Atmosphere of Earth the border between the atmosphere and outer space. Atmospheric effects become noticeable during atmospheric reentry of spacecraft at an altitude of around . Several layers can be distinguished in the atmosphere, based on characteristics such as temperature and composition. The study of Earth's atmosphere and its processes is called atmospheric science (aerology). Early pioneers in the field include Léon Teisserenc de Bort and Richard Assmann. The three major constituents of Earth's atmosphere are nitrogen, oxygen, and argon. Water vapor accounts for roughly 0.25% of the atmosphere by mass. The concentration of water vapor (a greenhouse gas) varies significantly from around
Natural gas in the United States price of natural gas has been relatively cheap on the North American market, especially compared to oil. Electricity from oil-powered generators in the US declined 81 percent from 2005 to 2014. The states which use the most natural gas for electricity production are, in descending order, Texas, Florida, California, and New York. Liquefied petroleum gas includes the butane and propane natural gas liquids removed in gas processing. They are sold for home heating, cooking, and increasingly for motor fuel. The industry segment is represented by the National Propane Gas Association. Natural gas, in the forms of compressed natural gas, liquified