Question

The Earth's circumference is nearly:

• A. 30075 km
• B. 50075 km
• C. 40075 km
• D. 60075 km

Hint:

Earth’s average circumference ≈ 40,075 km (equator). Check context for variations.

Answer 1

The Correct Option is C

To determine the Earth's circumference, we need to understand how this fundamental measurement is calculated and verified.

1. Historical Context:
The first accurate calculation of Earth's circumference was made by Eratosthenes in 240 BCE using simple geometry and observations of sun angles at different locations. Modern measurements confirm his remarkable accuracy.

2. Modern Measurement Methods:
Today, we determine Earth's dimensions through:
- Satellite geodesy measurements
- GPS technology
- Very Long Baseline Interferometry (VLBI)
- Laser ranging to satellites

3. Official Measurements:
According to NASA and the International Astronomical Union:
- Equatorial circumference: 40,075 km
- Polar circumference: 40,008 km
The slight difference is due to Earth's oblate spheroid shape (wider at the equator).

4. Why 40,075 km is Correct:
This value represents:
- The most commonly cited average circumference
- The equatorial measurement (longest circumference)
- The figure used in most educational and scientific references

5. Practical Demonstration:
This circumference means:
- A plane flying at 800 km/h would take 50 hours to circle the equator
- The speed of Earth's rotation at the equator is about 1,670 km/h

Final Answer:
The Earth's circumference is nearly $\boxed{40075\ \text{km}}$.