Earth's atmosphere

Earth's atmosphere is the layer of gases surrounding the planet Earth and retained by the Earth's gravity. It contains roughly 78% nitrogen and 21% oxygen, with trace amounts of other gases. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation and reducing temperature extremes between day and night.

Related Topics:
Earth - Nitrogen - Oxygen - Ultraviolet - Radiation - Day - Night

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The atmosphere has no abrupt cut-off. It slowly becomes thinner and fades away into space. There is no definite boundary between the atmosphere and outer space. Three-quarters of the atmosphere's mass is within 11 km of the planetary surface. In the United States, persons who travel above an altitude of 50.0 miles (80.5 km) are designated as astronauts. An altitude of 120 km (75 mi or 400,000 ft) marks the boundary where atmospheric effects become noticeable during re-entry. The Karman line, at 100 km (62 mi), is also frequently used as the boundary between atmosphere and space.

Related Topics:
Outer space - Planetary - Astronauts - Karman line

~ ~ ~ ~ ~ ~ ~ ~ ~ ~