LIKELY" to find anything? probably not, but ALOT of people feel that the payout if they do is great enough to continue to do it.

-hommiefro

Re:seti

[brunes69]

It doesn't matter how often you play the lottery, the chances of you winning any particular time don't go up. Every lottery is an independant random variable, it is not linked to the previous lottery in any way.

Re:seti

[brunes69]

What are you talking about? I sure as hell have no idea. *I* on the other hand am talking about statistics, a very disciplined branch of mathematics.

On the other hand...

[mcrbids]

These are the requirements for life ON EARTH.

One of the things that never ceases to amaze me is the sheer adaptability of life. Who's to say that our way is the only way? who's to say that life must contain water?

The -ONLY- requirement for life is that it must last long enough to reproduce.

In an environment without a moon, so that the planetary tilt shifts and there are more extreme climactic changes, mobility may be more strongly encouraged than it is here, which then might tip the scales in favor of the evolution of intelligence, resulting in an INCREASE of intelligent species.

The long and short? We simply won't know until we find another intelligent species on another planet. And, whatever we find, it will be far stranger than anything we've imagined so far.

Too restrictive definition?

[fiendo]

Isn't Drake's equation falling victim to the classic human flaw of being too, well human-centric?

Isn't it possible that life doesn't necessarily have to be water-based, carbon-based, or in need of a sun or planets at all? I forget which novel I read it from (it was years ago), but there was a sci-fi author (Asimov?) who put forth the idea that maybe there could be an intelligent life form that is electro-magnetic based.

Let's expand our thinking and loosen up the requirements a bit!

"Drake's equation is easy to understand. Take the number of stars in the galaxy (about 200 to 300 billion, based on generally accepted estimates), and multiply it by: the percentage of stars that are similar to our Sun in the energy output and stability; the percentage of stars that have planets (since not every star has any); the percentage of planets orbiting their star in a proper distance (so they could hold liquid water, a necessity for maintaining life); the percentage of planets with liquid water on which life actually evolved; and finally, the percentage of life-bearing planets in which intelligent civilizations (i.e., those that can communicate by radio) eventually came to be. All in all, there are five or six factors in this product."

Re:Too restrictive definition?

[the_2nd_coming]

dude...so that means that I can have sex with a sinliclorian who has 10 arms, a super long toung, is so flexable that a quadrajointed gymnist would be in aww and loves to have sex with me every moment of every day!!!!!!!!!!!

sign me up!!!!!

Re:Too restrictive definition?

[Bearpaw]

Isn't Drake's equation falling victim to the classic human flaw of being too, well human-centric?

If I remember correctly, Drake and Sagan were both quite aware of this. I think it was part of their relatively conservative (at the time) approach to the question. To wit: if life-as-we-know-it is the only kind of life, there could still be lots of life.

Re:Too restrictive definition?

[Dr Caleb]

Isn't Drake's equation falling victim to the classic human flaw of being too, well human-centric?

I whole heartedly agree!
In his book 'Cosmos', Carl Sagan made allowances for lifeforms similar to us, but with minor differences. Copper in the blood, instead of iron in our blood. Silicon based instead of carbon based. Even methane breather instead of oxygen breathers.

Ward and Brownlee seem to be taking our definitions and knowledge of what it takes to create life, and manipulating the Drake equation to fit those criteria; rather than allowing the universe to create life and develop it as the universe sees fit.

pessimistic and cocky...though logical

[realmolo]

The problem is, these guys are talking about what it takes to creat (Spock voice) "Life As We Know It".

Who is to say there aren't all kinds of life, that can flourish under completely different conditions than what we have here on Earth, or in our solar system?

And I love the "Earth is exactly the way it needs to be to support life on Earth" bit. Well, duh!

Other factors

[MuValas]

- there needs to be a country named "USA"
- there needs to be a state named "Michigan"
- there needs to be a city named "Grand Rapids"
- there needs to be a woman named "Jackie" that
is of Norwegian heritage
- there needs to be a man named "Don" that is of
extremely mixed heritage
- they have to meet and marry
- they have to have two previous children, one
5 1/2 years old and female, one 8 years old and
male
- and then they have to all to take a trip to
a place called "Florida", with its especially
fertile air.
- "grandparents" must live in this place, and
these beings must take care of the aforementioned "kids" for an evening.
- both "Jackie" and "Don" must be in the mood.

and *then* you get me.

Since this is obviously amazing unlikely to ever
occur again, I have therefore proved that no
one in the world exists but me.

Ta-daaaaa!

Me.

(Gosh its lonely)

Re:Other factors

[BLAMM!]

You use humor/sarcasm to make the point I was going to make. Namely that what is presented here is a list of requirements for life in the galaxy *period*, not for life in the galaxy, present company excluded. These items are what is needed and we *know* they were met once. To argue that it will never happen again because "It's too hard!" is ludicrous.

Re:Other factors

[Dreamweaver]

Unique and special just like everyone else, more like.

Just because every other human wasn't born under the exact same circumstances and, thereby, isn't exactly the same as the author of the comment doesn't make them any less human. Just because every other species in the galaxy didn't evolve along the same lines as we did on a planet we could easily call home does not make them any less valid. There'll never be another me (unless I get cloned for some reason), but there are some billions of other people like me, all of 'em unique and perfect snowflakes. There will never be another homo sapiens sapiens unless we go out and create one, but there's no reason to believe there aren't a multitude of other species Completely different from us.

Tripe

[MarkusQ]

This is tripe.

First off, Drake's equation was meant to map our ignorance, not as a serious attempt to enumerate the number of planets with intelegent life, just as if someone asked me how fast a car I'd never seen or heard of was, I might answer "take the distance from where it stops to where it stops and divide by the time it takes" as a (slightly) more informative way of saying "I don't know." Then I suppose these clowns would come along and say "But the driver might have taken side trips! What if he forgot his sun-glasses and had to go back for them? You aren't accounting for acceleration/deceleration time! What about the wind?", etc.

Secondly, "the moon is vital to life" is one of those science fiction plot ideas that predates science fiction. It comes in many forms, but I've never seen one that doesn't beg the question (we couldn't have evolved without the moon because the moon causes X, we are the only example of us we have, and evolved with X; therefore we needed the moon to evolve). It sometimes makes me wonder at the sagacity of whoever coined the term "lunatic."

Third, many of the things they drag in are by no means established (and several are in fact in doubt). For example, we don't know where the Earth got its water, so we can't say if the process is common or not. We have only detected large extra-solar planets because that's all we know how to look for. We don't know that a stable climate is needed for the evolution of complex life (some argue that an unstable climate is required, lest you get stuck at a local addaptive maxima.

Anyway, I could go on, but you get my point: this is tripe.

-- MarkusQ

Re:Tripe

[Mike Connell]

This is tripe

First off, Drake's equation was meant to map our ignorance, not as a serious attempt to enumerate the number of planets with intelegent life

"So I sat down and thought, "What do we need to know about to discover life in space?" Then I began listing the relevant points as they occurred to me." - Frank Drake describing how he came up with the Drake equation during the Green Bank conference.

