Ira Sevaya and knowledge in Science
Every year, the Sri Pada season begins on the Unduvap Full Moon Poya day and the season ends on the Vesak Poya day in the following year. As you know, the present Sri Pada season began on December 13 with traditional religious practices. Apart from the religious gains through worshiping the Lord Buddha’s foot print, Sri Pada pilgrims get an opportunity to observe the environment and the sky specially during the night and early morning hours without any obstacle, from a location at high altitude.
Many natural types of scenery are beautiful. The eastern sky in the early hours is also an extraordinary natural scenery irrespective of the viewing point on the globe. The most eye catching sights are the colour changes 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.
With the scientific understanding of the nature, man started to understand the reality (or science) behind many of the natural events which had been explained based on concepts in old days. But as the scientific understanding has not gone to the roots of all nations at the same speed for many reasons, intellectuals still struggle to make the people aware of the reality behind many natural events because most of natural phenomena have been related to concealed forces known as gods, ghosts and many extraordinary unseen super natural powers.
Knowledge in science and technology is well taught in developed countries while countries like Sri Lanka are holding end positions of the line of the literacy. It may be for this reason that the President, Prime Minister, the Minister of Science and Technology and Minister of Education are taking all necessary steps towards the improvement of the knowledge of children in science and technology. Even though we are late, this is much appreciated. For the fulfillment of the hopes of the Government, the education institutes and authorities and media have to give fullest corporation through all possible ways. The media has a big role to play in this regard through sparing more space in their media for conveying the scientific understanding to the public in all fields.
Out of the many examples with no real understanding among people, rainbow, halo, colours of the sky, lightning and glistening spots of the atmosphere are only a few. The natural event called ‘Ira Sevaya’ also has been accepted by the majority of us as a superstitious event that is special only to Sri Pada. But this is a natural phenomenon which can be explained using the knowledge in Physics of light taught to school children in their science lessons.
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 if he observes the eastern sky in the early morning, a few minutes before sunrise time, from a high spot like Adam’s Peak. The same thing can be visualized at many high locations of the world and in aircrafts flying at high altitudes. The Ira Sevaya is the shaking sun (real images of the sun) which can be seen above the horizon mixed with all the effects of colouring. It is not a single image, but multiple images. The images are seen in different locations before you see the actual sun above the horizon a little later and let us see how and why this happens.
Dancing sun
As this dancing of the sun, Ira Sevaya, can be observed only in the morning just before sunrise, it should be a game played by rays of light. A light ray encounters a number of effects when it travels in a medium or passes a sharp edge, or travels 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 phenomena are explained in Physics under the topics of reflection, refraction, diffraction, scattering, diffusion and total internal reflection which differ in meaning from one another. 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 fluctuation or dancing of the sun a few minutes before sunrise, when seen at the top of a hill, is caused either by Total Internal Reflection (TIR) or diffraction of the sun’s light beams by the lower atmosphere very close to the earth surface at horizon. Under certain conditions, these both phenomena may lead to instances with the dancing sun in the eastern sky.
Light rays undergo 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 in Physics), the rays are reflected towards the denser medium just like they get reflected by a plain mirror. In the early hours of the day, the dawn, light rays from the un-risen 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 and 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 behind the horizon, by the solid earth, an observer/pilgrim at the top of a hill such as Sri Pada or a passenger in a flying aircraft, can see the sun through the reflected light rays and he misunderstands that as the real sun while it is really an image of the sun. Those images of the sun are usually seen above the horizon.
There is another very important astronomical reality which is not well understood by the laymen. While our planet earth, whose radius is 6370 km, makes one rotation around its own axis in 23 hours 56 minutes and 4.1 seconds (not exactly 24 hours as many people believe) it travels in an elliptical path around sun in 365.242 days (not exactly in either 365 or 366 days) keeping an average distance of 150 million kilometers from the sun. After short calculation using these data, one can conclude that any location or a point on or near the equator of the earth moves through about 460 meters towards east in a second and while rotating, the earth moves a distance about 30000 meters in a second around the sun. So we view the universe or any object from a point having very fast motions even though we do not feel it. As a result, when an observer observes the eastern sky he sees a large number of images of the sun in a short as time passes. 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. Until the sun rises above the horizon, a person viewing the sky from a place at high altitude (Adam’s peak or any mountain or inflight) can entertain this extraordinary event which is a natural phenomenon.
Real sun
A few minutes later, the real sun rises above the horizon and as the total internal reflection does not occur now, one can see only one figure which is the real sun just at the horizon. This position of the real sun is usually below the positions of the images seen a little earlier.
Ira Sevaya may also be partly a result of the phenomenon called 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 called diffraction at the earth surface and breaks the ray into a number of branches, which are transmitted in different directions. As in Total Internal Reflection, a number of images are 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 main two phenomena Total Internal Reflection and diffraction causes the so-called Ira Sevaya, a natural event occurring all over the world every day. The sun and earth are continuously moving and rotating bodies. The sun is the common energy source providing energy to the whole world from a distance of 150 million km from us. It is not close to Adam’s Peak. Before it rises over our horizon that can be seen from Sri Pada hill, the sun spends hours in the sky in other parts of the world. The physics behind the event called Ira sevaya is same for the whole world. Where ever you are, you can observe this event provided that all necessary requirements are fulfilled. Some of the requirements are significantly high altitude of the observer, easily observable horizon, clear eastern sky, cloud and mist less environment.