In view of the solar eclipse on the new moon day of December 26, this article aims to enlighten the facts and debunk a few misconceptions. The partial eclipse will be seen from parts of Kathmandu, starting at 8:43 am and end at 11:31 am, with the peak at 10:01 am.

For the first time, in the 18th century, evidence was found about the harmful effects on the eye caused by watching a solar eclipse. The effect depends upon the amount of radiation and exposure to it. The effects are caused due to the heat induced photo-chemical process.

The ultra-violet rays affect the skin (red blisters or carcinogenic effects), its heat affects the retina and incites many other problems. The partial solar eclipse can be viewed with the naked eyes only for a few seconds, but a total solar eclipse—to be seen on August 21—is never safe to watch with the naked eyes.

Even when 99 per cent of the sun is covered by the moon, it is not safe to watch it without precautionary measures. This is because the harmful rays coming from the remaining 1 per cent of the sun especially affects the cornea of our eyes.

A black spot in the middle of the visual field shall always remain due to the permanent and irreversible damage to the centre of the retina. Why is it more harmful to watch the sun during a solar eclipse than at any other time? During an eclipse, the sun is blocked by the moon, and there is darkness all around for a while.

At this time, the pupil of our eye is dilated, and suddenly when some portion of the sun becomes visible, many harmful rays enter our eyes that even penetrate parts of the retina. On a normal day, the sun is so bright that we cannot look at it.

Similarly, at the time of the eclipse, the earth, the moon and the sun fall on the same plane in a straight line, causing the gravitational pull of each of the celestial bodies to combine. As a result, harmful rays, which would otherwise scatter in any other direction in space, are streamlined to precipitate onto the Earth. Radons are among those harmful rays, which can easily set in damp or wet materials for some time. So, there are scientific grounds for the old belief that water and food items exposed to the eclipse should not be consumed.

It is best not to watch a solar eclipse. It is heard on the grapevine that looking through a medical x-ray film, photo negatives or polarising spectacles saves eyes from those harmful rays, which is not true.