Sue Ann Schultz, age 13, of Woonsocket, R.I., for her question:
WHEN WAS THE MOON CREATED?
After studying lunar samples brought back by the Apollo astronauts, scientists have decided that the moon is about 4.6 billion years old. The moon's age is determined by measuring the amounts of radioactive atoms of certain elements in the lunar soil.
Each of the radioactive atoms decays or changes into another element at a known rate. How long this decay has been occurring can be figured by comparing the amount of radioactive atoms of an element with the amount of the atoms of the elements into which it has decayed.
The Earth and meteorites that have fallen on the Earth are also about 4.6 billion years old. On the basis of this evidence, scientists say that the entire solar system may have been formed at about that same time.
Most of the large craters in the highlands of the moon were formed when many large solid bodies from space struck the moon. Scientists believe this bombardment took place between 3.9 and 4.6 billion years ago.
The "escape" theory of the moon's origin says that the Earth and the moon were once a single body. The sun's gravity caused a bulge on one side of the fast spinning Earth. A lopsided dumbbell formed and the small end broke away and became the moon.
The "captured" theory of the moon's formation says that the moon was once a planet that traveled around the sun. At some point along its orbit, the moon was captured by the Earth's gravity and became a satellite of the Earth.
A third moon formation theory says that the moon was formed at about the same time as the Earth and in the same region of space. The two bodies were made from huge whirlpools of gas and dust that were left over when the sun was formed.
The large craters created early in the moon's history may have been formed by the impact of smaller moons that were circling the Earth, or by planetesimals that were orbiting the sun.
Since ancient times, man has measured time by the phases of the moon.
Many early peoples thought the moon was a powerful god or goddess. The ancient Romans called their moon goddess Diana. She was the goddess of the hunt and the guardian of wild beasts and fertile fields. She used a moon crescent for a bow and moonbeams for arrows.
The moon goddess of ancient Greece was called Selene. And early Egyptians honored the moon god named Khonsu while the Babylonians knew the moon as Sin, sometimes called Nanner, the most powerful of the sky gods.
Today, some primitive peoples still worship the moon.
Early wise men and priests taught that the moon was related to birth, growth and death because it waxed and waned.