Question: what are the four main layers of the atmosphere?
Answer: Troposphere. The troposphere starts at the Earth's surface and extends 8 to 14.5 kilometers high (5 to 9 miles). ... 
Stratosphere. The stratosphere starts just above the troposphere and extends to 50 kilometers (31 miles) high. ... 
Mesosphere. ... 
Thermosphere. ... 
Ionosphere. ... 
Exosphere. ... 
Credit: NASA/Goddard.