How Do Scientists Explore Space?

EARTH, SPACE, AND BEYOND

HOW DO SCIENTISTS

EXPLORE SPACE?

Contents

Sky Watchers

Project Planet

Comet Encounters

Solar Explorers

Other Stars, Other Worlds

Being There

Timeline of Space Exploration

Glossary

Find Out More

Index

Some words are shown in bold, like this. You can find out what they mean by looking in the glossary. You can also look out for them in the Word Station box at the bottom of each page.

Sky Watchers

The earliest space explorers were the first people who looked up at the night sky and wondered about the things they saw. The beginnings of space exploration took place from the ground with no more sophisticated tools than sharp eyes and inquiring minds.

These immense columns of gas and dust are big enough to swallow our entire solar system many times.

Ancient astronomers imagined patterns connecting the stars in the sky. These patterns are called constellations.

Navigation

The patterns of stars are called constellations. First labeled in ancient times, modern astronomers still use constellations as a convenient way to divide and describe the night sky. We can also use the stars to find out where we are on Earth. For example, for centuries people have known that facing Polaris, the North Star, means that they are facing north. Hundreds of years ago sailors had starcharts that told them how far above the horizon a star should be. Measuring the angle of the star above the horizon told them how far north or south they were.

Fixed stars

The first sky watchers would have noticed that most of the objects in the night sky always kept the same positions relative to each other. They rose and set in orderly patterns that always stayed the same. People of different countries, such as the Greeks, Chinese, and Indians, named these patterns of stars after gods and heroes. The night sky became a storybook of myths and legends.

Wandering stars

The sky watchers of long ago also saw that there were some objects that didn’t follow regular paths. The ancient Greeks called them planetes (wanderers) from which we get our word planet. The early observers built up precise records of the movements of stars and planets across the night sky. These observations became the basis of the modern science of astronomy, the study of everything that lies beyond the Earth’s atmosphere.

Aristarchus

Aristarchus, who lived over 2,200 years ago, was one of the greatest astronomers of ancient Greece. He used his observations to work out the sizes and distances of the Sun and Moon. He had no sophisticated instruments with which to make measurements and the answers he got were wrong, but his methods were correct. He correctly worked out that the Sun was very much