From Enrico Fermi to Bill Bennett

The calculation suggests that the $8 million estimate of his losses may be high or that the machines had lower payouts or that he was even more enamored of gambling than previously thought. Given the games he played and only his documented losses, however, Bennett's claim that he gambled occasionally and more or less broke even is laughably innumerate. His Book of Virtues should have contained a section on arithmetic rectitude.

In summary, doing a few back-of-the-envelope calculations can sometimes be quite revealing, not just in physics, but in journalism as well.

Answer: We need to find out how much land area there is on Earth and what the population is. The Earth is a sphere whose radius is about 4,000 miles. Since the formula for the surface area of a sphere is 4pi*r^2, we find that the earth has a surface area of about 200 million square miles. There are 5,280 feet per mile so there are 5280^2 square feet per square mile, which means that 200 million square miles contains about 5.6 x 10^15 square feet. Multiplying this by .3 (since only 30 percent of the Earth's surface is land) yields about 1.7 x 10^15 of land surface area. Dividing this by approximately 6 billion humans gives each of us about 280,000 square feet to call our own. Taking the square root of this figure reveals that we each would have a square a bit more than 500 feet on a side. Of course, most of these parcels would be inhospitable.

Professor of mathematics at Temple University and adjunct professor of journalism at Columbia University, John Allen Paulos is the author of several best-selling books, including Innumeracy, and the just released A Mathematician Plays the Stock Market. His Who’s Counting? column on ABCNEWS.com appears the first weekend of every month.

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