The Earth has been around for about 5 billion years, and has about another 5 billion years to go. It has been cooling since its formation, and its surface temperature has stabilized within about 100 degrees F of the freezing point of water. This is critical, as liquid water appears to be a prerequisite condition for life.
As the Earth cooled, what we would consider a poisonous atmosphere evolved, containing high concentrations of methane and some ammonia. "Hard" ultraviolet radiation provided energy to get molecules to react in the early oceans, and biochemical processes began. Oxygen, then a poisonous byproduct, began to accumulate in the atmosphere; aerobic life flourished. As climate conditions altered, life forms altered as well, and will continue to do so. Atmospheric changes 65 million years ago killed off the dinosaurs; several "Great Dyings" have been found throughout the Earth's history in the geologic record. Human population continues to increase, but will begin to slow and decline. Increasing carbon dioxide production by human activity has exacerbated what may be a naturally occurring climactic warming trend. The increase in carbon dioxide in the atmosphere is now considered a poisonous byproduct. Although humans may live or survive upon the Earth, or may not, the Earth will continue to exist with some kinds of life. However, all life will cease on the planet when the Sun goes nova in several billion years.
No comments:
Post a Comment