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Earth Space Science

Is the Earth Special? 745

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."
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Is the Earth Special?

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  • But... (Score:3, Insightful)

    by Anonymous Coward on Saturday December 10, 2011 @11:22AM (#38325838)

    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.

    • Re:But... (Score:5, Informative)

      by seandiggity ( 992657 ) on Saturday December 10, 2011 @11:48AM (#38326122) Homepage

      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 [wikipedia.org]

    • Re:But... (Score:5, Interesting)

      by v1 ( 525388 ) on Saturday December 10, 2011 @12:32PM (#38326558) Homepage Journal

      Didn't the Earth get hit by another planet, causing it to shoot a ton of crust into orbit..creating the moon?

      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.

  • Life Adapts (Score:5, Insightful)

    by Anonymous Coward on Saturday December 10, 2011 @11:25AM (#38325864)

    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.

    • Re:Life Adapts (Score:4, Insightful)

      by Vinegar Joe ( 998110 ) on Saturday December 10, 2011 @11:28AM (#38325894)

      All life really needs is a liquid solvent, energy, and enough time.

      So where is everybody?

      • Re:Life Adapts (Score:5, Interesting)

        by Anonymous Coward on Saturday December 10, 2011 @11:32AM (#38325948)
        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?"
        • You are also making a mistake in logic. If other life is so intelligent, why would it have anything to do with us?

          • by pclminion ( 145572 ) on Saturday December 10, 2011 @12:23PM (#38326460)

            If other life is so intelligent, why would it have anything to do with us?

            Because we are edible?

        • Re:Life Adapts (Score:5, Insightful)

          by Surt ( 22457 ) on Saturday December 10, 2011 @12:11PM (#38326346) Homepage Journal

          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.

          • Re:Life Adapts (Score:5, Interesting)

            by TrevorB ( 57780 ) on Saturday December 10, 2011 @01:31PM (#38327236) Homepage

            Dyson Spheres. Explains all the dark matter. ;)

          • Re:Life Adapts (Score:5, Interesting)

            by melikamp ( 631205 ) on Saturday December 10, 2011 @01:42PM (#38327380) Homepage Journal

            They should have had plenty of time to fill the galaxy by now.

            This is a big unfounded assumption. And while jump-starting life and moving bacteria around may turn out to be easy, moving animals the size of humans to a star system even 20 ly away is already known to be very, very hard. (I mean, mammals could not reach New Zealand for millions of years, and that's another continent, not another star.) And while colonizing deep space is a priority, persisting without a big chunk of rock in the immediate neighborhood is probably a pipe dream. So we should probably think of it as a planet-sized organism (like Earth with its biosphere) casting a seed (a generation ship) to a different star system. One needs to find a planet that's already ripe; being optimistic, there is one within a few dozen ly. One needs to build a big ass ship in deep space, capable of withstanding a several (or many) thousand year journey with a self-sustaining biosphere inside, so probably something like an asteroid several hundred meters in diameter. Then one has to accelerate the sucker with something at least as good as fusion and slowly crawl towards the goal. Just the travel itself is easily 100000 years, and building an ark is a tremendous job as well. Once arrived, colonists cannot hope to propagate again for hundreds of thousands or may be millions of years, since they don't have a planet backing them, so there is more downtime.

            Think about what I like calling a "hop time": the mean duration needed for a generation ship to colonize a planet, build a new generation ship, and travel to the next system. It's gotta be pretty big, may be a million years, may be 10. So if someone has a billion years on us, they may be on their 100-1000th hop. They are but a smidgen, may be as big as the width of the galactic disk. And if they are on the other side of the galaxy, we may not run into them for another few billion years.

          • Re:Life Adapts (Score:5, Interesting)

            by Dogtanian ( 588974 ) on Saturday December 10, 2011 @01:45PM (#38327408) Homepage

            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?

            • Re:Life Adapts (Score:5, Interesting)

              by Surt ( 22457 ) on Saturday December 10, 2011 @02:08PM (#38327698) Homepage Journal

              No, your theory has definitely been considered by many. Technological singularity changing the priorities of the civilization and/or rendering it invisible is definitely a possible explanation for the missing gating factor. That escape from the universe might be possible with a technology only slightly ahead of our own would explain everything (because this universe with its stupid second law of thermodynamics is a dead end that any reasonably advanced civilization would WANT to leave).

        • Re:Life Adapts (Score:4, Insightful)

          by Runaway1956 ( 1322357 ) on Saturday December 10, 2011 @12:21PM (#38326438) Homepage Journal

          No FTL? That's a proven fact - how? Those who assume that no possible sentient beings throughout the galaxy have ever built an FTL also ASSume that our knowledge of physics is flawless.

