Visually, nothing will change drastically, but at 12:33 pm (Brasília time) this Sunday (20) autumn 2022 officially begins. This precise time marking the beginning of the season is an astronomical moment that can be predicted dozens of years in advance.
To say exactly when one season ends and another begins, the now, the end of summer and the beginning of autumn in this year 2022, astronomers' knowledge and study are fundamental. This is what Josina Nascimento, a senior technologist at the National Observatory (ON/MCTI) points out.
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“What defines the seasons is the Earth's position in its orbit around the Sun and the inclination of the Earth's axis in relation to the plane of its orbit. Temperatures, rainfall, sunny days and the entire weather condition depend on a series of other factors, in addition to the season of the year”, explained the technologist.
It might even seem strange to have a precise instant to mark the beginning of the seasons. But Josina Nascimento points out that this happens because the change from one to the other, now from summer to autumn, is associated with specific positions.
Each beginning of the season is associated with an astronomical phenomenon. In summer and winter are the solstices. Already in autumn and spring, the equinoxes. It is these events defined by the Earth's position in its orbit around the Sun and by the inclination of the planet's axis of rotation in relation to the plane of its orbit, which the technologist cited.
“In Astronomy, we look at the movement of the stars from the point of view of the Earth, that is, from the geocentric reference system. Thus, we define the celestial sphere where the celestial equator is the continuation of the terrestrial equator. The path that the Sun takes is called the ecliptic,” he added.
While the southern hemisphere experiences the end of autumn 2022, the northern hemisphere enters spring. At this time, days and nights are approximately the same length. But, as time goes by, the days get shorter and the nights longer, until the winter solstice, scheduled for June 21st in this year of 2022.
“When the Sun is as far away as possible from the celestial equator to the south, it is the summer solstice in the southern hemisphere. Inversely, when the Sun is as far away as possible from the celestial equator to the north, it is the winter solstice in the southern hemisphere”, pleaded the technologist.
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