The Earth’s Atmosphere
The Earth's atmosphere is a mixture of nitrogen (78%), oxygen (21%) and
other gases (1%) that surround the Earth. As you travel higher and higher, the
atmosphere becomes thinner until it gradually reaches space. It is divided
into five layers – the troposphere, the stratosphere, the mesosphere, the
thermosphere and the exosphere, and each layer is very different.
This Space Shuttle ‘Endeavour’ appears to
be crossing through the stratosphere and
mesosphere, although in truth it is orbiting at
more than 200 miles from the Earth’s surface,
way above this transition layer. The troposphere,
the orange layer, is closest to Earth, where all
of the weather we experience is generated and
contained. The white stratosphere follows this,
and then out into the Mesosphere.
The Troposphere
The Thermosphere
This is where our weather forms and it contains about 75%
of the Earth's atmosphere. It is up to 10 miles above Earth –
extending up from Earth's surface by 5 miles over the North
and South Poles, and it is up to 10 miles up at the Equator.
It gets extremely cold near the top, reaching temperatures
as low as -75°C! This layer alone makes up the 'Lower
Atmosphere'.
The first layer contributing to
the 'Upper Atmosphere' is the
Thermosphere. This ranges
between 50 to 400 miles above
the Earth's surface. The air is thin
here, but it absorbs so much
solar radiation that it can get
extremely hot – up to 230°C!
Within this thermosphere there
is the magnetosphere, which
contains charged particles
affected by the Earth's magnetic
field, where the Northern and
Southern Lights are created
under the right conditions. It also
contains the ionosphere, where
electrically charged particles
interfere with radio broadcasts.
The S