0.02

Re:Tripe

[MarkusQ]

MarkusQ:

First off, Drake's equation was meant to map our ignorance, not as a serious attempt to enumerate the number of planets with intelegent life

Mike Connell:

"So I sat down and thought, "What do we need to know about to discover life in space?" Then I began listing the relevant points as they occurred to me." - Frank Drake describing how he came up with the Drake equation during the Green Bank conference.

I'm confused. Your tone (" This is tripe") seems to imply that you disagree with me, but the quotation from Drake you offer is exactly what I was refering to: he didn't sit down calculate the likelyhood of life in space from what we knew but rather sat down to list what we would need to know (and clearly did not, and for many points still do not). He was, as I stated (and as he has stated elsewhere) more interested in mapping out what we would need to learn than in computing an "answer."

So, are you disputing this (and if so, in what way?) or am I just confused about the intent of your post?

-- MarkusQ

Re:Tripe

[Mike Connell]

First part: you can say that he sat down (when deciding upon the necessary coefficients) to "map our ignorance" , but the statement "Drake's equation was meant to map our ignorance" is false. The equation really was (is) meant to provide answers.

Second part: the equation is an attempt to find out the number of detectable civilizations in space (I guess you are right that it was not to "enumerate the number of planets with intelligent life", because that isn't what the equation calculates), so I guess I technically agree with the second part of your statement.

The equation, and Frank Drake sitting down and writing it are two different things.

HTH

Re:Tripe

[MarkusQ]

From Drake's biography: "The purpose of the equation was to help focus the conference attendees' attention on the crucial questions that needed to be answered in order to determine the chances of SETI's success."

He didn't, as you state "come up with the Drake equation during the Green Bank conference"--he was one of the organizers of the conference, and used the equation to structure the agenda.

I stand by my interpretation (which seems to be reasonably common).

-- MarkusQ

Re:Tripe

[Mike Connell]

Jeebuz.

You said First off, Drake's equation was meant to map our ignorance, not as a serious attempt to enumerate the number of planets with intelegent life, and I have claimed that this isn't the case. Fortunately you have now quoted Drake disagreeing with you on the first point:

You: "Drake's equation was meant to map our ignorance..."
Drake "The purpose of the equation was to help focus the conference..."

As I've already conceeded, the second point is true because you have misunderstood what the equation calculates. It would be as accurate to say "Drake's equation was meant to X, not as a serious attempt to calculate how much I no longer care to explain this simple simple point to you over and over again".

Re:Tripe

[MarkusQ]

Jeebuz.

You said First off, Drake's equation was meant to map our ignorance, not as a serious attempt to enumerate the number of planets with intelegent life, and I have claimed that this isn't the case. Fortunately you have now quoted Drake disagreeing with you on the first point:

You: "Drake's equation was meant to map our ignorance..."
Drake "The purpose of the equation was to help focus the conference..."

Three points:

The quote you attribute to Drake is from his biography, not his autobiography. Clipping a quote at the point it starts to go against you is silly trick. The full sentence was:

The purpose of the equation was to help focus the conference attendees' attention on the crucial questions that needed to be answered in order to determine the chances of SETI's success. (Emphasis added)

Saying that something was meant to map our ignorance may arguably differ from saying that it was meant to focus attention on questions that need to be answered, but I can't see how any reasonable person can claim that it disagrees.

If it weren't for the fact that you seem to have posted reasonable things on other threads, I'd be tempted to think I was being trolled.

-- MarkusQ

Re:Tripe

[Faux_Pseudo]

Lunatic shares its orgin with histarical. You can do the searches your self on google and w-m.com but the quck and short is the hist histarical is the same hist that you find in historctome. If you think thats not politicaly correct then you will love lunatic which is based on the concept that a women goes nuts with every cycle of the moon. So it wasn't just sagacity it was intentional. Looks like the greeks and romans who gave us these words had the same problems with women that we do. Some things never change, some things like the earths magnetic pole change every 36,000 years or so.

What? Me spellcheck? -- Faux Alfred E Pseudo

Re:If there were intelligent life on other planets

[murray.steele]

Why? We're not there....

Notes for SETI

[Havokmon]

The most important conclusion (apart from SETI being a huge waste of resources) is an unavoidable cliché, which the authors avoided presenting directly, even though it stares into the reader's face from every page and each paragraph: What we have here is rare, maybe even unique.

Actually, based on these additional observations, SETI could refine it's search to locations that are MORE like our solar system. Since the authors book is based on making the questions fit the known answer, why not have SETI use that to it's advantage, and look for Earth-like life FIRST?

We can imagine a hell of a lot, but the authors are right, and we KNOW Earth-like life exists. Let's just start looking for the boring (bi-pedal humanoid), before looking for the fantastic (silicon/energy based, whatever you can dream).

Re:Notes for SETI

[fruey]

We can imagine a hell of a lot, but the authors are right, and we KNOW Earth-like life exists. Let's just start looking for the boring (bi-pedal humanoid), before looking for the fantastic (silicon/energy based, whatever you can dream).

You're obviously not an epistemologist. How can you know that I exist, let alone another world capable of supporting intelligent life. And how do we define intelligence?

Re:Nowadays . . .

[cetan]

Are you kidding? Now a days he would be sued because someone had patented the method of distributing torn paper products for measurment of the yeild of nuclear devices.

Hello? Fermi Paradox!

[fm6]

I find it very depressing to read a discussion on SETI where the only reference to Enrico Fermi is that cute little A-Bomb story. Fermi had something rather more important to contribute to the discussion: the Fermi Paradox. It's an insight that's rather more important than the Drake Equation. Drake gives us a "calculation" based on a long series of guesses. Fermi makes an observation based on observable fact.

If even a tiny percentage of stars have planets capable of growing intelligent life, and a tinier fraction of those manage to avoid blowing themselves up long enough to perfect intersteller travel, you should have a galaxy positively swarming with Bug Eyed Monsters. They've had billions of years to cross the interstellar vastness and do the exponential growth thing. So WTF are they? Except for the ravings of that guy in the FBI basement, there's no sign of them.

Re:Hello? Fermi Paradox!

[(void*)]

You do realize that the universe that we observe is IN THE PAST, don't you? You do realize the speed of light limitations right? You do realize just how much power a civilization must put out, to enable us to detect them right?

All these considerations make Fermi's conclusions less compelling. Be aware of the effect of anticorrelating variables.

Slide rule and back of envelope calculations

[Anonymous Coward]

Fermi's skill is not that unusual. When the slide rule was taught and used, almost anyone could make quick back of envelope calculations. It was an important skill to master because it aided in the use of the slide rule. To get the decimal point right with the slide rule, you had to have an idea of what the magnitude of your result would be. A slide rule will not fix the decimal point for you. That is up to you.

Re:SETI is not a waste of resources

[Havokmon]

Most people run SETI for the cool factor of techy looking screen saver. It's resource is that it actually looks like you're *doing* something

Errr If you're running the SETI Sreensaver, you ARE wasting resources.. turn the damn thing off and let your CPU crunch numbers 4 times faster..

If you cant disprove the science attack the source

[ahde]

You got to love the postscript.

Some ignorant jackass (and legions like him) imagines a personal affront to his religion (and probably his funding), but lacking any knowledge, abilities, or reason, turns to a personal smear campaign, claiming the authors were influenced, even duped, by a bomb tossing pedophile god worshipper false scientist.

it's all about time...