          What we need is another bizarro, like Einstein, to stand the world on it's head. Someone who can look at all those computations, spot a couple of mistakes, draw a few conclusions, and come up with a hypothesis. What if, Einstein were only 85% correct?

          I'm not about to go out on a limb, and say that FTL_is_possible, but neither will I go out on your limb, and say that FTL_is_not_possible.

          I think - not a statement of fact, but an opinion - that FTL is probably possible. There are at least tens of thousands of questions to be answered before it becomes a reality, but I think it's possible. The energy required to power a ship large enough for a crew of ten, and say a hundred passengers would be more than astronomical - but possible.

          And, do you know what? The jury is still out. You can't prove the impossibility, any more than I can prove the possibility. We'd get the same mileage arguing whether there is a god or not.

      • Life does not necessarily equal an advanced technological civilisation that we could detect or understand, not to mention that there's plenty of theories that may account for Fermi. The Doomsday argument [wikipedia.org] and the Singularity [wikipedia.org] are just 2 possibilities. There's plenty more, the problem is that until we actually find another civilisation, evidence of one, or conclusively prove they don't exist now or haven't existed... then we're still left with the paradox.
      • Re:Life Adapts (Score:5, Interesting)

        by rubycodez ( 864176 ) on Saturday December 10, 2011 @12:34PM (#38326584)
        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.
    • I've got a hamster and nail polish remover. How long is this going to take?


    • Re:Life Adapts (Score:5, Interesting)

      by ComaVN ( 325750 ) on Saturday December 10, 2011 @11:36AM (#38325992)

      Indeed. A civilisation on a tidally locked planet would probably think life couldn't possibly start on a planet with day and night, or seasons.

  • I can already hear the "intelligent design" folks jumping on this topic as proof that we aren't here through random chance but were assembled by some creator. Just as an FYI, the "rare earth hypothesis" [wikipedia.org] has been circulating in the scientific community for many years.

  • Why are conditions that promote life rarer than ones that prevent it?

    • Because we only know a limited set of conditions that promote life, and a lot of ones that as far as we can tell prevent it. This understanding may change as we discover more.
  • by Wonda ( 457426 )

    If the tides are so helpful, why did we evolve from fresh water amphibians? It seems they're just making it up!

  • by QuasiSteve ( 2042606 ) on Saturday December 10, 2011 @11:30AM (#38325910)

    All 7.5 of them born every single minute in the U.S. alone.

    Source: http://www.census.gov/population/www/popclockus.html [census.gov]

    ( Although I have to admit, that 0.5 baby is pretty darn special. )

    Maybe they should define the lower bound for 'special' before even pondering whether or not the Earth falls within the definition. Then, if it doesn't, they can raise that lower bound until it does.

  • by decora ( 1710862 ) on Saturday December 10, 2011 @11:31AM (#38325918) Journal

    "In the air, there is no way for Oxygen to enter our gills. Therefore, water is extraordinary!"

    • Water is extraordinary. It is one of the few substances that is less dense as a solid than as a liquid. This is a property with significance for aquatic life forms as aquatic life would have somewhat greater difficulty surviving in cold climates without that property.
  • Judging by the people on it, it's special alright. I'm pretty sure it took the short bus to the Milky Way.
  • Cop Out (Score:2, Insightful)

    This is the same thing religious leaders expouse, "what we can't explain must be special and unique". In a universe, nothing is unique. Except for snowflakes.
    • Re:Cop Out (Score:4, Insightful)

      by phantomfive ( 622387 ) on Saturday December 10, 2011 @12:05PM (#38326280) Journal
      And yet you do have to prepare yourself for the fact that it is a possibility. Though the article doesn't say unique, just very rare. Which may be a way of saying, that of the 708 exo-planets so far identified, not a single one may be habitable by life. I believe that's why the topic has come up again now, as a response to the articles claiming we might have found a planet capable of supporting life (like this one [slashdot.org]).
      • Re:Cop Out (Score:4, Informative)

        by Black Parrot ( 19622 ) on Saturday December 10, 2011 @01:48PM (#38327442)

        of the 708 exo-planets so far identified, not a single one may be habitable by life.

        Our methods preferentially find gas giants in close orbits.

        If only one star in a billion harbors a habitable planet there will still be a couple of hundred in our galaxy, and a few trillion in the observable universe.

    • by mcgrew ( 92797 ) *

      In a universe, nothing is unique. Except for snowflakes.

      Each human being is unique. I'm not so sure about snowflakes.

  • by jrq ( 119773 ) on Saturday December 10, 2011 @11:36AM (#38325990)
    "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.
  • by rbrander ( 73222 ) on Saturday December 10, 2011 @11:38AM (#38326016) Homepage

    What's exciting about the recent exoplanet work is that we're actually filling in the first few parameters of the Drake Equation. We're getting a grip on how common planets are, and now how common it is for them to be (a) not gas giants and (b) in the right zone around the star. I think those two alone (combined with "how many stars are like ours", which we have known a long time), knock off a good four orders of magnitude - from hundreds of billions of stars in this galaxy to tens of millions that are 1) not short-lived stars ; 2) have non-gas-giants that are 3) in the "habitable zone".

