The Greenwich Royal Observatory located in Greenwich, England, has made great contributions to the fields of astronomy and navigation. King Charles II established the Greenwich Royal Observatory in 1675 and appointed the first Astronomer Royal, a position that has continued to the present day. The king told the first Astronomer Royal "to apply himself with the most exact care and diligence to the rectifying of the tables of the motions of the heavens, and the places of the fixed stars, so as to find out the so much desired longitude of places for the perfecting of the art of navigation." Since then, the observatory has performed this function, and more.
Two notable contributions made by the Greenwich Royal Observatory are the establishment of the prime meridian and the institution of Greenwich Mean Time (GMT), which took place concurrently. The prime meridian is the longitudinal line that encircles the earth and was designated as 0 degrees longitude in 1884. This line runs directly through one of the buildings on the site of the observatory. It has been estimated that there were at least 2,000 time zones before GMT was established as the international standard at the prime meridian. Today, a person can straddle that imaginary line in the Meridian Courtyard at the observatory and be standing in two different hemispheres.
The complex at Greenwich includes many edifices besides the observatory including the Meridian Building, Flamsteed House, the National Maritime Museum and the Queen’s house. Flamsteed House contains the apartments used through the centuries to house the Astronomer Royals and their families. It was also the first Greenwich Royal Observatory. In 1833, Flamsteed House made the news when a time ball was constructed on its roof. This time ball was designed to drop every day at precisely 1 p.m. GMT and has continued to do so for more than 150 years.
Visitors to the complex can visit view galleries filled with displays showing the formation of the universe, a history of timekeeping, photographs taken of deep space, and other stunning exhibits. The Greenwich complex also features a cutting-edge planetarium. Astronomers Royal at the observatory study the heavens with a 28-inch refracting telescope, one of the largest in the world. In 1997, the Greenwich Royal Observatory was designated a UNESCO World Heritage Site due to the advancements it has made in mankind's understanding of the universe. These include the first sightings of Uranus and the predicted return of Halley's comet.