Typically, as the Moon travels through the sky and approaches the Sun's position, it goes a little bit above or below the Sun. At times, however, it cuts right across the Sun and hides it for a few minutes. This is a solar eclipse.
On the other hand, sometimes, when the Moon is full and on the opposite side of Earth from the Sun, it passes through the earth's shadow. When the earth's shadow falls on the bright side of the Moon, it makes the moons surface dark. This is a lunar eclipse and may last several hours
STUDYING THE SURFACE
The Surface of the Moon:
It is easy to study the Moon's surface with the naked eye. Astronomers, long before modern times, have tried to understand the details they could view. Studying the moon's surface with the naked eye reveals both shadows and bright spots on the lunar surface. In 1609 an Italian scientist, Galileo, built a telescope to view objects in space and was able to see mountain ranges and craters on the Moon.
Terrain
The Moon's crust is an average of 68 km thick. Below the crust is a mantle and possibly a small core. The Moon's center of mass is offset from its geometric center by about 2 km in the direction toward the Earth. Also, the crust is thinner on the near side.
There are two primary types of terrain on the Moon: the very old, heavily-cratered highlands and the relatively smooth and younger maria. The maria comprises about 16% of the Moon's surface and is composed of huge impact craters that were later flooded by molten lava. Most of the surface is covered with regolith, a mixture of fine dust and rocky debris produced by meteor impacts.
Most of the craters on the near side are named for famous figures in the history of science such as Tycho, Copernicus, and Ptolemaeus. On the far side, craters are named for such figures as Apollo, Gagarin and Korolev.
The Moon also has huge craters on the South Pole such as Aitken which at 2250 km in diameter and 12 km deep is the largest impact basin in the solar system. Orientale, a multi-ring crater is located on the western limb.
The Moon provides evidence about the early history of the Solar System not available on the Earth. The Apollo and Lunar programs brought back to Earth a total of 382 kg of rock samples. These provide most of our detailed knowledge of the Moon. They are particularly valuable in that they can be dated. Most rocks on the surface of the Moon seem to be between 4.6 and 3 billion years old compared to the oldest terrestrial rocks which are rarely more than 3 billion years old.
The Moon has no global magnetic field. But some of its surface rocks exhibit remnant magnetism indicating that there may have been a global magnetic field early in the Moon's history.
Seas Without Water
Craters on the Moon were caused by meteorites bombarding the surface that occurred in early days of Moon. There are several dark patches on the surface of the Moon that astronomers thought were huge bodies of water. They include the Sea of Tranquillity, the Bay of Rainbows, and the Lake of Death.
Now scientists know that there is no water on the Moon and these areas are actually smooth, flat plains that formed ‹3.5 billion years ago when lava poured out from the interior of the Moon. This lava covered 15 percent of the lunar surface when it flowed into the lowlands.
Crater-Scarred Surfaces:
Most of these craters were formed when meteors rained down on the surface of the Moon. Few craters are found in the lowland indicating that the meteor impacts must have occurred before lava flowed from the moon's interior.
The bright area which covers the rest of the Moon have thousands of craters in the highlands. Some of the larger craters have mountainous edges or peaks that rise from their centers. They can be seen from the Earth without the aid of a telescope. The Moon has no atmosphere and so there is no wind or rain constantly eroding the surface. Due to lack of an atmosphere the Moon probably hasn't changed in billions of years except for the rare impact of meteorites. Therefore, the Moon provides evidence about the early history of the Solar System not available on the Earth. Samples of Moon rocks brought back to Earth help scientists look back billions of years to the early ages of the Solar System and provide information on how the Earth was formed.