A variety of calendars has arisen historically. The need to measure time is intertwined with beliefs, traditions, and habitat. As a result, systems of reckoning of years arose, which not only begin on different days, but also count the number of days in a year differently.
What happened before the astronomical year
Almost all nations used the moon and the sun as reference systems for time intervals. The most natural unit was the day, which was regularly replaced at night. But there were other periods that could not be overlooked.
Winter, spring, summer and autumn followed one another with the constant rotation of the wheel spokes. It was impossible not to connect them with the phases of the moon and the duration of the sun's stay in the sky. Thousands of years of observing the movements of the heavenly bodies passed, until the concept of the year appeared.
"The sun shines equally for everyone." The once fashionable song explains well why the length of the year in different calendars is almost the same. The difference of several days in everyday life is not fundamental. The reference point is all the more so: some from Jesus, others from Krishna, and still others from earthly deities, kings.
New Year from an astronomical point of view
The science of stars could not come to terms with such diversity. Humanity has become more and more united. A uniform and scientifically based theory of daytime and seasonal periods was needed. This problem was solved by introducing the concept of an astronomical year.
The change of day and night has since been explained by the motion of the Earth around the Sun. The year was called the time of a full turn in the ecliptic, it remains to designate a reference point. Here, scholars did the same as priests and priests. Choose a day. He marked the astronomical new year.
Four points in orbit
The day was chosen arbitrarily, but not by chance. On the trajectory along which our planet moves around the Sun, there are four wonderful points. Two of them are called the equinox days - spring and autumn. Others are days of the winter and summer solstice. When the Earth is in one of them, the maximum difference between the duration of the day and night is achieved.
The choice was not rich, so it was not difficult. In the northern latitudes, this event occurs on December 21 or 22. It turns out that the beginning of the astronomical year is floating. It should be understood that this is not a day, but the moment when the inclination of the axis of rotation of the Earth reaches a maximum value of 23 ° 26´.
It is amazing that people attached great importance to this day in the Neolithic. Ancient buildings such as Stonehenge and Newgrange were oriented so that the observer could see the sun through an axial hole only on the day of the winter solstice.
The astronomical year begins on this day, partly because in almost all cultures it was given the importance of rebirth, of endeavor. Hades - the lord of the underworld, was allowed to come into the world. The Japanese goddess Amaterasu appeared from the cave, symbolizing the birth of a new sun.
Current year events
Like any other, the astronomical calendar for the year lists significant events. There are no holidays and weekends. But there is:
- dates of eclipses of the moon and the sun;
- the ability to observe asteroids, comets and meteor showers;
- favorable time of visibility of the planets, their connection;
- moon cover of stars and planets.
This year, several eclipses await us: three solar and two lunar eclipses. All of them can be observed from the territory of Russia.
The brightest asteroid in 2019 will be Vesta. Its brilliance while it is in the constellation Cetus will be such that it can be observed with the naked eye. Other asteroids - Glitter and Pallas, will be visible only through a telescope.
For astronomy lovers, the calendar provides tables and other reference data on the starry world around us.
Time or distance?
Science, among other varieties, also includes such species of the year as:
- tropical;
- sidereal;
- anomalistic;
- light.
If the first three species are rarely mentioned, then the astronomical light year is familiar to everyone, at least by ear. Fantastic novels contributed to his recognition. Only not everyone knows that this concept does not determine the time period, but the distance.
Stars and planets are too far apart to apply conventional measures of length. 384 thousand kilometers are separating us from the moon, which is close to zero in space scales. The development of astronomy required units of measure corresponding to the vastness of the universe.
When it was possible to accurately measure the speed of light, it became possible to use it to measure gaps in planetary systems. Its main advantage is that it is constant. Therefore, it was agreed that the distance that light travels in 1 year will be the standard of length for astronomers.
Measurement in light units gives: 1.28 seconds to the moon, 8 minutes to the sun, 4.2 years to the nearest star.
Curious facts
The beginning of the astronomical year - the winter solstice, is interesting because:
- it happens 2 times a year;
- in different countries on a different date;
- This is the wrong term.
Features of the winter and summer solstices are explained by the inclination of the earth's axis to the plane of the celestial equator and the fact that they last only a moment. The winter solstice in the Northern Hemisphere is summer for the Southern and vice versa.
As for the incorrectness of the term, it came to us in those days when the Earth was considered the center of the universe. Everything revolved around her: planets, the sun, stars. Therefore, the only moment of immobility of the sun was called the solstice. Copernicus saved us from this error, but the name remains.