The Earth-Moon-Sun SystemThe Earth-Moon-Sun System

The Earth has a few different motions associated with it. The two main motions are rotation and revolution. Rotation is the turning or spinning of a body on its axis. Revolution is the motion of a body, such as a planet or moon along a path around another body.

Earth also has another motion called Precession. Precession is the slight movement over a period of 26,000 years, of the Earth’s axis.

The main results of Earth’s rotation are day and night. Each rotation takes about 24 hours.

Earth revolves around the sun in an elliptical orbit. It has an average distance of 93 million miles from the Sun. Bucause the path is an ellipse the distance from the sun varies from 91 million miles around Jan. 3rd and 94 million miles around July 4th each year.

The planets and the moon travel in nearly the same plane as the Earth, which is the same plane as the sun appears on the back drop of the celestial sphere. This is called the plane of the ecliptic.

The Earth’s axis is tilted 23.5° from the plane of the ecliptic.

Because of the inclination of the Earth’s axis, Earth has yearly cycle of seasons.

The third motion again is called precession. The motion is very similar to the motion of a wobbling top. It takes 26,000 years for the precession to get all the way around.

The Earth also accompanies the sun and the rest of the solar system by moving within our own galaxy, the Milky Way. It takes 230 million years to get around our galaxy. And the Milky Way is approaching our galactic neighbor Andromeda.

The moon also has motion. The phases of the moon are a result of the motion of the moon and the sunlight that is reflected from its surface.

It takes the moon 27 1/3 days for the moon to revolve around the Earth. This is called the Sidereal month.

The cycle from full moon to the next moon takes 29 ½ days. This is called the Synodic month. This happens because the Earth is revolving around the Sun.

The side of the moon facing the Sun has a temperature of 260°F and the side away from the Sun is -280°F.

There are two types of eclipses that take place when the Sun, Moon, and the Earth all line up in the plane of the ecliptic. When the Moon comes between the Earth and the Sun and casts the Moon’s shadow onto the Earth it’s called a solar eclipse.

When the Earth comes between the Moon and the Sun and casts its shadow on the Moon it’s called a lunar eclipse. The next total eclipse of the sun visible from the U.S. will happen on August 17th, 2007.

The Moon is the Earth’s only natural satellite and is about ¼ of the Earth’s size, which makes us unique in the solar system. Most of what we know of the Moon came from the Apollo missions to the moon.

The lunar gravitational pull is 1/6 that of the Earth’s.

There are two main landscapes on the Moon dark lowlands and bright highlands.

Craters are the most recognizable features on the Moon and are the remnants of impacts of rapidly moving space rock.

The Moon is too small to hold in an atmosphere. For this reason there are many impact craters.

Some asteroid impacts caused some of the dark area called mare. Mare are ancient lava flows caused by asteroid impacts.

The most widely accepted model for the origin of the Moon is that when the solar system was forming, a body the size of Mars impacted the Earth. The giant-impact hypothesis is consistent with the evidence we have.

The rock the moon is made out of is mostly iron-poor mantle and crustal rocks. This would account for the Moon’s small iron core. The Moon is estimated to be about 4.5 billion years old, where the Earth is 4.6 billion years old. Why can we see many craters on the Moon, but not many on the Earth?