nitrogen
the most abundant gas in the earth's atmosphere (~78%)
oxygen
the second-most abundant gas in the earth's atmosphere (~21%)
atmosphere
the envelope of gases that surrounds Earth
ozone
a form of oxygen that has three oxygen atoms in each molecule instead of the usual two
water vapor
water that is in the form of a gas
weather
the condition of Earth's atmosphere at a particular time and place
density
the amount of mass in a given volume of air
force pushing on an area or surface
pressure
the result of the weight of a column of air pushing down on an area
air pressure
barometer
any instrument that measures air pressure
mercury barometer
instrument that measures air pressure using liquid mercury
the distance above sea level
altitude
aneroid barometer
instrument that measures air pressure without using a liquid
troposphere
the layer of the earth's atmosphere where weather occurs
mesosphere
the layer of the atmosphere where most meteoroids burn up
stratosphere
the layer of the atmosphere that contains ozone
ionosphere
the layer of the atmosphere where auroras appear and from which radio wave bounce off
thermosphere
atmosphere layer that is divided into the ionosphere and exosphere
exosphere
the outer portion of the thermosphere that extends from about 400 kilometers outward for thousands of kilometers
auroras
brilliant light displays caused by particles from the that enter the ionosphere near the poles