Ball Lightning Experiments Produce UFOs
[TNT headline: All fired up] The last place most people would try to start a fire is inside a tornado. But two researchers who have pulled off a similar trick in a lab in New Zealand say their experiment may explain enigmatic weather phenomena such as ball lightning. At first glance, tornadoes don't appear fire-friendly. Even at the calm centre of the whirlwind, there is enough of an updraft to make any flame tenuous, and the fast winds at its edge would blow out any blaze. Yet fireballs have been reported in some tornadoes, such as the twister that struck Dorset in Britain in 1989. Vortices have also been associated with floating spheres of ball lightning, which sometimes disappear with a loud explosion, suggesting they, too, contain combustible material. So John Abrahamson, a chemical engineer at Canterbury University in Christ- church, was intrigued when his former student Peter Coleman proposed trying to create a fireball in a mini tornado. They reckoned one might form in the vortex breakdown region, where air moves relatively slowly. "If it was coloured, you'd see this doughnut of air," says Abrahamson. Intriguingly, the vortex breakdown region is used in "vortex burners", in which a flame burns in a closed, horizontal cylinder. A horizontal vortex mixes and contains hot gases so that the fuel burns efficiently. But it was unclear if the combustion would be stable in a free-standing, vertical vortex. | |
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