When it comes to the Internet, people talk about the password most. Actually, it's been under fire for a long time. Research has shown that passwords are not a very good way to protect sensitive information.

    People would use some random characters, numbers and symbols. Furthermore, a unique password would be used for every site or application the user uses. Unfortunately, the longer and more complex passwords become, the more people are likely to forger them. Therefore, they use the same password for every service or application. These are all big no-noes and essentially defeat the purpose of a password.

    Google is trying to kill off passwords on Android devices by introducing the Trust API, which does what simple passwords cannot and gives developers a framework for securing their application using a number of security systems and metrics(衡量标准)on the device. A Trust Score will be generated based on a number of metrics including your device location, face scanning, fingerprints, and the things like your typing speed or the way you speak. Taken one at a time, these metrics are not secure. But taken together, these metrics will help recognize the real “you”.

    The good news is that Google has already been testing this on real world data. Google has proven the Trust API works. Next Google will run tests will some banks to see if the Trust API meets their needs before rolling out the system on Android phones later. It may take another year for apps and popular sites to start using the Trust API.

    This is a pretty exciting change. Passwords have been around for a lone time. Although the security of systems has been improved, the usability of systems hasn't been proved much. Google appears to have the best of them. Maybe that never-ending conflict between security and convenience will be able to take a break once the Trust system comes out.

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    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

    Do you like shopping? Or does the thought of wandering round the shops fill you with terror? For some of us, shopping is an enjoyable way of spending our spare time and our money. For me, it's something I would rather avoid. Thank goodness for the Internet! It's more convenient to buy CDs, electrical items, and even food from the comfort of your sofa. But that's not the only reason: price is an important factor. We can buy goods and services cheaper online. But sometimes the problem is knowing what to buy. This has led to a type of shopping called “showrooming”.

    Showrooming is something I've done. I will go to a shop to see, touch and try out products but then go home and buy them online at a knock-down price. I'm not alone in doing this. Research by a company called Foolproof found 24% of the people showroomed at Christmas in 2013.

    Amy Cashman, Head of Technology at TNS UK, says the reasons for this new shopping habit are that people are lacking time, lacking money and they want security about the products they are buying. She explains that consumers are not only shopping online at home but they are using the Internet in store or on their smart phones to shop around.

    But does this mean technology will kill shops? Certainly shops will change. They will have to offer more competitive prices or encourage people to buy more by giving in-store discounts or free gifts.

    We mustn't forget that buying in a shop means you can get expert advice from the sales assistant and you can get good aftercare. It's good to speak to a real human rather than look at a faceless computer screen, but at least by showrooming, you get the best of both worlds.

    It is natural that young people are often uncomfortable when they are with their parents. They say that their parents don't understand them. They often think that their parents are out of touch with modern ways, that they are too serious and too strict with their children, and that they seldom give their children a free hand.

    It is true that parents often find it difficult to win their children's trust and they tend(倾向) to forget how they themselves felt when young.

    For example, young people like to act on the spot without much thinking. It is one of their ways to show that they have grown up and they can face any difficult situation. Old people worry more easily. Most of them plan things in advance, at least in the back of their minds, and do not like their plans to be upset by something unexpected.

    When you want your parents to let you do something, you will have better success if you ask before you really start doing it.

    Young people often make their parents angry with their choices in clothes, in entertainment and in music. But they do not mean to cause any trouble; it is just that they feel cut off from the older people's world, into which they have not yet been accepted. That's why young people want to make a new culture of their own, and if their parents don't like their music or entertainment or clothes or their way of speech, this will make the young people extremely happy.

    Sometimes you are so proud of yourself that you do not want your parents to say “yes” to what you do. All you want is to be left alone and do what you like. It is natural enough, after being a child for so many years, when you were completely under your parents' control.

    If you prefer to control your life, you'd better win your parents over and try to get them to understand you. If your parents see that you have a high sense of responsibility, they will certainly give you the right to do what you want to do.

    Volunteering abroad is a great way to help others, improve your skills and become a more confident, independent person. If you are interested in volunteering abroad, here are some places to go.

    Australia

    If you seek a life on the beach, in a great climate with friendly people, Australia might be your best bet. With thousands of volunteers already signing up to leave for Australia during the holidays, it will be a very popular option.

    Brazil

    This vast country has some great opportunities on offer and is especially popular this year. A lot of volunteer work is available in Brazil centers on conservation and ecological projects. With the world's largest rainforest in Brazil, of which huge part is in danger, there are lots of different jobs you can do.

    Kenya

    Kenya is the destination for those seeking an African experience. Generally volunteers in Kenya work in orphanages (孤儿院) or with local children living in slums (贫民窟). There is a great demand for volunteers in Africa because many people live in poverty, so if you truly feel like making a difference to a community, Kenya should be at the top of your list.

    Costa Rica

    Golden sandy beaches, clear coastlines and beautiful cities are what Costa Rica is all about. Because of its small size, you can see a lot of the country in just a short time. You can really make the most of your time as a volunteer. A lot of work is needed with wildlife and ecological work, so if you want to look after turtles (海龟) on the beach, Costa Rica could be just the place for you.

    About six years ago I was eating lunch in a restaurant in New York City when a woman and a young boy sat down at the next table. I couldn't help overhearing parts of their conversation. At one point the woman asked, "So, how have you been?" And the boy — who could not have been more than 7 or 8 years old —replied, "Frankly, I've been feeling a little depressed lately."

    This incident(小事件) stuck in my mind because it confirmed(证实) my growing belief that children are changing. As far as I can remember, my friends and I didn't find out we were "depressed" until we were in high school.

    The evidence of a change in children has increased steadily in recent years. Children don't seem childlike anymore. Children speak more like adults, dress more like adults and behave more like adults than they used to. Whether this is good or bad is difficult to say, but it is certainly different. Children as they once were on longer exists. Why?

    Human development is based not only on innate biological states, but also on patterns of access to social knowledge. Movement from one social route to another usually involves learning the secrets of the new status. Children have always been taught adult secrets, but slowly and in stages: traditionally, we tell sixth graders things we keep hidden from fifth graders.

    In the last 30 years, however, a secret-revelation (揭示)machine has been installed in 98 percent of American homes. It is called television. Television passes information indiscriminately to all viewers alike, be they children or adults. Unable to resist the temptation, many children turn their attention from printed texts to the less challenging, more vivid moving pictures.

    Communication through print, as a matter of fact, allows for a great deal of control over the social information to which children have access. Reading and writing involve a complex code of symbols that must be memorized and practiced. Children must read simple books before they can read complex materials.