As humans began to learn more about the Moon and about science, some intriguing theories about the Moon's influence entered the conversation. Many people believed celestial objects affected personality, health, and disease-for example, they thought that the Moon brought fever, and even abrupt psychological changes. The words "lunatic," "lunacy," and "loony" all trace their origins back to "Luna," the Latin word for moon.                                                                                                                                                                                                                                                                                                                                                                                                                                                               Then there's the folklore, like the tale of a man who morphs into a werewolf when bathed in the light of the full Moon, wrecking havoc on society. Scientists are still investigating whether humans and animal behaviors do in fact correlate with lunar cycles. Although, as any scientist knows, correlation does not mean causation.                                                                                                                                                                                                                                                                                                                                                                                                      In 1609, Thomas Harriot pressed his eye to the end of a tube with a convex lens and a concave eyepiece. That lens magnified the Moon, which was five days past new Moon, bringing details into view that no human eye had ever seen. He sketched what he saw of the crescent Moon, making out the craggy line where sunlight peeked through valleys between mountains and crater tops. He drew the darker regions of long-frozen lava fields in what is known today as Mare Crisium. Much has evolved in lunar study-from the tools to the scientific understanding of the Moon-but it all began with this first observation through an early telescope.                                                                                                                                                                                                                                                                                                                              Galileo Galilei would begin his revolutionary study of Earth's companion a few months later. With his rudimentary telescope, he watched the shadows move and change on the surface during the Moon's 29.5 day cycle. Up until that point, it was thought that everything that existed in the cosmos orbited Earth in a celestial sphere, with all the stars fixed on the surface of the heavens. Galileo's astronomical studies of the Moon, along with the moons of Jupiter and the phases of Venus, threw that theory out the wondow.                                                                                                                                                                                                                                                                                                                         In the years that followed, observer after observer looked through early telescopes to sketch maps of the lunar surface. Those observers named features on the Moon after royal family members, scientists, and Earth's regions and natural landforms. Some believed that the dark regions that are visible from Earth were water features like seas and oceans. While today it's understood that these are actually impact basins filled with solidified lava, but their early names endure and we can still call them "mare" and "oceanus."                                                                                                                                                                                                                                                                                                     Observations of the lunar features would only improve over time, especially with the introduction of photography in the mid-1800s. Once astronomers had the capacity to take long-exposure photographs to capture detail in Moon images, they could make out more and more features, and with greater specificity. To this day, mapping the Moon's surface remains a critical scientific enterprise.