Then read our article Basics of Astrophysics series absolutely free of cost. From the popular topics such as stars , galaxies , and black holes to the detailed concepts of the subject like the concept of magnitude , the Hertzsprung Russell diagram , redshift , etc. All the articles are given here. Happy reading! I love to write about a plethora of topics concerned with planetary sciences, observational astrophysics, quantum mechanics and atomic physics, along with the advancements taking place in the space industry.
Our idea of a week. The motion of the Sun, Earth, and Moon defines our idea of a year, month, day, and even a week. Moon cycle. The 7 classical planets Image: dribble. Simran Buttar. Search for:. We use cookies on our website to give you the most relevant experience by remembering your preferences and repeat visits. However, you may visit "Cookie Settings" to provide a controlled consent.
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The cookie is used to store the user consent for the cookies in the category "Analytics". Some of the earliest civilizations observed the cosmos and recorded the movements of planets, the Sun and Moon. The Babylonians , who lived in modern-day Iraq, were astute observers and interpreters of the heavens, and it is largely thanks to them that our weeks are seven days long. The reason they adopted the number seven was that they observed seven celestial bodies — the Sun, the Moon, Mercury, Venus, Mars, Jupiter and Saturn.
So, that number held particular significance to them. Other civilizations chose other numbers — like the Egyptians, whose week was 10 days long; or the Romans, whose week lasted eight. The Babylonians divided their lunar months into seven-day weeks, with the final day of the week holding particular religious significance. The day month, or a complete cycle of the Moon, is a bit too large a period of time to manage effectively, and so the Babylonians divided their months into four equal parts of seven.
The number seven is not especially well-suited to coincide with the solar year, or even the months, so it did create a few inconsistencies. However, the Babylonians were such a dominant culture in the Near East, especially in the sixth and seventh centuries B. The seven-day week spread throughout the Near East.
Other cultures in the surrounding areas got on board with the seven-day week, including the Persian empire and the Greeks. Centuries later, when Alexander the Great began to spread Greek culture throughout the Near East as far as India, the concept of the seven-day week spread as well. Scholars think that perhaps India later introduced the seven-day week to China. You have an ancient people in modern-day Iraq to thank.
The reason why we organize our lives around a 7-day week is, quite literally, above our heads. Like many other calendars , today's Gregorian calendar is ultimately based on the phases of the Moon. It takes the Moon around For everyday purposes, this is a fairly long and impractical time span, so it makes sense to break it down into smaller segments.
Enter the Babylonians. This ancient society, who lived in Mesopotamia in what is now Iraq , rounded the Moon cycle down to 28 days and divided this time span into 4 periods of 7 days each, using leap days to stay in sync with the Moon phases in the long run. This 7-day structure is also believed to have ultimately informed a number of popular creation myths, such as the Book of Genesis in the Hebrew and Christian Bibles, which states that God created the world in seven days: six days of work followed by one day of rest.
Avid astronomers and astrologers, the Babylonians developed a kind of horoscope around BCE where each day of the week was assigned to one of the classical planets — the seven non-fixed celestial bodies visible to the naked eye. Some historical sources claim that the connection between the days of the week and the classical planets was introduced later by the ancient Greeks.
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