Our Whispy Thin Air

Candice eetimesWe live on a planet with almost no atmosphere to speak of.  Oh, I know it is a lot more than the Moon or Mars.  But compared to Venus, we live on the edge of space.  But most of us take what we have and think it is really thick.  We think of “space” as being ‘way up there’.  But it isn’t.

Our atmosphere is held down near the Earth’s surface by gravity.  The air pressure we depend upon is caused by the weight of the air above us.  But how thick is the atmosphere?  How much is really above us?  Far less than most realize.

Because the density of the air is related to how much air is above, the density changes with altitude because there is less air above as we go higher.  That means that most of the air is compressed at the very bottom, at low altitude.  How low?  Well, if one climbs a mountain that is 2000m (6,000ft), one is already above 20% of the atmosphere.  Climb Mount Everest, the tallest mountain on Earth at 8,500m (29,000ft) you can look down at 55% of the atmosphere, over half-way to space.

To get a feel for how thin this really is, visualize the Earth which is 6,371km radius on average.  Now visualize a radius only 20km larger, where 95% of the atmosphere lies below… if you drew a circle six inches in diameter with a compass the atmosphere is the thickness of the pencil line!

Let’s shift gears a moment and visualize the amount of atmosphere.  If one were to compress all of the air and convert it to a liquid it would be only a bit over 3m (16ft) deep.  That liquid would be about the same density as dirt or aluminum.  That’s it, 3m of radiation shielding between you and the vacuum of space.

Now, realizing how very little atmosphere there really is… one has a new appreciation for how little pollution it can absorb, including all of that O2 we are converted to CO2 greenhouse gas.  But that’s a topic for a future essay.

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