A glory, created by scattering of sunlight among the water droplets in a cloud, surrounds the shadow of a plane. Credit: Wiki
Plan on flying somewhere this summer? If it’s sunny and you’re lucky enough to sit on the side of the plane opposite the sun, take a close look out the window. On the clouds below, you might just see the plane’s shadow surrounded by shimmering rings of color called a glory.
The rings resemble a little corona like you sometimes see around the moon at night. Glories form in lower clouds made of water droplets; you’ll often see them after the plane breaks through a lower cloud deck into sunlight.
A corona around the moon is also caused by diffraction. Glories involve refraction (bending of light into the water droplets), reflection (light reflected back out toward the observer’s eye) and diffraction. Credit: Andrew Kirk
Coronas and glories are both caused by a process called diffraction. Sunlight shines into the droplets and is reflected back toward the person sitting in the plane. One the way to their eyes, the cloud’s minute droplets interfere with light’s progress, scattering or diffracting it in many directions. The scattered light rays bump into and interfere with each other to create a series of concentric rings.
Since white light is made of all the colors of the rainbow, we see individual colors separated out across the rings -red on the outside and blue inside.
Smaller water droplet sizes mean bigger, brighter glories. Since clouds don’t always have consistent droplet sizes, glories shrink and expand while you watch as if alive. Glories can also change in size as your altitude rises or drops during a flight. These targets of colored lights are one of nature’s more alluring sights – don’t miss the chance to see one if you’re traveling by air.
Planet Earth seen from the top down. Ocean scientist Norman Kuring pieced together this composite image of Europe, Asia, North Africa, and the entire Arctic. It was compiled from 15 satellite passes made by Suomi-NPP on May 26, 2012. Click for hi-res version. Credit: Norman Kuring, NASA/GSFC/Suomi NPP
NASA just released a very cool picture of planet Earth seen from a new perspective – looking down over the North Pole and Arctic. Scientist Norman Kuring of NASA’s Goddard Space Flight Center stitched together satellite photos to create this view of Earth looking down from 70 degrees north, 60 degrees east (western Siberia). If summer’s heat is already getting to be too much, click on the photo for a larger version and cool off.
Noctilucent clouds above the Tibetan Plateau photographed on June 13, 2012 by astronauts aboard the International Space Station. Also known as polar mesospheric clouds, they’re formed of ice crystals some 50 miles high – nearly at the edge of outer space. Click for hi-res version. Credit: NASA
Back on June 13 I wrote about a nice display of night-shining or noctilucent clouds visible in northern Minnesota during late evening twilight. Turns out ground dwellers weren’t the only ones watching the northern sky that night. Space station astronauts flying over Tibet looked out the window and snapped the photo above of the same delicate clouds from a much higher perspective.
June and July are the best months to watch for the elusive sight. I usually start checking the northern sky for the first faint traces of the clouds about an hour and a quarter after sunset.
