Eratosthenes, a Greek philosopher measured the Earth's circumference based on the angle of Sun rays at two different points. Which cities were they?

Correct option is A

The correct answer is (a) Alexandria and Syene.
Eratosthenes, a Greek philosopher and mathematician, measured the Earth's circumference around 240 BCE using the angle of the Sun’s rays at two locations: Alexandria and Syene (modern-day Aswan, Egypt).
Eratosthenes observed that at Syene, the Sun was directly overhead at noon during the summer solstice, casting no shadow. Meanwhile, in Alexandria, located approximately 800 kilometers north of Syene, the Sun cast a shadow at the same time.
By measuring the angle of the shadow in Alexandria and knowing the distance between the two cities, Eratosthenes used basic geometry to calculate the Earth's circumference, arriving at a remarkably accurate estimate for his time.
Information Booster:
● Eratosthenes was one of the first to provide a scientific estimation of the Earth’s size, using observations and geometric principles. ● The angle of the shadow measured in Alexandria was approximately 7.2 degrees, which is about 1/50th of a full circle (360 degrees). ● The distance between Alexandria and Syene was roughly 800 km, which Eratosthenes used to calculate the Earth's circumference as about 40,000 km, close to the modern measurement. ● This method showcased the application of geometry and astronomy in ancient science, reflecting the advanced knowledge of Greek scholars.