[passion]

OK, sure, I can buy the argument that throughout time there must be thousands of civilizations in the universe that are capable of radio contact... but that's stretched out over the lifetime of the universe.

Not all civilizations will last forever, not all will go into space and continue propigating, not all have invented their radios just yet. After all, we just celebrated the 100th anniversary of a trans-atlantic transmission...

What if aliens had turned their sattelites on our speck in the sky just before our signals went out in the air... What if they died off millions of years before life started evolving on this planet? What if we're the first life to exist in the universe (not ruling out that others could evolve, just that they haven't yet).

We don't know shit about this, and we won't until our Zefram Cochrane comes along and helps us reach to the other stars.

Underlying problem

[drodver]

The underlying problem with this and many other ET discussions is that they assume all life requires parameters similar to our own. Once the possibility of life taking forms completely alien to our own is accepted almost all current debates on the matter have their scope changed. No longer is it a debate about the existence of complex life, it is a debate about the existance of complex life as we know it.

Earthlike planets are impossible!

[meckardt]

The circumstances that allow intelligent life to develop are just too unlikely to ever occur. Therefor, I propose that it is just a mistaken assumption to believe that there ever was such a place as Earth... and even if there was, intelligent life never would have developed.

Hmmmm... reading some of the political news, this is probably correct.

Re:Tell you what

[Havokmon]

On the first day....(etc etc)... seventh day he rested.
(Several tens of thousands of years of silence, depending on your bible's timeline)
You do the division.

Well, you (and everyone else) seem to think a biblical day is one revolution of the Earth... What if it's a revolution of the Galaxy.. the Universe?

Some people can't "break out of the box", and take different perspectives. Both sides can be right, it just takes a little leveraging, and ego bashing. :)

paradox

[isotope23]

I have two ideas regarding this.

First, as a civilization approaches the technological level necessary to travel to the stars, they also have a myriad of opportunities to kill themselves off. I.E. nuclear war, designer viruses etc. As technology increases, (at least here) we are coming to the point where more and more dangerous technology can be used by the single deranged individual.....

If an evolutionary model is used, I think most species would have a crazy or two who might end up causing their own extinction. We are very near this point. Imagine either nanomachines, or plague as the easiest self replicating disaster.

2nd, perhaps other life does exist, but is not motivated by the explore and conquer ideal.
A xenophopic or non-curious species.

Re:Nowadays . . .

[jordan_a]

It wasn't to count time, he used the distance they were thrown by the explosion to calculate the force of the explosion. First year physics my friend.

Re:If there were intelligent life on other planets

[the_2nd_coming]

I think the quote is "if there were intelegent life on other planets, they would not come here"

as a statment about how horrible our civilization is.

"Fine tuning" != "divine design"

[Fweeky]

> Gonzalez writes: "The fact that the Sun's location is fine-tuned to permit the possibility of life [...] powerfully suggests divine design."

I can't resist pointing out that if the Sun wasn't in such a state, we wouldn't be here to talk about it.

On the other hand, if the Sun wasn't so tuned, and we WERE here and not all dieing of mass cancers or being frozen/boiled, I'd be much more inclined to believe that maybe there is some divine intervention there.

Re:"Fine tuning" != "divine design"

[Fweeky]

Can you please repost in a form that isn't just one long 25 line paragraph?

> We understand the processes, they don't work that way.

Says you. Maybe also says some scientists, but I'd still rather believe our knowledge and understanding is incomplete and our insight too shallow than give up and introduce something even more difficult to explain.

You see, if you want to rely on a Godlike being, eventually we're going to have to explain that. Exchanging one apparantly impossible thing with another just doesn't seem like good science to me :)

The problem

[mindstrm]

with these equations is that, although they are an esimated guess, there are far too many unknowns.

Until we find *some* kind of life *somewhere* else other than earth, we simply do not have anything to really go on to build statistics.

It's like, say I bring you over to my computer, tell you to hit enter, and then the computer shows you a number on the screen.

I tell you that this program follows a pattern, (not random) and that the numbers it produces are between one and a hundred billion.

Then I ask you what the probability of the same number coming up again is.

You have nothing to go on.

When I'm not so egotistical

[bluGill]

When I'm not so human first in my thinking I also use the following explination:

There are two intelligant civializations in the universe. (this expands to more, but not many) The other is many millions (maybe billion) lihgt years away. We can turn our telescopes on them, but the problem is they were intelligent millinos of years ago. Likewise they are turning their insterments on us, and the insterments would detect us, but we were not emmiting intelligent signals back when they would have had to leave earth to arrive now.

By the time we detect each other, we are both on the decline, by the time we get a response out, both are dead. And worse yet, because we are so far apart we can never impart useful information to each other. They might look on Fermet's last theorm as a child's exercise, and they might hear about it in their first decoded transmission. They can send a response right away, but it doesn't help, they won't get the problem for several million years, and we sovled it already. Likewise we can solve problems that they are interested in and haven't yet, but they will solve them long before we get decode their interest and get a solution back.

Re:Tell you what

[Amazing Quantum Man]

At the risk of answering a troll, how about Ezekiel?

Re:If you cant disprove the science attack the sou

[Bearpaw]

You got to love the postscript.

Huh. The postscript must have been entirely changed before I read it, as the version that I read makes no smears nor does any name-calling.

Unlike your post.

Two Points

[Kallahar]

1) Other life doesn't have to be like us. Just because we haven't seen life based on something else doesn't prove that it cannot exist. Maybe the most common form of life in the universe are hydrogen based blimp's floating in the atmosphere of gas giants around red dwarfs! We simply don't know yet!

2) In regards to the comment about there not being complex life, I suggest the book "Non-Zero" which talks about the concept that once life comes around, it will ALWAYS progress towards more complex lifeforms. (barring cataclysmic events) This is simple darwinism, the first lifeform to innovate will prosper until its prey catches up, ad infinium.

Personally, I like to maintain optimism. For example, I believe that faster-than-light travel (not necessarily "moving" FTL though) are possible simply because the universe would suck if we're confined to one or two planets forever. It may be irrational now, but "scientists" have said things were impossible which are now commonplace.

Travis

Re:Two Points

[vrmlguy]

1) This reminds me of some '70s era arguments for and against the intellegence of dolphins. Dolphins have very large, complex brains. This is likely to process sonar images. The question is, does this complexity lead to intellegence, at least of a sort that can be understood by tool-using primates? It is still arguable that ocean-dwelling mammals are capable of detailed communication with each other, but we can't translate because we don't have referents. Also, several common definition of intellegence include things like tool-making. Creatures without hands are going to have a hard time qualifying, no matter how complex their society.

2) Didn't you read the bit about long it took for cells to get organelles? Yes, once life comes around, it evolves in ways that increase the chances of eating and decrease the chances of being eaten. But that doesn't imply more complex. It's just as likely that evolution follows complex versions of "rock-paper-scissors". Birds evolved flight, but some (penguins, ostriches) have abandoned it. Are they more complex than their forebearers? Are snakes more complex because they evolved "beyond" limbs?

Tripe, cheese and moons.

