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View Diary: A Plausible Scenario for Detecting Alien Civilizations (64 comments)

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  •  But will they have 1 moon the same size (5+ / 0-)

    in the sky as their 1 sun?

    •  That (4+ / 0-)

      is an utterly fascinating question.

      How rare is that phenomenon? Is it a coincidence that we experience it? or is that precise arrangement essential for the incubation of intelligent life?

      The cynic in me says the former and the dreamer says the latter.

      "Violence is the last refuge of the incompetent." - Isaac Asimov

      by Hammerhand on Sun Apr 08, 2012 at 11:18:53 AM PDT

      [ Parent ]

      •  Well, it's not just the size of the moon. (0+ / 0-)

        It's the fact we were gifted a much larger planetary magnetic core than we otherwise would have had by the same impact that formed the moon according to current theories.

        So we have the moon as a big close target for impactors that would otherwise hit us, and a big strong magnetic field to keep a lot of cosmic radiation and solar wind material away from us.

        Add in Jupiter as the solar system's vacuum cleaner, as I've heard some astronomers refer to it, and a lot of the extraplanetary dangers to life become much less dangerous than they otherwise would have been - and there are a large percentage of extrasolar planetary systems with Jupiters or larger out past the apparent zone of habitability (inside, and the attracting effect isn't going to be a shield for anything inside the zone, if I understand correctly).

        So it's less the apparent size of the moon, and more the things a moon that large - and the formation of it - mean for the overall local environment.

        Prayers and best wishes to those in Japan.

        by Cassandra Waites on Tue Apr 10, 2012 at 10:01:38 AM PDT

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    •  I'm not sure the relevance of the question. (4+ / 0-)

      The Moon used to be a lot bigger in the sky, and in the future will be a lot smaller.  It's been receding from the Earth through tidal acceleration ever since its birth.  The fact that we live in an epoch right on the cusp where total eclipses are still possible is most likely a coincidence.

      Technology is a compromise: You can use whatever tool you choose, but be assured it will use you back.

      by Troubadour on Sun Apr 08, 2012 at 03:00:33 PM PDT

      [ Parent ]

      •  Yes, it's even more rare in terms of time (2+ / 0-)
        Recommended by:
        subtropolis, Troubadour

        Appearing to be the same size in the sky is, by definition, subjective.  But it seems that we're in the middle of a period of about 60 million years starting around the beginning of the oligocene when they could seem the same size -- the moon was visibly bigger in the time of the dinosaurs.  So, that's less than 1 percent of the earth's existence!

        I'm not sure but what all moons don't have that mechanical effect of moving slowly away.  Meaning that any planet with one reasonably sized moon would probably go through such a (brief) period.

    •  That's no moon! (2+ / 0-)
      Recommended by:
      Troubadour, Knucklehead

      All things in the sky are pure to those who have no telescopes. – Charles Fort

      by subtropolis on Sun Apr 08, 2012 at 03:31:56 PM PDT

      [ Parent ]

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