This was Equinox Tuesday, the astronomical event that marks the beginning of autumn in the Northern Hemisphere and the beginning of spring in the Southern Hemisphere.
Some celebrate it by taking a dip in the icy waters of the North Sea, as 800 women and men did in advance and naked this Sunday in Druridge Bay, United Kingdom.
Or those who, at least in non-pandemic times, preferred to welcome the new station by going to archaeological sites that were once ceremonial centers.
If you already knew this, we will tell you other details that you may not know about the equinox.
1. The origin of the term (and its varieties)
The word equinox has its origin in Latin aequinoctium which means “equal night”.
The equinox occurs when the Sun is positioned exactly on the equator, thus light and heat are distributed proportionally in both hemispheres making day and night last (almost) the same, hence its name.
The terms spring and autumn equinox are those that have been used universally historically, but are potentially confusing due to the need to differentiate between the northern and southern hemispheres.
One possible solution is to call them March and September equinox, so as not to have to clarify each time which hemisphere we are talking about.
However, this option is not universal since not all cultures use a solar calendar in which the equinoxes occur each year in the same month.
2. Disagreement between astronomers and climatologists
For astronomers, the equinox on March 20 indicated the beginning of spring in the Northern Hemisphere and autumn in the Southern Hemisphere, and we have practically all embraced that concept.
With the exception of scientists working in climatology, that consider that the station empstarted On March 1.
Astronomers define the seasons on Earth based on the position of our planet relative to the Sun. But scientists who work with climate take the Earth’s temperature cycle as a reference, and not the astronomical position of the Sun.
3. Since when is the equinox spoken?
The phenomenon of the equinoxes has been defined for centuries and centuries.
By setting the Julian calendar in 46 BC, Julius Caesar decided that March 25 would mark the vernal equinox in the northern hemisphere.
This day was already the first of the year in the calendars of Persia and India.
But a problem arose.
Since the Julian year is longer than the tropical year by an average of 11.3 minutes (or one day every 128 years), the dates kept changing; in AD 300 the equinox occurred on March 21 and by 1500 it had advanced to March 11.
This variation prompted Pope Gregory XIII to create the modern Gregorian calendar with which, after various calculations and adjustments, it was established that the equinox would oscillate between March 19 and March 21.
4. Cultural aspects of the equinox
Since the equinoxes are seen as the beginning of spring or fall, picturesque festivals are held all over the world to welcome the new season.
In Bhopal, India, the Holi festival marks the arrival of spring.
However, and without the intention of detracting from the equinox, the celebration of the solstices (June and December) is more striking and symbolic.
5. Effect on satellites and other planets
One effect of the equinox periods is the temporary disruption of communications satellites.
The immense power of the Sun and its extensive spectrum of radiation overload the receiver circuits of ground stations with noise and, depending on the size of the antenna and other factors, temporarily alter or degrade the circuit.
The duration of these effects varies, from a few minutes to an hour.
The equinoxes occur on any planet that has a tilted axis of rotation. A very clear example is Saturn, in which the equinox places the edge of its ring system facing the Sun.
This phenomenon occurs once every 14.7 years on average, and can last for a few weeks before and after the exact equinox.
The most recent for Saturn was on August 11, 2009 and the next will occur on May 6, 2025.
The most recent on Mars was May 22, 2018 and The next one will be this Saturday, March 23.
How it can affect us
The equinox itself has no physical effect on humans, scientists say.
What does seem to affect us is the change of season, but even on this point the experts disagree.
Some people associate the arrival of spring with the benefits of having more hours of sunlight, which translates into greater joy, desire to go out and be more active.
In contrast, the arrival of autumn is associated with a drop in mood, the so-called autumn depression.
But this is not something universal. For other people, spring is synonymous with the so-called spring asthenia, in which energy is lacking and reluctance and lack of motivation weigh heavily.
What group are you in?
It may interest you:
Does the arrival of the cold season really make your hair fall out?
3 ideal energetic cleanses to welcome the autumn equinox
What colors are the most suitable to dye your curly hair during fall
Remember that you can receive notifications from BBC News Mundo. Download the latest version of our app and activate them so you don’t miss out on our best content.
Do you already know our YouTube channel? Subscribe!