If you need glasses to read this, you are among the majority of Chinese students. That's because most students in China are short-sighted which means they can only see things close up and distant things will be blurry. Four-fifths of high school students wear glasses and now more and more children in primary school need glasses, too.

    This epidemic of poor eyesight has two very simple causes: too much time spent indoors studying and too little time spent outdoors playing. Reading and writing for hours and hours, sometimes in poorly lighted rooms, causes eyesight to weaken. But students have to do this because there is so much pressure on them to succeed in school. And because they spend so much time indoors at school and at home, they have less time to spend outdoors enjoying the sun.

    The sun, as a consequence, is important in developing good eyesight. Exposure to daylight releases a chemical in the eyes that prevents, or at least delays, short-sightedness. According to a study by Ian Morgan of Australian National University, Australian children and Chinese children have the same level of eyesight before they start school, but once they enter primary school, Chinese children only spend about an hour a day outside, while Australian children spend three to four hours each day in the sunshine. The result is that while about 40 percent of Chinese primary school students need glasses, only three percent of Australian children do.

    Wearing glasses may not seem like a big deal. For some, wearing glasses can even be an opportunity to make a fashion statement. But poor eyesight at a young age can have serious long term consequences. As you get older, your eyesight can worsen and lead to things like macular degeneration(黄斑变性), a condition of the eyes for which there is no cure and which can eventually lead to blindness.

    With all that in mind, don't you think it's time to give your eyes a break? Try spending a little less time inside and go for a walk in the park, instead. It's the healthy thing to do and your eyes will thank you for it.

    Life-Changing Science Discoveries

    Here's a look at some discoveries that have changed the world. It's impossible to rank their importance, so they're listed in the order they were discovered

Micro-organism

    Before French chemist Louis Pasteur began experimenting with bacteria in the 1860s, people did not know what caused disease. He not only discovered that disease came from micro-organisms, but also realized that bacteria could be killed by heat and disinfectant(消毒剂). This idea caused doctors to wash their hands and disinfect their instruments, which has saved millions of lives.

Penicillin

    Antibiotics are powerful drugs that kill dangerous bacteria in our bodies that make us sick. In 1928, British Alexander Fleming discovered the first antibiotic, penicillin, which he grew in his lab. Without antibiotics, infections like strep throat could be deadly

DNA

    On February 28, 1853, James Watson of the United States and Francis Crick of England made one of the greatest scientific discoveries in history. The two scientists found the structure of DNA. Our genes are made of DNA and determine how things like what color hair and eye we'll have. In 1962, they were awarded the Nobel Prize for this work . The discovery has helped doctors understand diseases and may someday prevent some illnesses like heart disease and cancer.

X-rays

    Wilhelm Roentgen, a German physicist, discovered X-rays in 1895. X-rays go right through some substances, like flesh and wood, but are stopped by others, such as bones and lead. This allows them to be used to see broken bones or explosives inside suitcases, which makes them useful for doctors and security officers. For this discovery, Roentgen was awarded the first-ever Nobel Prize in Physics in 1901.

    Last week, two companies, Kitty Hawk and Uber, announced their plans to bring flying cars to reality very soon.

    Imagine never having to worry about traffic, stop lights, or road construction. A flying car would get to a place much faster than one travelling by road. On the other hand, imagine having to avoid drones (无人驾驶飞机) and other flying cars. Also, what if your battery dies when you are in the air? And, how will you know where to land?

    Kitty Hawk is a start-up tech company supported by Google co-founder, Larry Page. According to the Kitty Hawk website, its car will be able to travel at speeds up to 40 kilometers an hour in the air. It says under US aviation law such a machine “does not require registration or a pilot's license and may be flown in uncongested (不拥挤的) areas for recreational purposes.” As of now, the car can only be flown over fresh water.

    Kitty Hawk is making a list of people interested in buying the flying car. They must pay a deposit of US$100. Those who get their names on the list early will receive US$2, 000 off the final cost of the car. However, Kitty Hawk has not yet announced the price. Kitty Hawk expects its first flying cars will go on sale by the end of this year.

