What is the leap year? Captain Astro will explain...

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The month of February will end, and it will be a special end because this time, like every 4 years, we will have a February 29. Because we are in a year called leap.

What is the leap year? Captain Astro will explain...

We all know and admit that the Earth revolves around the Sun. But how long exactly? Well, we call time « year ». How many days are there in the year... that's where the big questions will come out, because it's important to make sure that the calendar will give a precised date for when we say a season will arrive on a specific date, when the date arrives we should not see or feel a different season appears. Well, even more dangerous in calculating religious holidays...we know how religious matters are very sensitive down here!

The time it takes for the Earth to rotate around the Sun, astronomers call this the tropical year. It lasts 365.2422 days, This means approximately 365 days, 5 hours, 48 minutes and 45 seconds. So it's shorter than the civil year we're all familiar with: 365.25. Well, there are many astronomical details that explain this, such as the precessional movement and the axis of rotation of our planet...but we will not go into those technical details today.

But long ago, astronomers used to notice small lags in how they count the days of the year. The seasons began to not fall exactly on the days, and Christian, Jewish and Muslim religious holidays began to cause problems as well.

In the Roman period, on Jules Cesar, in the year 45 before J.-C. , for example, there was a year of exactly 365 days, although they used to add 1 month to make the year align with the solar year. But despite this, they found problems in the seasonal calendar, which has a lot of negative impact on the farmers. Therefore, the calendar must be stabilized, because it also has a political importance: Jules Cesar wanted to establish his authority as a good leader for the farmers. He entrusted this mission to an Egyptian astronomer named Sosigen who was working for him. Sosigen added 1 extra day every 4 years. This action will allow the stability of the calendar, to catch up with the days that will allow the new calendar to be the same length as the tropical calendar. Of course, the calendar bears in fact the name of the authority of the time: Jules Cesar. Julian calendar. Well, you know, it could not be different, a king is a king!

Every 4 years, the year that brings this extra day, in the month of February, is called a leap year.

But there is a small detail that Sosigen did not take into account that will start to cause some small problems that another astronomer will correct 1527 years later. It was another Italian astronomer named Luigi Lilio who brought corrections to the calendar. This man was not only an astronomer, he was also a mathematician, physician, physicist. Well, you know...at that time, the young people studied a lot...I wish the young people from our home would also make an effort to study a lot as well...so that the authorities would give them that opportunity too.

What did Luigi Lilio, and all the acolytes of astronomers who participated in this work, do in the Julian calendar that served as a basis at that time? Let's watch together...

The tropical year has 365.2422 days. The Julian year was rounded to 365.25 days. But in reality, there are a lot of digits after the comma, which means that even if you add 0.25 days every 4 years as the Julian calendar did, the rest of the digits after them are still there to add themselves and will end up giving a delay after several centuries. This is what the team of astronomers working on Pope Gregory XIII will ascertain and correct. The Julian year rounded the numbers too much. They will always keep the leap year every 4 years, except for centuries that are divisible by 400. For example, the years 1700, 1800 and 1900 are not leap years (because they are not divisible by 400), but the year 2000 is a leap year (because it is divisible by 400). The year 2024 is naturally a leap year because it is divisible by 4 and by 400. 2028 will also be leap, etc.

What to remember: in the Gregorian calendar, a year has approximately 365.2422 days, it is closer to the tropical year.

This means, it will take more time for the seasonal and calendar lag to appear...but they will appear certainly one day, we are clear about that...we know. Because the calculations show that there is still a residual difference of about 0.0003 days compared to the tropical year, and it will end up not appearing in 3300 years in the future. Well, there, we have time to make another reform on the calendar.

Well, we see, the matter is not more complicated than that, even though I find the word « bissextile » strange. You know, I'm following on social networks, there are people who even think bissextile means 2 sexes, strange....But those of you who have just heard Captain Astro, I'm sure you understand, because we talk about astronomy in our home language , in Haitian.

Don't forget to subscribe, like and share with other people who are interested in the science of astronomy in Haitian. My name is Captain Astro and you can ask me all your questions about astronomy on social networks or call me at +50938407775.

We will meet again for another occasion.

See you soon!