[Thornae]

Purely in response to your second point, I'm reminded of Niven's "One Way Street" (I'm surprised no-one else has mentioned it yet). I'll not diminish the story by summarisation, but one of the points made is that without the Terra-Luna system to stir the atmosphere and makes tides, our planet would be a lot more like Venus - covered in clouds and victim of a greenhouse effect to melt lead. Niven's description is wonderfully evocative - "an eternal searing black calm".

Now, whilst I don't take issue with your objection to the 'massive moon vital for life' view, I do think it's important to note that our particular system does seem to be a rather odd freak of fate that has strong bearing on our existance. Perhaps the more correct view would be that a large moon is necessary for Earth-like life to develop. This is, as others have pointed out, rather like evaluating the probability of the factors that led to your own birth (eg, my father dropped a screwdriver on my mother's head - would I be here if he hadn't?).

Personally, while I find the argument fascinating, I consider the implications to be more metaphysical in scope than scientific. This is probably why it attracts so much emotive argument...

An Argument For No Other Life

[cybermage]

I forget who I'm paraphrasing, but I've heard a convincing argument for the absense, or extreme rarity of other intelligent life in our galaxy. It goes something like this:

In 20,000 years, humans have gone from banging rocks together to reaching escape velocity.

Earth has been capable of supporting intelligent life for way longer than 20,000 years, and the galaxy has been around for much longer than Earth.

Even if faster-than-light travel is impossible, at a mere 100,000 light-years across, a single intelligent race around at the time of the dinosaurs could have colonized the whole galaxy many times over by now.

Which sounds the most likely?

a.) Intelligent life is either very rare in our galaxy or unique to Earth, or
b.) Intelligent life is abundant and coincidentally developing at more-or-less the same level everywhere, or
c.) Intelligent life is abundant, but Earth is in the lead development-wise.

Perhaps there is a forth option, but without one, option 'a' is the simplest and , therefore, most likely to be correct.

Re:An Argument For No Other Life

[edremy]

There are a lot of other possibilites

d) Intelligent life is common but interstellar travel is very, very hard, as in "No level of technology allows it."
e) Intelligent life is common but they quarantine developing planets to prevent interference.
f) Intelligent life is common but civilizations burn out/transcend after limited times.
g) Intelligent life is common but they haven't had time to respond to us yet.
h) Intelligent life is common but we're located in a designated ecological preserve.
i) Intelligent life is common but they're waiting until there are enough of us to feed Rigel 4.

The only pieces of data we have are that they aren't here now and we haven't found any radio signals close by. Occam's Razor would seem to indicate a) in that case, but we haven't been around anywhere near long enough to call it.

Fermi's Paradox is bunk.

[Otto]

Hey, why haven't WE colonized the galaxy yet? Since we haven't given any indicator that we exist (outside of a 90 light year radius or so, and then only weak ass radio signals), we must therefore not exist.

Fermi was super intelligent in some areas, and dumb as a brick in others (like everyone else). Saying that it ain't there because you haven't found it is silly.

Re:Fermi's Paradox is bunk.

[roca]

If the human race survives without interference* we will certainly develop machine intelligence within 1000 years. Probably a lot less. Just look at the progress of the last 50 years, both in improving computers and in understanding the human brain.

[* In fact I'm a Christian and I expect a) humanity on its own would not survive but b) God will interfere. But that's a digression...]

Once you have a machine intelligence, making it practically immortal is easy. Making as many of them as you need is easy. Suspending them during boring interstellar travel is easy. They can easily travel to other stars using fairly conventional propulsion. IIRC, the Milky Way is O(100K) light years across, so even at 0.001c the estimated time to colonize the galaxy is only 100 million years. (Intergalactic travel is feasible too but we'll ignore that for now.)

Also note that once immortal interstellar-voyaging intelligences exist, there is no danger of them being exterminated by themselves or anything else**. The self-destruction risk disappears.

[** Unless there is some physics which we are totally unaware of which would allow the construction of, say, a bomb which would destroy all intelligence in the galaxy but leave it otherwise unaffected.]

Conclusion: if there is any intelligent life in this galaxy with a desire to colonize, then it must be younger than 100 million years.

If there is such life out there right now, younger than 100 million years, it would be unlikely to have arisen at just the same time we did. Therefore it probably isn't out there.

Some people believe that intelligent life is common, it just destroys itself every time. I doubt that. In an intelligent species there's a technological race between a) building machine intelligence and sending it to the stars and b) building and using weapons which can wipe out the species. Whoever wins the race wins the game, and I see no reason why b) should always win.

So either there is plenty of intelligent life and it ALWAYS is disinterested in overt colonization, or intelligent life is incredibly rare. It's pretty hard to reason about the former proposition but so far it seems that if we knew how to build a machine intelligence and send it off to reproduce, at least one of us would do it. So I suspect that intelligent life is incredibly rare.

Re:Fermi's Paradox is bunk.

[mikeee]

So either there is plenty of intelligent life and it ALWAYS is disinterested in overt colonization, or intelligent life is incredibly rare.

They're always disinterested because they're too addicted to Everquest (alien edition) to bother with the real world.

(not joking...)

Re:Fermi's Paradox is bunk.

[Sloppy]

Hey, why haven't WE colonized the galaxy yet?

We have. In a sense that is good enough for Fermi, we've "colonized" a sphere seventy or eighty (don't quible on the exact figure) light-years in radius. Radio waves count.

Brief panic, then recovery

[KSchroeder]

I was about 3/4 of the way through writing a new novel when "Rare Earth" came out; since "Rare Earth" contradicted pretty well every premise I'd based on the novel on, I was pretty freaked--until I actually sat down and read through the book. I shouldn't have worried. The basic arguments put forward in "Rare Earth" are each consistent and compelling; the problem is that each challenge to the development of life presented has its own solution(s), which they ignore. For instance, they maintain that plate tectonics is essential for the maintenance of an atmosphere; this is manifestly untrue, because neither Venus nor Mars have plate tectonics, and both planets have atmospheres (albeit unlike our own). In fact, when you examine Venus, it turns out to have something that may fulfil the same role as plate tectonics: "coronae" which are upwellings from inside the planet that form ring-shaped volcanic chains. So an Earth-like planet with coronae is quite conceivable, even likely. The authors of "Rare Earth" argue fallaciously by assuming an exact match to the Earth to be required for life, then running through a laundry-list of reasons why such an exact match is rare. But an exact match isn't required; not even an inexact match. My new novel posits planets in orbit around brown dwarfs (failed stars bigger than Jupiter but smaller than the smallest red dwarf). In researching the book I became convinced that such exotic environments (which may be the rule rather than the exception in our galaxy because brown dwarfs are at least as common as lit stars) are perfectly fine environments for the development of life: for sunlight, substitute infrared radiation and intermittent visible-light flares from the dwarf; for plate tectonics, substitute tidal stretching by the dwarf; for a Jupiter to protect against cometary impacts, substitute a smaller and more impoverished Oort cloud. The list goes on and on--for every supposed "requirement" of the Rare Earth hypothesis, there's at least one, usually many, alternatives.

Fermi did a back of envelope calculation on this

[Chemicalscum]

Fermi while he was working at LANL in the fifties concluded that intelligent life was very rare in the universe. A group of physicists were at their coffee break and joking about a Flying Saucer and alien cartoon in the New Yorker - when Fermi suddenly said "Were are they?".

