Rare Earth 442
| 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.
Another factor? (Score:3, Interesting)
Re:Another factor? (Score:2)
Re:Another factor? (Score:2)
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 [sciam.com].
I suspect that part of the problem with Mars is that the core cooled down [cnn.com], 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? (Score:2)
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.
Re:Another factor? (Score:2, Funny)
How this important factor has been overlooked by so-called serious scientists is a mystery to me.
Simon Hibbs
Re:Another factor? (Score:2)
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.
Major flaw: increased number of variables (Score:4, Insightful)
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
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
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
Regards,
angel'o'sphere
The problem with all these equations... (Score:5, Interesting)
Re:The problem with all these equations... (Score:2, Insightful)
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... (Score:2)
Re:The problem with all these equations... (Score:2)
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... (Score:3, Insightful)
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... (Score:2, Insightful)
d)Not only have they visited us, but they [imdb.com] are [daniken.com] us!
Re:The problem with all these equations... (Score:2)
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... (Score:2, Funny)
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... (Score:2)
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... (Score:2)
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)
When I'm not so egotistical (Score:2)
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:The problem with all these equations... (Score:2)
Intelligent Life other than us is almost certain, when and where, that's the mystery.
Kintanon
Re:The problem with all these equations... (Score:2, Insightful)
Re:The problem with all these equations... (Score:3, Informative)
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... (Score:2)
Kintanon
Re:The problem with all these equations... (Score:3, Informative)
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... (Score:2)
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 [slashdot.org]
hmm. not sure about this... (Score:3, Interesting)
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... (Score:2)
Fermi... (Score:4, Funny)
This is a sign of high intelligence?
Re:Fermi... (Score:2)
Re:Fermi... (Score:2)
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 (Score:5, Insightful)
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 (Score:2, Insightful)
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 (Score:3, Insightful)
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.
.
Thanks Slashdot (Score:2)
Apart from the debate surrounding the book itself, I'm actually quite pleased with how it was reviewed (updates and all). Very fair. This is uncommon on the internet, so my kudos go to you.
Re:Thanks Slashdot (Score:2)
Kudos not to slashdot, but the reviewer...
A planet like Earth is not the only way (Score:2, Insightful)
Skeptics, *yawn* (Score:4, Insightful)
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* (Score:5, Informative)
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* (Score:2)
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.
Sauce for the goose... (Score:5, Insightful)
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... (Score:5, Insightful)
Re:Skeptics, *yawn* (Score:2)
Bzzzt. Nope, wrong. Being a staunch atheist means there not *being* evidence to prove the existance of a deity.
Re:Skeptics, *yawn* (Score:2)
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* (Score:4, Insightful)
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.
If there were intelligent life on other planets... (Score:2)
Re:If there were intelligent life on other planets (Score:2, Insightful)
Re:If there were intelligent life on other planets (Score:2)
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.)
Re:If there were intelligent life on other planets (Score:2)
as a statment about how horrible our civilization is.
seti (Score:2, Insightful)
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 (Score:2)
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.
On the other hand... (Score:2)
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? (Score:2, Interesting)
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!
Re:Too restrictive definition? (Score:2)
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? (Score:2)
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.
Re:Too restrictive definition? (Score:2)
sign me up!!!!!
pessimistic and cocky...though logical (Score:2, Interesting)
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 (Score:4, Insightful)
- 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 (Score:2)
okay, explain this to me... (Score:2)
Not sure I buy this (Score:2)
Something science has forgotten (Score:2)
An Influence on the Authors (Score:2)
Though an old earth creationist influenced the the authors, it does not mean that the hypothesis is invalid. One needs to look at the evidence. Does it make sense? Is there a better hypothesis out there? Are the assumptions reasonable?
Too many people will dismiss it for philosophical reasons and not try to see if it stands on it on its own merits. Does the evidence support it? Don't dismiss it because it could be used by creationists. We need to be open to the evidence.
