How did they calculate the circumference of the Earth?

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.

Did Ptolemy measure the Earth?

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.

Is Eratosthenes’s method of determining the circumference of the Earth logical and reasonable?

Eratosthenes reasoned that the ratio of the angular difference in the shadows to the number of degrees in a circle (360°) must equal the ratio of the distance to the circumference of the Earth. The resulting estimate, about 25,000 miles (40,234 km), is astonishingly accurate.

What is the exact circumference of the earth?

In 200 B.C. Eratosthenes estimated Earth’s circumference at about 46,250 kilometers (28,735 miles). Today we know our planet’s circumference is roughly 40,000 kilometers (24,850 miles).

How do we measure the size of the Earth?

The angle Eratosthenes measured at Alexandria was 7.2 degrees, or a fiftieth of a circle. So, he multiplied the distance between Syene and Alexandria by 50 to get the size of the Earth.

Why was determining the circumference of the earth so important?

Measurement of Earth’s circumference has been important to navigation since ancient times. The first known scientific measurement and calculation was done by Eratosthenes, who achieved a great degree of precision in his computation.

How did Eratosthenes calculate the Earth’s circumference?

Eratosthenes hired a man to pace the distance between the two cities and learned they were 5,000 stadia apart, which is about 800 kilometers. He could then use simple proportions to find the Earth’s circumference — 7.2 degrees is 1/50 of 360 degrees, so 800 times 50 equals 40,000 kilometers.

Who among the following had calculated the circumference of the earth?

Eratosthenes. The measure of Earth’s circumference is the most famous among the results obtained by Eratosthenes, who estimated that the meridian has a length of 252,000 stadia, with an error on the real value between -2.4\% and +0.8\% (assuming a value for the stadion between 155 and 160 metres).

Why did Eratosthenes measure the Earth?

Eratosthenes erected a pole in Alexandria, and on the summer solstice he observed that it cast a shadow, proving that the Sun was not directly overhead but slightly south. Recognizing the curvature of the Earth and knowing the distance between the two cities enabled Eratosthenes to calculate the planet’s circumference.

How did Eratosthenes calculate the earth’s circumference?

How big was the Earth according to Ptolemy?

Ptolemy elected to use the circumference of the earth proposed by Poseidonius rather than the accurate size determined by Eratosthenes (fl. 240-200 B.C.). Eratosthenes calculated it to be (in modern equivalents) 25,000 miles, which is very close to its actual circumference of 24,902 miles.

Did Ptolemy adopt the heliocentric or geocentric theory?

In his thinking Ptolemy adopted the geocentric universe propounded by Aristotle (384-322 B.C.) and others, rather than the heliocentric universe of Aristarchus of Samos (d. 230 B.C.). This is curious, in light of his professed thesis of adopting the simplest explanation possible for any phenomenon.

Who calculated the circumference of the Earth using a gnomon?

Eratosthenes Of Cyrene Calculated The Circumference Of The Earth Using A Gnomon And Counting How Long A Camel Walked In A Day Born in Cyrene which is now in Libya in North Africa, Eratosthenes Of Cyrene (276 BC – c. 195/194 BC) was a Greek mathematician, geographer, astronomer and historian.

What is the circumference of the Earth?

The later astronomer Poseidonius had calculated the circumference to be approximately 18,000 miles, about three-fourths its true measure. This smaller figure was adopted by Ptolemy. Hipparchus divided the equator into 360 degrees, a figure accepted by Ptolemy, whose world map covered the half of the world that he knew.