Question

Which are the two Solstice days?
A) 21 June and 22 December
B) 21 July and 22 December
C) 21 August and 22 December
D) 21 March and 23 September

Answer 1

Hint: Ancient Greek celestial navigation included the concept of the solstices. They invented the concept of the celestial sphere as soon as they realized the Earth is spherical, an imaginary spherical surface spinning with the heavenly bodies fixed in it. The sphere can be accepted as long as no assumptions are made regarding the distances between the bodies and Earth.

Complete answer:
The solstices and equinoxes are used in many nations to determine the seasons of the year. When the plane of the Earth's Equator touches the geometric centre of the Sun's disc, it is called an equinox. This happens twice a year, around the 20th of March and the 23rd of September. In other terms, it is the time when the visible Sun's centre is directly above the Equator.

On the celestial sphere, a solstice occurs when the Sun appears to be at its most southerly or northerly excursion relative to the celestial Equator. Every year, around June 21 and December 22, two solstices occur. The term solstice can also refer to the day when this happens in a broader meaning. The day of the solstice is either hemisphere that has either the greatest sunlight of the year, summer solstice or June solstice, or the least sunlight of the year, winter solstice or December solstice, for any area other than the Equator.

After the 22nd of March, other parallels in the northern hemisphere between the Equator and the Tropic of Cancer begin to get perpendicular rays. Only on June 21st and December 22nd do the sunrays at the Tropic of Cancer and Capricorn become perpendicular. These are solstice days.

So, the correct answer is Option ‘A’ i.e, 21 June and 22 December.

Note: The solstice time, unlike the equinox, is difficult to predict. As the Sun approaches its maximum or minimum declination, the fluctuations in solar declination become less. Changes in the sunrise or sunset azimuth owing to atmospheric refraction are similarly difficult to discern.