Nature News: When Galileo Galilei used a new invention called the telescope to watch the heavens, he revolutionized astronomy. But his estimates of the distances to the stars were thousand of times too short. A scientist has now taken a closer look at Galileo's seventeenth century results in an attempt to explain why the estimates were so far off the mark1. Christopher Graney, a physicist at Jefferson Community College in Louisville, Kentucky, argues in a paper posted to the preprint server arXiv that Galileo was tricked by a phenomenon that was only really understood two centuries later — diffraction.