98

Astronomers go to

extremes to build giant

telescopes atop high

mountains, where they

are above most of the

distortion caused by

Earth’s atmosphere.

(Mauna Kea Observatory)

Light and Telescopes

6

Guidepost

In the early chapters of this book, you looked at the sky the way ancient astronomers

did, with the unaided eye. In the last chapter, you got a glimpse through Galileo’s

telescope, and it revealed amazing things about the moon, Jupiter, and Venus. Now it is

time to examine the instruments of the modern astronomer.

You can begin by studying telescopes that gather and focus visible light, so you

need to be sure you understand what light is and how it behaves. But you will quickly

meet telescopes that gather invisible forms of radiation such as X-rays and radio waves.

Astronomers cannot overlook any clues, so they must use all forms of light. This chapter

will help you answer fi ve essential questions:

What is light?

How do telescopes work, and how are they limited?

What kind of instruments do astronomers use to record and analyze light?

Why do astronomers use radio telescopes?

Why must some telescopes go into space?

Astronomy is almost entirely an observational science. Astronomers cannot visit distant

galaxies and far-off worlds, so they must observe using astronomical telescopes. Twenty

chapters remain in your exploration, and every one will discuss information gathered by

telescopes.