July 13, 2008 | David F. Coppedge

Love Your Planet

Modern astronomy and space travel have given humans the ability to view the earth from a distance and ponder its significance.  Some astronomers expected the earth to be ordinary-looking.  In many respects, however, astronomy is teaching us otherwise.  Clara Moskowitz, staff writer for Space.com began an article by saying, “Earth is one special planet.”
    What makes the earth special?  Let her count the ways:

  1. Liquid water in abundance – but not too much water to submerge the continents.
  2. Plate tectonics and active geology.
  3. A magnetic field that shelters it from harmful solar radiation.
  4. The only planet known to have life.
  5. The only planet known to have intelligent life.
  6. The only known planet hosting intelligent beings who have achieved space travel.
  7. An environment that has kept water liquid for a long time.
  8. A safe distance from its star.
  9. A carbon-silicate cycle that has operated for a long time.
  10. The right size to hold onto an atmosphere, yet have a habitable surface.
  11. A moon the right size and distance to stabilize earth’s tilt and rotation.
  12. A moon that circulates the ocean tides.

Moskowitz entertained hopes that astronomers will find billions of earth-like planets eventually, but her list of unique features of the home planet is impressive.  No other planet or moon in the solar system comes close: not Venus, Mars, Jupiter, or Titan.  No other body is in the “Goldilocks” position of being just right.  And “So far,” she added, “we haven’t seen any planet outside the solar system come very close to Earth either.”  Of the extrasolar planets discovered so far (going on 300), many are “hot Jupiters” or gas giants as close in as Mercury to our sun, or even closer.  An earth-like planet could not compete in the habitable zone of such a system.
    She quoted Donald Brownlee, co-author of Rare Earth (12/19/2000, 07/15/2002) and project scientist of the Stardust mission (01/02/2004, 01/25/2008), who said, “I doubt that in our galaxy typical stars have planets just like Earth around them.  I’m sure there are lots of planets in the galaxy that are somewhat similar to Earth, but the idea that this is a typical planet is nonsensical.”  See also the 04/04/2005 entry, where five astronomers on a panel agreed that our solar system is special.

Brownlee appeared briefly in the DVD The Privileged Planet explaining his view about the uniqueness of earth.  The unique properties listed above and more are discussed in the film – along with a thought-provoking hypothesis about why these features point to intelligent design.  The production includes startling admissions by a variety of astronomers, some hostile to intelligent design but struck by the facts of nature.  If you haven’t yet seen this powerful and beautiful film, order a copy today.  It makes a nice loaner and conversation starter.

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