This means that the force between the Earth and the Moon is not exactly along the line between their centers producing a torque on the Earth and an accelerating force on the Moon. The Earth’s rotation carries the Earth’s bulges slightly ahead of the point directly beneath the Moon. (This is a greatly simplified model actual tides, especially near the coasts, are much more complicated.)īut the Earth is not completely fluid, either. And because the Earth rotates much faster than the Moon moves in its orbit, the bulges move around the Earth about once a day giving two high tides per day. The effect is much stronger in the ocean water than in the solid crust so the water bulges are higher. From our perspective on the Earth’s surface we see two small bulges, one in the direction of the Moon and one directly opposite. Since the Earth, and particularly the oceans, is not perfectly rigid it is stretched out along the line toward the Moon. The Moon’s gravitational attraction is stronger on the side of the Earth nearest to the Moon and weaker on the opposite side. The gravitational forces between the Earth and the Moon cause some interesting effects. In the summer of 1994, the Moon was very extensively mapped by the little spacecraft Clementine and again in 1999 by Lunar Prospector. The Moon is also the only body from which samples have been returned to Earth. The first landing was on J(do you remember where you were?) the last was in December 1972. It is the only extraterrestrial body to have been visited by humans. The Moon was first visited by the Soviet spacecraft Luna 2 in 1959. The time between successive new moons is 29.5 days (709 hours), slightly different from the Moon’s orbital period (measured against the stars) since the Earth moves a significant distance in its orbit around the Sun in that time.ĭue to its size and composition, the Moon is sometimes classified as a terrestrial “planet” along with Mercury, Venus, Earth and Mars. As the Moon orbits around the Earth once per month, the angle between the Earth, the Moon and the Sun changes we see this as the cycle of the Moon’s phases. It is the second brightest object in the sky after the Sun. The Moon, of course, has been known since prehistoric times.
The Moon ProfileĬalled Luna by the Romans, Selene and Artemis by the Greeks, and many other names in other mythologies.
It’s the fifth-largest moon in our solar system and is the second brightest object in the sky (after the Sun). It was created 4.6 billion years ago, and it is widely accepted that it was created when Earth collided with a planet-sized object called Theia. The Moon, otherwise known as Luna, is the only natural satellite of Earth.
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