Chapter 23

Observing and Exploring Space

23.1 Telescopes

Lesson Objectives

• Explainhowastronomersusethewholeelectromagneticspectrumtostudytheuniverse
  beyond Earth.


• Identify different types of telescopes.


• Describe historical and modern observations made with telescopes.

Introduction

Manyscientistscaninteractdirectlywithwhattheyarestudying. Biologistscancollectcells,
seeds, or sea urchins and put them in a controlled laboratory environment. Physicists can
subject metals to stress or smash atoms into each other. Geologists can chip away at rocks to
see what is inside. But astronomers, scientists who study the universe beyond Earth, rarely
have a chance for direct contact with their subject. Instead, astronomers have to observe
their subjects at a distance, usually a very large distance!

Electromagnetic Radiation

Earthisseparatedfromtherestoftheuniversebyverylargeexpansesofspace. Occasionally,
matter from the outside reaches Earth, such as when a meteorite makes it through the
atmosphere. But for the most part, astronomers have one main source for their data—light.
Light can travel across empty space, and as it does so, it carries both energy and information.
Light is one type ofelectromagnetic (EM) radiation, or energy transmitted through
space as a wave.