Thursday, November 15, 2007

Why does the Earth have life?
Several things about planet Earth make it uniquely suite to life. The main one is abundant water. No other planet that we know of has the huge oceans we have, nor the many lakes and rivers. Water is a very important ingredient of all living things because it has many properties that no other substance has. All the important reactions that occur inside our cells require water, and all the organs in our bodies, such as the heart and lungs and liver, rely on being surrounded by water. Without water, life as we know it could not go on. Could there be a completely different kind of life form that is not based on water? Scientists have tried to imagine such life forms, but it is hard to see what could take the place of water.

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