When we think about astronomy, there arise some questions such as, what is the role of astronomy in everyday life, and what was its role Among ancient civilizations? Well, let’s discuss some facts related to it.
Imagine 50,000 years ago, to keep agricultural timekeeping and the provision of crops for growing societies, people wanted to keep track of time. They used the sky to keep time and to track the seasonal cycle and also they observed the solar and lunar cycle. As the most prominent objects in the sky, they monitored the phases of both the sun and the moon. Also, they noticed the strange juxtapositions of both. What would they have made using these phenomena? They found out that the sky was a map, a calendar, a clock, and also a source of myth and legend.
Among these, the calendar is a topic where ancient astronomical practices meet the modern world. So, let’s look at calendars or timekeeping, and see how ancient astronomical practices are deeply embedded in our modern life. Astronomy still lives with us every day on our calendar.
As we know, there are four major subdivisions of time in a year where three of them are astronomical. The days – the rotation period of the Earth, the year – the orbital period of the Earth around the Sun, and the month – is a lunar cycle or the orbital period of the moon around the Earth. The only division of time that’s not naturally or obviously astronomical is the week.
Actually, the week did not have the same division of time (ranges from 4-10 days) across different cultures all around the world. The classic week of the modern calendar, that is 7 days, starts with the Babylonians and the Egyptians. The names of the days of the week are quite obviously the names of seven moving objects in the night and daytime sky, the Sun, the Moon, and the five naked-eye visible planets; Mercury, Venus, Mars, Jupiter, and Saturn in Roman language like French, or Spanish, or Italian, or Portuguese. So, the week is also an astronomical relic.
ORIGIN OF MODERN CALENDAR
Our calendar traces back to the ancient Romans in the seventh century BC. Rome was a set of warring tribes, quite militaristic, that dominated their region, and occasionally would do battle with other tribes North of the Alps. They needed a calendar. So, the ancient Romans started their year when the snow melted enough that they could raise an army and do battle. They were following roughly a lunar calendar and they only needed 10 months in their year and reset it again.
They didn’t count the time in the dark winter. That’s why the last four months of our year are named after the Roman words for seven, eight, nine, and ten. This calendar was used for a few centuries. Then the Emperor Promiscuous and other Emperors decided to add a couple of light months at the front end, giving 12 months. Thus, the year their lunar calendar consisted of 12 lunar cycles, that is 354 days. That is, the world’s first calendars were lunar calendars!
The actual problem with the lunar calendar was, it was not good for knowing about seasons. Because it goes out of sync by 11 days a year as compared to the solar cycle. The Romans needed their calendar to be season reliable. Thus the solar calendar was introduced.
The solar calendar – the time taken by the Earth to go around one complete orbit of the Sun. So, the calendar moves towards 365 days and a quarter day. It consisted of 12 months. They had a pretty strictly alternating sequence of 30 and 31 days among the later months. As a relic, February was the short month, the unlucky month. The last months of the year named after numbers, and the first months of the year named after primordial gods such as Maya for May, Janus for January, the god of doorways and beginnings etc.
Do you wonder, while we’re using the knuckles of our hand to figure out which days have 30 and 31 days, July and August have the same knuckle and have 31 days?
During the time of Julius Caesar, he presided over one of the most extensive and powerful regimes ever known in world history. For regulating this large empire and for administrative purposes he needed a good calendar. Caesar recognized that the old Roman calendar was not up to good for this. So, he put forward the Julian calendar. The main thing Caesar added in calendars was a leap year, that is an extra day in every fourth year, giving a calendar with a mean length of 365.25 days. That’s close to a solar cycle. Also, he decided to take the first unnamed month in sequence and name it after himself, hence July.
After Caesar, Augustus didn’t make any innovation to the calendar. But due to his large ego, he named the next unnamed month after himself, hence August. Also, since Julius Caesar’s month was longer than his month, he added an extra day to his month, and hence messed up the pattern.
The Julian calendar is quite successful. However, the exact time that the Earth to rotate around the sun is 100th of a day different from 365.25. It’s actually 365.24199. So, Julian’s calendar gets out of sync by the 100th of a day per year. After a century, that’s a day. By medieval times, the Julian calendar was off by a week or so, and agricultural planting cycles were starting to be affected. So, in the era of the Italian Renaissance, the last adjustment to the modern calendar was made by the Popes. Pope Gregory recognized the problem with the calendar. He with the help of some astronomers made careful measurements of the length of the day and the year and made a final adjustment to our calendars. The Gregorian calendar only off by less than a ten-thousandth of a day per year, and therefore will be good for tens of millennia. This leads to the rise of the modern calendar.
An interesting sidelight on this is that the Protestant countries after the Reformation, did not follow the Pope’s guidance on the calendar, so they resisted to make the adjustment that Gregory made for another 150 or 200 years. In France, this happened quickly. But in England and the United States where Protestants were dominant, the calendar was not adjusted until the gap between the solar year and the calendar year had approached 13 days. So, due to this, when they decided to follow the Gregorian calendar on one day, April fourth turned into April 15th. Benjamin Franklin wrote in Poor Richard’s Almanack, Do not fret over the loss of those days”. But people worried that they’d be ripped off rent, and bad things would happen although the Earth continued in its orbit. Thus, the French created the April Fool holiday to mock the Americans and the British for taking so long to get the right calendar. So, calendars have been part of our culture for a long time.
Calendars and their history gives us a quirky and entertaining embedding of astronomy in modern culture. According to a recent survey, there are about forty calendars used in the world today. Most of them are astronomical. The common theme of the calendar is the desire to organize units of time to satisfy the needs and preoccupations of society. Also, this process of organization provides a sense of understanding and controlling time itself. Thus our calendars serve as a link between humankind and the cosmos or calendars are the topics where ancient astronomy meets the modern world.
Courtesy: chris impey ( British astronomer, educator, and author)
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