A host of recent discoveries suggests that complex life is less pervasive in the universe than previously assumed. Although it cannot be proven that complex
life is rare elsewhere in the universe, based upon a through examination of intergalactic history, we
can generalize its probability. If we eliminate our subjectivity on the abundance of life that surrounds us, and reexamine the conditions that allow complex life from a truly
universal perspective, then we may begin to objectively experience the rare attributes of the planet in a new light.
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| Even among thousands of galaxies are there many environments able to sustain life? |
In this discussion it is important to distinguish between life and complex life. Life is defined as everything from single cell bacteria to large mammals, where as complex life is viewed as the symbiotic relationship between multi-celled organisms and their environment.
Recently, bacteria has been found to exist in the harsh climates of some asteroids and moons. However, complex life such as found on earth not only needs a mild
environment, but an environment that remains stable for a relatively long period of time.
It took two billion years for earth's ecosystem to produce the amount of oxygen
needed for the survival of complex species. This evolution occurred due to the stability
of the sun. The sun's relatively large size allows for the creation of energy
over a long period. Had the sun's energy experienced a greater degree of
variation, there would have been little chance for
evolution to occur. Therefore the development of complex life in an environment
with a more inconsistent energy source, such as planets orbiting variable stars,
or planets orbiting stars in binary or tertiary stellar systems, is very
improbable. Other factors such as the frequency of galatic impact and a consistent orbit help to maintain the stable conditions that support complex life.
Miraculously in the planet's long history it has not only avoided galactic hazard, such as impact from a comet or asteroid that was catastrophic enough to
completely eliminate life, it has maintained the ideal orbit to support life.
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| Earth may be the only habitat that supports life with in 10,000 light years. |
It is situated at a suitable distance from the sun to maintain liquid
water, not too close for the water to evaporate, and not far enough for it to
freeze. In addition, Earth is the only planet in the solar system (besides
Pluto) with a moon of comparable size, and the only planet with plate
tectonics. Both of these characteristics allow for a more diverse planetary
topography and ecosystem. The "habitational zone" created by the the size of the sun, the earths distance from it, the degree of orbit, and the planet's placement in the solar system all contribute to the unique conditions needed to support and maintain complex life. Habitational zones in which complex life can exist are also
found on a galactic level. The tightly packed interior composed of star
clusters and supernovas and the low percentage of heavy metals present in the
exterior are unsuitable for complex life. With more information an argument may
soon be made that even galactic placement within the universe may play an
important role in providing stable environmental conditions. What if earth is the only planet with complex life with in a few
thousand light years? What if the ecosystem found on earth is truly unique in
the galaxy or even the universe, an island of life amid an endless sea of space?
If this is the case so much greater the loss caused by the careless destruction
of life.
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