Revolution or 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
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
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.
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
∑ The NASA Apollo missions added a great deal to our understanding of
∑ Our understanding of the sun, moon, and the solar system continues
to change with new scientific discoveries.