|MLA Citation:||Bloomfield, Louis A. "Question 1045"|
How Everything Works 20 Jan 2018. 20 Jan 2018 <http://howeverythingworks.org/print1.php?QNum=1045>.
This dynamic balance of growth and shrinkage occurs right in the middle of the air all the time. Tiny water droplets form by accident, even in reasonably dry air, but in most cases they quickly shrink back to nothing because the leaving rate is higher than the returning rate. However, when air that contains lots of moisture experiences a decrease in temperature, the returning rate can exceed the leaving rate. When that happens, the tiny droplets that appear by accident don't immediately disappear. Instead, they grow larger and larger. Depending on the altitude, we call the white mist that results clouds or fog.