Alas a lot of "folk science" is going to cloud up this discussion.
Re:An Influence on the Authors (Score:2)
This is exactly what's wrong with the creationist argument and why it is not science. The distance of the sun from the earth is not "evidence". It is a fact. To call it "evidence" of something is leap of faith the springs not at all from the sun but from something completely else.
This springs from the same source as the belief that the solar system revolved around us and the earth. Incredibly complex models were created to explain why the mars appears to retrograde from earth rather than the simplest model with the sun at the center that explains all our observations.
The argument: The fact that the Sun's location is fine-tuned to permit the possibility of life [...] powerfully suggests divine design. completely assumes that the sun is there for our benefit. It assumes that the universe was created specifically for us to be exactly what we are right now. This is exactly what's wrong with the entire book - it assumes that our situtation was created for us - rather than us for the situation.
In short: The sun was not tuned for us - we are tuned for the sun.
The assumption that life is rare because it has to be just like us is just the continuing of a series of errors based on arrogance.
"Our tribe is the center of civilation", "the sun revolves around us", "we are unique in the entire universe" are all statements based on our assumption of our importance. To assume that our importance dictates the distance of the sun from the Earth is the same thing.
The god of the triangle people is three sided, Get over yourselves,
=tkk
the anthropic principle (Score:2)
This is like holding a winning lottery ticket. You had just the right combination of numbers, which is nearly impossible. You might think that it's "divine influence" that your numbers won, because you had a near-zero probability of winning just by chance!
But then if you flip the problem upside down, if enough people play using random numbers, you approach near 100% probability that somebody will win, even though the vast majority of people will lose. So the fact that somebody wins is not amazing in itself. The winner (no matter who wins) will think that it was divine influence that caused them to be singled out as the winner.
So basically, if Earth didn't have just the exact right conditions for us to come into being, then we wouldn't be here to argue the point. There could've been a gazillion other "failed" Earths in other universes for all we know.
Tripe (Score:5, Interesting)
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
Tripe, cheese and moons. (Score:2)
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...
Re:Tripe (Score:2)
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 (Score:2)
Mike Connell:
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
begging (Score:2, Interesting)
Re:begging (Score:2)
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 [slashdot.org]?
Notes for SETI (Score:2)
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 (Score:2)
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?
Hello? Fermi Paradox! (Score:2)
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.
paradox (Score:2, Interesting)
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:Hello? Fermi Paradox! (Score:2)
All these considerations make Fermi's conclusions less compelling. Be aware of the effect of anticorrelating variables.
Fermi's Paradox is bunk. (Score:2)
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. (Score:2)
[* 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.
Slide rule and back of envelope calculations (Score:5, Insightful)
If you cant disprove the science attack the source (Score:2)
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.
Re:If you cant disprove the science attack the sou (Score:2)
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.
it's all about time... (Score:3, Insightful)
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 (Score:2)
Earthlike planets are impossible! (Score:3, Funny)
Hmmmm... reading some of the political news, this is probably correct.
"Fine tuning" != "divine design" (Score:2)
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.
The problem (Score:2)
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.
Two Points (Score:2)
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 (Score:2)
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?
An Argument For No Other Life (Score:2)
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 (Score:2)
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.
Brief panic, then recovery (Score:2, Interesting)
Fermi did a back of envelope calculation on this (Score:2, Interesting)
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.
Iceball Earth (Score:5, Interesting)
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 (Score:4, Funny)
eat the tasty ones, f*ck the sexy ones, and market pepsi products to the rest as 'emerging markets'.
How likely is the answer? (Score:2, Insightful)
t.
Drake is wrong, for the following reasons (Score:2)
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
Re:Nowadays . . . (Score:2, Funny)
Re:Nowadays . . . (Score:2)
Re:Nowadays . . . (Score:3, Funny)
Re:SETI is not a waste of resources (Score:3, Informative)
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..
Re:Tell you what (Score:2)
Re:Tell you what (Score:2)
(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. :)