Astronomy was very important for the ancient Egyptians who monitored the sky periodically. Astronomers named what they saw in the sky and used their observations to establish the Egyptian calendar. The beginning of the year when the ancient Egyptians announced with the arrival of the waters of the flood of the Nile River; they noticed that the flood comes with the emergence of the star of the Yemeni poetry, the brightest stars of the sky (to the south). The event marked the beginning of the agricultural year in Egypt. That year consisted of 365 days; divided into twelve months, each in thirty days. They have made the remaining five days (days of the poor) days of festivals added to the end of the year. The seasons are divided into three seasons: the flood season, the planting season, and the harvest season. The ancient Egyptians recorded the history of the ascension of all the king of the throne of the country in their documents; starting with the day of the year, season, month and day.
Ancient Egyptians used instruments or detectors to monitor the polar star; then they drew the axis of the north-south line; on the ground, to determine the direction and location of the star. A step that was necessary to determine the right direction for important building projects. One of these devices was called "Mrakht", which could mean "revealing or indicative". It consists of a narrow wooden rod pierced at one end; the astronomer looks through it, to locate the star. There is another device called "Bie in Amy Onout", which means the palm (cranium) of the palm. The device has a slot or slot number 7, cut at the wide end; the opening through which the priest is assigned to track the clocks, so that he can locate the star.
In the Ptolemaic period Claudius Ptolemy, an astronomer, mathematician and geographer, studied the data left by his predecessors; to map the sites of about 1,000 stars. He also made a list of 48 constellations, describing the latitude and longitude of the planet. He believed that Earth was the center of the universe and worked to advance this theory. He also developed the Ptolemaic system to explain why some planets seem to be inversely moving, for periods of time, in their orbits around the earth. I assume that each planet has a rotation in a small circle and another rotation in a larger circle, which is called a "rotary orbit". That theory prevailed for about 1,400 years, until the earth itself turned into orbit around the sun.

In the Ptolemaic period, a calendar was used based on Julian calendar calculations, which were based on the leap year. The Copts in Egypt adopted that calendar; to follow the sun and calculate the days and seasons of agriculture and solar years. The lunar year was also important, used to determine the date of Easter; and other important religious holidays. The Ptolemaic era also witnessed the invention of astrolabe; a navigational tool developed to perfection in the era of succession and the rule of Muslim rulers. Astrolabe played an important role in guiding ships, both for commercial and military purposes.

Tags: Sciences
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