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Our home, the Earth, rises over the moon during the Apollo 11 mission.
FILE/NASA
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Give thanks for life on planet Earth
Giving thanks for our world
Date published: 11/1/2007
AS WE GIVE thanks this month, I am reminded of a question my 9-year-old son recently asked me. He wanted to know why the Earth could sustain life while other planets in our solar system are lifeless places.
Although he did not realize it, his question was a fundamental one that has continually intrigued astronomers. Is ours the only planet in the universe where intelligent life has been able to prosper?
Mercury, Venus, Earth and Mars are the four inner planets of the solar system. The inner planets are small, rocky worlds, while the outer planets of Jupiter, Saturn, Uranus and Neptune are large and gaseous.
Sometime during the formation of the solar system, our planet began to differentiate itself from its solar system brethren. Earth contained a hospitable atmosphere, with oxygen and copious amounts of liquid water on its surface.
In addition to possessing life-giving water, our planet's temperature is neither too hot nor too cold for life to exist. Our distance of 93 million miles from the sun happens to be in the solar system's region where life could flourish.
Astronomers take these and other factors into consideration as they study the possibility of life in the universe beyond our solar system.
In 1961, astronomer Frank Drake devised his famous equation, which attempts to mathematically estimate the numbers of intelligent civilizations in the Milky Way. Try it yourself at pbs.org/lifebeyondearth/listening/drake.html.
Even before Drake's equation, astronomers had speculated that stars outside our solar system probably had planets orbiting them. However, the technology did not exist to support the theory until 1995, when the first planet outside our solar system was discovered.
Since then, more than 250 planets, most of them gas giants like Jupiter, have been discovered orbiting distant stars in our Milky Way galaxy. Most recently, astronomers using NASA's Spitzer Space Telescope have discovered an Earth-like planet forming 424 light-years away from us.
In addition, a new space mission to be launched in early 2009 named Kepler (kepler.nasa.gov) will concentrate on finding Earth-like planets around distant stars.
As techniques and technology continue to slowly improve, our discoveries will become more intriguing. But will we ever have a definitive answer to the question of life beyond Earth?
Date published: 11/1/2007
Most recent reader comments:
Wouldn't it be awful.....
(posted by
pinkphantom
, Nov. 1, 2007 9:18 am)
if Earth was the only planet in the universe with life? However, I believe that life exists on millions of planets in the universe and that variety of life runs the spectrum of possibilities. I believe there are civilizations far more advanced than we are as well as planets existing with their own primordial soup. It would be fantastic if one of those advanced civilizations could visit us and give humanity a real lesson in what is important. It certainly would change humanity's priorities!
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