Media Release

Udupi, Mar 20: Although astronomy events are those that bring awe during the night, some events from astronomy can also be enjoyed during daylight. One such event is the Equinox. The March Equinox this year will occur on the March 21.

Equinox is an astronomically significant day when the duration of the day and the night on the Earth is equal. Typically, this occurs twice –in March and once again in September, every year.

On this day, the Sun shines directly on the equator which leads to equally lit and unlit surfaces on Earth. Also, the Sun rises exactly from the east and sets exactly in the west.

On the day of March Equinox, the Sun moves from the south to the north of the Celestial Equator (Earth’s equator extended into space), initiating Summer in the Northern Hemisphere, and hence, is also known as Vernal or Spring Equinox.

On this day, the Sun’s geometric centre is above the horizon for 12 hours and below the horizon for 12 hours. However, on Equinox, the day is slightly longer than the night at the equator, as 'a day' is the duration between the appearance and disappearance of the upper edge of the Sun’s disc at the horizon.

The best way to observe equinox is through a simple experiment which will help us determine the latitude of the place we live. The Latitude of a place can be calculated on this day by measuring the length of the shortest shadow (measured between 12pm to 1pm) of an object observed, say a long candle set vertically on the ground, around noon. The shadow forms the Opposite and the candle forms the Adjacent of the right-angled triangle, θ will give the latitude. Any straight object can be used. The Taller the Object, the better the results.

The line formed by the base of the object and the tip of the shadow (when shortest) will lie along the north-south direction, and the shadow will be pointing exactly towards the North.

Astronomically, Equinox is that instance when the Sun shines exactly from the point where the Ecliptic (Path of the Sun) and the Celestial Equator (Earth’s equator extended into space) intersect. As the Sun passes through this point, it will appear to move towards the North with each passing day until June.

In India, we call this day “Vishuvat Sankranti” as 'the Sun Enters' (Sankranti) the Equinox (Vishuvat) on this day. It is also called “Vasantha Vishuva”, as it brings with it – Vasantha Ruthu (Spring season) in the Northern Hemisphere. The word Equinox means Equal Night in Latin.

Poornaprajna Amateur Astronomers’ Club wishes everyone a clear, cloudless sky on this afternoon to perform the beautiful experiment and observe the day of Vernal Equinox.