【推荐1】Since I was born and brought up in a rural town, I have a great interest in nature. Having the chance of studying abroad in my second year at college, I decided to go to Canada just because I wanted to see the beautiful phenomena there. So after I finished the study, I went to Yellowknife in the Northwest. I clearly remember the sixth night in Yellowknife. Suddenly my host mother came to my room around 8 p. m. and told me to change clothes and go outside quickly carrying her camera.

The northern lights were flickering (闪烁) in the sky! I was amazed and just stood there with my mouth open. I forgot to take pictures of the mysterious lights.

Since that night, whenever it was sunny, I went outside at night and looked at the sky. It was so cold that my hands and feet were numb (失去知觉的) with cold. Actually, the time of my being able to be out was limited. I had to bring her camera back to the house in one hour at most, for the camera was going to be broken because of the cold temperature.

As I took pictures of the northern lights, I came to find a characteristic movement of the lights. They first appear in the north part of the sky and then they come down to the south. After that, suddenly, they come in the middle of the north and south only for a while, which is the time when the best northern lights can be seen. Since it is only a few seconds for the northern lights to come down to the middle of the sky, it is very hard to get good pictures.

The stronger the sun acts, the better and stronger northern lights flicker in the sky. That’s because they occur from the collision (碰撞) between atmospheric gases and solar wind. Much more solar wind comes to the earth when the sun is active, leading to the best northern lights.

【推荐2】NASA aims to send a man and a woman to the moon by 2024. This is the goal of its Artemis program. But for Artemis to succeed, the U. S. space agency first needs to solve a big problem: the damaging threat of moon dust.

Over billions of years, celestial （天体的）bodies, such as asteroids and meteors, have slammed into the moon. These hits have crushed some lunar rocks into dust. The surfs radiation gives the dust an electric charge that makes it stick to everything. Those powdery bits are like ^u broken pieces of glass" , notes Mihaly Horanyi, a physicist at the University of Colorado Boulder. The dust is so rough, in fact, that it can damage equipment. If taken in, it might even harm an astronaut's health. Horanyi is part of a team that has now figured out how to overcome one troubling aspect of the dust: its static cling, using a low-powered electron beam （电子束）.When shined onto the dust, that beam sends the dust flying.

During the 1970s, the astronauts in NASA's Apollo missions relied on a very low-tech system to clean lunar dust off their spacesuits. They swept it away with what looked like the brushes used to paint a house. But the electrically charged nature of space dust tended to fail such hand sweepers.

The new electron-beam broom takes advantage of the dust's electrical characteristic. As the beam hits the dust, it releases electrons into the tiny spaces between particles. Some of these negatively charged electrons will be absorbed by the surrounding dust.

One problem with the electron beam, at least for now, is that it leaves up to one-fourth of the dust behind. The Boulder group aims to strengthen that cleaning power. Horanyi says the electron beam is just one of several ways future space explorers could keep surfaces clean. Others might include changes to a spacesuit's design.

【推荐1】Volunteering is a great way to help your community. It is something that people should be doing more often, because it is a great way to help out those less fortunate. Another reason that you should volunteer is that it has a lot of health benefits, which people don’t seem to really know about.     1    .

Reduce depression (抑郁)

Volunteering is a great way to decrease depression, especially if you are someone who doesn’t have a great support system at home.     2    . When you are volunteering, you are around other people often talking and laughing, which helps reduce depression.

    3    

A lot of volunteering involves packing boxes or moving things, and that is very good for your heart. You can actually walk the dogs and clean cages at a local animal shelter, which are all ways to stay active. If you are volunteering to do something you love, you may not even notice that it takes a great deal of physical energy, so it’s much better than just working out because you enjoy it.

Make you feel satisfied (满意的)

When you do voluntary work, you feel this satisfaction out of what you are doing, because you know you are helping other people. When you feel this satisfaction, your mental and physical health improves, and you just feel better overall (全面的).     4    . And this is something that volunteering provides.

Reduce anxiety

    5    . When you start volunteering, you find new ways to communicate with other people. It helps reduce your anxiety levels. It can help you find ways to interact with others and can help you build confidence around others.

【推荐3】Utah Lake is, in a word, disgusting. The State of Utah has worked with many partners and spent millions of dollars in an attempt to restore Utah Lake. It has indeed produced some active effects.   However, due to the wastewater getting into it，this body of water is rich in   nutrient and home to water bloom.   Overfishing and the introduction of invasive species have only made the problem worse. In the summer of 2016，500 people in Utah complained about their headaches, skin rashes and discomfort after swimming in the lake.

The Utah Lake Restoration Project is headed by Parker.   He imagines a beautiful lake dotted with man-made islands where a community could be built.   Parker frequently goes to Capitol Hill to push for the proposal of the comprehensive lake restoration. Parker follows his rules "big ideas are worth approaching"，as the project calls for lake digging, the creation of islands，the removal of invasive species to restore the habitats of native plants，fish and so on.

