Vocabulary
axis An imaginary line that runs from the North Pole to South Pole, and includes the
center Earth.
ellipse A shape that looks like a slightly squashed circle.
hemisphere One half of a sphere.
revolution The Earth’s movement around the Sun in an orbital path.
rotation The motion of the Earth spinning on its axis.
Points to Consider
- What type of experiment could you create to prove that the Earth is rotating on its
axis? - If you lived at the equator, would you experience any effects due to Earth’s tilted axis?
- If Earth suddenly increased in mass, what might happen to its orbit around the Sun?
24.3 Earth’s Moon
Lesson Objectives
- Explain how scientists believe the Moon formed.
- Describe the features of the Moon.
Introduction
On July 20, 1969 hundreds of millions of people all over the world excitedly sat in front of
their televisions and witnessed something that had never happened before in the history of
the world. On that day, two American astronauts named Neil Armstrong and Edwin “Buzz”
Aldrin landed theEagleon the surface of the Moon (Figure24.12). Neil Armstrong was
the commander of the mission, and he was the first human to ever step foot on the Moon.
No other place in space, besides Earth, has been touched by humans. Even today, the Moon
remains the only other body in space that humans have visited.
Between 1969 and 1972, six piloted spaceships were sent to land on the Moon. They are
often referred to aslunarexpeditions, the word lunar meaning “related to the Moon.” On