There was an old lady called Wright
who could travel much faster than light.
She departed one day
in a relative way
and returned on the previous night.
I admit, that had nothing at all to do with the topic of this post. But it is sort of about light. And apparently it was Einstein’s favourite limerick. So it’s appropriate by default.
I read a rather fascinating article the other day on earthquake lights. What’s that, you ask? Exactly what it sounds like. I’ve heard of some weird earthquake science, but this is probably the most bizarre phenomenon I’ve encountered so far. Earthquake lights (EQL) are glows that appear in the sky before, after, or during earthquakes. Though they’ve been documented as far back as ancient Greece, it wasn’t until the mid-1960s that they were caught on camera and conclusively accepted into the realm of science. The colour, range, and duration of documented lights ranges widely, although they have commonly been reported as white or blue.
Photograph of the glow from Nagano, Japan (mid-1960s) (Photo: Earthquake Engineering Research Center, University of California, Berkeley)
Until recently, these phenomena have remained something of a scientific enigma. A new study, however, has finally proposed a plausible explanation for how these glows are produced. In the study, the authors looked at 65 documented events to try to determine a common denominator. What they found is that the majority of events were associated with earthquakes that occurred at faults or rift zones. Imagine two large slabs of rocky crust moving in opposite directions. Where they meet and slide against each other, pressure builds up and is released through earthquakes.
An aerial view of the San Andreas Fault
Faults are essentially large vertical or inclined ‘cracks’, often extending kilometers below the surface. These cracks can serve as conduits for charges to travel upwards from stress zones to the surface, where they interact with the atmosphere. As rocks deep below the surface are squeezed against each other, they are not only bent and fractured, but chemical bonds within them are broken on a molecular level. In the proper conditions, this can create ‘holes’ of electrical charge that travel upwards through the fault to the surface. In effect, the glow can be thought of as a weak form of lightning that comes not from the clouds but from beneath the ground.
This footage was recorded before the 2008 Sichuan, China earthquake and has since been verified as an EQL phenomenon
Be warned: you may have just sustained a lethal dose of mostly harmless science.
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Cover photo courtesy of Jesusisland, Flickr Creative Commons. Other images from Wikimedia Commons.
