When we talk about the universe, we mean not only the earth, the sun and the moon, but also the stars and space between them. There are millions of stars in our sky. The sun is one of them. Around it there are eight big planets moving, including the earth. The moon is our nearest neighbor in space. If you look at the sky on a clear night, it is possible to see about 3, 000 stars. They look small, but they are really very big hot balls of burning（燃烧着的）gas. Some of them arc huge（巨大的）, but others are much smaller like our planet Earth. The biggest stars are very bright, but they can only live for a short time. Every day new stars are born and old stars die.

    All the stars are very far away. The light from the nearest star（except the sun）takes more than four years to reach the earth.

    Hundreds of years ago, people used stars, like the North Star, to know which direction（方向）to travel in.

Today you can still see that star.

    Have you ever dreamed about a trip to the space? Seeds (种子) of some vegetables and crops are a lot luckier than you, as they have travelled to space and back.

    China is among the three countries in the world that carry out agricultural research (农业研究) in space. The others are Russia and the US.

    Since 1987, China has sent about 1, 000 species of seeds into space.

    These include green peppers, tomatoes, cucumbers (黄瓜), carrots, lettuce and wheat. Even on China's first manned spacecraft Shenzhou—V, there were some seeds from Taiwan.

    "Conditions in outer space such as radiation (辐射) and low gravity can cause big changes in the seeds," said Chinese researcher Jin Xing.

    But not all seeds are better after going to space. After returning to the Earth, the best seeds are selected. These seeds produce (生产) much more and also grow faster than normal (正常的) seeds

    Earthquakes are hard to predict, but do you know what to do before, during and after an earthquake? Here's some advice:

    Before an earthquake. It's necessary to prepare yourself and your family. All family members should know how to turn off the gas, water and electricity and know useful telephone numbers (120, 110, 119, etc.). Never put heavy things over beds.

    During an earthquake. It's important for each of you to stay calm. If you are indoors, quickly move to a safe place in the room such as under a strong table. The purpose(目的) is to protect yourself from objects. Stay away from windows, large mirrors, heavy furniture and so on. If you're cooking, turn off the gas. If you're outdoors, move to an open area like a playground. Move away from buildings, bridges and trees. If you are driving, stop the car as soon as possible and stay away from bridges and tall buildings.

Stay in your car.

    After an earthquake. Once the shaking has stopped, DO NOT run out of the building at once. It's better to wait and leave when it's safe. Check around you and help the people who are in trouble. If your building is badly broken, leave it. If you smell the gas, get everyone outside and open windows and doors. If you can do it safely, turn off the gas. Report it to the gas company.

    The name of our galaxy(星系), the Milky Way, comes from its appearance. It's a milky white band of glowing light that spreads across the night sky. If you look up at the evening sky, there's a good chance you will not be able to see what your grandmother saw when she was a little girl. A new study says that nearly 80 percent of people in North America can't see the Milky Way because of light pollution.

    The most light-polluted country in the world is Singapore where researchers found that people living in the country never have the chance to experience true darkness. Other countries with large percentages of people living under such skies include Qatar, Kuwait and the United Arab Emirates.

    Too much light has a direct influence on human physiology and behavior. It can also destroy our sleep cycle. What's more, it also influences wildlife. For example, baby turtles may not swim into the ocean because of street lights near shorelines.

    In the U.S., some communities have been taking action on light pollution but in developing countries, people still want to make bigger, brighter light, like LED lights. They can save energy, but on the other hand, they will increase light pollution rapidly in fact.

    There are still people that can remember when they used to be able to see the Milky Way, when they would walk outside at night, but those are becoming fewer and fewer.

    Nighttime natural scenery needs protection just like daytime scenery. Don't let the light pollution steal the chance to experience the wonder of a natural night sky from us.

    Do you believe that only boys do well in science? Does it seem that girls have better language skills than boys? In your opinion, are boys better at building things? If your answer to each of those questions is" Yes", you are right, according to an article in Current Science. There are exceptions(例外),but here are the facts.

    Usually, boys score higher in tests about math, while girls do better in tests about words, spelling and memory. But these differences may not always be true. In the future, a person's abilities may not be decided by sex. As one scientist says, "Nothing is impossible for a person to be or do."

    A recent study by Jerome Kagan, a scientist at Harvard University is studying the watching ability of children who are 10 months old. Baby boys and baby girls are watching "show" while seated on their mothers' laps. In Act One of the show, an orange-colored ball is lifted from a blue box and moved slowly. Then it is returned to the box. This is repeated six times. Act Six is almost the same, except that the orange ball is smaller. Baby boys do not seem to notice the difference in the size of the ball, but girls immediately become excited and begin to make noises that sound like language.

    It's also known that baby girls usually talk at an earlier age than baby boys do. Scientists believe that the left side of the brain develops faster in girls than in boys. As a result, by the time they start to go to school, little girls have an advantage that boys don't have, but what have the boys been doing in the years before starting school? They have been developing something called aggression. An aggressive person feels strong and independent. He is often the first one to start a fight. It is said that aggression is caused by hormones(荷尔蒙). Scientists believe that hormones are not the only cause. They say aggression in boys is also caused by mothers.