His argument was if there were a number of intelligent alien civilizations in our galaxy - then there was a good statistical probability that some would be much more advanced than us. If they colonized the galaxy at moderate sub-light velocities (say 0.1c) then they would have colonized the entire galaxy in about 10^5 years. So if there were many extraterrestrial civilizations intelligent aliens should be here by now (he assumed that UFO phenomena were not produced by aliens).

This stuff is on the web - but I have forgotten the URL. Google "Fermi's question" and you should find it.

Sauce for the goose...

[fractalus]

I've seen this on all sides of the debate.

I'm a religious person; I believe in a creator. Does that mean I agree with all the creationist wackos out there who don't know how to do good science? Nope. Does it mean I look skeptically at atheistic scientists who look at something they don't understand, can't explain, and pronounce there must be some mysterious non-divine explanation because they've already decided there's no God? Of course I expect them to back up their science.

Right now science doesn't have good explanations for exactly how macroevolution works. Religion doesn't have good explanations for the apparent age of the universe. Everybody should just fess up and admit they don't know the whole story, quit pushing dogma, and work on finding honest answers.

But hey, I'm religious and therefore biased.

Re:Sauce for the goose...

[eyeball]

I think what's missing in most creation vs. science arguments is the allowance for the posibility that both sides could be wrong.

Re:Sauce for the goose...

[nathanh]

Problem with atheists is that they don't give any good answers that are meaningful to a human being with existential questions. Problem with religious folks is that they tend to interpret the world into what they want to believe. As always, the wise man walks in the middle and noone notices.

Problem with the wise man is that he thinks he's a lot smarter than he really is.

Hint: atheists don't offer meaningful answers to existential questions for the same reason that atheists don't offer gardening tips.

Iceball Earth

[coyote-san]

There's strong evidence that the earth was once an iceball yet life not only survived, it had an unprecedent and unmatched explosion of diversity after the Thaw.

The problem with the earlier models is that they only considered the incoming solar radiation and the ice. Shortly after the oceans froze over, the surface temperature near the equator was -50F and stayed there for many thousands of years.

But the earth (and any tectonically active planet) has volcanoes. Volcanoes release greenhouse gases, notably CO. According to one estimate I saw on the Discovery Channel (IIRC), the CO level hit _10%_ and the surface temperature was something like 150F before the ice started to melt. (Remember that the conversion from ice to water takes a *lot* of energy, and there was only poor thermal coupling between the hot atmosphere and frozen ocean.) Once the ice started breaking up, there was a cascade effect that lead to a thousand years of acid rain as the CO was washed out of the atmosphere.

And after the Thaw, we had the Cambrian(?) Explosion, the transition from the simple single-celled organism (the only life that could survive under the shattered sea ice) to multicellular life.

This begs the question - is an "iceball" stage a necessary precondition to multicellular life? If it is, and the fact that most life-bearing planets will have an iceball stage since stars become brighter over their lifetime as main sequence stars, then a key part of their argument is invalid. Life-bearing planets will have ice-ball stages, and multi-cellular life will appear after the Thaw.

As an aside, one thing that's unique about the solar system is the unusually high level of metals for a system of our age. Maybe complex life requires these metals, and we're a few billion years too early.

Re:Iceball Earth

[coyote-san]

Sure we have. Look at the solar spectrums. Older stars have less metals (and remember that to an astronomer a "metal" is anything heavier than helium), younger stars have more metals. I think there's also a connection with distance from the center of the galaxy - further in you have more metals, further out you have fewer metals.

This makes sense - metals are distributed in planetary nebula and supernova explosions (and the heavier metals are only produced in SN explosions), and the gas clouds that give birth to stars are increasingly 'polluted' over time. The gas cloud that the solar system formed in was probably close to a supernova explosion - the shock wave both compressed the gas (leading to stellar formation) and deposited an unusual amount of metal in it.

When astronomers compare our sun to similar main sequence stars, we have significantly more metals. But we don't know that that means about their planetary systems - are they limited to small rocky bodies (Mercury, Mars) in addition to Jovians? Earth-like planets with a frozen core (no magnetic field, erosion reducing everything to a submerged swamp)? Or maybe an earth-like planet incapable of supporting any civilization higher than basic agriculture?

On the flip side, IIRC the youngest stars have the same amount of metals as us. This means that we could find millions of inhabitable planets where life is still at the 'ocean slime' stage.

BTW, the "Iceball Earth" scenario was covered in Scientific American a year or two ago, in addition to the documentary airing on the Discovery Channel. The "metals" analysis was covered in Analog (IIRC).

Re:Iceball Earth

[zCyl]

Maybe ... we're a few billion years too early.

Now there's a promising movie plot... In a billion years, humanity would become the extremely technologically and genetically evolved caretakers of newly developing sentient life in the universe. And how would we treat it?

Re:Iceball Earth

[3am]

Now there's a promising movie plot... In a billion years, humanity would become the extremely technologically and genetically evolved caretakers of newly developing sentient life in the universe. And how would we treat it?

eat the tasty ones, f*ck the sexy ones, and market pepsi products to the rest as 'emerging markets'.

Re:Nowadays . . .

[PaulGibson]

Yeah, I remember doing this in first year physics. They let us detonate the bomb in the law school. 2 birds.

begging

[iiii]

MarkusQ, big kudos to you for the first correct, appropriate in context, use of "beg the question" I have ever seen on this site. It is misused *vastly* more often than it is used correctly, so it's a relief to see it right for once. Way to go.

Re:begging

[MarkusQ]

MarkusQ, big kudos to you for the first correct, appropriate in context, use of "beg the question" I have ever seen on this site. It is misused *vastly* more often than it is used correctly, so it's a relief to see it right for once. Way to go.

Thanks. I was once chastized for using it correctly by someone who was so used to seeing it used incorrectly that he misinterpreted my post in an odd way that let him see the misuse he expected. Jeesh.

-- MarkusQ

P.S. *smile* Am I correct in deducing that you from your user ID that you eat processed starches?

Re:If there were intelligent life on other planets

[Stephen]

Agreed. It's not a proof, but I find it more convincing than these Drake-type probabilistic calculations. (How do you know you've got all the factors? How do you know they are independent so that you can multiply the probabilities?)

The Fermi argument is really that if there are lots of planets supporting intelligent life, it is likely that some of them are more advanced than us, and so should have explored further, or at least worked out how to signal us. (The fact that Fermi was mentioned at the beginning of the article was a bonus.)

Drake is wrong, for the following reasons

[dasunt]

I agree with the idea that Drake's equation is wrong, but not for the reasons stated.

Drake is assuming that all life must evolve on an earthlike planet. Europa-like planets, with a possible liquid ocean, and warmth supplied by the tidal forces of a gas giant, seem much more plausable. (Btw, the book discussed seems to ignore this possibility as well). Jovian planets seem more common then earth-like planets, and some of the reasons the book brings up for the decreased incidence of life don't apply (Jovian planets can be at a distance from the sun where the sun's energy fluctuations wouldn't matter, since the moons are warmed by tidal forces. Of course, in some discovered systems, Jovian planets are rather close to their stars, which means the $64k question for this scenerio is: how many stars have Jovian-type planets with the appropiate moons at the right distance?).

