Below is a selection from a popular science book.

    If blood is red, why are veins（静脉） blue?

    Actually, veins are not blue at all. They are more of a clear, yellowish color. Although blood looks red when it's outside the body, when it's sitting in the vein near the surface of the skin, it's more of a dark reddish purple color. At the right depth, these blood-filled veins reflect less red light than the surrounding skin, making them look blue by comparison.

    Which works harder, you heart or your brain?

    That kind of depends on whether you're busy thinking or busy exercising. Your heart works up to three times harder during exercise, and shifts enough blood over a lifetime to fill a supertanker. But in the long run, your brain probably tips it, because even when you're sitting still your brain is using twice as much energy as your heart, and it takes four to five times as much blood to feed it.

    Why do teeth fall out, and why don't they grow back in grown-ups?

    Baby (or “milk”) teeth do not last long; they fall out to make bigger room for bigger, stronger adult teeth later on. Adult teeth fall our when they become damaged, decayed and infected by bacteria. Once this second set of teeth has grown in, you're done. When they're gone, they are gone. This is because nature figures you're set for life, and what controls regrowth of your teeth switches off.

    Do old people shrink as they age?

Yes and no. Many people do get shorter as they age. But, when they do, it isn't because they're shrinking all over. They lose height as their spine（脊柱） becomes shorter and more curved due to disuse and the effect of gravity(重力). Many (but not all) men and women do lose height as they get older. Men lose and average of 3-4 cm in height as they age, while women may lose 5 cm or more. If you live to be 200 years old, would you keep shrinking till you were, like 60 cm tall, like a little boy again? No, because old people don't really shrink! It is not that they are growing backwards —- their legs, arms and backbones getting shorter. When they do get shorter, it's because the spine has shortened a little. Or, more often, become more bent and curved.

    Why does spinning make you dizzy（眩晕的）?

    Because your brain gets confused between what you're seeing and what you're feeling. The brain senses that you're spinning using special gravity-and-motion-sensing organs in your inner ear, which work together with your eyes to keep your vision balance stable. But when you suddenly stop spinning the system goes out of control, and your brain thinks you'removing while you're not.

    Where do feelings and emotions come from?

Mostly from an ancient part of the brain called the limbic system. All mammals have this brain area —- from mice to dogs, cats, and humans. So all mammals feel basic emotions like fear, pain and pleasure. But since human feelings also involve other, newer bits of the brain, we feel more complex emotions than any other animal on this planet.

    If exercise wears you out, how can it be good for you?

    Because our bodies adapt to everything we do to them. And as far as your body is concerned, it's “use it, or lose it”! It's not that exercise makes you healthy, it's more that a lack of exercise leaves your body weak and easily affected by disease

    Most Europeans want small cars. Many Americans prefer large cars. As a result, European automakers produce a large number of economical, light weight cars, while American automakers build bigger, heavier cars.

    The price of gas has much to do with this. The petrol is expensive in Europe, so Europeans naturally prefer cars that will go a long way on a small amount of fuel. There are other reasons. Many European cities have very narrow streets. In these cities a small car is more practical and easier to handle than a large one.

    Some Americans like powerful engines in their cars. They enjoy having wider cars that are comfortable for large families and long trips. They are prepared to pay higher costs to get these advantages. Other Americans, however, have learned to like the small and smart cars. Many visitors to Europe during and after World War I discovered that small cars were fun to drive and easy to park in small spaces. They were delighted to learn how far small cars could go on a few gallons of gasoline.

    In the 1950s many Americans began buying European cars. In 1957, for the first time, the United States imported more cars than it exported. The best seller among these imported cars was a cool-looking but small car from Germany. Americans immediately gave it another name “ the bug”.

    Today, American car buyers have a wider choice. There are big cars for people who want large room, comfort, and power. And there are small cars, mostly imported but some American-made, for people who want easy parking and economical operation.

    A new study, a project of the researchers from the University of Pittsburgh in Pennsylvania, finds the fitness tracker probably does not help with weight loss.

    The devices are designed to record your physical activity. They are usually worn around the wrist, where they measure a person's heart rate. The research team looked at two groups of individuals. The first wore a fitness tracker and took part in health counseling (咨询) with experts to consider the best weight-loss plan. The researchers compared this group with people who only got health counseling.

    The study found that those only speaking with the health experts lost nearly 6 kilograms, but those using a fitness tracker lost only 3.5 kilograms. John Jakicic, the lead researcher, questioned the use of electronic devices for weight control in place of "effective behavioral counseling for physical activity and diet."

    The study involved 470 subjects aged between 18 and 35. Some of them were overweight, while others were considered obese (肥胖的). Over three fourths of the subjects were women. All the subjects were told to increase physical activity and start on a low-calorie diet. They had their weight measured once every six months. After six months, researchers divided the group into two parts: one continued with monthly counseling, while members of the other group were given a fitness tracker. Eighteen months later, both groups "showed significant improvements in fitness, physical activity, and diet," with no major difference between groups. However, when it came to losing weight, the people who only spoke with experts lost nearly twice as much weight.

    Jakicic said, "the study's findings are important because effective long-term treatments are needed to address America's obesity." More information is needed, he added, to learn how to best use these devices to change "physical activity and diet behaviors" in adults who want to lose weight.

