The following excerpt is from the August issue of National Geographic magazine.
Late summer is thunderstorm season in this part of the country, [the Oklahoma Panhandle] and since 2006 [Tim] Samaras has been trying to do the impossible: capture an image of a lightning strike the moment it is born. The process typically begins when a descending zigzag of negatively charged electricity—a stepped leader—feels its way from cloud to ground. When it gets near enough, positive fingers of charge reach up from the earth. The instant the two come together, a dazzling surge of current—some 30,000 amps traveling at a third of the speed of light—leaps toward the sky. The burst of light from this "return stroke" is what you see with the naked eye, which often interprets the motion as downward. From beginning to end, the entire process takes as little as 200 milliseconds.
In Samaras’s trailer there are two Phantoms, high-speed cameras capable of shooting 10,000 frames per second. They have allowed him to capture stunning slow-motion videos detailing the paths of downward stepped leaders and occasionally the upward streamers. But as soon as the two connect—initiating an event called the attachment process—the flash from the return stroke blinds the camera, obliterating the details. Scientists would love to peek behind the curtain and watch the event as it unfolds, with the return stroke lifting off like a rocket from the ground.
Lying within the imagery might be clues to some of lightning’s biggest mysteries. Why will a lightning bolt sometimes strike a low tree when right beside it is a tall metal tower? And why, for that matter, does lightning strike at all? For all their intensity, the voltages produced in thunderclouds are not nearly strong enough to overcome the insulating properties of air. Some extra factor is required, and a picture of the attachment process might suggest an answer. Opening this frontier calls for a custom-outfitted camera capable of shooting more than a million high-resolution frames per second. There’s just one camera like that, and it too is in Samaras’s trailer.
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The images provided are from the August edition of National Geographic magazine.