Predicting Weather By The Moon - Xavier University Libraries

Weather By The Moon
was the size of a medicine ball, the atmosphere would be
only 1 millimetre more in diameter. Moreover, on that scale
the amount of water in the seas would be only a tablespoonfull,
tipped onto the medicine ball. This seems surprising;
if the seas covered the earth uniformly, they would only
average one kilometre deep.
Just as the seas are free to move, so is the atmosphere,
which is less dense and able to move quicker. Water
is 800 times heavier than air. We have no trouble accepting
that the moon moves the seas. Moving the air is easier and
move it does, constantly.
The atmosphere is invisible to us. We don’t see it,
anymore than a fish sees water. Everything we sense is due
its presence, for smells are carried on the wind, sounds are
really air compressions, feelings on our skin surface are
partly due to temperature changes, and visible colors are
affected by the air which diffuses light.
The atmosphere is heated by the Sun when the Sun
heats the Tropics, which is that imaginary line around the
Earth at some 23° north of the line of the equator - Tropic
of Cancer (the Northern Tropic) and the Tropic of Capricorn
(the Southern Tropic) 23° south of the equator. ‘Tropic’
means to turn. The Tropics were the names given to the
apparent limits of the northern and southern passages of
the Sun. To peoples long ago they were the solstice point
at which the Sun ‘turned back’ toward the Earth, as viewed
from the ground. We still call this band the tropics - virtually
the area of the Earth containing all places between
imaginary latitude lines running through Sahara, Calcutta/
Mexico - and Johannesburg, Brisbane and Rio de Janeiro.
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