What is a solstice?
A solstice is an event which is said to occur when the Sun reaches its maximum elevation for any of the hemispheres with respect to the celestial equator i.e. the path of the sun in the sky is either farthest north or farthest south.
About the Earth’s movement around the Sun and about its axis
The Earth’s rotational axis (the line passing through its geographic north and south poles) is tilted at an angle of 23.4 degrees from the vertical, possibly due to collision with a huge object during the early stages of the formation of the solar system. As the axis always points in the same direction, the North pole is closer to the sun for 6 months and father from it for the next 6 months with respect to the south pole
Summer solstice – Longest day of the year
At the summer solstice, the Sun travels the longest path through the sky, and that day, therefore, has the most daylight i.e becomes the longest day.
When the summer solstice happens in the Northern Hemisphere, the North Pole is tilted about 23.4° (23°27´) toward the Sun. Because the Sun’s rays are shifted northward from the Equator by the same amount, the vertical noon rays are directly overhead at the Tropic of Cancer (23°27´ N). Six months later, the South Pole is inclined about 23.4° toward the Sun. On the day of the solstice, in the Southern Hemisphere, the Sun’s vertical overhead rays reach their southernmost position, the Tropic of Capricorn (23°27´ S).
For the Northern hemisphere, summer solstice happens between June 19- 21, while for the Southern hemisphere, it happens between December 19-21
During the summer solstice, the northern hemisphere stays lit up by sunlight while during the “winter solstice” (i.e. summer solstice for the southern hemisphere) the southern hemisphere stays lit up by sunlight
Relation to seasons
According to the astronomical definition of seasons, the summer solstice also marks the beginning of summer which lasts until the autumnal equinox i.e the day when the rays are perpendicular to the equator (September 22 or 23 in the Northern Hemisphere, or March 20 or 21 in the Southern Hemisphere).
Solstices have been known to mankind since ancient times. Mankind has marked the apparent movement of the sun in the sky and the changes in daylight. The Stonehenge, a prehistoric monument in the UK has been built with the solstice in mind. 25 ton heavy stones have been arranged in a pattern such that the altar stone is bathed in light on the day of the solstice
Even today, it is celebrated by many cultures. For example, in Scandinavian countries, the holiday of Midsummer’s Eve is observed on a weekend near the time of the solstice
When is the next summer solstice?
The summer solstice for the northern hemisphere is almost upon us. It is on June 21, 2020
If you’re in the Northern Hemisphere, you can use this opportunity to observe:
- Early dawns and late sunsets
- High arc of the sun across the sky each day.
- How high the sun appears in the sky at local noon.
- Your noontime shadow. Around the time of the solstice, it’s your shortest noontime shadow of the year.