Surveyors are often seen in the middle of the street making careful measurements of angles with their transits, and distances with their steel tapes. For points than can be easily reached, such a survey is convenient. But when the target is inaccessible – a mountain summit or a distant star – known distances can be combined with measured angles to determine a distance or altitude. The method relies on parallax, the way an object appears to move, relative to a more distant background, when viewed from different angles.

Many people dream of becoming millionaires these days. In order to make this dream come true, people play the stock market, play the lottery, and appear on television game shows designed for this purpose. Counting on the stock market requires placing money at risk and playing the lottery involves playing against the odds. And honestly, the television programs place contestants in the risky position of looking foolish by missing an easy question in front of millions of viewers.