Show that the ratio of the Moon’s diameter to the Sun’s diameter is very similar to the ratio of the Moon’s distance from the Earth to the Sun’s distance from the Earth.
The Correct Answer and Explanation is:
To show that the ratio of the Moon’s diameter to the Sun’s diameter is very similar to the ratio of the Moon’s distance from the Earth to the Sun’s distance from the Earth, we can use approximate values for both ratios.
1. Diameter Ratio:
- The diameter of the Moon is about 3,474 km.
- The diameter of the Sun is about 1,391,000 km.
The ratio of the diameters is:Diameter of MoonDiameter of Sun=3,474 km1,391,000 km≈0.00025\frac{\text{Diameter of Moon}}{\text{Diameter of Sun}} = \frac{3,474 \, \text{km}}{1,391,000 \, \text{km}} \approx 0.00025Diameter of SunDiameter of Moon=1,391,000km3,474km≈0.00025
2. Distance Ratio:
- The distance from the Moon to the Earth is about 384,400 km.
- The distance from the Earth to the Sun is about 149.6 million km (or 149,600,000 km).
The ratio of the distances is:Distance from Moon to EarthDistance from Earth to Sun=384,400 km149,600,000 km≈0.00025\frac{\text{Distance from Moon to Earth}}{\text{Distance from Earth to Sun}} = \frac{384,400 \, \text{km}}{149,600,000 \, \text{km}} \approx 0.00025Distance from Earth to SunDistance from Moon to Earth=149,600,000km384,400km≈0.00025
3. Comparison of the Ratios:
Both ratios are approximately equal:3,474 km1,391,000 km≈0.00025\frac{3,474 \, \text{km}}{1,391,000 \, \text{km}} \approx 0.000251,391,000km3,474km≈0.00025384,400 km149,600,000 km≈0.00025\frac{384,400 \, \text{km}}{149,600,000 \, \text{km}} \approx 0.00025149,600,000km384,400km≈0.00025
Explanation:
This similarity in the ratios is why the Moon and the Sun appear to be nearly the same size in the sky, despite the vast difference in their actual sizes and distances from Earth. This phenomenon is known as angular diameter and is responsible for the Moon being able to completely cover the Sun during a total solar eclipse, making the Sun appear to be about the same size as the Moon. The relative sizes and distances create this “optical illusion,” making the two objects appear similar in size when observed from Earth.
