Our atmosphere is a delicate, life-giving blanket of air that surrounds the fragile Earth.
In
one way or another, it influences everything we see and hear—it is intimately connected to our
lives. Air is with us from birth, and we cannot detach ourselves from its presence. In the open
air, we can travel for many thousands of kilometers in any horizontal direction, but should we
move a mere 8 kilometers above the surface, we would suffocate. We may be able to survive
without food for a few weeks, or without water for a few days, but, without our atmosphere,
we would not survive more than a few minutes. Just as fish are confined to an environment of
water, so we are confined to an ocean of air. Anywhere we go, air must go with us.
Earth without an atmosphere would have no lakes or oceans. There would be no sounds, no
clouds, no red sunsets. The beautiful pageantry of the sky would be absent. It would be
unimaginably cold at night and unbearably hot during the day. All things on Earth would be at
the mercy of an intense sun beating down upon a planet utterly parched.
Living on the surface of Earth, we have adapted so completely to our environment of air that
we sometimes forget how truly remarkable this substance is. Even though air is tasteless,
odorless, and (most of the time) invisible, it protects us from the scorching rays of the sun and
provides us with a mixture of gases that allows life to flourish. Because we cannot see, smell, or
taste air, it may seem surprising that between your eyes and these words are trillions of air
molecules. Some of these may have been in a cloud only yesterday, or over another continent
last week, or perhaps part of the life-giving breath of a person who lived hundreds of years ago.
In this chapter, we will examine a number of important concepts and ideas about Earth’s
atmosphere, many of which will be expanded in subsequent chapters. These concepts and ideas
are part of the foundation for understanding the atmosphere and how it produces weather.
They are built on knowledge acquired and applied through the scientific method. This technique
allows us to make informed predictions about how the natural world will behave.
1.1 The Atmosphere and the scientific Method
For hundreds of years, the scientific method has served as the backbone for advances in
medicine, biology, engineering, and many other fields. In the field of atmospheric science, the
scientific method has paved the way for the production of weather forecasts that have steadily
improved over time.
Investigators use the scientific method by posing a question, putting forth a hypothesis*,
predicting what the hypothesis would imply if it were true, and carrying out tests to see if the
prediction is accurate. Many common sayings about the weather, such as “red sky at morning,
sailor take warning; red sky at night, sailor’s delight,” are rooted in careful observation, and
there are grains of truth in some of them. However, they are not considered to be products of
the scientific method because they are not tested and verified in a standard, rigorous way.
