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View Diary: Getting to Know Your Solar System (5): Earth (Vol. 2) (44 comments)

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  •  So, let me get this straight (6+ / 0-)

    The core is molten because we have plenty of Uranium, Thorium and other radionuclides generating heat.  The molten core is mostly iron-nickel  because of a massive impact which spun off Luna.  Luna in turn helps stabilize the spin axis of the earth bringing long-period climate stability, and it helps keep the core hot via tidal friction.  The magnetic and molten core in turn generates a strong magnetic field that protects the atmosphere from being stripped of water via high energy particles of the solar wind.  Without this magnetic shield, there would be no life on earth because the planet would be desiccated by now!  

    So without the relative abundance of radionuclides and that big early mega-impact there wouldn't be life as we know it!?  

    Wow!  

    It is incredible how dependent our existence today is on the many, many interconnected chance factors that have occurred over geologic time.  Who needs religious mythology when reality is so much more incredible!

    The intrinsic nature of Power is such that those who seek it most are least qualified to wield it.

    by mojo workin on Fri Sep 09, 2011 at 06:57:50 AM PDT

    •  Yes, I keep getting more and more struck by how (4+ / 0-)
      Recommended by:
      Troubadour, Jantman, Russgirl, alefnot

      lucky that collision was for us. Spinning us up, keeping the poles stable, giving us a magnetic field and therefore letting us keep our water, tides for biodiversity and perhaps life itself. Yet the collision itself seems like a very unlikely hit, given how huge space is.

      Is it true? Is it kind? Is it necessary? . . . and respect the dignity of every human being.

      by Wee Mama on Fri Sep 09, 2011 at 08:27:09 AM PDT

      [ Parent ]

      •  Actually, we were spinning very fast (2+ / 0-)
        Recommended by:
        Wee Mama, LokiMom

        before the impact - the Moon has been slowing us down through tidal effects.  It's been "stealing" a large amount of the Earth's angular momentum and spiraling slowly outward.  The planet that would have existed without the impact would be a very weird object, with a day lasting only a few hours and an axis that wobbles chaotically over million-year scales.

        The probability of the impact was actually relatively high under the formative conditions of the early solar system.  Remember that Venus was hit by a giant impactor too that reversed its rotation, and Mercury had originally been the core of a larger body before having most of its mantle stripped off by another giant impactor.

        The conundrum of stable democracy: Reform requires the consent of the corrupt.

        by Troubadour on Fri Sep 09, 2011 at 11:49:06 AM PDT

        [ Parent ]

        •  Getting hit, yes, I believe that's likely. Getting (1+ / 0-)
          Recommended by:
          Troubadour

          hit by something big enough but not too big, that hits at an angle that makes things better and not worse: I'd love to know what the odds are for that.

          Is it true? Is it kind? Is it necessary? . . . and respect the dignity of every human being.

          by Wee Mama on Fri Sep 09, 2011 at 12:34:42 PM PDT

          [ Parent ]

          •  That's true - it is small. (2+ / 0-)
            Recommended by:
            Wee Mama, some other george

            But on the scale of the universe, the odds are essentially certain.  It's only if we insist that there is anything special about a particular location that the odds look outsized - then we ask "But how likely was it to happen here?"  But "here" would be wherever it happened to occur - if not this solar system, then some other one.  The conditions that lead to intelligent life are precisely the ones that end up being observed.

            The conundrum of stable democracy: Reform requires the consent of the corrupt.

            by Troubadour on Fri Sep 09, 2011 at 12:42:41 PM PDT

            [ Parent ]

            •  Understandable to think so, but the more variables (1+ / 0-)
              Recommended by:
              Troubadour

              the lower the final odds. I taught a seminar class with an astronomer once about Rare Earth. Toward the end of the class we took the classic equation for how many planets with advanced civilizations, added a few variables that had been identified more recently and broke the class up into groups to get estimates for all the variables. Only we told them to look at a range of estimates, and to bring back the most optimistic and most pessimistic estimates.

              When we evaluated the equation with all optimistic numberes, it predicted a billion planets with advanced life in our galaxy. When we used all pessimistic numbers, it predicted eight.

              It will be interesting to see where it all goes. No one (or very few) predicted the hot Jupiters, and what they are telling us about alternate pathways to forming planetary systems. Time may tell.

              Is it true? Is it kind? Is it necessary? . . . and respect the dignity of every human being.

              by Wee Mama on Fri Sep 09, 2011 at 12:53:24 PM PDT

              [ Parent ]

              •  In the last diary in this series (2+ / 0-)
                Recommended by:
                Wee Mama, Russgirl

                I intend to explore some thoughts about alien civilizations and some of the more likely scenarios for discovery.  The reality wouldn't be like any movie that's ever been made - no dramatic appearances, and no SETI greetings.  Just a gradual understanding that anomalous readings from a distant star system result from artificial activity.

                The conundrum of stable democracy: Reform requires the consent of the corrupt.

                by Troubadour on Fri Sep 09, 2011 at 01:47:08 PM PDT

                [ Parent ]

    •  The core would be nickel-iron anyway (0+ / 0-)

      but it would be smaller.  All solid bodies that form from accretion have an iron core - only those which are created by being blasted off a larger body lack iron.

      As to the many chance events that life depended on, I tend to subscribe to the anthropic principle: Basically, the only possible way conditions can be observed at all is for those conditions to have led to life and intelligence, however improbable the chain of events, so by unavoidable selection bias all such observations will involve a large number of coincidences.  Highly probable circumstances will not lead to being observed.

      The conundrum of stable democracy: Reform requires the consent of the corrupt.

      by Troubadour on Fri Sep 09, 2011 at 11:42:14 AM PDT

      [ Parent ]

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