Speaking of the Utah Lake Restoration Project，Ben Holcomb said, "It is not quite in line with reality.” He added，"Despite impressive computer models and the current project report， the Utah Lake Restoration Project lacks the actual field research to show that this project will have a positive effect on the lake's ecosystem.”

When asked how the public would help beautify Utah Lake, the lake's official workers suggested picking up garbage. However, it has a greatly limited effect on the overall health of the lake. Parker's plan may seem like the state's best chance to restore Utah Lake, but in reality the Utah Lake Restoration Project lacks the facts necessary for this sort of proposal. The State of Utah should propose some suggestions for the revision of the plan and offer the Utah Lake Restoration Project the access necessary to conduct research which could be compared with their theoretical findings. Only then can the State of Utah make an educated decision on behalf of people and resources.

【推荐2】It is believed that human story begins in Africa and ends about 200,000 years later with their seven billion descendants (后代) spread across the Earth, living in peace or at war, their faces lit by campfires and computer screens.

In between is an exciting tale of survival, movement, isolation, and conquest, most of it occurring before recorded history. Who were those first modern people in Africa? What routes did they take when they left their home continent 60,000 years ago to expand into Europe and Asia? When and how did humans reach the Americas? For decades, the only proof was found in a small number of scattered bones and artifacts that our ancestors left behind on their journeys. In the past 20 years, however, DNA technologies have allowed scientists to find a record of ancient human migrations in the DNA of living people.

“Every drop of human blood contains a history book written in the language of our genes,” says population geneticist Spencer Wells. The human genetic code, or genome, is 99.9 percent identical throughout the world. But while the bulk of our DNA is the same, what’s left is responsible for our individual differences — in eye color or disease risk, for example. On very rare occasions, a small change, called a mutation, can occur, which is then passed down to all of that person’s descendants. Generations later, finding that same mutation in two people's DNA indicates that they share the same ancestor. By comparing mutations in many different populations, scientists can trace their ancestral connections.

These ancient mutations are easiest to track in two places: in DNA that is passed from mother to child (called mitochondrial DNA, or mtDNA for short), and in DNA that travels from father to son (known as the Y chromosome, the part of DNA that determines a child will be a boy). By comparing the mtDNA and Y chromosomes (染色体) of people from various populations, geneticists can get a rough idea of where and when those groups separated in the great migrations around the planet.

【推荐2】Kyle Cassidy and three other members of the Annenberg Running Group were stretching on the grounds of the University of Pennsylvania, waiting for a few latecomers. The Penn colleagues and other community members meet three days a week for a roughly 30-minute jog and an occasional lecture. That's right― during some runs, one of them delivers a talk. Topics range from the brain to Bitcoin.

But on this day last January, it would not be their normal run. The first clue that something was off was the man who sprinted past them. "Running at an amazing pace," Cassidy told Runner's World admiringly. Cassidy discovered why the sprinter was so fleet of foot when another man ran by, yelling, “Help! He took my phone and laptop!"

At that, the group did what running clubs do: They ran, trailing the suspect down the streets of Philadelphia until he ducked into a construction site. The runners split up. Cassidy ran around to the far side of the site to cut the thief off while the others wandered the neighborhood hoping he had dumped the loot （赃物）in a backyard.

No luck. So they decided to ask residents whether they'd seen the guy. When they knocked on the door of one row house, they were in for a surprise. Unknown to them, he had already emerged from the construction site—and was hiding behind a bush by that very house. As the owner opened the door, the suspect darted out from behind the bush ... and right into the arms of campus police, who'd joined the chase shortly behind the runners.

The members of this running group are not hard-core athletes. But they do understand the benefit of a little exercise. ''Running is typically a useless sport where you turn fat cells into heat," Cassidy told The Philadelphia Inquirer. "But occasionally it can be useful, and here was one of those opportunities."

【推荐3】London Tours and Cruises

Explore London with these top London tours to see the city from a different perspective. With the London Pass you can enjoy all of the below tours for free, so whether it is by land. water or on two feet, there are plenty of ways to get around and see the capital. From guided tours to walking tours, you’ll experience the sights like never before.

Hop-On Hop-Off Bus Tour

Drive through the streets of London on an iconic hop on hop off bus tour. It’s one of the best ways to see the sights and with a choice of three routes around the city you’re guaranteed to see all the major landmarks and attractions. Just jump off and on as you will and tailor-make your own sightseeing experience.

Thames River Cruise

See the sights of London from a unique perspective on one of the best river tours down the Thames. The Thames River Cruise is one of our top 10 experiences in London and it's worth it! See the Houses of Parliament, Big Ben, Tower of London and pass under Tower Bridge. too. You can even take the tour right down into Greenwich.

Shakespear’s Globe Theatre Tour

Learn about the history of the Bard at the Shakespeare’s Globe Theatre Tour. This Elizabethan-style playhouse is a replica (复制品) of the original which burned down in a fire. Learn more about the fascinating world of Shakespeare, his huge body of works and life on stage in the 16th century.

London Bicycle Tour

Take to the streets of London on two wheels with the London Bicycle Tour company. Go off the beaten track with a guided tour and wind your way through the streets of London learning about the tales of the town and its rich history.