Back-of-the-Envelope Calculations: The Right Eye of the Man in the Moon
The "right eye" of the Man in the Moon is really Mare Imbrium, the central portion of a gigantic multi-ring basin formed by a colossal meteorite impact several billion years ago. Which of the following is approximately the same size as Mare Imbrium? Choose from the Pacific Ocean, the North Atlantic Ocean, Australia, Texas, and New York State.
About the size of Texas. The main part of the Imbrium Basin is about 1150 km across, not even close to being the size of any of the terrestrial oceans. Many people visualize the Moon as being much larger than it really is!
References and Resources
This SERC page describes the use of Back of the Envelope Calculations
The Back of the Envelope : This page outlines one of the essays in the book "Programming Pearls" (ISBN 0-201-65788-0). The book is written for computer science faculty and students, but this portion speaks very well to back of the envelope calculations in general.