Planet Earth Only One With Life
Why is the earth the only planet that things can live on?
We do not know the answer to this question -- one way or the other.
Earthlings have not identified such planets, which may be less "advanced"
than Earth, "equivalent" to Earth in technological capabilities, or "far
more advanced" than our global culture. It is not even a "given" that their
evolution (I know that is an inflammatory word.) has developed along the
lines of carbon based chemistry as has life on Earth. It may be better, or
worse. We also have to realize that our ability to 'communicate' with any
such hypothetical life has a narrow time "window" given the finite speed
of light and our technological capabilities that are only about 100 years
old. So, without any prejudice, we just do not, cannot know if there is
another astronomical body that harbors life, or life'like' organisms.
There are many reasons why the Earth is "just right" for life.
If a planet is too close to the Sun, it will be too hot to support life as
we know it. If the planet is too far from the Sun, then it will be too
cold - water, which we know is important to the kind of life we are used
to seeing will be ice, and that is not useable for life.
Also, how much mass (how heavy) the planet is also has an effect on how
much air the planet can hold onto. If the planet's gravity is too weak the
air escapes into space.
Also, the fact that the Earth has a moving molten iron core provides a
magnetic field which shields life from the more harmful radiation from the Sun.
But, having said all that, we have to be careful and say that Earth is
just right for the kind of life that we know - as we know life to be.
There may be other planets that can support life, but it may be a kind of
living thing that is very different from what we see on Earth.
Greg (Roberto Gregorious)
Click here to return to the Astronomy Archives
Update: June 2012