The stratosphere is a layer of Earth's atmosphere. It is the second layer of the atmosphere as you go upward. The troposphere, the lowest layer, is right below the stratosphere. read more
The atmosphere becomes thinner as you go higher above the Earth's surface. About 50% of the mass of the atmosphere is located below an altitude of about 18,000 feet (5.6 km). About 90% of the atmosphere's mass is below an altitude of 52,000 feet (16 km). read more