    We already know enough from extremophiles on earth that anything with liquid water, practically, is "habitable zone".

    What we can get from just closer examination of our own solar system whether life NOT "as we know it" happens - did it arise in liquid methane, or floating about in Jupiter's atmosphere and all that. And if it does, how complex does it get?

    These "special conditions" may not be necessary for *life*, but they may be necessary for it to bother (sorry, "have reproductive advantage") going past single cells, which biologists still consider a pretty Great Leap Forward.

    It may well be; until we're not extrapolating from one data point, speculation is just entertainment. If it turns out complex life happens only every trillion stars and there's only one other in the "local group", ten million light-years from here, well...rats. Just ourselves to talk to.

    Console yourself with this: it means our celebrities are even MORE important than we ever imagined. "Miss Universe", for instance, really IS Miss Universe!!

  • 1 in a million (Score:4, Interesting)

    by carpefishus ( 1515573 ) on Saturday December 10, 2011 @11:42AM (#38326072)
    If our solar system is so special that it is one in a million then there are about 200,000 systems that are as special as ours in the Milky Way. Multiply this by 100 billion to one trillion galaxies and we are really not that special.
  • by pecosdave ( 536896 ) * on Saturday December 10, 2011 @11:52AM (#38326160) Homepage Journal


    Now I like boobs as much as the next guy. As a matter of fact what got my mind started down the track is staring at alien boobs on all of my favorite SciFi movies and I started thinking to myself "You know, those are kind of weird as far as life is concerned".

    I'll use life on our own planet as an example. Only mammals have boobs.

    Other animals do indeed feed on another, there's a lot of really unappealing vomit sharing in many types of life and poop sharing in the insect world that I think would probably be more common among the stars (Slurm for example) as it's even more common here. There are nutrient transfers that happen on our planet that are different than the insect ones I just mentioned might be out there as well as some we haven't thought of, but I keep thinking of boobs, cause I think of them all the time, and I just don't see them as something that are likely to exist on alien babes. I'm not discouraging my favorite Sci-Fi writers by any means, whatever happens keep the boobs on your alien babes, but when I think of the possibility of meeting real alien babes it saddens me when I realize evolution is unlikely to have included boobs into the equation.

  • Yes. (Score:3, Insightful)

    by sgt scrub ( 869860 ) <saintium@yahooUMLAUT.com minus punct> on Saturday December 10, 2011 @11:57AM (#38326206)

    The Earth is special. Humans are only here because of the great beardy guy in the sky. Now that this massively important issue is settled can we get on with colonizing Mars? Please?

  • by LastDawnOfMan ( 1851550 ) on Saturday December 10, 2011 @11:59AM (#38326226)
    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.
  • by lexsird ( 1208192 ) on Saturday December 10, 2011 @04:37PM (#38329226)

    Aliens don't stop because they are busy searching for INTELLIGENT life.

    Dear Aliens,
    Don't be racist, Thank you.
    The People of Earth.
    P.S. Do as we say, not as we do.

    Why did the human cross the road?
    Because he's still stuck on his planet and can't fly.

    A human walks into a bar with some Uropian gas termite his shoulder. The bartender before he throws them out asks, "Where did you get that disgusting thing?"
    The gas termite says "On planet Water, these dumb fucks are everywhere."

    Do you remember in High School the retarded kids and their classrooms? Did you ever go in them? Did you know the retarded kids? Don't feel bad, nobody did. You knew where they were though so God forbid you stumble anywhere near there and be mistaken for a retard. If retards spoke, you just ignored them. Well I hate to tell everyone, but Earth is the Retard Class of the Galaxy. There are plenty of Aliens out there that know damn well where we are. But do you see them coming here? They don't want any of that "retard" rubbing off on them. Oh sure, we get sightings and such, but nothing official. Do you know why? These are the Aliens that are throwing spitballs at us and calling us RETARDS and running the hell off before they end up in detention or suspended.

    "Why?" do you ask????

    Well imagine our Alien benefactors who waited breathlessly and patiently for us to come out to space and prove we are intelligent. Who do we send? A dog! Imagine that? So they do a mind probe to find out WTF it wants and it wants a bone. They consider the situation and just leave and chock us all up for being retarded.Word gets around you know. Yeah...that new planet..? It's retarded!

    So you ask me, is Earth special? I say yeah, it's special alright, it's Special Ed.

1 1 was a race-horse, 2 2 was 1 2. When 1 1 1 1 race, 2 2 1 1 2.