1 . The Silk Road is arguably the most famous long-distance trade route of the ancient world. This passage connected Europe in the West with China in the East, and allowed the exchange of goods, technology, and ideas between the two civilizations. Although merchants could make huge profits travelling the road, it was not without risk.

The main Silk Road started in Chang’an (known today as Xi’an), the early Han capital. Travelers commencing their journey from this city could take a northern route that would take them across China’s northwestern provinces. After this, they would face the Gobi Desert, arguably the greatest danger of the Silk Road.

The Gobi Desert, the largest desert in Asia, consists mainly of rocky, hard earth. This feature made it easier for traders to travel across, compared to sandy deserts like the neighboring Taklamakan Desert. Like other deserts, the Gobi Desert is dry and hot, and therefore the biggest challenge travelers faced was obtaining enough water for themselves as well as for their camels.

So, rest stops were created along the route, allowing travelers to rest, eat and drink. These places also promoted the exchange of goods, and even ideas, amongst the travelers who stopped there. Usually, the rest stops were placed within a day’s journey of each other. In this way, travelers could avoid spending too much time in the desert, which would make them targets for robbers, another danger of the Silk Road.

Once through the Gobi Desert, travelers would continue their journey into Iran, Turkey, and finally Europe. While this part of the journey may have been less dangerous, it is not entirely without its perils (风险).

3 . To understand the effect of ice melting (融化) around the world we first have to understand what an ice sheet actually is. Covering 5.4 million square miles in Antarctica (南极洲) and 656,000 square miles in Greenland, an ice sheet is actually a huge land of ice from the Ice Age. These sheets form in areas where snow that falls in winter does not melt entirely over the summer. This ice, home to different species of animals, is now melting at a rate that cannot support the life it currently holds.

Many of these creatures rely on ice sheets as land for resting, hunting and protection, yet as the size decreases, they are forced out of their homeland in search of other land on which to live. Often this means journeys to search for food and an imbalanced ecosystem happens when different species are forced together onto the coast.

Since the 1990s, the deer population has dropped by 56 per cent—climate change has caused warmer temperatures over winter setting off rainfall instead of snow, which freezes more quickly underfoot and makes it harder to walk and search for food. In the summer, frozen layers of land melts and releases trapped diseases which bring death to animals. A similar situation has fallen on the polar bears who suffered a 40 per cent population loss between 2001—2010.

Quite apart from these problems, the threat of sea levels rising if the ice caps were to disappear is approaching. If the Greenland Ice Sheet melted, the sea level would rise around six meters, and if the Antarctic Ice Sheet melted, sea levels would rise by around 20 feet. As a matter of fact, sea levels have risen about eight inches since 1880, three of which we’ve gained over the last 25 years. This seemingly small amount has already caused dangerous flooding, loss of farmland and more deadly storms.

While we’re still a long way from losing the ice sheets all together, we’ve already lost too much and if we don’t take climate change seriously now, we will certainly hit the point of no return.

6 . There are around 100 tribes(部落)that live in global isolation, mostly in South America and India. The Sentinelese have lived on one of the Andaman Islands in Eastern India for 60, 000 years. They protect their island by fighting against people from outside. Their language is different from any other known language. Another Andaman tribe is the Jarawa. In the past, they were independent and fought against anybody trying to make contact with them. But in 1998, the Indian government built a road across their land, and since then, they’ve had more contact with the outside world.

Some Amazon tribes avoid contact because of unhappy memories. The Mashco-Piro left their vegetable gardens after rubber companies killed most of their tribe at the beginning of the 20th century. Those who survived became nomadic(游牧的)and started hunting animals in the forest.

The Awa live in the Amazon forests ofBrazil. Out of 350 members, 100 have no contact with the outside world. They left their villages and adopted a nomadic lifestyle around 1850 to escape attacks by Europeans. In the following years, farmers in nearby communities started cutting the trees to expand their farmland. The Awa lost most of their hunting land. The few Amazon tribes that still exist are fighting to keep their traditional way of life.

Survival, an organization that fights for the rights of tribal people, says that uncontacted tribes are the most vulnerable(弱势的)humans on the planet and that’s why their environment should be unavailable to the rest of us. After years of pressure, the organization got Brazil’s government to clear non-natives from the Awa land. All non-Awa people are leaving so the tribe can get their forest back.

But some think it's impossible for tribes to stay isolated forever in a connected world. Contact will be made one day. So the question is：Whose choice should it be, ours or theirs?

7 . Deep in the middle of Sri Lanka, a massive column of rock reaches out from the green tropical forest. It is 660 feet tall and features frescoes (壁画), graffiti, and landscaped gardens.

The rock is known as Sigiriya and holds a special place in the island's cultural history.

It was established as the stronghold of a king over 1,500 years ago, and today the Sigiriya complex stands as one of the earliest preserved examples of ancient urban planning.

