Distance
At an average distance of 385,000 km from Earth, the Moon is our closest neighbour in space. That distance is the same as travelling ten times around the planet, a journey that would take a jet aircraft travelling nonstop about two-and-a-half weeks. Yet light from the Moon reaches Earth in only 1.25 seconds.
Appearance
If we look at the Moon through a telescope we see that it is covered by craters — round depressions with raised rims — of all sizes. These are due to the impact of meteorites. Since there is neither wind nor rain on the Moon to wear away the craters, they preserve a record of the Moon’s bombardment from thousands of millions of years ago to the present day. By tradition, craters are named after scientists, philosophers and writers. In 1973 one small crater was named after the famous 19th-century Australian astronomer, John Tebbutt.
There are also giant dark regions on the Moon’s surface, which were once thought to contain water and so were misnamed maria (plural of the Latin mare meaning ‘sea’). The first crewed landing on the Moon in July 1969 was in Mare Tranquillitatis or the Sea of Tranquillity. Maria are regions where lava has covered low-lying basins carved out by huge impacts. They have fewer craters than other regions on the Moon because the lava flows occurred after much of the meteoric bombardment was over. Any craters in the maria today were formed after the lava cooled and solidified. Strangely, the far side of the Moon has more craters than the near side and few, if any, maria.
Two craters in the Ocean of Storms: the old one on the left is eroded and degraded, while the young one on the right is surrounded by boulders. Courtesy NASA/GSFC/Arizona State University
Some of the Moon’s features such as the major seas can be discerned with the unaided eye, especially when the Moon is low in the sky and appears to be larger than usual. Of course, the view through a pair of binoculars or a small telescope is even better. The best time to view the Moon through a telescope is when it is at first quarter phase, when deep shadows allow detail on craters and other lunar structures to be seen.
The map below is shown with the correct orientation for viewing the Moon with binoculars. The table beneath gives the English names of the main features identified on the map, together with the key to the abbreviations. The map was created by lunar observer Harry Roberts.
