Scientific explanation of Ira Sevaya

by K. R. Abhayasingha

Every year, the Sri Pada season begins on the Unduvap Full Moon Poya day and the season ends on the Vesak Full Moon Poya day the following year. Accordingly, the next Sri Pada season will begin on the Unduvap Full Moon Day, December 27 and will end on the Vesak Full Moon Poya day, in May 2013. Many of the Sri Lankans, irrespective of their religion or race, may be making arrangements to join the Sri Pada pilgrimages in the coming season.

Even though the Sri Pada pilgrimage is religion related, it also has some educational value as well because all pilgrims joining the ceremony get an opportunity to observe the environment which is usually different from their routine observations in their native places. Atmosphere at about two kilometres above sea level, clouds floating below pilgrims, the circular horizon, special varieties of foliage that grow at high altitudes are some of them. The chance of observing the sky without any obstacle is another important matter.

As pilgrims who climb to the top of Samanola hill (or Adam's Peak) to worship the Buddha's Foot Print can observe the sky during all hours of the day and night. The most extraordinary sights are the colouration of the eastern sky in the early morning and western sky in the late evening plus the shaking of the early sun in the eastern horizon which is termed as ‘Ira Sevaya’ by Sri Lankans. This ‘Ira Sevaya’ is the most expected sight from the Sri Pada.

Natural events

As many natural events in the environment were not understood by the man during the past, many concepts have been proposed and related to the unexplainable natural events by the philosophers during the old days. With the scientific understanding of the nature, the man started to know the reality (or science) behind many of the natural events which had been explained based on concepts in earlier days.

The scientific understanding has not gone to all nations at the same speed for many reasons. Therefore, the intellectuals still struggle to make the people aware of the reality behind many natural events because many concepts are based on beliefs on gods, ghosts and many extraordinary unseen powers or super natural powers.

The situation in our country is pathetic as the understanding of the public as far as nature is concerned. Most of the natural events have been conveyed to the nation through concepts. Out of the many examples, rainbow, halo, colours of the sky, lightning, glistening spots of the atmosphere represent only a few. The natural event ‘Ira Sevaya’ also has been accepted by the majority of us as a superstitious event that is special only to Sri Pada Samanola mountain.

The inauguration of the Sri Pada season is usually a big event with a number of media personnel (print and electronic) participating with all modern technology with the intention of providing information to the nation. The media get the support of Bhikkhus and professors for describing the activities performed and the environmental observation from the top of Sri Pada.

Ira Sevaya

The Ira Sevaya, (fluctuation of sun's images a few minutes before the sun rise) is one of the most beautiful and colourful visual observations one can see in the world. When one observes the sky in the early morning, a few minutes before the Sun rise time, from Adam's Peak, the sky over the eastern horizon changes colours so fast that one can observe beautiful designs in the sky.

Mixed with all the effects of colouring, the shaking sun (really images of the sun) can be seen above the horizon. It is not a single image, but a multitude. The images are seen in different locations before you see the actual sun above the horizon a little later.

One who does not know what is really happening in the eastern sky may believe that the sun moves up and down several times to worship the Foot Print of the Buddha as it is mentioned in myths about Sri Pada. As it is not an easy thing to count the number of visible images of the sun, most of the pilgrims including some veterans used to give credence to this belief especially since the phenomenon could not be explained in lay language.

A light ray encounters a number of effects when it travels in a media or passes a sharp edge, or travel through a common surface between two transparent media such as water and glass or air and glass or even between two air layers with different characteristics. Such behaviour is explained under the terminology of reflection, refraction, diffraction, scattering, diffusion and total internal reflection which differ in meaning from one another.

Phenomena

A student of physics, who has studied these phenomena, can explain the science of the natural events such as rainbow, mirage, fluctuation of sun before the sun rise, eclipse, halo event and colourful patterns seen in the sky particularly in the north and south polar areas.

The apparent movement or shift of the sun a few minutes before the sun rise, when seen at the top of a hill, is caused both by Total Internal Reflection (TIR) and diffraction of the sun's light beams by the lower atmosphere very close to the earth surface at horizon.

Light rays undergo through Total Internal Reflection when they meet a common boundary between two media, one denser than the other (like glass and water, water and air or glass and air) provided that the incident rays travel through the dense medium before meeting the common boundary. When the incident angle exceeds a particular value (called critical angle), the rays are reflected towards the denser medium just like they are reflected by a plain mirror.

Light rays from the unrisen sun are incident through the dense air which is at very low level, close to the earth surface, of the atmosphere towards rare (low dense) layers which are above surface layers.

Under the circumstances, light rays get reflected towards the dense layer at boundaries separating dense/rare air layers. Even though the actual position of the sun at this time is covered by the solid earth, an observer/pilgrim at the top of a hill such as Sri Pada, can see the sun through the reflected light rays and those images of the sun and are seen above the horizon.

As this happens while the sun and the earth are moving, an observer sees a large number of images of the sun as the time passes and the apparent positions of images are not the same. The observers may misunderstand the changing of positions of the sun's images as movements of the sun up and down in the eastern sky.

Internal reflection

A few minutes later, the sun rises above the horizon and this is the real sun. As the total internal reflection does not occur now, one can see only one figure which is the real sun just above the horizon. This position of the real sun is usually below the positions of the images seen a little earlier.

Ira Sevaya may be partly a result of the diffraction of solar light beams at the tip of the earth in the early morning. A light ray finds the body of the earth as a tiny sharp edge and therefore it undergoes the phenomenon diffraction at the earth surface and breaks the ray into a number of branches, which are transmitted in different directions. Similarly, in total internal reflection, a number of images is formed by diffraction too and an observer on a high location can see fluctuation of images of the sun before he sees the real sun rise.

The geographical situation of Sri Lanka in the Indian Ocean may be another enhancing support in forming some more images of the rising sun. The reflection of solar radiation from the moving sea waves in the Bay of Bengal also can result in the formation of images of sun above the horizon which is known as Ira Sevaya.

Energy source

The main phenomena, Total Internal Reflection and diffraction, cause the so-called Ira Sevaya a natural event occurring all over the world, every day. The sun and earth are moving and rotating bodies. The sun is the common energy source providing energy to the whole world from a distance of 150 million kilometres from us. It is not close to Adam's Peak (as some people believe). Before it rises over the horizon that can be seen from Sri Pada hill, the sun spends hours in the sky in other parts of the world!

Media personnel who will telecast and broadcast from Adam's Peak on December 27 should gather knowledge of the natural events and phenomena one could see from a high altitude before planning to describe the old concepts with beautiful words that would mislead and misguide the audience, listeners and viewers.

They should find the support of Bhikkhus or professors who understand the scientific background of natural events.

(The writer is a former Director of Meteorology.)