for National Geographic News
People have reported seeing ball lightninga rare phenomenon that resembles a glowing sphere of electricityfor hundreds of years.
But scientists still can't explain what causes it, or even exactly what it is.
"There's certainly no consensus. I don't think that anyone knows what it is," said Graham K. Hubler, a physicist at the U.S. Naval Research Laboratory in Washington, D.C.
"Most scientists feel that the proper model hasn't been found yet."
Surveys estimate that between 1 in 30 and 1 in 150 people believe that they have seen ball lightning. Hubler is one of them.
His close encounter happened at age 16, while he was riding out a thunderstorm in an open-sided park pavilion.
"It's extraordinaryyou're so startled that you remember it for the rest of your life," he said.
He describes seeing a glowing, tennis ball-size formation hovering nearby.
"It drifted along a few feet above the ground," Hubler recalled, "but when it came inside [the pavilion] it dropped down to the ground and skittered along the floor."
"It made lots of gyrations or oscillations and a hissing sound like boiling water. When it went out the other side [of the pavilion], it climbed back up [several feet off the ground]."
Hubler says the ball behaved as if it had a charge and was following electric field lines along the Earth.
"I remember telling people what I had seen, and they thought I was crazy, so I stopped talking about it," he said.
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