Many animals do strange things before an earthquake. This news may be important. Earthquakes can kill people and knock down homes. The animals may help to save lives.

Some animals make a lot of noise before an earthquake. Farmers have told about this. Dogs that are usually quiet have started to bark(吠). Horses on farms have run around in circles. Mice have left their holes and run away. Cows have given less milk.

In a town in Italy, cats raced down the street in a group. That happened only a few hours before an earthquake. In San Francisco, a man kept tiny pet frogs. One Sunday, the frogs jumped around more than ever. They made loud noises, like bigger frogs. That night, an earthquake struck the city.

    People want to know when an earthquake is coming. Then they could get away safely. Right now, there is no sure way to know ahead of time. Maybe the best idea is watching the animals.

    The word “day” has two meanings. When we talk about the number of days in a year, we are using “day” to mean 24 hours. But when we talk about day and night, we are using “day” to mean the time between sunrise and sunset. Since the earth looks like a ball, the sun can shine on only half of it at a time. Always one half of the earth is having day and the other half night. A place is moved from day into night and from night into day over and over by the spinning（旋转）of the earth. At the equator（赤道）day and night are sometimes the same length（长度）. They are each twelve hours long. The sun rises at 6 o'clock in the morning and sets at 6 o'clock in the evening. For six months the North Pole（北极）is tilted（倾斜）toward the sun. In those months the Northern Hemisphere（半球）gets more hours of sunlight than the Southern Hemisphere（半球）. Days are longer than nights. South of the equator nights are longer than days. For the other six months the North Pole is tilted away from the sun. Then the Southern Hemisphere gets more sunlight. Days are longer than nights. North of the equator nights are longer than days. Winter is the season of long nights. Summer is the season of long days.

Would it surprise you to learn that, like animals, trees can communicate with each other and pass on their wealth to the next generation—their young trees?

    Suzanne Simard, forest ecologist(生态学家) at the University of British Columbia, explains how trees are much more complex(复杂的) than most of us ever imagined. Although Charles Darwin(达尔文) thought that trees are competing for survival of the fittest, Simard and her team have made a new discovery and showed just how wrong he was. In fact, the opposite is true: trees survive through their group work and support, passing around necessary nutrition(营养) such as nitrogen(氮) and carbon "depending on who needs it".

    Nitrogen(氮) and carbon are shared through miles of underground fungi (真菌) networks. This makes sure that all trees in the forest ecological system give and receive just the right amount to keep them all healthy. This system works in a very similar way to the networks of neurons (神经元) in our brains, and when one tree is destroyed, it influences all.

    Simard talks about "Mother trees". These are usually the largest, oldest plants that on which all other trees depend. These "Mother trees" are connected to all the other trees in the forest by this network of fungi, and may manage the resources of the whole trees and plants in the forest. She explains how these trees pass on the wealth to the next generation, transporting important resources to young trees so they may continue to grow. When humans cut down "Mother trees" without paying attention to these highly complex "tree societies" of the networks on which they feed, we are reducing the chances to save the whole forest.

    "We didn't take any notice of it," Simard says sadly. "Mother trees" move nutrition into the young trees before dying, but we never give them chance. If we could put across the message to the forestry industry, we could make a huge difference towards our environmental protection efforts for the future.

    Once people thought that dinosaurs were brown or gray in colour, but the answer is to be found out. After examining the remains of a dinosaur, scientists say the colour of the feathers is bright. American and Chinese scientists rebuilt the feathers of a flightless(不能飞的)dinosaur

that lived about 150 million years ago, and researchers studied melanosomes(黑素体)in the feathers. The researchers compared them to the melanosomes that control the colour of feathers on modern birds. They were then able to make out the colours of dinosaurs' feathers. Richard Prum, a biologist(生物学家)at Yale University, said the dinosaur would be a beautiful creature if it were still alive. The discovery is useful to scientists in another way. It helps them better understand not only how dinosaurs looked but also how they lived in their daily life. Some researchers plan to use this way to study the colours of other feathered dinosaurs.

    As space science develops, man has learned more and more about space. Space is not only amazing but also dangerous. While working in space, spacemen are facing danger as well as success.

    Scientists have found out that radiation(辐射) is the greatest danger to spacemen in space. When spacemen are working in space, they are in danger of radiation from the sun and other stars, which is bad for their health. The damage(危害) done by radiation won't be discovered until their children or even grandchildren are born. Some special medicine may work a little, but no really helpful medicine has been.

    Space junk is also thought a great danger to spacemen. It's reported that there are 9, 000man﹣made things flying in space. About 30% of these are satellites, 10% are spaceships, and the rest are space junk. An explosion(爆炸) in 1996made a cloud of 300, 000 fragments, each at least 4mm in size, and even a small piece of these knocked against a spaceship window and did some damage. Scientists are watching and reporting any possible danger all the time. They are working on helpful ways to do with space junk.

    Although space is really dangerous, it interests everyone on the earth. In the near future, it may become usual for people to spend a few days in a space hotel. We may even choose to leave the earth and live in space in a few years. So we should care for space and do something to help improve the space environment.