When I was a small child, I had a friend who was born on February 29, a “jump”, which we add this month every four years. I remember how we teased him, saying that he was only three years old. I lost contact with him for many years, but I assume that by now he is quite tired of a joke.
And here we are again on the threshold of our four -year exercise during the service life: Jumping 2024 is almost on us. A handful of traditions was associated with her; One of them believed that this was the only acceptable day for – GASP! Some people like to treat this day as a free day that gives them time to catch up with something that they have laid out for a long time.
I think that this is a pretty good idea, because, in the end, to catch up is what LEAP DAY is an astronomically, that is.
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There are two main units of time that we use, which are based on astronomical events. One of them is the day, the duration of the time that it is required to rotate once on its axis. Another is the year, the time required for the Earth to complete the orbit of the sun. Although this seems simple, these two units are actually quite complicated. For example, the earth rotates once in relation to what? You need some reference structure with which you can measure this movement.
For our daily life, we use the Sun. The time that is required for the Sun in the south to set and then rise again and achieve the southern meridian is one sunny day, which we define as 24 hours or 86,400 seconds. This is actually keep in mind The sunny day, which uses the center of the solar disk as a reference point and is on average every day of the year. The use of the average value is useful for timing, because the earth moves at different speeds at different points of its orbit, which changes the exact length of any particular day.
There are several different ways to measure the length of the year. Our current calendar uses a tropical year, time from the spring equinox to the spring equinox, in order to take into account subtle effects, such as precessionOtherwise, the field of equinox will slowly change for many years, and ultimately in July the December solstice will occur, which will be terribly confusing.
The tropical year is 365.2422 average sunny day in lengthThe field since the rotation of the Earth and the orbital period are in no way connected, they do not separate evenly. We have 0.2422 remaining, and this is the key to jumping days.
If we begin to measure the day and year at the same moment, at the end of one year the Earth will spin 365 times, plus an additional 0.242 paths, when the New Year begins. Four years later, this is up to 0.9688 days – very all day. We created an additional day of the year!
This was known even by ancient peoples, and when Julius Caesar decided to change the basis of the Roman calendar using the moon in the sun, he also decided that every fourth year an additional day would be added to preserve everything to synchronize. Congratulations! Happy jumping day! Technically, this is called an intercalar day, which is added to the calendar for its synchronization.
With the exception of mathematics, it will not work. Adding all day every four years, we add too much: after four years we have only 0.9688 days left, not 1.0 days. This difference is 0.0312 days or about 45 minutes. This means that every four years we still have about three quarters of an hour to take into account. Over time, this accumulates, and the calendar will be disconnected again.
Enter Pope Gregori XIII, who again reformed the calendar in 1582. He decided that every 100th year (to make it simple, the years ending in 00) will be No Be jump, so the day of jumping will not be added. 25 temporal days take place in the century, so this method Removes 25 x 0.0312 = 0.78 day, and in the long term the calendar is a little better, but again, not quite.
Using this algorithm, every 100 years the calendar will operate 1 – 0.78 = 0.22 days. This also adds! Thus, as part of his papal bull, Pope Gregory XIII also stated that every 400th year will again acquire a jump. By that time, there is an additional 4 x 0.22 = 0.88 days, so adding one day to catch up with an irritably non -integral ratio of the Earth.
This is the rule that we use now. Every fourth year, that is, every year whose number is evenly divided by 4 is a temporal year, and it is provided an additional day, that is, with the exception of every 100 years, when we pass the temporal day, except Every 400 years, when we overestimate the rule and add a jump again. Thus, 1700, 1800 and 1900 years were not jumping. 2000 occurred because, although it is divided evenly into 100, it is also evenly divided into 400. It will not be a medical year, but 2400 will be and so on.
This actually brings us closer to synchronization. I sometimes wondered, however, why Pope Gregory XIII did not use a period of time every 500 years instead of 400. It would be better because the remaining amount of 100 years is closer to one fifth day. But here we are.
From this, however, our current rules still leave the calendar a little. We add all day every 400 years, but this is too much for 1 – 0.88 = 0.12 days. If we wanted, we could again change the rule and say that every 3200 years we Not Make the old year this year. Why 3200? Well, 8 x 0.12 = 0.96, so that we can skip a jump with every eighth 400-year cycle, which is every 3200 years. This will mean that the year and day will be disconnected only for 0.04 days – in just an hour – every three millennia, which has suffered quite enough.
As usual, when working with astronomy and numbers and calendar, things seem simple – so far they are not.
One way or another, a happy jumping day, and if you have something, that you are postponing for four years, now now is a good time to get to this. And for my old friend Ted, if you happen there: Happy Birthday!