On earth, life took quite some time to jump from sea to land. On a Europian planet, there is no land, but there is another "beach" they can wash against - airless vacuum. I don't see any reason why a creature can't evolve to live in a vacuum, which leads to the idea of a lifeform being able to live in interstellar space. Imagine a creature that is content to drift through space in a dormant state, only "waking up", when its near enough to a star for its version of photosynthesis. Damned if I'd know how such a life could generate intelligence, but if I was a Europan, staring at earth, monkeys making fire wouldn't be an idea I'd come up with. ;)

Of course, we have the Jovian planets themselves, with thick atmospheres, and the chance of liquid water to exist in that atmosphere.

The point of these examples, is that the Drake equation is misleading, making assumptions that might not be true.

Just my $.02

Major flaw: increased number of variables

[angel'o'sphere]

By increasing the number of variables in the "Drake equation" the authors make one major error: a lot of the variables they introduce are very close related:

E.G.
a star of proper mass and:
A constant energy output from the star
are close related to each other IF the star has a similar age like our sun e.g.

I mean: if the star is similar old like the sun and has similar mass like the sun, it will have a similar and constant energy output, like our sun.

For the planet the following variables are not independened from each other or even depend on the variables related to the sun above:
Proper distance from the star.
A proper mass.
Oceans
Plate tectonics.

IF the planet has the proper mass THEN the planet will have plate tectonic. EXCEPTION: the planet is FAR older than our earth.

IF the planet has the proper distance from the star AND the planet has the right mass THEN the planet WILL have oceans.

The bottom line is that many additional factors must be added to Drake's equation. One must keep in mind that as any term in such an equation approaches zero, so too does the final product. For most terms, we have no way of reliably estimating their true value, but it seems like at least some of these values are extremely low

I doubt that. IMHO the approach should be other way around. We shoudl look how many variables indeed are only different expressions of the same basic principle.

There are several astrophysicians which strated to study and make models for solar system creation. They describe how a solar system is comming to existance like this:

You have a big cloud of "dust". Depending on the distance from the galactic core and super novae around that area you will have there a defined mixture of heavy elements and lighter ones.

During star forming the mixture is slowly compressed by gravity ... during this phase you have a sorting of all elements by weight.

Basicly the same process like in a mixture of liquids and sand and lead in a hot pot: lead sinks to the bottom of the mixture, above sand will settle, then you have the hot water and on the surface you have the oil.

Now imagine you have a dust and gas cloud as big as our solar system. The center is several thousand degrees hot, but FAR from ignition.

There will be several hot spots where bodies are forming. The closer the bodies are to the center, the more heavy elements will participate in the forming.

IIRC some 10 years ago an astrophisics got a nobel price for crafting such star system forming models.

He proofed that our solar system only had one way in "condensating" into planets and that is the way it is visible now.

Well, of course we could have the Venus a bit farer away and Mars a bit closer.

Earth then would probably not exist but Mars would be bigger.

Same for the outer planets, there could be one more or one less. But the distribution of mass from the inner side of the solar system to the outer side would be very similar.

And it only depends on two things: total size of the dust and gas cloud forming the solar system and total amount of heavy elements in the cloud.

Bottom line, if two dust clouds are similar enough (-> size of sun which is ignationed is similar) and in the same distance to the galactic core ( -> distribution of heavy elements is similar) they will condensate to similar solar systems.

If you take ten sun like suns I bet that ALL have planets and that 3 have one or more in the distance of the Venus/Earth/Mars belt.

And those planets will in the size of Mars to Venus. Because there is NO WAY in forming any other planets in any different size or any different distance. (If the system has enough iron and other heavy elements)

There are further variables which are supported by weak arguments: a big moon.

Sure, a big moon stabilizes the rotation axe.
Sure, it might deflect incomming bigger rocks.

But: how important is a stabilized rotatino axis?
During earth history the planet flipped its rotation axe several times by 180 degrees. Yes, what is now north pole was then south pole.

This was recent hsitory! In terms of the age of the earth.

The same for the proper distance, a final quote: There isn't much margin for error here: a change of 5 to 15 percent in Earth's distance from the Sun would lead to the freezing, or boiling, of all water on Earth.

The earth was some hundred million years ago totaly covered by ice. There is a recent story about that in scientific american, it was covered here on /. Live allready existed at that point. And it survived under the ice plate as the ocean was warm enough by vulcanic activities. Not only bacteria but high evolved live like crabs etc.

There is absolutely nothing preventing that, to be the normal way in other solar systems. E.G. if Alpha Centauri has a Earth sized planet as far away as Mars ... it could just be a ice covered ocean world like our world was 400 million years ago. Habouring live, of course.

Regards,
angel'o'sphere

Re:Major flaw: increased number of variables

[the_consumer]

But: how important is a stabilized rotatino axis?
During earth history the planet flipped its rotation axe several times by 180 degrees. Yes, what is now north pole was then south pole.

Um, I have never heard of this happening. I know the magnetic poles swap places from time to time, but the rotational poles have never done so, AFAIK. If they had, it wouldn't just be North and South switching, it'd be Easy and West as well!

Re:Major flaw: increased number of variables

[angel'o'sphere]

the moon is crucial to our biosphere because it actually *generates* the earth's magnetic field. basically, the system works like a huge dynamo with the earth's iron core as the center.

This is wrong.

The magnetic field is generated by the molten core of iron inside of the earth.

Further more: its absolutely unclear if a magnetic field is needed to evolve live.

angel'o'sphere

Separated in TIME and inv-sqr law

[redelm]

I have a beef with SETI. I can more-or-less accept the Drake Equation, but I have a few additional factors: First, an ET civilization probably wouldn't broadcast for a long time. Second, it'd have to be powerful and nearby. Both drastically reduce the probability of contacting ET, even if there are thousands of ET civilizations.

Civilizations develop or die. They're not static. We've been using radio for less than 100 years, and are already stopping using it in any observable pattern (digital spread-spectrum). Our broadcast/beacon program lasted less than 10 years out of the 3-4 billion that there's been life on Earch. Et may be more patient and change slower, but by how many orders of magnitude?

The inverse-square-law really kills. Don't worry about RF emissions attracting aliens. They don't make it past Jupiter with any S/N. An important benchmark is that Voyager 5 used ~5 Watts power with a directional antenna to the most powerful receiving array on Earth and couldn't get more than 110 baud past Neptune's orbit. Give ET a 10 MW transmitter with 100x greater efficiency, and he's still got to be close, ~10 light-years.

I don't believe we're alone, but I do believe we're separated by unfathomable gulfs of time and distance. Even if we did discover faster-than-light travel, there's still the phasing of civilizations development and the huge number of rejects.

You mean LIKE US, don't you?????

[gelfling]

After all until we ACTUALLY FOUND tube worms living at the bottom of the Atlantic Rift living off boiling sulphuric acid we 'naturally' assumed that such a thing was absurd and patently impossible. We falsely assume that ET life would be ANYTHING like us or anything proto-humanoid or 'bear' we see on the old Vid.

Life is one thing, intelligent life quite another

[ColGraff]

The problem is this: Yes, we can posit any number of life-forms that don't need air, or water, or DNA, or even a planet. Good for us, I say - that's remarkably open-minded.

