There seems to be a fairly general acceptance of the idea that atmospheric pressure is caused by the weight of the molecules in the atmosphere.  This idea is supported even by Wikipedia.  I am not convinced that this is true.  I think that atmospheric pressure is caused by "air" molecules colliding with the Earth's surface.  This is not a new idea, of course, but it may not be widely held.  If true, however, surely the "air has weight" explanation should be put to rest, as in Wiki and other webs