3 . Bookstores are fascinating places. That’s because the books on the shelves can take you away to magical lands, help you learn a foreign language, or cook a delicious meal. But when your community is too small to house a real brick bookstore, sometimes you have to make a compromise. A mobile bookstore that brings books around the country was the result. That is the case for Rita Collins, 70, who dreamed of opening a used bookstore after retiring from teaching.

A business planning class from the American Booksellers Association convinced Collins to abandon her idea that opening a bookstore in the small town where she lives, which would not be sustainable. Eureka, Montana, located just seven miles from the Canadian border, only has a population of 1,517. Collins asked her instructors about a traveling bookstore on wheels and they were skeptical. But she persevered.

Collins was inspired by Dylans Mobile Bookstore, a traveling bookstore in Wales run by Jeff Towns. She contacted Jeff for advice but she was largely on her own when it came to building her bookstore. First, she had to find a vehicle large enough to stand in. Then she had to have it refitted with shelves that would hold the books at a 15-degree angle so that they would stay in place while in transit. Collins named her bookstore St Rita’s Traveling Bookstore, which has been on the road since 2015.

At first, she drove through Montana and then she made her first cross-country trip in 2016. After she retired in 2017, it became a full-time job all year round. Collins and her mobile bookstore have visited 30 states, stopping at festivals and events along the way. While the locations change, some things always stay the same. Collins loves meeting people and making connections. While she loves what she does, Collins doesn’t think she can keep doing it. In several years, she hopes to pass her traveling bookstore onto another bibliophile who shares the same interest and will keep it on the road.

5 . It’s common knowledge that the woman in Leonardo da Vinci’s most famous painting seems to look back at viewers, following them with her eyes no matter where they are in the room. But this common knowledge turns out wrong.

A new study finds that the woman in the painting is actually looking out at an angle of 15.4° off to the viewer’s right — well outside the range that people normally believe when they think someone is looking right at them. In other words, said the study author, Horstmann, “She’s not looking at you.”

This is ironic (讽刺), because the entire phenomenon of a person’s gaze (凝视) in a photograph or painting seeming to follow the viewer is called the “Mona Lisa effect”, which is absolutely real. If a person is illustrated or photographed looking straight ahead, even people viewing the portrait from an angle will feel they are being looked at. As long as the angle of the person’s gaze is no more than about 5 degrees off to either side, the Mona Lisa effect occurs.

Horstmann and his co-author were studying this effect for its application in the creation of artificial-intelligence avatars (虚拟头像) when Horstmann took a long look at the “Mona Lisa” and realized she wasn’t looking at him.

To make sure it wasn’t just him, the researchers gathered 24 people to view images of the “Mona Lisa” on a computer screen. They set a ruler between the viewer and the screen and asked the participants to note which number on the ruler intersected (相交) Mona Lisa’s gaze. To calculate the angle of Mona Lisa’s gaze as she looked at the viewer, they moved the ruler farther from or closer to the screen during the study. Consistently, the researchers found, participants judged that the woman in the “Mona Lisa” portrait was not looking straight at them, but slightly off to their right.

So why do people repeat the belief that her eyes seem to follow the viewer? Horstmann isn’t sure. It’s possible, he said, that people have the desire to be looked at, so they think the woman is looking straight at them. Or maybe the people who first coined the term “Mona Lisa effect” just thought it was a cool name.

8 . It could be said that the northernmost part of our planet holds the secrets of our past as well as our future.

Through our exploration of the Arctic, scientists have discovered more about the biodiversity (生物多样性) of the area as well as how to preserve Earth’s ecosystems. Yet as one of the most severe but most primitive (原始的) places on Earth, the Arctic has been affected by human activities---research and exploration, booming tourism and above all, global warming---in recent decades.

Jonathan Smith, producer of the BBC documentary Blue Planet II, shared his filming experience in the Arctic. “We were all set and ready to film but we needed two major things---walrus (海象) and ice. I had expected that walrus may be hard to find, but I didn't expect it to be hard to find ice,” he told the BBC. “The crew was all commenting on how surprisingly warm it was.”

They were not mistaken. Scientists have been recording changes in the Arctic. Its sea ice minimum in summer, for example, has reduced by 40 percent in the past 30 years, NASA data showed. These changes have had bad influences on the Arctic and the human, animal and plant life that calls it home.

But the effects of these changes are not limited to the inhabitants of this area alone. In fact, it could be said that the weight of the world relies on this icy region. The Earth’s steady climate depends on the Arctic’s sea ice, which acts as a huge white reflector (反光体) at the top of the planet, bouncing some of the sun’s rays back into space. The more Arctic sea ice melts, the less light is reflected, and the more the dark oceans will absorb the sun’s radiation. The Arctic also helps circulate ocean movement, moving cold and warm water around the globe.

With visible changes in the global climate, the Arctic has given us a wake-up call---what happens “up in the North” doesn’t just stay there. It comes with a high cost to the world at large. It's time for us to pay attention to this chilly region and learn more about what’s happening there, as well as its past and possible future.

10 . Modern agriculture and its ability to feed billions of people may be one of humanity’s greatest achievements. However, it comes with hidden costs. For example, have you ever considered how much water is needed to provide you with a steak or a salad? It may surprise you.

In a recent study published in the journal Nutrients, scientists from the Commonwealth Scientific and Industrial Research Organization (CSIRO), took a close look at the diets of 9,341 adult Australians – specifically, their “water-scarcity (缺少) footprints”.

The water-scarcity footprint is a widely recognized measurement of water consumption（消耗）. First, it counts the liters of water you used. Then, it looks at the place where the water was used. Using a liter of water in the desert is not the same as using a liter of water in a tropical (热带的) rainforest. The more scarce water is in your area, the larger your water-scarcity footprint.

The scientists found that the average Australian’s diet had a water-scarcity footprint of 362 liters per day. Snacks and beverages – cookies, cakes, sodas and alcohol – accounted for 25 percent of the water-scarcity footprint. The research also included a glass of wine (41 liters), a single serving of potato chips (23 liters), and a small bar of milk chocolate (21 liters). Not surprisingly, cutting out snacks would be the NO.1 priority if you wanted to lower your own water-scarcity footprint.

Climate change is causing droughts and extreme weather. In 2018, Cape Town, South Africa, nearly ran out of water due to a drought. Its freshwater reservoir(水库) stayed at just above 13.5 percent of full capacity. By 2030, a world of about 8.6 billion people will need 35 percent more water, and 50 percent more food, according to the United States National Intelligence Council.

So, we need to watch what we eat, not just for our personal health but for the health of our societies.