    There is a cry of anger, and a tennis racket crashes to the ground. Jake, age 7, has just lost another match and is now in tears beside the court. His sister Sally, just one year older, looks at her mother and rolls her eyes: it is hard to enjoy winning when this keeps happening. It is not an unusual situation, and it is one reason why many people argue that competition is bad for children. However, the truth is that competitive games are a valuable preparation for adult life.

    Games with winners and losers give children the chance to experience life's ups and downs. Take Jake, for example. Even though he is unhappy now, he will probably be smiling and laughing with his sister in a few minutes, just like the last time this happened. Gradually, he will learn that the world does not end when you lose a game. Eventually, he may even be able to lose with a smile on his face. This is an important lesson. Not everything in life goes the way you would like, and it is important to know how to handle disappointment when it occurs.

    Children who participate in competitive games develop qualities that allow them to succeed in the complex world of adult life. For example, one of the missions of the Youth Olympic Games is to inspire young people to adopt the Olympic values, which include striving, determination and optimism. Competition creates a desire to do better. Children have to learn to succeed in a competitive atmosphere in order to take advantage of opportunities in the future. Although it is possible to win by chance occasionally, people who win and keep winning work very hard to achieve their success.

    On the negative side, there are those who will say that competition actually encourages some values, which does happen. It is common to see sports competition in which the desire to win has replaced the desire to have fun. You may even see very young children playing violently—like the superstars they see on TV. While the bad behavior of young athletes is troubling, the problem is not the competition itself. In reality, the blame lies with the professional players who are bad role models for these children. In fact, a recent study of young athletes by the school of Physical Health Education at the University of Wyoming showed an improvement in mood after exercise, athletes were less depressed or tense.

    Of course, there are parents who argue that children of Jake's age are too young to handle the pain of losing. But whether we like it or not, adult life is very competitive, and keeping children away from competition does them more harm than good. If children do not learn how to compete, they will be defeated by people who can. It is an unfortunate fact of life: whether ten or a hundred people want the same job, there can be only one winner. Wouldn't you want your child to be that person?

    Backcountry for beginners: the best destinations in Canada

    When carried out safely, your first backcountry trip will leave you lifelong memories, opening a getaway into nature. But the leap from car camping to backcountry requires preparation and learning. Here are some recommended trips for backcountry beginners:

    Grundy Lake Provincial Park

    The park's 9 backcountry sites are a 30-minute paddle (划船) away. Grundy Lake is motor-boat free. Your sites are quiet enough for a true backcountry trip. Each site comes equipped with a fire pit (坑) and a picnic table.

    Bon Echo Provincial Park

    Many visitors don't know about the 25 canoe-in campsites located on Joeperry and Pearson Lakes. A short canoe trip of 30-minute will get you to your campsite. At each campsite, you will find a picnic table, tent space and a toilet nearby.

    Charleston Lake Provincial Park

    Experience the best of the Canadian Shield, and hike or paddle your way to 10 backcountry campsites. Travel time can range from 10 minutes to 2 hours. All sites come equipped with elevated tent platforms, a picnic table, a fire grill, and a toilet.

    Murphys Point Provincial Park

    Paddle through Big Rideau Lake (part of the historic Rideau waterway) to access 14 backcountry campsites. Most are located 5-45 minutes away from the boat launch. You'll find a picnic table, tent space, and a pit toilet nearby each site. Paddle back to visit Murphys' piece of living history: the Mica Mine!

    Remember: backcountry travel requires careful consideration of packing, route planning, meal planning, safety, and your skill level.

We credit Socrates with the insight that "the unexamined life is not worth living," and that to "know thyself" is the path to true wisdom.

But when it comes to introspection (内省), you might easily slip into the "rumination" (沉思) mode. This pattern is likely to cause you to become stuck in the rut of your own thoughts and absorbed in the emotions that might lead you to a wrong way. Research has also shown that people who are likely to ruminate are often at a substantially increased risk of depression.

Instead, scientific research suggests that you should adopt an ancient method favored by the likes of Julius Caesar, known as "illeism" which was coined in 1809 from the Latin "ille" meaning "he". The point of adopting this third person thinking is that such a small change can clear your emotional fog, allowing you to see your biases and helping you know the limits of your understanding of the problem at hand.

A study finds that illeism can also bring long-term benefits to wise reasoning (including elements like taking the perspective of others, recognizing uncertainty, and so on). The finding is the brainchild of Igor Grossmann, a psychologist. According to Grossmann, wise reasoning had long been considered too vague for scientific enquiry. In one of his earlier experiments, he established that as with IQ, the scores of wise reasoning could be achieved and were meaningful.

Grossmann's latest research team asked nearly 300 participants to describe a challenging social situation, and two psychologists graded them on different aspects of wise reasoning. The participants then had to keep a diary for four weeks. Each day, they had to describe a situation they'd just experienced, such as a disagreement with someone. Half were prompted to do so in the first person, while the others were encouraged to describe their situations from a third person perspective. At the end of the study, all participants repeated the wise reasoning test.

While the control group showed no overall change in their wise reasoning scores, those using illeism improved on their perspective taking and capacity to find a compromise.

Grossmann's work continues to prove that the subject of wisdom is worthy of experimental studies, indicating wiser reasoning is within everyone's power.