But...

To have intelligent life, there needs to be some advantage to intelligence. You can have a Funky Space Alien Bug (FSAB) that is twice as smart as all the others - but what good is that if all it does is, say, float through space collecting hydrogen using an electromagnetic field? Not much- - it doesn't help the bug eat or get laid, so there's no more chance for it's genes to be carried to the next generation than the other, dumber bugs.

To have intelligence, you need life in a place where intelligence matters. There needs to be some possibility that if you're a little smarter, if you can think abstractly, if you can teach your offspring and learn from your parents - heck, if you can learn at all! -, there has to be something to gain from these abilities in terms of staying alive.

Am I making any sense here? What I'm trying to say is that sure, there may be life in environments we may consider so hostile to life, there's no way it could exist. But that life may adapt to that extreme environment by becoming so well adjusted, no further cognitive effort is needed for survival.

David Brin's uplift series

[coyote-san]

Ironically, one possibility is addressed in David Brin's "uplift" series (Startide Rising, Uplift War, etc.) Only instead of being the brash wolfling race, we would be the Progenitors that first started uplifting other species.

But as a practical matter we would just overwhelm any existing life on these planets. Even our "primitive" life forms have billions of years of evolution on the competition, and they wouldn't stand a chance.

Time

[fm6]

I'm not talking about detecting civilizations out there. I'm talking about our own neighborhood. As Fermi pointed out, it might take a civilization millions of years to spread across the galaxy -- but that's nothing in terms of the total age of the universe.

People are too used to thinking on a human scale. Look at it this way: if the whole age of the universe were a single year, then the human species would have existed for a fraction of a second. One explanation of the Fermi paradox is that no intelligent species manages to survive longer than that -- a depressing thought.

Re:The Theory of Panspermia

[coyote-san]

One big problem with the theory of panspermia is that it just pushes back the questions. If life didn't start on earth, fine. Then how did it start?

Re:An indication(not proof) for God

[gewalker]

Beats me why anyone believes in theistic evolution. Bible account is very clear, God created animals, man, trees, etc. fully formed. If you don't believe this to be accurate, why believe in the book. Bible refers to creation in many of the books of the old & new testament. Jesus refers to it specifically as a factual account. If he could not get these facts right, why would you dedicate your life to follow him (as he would either be a liar or delusional).

What I thought was interesting was the author's faulty logic in this statement. Additionally, anyone who insists on taking the ideas of this book as a proof for god's existence will also have to accept the authors' prepositions about the age of the universe, the age of planet Earth, and more importantly, the theory of evolution

Totally invalid. Assume as a creationist, I find that the Drake equation gives me a zero (or essentially zero result). On that basis, then the exisintence of God is implied. This does not mean I would then accept evolution as valid, rather that the Drake hypothesis is false.

IF A then B, but B != TRUE, then NOT A is true.

IF A is dependent upon (A1 + A2 + A3) then at least one of A1, A2, or A3 is false. I expect most creationists would argue we are the unique exception to Drake=0, because of cooking the results for the human case by God.

Thus A creationist believing eperiemental value of Drake equation is approximately zero, is a strong argument in favor of creationism. To the suprise of most apparently, the Bible says nothing about ET life or intelligence. Thus Drake > 0 does not disprove the Bible. Bible could be proved by factual errors, etc, but not by Drake > 0.

Knuth

[IntelliTubbie]

Donald Knuth is well-known to be a religious man (he has even written on the subject) -- which is why everything written in The Art of Computer Programming is false. I have a marvelous proof of this, but unfortunately Knuth wrote TeX as well, so when I tried to typeset my groundbreaking proof the entire thing was erased and replaced with a copy of the King James Bible. Damn that Knuth!

Cheers,
IT

Drake equation uneasiness

[DNS-and-BIND]

I've always felt uneasy about the Drake equation, but I've never been able to put my finger on exactly why.

"Drake's equation is a statistical calculation, but with no other example for life, we're doing statistics with N=1."

And that's what's always bothered me. It always irked me how Sagan smoothly insisted that life would become intelligent, and the way he calmly made assertions about which he had nothing but his own opinion to back up!

Re:Tell you what

[jaoswald]

If it weren't a single revolution of the Earth, then why didn't God explain it more clearly (in Hebrew, of course) in the first place?

The only reason to spend a second thinking up your "outside the box" solution is because you need an excuse to stay in your own box, i.e., you need some way to keep the seemingly-explicit language in Genesis consistent with your understanding of history.

How about thinking outside your own box: Genesis was written by several Hebrew writers, who were addressing an audience that needed religious instruction, but didn't care too much about how old the universe really was.

1) Makes perfect sense
2) Doesn't require any stretching of the Hebrew text to make it work.

another possibility

[maxpublic]

I realize I'm posting this in a forum that practically worships the idea that 'friendly aliens are out there', but I have a karma of 50 so what do I care?

The biggest mystery in terms of alien civilizations is why they aren't here. Why haven't they colonized the Earth? If intelligent life is common then at some point at least one species had the wherewithall to colonize the galaxy. And that species, once moderately into the colonization process, is immune to complete collapse. Any one planet might suffer a collapse in civilization; even thousands might, if they're all affected by the same disaster. But many won't be and since expansion is a given (otherwise they would never have left the home system in the first place) they'll reoccupy any habitable system that goes through this collapse. And if you posit that one species is capable of doing, then others will eventually come along as well.

What this means is that the Earth should have been colonized by *at least* one intelligent species that found it to its liking at some point in the past (distant past, actually). And even if that colony was destroyed it wouldn't matter - Earth would just be *recolonized*, again and again because colonization is what these aliens, all of them, do. Yet it hasn't: we're here and nobody else is, nor is there any evidence at all to suggest that anyone has been here but us. And even if they had been here, in all the long millions of years the recolonization, or new colonization by some other species, just didn't happen. Doesn't make sense.

The 'galactic' disaster theories (a la Niven's Thrint/Tnuctipun war) are so much hogwash - great science fiction, lousy science. Also hogwash is that civilizations advanced enough to begin the process of colonization eventually collapse - every planet, everywhere, all of them in a time frame close enough to prevent recolonization. Uh huh. Again, nice science fiction but there's no rational reason why this should be believed. Another postulation of pseudo-science is the 'Prime Directive' which again has no basis in anything but a TV show popular among geeks. Humans don't practice the prime directive so there's no reason to believe that *every species capable of colonization* is somehow enamored of leaving nice big chunks of real estate alone to allow potential natives to *perhaps* develop into future neighbors. The 'Prime Directive' argument is apologia for why we aren't in contact with a colonization-capable species and isn't something to be seriously considered. The 'we haven't discovered them because the galaxy is so huge' argument is much the same thing, as it doesn't matter what *we've* done; *they* should be here anyway.

All of these are just suppositions, in fact defenses given by the pro-alien crowd for why contact hasn't occurred, and why there is no evidence at all that other intelligent life exists in the galaxy.

Of course, the only sample for life we have (so far) is Earth. Life on earth is incredibly resilient and lives in the most inhospitable of places; it's rational to assume that life exists elsewhere as well, wherever conditions permit. The 'Earth Only' crowd essentially denies the adaptability of life by claiming - without any evidence to support them - that life was a one-time fluke in a galaxy with a hundred billion or more stars. Right. Tell me another, O creationist.

