[San Francisco Chronicle] Scientists are eyeing the jet stream, an energy source that rages night and day, 365 days a year, just a few miles above our heads. If they can tap into its fierce winds, the world’s entire electrical needs could be met, they say. The trick is figuring out how to harness the energy and get it down to the ground cost-effectively and safely. Dozens of researchers in California and around the world believe huge kite-like wind-power generators could be the solution. As bizarre as that might seem, respected experts say the idea is sound enough to justify further investigation. The jet stream typically blows from west to east 6 to 9 miles over the northern hemisphere at speeds up to 310 mph. By lofting generators into the upper atmosphere, scientists theorize they could capture the power of the jet stream and transmit the electricity along cables back to Earth.