Hey Mr. Green,
Why is there air? —Anonymous

Mr Green answers:
Ooo-wee, I just love these big questions. They remind me of those probed in Time magazine cover stories, like "Who Was Moses?" "Is Government Dead?" "Is God Dead?" "Is God Coming Back to Life?" (Verily, folks, thus hath Time spoken.) In the beginning, there was air, but not the marvelous kind in which we now exist. Go back 4 billion years, and the air was made up of assorted combinations of suffocating gases like carbon dioxide, methane, hydrogen sulfide, and nitrogen. Then, around 2 to 3 billion years ago, cyanobacteria (a.k.a. blue-green algae) figured out how to release oxygen by extracting it photosynthetically from carbon dioxide and water.

This was followed by the appearance of plants that produce oxygen, accelerating the 2-billion-year process in which the oxygen content in the atmosphere increased from close to nothing to the 20 percent level of today. Of course, there were all sorts of other complicated geological, chemical, and biological changes that cooperated in this development. Kinda makes you wonder about the arrogant polluters trying to undo this amazing atmospheric accomplishment--and the loopy zealots who deny that evolution ever happened. It's hard to say which group is more annoying: the former, who play God, or the latter, who claim to know exactly what He's been doing since the beginning of time.
Environmentally,
Mr. Green