Study Guide SOL 4.7 
The Sun, Moon and Earth

Revolution or Rotation?

Rotation and Revolution:
The Earth completes one revolution (or orbit) around the sun every year (365 days). The Earth completes one rotation on its axis every 24 hours.  Day and night are caused by the Earth's rotation on its axis.

The Seasons and the Earth's Tilt

Earth's tilt causes seasons:   The Earth is tilted on its axis as it revolves around the sun. The  hemisphere tilted toward the sun receives the sun's rays more directly and  therefore has warmer temperatures as well as  longer days (summer), while the half of the Earth tilted away has cooler temperatures and shorter days (winter).  It's important to realize that warmer summer temperatures occur because the Sun's rays are striking more directly, not because part of the Earth is closer to the Sun.


   The Phases of the Moon
The moon revolves around the Earth about once every month. The phases of the moon are caused by its position relative to the Earth and the sun.  (we see only part of the sunlit side of the moon) The phases of the moon include the new, waxing crescent, first quarter, waxing gibbous, full, waning gibbous, last quarter, and waning crescent.

Solar and Lunar Eclipses

-Due to the moon's revolution around the Earth, a lunar eclipse will occur when it moves into the Earth's shadow. A solar eclipse will occur when the moon moves between the sun and the Earth.


The Sun, the Moon and the Planets

The sun is an average-sized yellow star, about 110 times the diameter of the Earth. The sun is approximately 4.6 billion years old.
Our moon is a small rocky satellite, having about one-quarter the diameter of the Earth and one eightieth its mass. It has extremes of temperature, (virtually) no atmosphere, no water, and no life.

∑ The Earth is one of nine planets that revolve around the Sun and comprise the solar system. The Earth, third planet from the sun, is one of the four rocky inner planets. It is about 150 million kilometers from the sun.
∑ The Earth is a geologically active planet with a surface that is constantly changing. Unlike the other four inner planets, it has large amounts of life-supporting water and an oxygen-rich atmosphere. The Earthís protective atmosphere blocks out most of the sunís damaging rays.

Aristotle, Ptolemy, Copernicus and Galileo

∑ Our understanding of the solar system has changed from an Earth-centered model (Aristotle and Ptolemy) to the sun-centered model (Copernicus and Galileo).
∑ The NASA Apollo missions added a great deal to our understanding of the moon.
∑ Our understanding of the sun, moon, and the solar system continues to change with new scientific discoveries.