The Lost Sock

Imagine that you've lost one sock in the week's laundry. How do you find it? Where do you look first - under 14 pounds of towels topped by your brother's football jersey? People who search for natural gas have a similar problem.

Fossil fuels like coal, oil, and natural gas are cleverly hidden under about a ka-zillion tons of rock, limestone, and shale. Special scientists like geologists, geochemists and subsurface specialists study the contours of the earth and look for certain signs that will clue them in to the underground presence of these fuels.

They gather clues that include photographs taken from airplanes, readings taken by scientists called seismologists who use explosives to send shock waves through the ground, and measurements taken by other scientists of the variations in the earth's density and magnetic fields.