Solar System Model
A reasonable width for a living room is 20 feet. If your living room is 20 feet wide and you erect a scale model of the solar system, placing the sun against one wall of your living room, and the earth against the other wall, how large would the sun and the earth each be in diameter?

Answer:

Two inches, and two one hundredths of an inch, respectively. (About the size of a plum and a tiny speck.)

Calculation: The diameter of the sun is 800,000 miles. The diameter of the earth is 8000 miles. The distance from the Earth to the Sun is 93,000,000 miles. If we change these numbers to feet we would have a scale model that would be 5280 (the number of feet in a mile) to 1. The relationship of 20 feet to 93,000,000 feet is 20/93,000,000 = 2.15 x 10^-7. Multiplying this by 800,000 gives us .172 feet for the diameter of the sun, and .00172 feet for the diameter of the earth. Multiplying by 12, we get 2 inches for the diameter of the sun, and two one-hundredths inches for the diameter of the earth. The sun, therefore would be about the size of a plum, and the earth would be a tiny little speck on the wall that you would have to look very carefully to see (assuming you have very good eyesight).