Source: University of Western Ontario
Published: November 2018
Circulated: May 11, 2020
A “Fermi question” is a question in physics or mathematics which seeks a fast, rough estimate which is either difficult or impossible to measure. It is designed to teach approximation, also known as back-of-the-envelope calculations.
What is the circumference of the Earth?
1. How many time zones do you pass through flying from New York to Los Angeles?
2. How many miles is it, about, over that same distance?
Answer: About 3,000 (4,800 km).
3. How many miles per time zone, on average?
Answer: About 1,000 (1,600 km).
4. How many time zones must there be around the world?
Answer: 24 because there are 24 hours in a day.
5. How many miles around the world?
Answer: 24 time zones x 1,000 miles per time zone = 24,000 miles (38,000 km)
Yes, it is about 24,000 miles around the world. The actual distance is 24,901 miles (40,075 km).