SPHERES

Last week I wrote about our atmosphere.  How it is made up mostly of nitrogen and oxygen and how there is less and less the further you get away from Earth.  This week we'll delve a little deeper into the subject. 

Our atmosphere is actually divided up into several layers.  The first is called the troposphere.  It extends from the surface of the Earth to about 4 miles at the poles and 10 miles at the equator.  This is the layer we live in - the troposphere.  When you fly in a large airplane, this is the layer you usually glide in.

The troposphere ends at the stratosphere.  The stratosphere contains our ozone layer which protects us from the harmful rays of the sun.  This layer goes up to about 30 miles above the Earth.  This level is reserved for spy planes and the like.

Next comes the mesosphere.  It extends to about 50 miles above the Earth.  Most meteors (shooting stars) burn up in this level.  

After the mesosphere comes the thermosphere.  It starts at about the 50 mile mark and reaches 250 miles high.  At about 60 miles up, we consider the thermosphere to be outer space. 

Inside the thermosphere is an interesting sub level called the ionosphere.  The ionosphere moves up and down and thickens depending on whether the sun hits it.  This is the level that reflects am radio waves and explains why you can receive far-away stations at night but not during the day.

Above the thermosphere is the exosphere which indicates it is not part of our atmosphere.   It starts about 400 to 600 miles above Earth.  Somewhere up there, the exosphere runs into the magnetosphere.  This layer gets it's name because it is the boundary where Earth magnetic field has some effect on objects.

Okay, if you have continued to read this whole article, raise your right hand; now put it behind your head; now pat yourself on the back.  You deserve a medal.

ps  I don't care how many billion planets there are - finding another just like this is beyond my imagining.  I don't buy aliens on distant planets.