Like we measure heat with a thermometer.

Question

Now, the bottom layer is the ,
It contains 90% of the air.

Answer 1

The bottom layer of the Earth's atmosphere, which contains about 90% of the air, is called the troposphere. This layer extends from the Earth's surface up to about 8 to 15 kilometers (5 to 9 miles) in altitude, varying with latitude and weather conditions. It is where most weather phenomena occur and where we live.