SUMMER. The first day of summer 2023 is very precisely for this Wednesday, June 21. This date of the 2023 summer solstice also marks, once again, the longest day of the year. What time does the phenomenon occur and how to explain it?
[Updated June 21, 2023 8:48 AM] This Wednesday, June 21, 4:57 PM marks the summer solstice, an astronomical phenomenon that marks the beginning of summer. The solstice, in general, whether winter or summer, occurs twice a year, 6 months apart, when the position of the sun reaches its maximum distance from the equator. The summer solstice thus corresponds to the longest day of the year in our northern hemisphere, with 16 hours 09 hours in total, while the winter solstice, which takes place between December 20 and 22, marks here on the shortest day of the year. Conversely, in the southern hemisphere, the longest day coupled with the shortest night, on the contrary, takes place at the end of December.
The summer solstice can, depending on the year, occur between June 19 and 22. In 2016 and 2020, the summer solstice did not occur on June 21 but on June 20. As the Sciences et Avenir website explains, it happened 36 times during the 20th century that this solstice happened on June 22 and 64 times on June 21. During the 21st century, this event will occur 47 times on June 20, and the next time will be on Thursday, June 20, 2024.
After the summer solstice, the day of June 22 will be just as long in our hemisphere. From June 23, therefore, the duration of sunlight will begin to decline to reach the shortest day of the year at the winter solstice, which corresponds to approximately eight hours of light. If the date of the summer solstice corresponds to the date of the beginning of the astronomical summer, the meteorological summer begins on June 1st. Artificially programmed by scientists on June 1 of each year, the “meteorological” summer allows sky experts to carry out their calculations more easily. Speaking of weather, what does this first day of summer have in store for us when the last few days have been marked by the heat wave in several departments of France? What time does the summer solstice occur and how long is the day? And how to explain this phenomenon that does not always fall on June 21? All your questions answered below:
In our northern hemisphere, the summer solstice, which marks the first day of the summer season on our calendar, will occur on Wednesday, June 21, 2023, at 4:57 p.m. according to figures provided by the Institute of Celestial Mechanics and Computation. ephemerides (IMCCE).
How do you define the summer solstice? It corresponds to the time of year when the path of the Sun, as seen from Earth, reaches its northern (in the northern hemisphere) or southern (in the southern hemisphere) maximum. In other words, during the summer solstice, at our latitudes, the Sun “passes” its zenith, at the Tropic of Cancer. In reality, it is not a movement of our star that produces this phenomenon, but the revolution of the Earth around the Sun. This is because the axis of our planet is tilted 23 degrees relative to the plane of the ecliptic, which is the plane on which the Earth moves relative to the sun. We therefore have the illusion of the Sun moving across the sky. But a good diagram is sometimes worth more than a long speech…
Concretely, this phenomenon has many consequences that can easily be seen with the naked eye (and with a clock in hand). It is at the time of the solstice that the sun passes highest in the sky at the moment of its zenith: the shadows shorten to the maximum. The star can then pass, for example, at an altitude of 65° relative to the horizon. By way of comparison, at the time of the winter solstice, the sun rises only 18° above the horizon. Another consequence: this is when the star rises and sets most northerly (northeast in the morning, northwest in the evening).
On Wednesday, June 21, 2023, the day of the summer solstice but also the longest day, the sun will set at 9:57 p.m. in Paris, after having illuminated the capital for 4:09 p.m. -Ouest, in France, the inhabitants of the department of Finistère will be the most spoiled by this long day. In Brest, the star will set squarely at 10:22 p.m. In Rennes, the Sun will set at 10:10 p.m. In Metz, he will disappear at 9:43 p.m. In Toulouse, the star will set at 9:39 p.m. In Lyon, the sun will set at 9:34 p.m. In Marseille, the sun will bow out at 9:22 p.m. on June 21. To find out more about sunset times by city, visit the specialist site Kalendrier.com.
