WITH each new generation — every 25 years or so — science and scientific thought, and new scientific ideas undergo a change and are eagerly accepted by new adherents

There was a time, lasting thousands of years, when people feared comets. It took them a long while to get over this fear — until a couple of centuries ago when the great astronomer Sir Edmund Halley put permanent rest to these needless fears doing the rounds of social and political circles unabated.

However, we are still left with the strange but easy-to-understand eclipses which, even today are grossly feared and loathed by many. For the entire world, it will still take some time to figure out why. We shall do exactly that today.

Simply speaking, an eclipse takes place when the Sun, Earth and moon are in a straight line. Although their diameters differ, the Sun and moon appear to be of the same apparent diameter, that is half an inch or 31 1/2 minutes of an arc where one arc is one degree, and 30 minutes is equal to half a degree in the sky. And 31 1/2 is just over half a degree (1 degree has 60 minutes, and any further divisions comprise 60 seconds). As a comparison, the entire sky (from East to West, or from North to South or whatever direction) is 180 degrees across and the full circle is 360 degrees. Although half a degree is small, it is not too small for that is the apparent size of the Sun and moon as it appears to us.

In a total solar eclipse, in the course of its orbit, the moon hides the brilliant solar disc completely and there is a small period of near total darkness so that the stars appear and the birds rush towards their nests believing that the night has suddenly fallen. But mercifully for birds and animals, this period is only eight minutes long, never longer.

The moon revolves round the Earth, which in turn revolves around the Sun. (which itself, together with the entire Solar System goes in orbit around the centre of the galaxy). There comes a time when the three bodies align themselves in a straight line with the moon at the centre. The moon disc is just enough to cover the solar disc, causing a total solar eclipse. When that happens, Sun’s atmosphere flashes into view; the lovely red prominences and the pearl-like corona appear along the edge of the solar disc (these are severe blasts of nuclear fire emanating from the pit of the sun).

Also, if the Sun is completely hidden by the lunar disc, there is a total solar eclipse, but if it does not and only a small portion is covered, like a single bite into the apple, partial eclipse occurs which again is a marvel of nature.

You would imagine that the total eclipse should occur every year whenever the three bodies are in exact line but it does not happen every year, nor everywhere. It is, in fact, a very rare event at any given place, a once in a life time occasion. Because their mutual distances differ each time they appear to be in line for a total solar eclipse but in fact, they do not because of their (apparently) differing diameters.

For instance, I once travelled all the way to a small, remote castle in Norway just to see a total eclipse. Despite all the money and effort I made, I couldn’t see it because of a heavy cloud covering right at the time of eclipse!

So when the moon covers Sun’s disc completely, it becomes completely dark. Only the corona is visible and presents a lovely sight especially when the prominences also appear in full glory. It is a colourful scene which appears in many beautiful colours. Then the moon moves away, as it must, the Sun gradually brightens up and is soon restored to its intrinsic glory. Totality lasts briefly, that is, from a few precious seconds to just about seven and a half minutes.

Solar eclipses occur two to three times in an year, but it is not possible for everyone to see them at any given place on the earth. A total solar eclipse may be seen once in a whopping 360 years. Yes, it is that rare! And the next is due to take place on March 15, 2015, over a tiny portion of the earth.

Next we shall discuss some technical aspect of eclipses, both solar and lunar. Next issue, if you may! Good bye and God bless.