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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."
Why do you think that life on other planets would have anything different from us resource and technology-wise? Unless you think the laws of physics and the Periodic Table of Elements are purely local to Earth? What we have now is whatever anyone else anywhere else would have. We won't have FTL spaceships, neither will they. Why is this so hard to understand? There's no Fermi's Paradox, there's only the Space Nutter Paradox: "Given what we know as FACTS, why would you think any other intelligent life would have more capacities than us?"
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.
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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.
Consider that in less than 500 million years, the earth will be too hot to support life. So that means there is a race, the 5 billion year race from when our solar system began to that extinction time. Maybe most other planets with life lost that race, before anything could overcome the limits of their sun's cooking their home world.
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.
Your mistake is in assuming that the starter gun fired at the same time for everyone. That isn't true, we're late to the game. Other planets finished forming and starting up their life engines more than a billion years before ours did. The question is, where are those folks? They should have had plenty of time to fill the galaxy by now.
Thing is that mankind only arrived on the planet *very* recently in evolutionary terms. In addition to this, we've made incredibly fast levels of progress in the past few thousand years, and the past hundred years has seen technological change orders of magnitude faster than *that*.
It's fair to assume that this process hasn't stopped yet- the logical conclusion some have drawn is the "singularity". Well, whether or not that happens, the bottom line is that we're in the middle of a change that's happening incredibly suddenly- the blink of an eye, the flash of a camera bulb- compared to the relative "hours" or "weeks" that life has existed on the planet overall.
Now, there *may* be a significant number of other worlds that are presently capable of supporting life out there, i.e. at the same time as ours. But even if there are (e.g.) hundreds of them, even if they *broadly* follow the same trajectory and timescale as earth (in terms of the evolution of life), even if their development was congruent to ours in the larger scale of things, the chance of even one other world's "camera flash" evolutionary moment occurring at exactly the same time as ours is incredibly small.
This matters because if they're even slightly behind, they're probably still at the monkey-level intelligence stage (if we're lucky), or the stage earth was at tens or hundreds of millions of years ago.
If they're even "slightly" ahead- e.g. a million years on the evolutionary scale of things is pretty "close" to us- then they're probably so far ahead of us that we won't even be able to begin to comprehend where they've gone, assuming their development (even if it eventually slowed down) went through the rapid phase that mankind is going through- and continued, even if only for a few thousand years!
This does assume that mankind's current rate of development can be continued at least for the immediate future. Still, I'm surprised that I haven't seen the above issue even considered elsewhere. Maybe I overlooked something obvious?
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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