From a plane you can see the fields,     1    , mountains or rivers below. If we go into space, we see more and more of the earth. People and man-made satellites are     2     out into space to look at the earth, the stars and other     3     and learn more about them.

The moon is our     4     neighbour in space. It is our satellite and men have visited it already. It is smaller than the earth.     5     can’t grow on the moon because there’s no air or water on it.

The moon hasn’t its own light. It     6     back the light of the sun. When the sun is shining on the side of the moon that faces us, it     7     like a great round ball. We can’t see the moon when the sun is shining on the side of the moon that faces away from     8    .

In fact the moon isn’t as near as it looks. It is three     9     and eighty thousand kilometres away from the earth. Of course we can fly to the moon in a spaceship. A spaceship     10     very, very fast, and it flies at about eleven kilometres a second. So it only takes more than three days to get there by spaceship.

Is there intelligent (有智力的) life on other planets? For years, scientists said “no.” or “we don’t know.” But today this is changing. Seth Shostakovitch and Alexandra Barnett are astronomers (天文学家). They believe intelligent life exists (存在)     1     in the universe. They also think we sill soon contact these beings(人；生物).

Why do Shostakovitch and Barnett think intelligent life exists on other planets? The first     2     is time. Scientists believe the universe is about 12 billion years old. “This is     3     enough for other planets to have intelligent life,” says Shostakovitch and Barnett. The second reason is size—the universe is huge. “Tools like the Hubble Telescope (哈勃望远镜) have     4     that there are at least 100 billion galaxies,” says Shostakovitch. “And our galaxy, the Milky Way, has at least 100 billion stars. Some planets going around these stars might be     5     to Earth.”

In the past, it was hard to look for     6     of intelligent life in the universe. But now, powerful telescopes (高倍望远镜) allow scientists to     7     smaller planets—the size of Mars or Earth—in     8     solar systems. These planets might have intelligent life.

Have beings from space already visited Earth? “Probably not,” says Shostakovitch. “It’s a long way away. However, intelligent beings may contact us in other way, such as radio signals (信号). In fact, they may be trying to communicate with us now, but we don’t have the right tools to     9     their messages. However, this is changing. By 2025, we could make contact with other life     10     in our universe and we might help each other.”