【推荐1】Monarch butterflies(黑脉金斑蝶) are a common summer sight in the northern United States and Canada. These large orange and black insects brighten parks and gardens as they fly lightly among the flowers. What makes monarchs particularly interesting is that they migrate—all the way to California or Mexico and back. They are thought to be the only insect that does this.

Every year in the late summer monarchs begin their journey to the south. Those heading for Mexico go first for the Louisiana-Mississippi area, then fly across the Gulf of Mexico into Texas. Once in Mexico, they settle themselves in one of about fifteen places in a mountain forests filled with fir tress. Each place provides a winter home for millions of monarchs. The butterflies are so many that they often cover entire trees. When spring comes, they begin their long journey north.

The question is often asked whether every butterfly makes the round-trip journey every year. And the answer is no. The average monarch lives about nine months. So one flying north might lay eggs in Louisiana and then die. The eggs of that generation may be found in Kentucky; the eggs of the next generation may end up in Wisconsin or Michigan. The last generation of the season, about the fourth, will make their way back to Mexico and restart the journey.

Scientist learn about monarchs’ migration by catching and making marks on the insects. By recatching a monarch with such a mark and noticing where it came from, the next scientist can get to know things like the butterfly’s age and its routing.

【推荐2】Sharks are among the best swimmers on the planet, but a new research suggests that even they sometimes “hold their breath” while diving deep underwater. The reason is that sharks are cold-blooded and their body temperature matches the waters they swim in. To do deep dives, they must maintain body heat, and the best way to do that is to close their gills (鳃).

Royer, a leading researcher at the University of Hawaii, set out to study the diving habits of hammerheads sharks. They’re known for swimming in warmer coastal waters, but earlier studies showed they can also dive to over 800 meters below the surface. At those cold depths, the water temperature falls to as low as 5℃.

For these sharks, the fall in temperature is a matter of life and death. Because a shark can’t produce its own body heat, it begins to freeze the deeper it goes. Its muscles, eyes and brain become sluggish (迟钝). If it gets too cold, it can’t swim. And if it stops swimming, water doesn’t go across its gills. It can’t breathe and will eventually drown (溺亡).

How is it that hammerheads are able to go down into these deep depths and survive? To find out, Royer and his colleagues caught the fish and attached an electronic sensor to each shark. The sensor would release itself from the shark’s body after several weeks. The data they found amazed them: The sharks dived, spent just a few minutes at depths and then they shot towards the surface. They closed their gills and kept water out of their gills so that their body wouldn’t cool down.

“Unlike animals with lungs, the sharks don’t return to the surface to breathe. Instead, they simply go to a depth where it’s warm enough for them to feel comfortable and reopen their gills. Hammerheads are probably not the only species doing so. Our work is another example of how new electronic sensors help to explain the extraordinary ability of these animals across 400 million years of changing ocean environments,” Royer said.

【推荐3】Polar bears generally use sea ice to hunt (捕猎), but a newly discovered group has found another way. An isolated (与世隔绝的) population of polar bears has been discovered in a fjord (峡湾) in southeast Greenland, which is free of sea ice for most of the year. Polar bear generally need sea ice to survive, so the discovery is raising hopes that some kinds of the polar bears might survive the loss of sea ice caused by global warming.

Researchers found the population living in a fjord in the southeast Greenland, which is surrounded by mountains and an ice sheet to the west, and ocean to the east. The sea-ice coverage lasts for only around 100 days each year. With sea ice in the fjord becoming smaller because of global warming, the whole group were expected to die out by the end of this century.

But the isolated population has found a way to hunt without sea ice. The group, about 27 adult females, has been isolated from other polar bear populations along Greenland’s east coast for at least 200 years.

Tracking data from marked bears proves that they don’t move far. For example, when members of the group went out of the fjord, the ice on which they sat sometimes got caught in the rapid water flow. “Whenever this happened, they would get stuck and then, they would have to jump off, swim to the beach and walk back home empty-handed,” says lead author Kristin Laidre, an animal ecologist at the University of Washington in Seattle.

Though the researchers failed to video their hunting without sea ice, the existence of this small population in conditions of low sea-ice coverage suggests there is a chance that the population can survive, even as sea ice flows away to farther north each year.

【推荐1】Right now you should know about two ways to represent numbers, as Roman numerals and Arabic numerals. Plus, people in other countries use different symbols for numbers. With all these different symbols, how can math be a universal language?

Math is a universal language because the principles and foundations of math are the same everywhere around the world. Ten plus ten equals twenty if you write it as Arabic numerals 10+10=20 or Roman numerals X+X=XX. The concept of 20 items is the same no matter where you are in the world.

