The Arms of Buddha

Tuesday 18th February 2014

Our speaker was Mike Frost who, by day, is a systems engineer but in his spare time is a passionate amateur astronomer. Amongst other things, he is director of the Historical Section of the British Astronomical Association and confesses on his website to being an "eclipse chaser" which means his hobby takes him all around the world.

Previously he had talked to the Society about historical eclipses visible in Warwickshire but for our February meeting he led us through the amazing subject of anti-solar phenomena with the rather cryptic title "The Arms of Buddha".

The title of the talk was inspired by a Henry Miller quotation, which reads: "In the Himalayas where the same phenomenon occurs, it is said that a devout follower of the Buddha will throw himself from the peak into the arms of the Buddha". This excerpt is taken from Miller's book "Big Sur and the Oranges of Hieronymous Bosch" which is his book of musings about California, published in 1957.

The phenomena Miller is referring to is known as the "Spectre of the Brocken" which gets its name from similar apparitions on the Brocken (the highest peak of Germay's Harz Mountains). Just like in the Himalayas, Miller was able to observe the effect for himself when living in the hilly region of Big Sur, California

In his book he is standing on a high peak with the Sun behind him in the morning and below is a thin stable layer of fog. Due to the low Sun his shadow is stretched to resemble that of a giant with extremely long legs and should he stretch out his arms they too would seem extraordinarily long. Around Miller's head would be a circular halo of bright light that may have been surrounded by rainbow-coloured rings. The halo itself is known as a "glory".

Perhaps some Buddhists mistook this stunning yet rarely seen effect for the Buddha himself beckoning them into Nirvana and so they jumped from their mountain-top viewpoint into what they thought were the Buddha's arms. Nowadays most people see glories from high peaks or from an aircraft window looking down onto fog or clouds.

The explanation behind the distorted shadow is that it is simply due the low Sun casting long shadows and is a common sight in sunny days with tall trees and buildings casting elongated shadows. The halo around the observer's head is much more complicated and is caused by sunlight being scattered backwards by individual water droplets.

In fact, the glory formation process can be predicted using something called "Mie scattering theory" using Maxwell's equations of electromagnetism but the process is still not completely understood. Work done by Peter Debye shows that the main source of the glory's central illumination is light that has been reflected just once inside the water droplets; with additional rays coming from light reflected 10, 6 and 5 times inside a drop. However, this is not the complete picture as analysis has shown that some light travels along the actual surface of the droplet before re-emerging.