Aerial view of the world's largest particle accelerator, located at the Fermi National Accelerator Laboratory in Batavia, Illinois. (Corbis- Bettmann)

Natural gas is a mixture of naturally-occurring methane (CH₄) with other hydrocarbons and inert gases. The 2.3 trillion cubic meters (Tcm) or 81 trillion cubic feet (Tcf) of gas marketed and consumed globally in 1997 accounted for about 24 percent of the world's primary energy, ranking third among fuels after petroleum liquids (40%) and coal (25%).

The modern natural-gas industry has its origins in the nineteenth century as urban "gas works" that distributed synthesis gas (a mixture of carbon monoxide, hydrogen and carbon dioxide made by the incomplete combustion of coal, oil, or organic wastes in the presence of steam). Gas works illuminated London streets even before 1800, and subsequently provided lighting, cooking, water- and space-heating for homes, businesses and public buildings. By the late nineteenth century, gas light...