Located in the Central Province, the column of rock is somewhat central to the country. The rock is known as Sihagiri, meaning "Lion Rock", a nod to the giant animal carved from stone which greeted visitors at the entrance.

In 476 BC. King Dhatusena ruled over Sri Lanka. One of his illegal sons, Kashyapa, wanted the throne (王位). Kashyapa overthrew Dhatusena and drove his brother Moggallana to Southern India. Kashyapa crowned himself king in 477 BC.

King Kashyapa chose Sigiriya as his palace because its position was an advantage to the defensive stronghold, offering fantastic 360-degree views. Plans to build a city quickly unfolded and after several years, the Sigiriya complex had become a business center for the new King.

Sigiriya was both a palace and a fortress (堡垒); the overall complex featured five gates and measured just under 3 km by just over 1 km. The site plan consisted of a fort，an upper palace on the top of the rock,and lower palaces at ground level. The king also constructed gardens throughout，and for protection a river with walls surrounded the complex.

Frescoes decorate the western side of the rock, along with the mirror wall, a brick face covered in a highly-polished white plaster. When new, the wall was said to be able to produce Reflections.

Over time the Mirror Wall became a graffiti board, covered in verses written by visitors. Known as "Sigiri Graffiti", some of the messages date to the 8th century CE.

8 . By the end of the century, if not sooner, the world’s oceans will be bluer and greener thanks to a warming climate, according to a new study.

At the heart of the phenomenon lie tiny marine microorganisms(海洋微生物) called phytoplankton. Because of the way light reflects off the organisms, these phytoplankton create colourful patterns at the ocean surface. Ocean colour varies from green to blue, depending on the type and concentration of phytoplankton. Climate change will fuel the growth of phytoplankton in some areas, while reducing it in other spots, leading to changes in the ocean’s appearance.

Phytoplankton live at the ocean surface, where they pull carbon dioxide(二氧化碳) into the ocean while giving off oxygen. When these organisms die, they bury carbon in the deep ocean, an important process that helps to regulate the global climate. But phytoplankton are vulnerable to the ocean’s warming trend. Warming changes key characteristics of the ocean and can affect phytoplankton growth, since they need not only sunlight and carbon dioxide to grow, but also nutrients.

Stephanie Dutkiewicz, a scientist in MIT’s Center for Global Change Science, built a climate model that projects changes to the oceans throughout the century. In a world that warms up by 3℃, it found that multiple changes to the colour of the oceans would occur. The model projects that currently blue areas with little phytoplankton could become even bluer. But in some waters, such as those of the Arctic, a warming will make conditions riper for phytoplankton, and these areas will turn greener. “Not only are the quantities of phytoplankton in the ocean changing. ” she said, “but the type of phytoplankton is changing.”

And why does that matter? Phytoplankton are the base of the food web. If certain kinds begin to disappear from the ocean, Dutkiewicz said, “it will change the type of fish that will be able to survive.” Those kinds of changes could affect the food chain.

Whatever colour changes the ocean experiences in the coming decades will probably be too gradual and unnoticeable, but they could mean significant changes. “It’ll be a while before we can statistically show that the changes are happening because of climate change,” Dutkiewicz said, “but the change in the colour of the ocean will be one of the early warning signals that we really have changed our planet.”

9 . Scientists today are making greater effort to study ocean currents (洋流). Most do it using satellites and other high­tech equipment. However, ocean expert Curtis Ebbesmeyer does it in a special way — by studying movements of random floating garbage. A scientist with many years’ experience, he started this type of research in the early 1990s when he heard about hundreds of athletic shoes washing up on the shores of the northwest coast of the United States. There were so many shoes that people were setting up swap meets to try and match left and right shoes to sell or wear.

Ebbesmeyer found out in his researches that the shoes — about 60,000 in total — fell into the ocean in a shipping accident. He phoned the shoe company and asked if they wanted the shoes back. As expected, the company told him that they didn’t. Ebbesmeyer realized this could be a great experiment. If he learned when and where the shoes went into the water and tracked where they landed, he could learn a lot about the patterns of ocean currents.

The Pacific Northwest is one of the world’s best areas for beachcombing (海滩搜寻) because winds and currents join here, and as a result, there is a group of serious beachcombers in the area. Ebbesmeyer got to know a lot of them and asked for their help in collecting information about where the shoes landed. In a year he collected reliable information on 1,600 shoes. With this data, he and a colleague were able to test and improve a computer program designed to model ocean currents, and publish the findings of their study.

As the result of his work, Ebbesmeyer has become known as the scientist to call with questions about any unusual objects found floating in the ocean. He has even started an association of beachcombers and ocean experts, with 500 subscribers from West Africa to New Zealand. They have recorded all lost objects ranging from potatoes to golf gloves.