Autumnal Equinox: what is this phenomenon that influences life on Earth?

Summer is ending: this Wednesday (20) the autumn begins in the Southern Hemisphere and, with it, a phenomenon called autumnal equinox – also known as Pound Point🇧🇷 And do you know how it occurs?

To better illustrate this event, the MofWoman interviewed three astronomers who explained exactly how the phenomenon occurs.

Starting with the meaning of this rather strange word, Equinox originates in Latin and comes from the junction of aequuswhich means “equal”, and nox, which means “night”. The reason for this is the fact that on the first day of autumn – or spring – day and night are the same length🇧🇷

“The Autumnal Equinox is that point from which the days become shorter than the night, that is, the corresponding hemisphere will be less bathed in sunlight than the opposite hemisphere. This will last approximately 6 months until the Spring Equinox”, says Professor Rama Teixeirafrom the Institute of Astronomy, Geophysics and Atmospheric Sciences at the University of São Paulo (USP).

There are the Autumn and Spring Equinoxes, which occur in March and September, and the Winter and Summer Solstices, which occur in June and December. As the name implies, in the summer solstices, the day (period of sunshine) lasts longer than the night, and in the winter solstices, the opposite.

Professor Rama adds that, in fact, “these episodes do not happen between seasons, but they are what define the beginning of the seasons from the astronomical point of view that is followed in Brazil”. He explains that, due to the fact that our planet’s rotational axis is not perpendicular to its plane of orbit around the Sun, the hemispheres “are not equally bathed in solar radiation throughout the year”.

At 6:58 pmin Brasilia time, is the exact time that marks the beginning of the Autumnal Equinox this year here in the Southern Hemisphere. In addition to the change of season, the event also affects the remarkable weather, which tends to change with the season. “The typical summer climatic conditions are decreasing, average temperatures are dropping, rainfall is decreasing in southeastern Brazil and the climate is approaching winter conditions (the following season) over the months”, he explains. Roberto Costaprofessor at the Department of Astronomy at USP.

the leap year

A curiosity about these phenomena is that they do not happen annually on the same day. The beginning of autumn, for example, happens on the 20th or 21st of March.

This can be explained by an “error” in our calendar. The actual length of the year is 365 days and 6 hours, about. With that, there is a variation, year after year, of 6 hours. This amount of hours is compensated in what we call “leap year“, which is when we include an extra day in the calendar (the 29th of February).

Professor Emeritus and Doctor of Physics at the Federal University of Rio Grande do Sul (UFRGS) Horacio Alberto Dottori still highlights information about this alternation of days. “The Earth moves in an elliptical orbit (the shape of an ellipse, almost oval) and when it is closer to the Sun it moves faster. This also causes the Northern Hemisphere’s spring and summer to be slightly longer than those of the Southern Hemisphere.”

Google Doodle Marks the Autumnal Equinox

O Googlekeeping an eye on the change of seasons, aired a doodle on the home page, so we can get in the mood. With a very cute illustration, our planet is snuggled under a dry leaf.

Pretty cool, isn’t it? And you, are you happy with the arrival of autumn?