s that the atmosphere must fill itself with water vapor again.
It's a continuous performance, and the water which is being evaporated
into the air falls to the earth, sooner or later, as rain, hail, or
snow."

"If it's all so regular," said Anton thoughtfully, "I don't see why we
don't get the same amount of rain every day, or at least every season."

"It isn't regular at all," the Weather Forecaster explained. "If
climatic conditions were regular, we could forecast the weather several
years in advance, instead of only a few days. There are a thousand
complicating factors. Land and sea are irregularly divided, and as there
is more evaporation from the sea than the land, every little curve in a
coast line means a disturbance of regularity. Then, Anton, remember,
while the earth is almost a globe it is not perfectly round, so that
every variation from the regular curve disturbs the air currents.
Moreover, the motions of the earth are very complicated. Sometimes it is
nearer the sun than at other times. It wobbles slightly on its axis. It
is inclined to the plane of the ecliptic, causing the seasons, and that
brings a new set of factors into the problem. A mountain range or a
desert will modify the atmosphere, even the difference between a forest
and a prairie is noticeable."

"Suppose you could figure all those things out, couldn't you foretell
the weather, then?"

The Forecaster shook his head.

"Suppose you had a thousand marbles of different colors," he said, "and
you dropped them from the top of a house to the hard ground below, a
rough and rocky piece of ground, could you ever figure out what kind of
a pattern they would make? You might measure the size of the marbles and
compute how many times they would strike against each other in falling,
meantime figuring the angles of direction that each collision would
produce. You might measure the resistance of the ground and the
elasticity of the marbles and estimate the manner in which they would
bounce after striking the ground and the distance to which they would
roll. After you had done all that, you might have the right to expect
that you would know the pattern that the marbles would make as they lay
scattered on the ground. But you would be wrong, for if you dropped
those marbles a thousand, yes, a million times, the pattern would be
different each time. After tens of billions of experiments you might be
able to find the proportion of patterns, but the result wou