Why does darkness set in early ?

by Sumana Saparamadu

Now darkness sets in early. By 5.30 p.m. it is quite dark, isn't it? The day is getting shorter and shorter and the nights are longer and longer, with each passing day. Why?

The Sun is over the southern hemisphere now and will be moving further and further south each day, until mid-December. It will be over the Tropic of Capricorn, 23.5 degrees South of the equator on December 23.

This will be the shortest day for all of us in countries north of the equator. Then it is mid-winter north of the tropic of Cancer, and mid-summer and the longest day in countries south of the Tropic of Capricorn such as Australia, New Zealand, South Africa and some countries in S. America.

From December 24, the Sun will again turn northwards and the days will get longer and longer and the nights shorter. Day and night will be equal at the equator on March 21. On this day the Sun is directly over the equator and the day is called the equinox.

The equinox comes twice a year on March 21 and on September 23. It was overhead the equator on September 23, which is known as the autumnal equinox as it marks the beginning of autumn in the northern hemisphere. March 21 is the vernal equinox, marking the beginning of Spring in the northern hemisphere.

The Sun was overhead of Sri Lanka in early September when it was morning south, and will be overhead of Sri Lanka again in early April, over Dondra on or about April 7.

Try to make a note in your diary or in your notebook when the lights in your home are switched on each day. This week it's done earlier than last week and next week it will be still earlier.