A crow(乌鸦) is about twenty inches (英寸) long and black all over. Crows are dirty birds because they live on bad food. Crows eat a lot of waste food. In this way they are more useful to us than any birds. They clean up the dirty things in our streets. Crows are always hungry. They look for food all day, and in the evening you can see them in large numbers flying back to their nests(巢) in the trees. They sleep there at night.

    Crows are much noisier than other birds. Very often a large number of crows will get together on one house and talk. Sometimes they talk together, and sometimes they do it by turns(轮流) like human beings(人类). It is easy to tell(判断) from crow's sound if they are pleased or angry. Perhaps crows talk a lot because they are friendly birds. A pair of crows will live together all their lives, and if one of them dies, the other one becomes very sad and quiet for the rest of its life and some time later it dies too.

    Baboons(狒狒) live in Africa. They are like monkeys. Most people think daddy baboons don't know their babies. But scientists (科学家) find that daddy baboons know how to help their babies. The daddy baboons are smart.

    Joan Silk is a scientist. She studies the baboons for 3 years. She says the daddy baboons are happy to see their babies. They have big teeth to help the babies to eat hard things. Mother baboons are small. And they live in a place. When a mother baboon gives birth(分娩), she often has only one baby. Baby baboons have fur. They are very cute.

    During the day they eat things. At night, they sleep in the trees. Most children like baboons because they look like the man.

    As our closest neighbor in space, the moon has been the subject of popular legends, songs and poems since ancient times. And it also attracts scientists deeply.

    But even after centuries of research, many questions remain to be answered about the Earth's only satellite.

    Perhaps the Chang'e-4 lunar probe will be able to find out more of its secrets. On Dec 8, 2018 the probe lifted off from Xichang Satellite Launch Center in Sichuan province. It is the first probe to the far side of moon in human history.

    The Earth's gravity slows the moon's rotation, matching it to the speed of its orbit. Thus, the far side of the moon is always dark and has never been seen.

    It's this sense of the unknown that makes the far side of the moon such an interesting place for scientific and space exploration. Long exposed to solar winds, the far side may have the special soil and minerals in its upper mantle.

    For this reason, Chang'e-4 will study the effect of solar winds on the lunar surface and any minerals found beneath the probe. Chang'e-4 is also carrying flower seeds and potato and silkworm eggs to see whether life is possible on the moon. If it is, then the moon will become a more likely destination for space travel in the future.

    However, because of communication problems, exploring the dark side will not be easy. As the far side is blocked off from us, radio noise coming off Earth is also blocked. This is why China launched the relay satellite Queqiao in May, 2018, so that communication between Earth and the probe could go ahead.

    Power supply is also a challenge to the mission. Chang'e-4 gets energy from the sun through its solar panels. However, a lunar day has the length of 28 Earth days. It means that the probe will need to orbit the moon for over 20 days to be in a position to be able to land in moon daylight and so use its solar panels.

    According to Xinhua, theChang'e-4 lunarprobe landed on the far side of the moon on Jan 3, 2019 successfully, and everything goes well.

    The New York Times described the journey as "groundbreaking", and wrote that it would "give clues to the history and development of the moon".

    It's every parent's worst nightmare there's a fire in the house, the alarms are beeping, but the children are sleeping on. Now scientists have found a better way to rouse slumbering youngsters. Researchers in the US have discovered that playing a child a recording of his mother's voice is about three times more likely to wake him up than a traditional alarm.

    Writing in the Journal of Pediatrics, Smith and colleagues report how they compared the effects of four different smoke alarms on 176 children aged between 5 and 12 years old, none of whom had hearing difficulties or were taking any medication that affected their sleep. While one alarm featured a high-pitched beep the sort of commonly found in households the other three featured the voice of the child's mother calling either the child's name, giving instructions such as: "Wake up! Leave the room! ", or both. Each child slept in a lab-based room that resembled a real bedroom.

    The results show that vocal alarms appear to be more effective than high-pitched beeps. About 90% of children woke for a voice alarm compared with just over 53% for the traditional alarm.

    “High pitched beeping alarms don't wake up children well at all under about 12 years of age, "said Dr Gary Smith, a co-author of the research from the Nationwide Children's hospital in Ohio, although

he said at present it is not known why. He said it was important to look at developing better alarms.

    Prof Niamh Nic Daeid, director of the Leverhulme Research Centre for Forensic Science at the University of Dundee, said the research found a human voice combined with a low-frequency pulsing tone was far more effective in waking up children than a traditional high-pitched alarm. She also noted that more work was needed to explore whether other familiar sounds, such as a dog barking, might also prove effective in rousing children.

    Have you ever had trouble sleeping in a new place? Lots of people do. And now researchers from Brown University in Rhode Island think they know why. They found that one-half of the brain "remains more awake" than the other half when people are trying to sleep in a new place.

    The sleep findings were reported in Current Biology by Brown University. In their report, the researchers said many people report that they have a harder time sleeping the first night at a hotel or other places outside their home. They call it "first-night influence". "In Japan they say, 'If you change your bed, you can't sleep,'" said Yuka Sasaki, one of the report's writers. "You don't sleep very well in a new place. We all know about it."

    The researchers measured brain waves (测量脑波) for 35 volunteers over two nights in a laboratory. The two nights were a week apart(间隔).They found during the first night the left half of the brain was more active than the right half. This was during the first deep-sleep period, the researchers said.

    Sasaki said a lot of questions remain.

    Researchers did not keep measuring brain waves all night long. So, they don't know if the left half keeps "watch" all night, or whether it" works in shifts (轮换) with the right half later in the night" .They also do not know why the brain activity, at least during the first period of deep sleep, is always on the left half.

    For some, this research may be calming. It is good to know that our brain is "looking out for us" in a new place. But it may not help with sleep. That brain activity, at least according to this new research, makes it harder to get the sleep people need to wake up well rested in the morning.