Moon is the only known natural satellite of the earth. It is the brightest object in the sky after Sun. The moon travels around the earth in the orbit elliptically. It orbits around the earth counter clockwise from west to east at 2,300 miles per hour. It is 1/4th the size of the earth. The moon doesnot have the light of its own. It reflects the light of the sun. The temperature of the moon ranges between 123 degree C to 233 degree C.The moon is cold and dry as it has no atmosphere.
The moon is around 4.5 billion years old. Scientist proposes The Giant Impactor Theory for the formation of the moon. The theory suggests that just after the formation of the solar system, the moon was created when a Mars-sized giant asteroid collided with our planet earth. This ejected large volumes of heated material from both the objects which ultimately stuck together to form moon orbiting around the earth.
The moon has a dry, dusty and rocky surface with the surface studded with craters and basins. The craters and basins are formed by meteorite collision. The bright and deep craters are called terrae.The moon has a very small core about 680 km wide which consist of iron and sulfur. The mantle is rocky and about 1,330 km in thickness containing large amount of iron and magnesium. The moon crust on the top is 70 km deep and is wrecked and cluttered. The composition of the moon surface is about 43% oxygen, 20% silicon, 19% magnesium, 10% iron, 3% calcium, 3% aluminium, 0.42% chromium, 0.18% titanium and 0.12% manganese.
The moon has a surface area of 9.4 billion acres. The moon is 384,403 km far from the earth. It completes one rotation and revolves around the earth in 27 days 7 hours, 43 minutes and 11.6 seconds. It rotates around its own axis. The diameter of the moon is 3,476 km. Only 59% of the moon surface is visible from earth. The gravity of the moon is one-sixth that of the earth. The moon has no magnetic field.
The gravitational influence of the moon produces the ocean tides. During full moon the gravitational forces of the Sun and Moon combine to produce the highest tides called Spring Tides. It is in synchronous rotation with earth which is caused through unsymmetrical distribution on mass in the moon. Due to this earth’s gravity, the same side of the moon always faces the earth.The near side is evident with dark Maria which covers about 16% of the moon surface and is volcanic and the bright crusted highlands.
In 1959, Soviet Union,s Luna programme launched the first unmanned spacecraft, Sputnik 1. In NASA’s Apollo program, Apollo 11 was launched on July 20, 1969 from the Kennedy Space Center. The crew of Apollo 11 consisted of Commander Neil Armstrong who was the first man to walk on the surface of the moon. He was followed by Lunar Module Pilot Edwin E. Aldrin and Command Module Pilot Micheal Collins.
