Atmosphere

What is the
Atmosphere?

The atmosphere is the air that
surrounds earth. It is made of a
mixture of gases that protect
Earth and help create conditions
that allow life to live here.

Scientists describe the
atmosphere in terms of five
layers, each with distinct
characteristics.The atmosphere
is thickest near the surface of
Earth. It thins out gradually until
it eventually merges with space.

Troposhpere

The troposphere is the layer
closest to Earth. It extends
higher at the equator, where
the weather is warmer than it
is at Earth's poles. It is about
18 km high at the equator
and only 8 km high at the
poles. All weather takes
place in this layer, including
clouds, rain, snow, ice, and
winds.

Stratosphere

The stratosphere is the next
layer of the atmosphere. It's
about 40 km thick, which is more
than twice the size of the thickest
part of the troposphere. The
stratosphere contains ozone--a
special form of oxygen that
protects Earth from receiving too
much ultraviolet (UV) radiation
from the sun. All living things
need small amounts of UV
radiation, but not too much.

Mesosphere

The mesosphere begins
just above the stratosphere
and extends 85 km above
Earth. This is the coldest
layer of the atmosphere.
It's also the layer in which
most meteors dissolve.

Thermosphere

Above the mesosphere is
the thermosphere, which
reaches to about 600 km
above the planet's
surface. The air in this
part of the atmosphere is
very thin, but the layer
itself is much wider and
hotter than the others.

Exosphere

The fifth and thinnest
layer, the
exosphere, is the
atmosphere's upper
limit. Here, the
atmosphere merges
into space.

What makes our sky
blue?

As waves of sunlight pass through
Earth’s atmosphere, gases and
particles scatter the waves. If
you’ve ever seen a rainbow, you've
seen all of the colors that exist in
sunlight.

Of all the waves in sunlight, blue
light travels in the shortest, smallest
waves. As a result, blue is scattered
more than the other colors. That’s
why we think of the sky as blue!