Friday, January 22, 2010

Superior Mirage

Ordinary ground mirages look like puddles on hot roads in the desert. They’re called inferior mirages and they’re fairly common.

Far more rare and magical are superior mirages, also known as fata morgana. They occur when a layer of very cold air is overtopped by a warm air layer. The change of densities bends the light and inverts faraway images.

Phantom icebergs, ships, mountains, or even entire cities appear upside down, floating in the air. The observed objects are often so far away that they would normally be invisible, hidden behind the curvature of the earth,

Superior mirages usually occur in polar regions over ice or cold water. Sometimes they look like spiky mountains. In Iceland these are called halgerndingar. Floating cities or ships are called hillingar in Icelandic.

In her book Half-Broke Horses, Jeannette Walls describes her grandmother’s eyewitness account of a floating town in the high desert of Arizona: “There, floating in the air above the horizon, was an upside-down town. You could see the low, flat stores, the adobe church, the horses tied to the hitching posts, and the people walking in the streets.”

Images from Astronomy Cafe
More examples at the Mirage Gallery

5 comments:

Rob Rey said...

Ah, how interesting! Just last week I was reading Hans Christian Andersen's story of "The Wild Swans" in which the main character Elisa's brothers, turned to swans, fly her across the ocean in a net. Along the way she sees "Fata Mogana's lovely castle in the air, a place that is always changing."
Now I know what that was about!
My annotated version of the tale also tells me that Fata Morgana is "also known by the named of Morgan le Fay, an enchantress with the ability to change her appearance. Trained by Merlin the Magician..."

Mary Bullock said...

So Cool!! How do you know this stuff??

Gordon Napier said...

I once heard that this illusion inspired a myth of mushroom shaped islands. That would be a great idea for a fantasy painting, a city on top of an island that tapers in and then expands out again- or indeed a ruin on the sloping surface of one of these islands that has given in the centre and tipped to one side.

Dan Gurney said...

On Sept 16, 2008 I saw exactly this phenomenon occur on the Pacific Coast, looking west from Point Reyes to the Farallon Islands. I *knew* it was an inverted mirage, but I had never seen or heard of one before, or could explain how it would occur. The image persisted more than an hour, changing sometimes appearing to be tall island mesas, sometime more like a formation of enormous aircraft carriers with perfectly flat tops Now I know.

James Gurney said...

Mary, my wife gets the credit for finding out about this one. She was reading the novel that mentioned it, and it showed up on a quick search. I've never seen one. Dan, you're lucky to have been an eyewitness. Rob, yes, the Fata Morgana name is perfect for this effect.