DECEMBER 2021 • 89visiting 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 often.”
We see the aurora because
electrons charged by the solar wind
collide with atoms in the upper
atmosphere, mostly atomic oxygen.
A fountain of resulting photons
spills across hundreds of miles 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
ionised nitrogen. A furious discharge
cascades down through the
atmosphere into increasingly dense
air until it is exhausted. The power
of the aurora can be as high as
100,000 megawatts.For aeons, 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
whirring of a cannon-shot heard
from a short distance.” It has been
long thought, however, that whatever
audible 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
news by saying that auroral sound
was “scientifically unreasonable,” but
admitted that he has heard it, too.
To Indigenous communities,
the northern lights are familiar but
worthy of respect. Many Inuit people
in the Arctic share a myth of theREADER’S DIGESTph
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