Context: The longest day of the year, for anyone living north of the Equator, is June 21. The day is referred to as the summer solstice, and it occurs when the sun is directly over the Tropic of Cancer, or more specifically right over 23.5 degrees north latitude.
Understanding solstice, equinoxes and seasons?
- Earth’s axis is tilted at 23.5 degrees.
- Earth makes a complete revolution around the sun once every 365 days, following an orbit that is elliptical in shape. This means that the distance between the Earth and Sun varies throughout the year.
- During the first week in January, the Earth is about 1.6 million miles closer to the sun. This is referred to as the perihelion. The aphelion, or the point at which the Earth is about 1.6 million miles farther away from the sun, occurs during the first week in July.
- Since Earth rotates on its axis, the Northern Hemisphere gets more direct sunlight between March and September over the course of a day, which also means people living in the Northern Hemisphere experience summer during this time. The rest of the year, the Southern Hemisphere gets more sunlight.
- During the solstice, the Earth’s axis — around which the planet spins, completing one turn each day — is tilted in a way that the North Pole is tipped towards the Sun and the South Pole is away from it.
- It should be noted that summer solstice for northern and southern hemisphere will be on different dates different.
Seasons are not caused due to this variation in distance rather they are caused due to tilted axis of Earth.
There are two times of the year when the Earth’s axis is tilted neither toward nor away from the sun, resulting in an equal amount of daylight and darkness at all latitudes. These events are referred to as equinoxes and occur near March 21st (Vernal Equinox) and near September 22nd (Autumnal Equinox). At the equator, the sun is directly overhead at noon on the two equinoxes.
June 20th – 22nd – summer solstice in northern hemisphere and winter solstice in southern hemisphere.
December 21st – 22nd – Winter solstice for Northern hemisphere and Summer solstice for Southern hemisphere.
March 20th – 21st – Vernal equinox
September 22nd – 23rd – Autumnal equinox
- The amount of light received by a specific area in the Northern Hemisphere during the summer solstice depends on the latitudinal location of the place. The further north one moves from the equator, the more light one receives during the summer solstice. At the Arctic Circle, the sun does not set during the solstice.
- Summer solstice, however, does not necessarily mean the earliest sunrise or latest sunset. That depends on the latitudinal location of the country.
