Monarch butterflies from eastern Canada make the most amazing journey in the insect world. Each year, this butterfly travels about 3000miles to its winter home in central Mexico(墨西哥). How can it fly so far? And why does it make this long and dangerous trip? Scientists still don't have an answer.

 For many years, people in Mexico wondered where the orange-and-black butterflies came from every winter. Then, in 1937, a scientist started to follow and study the butterflies. For the next 20 years, he discovered that one butterfly started its journey in Canada. Four months later, it arrived in Mexico.

 The length of the butterflies find their way back to the same place? Another amazing thing is that the butterflies always return to the same area in central Mexico.

 How do the butterflies find their way back to the same place? This is an interesting question because only every fourth generation(代) makes the trip south. In other words, the butterfly that travels to Mexico this year is the great-great-grandchild of the butterfly that traveled there last year.

 Each year, four generations of a Monarch butterfly family are born. Each generation of the family has a very different life. The first generation is born in the south in late April. It slowly moves north, reproduces(繁衍), and then dies. On the trip north,two more generations are born, reproduce, and die. Each of these generations of butterflies is born. This generation has a much longer life. It lives for about eight months. This generation of butterflies makes the amazing journey back to the winter home of its great-great-grandparents. The butterflies spend the winter there, and in the spring they reproduce and then die. Their offspring will be the first generation of the next circle of life.

 Today, people are still studying the Monarch butterfly. But they are not clear about everything.

    A computer can get very hot when it works on a lot of programs. It can cost a lot to cool the computer. So some scientists want to know what would happen if the heat from the computer could be used.

    Large Internet companies such as Google and Microsoft have thousands of computers. As these computers deal with information， they produce lots of heat， so they need huge cooling systems. These systems send the heat into the air.

    A company in Holland thinks paying to make the computers work and then paying again to cool them are a waste of energy. So the company developed a special device—the e-Radiator.

    Boaz Leupe， head of the company， says that e-Radiator works as a heating system and saves money. He explains that the energy is used twice—once to heat the home and once to cool the computer and that the users don't have to pay to cool their computers.

    Five homeowners in Holland are testing the heating system in their homes.

    “We pay for the computer using， so， in that way， homeowners get heating for free.” Boaz says.

    Jan Visser is one of the homeowners. “If you use the computer more， the e-Radiator producers more heat，” he says， “It cannot provide enough heat if you don't use your computer often.” But he is ready to try it. It's a great help for his family.

    The company says e-Radiators produce heat temperatures of up to 55℃. It says the system could save its users about $440 a year.

    A study of sleep in sparrows suggests the relationship between sleep and the ability to learn may be more complicated (复杂) than realized．

    Niels C. Rattenborg of the University of Wisconsin—Madison wanted to find out how the sparrows were able to deal with getting so much less sleep．He and his team brought eight wild birds into a lab and watched them for one year．They invented a game to check how well the birds could learn．In the game, the sparrows had to peck (啄) three buttons (按钮) in a certain order to get a food treat．The scientists discovered that the birds' ability to learn the right button order depended on (依靠) two things, the time of year and the

amount of sleep the birds had．

    During the migration (迁徙) season, the sparrows were restless at night and got much less sleep than usual．Even so, they were able to understand how to get the food quickly as if they'd had a regular night of sleep．Outside the migration season, they found the sparrows that got less sleep than usual had much more difficulty learning how to get the food treats than birds that had a regular sleep．

    The results show that the sparrows can deal with much less sleep during the migration season than usual．If scientists can find out why, they may learn from sparrows and find ways of helping people deal with getting much less sleep．Until scientists fully understand the relationship between sleep and learning, it's better to get plenty of sleep when preparing for an exam．

    Every year on 15th October, over 200 million people around the world take part in Global Handwashing Day. But why do we have a day for something we do all the time? Well, research shows that not enough people often wash their hands with soap. Experts believe that this leads to the deaths of millions of people every year.

    Sidibe, a public health expert says soap is the most beautiful invention in public health. Washing your hands with soap can have a huge impact on reducing (减少) the spread of diseases. Handwashing with soap prevents babies from getting ill and keeps children healthy in school.

    However, washing hands with soap does not happen as often as you might think. This is partly because there aren't enough resources (资源) in poorer countries, but it's also because for many people, handwashing is simply not part of their everyday life. It's not easy to get people to change habits they learned in early childhood -- but this is what Global Handwashing Day wants to do.

    In 2008, the Indian cricket team joined around 100 million Indian schoolchildren in washing their hands to promote (促进) the first ever Global Handwashing Day. Every year since then, many different events have been held around the world. In 2014, Global Handwashing Day was used in the fight against Ebola, a very serious disease, with events held in affected (受感染的) African countries.

    Today, local and national leaders continue to use the day to spread the message about the importance of clean hands. The hope is that handwashing becomes a necessary part of people's lives and improves the health of millions around the world.