Readers Digest Australia Sampler 2022

PHOTO: COURTESY BLACHFORD LAKE LODGE & WILDERNESS RESORT. *SOURCE: WWW.NRC.GOV/DOCS/ML1209/ML120960701.PDF Blachford Lake Lodge is best reached by bush plane the lodge. One night, Elizabeth Mac- Donald, a visiting space scientist from NASA, gave a lecture on the aurora’s physics. She told us how glad she was to be here; she spends most of her time on data. “I study the aurora,” she said, “but I don’t get to see it that of- ten.” We see the aurora because elec- trons charged by the solar wind collide with atoms in the upper at- mosphere, mostly atomic oxygen. A fountain of resulting photons spills across hundreds of kilometres in seconds. Atomic oxygen releases red light when high in the atmosphere and can emit greenish-white light at lower altitudes. Sometimes deep blues and purples appear from ion- ised nitrogen. A furious discharge cascades down through the atmos- phere into increasingly dense air until it is exhausted. The power of the aurora can be as high as 100,000 megawatts – enough to power 40-90 million houses*. FOR EONS, people have said the aurora makes noise, that it swishes, whistles, cracks. One polar explorer described it as “the sound of field- ice, then it was like the sound of a water-mill and, at last, like the whir- ring of a cannon-shot heard from a short distance.” It has been long thought, however, that whatever au- dible sound reaches a human ear at ground level could not be an effect of activity at such a high altitude. But in 2012, Finnish scientists captured faint hissing, popping and clapping during an aurora, and proved the sounds were coming from the sky. A geophysicist in Alaska reacted to the readersdigest.com.au 9 Chasing The Northern Lights