Reef robocop res­cue

Australian Geographic - - Contents - with Dr Karl Kruszel­nicki

THE MYSTERIOUS MIN MIN lights ap­pear af­ter dark, of course. Weirdly, when you ap­proach them, they al­ways re­treat. They were first noted near the now-aban­doned western Queens­land set­tle­ment of Min Min.

A typ­i­cal Min Min light is cir­cu­lar, about one-quar­ter the size of the full Moon and has fuzzy, mov­ing edges, like a buzzing bee swarm. Min Min lights are usu­ally white, but can be green, yel­low, red or rarely blue. The fuzzy orbs can dance around er­rat­i­cally left to right, up and down and back and forth. Oc­ca­sion­ally, a sin­gle Min Min light can sud­denly split into two sep­a­rate lights.

Aus­tralian poly­math and neu­ro­sci­en­tist Pro­fes­sor John Pet­ti­grew says he’s solved the mys­tery. In­deed, he was even able to cre­ate his own Min Min light.

He says they are real, but dis­tant, lights – a fire, or bright head­lights.

Nor­mally, you can’t see them, be­cause they’re over the hori­zon, and too faint. But Pro­fes­sor Pet­ti­grew has proved that a layer of cold air, sit­ting just above the ground, be­tween the dis­tant light and the ob­server, can trap light. This layer bends the light and keeps it close to the ground, so it can be seen over great dis­tances. This layer of cold air can also con­cen­trate the dis­tant light and stop it from spread­ing – so it doesn’t get weak­ened by ex­treme dis­tance.

John Pet­ti­grew used ge­om­e­try to show a Min Min light was ac­tu­ally very bright truck head­lights – 300km away! An­other time, he drove 10km away and shone his head­lights at the camp­site.

His com­pan­ions re­ported via ra­dio see­ing a bob­bing light just above the hori­zon, half the size of the full Moon, chang­ing from vivid red, to or­ange, yel­low then green. As Pet­ti­grew switched his head­lights on and off, the Min Min light dis­ap­peared and re­turned.

So these float­ing orbs aren’t com­bust­ing marsh gas, swarm­ing bi­o­lu­mi­nes­cent in­sects, or even aliens. But light trapped in cold air is spooky enough.

DR KARL is a pro­lific broad­caster, au­thor and Julius Sum­ner Miller fel­low in the School of Physics at the Univer­sity of Syd­ney. His lat­est book, Karl, the Uni­verse and Ev­ery­thing, is pub­lished by Pan Macmil­lan. Fol­low him on Twit­ter: @Doc­torKarl

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