June 21 is the Summer Solstice, which is the longest day of the summer season and takes place in the northern hemisphere when the Sun is directly over the Tropic of Cancer.
It signals the start of the summer season in the northern hemisphere and the beginning of winter in the southern hemisphere.
This phenomenon occurs twice a year, once in the northern hemisphere (between June 20-22, depending on the year and time zone) and once in the southern hemisphere (between Dec 20-23).
What solstice means?
The word “solstice” originated from Latin word “sol” which means sun and “sistere” which means stationary or stand still. The summer solstice occurs between June 20 and 22 every year.
At this time, the Earth is at a point where its tilt is at the greatest angle to the plane of its orbit. This results in one hemisphere receiving more sunlight and a longer day than the other.
NASA has shared an image on Twitter that gives us an insight into Earth’s position with respect to the Sun during both these events.
Today is the northern #SummerSolstice, marking a new season as well as the longest day in the northern hemisphere. While it’s a time to enjoy the warmth & light, it also signifies an astronomical event caused by the tilt of Earth’s axis. 🌍☀️ Read more: https://t.co/Wt5BhAKAq1 pic.twitter.com/wsuKWdXr03
— NASA (@NASA) June 20, 2021