Science glossary film: Atmosphere Glossary video

A layer of gas surrounding a planet or star, held in place by gravity. The Earth's atmosphere consists of roughly 78% nitrogen, almost 21% oxygen, and small proportions of other gases, such as argon and carbon dioxide. It gets thinner with increasing altitude, and while there is no strict boundary between the atmosphere and space, 100 kilometers is generally accepted as its upper limit.

The Earth's atmosphere consists of roughly 78% nitrogen, almost 21% oxygen, and small proportions of other gases, such as argon and carbon dioxide. It gets thinner with increasing altitude, and while there is no strict boundary between the atmosphere and space, 100 kilometers is generally accepted as its upper limit.