June 21, 2021 is the longest day of the year in most time zones in the Northern Hemisphere. Here are 10 facts you might not know about the summer solstice.
In the northern hemisphere, where there is the longest daylight of the year, the June solstice is also known as the summer solstice. On the other hand, in the southern hemisphere, this day has the shortest daylight of the year and is called the winter solstice.
Some pictures of the summer solstice. Source: Unplash
The solstice occurs twice a year, in June and December. The June Solstice (Summer Solstice) falls around June 21, when the Sun appears directly overhead for people living in the Tropic of Capricorn. The December solstice (winter solstice) falls around December 21, on this day the sun shines perpendicular to the Tropic of Cancer).
Some pictures of the winter solstice. Source: Unplash
The word “sol” (solstice) is derived from the Latin words “sol”, meaning Sun (Sun) and sistere (to stop or stand still). At the summer solstice, the Sun reaches its northernmost point as seen from Earth. At this time, the day’s highest position of the Sun does not move north or south like most other days of the year, but maintains the position of illumination perpendicular to the Tropic of Cancer. It then reversed course and began to continue moving south.
The reverse happens at the winter solstice, when the Sun reaches its southernmost point in the sky, shining perpendicular to the Tropic of Cancer – staying there and then reversing its direction to move north.
Some pictures of the summer solstice. Source: Unlash
…in the whole world. Scientifically, the June Solstice is the exact moment when the Sun shines perpendicular to the Tropic of Cancer. In 2021, this event will take place on June 21 at 10:32 a.m. (Vietnam time).
Although most people think of June 21 as the summer solstice, it can occur anytime between June 21 and June 22. international time), and there will be no June 22 solstice until 2203.
….depending on who you ask. Astronomers and scientists use the summer solstice to mark the start of summer in the northern hemisphere and winter in the southern hemisphere. Meteorologists, on the other hand, suggest that summer begins three weeks earlier, on the first day of June. In many northern cultures, the summer solstice is traditionally considered midsummer (middle of summer). Midsummer Festival takes place during or near the summer solstice in the northern hemisphere in many European countries.
Some pictures of the summer solstice. Source: Unlash
Because the Northern Hemisphere is summer, it’s easy to misunderstand that the distance between Earth and the Sun is shortest during the summer solstice. But the truth is the opposite, this time the Earth is the farthest from the Sun of the year. In fact, the Earth will move towards aphelion (Aphelion) a few weeks after the summer solstice.
The distance from the Earth to the Sun has little effect on the seasons. Instead, it’s caused by the tilt of the Earth’s axis of rotation (about 23.4 degrees), which creates the seasons of the year.
The direction of Earth’s tilt does not change as it orbits the Sun – both hemispheres point in the same direction in space at all times.
What changes as the Earth revolves around the Sun is the position of the two hemispheres relative to the Sun – the Northern Hemisphere faces the Sun at the summer solstice and throughout the summer. In contrast, the southern hemisphere is tilted away from the Sun, so winter is experienced during this time.
Some pictures of the summer solstice. Source: Unlash
Although the summer solstice has the longest day of the year in the northern hemisphere, it is not the first dawn for most places. The day with the first sunrise and the last sunset occurs a few days before and after the summer solstice, respectively. In the southern hemisphere, where the winter solstice is marked, the first sunset and the last sunrise occur a few days before and after the summer solstice, respectively.
The reason is due to the imbalance between the time measured by the clock and the time measured by the sundial.
Indeed, the hottest day of the year in the northern hemisphere usually falls a few weeks or sometimes a few months after the summer solstice, because it takes a long time for the oceans and continents to warm up, allowing temperatures to rise higher. This phenomenon is called seasonal delay.
The summer solstice is the only day of the year when all parts of the Arctic Circle see daylight 24 hours a day. However, due to atmospheric refraction, a midnight sun can occur for several days, before and during the summer solstice in areas within a radius of about 60 miles (97 km) south of the Arctic Circle. The farther north of the Arctic Circle, the more the sun appears at midnight. In the Antarctic Circle, the summer solstice
immersed in the night for 24 hours. As in the Northern Hemisphere, anywhere within the Antarctic Circle sees polar night (the sun does not rise above the horizon) in the days leading up to the summer solstice.
See more astronomical calendar 2021 here: https://deepsky2000.net/lich-cac-su-kien-thien-van-nam-2021/
HAS translation team: Dieu Linh
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