• Frank DiGiovanni

Pretty things in the sky

Updated: Jun 1

The earth is unbelievably beautiful, these are only two examples of that, but these are terrestrial examples. Whether it's daytime or night time, the beauty seen in the sky can rival anything seen on the ground.

One of the beautiful things that can be seen around either the moon or the sun is something called a "22° halo". The example below on the left is from my trip to Puerto Plata, Dominican Republic in July of 2016. While I was returning to the cruise ship, I noticed thin cirrus clouds had rolled over the island. There’s an old weather saying: ring around the moon means rain soon. Whether daytime or nighttime, the cause of the halos below are ice crystals high in the atmosphere. Hexagonal in shape, these crystals act like prisms, scattering the light through the millions of crystals suspended in the stratosphere, creating the ethereal rings around the sun or moon. Things can get even more circular under the right circumstances because these crystals can form a 46° halo around the already-existing 22° halo! But I'll let you follow your curiosity about them ;-)

The solar halo (left) courtesy of author, lunar halo (right) courtesy of Wikimedia Commons.

Light pillars are columns of light seen, especially under the same atmospheric conditions as the halos above. And like the halos, the culprit behind these pillars of shimmering light are, you guessed it, ice crystals. The conditions for the light pillars to form are flat ice crystals that have a horizontal orientation with the ground. These crystals, reflecting (as opposed to refracting) the light from their source to your eyes, create the pillar of light above its source. The larger and more numerous the flakes/crystals, the more the effect is increased.

Light Pillars, taken by Timmy Joe Elzinga in North Bay Ontario. Image courtesy of WikiMedia Commons

As beautiful as these halos and pillars are, and they are beautiful (to me), bending light is often the source of confusion when viewed from afar. Consider that the sunrise or sunset you watch occasionally isn't the actual rise or set of our home star. Nope, what you're witnessing is the sun's light being bent through our atmosphere making it APPEAR as if the sun is rising or setting when you're watching it. According to the Global Monitoring Laboratory and the Earth System Research Laboratories website: Light from the sun is bent, or refracted, as it enters earth's atmosphere. See Apparent Sunrise Figure to see how the atmosphere bends the light of the sun. This effect causes the apparent sunrise to be earlier than the actual sunrise. Similarly, apparent sunset occurs slightly later than actual sunset. But bending light is only part of the mysteriously-sounding "Fata Morgana".

Fata Morgana image, inverting a ship. Image courtesy of WikiMedia Commons.

A Fata Morgana is a complex form of a superior mirage that is seen in a narrow band right above the horizon. This makes the news every now and then with a headline something along the lines of "Floating ship seen in the sky off the coast" or "Man stunned after spotting ship 'floating' across the sky!" Named for the fairy, shapeshifting half-sister of King Arthur, sorceress Morgan le Fay is credited with the name of the mirage that significantly distorts any object on the horizon, making either unrecognizable or make these ships "float in the sky". But the only wizardry that's happening here involves temperature inversions. This happens when warmer air exists over a well-defined layer of much-colder air. (This is the opposite of what typically occurs.) This inverted layer of air acts like a lens, refracting the images, making them inverted or raising them above their actual position on the horizon.

Fata Morgana mirage, creating appearance of wall of water on horizon with sailboat (left) on the actual horizon. Image courtesy of WikiMedia Commons.

These Fata Morgana are often fleeting and are associated with legends such as The Flying Dutchman or phantom islands such as Sannikov Land. There is also circumstantial evidence that part of the reason the lookouts on the R.M.S. Titanic didn't see the iceberg was because of a cold-weather mirage, much like the fata morgana above which created a "soft horizon" as you can see above. These mirages have been captured in poetry, about some mysterious, unreachable and yet eternally longed for land. Henry Wadsworth Longfellow's 1873 poem, Fata Morgana, captures the transitory nature of these mirages in a stanza:

"Fair towns with turrets high,

And shining roofs of gold,

That vanish as he draws nigh,

Like mists together rolled—"

Brocken spectre image. Courtesy of Wikimedia Commons

No, what you are seeing is not a deity’s arrival on earth or a shadow photoshopped into the picture. Nope, what you see here is an example of something called a "Brocken spectre", German for "Brocken ghost", taking its name from a mountain peak in the Harz Mountains in Germany. First observed and described by Johann Silberschlag in 1780, Brocken spectre is another attempt of nature to make you think what you're seeing isn't real. Like all of the optical sights discussed thus far, the spectre only appears when the conditions in the atmosphere are correct. What's needed this time isn't ice, but mist or fog, the sun and a little geometry.

Brocken Spectre at Nipstone Rock, UK. Image courtesy Dave Croker.

On a foggy-enough day (as seen above, below and at right,) and with the sun or other illumination source at the back of the observer, their casted shadow appears to increase its size tremendously. This optical illusion occurs when the observer judges their shadow on relatively nearby clouds (as seen above) to be at the same distance as faraway land or objects seen through gaps in the clouds, or when there are no reference points by which to judge its actual size, such as the image at right. This can even happen if you're standing in front of a car with its headlights on, during a foggy day or evening. Get the angle correct and even a jetliner can cast haunting looking shadows with their "glory rings" of rainbow around the shadow.

Brocken Spectre, mid flight. Image from Wikimedia Commons.

But for our last "pretty thing" in the sky, we must wait until the daytime turns to night... For it is when the hemisphere you live on is in shadow, that true beauty can be seen by looking up. Come nighttime and the sun well set, colors can come out and dance in the sky and those lucky enough, can view them from above! You know them as aurora.

The video above is a sequence of shots taken on September 17, 2011, on a pass from south of Madagascar to just north of Australia over the Indian Ocean, and was taken by the crew of Expedition 28 on board the International Space Station! Aurora Australis or Aurora Borealis are the names for these phenomena given to the colors based on which hemisphere they're seen in; Australis for the southern hemisphere, Borealis for the northern.

Aurora photographed in Estonia March 19, 2015, via Wikimedia Commons

While these lights aren't threatening to human life as some culture's stories originally thought, many tales were told regarding these ghostly, celestial dancing lights. The website Natural Habitat Adventures provides us with a few of these.

  • Indigenous Greenlanders believed that the lights were dancing spirits of children who had died at birth.

  • In Alaska, some Inuit groups saw the lights as the spirits of the animals they had hunted, namely beluga whales, seals, salmon and deer.

  • In Finland, a mystical fox was thought to have created the aurora, its bushy tail spraying snow and throwing sparks into the sky.

  • In Estonia, one legend said the lights appeared when whales were playing games. Another said they were sleighs taking guests to a spectacular wedding feast.

Looking at the image above it is easy to see that it appears like something's coming falling to Earth, but we know there's only particles from the solar wind crashing into the earth's magnetosphere and funneling towards the poles, which creates the beautiful colors and patterns. Each color occurs when the high energy particles entering Earth’s atmosphere collide with a particular element in the atmosphere, and during the collision emit light at a particular wavelength. Red, blue, green are the most common colors, but yellow, purple and pink are occasionally seen. All of these colors have to deal with the excited oxygen and nitrogen molecules and the altitude they're in when struck by some of these high-energy particles. And perhaps shockingly, these lights "only" happen between 56 and 93 miles (90 and 150 km) above Earth's surface; some are also estimated to occur at over 620 miles (1,000km) up!

The sky creates many different and spectacular images. Things like Sun dogs, the Belt of Venus, Alpenglow and Green Flashes; way too much for me to get into here without making this post much longer. I'll leave you to your curiosity to find out what they are and why I think they're one of the many pretty things in the sky =)

Happy searching!

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