11The sky above mountain-
top observatories far from
city lights is the same sky
you see from your window.
The stars above you are
other suns scattered
through the universe.
(Kris Koenig/Coast Learning
Systems)Guidepost
The previous chapter took you on a cosmic zoom through space and time. That quick
preview only sets the stage for the drama to come. Now it is time to look closely at the
sky and answer four essential questions:
How do astronomers refer to stars and compare their brightness?
How does the sky appear to move as Earth rotates?
What causes the seasons?
How can astronomical cycles affect Earth’s climate?
As you study the sky and its motions, you will be learning to think of Earth as a planet
rotating on its axis. The next chapter will introduce you to some of the most dramatic
cycles in the sky.