That's cold enough to freeze carbon dioxide and form an ice cap of dry ice. Temperatures at the equator on Mars are comparable to the temperature found in the polar regions on Earth, but on the Martian poles the temperature plunges to about 180 degrees below 0. If the earth were smaller, its gravitational pull would be reduced and, like on the Moon, the atmosphere would be lost in space.

Mercury has an average temperature of 500 degrees. On Venus, the temperature is as high as 900 degrees. If the earth were closer to the sun, the intense heat would cause the gases to escape-just like vapor escapes from a boiling pot of water. The following chart shows the composition of the atmosphere-and are we ever lucky! There's just the right mix of oxygen and nitrogen to support life and achieving that mix was no easy matter.Ĭomposition of the atmosphere. The following figure shows that balance.īecause the atmosphere consists of a group of gases, it must have some weight.

You really can feel it when the pressure changes within the atmosphere. But if you had an operation, an injury, or maybe a connective-tissue disease (such as arthritis), your body might not be in exact, natural balance with the surroundings. Nobody really collapses and hardly anyone is even aware of the heavy air. So 10 tons of air may be resting on you, but another 10 tons are pushing outward from inside your body. Why don't we collapse under such pressure? Fortunately, our bodies exert from within an equal pressure to the atmosphere. But the atmosphere is floating and there's nothing feathery about it: Ten to twenty tons of atmosphere rest on the average adult. If something floats, it's supposed to be lighter than a feather. Do you grow tired at the end of the day? I have an excuse for you.

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