Answer to Question 1
Temperature is defined in terms of the average speed at which molecules move. Because the gases of the thermosphere are moving at very high speeds, the temperature is very high. But the gases are so sparse that, collectively, they possess only an insignificant quantity of heat, whereas the gases near Earth's surface are far more concentrated.
Answer to Question 2
The lowermost layer is the troposphere. Here, temperature decreases with an increase in altitude. This is the layer where essentially all important weather phenomena occur. The next layer is the stratosphere. In this layer, the temperature remains constant to a height of about 20 kilometers and then begins an increase that continues until the stratopause, at a height of about 50 kilometers. The ozone layer is concentrated in this layer. The third layer is the mesosphere, where temperatures again decrease with height. The fourth layer is the thermosphere, which has no well-defined upper limit. It contains only a tiny fraction of the atmosphere's mass. In this layer, temperatures increase due to the absorption of shortwave high-energy solar radiation by atoms of oxygen and nitrogen.
