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Is the Earth Special?
Hugh Pickens writes "Planetary scientists say there are aspects to our planet and its evolution that are remarkably strange. In the first place there is Earth's strong magnetic field. No one is exactly sure how it works, but it has something to do with the turbulent motion that occurs in the Earth's liquid outer core and without it, we would be bombarded by harmful radiation from the Sun. Next there's plate tectonics. We live on a planet that is constantly recycling its crust, limiting the amount of carbon dioxide escaping into the atmosphere — a natural way of controlling the greenhouse effect. Then there's Jupiter-sized outer planets protecting the Earth from frequent large impacts. But the strangest thing of all is our big Moon. 'As the Earth rotates, it wobbles on its axis like a child's spinning top,' says Professor Monica Grady. 'What the Moon does is dampen down that wobble and that helps to prevent extreme climate fluctuations' — which would be detrimental to life. The moon's tides have also made long swaths of earth's coastline into areas of that are regularly shifted between dry and wet, providing a proving ground for early sea life to test the land for its suitability as a habitat. The 'Rare Earth Hypothesis' is one solution to the Fermi Paradox (PDF) because, if Earth is uniquely special as an abode of life, ETI will necessarily be rare or even non-existent. And in the absence of verifiable alien contact, scientific opinion will forever remain split as to whether the Universe teems with life or we are alone in the inky blackness."
While most planets are obviously not suitable for life, life itself has a strong tendency to overcome the challenges of its environment. Life endures climate fluctuations, extraterrestrial impacts, and even extreme radiation, all here on Earth. While many of these protective characteristics are conducive to the emergence of higher life, life itself has already shown its capacity to adapt and overcome.
All life really needs is a liquid solvent, energy, and enough time.
"You know, the most amazing thing happened to me tonight. I was coming here, on the way to the lecture, and I came in through the parking lot. And you won't believe what happened. I saw a car with the license plate ARW 357. Can you imagine? Of all the millions of license plates in the state, what was the chance that I would see that particular one tonight? Amazing!"
Just because our "route" resulted in our "life" situation, doesn't mean that other routes couldn't produce equally valid and viable "life" conditions. We're not that special.
My UID is prime!
Didn't the Earth get hit by another planet, causing it to shoot a ton of crust into orbit..creating the moon?
Clearly, life requires a mars-sized object to hit the planet where life wants to form.
Jury's still out on that one: http://en.wikipedia.org/wiki/Moon_Formation#Difficulties
Geeks like to think that they can ignore politics, you can leave politics alone, but politics won't leave you alone.-rms
It seems that life, intelligence, and civilization are the things that we find most interesting, in ascending order, when discussing exobiology. And, in ascending order, much, much more difficult to achieve. In other words, simple life is almost common, complex life is rare, intelligence even rarer, and civilization the rarest of all. Each step requires more time, stability, and opportunities for differentiation, than the last. A lot of the uniqueness of the Earth, according to the article, has to do with its suitability for developing land-based life. I wonder if achieving a land-based civilization is rarer than a liquid-based one. If there are aliens sending probes over here to investigate us, maybe it's to study this weird, land-based civilization. I admit that one advantage to land-based life development is that it's much easier to form divided ecosystems on land than it is in an ocean. This could create more opportunities for divergent evolution, speeding things up if you want to see a particular result, like intelligent life. However, it seems to me that there could be situations on other planets that can create a similar effect in a liquid environment. Perhaps not common, but possible. My point is, it might be chauvinistic to focus so much on conditions that allow the development of land-based life. The other, hidden chauvinism is towards carbon-based life, but it's hard to blame ourselves for that since it's so difficult to figure out how other kinds of life could work.
How do you know WE aren't the extremophiles?
Oceans full of a solvent, we breathe a caustic gas... and so on.
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There's more. The "uniquers" are clueless. Is the magnetic field because of our unique liquid core?
No. We have a lot of iron and rotate. Duh.
Moons! Look at the moons! Statistically most of the other rocks going around the sun have 'em, too.
And so forth. Statistically, we're in a zone that allowed the chemicals to make whoopee and produce life, leading to us. People believe they're special, but they evolved something that they narcissitically believe is "intelligence". Do they treat their little planet with care? I don't think so. And they kill each other with glee, and deny the world around them, waiting for magical-thinking to become real.
---- Teach Peace. It's Cheaper Than War.
That's one going theory, but there are good arguments for orbital capture also. The biggest one being the concentration of elements on the moon is different than those found on earth. The moon has a LOT of silicon on it for example, and very little carbon. If it was created by the splash from an impact, one would expect it to have at least a similar concentration of elements as the parent body. Elemental concentration doesn't change a lot over the course of a planet's existence, since elements are formed within stars and planets have to play with the hand they were dealt when they formed. Comets may bring in a little, and atmosphere may bleed away, but the lion's share of the ratio remains unchanged from beginning to end.
