geography assignment.. The atmosphere is the source of life
Answers
Explanation:
The atmosphere is thin and light, a gas that is only bound to the solid mass of the Earth by gravity. The mass of the atmosphere is about 250 times less than that of the oceans and accounts for less than one millionth of the total mass of the planet. The atmospheric pressure and density of air decrease exponentially with height above the surface. The term ‘exponentially’ means that for every increase in height by the same distance, the atmospheric density falls by the same factor. In the case of the Earth, density halves for every increase of around 5.9 km in altitude. At the top of Mount Everest (8.85 km above sea-level), about 70% of the atmosphere is already beneath your feet. Contrast this with the radius of the Earth itself, around 6,371 km. The atmosphere is really a very thin skin.
Continue
Skip to content
The Open University
Author: Stephen Lewis
How the atmosphere sustains life on Earth
Updated Monday, 2nd November 2020
Why does the Earth’s atmosphere make it the perfect home for life? Professor Stephen Lewis explores...
Earth is a vibrant blue planet, the only place that we can be sure that life exists. As A Perfect Planet shows, a complex and interconnected set of systems operate to form our environment. Every planet except one in the Solar System has a gaseous atmosphere, as do some moons and even some dwarf planets. Why does the Earth’s atmosphere make it so perfect as a home for life?
The Earth’s atmosphere
The atmosphere is thin and light, a gas that is only bound to the solid mass of the Earth by gravity. The mass of the atmosphere is about 250 times less than that of the oceans and accounts for less than one millionth of the total mass of the planet. The atmospheric pressure and density of air decrease exponentially with height above the surface. The term ‘exponentially’ means that for every increase in height by the same distance, the atmospheric density falls by the same factor. In the case of the Earth, density halves for every increase of around 5.9 km in altitude. At the top of Mount Everest (8.85 km above sea-level), about 70% of the atmosphere is already beneath your feet. Contrast this with the radius of the Earth itself, around 6,371 km. The atmosphere is really a very thin skin.
Sunset looking through the Earth’s atmosphere from the International Space Station
Sunset looking through the Earth%u2019s atmosphere from the International Space Station.
The image above was taken by an astronaut on the International Space Station as the Sun sets behind the outer edge of the Earth. Astronauts aboard the International Space Station experience sixteen sunsets and sunrises per day as it orbits Earth! The lowest layer of the atmosphere is mostly illuminated red and is cloudy in this image. This is the troposphere, where the atmosphere churns as it carries heat upwards by convection from the surface, like water in a saucepan when heated from below. The troposphere is where nearly all of our familiar weather happens. Long-distance passenger aircraft fly in the upper troposphere. The troposphere extends to about 10–20 km from the surface; it is up to 20 km deep near the equator, where the atmosphere is convecting strongly, and can be as little as half that at the poles. Within the troposphere the temperature falls by about 6°C for every kilometre of altitude gained, so by the top of the troposphere the temperature can fall well below -80°C and the pressure and density are only a tenth of those at the surface. These conditions require a pressurised and heated cabin or a space suit.
The atmosphere above the troposphere is called the stratosphere and appears a clear, blue colour in the image. In the stratosphere the temperature begins to rise again with increasing height. In contrast to the troposphere, the stratosphere is very stable, or stratified, as implied by the name. Although 90% of the mass of the atmosphere is below in the troposphere, the stratosphere still makes a vital contribution to the environment beneath. Only a few aircraft and research balloons are built to be able to fly in the stratosphere in the thin air. Most of the sky would already be dark, rather than blue, for a passenger in such an aircraft. The top of the stratosphere lies at about 50 km altitude. Although there are more rarefied atmospheric layers above, for practical purposes the environment is already much more like ‘space’ by this point. By convention ‘space’ is said to start at an altitude of 100 km, although this is a rather arbitrary round number and there is no ‘top’ to the atmosphere as such, rather atoms and molecules simply become increasingly rare, but a very few reach out even beyond the Moon’s orbit and are lost to Earth.
Atmosphere: An atmosphere is a blanket of gases that surrounds Earth. It is held near the surface of the planet by Earth’s gravitational attraction. Argon, oxygen and nitrogen from the three main constitutions of the atmosphere.
Atmosphere as the source of life : The atmosphere is the source of life for the following reasons:
a. Oxygen, which is essential for the survival of all living organisms, is present in the atmosphere.
b. Essential gases that support life on the earth are present in the atmosphere.
c. Water cycle would not have been possible without the atmosphere.
d. The atmosphere acts as a protective blanket for the earth by blocking the harmful UV rays from the sun.
e. The temperature on the earth is maintained because of the presence of the atmosphere.
So, we call " The atmosphere is the source of life"