Imagine you are taking a ride in a hot air balloon. The balloon rises gently from the ground,
then catches a breeze. As you float along, you see fields and forests, roads and towns.
You rise higher and higher until you can see clouds below you and the air gets a bit chillier.
How high are you?
Hot air balloons typically travel between one thousand and three thousand feet above the ground, less than a mile.
Your hot air balloon will do all of its traveling in the layer of the Earth's atmosphere called the troposphere.
The troposphere contains about 80 percent of the mass of the atmosphere. Because it holds almost
all of the Earth's water vapor, this layer is also where most weather happens. The air in
the troposphere is warmed by the Earth's surface and is in constant motion. As the warm air rises,
cooler air flows down to take its place. These air currents create wind and promote cloud formation.
As you look around in your hot air balloon, you see a huge cloud off to the west.
It rises high into the air and then flattens at the top into a shape like an anvil. Where
it flattens is where the cloud reaches the next layer of the atmosphere called the stratosphere.
You'll hear a roaring noise and look out to see a commercial jet high above you.
These jets fly in the upper reaches of the troposphere and sometimes into the stratosphere
where they can stay above most air turbulence and storms, and where the thin air offers little
resistance to the plane's movement. Incredibly, there is a bird called the Ruppell's griffin
vulture that can fly into the stratosphere at the same height as a commercial airplane.
There is only one place on Earth where land touches this layer of the atmosphere.
If you were to climb to the top of Mount Everest, you would reach the stratosphere.
The amount of gases in the atmosphere decreases the higher you go which
is why people who climb Mount Everest choose to bring extra oxygen with them.
An important layer of the atmosphere lies within the stratosphere. The ozone layer
is a layer of gases that absorbs harmful ultraviolet rays from the Sun before they
can reach the surface of the Earth and cause harm to the humans and creatures living here.
If you brought a helium balloon with you on your hot air balloon ride and let it go,
would it reach the stratosphere? It might make it there but not much further. It would most likely
burst at around 32,000 feet from expanding and contracting to equalize the pressure outside the
balloon with the pressure inside the balloon. On the other hand, special weather balloons regularly
enter the stratosphere where they measure wind speed, temperature, air pressure, and humidity.
Weather balloons help scientists learn about the atmosphere and more accurately predict the
weather. The Sun is setting as your balloon ride ends and it is almost dark when you touch down.
Looking up, you see a shooting star streak across the sky. That meteor is burning up
in the mesosphere, the third layer of the Earth's atmosphere. Scientists know very little about the
mesosphere, but they do know that it contains less than 0.1 percent of the atmosphere's air mass.
If you were taking your balloon ride somewhere far to the North like Alaska or Norway, you might
see the Northern Lights or Aurora Borealis once it gets dark. This beautiful display of dancing
colors is caused by charged particles from space colliding with the fourth layer of the atmosphere
called the thermosphere. This layer is also the hottest layer, where temperatures can reach as
high as 4500 degrees Fahrenheit. The final layer of the Earth's atmosphere is the exosphere.
The International Space Station orbits in the thermosphere, but other satellites orbit farther
out into the exosphere. This atmospheric layer is almost empty of gas molecules and it is the
transition layer between the Earth's atmosphere and empty space. Our atmosphere protects us from
the sun's rays and other radiations, such as cosmic rays, and provides us air to breathe,
as well as giving us a source of incredible beauty and wonder. Although the atmosphere is colorless,
the phrase clear blue sky perfectly describes the beauty and wonder of Earth's atmosphere
as it looks to us on a pretty day. Next time you look up at a fluffy white cloud,
think about the protection and life-giving air we receive from our amazing atmosphere.