The correct answer is option 1, Eratosthenes. Eratosthenes was a Greek mathematician and astronomer who lived in the 3rd century BC. He is credited with being the first person to accurately calculate the circumference of the Earth.

Eratosthenes used a method involving shadows and geometry to measure the Earth`s circumference. He knew that at noon on the summer solstice, the sun would be directly overhead in the Egyptian city of Syene (now Aswan), causing objects to cast no shadows. However, in Alexandria, which was located to the north of Syene, objects would cast a shadow.

Eratosthenes measured the length of the shadow cast by a vertical stick in Alexandria and used the angle of the shadow to calculate the angle between the sun and the zenith. From this, he was able to estimate the circumference of the Earth using simple trigonometry.

His estimate was remarkably accurate, calculating the circumference of the Earth to be around 39,375 kilometers. Although this estimate is slightly off from the modern value of approximately 40,075 kilometers, it was a significant achievement considering the limited tools and technology available at the time.

Therefore, Eratosthenes was the first person to measure the circumference of