How do you measure the distance to something you cannot reach? Parallax (the shift in an object's position when viewed from two different spots) is one answer. Astronomers use it to measure distances to stars. In a dark room you set up six candles on stools and one distant reference light. You sit in a chair and hold a strip of graph paper at arm's length. Close one eye and record the spacing between each candle and the reference light. Then move to a different chair and repeat. Using the two sets of measurements you calculate how far away each candle is. The method mirrors how astronomers determine stellar distances.