Grab that, now if the heat came with the longest day of the year

The seasons have become an astronomical convention since climate change dominates our lives. Neither the winters are as hard as before nor the summers so bearable, and we still suffer a cyclogenesis in June as we wear short sleeves in November.

The truth is that this year has rained 25% less than usual and the forecast is that the station that starts today is also warmer than normal, so the definition of the situation in Spain is again “meteorological drought ” According to the State Meteorological Agency (AEMET), the average temperature this summer will be between half a degree and a higher degree than usual and the scenario will change drastically next week, when the arrival of “intense heat” is expected. It is not ruled out that a heat wave can occur, although it is still too early to know.

The beginning of the seasons is established by those moments in which the Earth is in certain positions in its orbit around the Sun. In the case of the summer solstice this position occurs at the point of the ecliptic in which the star reaches its most boreal position.

The solstices, therefore, occur because of the imperfection of the Earth, a slight inclination of 23º and 27 minutes. This position, together with the movement of the Sun, means that at the summer solstice the North Pole is closer to the sun than the South Pole. In reality, the Sun is at the height of the Tropic of Cancer, the highest possible position with respect to the Earth.

The scientific explanation is as follows: the duration of a terrestrial orbit is equivalent to something less than 365 and a quarter of terrestrial rotations (that is, of days). With this room the introduction to the Gregorian calendar is explained every four years of an extra day; on February 29 of the leap years. However, there are more corrections to regularize that annual quarter of terrestrial rotation, and that is that the current calendar by which we are governed eliminates three leap days every four centuries.

For that reason, every year the exact moment of the solstice changes, because while the duration of each season, the orbital speed of our planet and all the physical parameters do not change, our calendar does for that quarter of more each year. In this way, every year the time and even the day of entry of the stations changes and the summer solstices always occur between June 20 and 23 due to these adjustments.

On the other hand, the difference in daylight hours between day and night depends on the latitude of the place, so it is zero at the equator and extreme (24 hours) between the polar circles and the poles. Around these dates, in places located above the boreal polar circle occurs the phenomenon called ‘Sun of Midnight’, which is when the star is visible above the horizon during 24 hours a day. In fact, in the days before and after the solstice the position of the Sun does not change too much with respect to the Earth. And hence the name of this phenomenon: solstice (“still sun”, in its literal translation).

Therefore, if we understand by day duration the time that elapses between sunrise and sunset, this June 21 will be the longest day of the year, although wrongly we always associate the longest day and the Shortest night to the celebration of the night of San Juan, next Sunday.

Similarly, one might think that the longest day of the year is also when the Sun rises earlier and sets later, but it is not because the Earth’s orbit around the sun is not circular, but elliptical , and the inclination of the planet in a direction that has nothing to do with the axis of the ellipse. In fact, the day when the Sun came out sooner was the past day 15, while the day it will be later will be the next day 28.

The summer season is longer than others because the Earth moves more slowly along its elliptical orbit, as Kepler’s second law explains, precisely because of this greater distance from the Sun.

At this time of year, although not related to the seasons, there is another curious fact, known as the day of the aphelion, which is when the Sun and Earth are further away from each other in the year. The maximum distance will occur next July 5 with a distance of just over 152 million kilometers between Earth and the Sun, which will be about five million kilometers more than last January 3, when the distance to the Sun reached its annual minimum, which is known as perihelion.

Also, summer is especially rich and attractive from the astronomical point of view. This year, in addition, in summer there will be an eclipse of the Sun on July 2 that will be partially seen in the South Pacific and South America and that will be total in some areas of Argentina and Chile. Also, on the night of the 16th and early morning of July 17 there will be a partial eclipse of the Moon that will be visible in South America, Europe, Africa, Asia and Oceania, so it can also be seen in Spain.

At the beginning of the season that we premiere today, it will also be visible to the naked eye throughout the night Saturn, and also at dusk next to Jupiter and even Mars until the middle of next month. Similarly, Venus will be visible at dawn also until mid-July.

And if there is something striking in summer are the so-called “showers of stars”: the aquarian deltas will reach their maximum frequency around July 30, while the popular perseides or “tears of San Lorenzo” will reach their maximum splendor around the 12th. August; although the full Moon of the 15th of that month will make it difficult to observe the ‘shooting stars’.

With information from El País.