Right now the big hangup on that is we don't know a lot about the interior of the moon, other than it's solid. It's possible the surface of the moon just happened to wind up being mostly Si, and the interior is more of an earth-like distribution of elements. But when planets cool, heavy things go to the core and light things float on top, which is why earth has lots of carbon on the crust and iron in the core. You'd expect the same of the moon.
I work for the Department of Redundancy Department.
Contrary to popular belief among religious fundamentalists, most atheists are not anti-Christmas. It has become more of a cultural holiday than a religious one anyway; If you asked 100 people at random what Christmas was about, how many do you think would say "the birth of Christ", and how many would say "presents", "family" or "Santa Claus"?
The people screaming bloody murder about nativity scenes and whatnot are a small but vocal minority. Usually those zealous types are former Christians themselves, the rest of us don't really care.
There are 400 billion stars in our galaxy, and there are probably many billions of planets. Out of all those possibilities, how rare could it be for a planet to be in the "habitable zone" of a star, with a few gas giants farther out? And isn't iron a fairly common element in planets, hence molten core, hence magnetic field protecting the surface from cosmic rays and all that.
If we suppose that Earth-like conditions are one in a billion, which seems exceedingly conservative, nonetheless we're talking about dozens or hundreds of Earth-like planets out there. It's reasonable to suppose that our conditions are not that uncommon, and there might be an order of magnitude more Earth-like planets.
There also would be millions of planets that are much harsher than Earth, yet perhaps some form of life could have evolved.
A counter argument might be that even our world was not always friendly to life; during Earth's first billion years it was quite a harsh place indeed. Subsequently there were several mass extinction events, the last one a mere 60 million years ago. During pre-Cambrian times, it's believed the planet was basically a giant snowball. Alien probes sent here during those periods might have concluded that there was no sustainable life.
I think it will be a good 200 years before we can get out to some of our neighboring stars and investigate up close. Even the closest stars would take multiple lifetimes to get to using any current or upcoming propulsion technologies. Ultimately it will be some kind of intelligent robotic explorer that we send out as a kind of trans-generational emissary, that may come back to entertain our distant descendants with tales of foreign worlds. Sad that trans-light propulsion is nothing but a pipe dream, for now anyway.
it's = "it is"; its = possessive. E.g., it's flapping its wings.
Maybe, but it's pretty obvious that the GP to your post is anti-Christian.
Just like reality. Ok, reality isn't anti-christian, it's just that christian beliefs are disproved by reality.
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How is a post that is so obviously about Zeus considered "anti-Christian"?
kurzweil_freak
5th Kyu Genbukan Ninpo/KJJR student
Be the darkness that allows the light to shine.
Pardon in advance for any meanderings. Several interruptions while composing this.
And yet the Moon might well be the cause of several other factors.
The Moon is massive enough in comparison to the Earth that it is reasonable to consider the two to be a binary planet system in many ways. While the barycenter of the binary revolves around the Sun in a highly predictable ellipse, the Earth itself does not; it meanders inside and outside that elliptical orbit due to the Moon's influence. As a consequence, the location of the Earth's perihelion can shift more than one degree from one year to the next (varies from Jan 2 to Jan 4). The barycenter of the binary system is displaced from the center of the Earth toward the Moon by 75% of the Earth's radius (quick reference here), which from the point of view of a flat Earth theorist means that the barycenter is rushing along 1,000 miles beneath our feet at about twice the speed of sound.
And of course there are the tides.
Not just the ocean tides, but also the much greater tidal bulge of the atmosphere. And a definite tendency to a tidal bulge in the liquid core. IANAGeologist so I don't have a clue how the tidal forces and the weight of the mantle would interact... but then I think that most geologists have never considered this either since they are always looking down into the Earth and the Moon is for them a whoosh in the finest Slashdot meaning.
As far as evolution of life goes wrt planet Earth, the Moon is at the very least a major, significant stirring rod. It is really hard to say how major, since we are in the position of being stirred so everything else that is also being stirred with us looks very normal. It could be that both meteorology and geology need their Copernican revolution and won't really make sense until they meet their Galileos.
Will
if there is ONE case where it is true and your sample size is (nearly) infinitely large, the chance to find another case is 1.
Perhaps "nearly 1", but not 1. Case in point: There are infinite counting numbers, but only 1 even prime number (2). Surely with an infinite sample size, by your logic, you would expect multiple examples even primes?