Hurricanes(飓风) are storms. They can cause terrible waves, wind and rain. They happen in the Atlantic Ocean and the Pacific Ocean most of the time.

Category(类别)

·Scientists divide(划分) them into five categories according to the wind speed.

·A Category 5 hurricane can destroy(摧毁) all the buildings.

Characteristic(特征)

·Hurricane Season usually comes on June 1^st and ends on November 30^th in the Atlantic Ocean, from May 15^th to November 30^th in the Pacific Ocean.

Danger

·It can cause flood when a hurricane comes with heavy rain.

·A hurricane has an eye. The eye means the center of a hurricane. After the eye passes, the wind and rain comes again.

Safety advice

·Stay inside during the Hurricane, or you'll be injured.

    We have known for a long time that flowers of different plants open and close at different time of day. Yet no one really understands why flowers open and close like this at special times. It is not as simple as we might think, as new experiments(实验) have shown. In one experiment, flowers were kept in darkness. We might expect that the flowers, without any information about the time of the day, did not open as they usually do. In fact, they continued to open at their usual time. This shows that they have some mysterious (神秘的) way of knowing the time.

    Their sense of time does not depend on information from the outside world; it is, so to speak, inside them, a kind of “inner clock”. This discovery may not seem to be very important. However, it was later found that not just plants but also animals including man have this “inner clock”which controls(控制) working of their bodies and their activities.

    Human beings, then, are also controlled by this mysterious power. Whether we wish it or not, it affects such things in our life as our need for sleep, our need for food. And our ability to concentrate(集中).

    You probably know a typhoon is a large and powerful storm that can cause a lot of rain and wind. Everyone pays attention to typhoons because they can be dangerous. Some typhoons come and go and really don't cause much more trouble than a bad thunderstorm. Others may damage homes and cause some floods that go away on their own.

    Typhoons are always a concern, especially for people who live near the coast. When a typhoon is on the way, weather forecasters can say which areas will be affected. Maybe you've heard people call a typhoon a "natural disaster", but what does that mean? A natural disaster is something that happens in nature and causes big problems, like a typhoon, a tornado(龙卷), an earthquake, or a tsunami. But wherever you live, it's important to remember that there are lots of people looking out for you. In a bad storm or other crisis, this would include not only mums and dads, but also police officers, firefighters, doctors, nurses, and other people who are trained to handle emergencies.

    On July 20, 1969, Neil Armstrong became the first person to walk on the moon. The space suit Armstrong wore on his lunar mission has come to symbolize courage and human achievement. In 1971, the Smithsonian's National Air and Space Museum(NASM), in Washington, D.C., acquired (获得) Armstrong's suit. It stood proudly on display for visitors to admire, until there were changes in the suit's appearance. "Over time, the suit started to show signs of deterioration," Lisa Young said. Young is an objects conservator (文物修复员) at NASM. It is her job to preserve(维护)historical and cultural objects.

    "Plastics are tricky to conserve," Young says. They tend to degrade (降解)over time. Neoprene is one type of plastic in Armstrong's suit. The material can turn brittle and break into tiny pieces. This would ruin the space suit. NASM, seeking ways to preserve this historical treasure, removed it from display in 2006.

    What causes plastic to degrade in the first place? "Many things," Odile Madden says. Madden is a scientist in California. She explains that sunlight, water, humidity, and dust can cause plastics to degrade. "Some plastics will break down no matter what we do," Madden says.

    Yet history can still be saved. Scientists have found that storing plastics in cooler temperatures, with lower humidity levels, can slow degradation. Young says Armstrong's suit is currently in storage at a temperature of 63°F and a lower relative humidity of 30%. These conditions will be maintained when Armstrong's suit returns to a museum display case in time for the 50^th anniversary of the moon landing.

    Plastic degradation affects art, too. Artist Claes Oldenburg created False Food Selection in 1966.It consists of plastic food displayed in a wooden box. The plastic food used to look real. Now, some of it has flattened and yellowed. Georgina Rayner is a conservation scientist at Harvard Art Museums, in Cambridge. She says the artwork's wooden box produces an acidic (酸的) gas that eats away at the plastic. This speeds up the degradation process. But Rayner is motivated to conserve this artwork and others like it. "Plastics are a part of our history," she says. "It's important to preserve them so that future generations can understand the journey we've taken."