【推荐1】Throughout history, great cities have risen and fallen. Some of them are seemingly lost in time — until artifacts (古物) are discovered that bring them back to life.

Teotihuacán

Located outside of Mexico City, Teotihuacán is thought to have been settled around 400 BC. By 400 AD, it was the most influential, powerful city in its region. Teotihuacán’s real treasure is its massive step pyramids. Much of the city’s history is still a mystery, but some believe that its decline came from changing climate conditions like long-term droughts.

Petra

This ancient city in southern Jordan flourished from the 4^th century BC to 106 AD. It was an important place for spice and silk trade routes. It also had a complicatedly-designed water management system. Petra was occupied by Rome in 106 AD, and the trade routes soon shifted. Hundreds of years later, earthquakes damaged the water system and Petra was abandoned.

Pompeii

Endless tales have been told about the tragedy of Pompeii, which occurred on August 24, in the year 79 AD, when the volcano Vesuvius erupted. The entire town was swiftly covered in ash and soil. Everything was frozen in time. The site was unearthed in the 18th century, and the evidence found provided a great detail of insight into daily living in this ancient Italian city.

Ctesiphon

Located about 20 miles outside of Baghdad, Ctesiphon was one of the greatest cities in Western Asia in the 6^th century. It was conquered (征服) by Rome, and then by the Byzantine Empire. In 637 AD, it was captured by the Muslims. Many believe that the ancient city was the inspiration for the city of Isbanir mentioned in the Thousand and One Nights folk tales.

Silk is a thin, yet extremely strong, fiber. It is made from protein that silkworms produce when they make their cocoons. Thousands of years ago, ancient Chinese craftsmen began weaving silk fiber into a soft, smooth fabric. A precious textile, silk was at first reserved for exclusive use by the Chinese imperial court. Chinese officials decided that silk-making methods must remain China’s secret.     1    

However, the existence of silk did not remain a secret. On diplomatic visits to neighboring rulers, Chinese envoys carried gifts of silk. By the first century BC, the Romans had become familiar with this exotic(异国情调的)luxury item.     2     Western rulers issued edicts (法令)that controlled silk prices. As in China, silk was designated a solely royal fabric. Trading for silk was principal motivation for merchants who searched for routes.

Over the centuries, different main routes developed.     3     Tradesmen travelling east or west could choose among routes that crossed many regions of Eastern Europe, the Middle East, Central Asia, and the Far East.     4     Trading vessels carried goods from China and Southeast Asia across Indian Ocean to Africa, India, and the Near East. Sea routes even reached Venice, Italy, by crossing the Mediterranean.

    5    

The Silk Road played an important role in bringing diverse cultures and peoples into contact. To make successful deals, merchants had to learn the languages and customs of the countries they crossed. As they journeyed along the Silk Road, people shared knowledge about arts, crafts, literature, science, and technologies. Over hundreds of years, cultures, languages, and religions influenced one another. Perhaps Chinese silk influenced history more extensively than any single famous person you can name.

【推荐3】French explorer Jacques Cartier is known mainly for exploring the St. Lawrence River and giving Canada its name.

Like many other European explorers, Jacques Cartier went to North America looking for gold and perhaps a shortcut to Asia.     1     It became France’s main route into Canada.

Jacques Cartier was born on December 31, 1491 in Brittany, a province of France. In about 1534, the king of France asked him to lead an expedition(远征) to the New World in search of riches and a new route to Asia.

    2     There he and his crew explored the land around the Gulf of Saint Lawrence and met Native Americans. When he sailed back to France, he took with him two Native Americans.

    3     This time, Cartier sailed deeper into the Gulf of Saint Lawrence and into the Saint Lawrence River. The two Native Americans he had taken before had learned French, and they served as guides. About 260 miles inland, Cartier reached the Native American village of Stadacona. Today, the city of Quebec stands near that place.

Cartier and his men were among the first Europeans to winter in what is now Canada.     4     After returning to France he reported tales told by the native people of treasures farther inland.

Cartier once again crossed the Atlantic in 1541.     5     When he returned to France in 1542, he was told that they were just the common minerals pyrite(黄铁矿) (fool’s gold) and quartz(石英).

【推荐1】Batman may not have any superpowers, but his inspiration certainly does.

More than 1,400 bat species live around the world, except in Antarctica and a few remote islands. Over their 50 million years of evolution, bats have developed clever solutions to life’s challenges, from a built-in sonar (声呐) system for finding food to fast, flexible wings that produce the fastest level-flight speed of any animal on Earth.

“There is still a lot to learn, but it is clear that bats really do have superpowers,” says Rodrigo Medellín, an ecologist. “Bats are showing us how to live a better life, for instance, by serving as models for healthy living and long lives.”

As a general rule in biology, smaller animals have shorter lives than larger ones. But bats are rule breakers: they’re the longest-lived mammals (哺乳动物) relative to their body size. Recently, scientists looked inside bats’ cells for the secrets to their exceptionally long lives. They focused on telomeres (端粒), which are the protective structures found at the ends of chromosomes (染色体). In most animals, telomeres tend to get shorter with age. But the telomeres of the longest-lived group of bats, Myotis, do not appear to shrink (收缩) with age. Understanding why bats live so long may help humans live longer one day.

In addition to living longer, bats remain healthy throughout their lives, with very low risk of developing cancer. Furthermore, bats can carry deadly viruses without getting sick. So further research into their unique immune (免疫的) systems may actually give insight into how people can live with viruses and not get sick.

Beyond their own abilities, bats also support many other parts of their ecosystems. Three out of every four bat species eat insects. Many are pests that cause damage to important agricultural crops, such as cotton. Scientists estimate that insect-eating bats may save U.S. farmers about 1 billion per year. In addition, many bat species help improve plant health and diversity.

“Bats are unsung heroes of biodiversity,” says Medellín. “It’s about time we appreciated them.”

【推荐2】U.S. forests could worsen global warming instead of easing it because they are being destroyed by natural disasters and are losing their ability to absorb planet-warming gases as they get older, a new Agriculture Department report says.

U.S. forests currently absorb 11 percent of U.S carbon emissions, or 150 million metric tons of carbon a year, equal to the combined emissions from 40 coal power plants, the report says. It predicts that the ability of forests to absorb carbon will start falling quickly after 2025 and that forests could emit up to 100 million metric tons of carbon a year as their emissions from rotting trees exceed their carbon absorption. Forests could become a “substantial carbon source” by 2070, the USDA report says.

The prediction suggests that the loss of forests as a natural carbon absorber will require the U.S. to cut emissions more rapidly to reach net zero, said Lynn Riley, a senior manager of climate science at the American Forest Foundation.

“Ten percent of our domestic emissions. That is a really significant portion,” Riley said. “As we work to decarbonize...forests are one of the greatest tools at our disposal. If we were to lose that, it means the U.S. will contribute that much more in emissions.”

The loss of cab on absorption is driven in part by natural disasters such as wildfires, tornadoes and hurricanes, which are increasing in frequency and strength as global temperatures rise. The disasters destroy forestland, disrupting their ecosystem and decreasing their ability to absorb carbon, Riley said.

Exploitation of forested areas, which the report projects will continue to increase, is having the same effect as people increasingly move to the so-called wild and urban interface.

The trees’ ability to absorb carbon weakens overtime. Older, mature trees absorb less carbon than younger trees of the same species, and the U.S. forests are rapidly aging, the report found.

More aggressive forest management can help by cutting down a small portion of aging forests to make ways for younger trees that absorb more carbon, Riley said. A thorough study of each forest should be done before removing older trees, Riley said, comparing forest management to prescribing the proper dugs to a patient.