EVERYDAY SCIENCE

Detailed explanation-1: -After more than a thousand of years, in 9th century, an Abbasid Caliph ordered the first test of this value. Probably in year 820 AD, the astronomers of Caliph Al-Ma’mun determined the equatorial Earth’s circumference being 20400 miles.

Detailed explanation-2: -The Greek philosopher Aristotle (384-322 B.C.) is credited as the first person to try and calculate the size of the Earth by determining its circumference (the length around the equator) He estimated this distance to be 400, 000 stades (a stadia is a Greek measurement equaling about 600 feet).

Detailed explanation-3: -240 B.C. Eratosthenes Measures the Earth. By around 500 B.C., most ancient Greeks believed that Earth was round, not flat. But they had no idea how big the planet is until about 240 B.C., when Eratosthenes devised a clever method of estimating its circumference.

Detailed explanation-4: -Eratosthenes sent a man to Syene from Alexandria on foot to measure the distance between Alexandria and Syene. Thus, Eratosthenes measured the distance between the two cities is 800 km. He multiplied by 800 km to 50 and calculated that the Earth’s circumference is 40, 000 km.

Detailed explanation-5: -In the second century CE (Common Era) in Alexandria, a philosopher named Claudius Ptolemaeus, or Ptolemy, revised Posidonius’ calculations and set the earth’s circumference at 28, 985 kilometers (18, 000 miles)-an error of nearly 28 percent.