Fata Morgana

ABC Wednesday
August 16th, 2017

The letter is F for FATA MORGANA

Earth Science Picture of the Day is a service of Universities Space Research Association

A Fata Morgana is a complex form of

superior mirage that is seen in a narrow band right

above the horizon.

This particular Fata Morgana is a mirage observed

from Brittany, France, and it is affecting the rather featureless

Island of  Ile d'Houat, located about eleven miles from 

the shoreline.

This photo was taken by Guillaume Doyen who says

"notice that parts of the island seem to be floating or looming.

Mirages such as this occur when there's a steep temperature

gradient.:  when a layer of colder air (immediately above the seawater)

is trapped below a layer of warmer air - a temperature inversion. the temperature at the time the picture was snapped was 98F"

Guilllaume Doyen goes on to say

"under these conditions light rays from a distant object

(the island) are curved toward the eye by layers of air

having different densities, caused by the abrupt temperature gradient.

So it seems that the island is more or less smeared upwards into a cliff."

This Fata Morgana mirage lasted for a little more than an hour.

Before science began to look into mirages, and their cause,

mirages were firmly in the realm of mysticism, and the fata morgana

takes its name from Morgan le Fay, that wicked half sister of King Arthur,

enchantress and treacherous fairy.

You may well ask how bending light creates a mirage,

 and here is where your brain enters the picture.

I learned this online, and I quote verbatim....

"When light hits your eyes, your brain assumes it arrived there in a straight path between you and the object reflecting the light.  So if light is bent on its way toward you your brain will think the object is where it would be if the light's path was straight.  This is why when you are looking down on a surface of water, objects under the surface will appear to be in a different spot than they actually are.....the human brain doesn't automatically account for refraction"

The writer of this article goes on to say 

"the brains of some birds like ospreys do correct for the effect

so that when they dive headlong into the water after a fish,

they are right on target"

but I digress.....

Christina Rossetti wrote a poem entitled FATA MORGANA

and it goes like this....

A blue-eyed phantom far before

is laughing, leaping toward the sun:

Like lead I chase it evermore,

I pant and run.

It breaks the sunlight bound on bound:

Goes singing as it leaps along

To sheep-bells with a dreamy sound

A dreamy song.

I laugh, it is so brisk and gay;

It is so far before, I weep:

I hope I shall lie down some day,

Lie down and sleep.

Perhaps she was referring to the constantly changing conditions 

of the atmosphere which causes the Fata Morgana

to change within just a few seconds of time,

alternating between stretched and compressed zones,

either erect or upside down.

If you are interested in reading more of the history of the Fata Morgana
I would suggest you Google 
"Fantastically wrong: the bizarre mirages that once 
scared the bejesus out of sailors"

and perhaps some day you might be in the right place at the right time
and see for yourself the fantastic
Fata Morgana

For more interesting Fs visit here
at ABC Wednesday
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