Astronomy (天文学) is the oldest science known to man. Thousands of years ago man looked at the stars and wondered about heavens (天堂). But the six planets that he could see with his eyes alone limited man.
The Greeks studied astronomy over 2,000 years ago. They could see the size, color, and brightness of a star. They could see its place in the sky. They watched the stars move as the seasons changed. But the Greeks had no tools to help themselves study the heavens.
Each new tool added to the field of astronomy helped man reach out into space. Until there were telescopes (望远镜), man did not know much about the moon. He did not know that the planet called Saturn (土星) had rings around it. His sight was so limited that he could not see all the planets. In the early 1700s, people thought there were only six planets. Pluto (冥王星), the last of the nine planets to be discovered was seen until 1930.
Before the spectroscopes (分光镜), man didn’t know what kind of gas was in the sun or other stars, without radio telescopes (射电望远镜), we did not know that radio noise came from far in space.
Today, astronomy is a growing science. We have learned more in the past fifty years than in the whole history of astronomy.
Thousands of years ago, man watched ____ with his eyes.

A．the moon

B．the stars

C．the universe

D．all the planets

When the Greeks watched the stars, they could ____ .

A．know what the stars were made of	B．not see their places in the sky
C．help themselves study the heavens	D．watch the stars move as the seasons changed

Until there were ____ , man knew very little about the moon.

A．telescopes

B．spectroscopes

C．radio telescopes

D．spaceships

People didn’t know about Pluto until ____ .

A．the 1700s

B．2,000 years ago

C．1930

D．thousands of years ago

____ people began to do research on astronomy.

A．50 years ago

B．90 years ago

C．In the early 1700s

D．Over 2,000 years ago