    At a conference last week, Uber announced plans for flying taxis to begin carrying passengers. Unlike the Kitty Hawk company, Uber does not plan to build its flying cars. Instead, it will use the resources of partner companies.

    Like the Kitty Hawk car, Uber flying taxis will use electric power. Uber says its flying taxis could travel up to 241 kilometers an hour. The company said that could reduce the travel time between San Francisco and San Jose, California from two hours on the road to 15 minutes in the air.

    Riders could use the Uber app to book a flying taxi to take them to their destinations. The company has not yet said how costly air taxi travel would be compared to road taxi travel.

    10-year-old Mikaila Ulmer from Texas is building a lemonade（柠檬水）empire, hoping to save honey bees in the process.

    It all started when Mikaila was 4 years old and she was bitten by a bee twice in one week. This caused her to become very scared whenever bees were near. In order to help her manage this new fear, Mikaila's parents asked her to do some research on bees. She learned that bees are quite important for flowers, gardens and trees. She also learned that they are dying at a rapid rate. In the past year, honeybee farmers have reported losing nearly 42% of them. Many believe that this could be due to the overuse of pesticides（杀虫剂）.

    This is when she set her mind to create a product to help save bees. She started her company BeeSweet Lemonade. Her special lemonade recipe came from her great-grandmother's cookbook. She adds honey to it, instead of sugar. In order to call attention to the problems honeybees face, Mikaila sells lemonade almost every day at her lemonade stand. And she takes every opportunity to tell her customers about the problems that face honeybees.

    What began as a small activity is starting to grow. BeeSweet is projected to sell almost 140,000 bottles of lemonade this year. BeeSweet lemonade can be found on the shelves at select Whole Foods Markets as well as many restaurants and other locations near her home.

    Does Mikaila have any time to just be a kid? Sure! Every weekend Mikaila does something fun. She doesn't mind the hard work though. She says that she is happy watching people enjoy her lemonade. The more people enjoy it, the more they're learning about the bees.

    Earthquakes happen without warning(前兆). They can happen any time of a day, at any point during the year. But don't worry because most are so weak that they cannot be felt. Only a few big ones hurt people. However, it's important to know what to do when an earthquake is happening.

    Do NOT go outside. You could get injured from falling glass or parts of buildings. If you are outside, stay away from buildings and power lines (输电线).

    Stay under a desk, table, or other strong furniture. Hold on to it. Or stay in a corner of the building. Cover your face and head with your arms and cover your mouth with a towel or clothing. Stay inside until shaking stops and it is safe to go outside.

    Keep away from windows, pictures or advertisements on the wall or the building, and anything else that could fall and hurt you. Most people get injured by falling things during an earthquake, not by the shaking itself.

    Also keep away from a fire. You could fall down and burn yourself on the fire.

    If you are driving when an earthquake happens, stop the car if it's safe. Stay inside your car until the earthquake stops, and don't drive near bridges. Try not to stop by power lines or trees. These could fall and hurt you.

    On a freezing cold day, a couple had to move into a small apartment because of their failure in business. The husband worked day and night to support the family but gave no care of his wife. So she thought, "He doesn't love me any more. He just cares about his business ... not me"．

    One day, she was about to take a shower when he stopped her at the door, "Let me take it first, okay?" "Why not me first?" she asked. "I am tired, honey, you take it later, okay?" She was entirely unhappy.

    One day, she found nothing to do and turned on his computer. A few words came into her sight. Reading them, she burst into tears. It was his diary：

    Today, I was quite sad. She asked me why I was always taking the shower first, and I said to her, "I was exhausted." She was unhappy. In her mind, I treated her not as well as usual, but what could I do? I was not as rich as before! We moved to the small apartment, and there was only one shower in the bathroom. It was so cold to take a shower in such a cold winter. But I found that if one person took the shower first, the room could get a little warmer. So every day I rushed to the bathroom first. I was thinking that, when she took the shower, the room would get warmer, even if it was only 1℃.

    Now I cannot give her a comfortable life, take her to good restaurants, or buy expensive dresses for her, but at least, I can give her 1℃ love.