Sally Ride was born in California in 1951. She was the first American woman to travel into space. She loved to play tennis and wanted to be a tennis player when she was young. But after three months' professional（专业的）training, she changed her mind. She went to Stanford University and started to study science. She studied stars and planets. She did researches at the university and got her PhD in astrophysics（天体物理学博士学位）after several years' hard work.

    In 1977, she took a test to become an astronaut. And then she was picked up from over 8, 000 people. In order to realize her dream of going into space, she had to get different kinds of special and difficult training. She learned how to fly a plane, how to jump out of a plane as well as how to operate（操作）special machines.

    Sally and four other astronauts flew a spaceship called Challenger on Jun. 18, 1983. She became the first American woman to travel into space. Later, she taught at the University of California. Then she wrote seven books on space for children, encouraging children to study science. Unfortunately, she died in 2012.

    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 Shostak and Alexandra Barnett are astronomers（天文学家）. They believe intelligent life exists（存在）somewhere in the universe. They also think we will soon contact them.

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

    In the past, it was hard to look for signs of intelligent life in the universe. But now, powerful telescopes（高倍望远镜）allow scientists to discover smaller planets-the size of Mars or the earth-in other solar systems, these planets might have intelligent life.

    Have beings from space already visited the earth? "Probably not, "says Shostak. "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 receive their messages. However, this is changing. By 2025, we could make contact with other life forms in our universe and we might help each other. "

    In the universe, as we know, there is the sun, the moon, the earth and a good many stars. Through our geography lessons, we know the earth goes round the sun, and the moon goes round the earth. We have day and night because the earth keeps turning all the time. When our part of the earth turns to the sun, it is day. When our part of the earth turns away from the sun, it is night.

    Just because the moon is closer to the earth than the sun, it looks much bigger than the sun. Big things will look smaller when they are farther, and small things also look bigger when they are nearer.

    The sun is bright enough to give out very strong light. The moon can't give any light at all, but it looks quite bright, too. Why? In fact, the light from the moon comes from the sun. The moon looks much bigger and brighter than the stars. But actually（事实上）the stars are much bigger and brighter than the moon. They look smaller than the moon also because they are farther away from the earth.

    There are still many other planets in the universe.

    But of all these planets, only on the earth there are living things and people can only live on the earth, too. But at 9：00 am on October 15th, 2003, Chinese pilot Yang Liwei was sent up to space. He stayed there for 21 hours. It was the first time for Chinese to get into space.

—Not              .

    Some countries are better than others at looking after the environment. In Europe, Germany(德国) and northern European countries work very hard to improve the environment. The people in Germany put their rubbish into different bags--paper in one bag, plastic in another. Laws do not allow people to burn too much coal.  

    In the l970s, as people learned more about environmental problems. The "Green" movement(运动) began and soon spread all over Europe. The "Green" movement tries to get governments to protect the environment. It collects information about how industry is damaging(毁坏) the environment and tells newspapers.