And, what about geometry(几何)? A circle is always a circle and its circumference (周长) is always calculated the same way no matter where you are in the world. The same holds true for any other figure like triangles, squares or rectangles.

We like to visit other countries to experience new scenery, new foods and a different culture. It’s fun to watch documentaries about festivals that we don’t have in North America. There is a great deal of cultural diversity in the world that we can enjoy and celebrate. But math is one thing that is common to everyone.

Different countries use different units of measurement; for example, the United States and the United Kingdom use inches and feet while the rest of Europe uses metric measurements of centimeters and meters. But no matter what the units are, everyone must measure the house that they are building. Houses everywhere, whether they are square or round, are built using the same mathematical equations(方程式).

The principles of probability are the same everywhere as well. The chance of rain in Guatemala might be greater than the chance of rain in the Sahara Desert but probability works the same way. People around the world have different genes but the probability of passing on genes to their children follows the same mathematical rules.

It is easy to see that no matter how diverse different cultures are, math is one common language across the world.

【推荐2】While climbing the Great Wall is a once-in-a-lifetime dream for many, Jim Spear has taken it a step further, spending the last 18 years as a villager residing beneath this ancient wonder.

“Never did I dream I would have the chance to visit the Great Wall, let alone live under it,” said 68-year-old Spear, a self-taught architect from the United States.

Spear’s interest in China began during his college days. It deepened when he met Tang, a Chinese girl, in 1980, and they got married two years later. In 1986, he decided to drop out of his doctoral studies in Chinese politics at the University of California and moved to China “to get to the heart of things”. “I realized that if I became a scholar of China, based overseas, I wouldn’t be able to experience what was happening in China,” Spear said.

In 1995, the couple secured a long-term rent of a traditional village farmhouse in Mutianyu and decided to make it their full-time home ten years later. Shortly after possessing full-time village life, he rented an abandoned schoolhouse and transformed it into a restaurant and art glass factory for a sustainable tourism business. He also turned a former factory into a hotel and helped renovate (翻新) over 20 households into restaurants. Besides, he explored other ways to support those residents in rural areas. “I want to do something for them,” Spear said.

Spear’s designs reflect his natural talent for fusing (融合) traditional and modern elements, adopting the Great Wall style. However, Spear emphasized his approach involves creating designs and views “that echo (呼应) the Great Wall, not copy it”. In 2014, Spear received the Great Wall Friendship Award from the Beijing government.

Talking about the future, Spear sees abundant possibilities in China, driven by significant domestic demand and a growing emphasis on preserving historic structures.

【推荐3】In this room at Microsoft’s headquarters in Redmond, Washington, all sound from the outside world is locked out and any sound produced inside is stopped cold. It’s called an ‘anechoic’ (无回声的) chamber (室), because it creates no echo at all. This is the world’s quietest place.

The room offers a very rare experience. “As soon as one enters the room, one immediately feels a strange and unique sensation which is hard to describe,” wrote Hundraj Gopal, a speech and hearing scientist and the principal designer of the anechoic chamber at Microsoft, in an email. “Most people find the absence of sound deafening, feel a sense of fullness in the ears, or some ringing. When you turn your head, you can hear that motion. You can hear yourself breathing and it sounds somewhat loud,” he said. In the real world, Gopal explained, there is always some air pressure on the ear drums. But upon entering the anechoic room this constant air pressure is gone, since there are no sound reflections from the surrounding walls.

Microsoft’s chamber is currently registered in the Guinness World Record as the world’s quietest place, a title it claimed in 2015 at the expense of a similar chamber at Orfield Labs in Minneapolis. But unlike Microsoft’s, that chamber is open to the public, which has turned it into a small tourist attraction.

Despite rumors to the contrary, there is no “world record” for time spent in the chamber constantly by a person, and such challenges are not encouraged, according to Orfield, who constructed his own lab and anechoic chamber. And he has rejected many requests from people who want to “beat the record.”

Anechoic chambers are generally used to test noises and sounds coming from a variety of products with a high degree of scientific reliability. Microsoft uses it for audio equipment such as microphones, receivers, headphones and speakers, or to analyze clicks and hums from computing devices like keyboards, mice, fans and so on. Since the chamber at Orfield Labs is the only officially approved one in an independent lab in the United States, it attracts an even wider range of businesses and products: medical defibrillators, sleep-apnoea machines, hearing aids, heart valves, appliances, automotive parts, computers and hard drives.