The summer solstice occurs on June 21, a spectacular occurrence in which the northern hemisphere has the longest day of the year (while the southern hemisphere has the shortest). Cities in India, such as Ujjain and Gandhi Nagar, have a zero shadows moment, when shadows disappear around midday.
But what exactly is a solstice, and why does the longest day of the year occur on this specific date? The following are answers to some of the most often asked questions about the summer solstice.
What exactly is a solstice?
Every day, between dawn and sunset, the Sun’s position with relation to the Earth shifts from east to west. Throughout the year, though, the Sun moves in a similar but somewhat less visible direction – from north to south.
While the latter movement is difficult to see on a daily basis, the difference may be readily detected over time by monitoring the location of the Sun from a fixed point on Earth (such as your house).
However, the Sun appears to’stand still’ for two days each year when it pauses on the northern and southern borders before changing course. These are known as the solstices, which are derived from the Latin words sol (“sun”) and sistere (“to stand still”).
These Pause days occur twice a year, once in the summer (about June 20-22, depending on your time zone) and once in the winter (around December 21-22).
What causes the Sun to go north-south?
What causes the Sun to go north-south?
The axial tilt of the Earth.
Because of our planet’s axial tilt, the Sun moves north-south relative to its location. But what exactly does axial tilt mean?
The imaginary line drawn connecting Earth’s north and south poles is not perfectly vertical. The Earth, on the other hand, has an axial tilt of around 23.5 degrees off its imaginary vertical axis. This tilt leads the two hemispheres to face the Sun and its direct rays at different periods of the year.
As the Earth rotates around the Sun, the most direct sunlight shifts throughout the year between the Tropics of Cancer and Capricorn. This is what causes the shift in
How does the summer solstice occur?
During the solstices, Earth’s tilt is at its highest angle to the plane of its orbit, resulting in one hemisphere receiving more daylight than the other.
(NASA photo/Genna Duberstein)
In scientific terms, the summer solstice represents the Sun’s greatest tilt towards the north of the Earth.
The Sun is directly above the Tropic of Cancer on the northern hemisphere’s summer solstice day. The north pole is inclined about 23.4° towards the Sun, causing the rays to fall exactly above of the Tropic of Cancer, which is nearly the same latitude as the Tropic of Cancer (23°3′ N).
Simply said, when the summer solstice occurs in the northern hemisphere in June, the north pole is as inclined towards the Sun as possible.
The north pole is as close to it as feasible, while the south pole is as far away as possible.
This day also commemorates the start of the Sun’s southern migration, known in India as the Dakshinayan. The Sun will shift position and migrate towards the south pole over the following six months. In six months, the Sun will appear exactly above of the Tropic of Capricorn, whose latitude is 23.5° South, signaling the winter solstice.
