The flowers, the warmth and the scent of rebirth had anticipated it weeks. Today is the day of the spring equinox, during which the lengths of day and night are equal, barring the effects of atmospheric refraction, and the outdoor and allergy season officially begins. Although we tend to believe that the word defines the day when spring begins, the equinox is actually a specific moment. One in which the dividing line between the lighted and dark parts of the Earth passes through the two poles and in which the solar radiation is exactly perpendicular to the equator. An event that only occurs twice a year, at the spring equinox in autumn, due to the tilt of the earth's axis of 23.27 degrees. Without this tilt, sunlight would always be perpendicular to the equator and seasons would not exist.
Day and time of the spring equinox 2024
In 2024, the spring equinox fell at 4:06 a.m. on March 20, thus deviating from March 21, the day commonly considered to be that of the equinox. At that precise moment, at the astronomical North Pole, the sun was rising for the first time after the long Arctic night. The opposite has happened at the South Pole, where the sun will not rise for the next six months, marking the start of the Southern Hemisphere's astronomical autumn. In fact, the equinox has not fallen on March 21 since 2007. This is due to various factors, including the fact that the solar year is not exactly 365 days long, but 365 days and six hours, all of which add up every four years, thus becoming an extra day on leap years. It is predicted that in the coming years the equinox will arrive even earlier, on March 19, and will not return to the 21st until 2044.
Atmospheric refraction of the Sun: Why day and night do not last 12 hours at the equinox
Looking at the sunrise and sunset times in various Italian and global cities on March 20, you will notice that the sun does not rise exactly 12 hours before sunset. In Milan, for example, on March 20, 2024, the sun rose at 6:24 a.m. and set at 6:36 p.m. A gap of 12 minutes. In London, sunrise was at 6am and sunset at 6:14pm, with a slightly greater difference. What is the cause of this difference in the day when day and night should have an equal duration of 12 hours each? To get into the game – explains a Open the doctoral student in astronomy from the University of Padua Nicola Bellucco – is the atmospheric refraction of the sun. Due to this phenomenon, the sun becomes visible a few minutes before it actually rises above the horizon and remains visible for a few minutes after sunset. For this reason, at the spring equinox, sunrise and sunset are never 12 hours apart.
Start of spring: 20 degrees everywhere
If astronomical spring began a few hours ago, meteorological spring has already been underway for some time. The official departure took place on March 1 and, meteorologists warn, the departure brought well-above-average temperatures throughout Italy. Flowers bloomed early, just as animal hibernation ended earlier in many cases. The new spring is now preparing to bring the first heat wave, which in some parts of the country will have an almost summer flavor. Maximum temperatures of 22 degrees are expected in Palermo on March 22. On the same day, Rome will reach 21 degrees, as is usually the case at the end of April. Same temperature expected on March 22 in Milan, in line with the averages for mid-May.
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