key term - Eratosthenes

Definition

Eratosthenes was an ancient Greek mathematician, astronomer, and geographer who is best known for his remarkably accurate calculation of the circumference of the Earth. He is considered one of the most influential scholars of the Hellenistic period, making significant contributions to various fields of study.

5 Must Know Facts For Your Next Test

1. Eratosthenes calculated the circumference of the Earth by measuring the difference in the angle of the sun's rays between two locations on the same meridian, separated by a known distance.
2. He used the city of Syene (modern-day Aswan, Egypt) and the city of Alexandria as his two observation points, and determined that the difference in the sun's angle was about 7.2 degrees.
3. Eratosthenes then used this angle difference and the known distance between Syene and Alexandria to calculate the circumference of the Earth, arriving at an estimate that was remarkably close to the actual value.
4. His calculation of the Earth's circumference was approximately 250,000 stadia, which translates to about 24,900 miles, very close to the modern estimate of 24,901 miles.
5. Eratosthenes' method of calculating the Earth's circumference is considered a significant achievement in the history of science, as it demonstrated the ability of ancient Greek scholars to make precise astronomical observations and perform complex mathematical calculations.

Review Questions

• Explain how Eratosthenes used the difference in the sun's angle between two locations to calculate the circumference of the Earth.
  • Eratosthenes observed that the sun's rays were perpendicular to the ground in Syene (modern-day Aswan, Egypt) on the summer solstice, indicating that the sun was directly overhead. However, in the city of Alexandria, located on the same meridian but about 500 miles to the north, the sun's rays were not perpendicular, and the angle between the sun's rays and the ground was about 7.2 degrees. Eratosthenes then used this angle difference and the known distance between the two cities to calculate the circumference of the Earth, arriving at an estimate that was remarkably close to the actual value.
• Discuss the significance of Eratosthenes' calculation of the Earth's circumference and how it challenged the prevailing geocentric model of the universe.
  • Eratosthenes' calculation of the Earth's circumference was a significant achievement in the history of science, as it demonstrated the ability of ancient Greek scholars to make precise astronomical observations and perform complex mathematical calculations. His method of using the difference in the sun's angle between two locations on the same meridian to determine the Earth's size challenged the prevailing geocentric model of the universe, which placed the Earth at the center of the cosmos. Eratosthenes' work provided evidence that the Earth was a sphere, rather than a flat plane, and his remarkably accurate estimate of the Earth's circumference laid the groundwork for future advancements in geography, astronomy, and our understanding of the world.
• Analyze the impact of Eratosthenes' contributions to the field of ancient astronomy and how his methods and findings influenced the development of scientific thought in the Hellenistic period.
  • Eratosthenes' contributions to ancient astronomy were truly groundbreaking and had a profound impact on the development of scientific thought in the Hellenistic period. His calculation of the Earth's circumference, which was remarkably accurate, demonstrated the power of systematic observation, mathematical reasoning, and the scientific method. Eratosthenes' work challenged the prevailing geocentric model of the universe and provided evidence that the Earth was a sphere, rather than a flat plane. This laid the foundation for future advancements in geography, cartography, and our understanding of the cosmos. Eratosthenes' methods, which involved making precise measurements, analyzing data, and drawing logical conclusions, set a precedent for the rigorous, empirical approach that would come to define the scientific revolution. His achievements in astronomy, mathematics, and geography solidified his reputation as one of the most influential scholars of the Hellenistic era and a true pioneer of scientific inquiry.

Related terms

Geocentric Model:

The geocentric model is an astronomical model in which the Earth is at the center of the universe, with all other celestial bodies orbiting around it.

Spherical Earth: The concept that the Earth is a sphere, rather than a flat plane, which was widely accepted in the ancient Greek world.

Meridian:

A meridian is an imaginary line on the surface of the Earth that runs from the North Pole to the South Pole, passing through a specific location.