Want to stay on top of all the space news? Follow @universetoday on TwitterLately, the atmosphere has been one of those entities cast into the limelight as a result of Al Gore’s well-circulated documentary film about global warming, entitled ‘An Inconvenient Truth’. In the movie, Gore described the atmosphere by showing a huge globe and pointing out that the atmosphere was like a coat of varnish on it. But global warming aside, what is the atmosphere, really?
The atmosphere is the body of gas that surrounds a planet. If we talk about the Earth’s atmosphere composition alone, we can describe it in terms of structure as being made up of five principal layers: the Troposphere, Stratosphere, Mesosphere, Thermosphere, and Exosphere.
The Troposphere, which is the lowest, i.e, from the ground surface up to roughly 7 km above it (at the poles) or 17 km above it (at the equator), is also the warmest. This is because it is in direct contact with the Earth’s surface. In case you’re not aware, solid materials (like the ground) heat up fastest and this heat is transfered to the adjacent Troposphere.
Right above the first layer is the 50 km-high Stratosphere. This is followed by the 85 km-high Mesosphere, the layer where most meteors ignite on their way to the surface below. Thus, when we see shooting stars, we’re looking at them as they pass through the Mesosphere.
As we ascend even higher, we enter the realm of the 690 km-high Thermosphere. This is where the International Space Station orbits. It is then followed by the topmost layer, the Exosphere. The highest point of the Exosphere is about 10,000 km from the ground.
All measurements of distance mentioned above can change due to variations in atmospheric pressure in any of the layers.
As one moves to higher altitudes, the atmospheric pressure decreases. Thus, the Troposphere has the highest pressure while the Exosphere has the lowest. Pressures are so low at high altitudes that they can have harmful effects on the human body. That is why pilots flying aircraft at these altitudes wear pressurized suits.
When Joseph William Kittinger II ascended for his record-setting dive, his right glove malfunctioned. As a result, his right hand swelled to twice its normal size. Breathing is also difficult, if not impossible, at the topmost atmospheric layers because of low pressure.
When somebody asks you the question, “What is atmosphere?” you should first determine which ‘atmosphere’ the person asking is referring to. It can also mean the main unit used to denote atmospheric pressure, you know. For example, the atmospheric pressure at sea level is 1 atmosphere or 1 atm.
Universe Today has some articles that can tell you more about the atmosphere. Here are the links:
NASA also has some more:
Here are two episodes at Astronomy Cast that you might want to check out as well: