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
Shale gas in the United States natural gas expenditures by as much as 11.6 billion by 2025. America's Natural Gas Association (ANGA) estimates that lower gas prices will add an additional $926 of disposable household income annually between 2012 and 2015, and that the amount could increase to $2,000 by 2035. Over a 100 billion dollars is going to be invested in the US Petrochemical industry and most of it in Texas. Due to emergence of shale gas, coal consumption declined from 2009. One study finds that hyraulic fracturing has contributed to job growth and higher wages. The results of the study "suggest new oil and