habitable zone

From: Glenn Morton (glenn.morton@btinternet.com)
Date: Sat Nov 16 2002 - 16:16:47 EST

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    I found the following interesting passage in a recent magazine concerning
    the design in the earth's orbit which is often claimed by design advocates.
    The claim that a circular orbit is required for life may be wrong.

    ìAt an eccentricity of 0.3, the planetís orbit would pass inside the orbital
    path of Venus at perihelion and fly within 20 million miles of Mars at
    aphelion. In Pollardís model, though, even when Earth drew closer to the sun
    than Venus, it didnít develop a Venus-like climate. ëWater has a very high
    heat capacity,î Williams says,í so the large amount of water on Earth is
    slow to warm up.í And the heat wouldnít last long. As Kepler also explained,
    planets on eccentric orbits travel fastest at perihelion, accelerating
    furiously. ëWell before the oceans start boiling,í Williams says, ëthe
    planet is racing away.í
            ìAt the other end of an eccentric orbit, Earth slows down
    again. But here
    the climate model takes a strange and welcome turn. The planet absorbs so
    much heat during its brief trip around the sun, Williams explains, that its
    coldest months out by Mars are still warmer than winter months on a circular
    orbit: the average global temperature is 73 degrees Fahrenheit, versus 58
    degrees on Earth now. Itís not a perfectly regulated system: Some parts of
    the African South American, and Australian interiors heat up to 140 degrees
    at perihelion. But the extreme temperatures only last a month or two."
    William Speed Weed, ìCircles of Life,î Discover, Nov. 2002, p. 44-46

    glenn

    see http://www.glenn.morton.btinternet.co.uk/dmd.htm
    for lots of creation/evolution information
    anthropology/geology/paleontology/theology\
    personal stories of struggle



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