In a camera obscura, which is a Latin word meaning ‘dark chamber’, light enters a dark room or a closed box through a small hole. If the hole was small enough, a very faint inverted image would be seen on the opposite wall. At the end of the 13th century, astronomers made use of this to observe the sun. In this way they could study its hot surface, without having to look directly at it. Today, we buy a special pair of goggles to look at the sun.