But whether or not life exists elsewhere isn't the point. The question is whether *intelligent* life exists elsewhere. And how do you go about answering that question?

For starters, they aren't here. If intelligent life were common, and throwing out the inane arguments, they should be; they should've been here all along, during our development and before, and they aren't. Okay, so this gives us some idea that while life may be common, intelligent life might be darned rare. Another fact in support of the rarity of intelligent life is Earth itself. Of all the species that have existed over the course of hundreds of millions of years (just taking into account complex organisms, say from the Triassic on up) there has been exactly one intelligent life form. Just one. No others. That is pretty definite evidence that *at least on Earth* (my only sample, and yours too) intelligent life is incredibly rare - unique for this planet. It might very well be a fluke.

So, common sense tells us that life may be common but that intelligent life might be one of those one-in-a-billion shots in the dark. With that we have something to work with. But the question still stands: even if intelligent life is that rare, unless humans are the first to make it this far why has no species colonized the galaxy?

That one is unanswerable, as yet. My hypothesis (completely unsupported) is that once a species reaches a certain technological level, barring accident or malevolence it'll do as we're doing now - ride a roller coaster of technological development that follows an asymptotic curve to a conclusion that we can't even guess at. If this is true, it could be that all species, once they've punched the ticket for ride, reach the technological know-how to travel between stars and colonize planets; but that by the time they get to this level of development they're no longer interested in doing so. It could be that whatever siren-song plays at the event horizon of asymptotic development is far, far more interesting than the pedestrian endeavors of colonizing other planets. That *something* happens to them that draws the entire species into one great collective bent on achieving a goal we can't even guess at - not yet, at least.

And once they achieve that goal, they disappear from the universe as we know it. On to some other playground where our little patch of reality appears downright boring in comparison. Perhaps they go someplace else and mutter 'let there be light'. Who knows? All conjecture, of course.

But if true, it does explain why the universe is so empty. Any species capable of interstellar colonization is no longer interested in colonization. The time frame between discovery of the radio and the Whatever-It-Is that tempts them to go 'someplace else' would be awfully short. Hence no colonization, and no tens of thousands of years worth of radio waves criss-crossing the galaxy.

I have no evidence for any of this, but I believe that Vernor Vinge just might have gotten it right in "Across Realtime". In any event, barring self-destruction or catastrophe we'll hit the 'event horizon' in about 150 years, and then we'll be able to answer the question for ourselves.

Assuming all of this isn't a crock.

Max

Re:The Theory of Panspermia

[coyote-san]

There's no doubt that we're finding amino acids in interstellar dust, but it's a huge step from amino acids to life. Where is the energy coming from? The consumables?

In contrast, the theory that life started in gaps in clay near a shorelines has energy from both sun and surf, consumables brought in on the water, etc. It's a lot easier to see a self-reproducing chemical system getting started and taking off.

Re:machine intelligence

[roca]

I agree that given where we're at, *we* will probably lose the race to a nanotech (or similar) catastrophe (barring divine intervention), but why should this be the case for all intelligence-supporting worlds? It's not obvious you need nanoscale self-replication in order to build a machine intelligence, even a self-replicating one. And there are other possible outcomes, such as 1984 worlds where technological advances lead to a small group with total domination, able to halt threatening research into doomsday weapons.

What is alive seriously

[budgenator]

living people are definatly alive, metabolic activity, reproduction locomtion and the same follows all the way down to bacteria.

rocks are definatly dead no metabolic activity, no reproduction and non-locomative

but there are things in the grey zone, are viri alive? no reproduction, they are manufactered by the host, no metabolism again taken care of by the host and non-locomotive but they are considered alive by most people.

let's say viri are non-living just like a computer program with out hardware is non-functional consider ricketsia and chalymedia each class of organisms missing things that we consider part of being alive.

the point is there is no definition of alive just like we know the Earth is a planet and a rock isn't but there is a lot of stuff in the middle, where is the line drawn?

as for me I'll keep on crunching seti@home because it's likly one of us will stumble across some signal that'll lead to an interesting phenomina probaly not associated with an intelligent source.

not a good explanation?

[Edmund Blackadder]

I think science have a very good explanation about how evolution works.

It is usually given in highschool or college bio classes.

You'd have to redesign a lot of atoms

[leonbrooks]

There may be forms of life out there that have nothing to do with amino acids or DNA or even liquid water.

You'd have to redesign a lot of atoms.

For example, water is very special in a number of ways, starting with being very small and highly polar, and working outwards.

In the case of systems like DNA, you have very specific atoms arranged in large, highly ordered groups of groups, to form codons; these codons are bound to their DNA strand (itself amazingly complex); the two DNA strands bound to each other with complementary codons and twisted just so, the whole lot folded, and folded again, each enfoldment a marvel of geometry and held in place by (again) very specific complementary geometry and features (bump-hollow, pluspolar-minuspolar, oily-oily etc). This is just DNA I'm on about so far, we haven't explored the miracles of RNA transcription, the automated untangling that happens as this progresses along the (foleded!) DNA strands, yadda, yadda, or worked up the scale to the incredibly complicated array of interdependent molecular factories, structure and membranes which fill a living cell... I have a couple of huge wall-charts from Roche which show a massive simplification of the 1,000 `most important' reaction paths of the 50,000 _known_ in a cell (and given a typical collection of roughly 2000 organelles in a cell, the 50,000 looks very impoverished, a small fraction of reality). The simplified diagrams look like a collection all of the marshalling yards in the USA, in colour, after an earthquake and a tornado came through.

OK, now if such specific atomic properties are necessary for the operation of this mind-boggling miracle of moelcular engineering, how many other systems of _successfull_ arrangment of the same atoms do you expect to find?

Re:Tell you what

[Havokmon]

The only reason to spend a second thinking up your "outside the box" solution is because you need an excuse to stay in your own box, i.e., you need some way to keep the seemingly-explicit language in Genesis consistent with your understanding of history.

hehe I don't intend to mean it's something I dwell upon, it had just occured to me, and happened to fit both scenarios. Kind of like "Man in God's image" = god looked like an ape - fits both.

I was the only kid in Lutheran School class that thought coloring Mary white and Joseph black would be interesting.. I spent more time sitting in the corner that year than I ever spent in detention in public school.

The Big Guys

[fm6]

...my point is that wherever life starts, it is going quickly go upscale culturally and head for the prime real estate (at least between the stars, probably even away from the noisy, supernova-prone galaxies) soon after it develops intelligence, and won't look back.

Interesting idea. But wouldn't the creations of such a civilization be even more conspicuous than one that just colonized planets? The appearance of non-natural structures in interstellar or intergalactic space would be pretty hard to overlook!

Request. When you make an original post, please write an original subject line. I almost didn't read yours -- which would have been a shame. When I get a dozen or so "Re:" replies I tend to assume they're all knee-jerk "Oh yeah?" responses, as most of the responses to "Hello? Fermi Paradox!" were. It's one thing to be disagreed with, but people who just want to tell you that you're wrong are too boring and depressing to deal with.