The most obvious consequence of the summer solstice phenomenon is the maximum lengthening of visible day length. In Paris, this year 2023, the duration between sunrise and sunset will reach 16 hours 9 minutes, its annual maximum. The star will appear in the east from 5:48 a.m. to disappear at 9:57 p.m. From the next day, the length of the day will begin to gradually decrease. First imperceptibly, then faster and faster until the autumnal equinox. The Latin etymology of the word solstice translates this progression: sol (sun) and sistere (to stop) remind us that it is during this period that the length of the day changes the least quickly.
If the length of the day reaches its maximum on the occasion of the solstice, it is not the same everywhere. The closer you get to the Arctic Circle, the more it increases. In northern Norway, the Sun hardly ever goes below the horizon: there is no night to speak of. There, the Sun stops setting altogether from the summer solstice at the level of the Arctic Circle. In the southern hemisphere, the phenomenon is reversed. At the time of the summer solstice in our lands, Antarctica is plunged into darkness. Be careful though: if it is theoretically at the time of the summer solstice that the sun rises the earliest in the morning or sets the latest in the evening, this principle is not always rigorously exact. In question, the slightly elliptical course of the Earth around the Sun, marked by accelerations and decelerations. The irregular shape of our planet also plays a role.
This is simply explained by the Gregorian calendar, as explained by the Numerama site. The latter was adopted in 1582 and provides that a year lasts 365 days, except for leap years which occur every four years and during which there are 366 days with the addition of a February 29. In fact, more than 365 days are needed for the Earth to make one revolution around the Sun, it takes precisely 365 days, 5 hours and 48 minutes. The decision to include leap years in the calendar was made to erase the gap between the length of a year and the time of revolution. And this explains the shift of the summer solstices.
While the phenomenon also falls on the day of the music festival, the summer solstice traditionally gives rise to the great fire festival of Saint John, which is then celebrated every June 24. This festival honors the summer season by drawing inspiration from the worship of the sun during Antiquity. An initially pagan practice of harvest celebration taken up by the Catholic Church, which Christianized it to set it up as a festival of light, in particular thanks to the famous fires of Saint John lit at nightfall.
In our northern hemisphere, the summer solstice is the longest day of the year. The time span between sunrise and sunset can exceed 16 hours, compared to just 8 hours at the end of December at the time of the winter solstice. The phenomenon arises from the Earth’s natural tilt relative to the plane on which it revolves around the Sun. Without this shift, the seasons as we know them on our planet would not exist! In our regions, the summer solstice therefore marks the beginning of the summer season. Midway between the spring and fall equinoxes, when night and day are exactly the same length. What makes it a very special date.
The date of the summer solstice is generally the first piece of information that we seek to know among gardeners, lovers of the warmest days or simply among those who like to be fixed on the ball of the seasons. On this point, it’s relatively simple: the summer solstice usually occurs on June 21st. But beware, there are still exceptions. In 2016, for example, it was scheduled for Monday, June 20 at 22:34 GMT. France living at GMT 2 since the time change, it did take place, in France anyway, on June 21 at 00:34.
But it can happen, as in 2008, 2012 or 2020, that the summer solstice occurs on June 20. This phenomenon can also occur on June 22, as it did in 1975 (the next occurrence will be in…2203). Rarer still, the summer solstice can finally arrive on June 19. It will be in 2488. Because the exact moment of the solstice changes every year. It is a question of correctly evaluating the trajectory of the Earth in relation to the Sun, and of our ability to model our time system and our calendar on these astronomical movements. Indeed, the calendar year (365 days) does not correspond to the tropical year, that is to say the exact duration that our star takes to revolve around our star (365 days, 5 hours, 48 ??minutes and 45 seconds). If this “shift” is corrected by leap years, the elliptical trajectory of the Earth also plays a role in shifting the solstice each year.
Here are the dates on which the summer solstices will occur in the following years:
