outside and look up. What do you see? You might see blue sky or wooly
clouds. At night you might see stars, a satellite or a crescent moon.
What you are not seeing, however, is the complexity of our atmosphere.
The atmosphere is a protective layer of gasses that shelters all life
on Earth, keeping temperatures within a relatively small range and
blocking out harmful rays of sunlight.
The atmosphere has five different layers that are determined by the
changes in temperature that happen with increasing altitude.
Living at the surface of the Earth, we are usually only aware of
the events happening in the lowest layer, the troposphere, where
occurs. The base of this layer is warmer than its top because the
air is heated by the surface of the Earth, which absorbs the
Above the troposphere lies the stratosphere where jet airplanes fly.
Temperatures increase with altitude because of increasing amounts of
ozone. The ozone layer within the stratosphere absorbs harmful ultraviolet
rays of sunlight.
As the mesosphere extends upward above the stratosphere, temperatures
decrease. The coldest parts of our atmosphere are located in
this layer and can reach –90°C.
In the forth layer from Earth’s surface, the thermosphere, the
air is thin, meaning that there are far fewer air molecules. The thermosphere
is very sensitive to solar activity and can heat up to 1,500°C
or higher when the Sun is active making an aurora that lights
up the night
sky. Astronauts orbiting Earth in the space station or space
shuttle spend their time in this layer.
The upper layer of our atmosphere, where atoms and molecules escape
into space, is called the exosphere.
Windows to the Universe Earth Atmosphere section
showing what phenomena can be found in the different layers of the atmosphere