Historians consider astronomy to be the world’s first science. Since ancient Babylonia in 1600 BCE, people have mapped the heavens, tracked eclipses, and developed calendars. Until the early 17th century, scientists used measurement devices with the naked eye to observe and track the movement of planets and stars. In 1572, Danish astronomer Tycho Brahe discovered a new star, challenging the prevailing notion that the universe was unchanging. Throughout the following century, refracting telescopes were invented and improved, and in the late 17th century, developed into the more efficient reflecting telescope, through the work of Sir Isaac Newton. Optical telescopes were used in the significant astronomical accomplishments of the 18th and 19th centuries, such as mapping the Milky Way and the surface of Mars. In the 20th century, radio telescopes were developed to survey the universe beyond the Milky Way; by mapping cosmic radiation, astronomers have garnered much evidence for the Big Bang Theory to explain the origins of the universe. With LIGO, which maps gravitational waves caused by immense distortions in space-time, such as black holes, yet more answers are on the horizon.