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Remember last week’s noctilucent clouds? When I wrote about them June 14, I had only received a few photos of the rare optical phenomenon. Since then, my inbox has been filling up with photos from across the region. I’m a bit jealous as I have never seen them.
I look up all the time, but it has a lot to do with timing and luck. The day before the eerie clouds appeared, Michael Boschat was out looking for them. He had been in search of these glowing high-level clouds for 30 years Instead, he spotted beams of light in the western sky just after sunset.
Many of you have seen them, but I thought you might not be familiar with their lovely moniker.
These shafts of light are often seen extending from clouds early in the morning or late in the day. Some people refer to them as “God's rays”, but the phenomenon is known as crepuscular rays since they occur during crepuscular hours.
Rays of light can change direction when they encounter small particles suspended in the atmosphere: this is called scattering. A cloud between you and the sun can block some, but not all, the sun’s light. Where the light peeks through, scattering illuminates its path from the sun to your eyes. This creates beams in the sky.
These beams appear to converge toward the sun, but that’s just an illusion; in fact, the rays are parallel. When you look down a railroad track, the tracks look like they converge off in the distance, but we know and hope they remain parallel.
These rays are not multicoloured like a rainbow because the light is being scattered by an object. Rainbows get their colour from light entering and bouncing off a drop of water or rain.
We’ve all seen them; now we know the science behind crepuscular rays. Thanks again, Michael.
P.S. Michael did witness the noctilucent clouds the very next night!
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Cindy Day is the chief meteorologist for SaltWire Network.