The word “day” has two meanings. When we talk about the number of days in a year, we are using “day” to mean 24 hours. But when we talk about day and night, we are using “day” to mean the time between sunrise and sunset. Since the earth looks like a ball, the sun can shine on only half of it at a time. Always one half of the earth is having day and the other half night. A place is moved from day into night and from night into day over and over by the spinning(旋转) of the earth. At the equator(赤道) day and night are sometimes the same length. They are each twelve hours long. The sun rises at 6 in the morning and sets at 6 in the evening. For six months the North Pole is tilted(倾斜) toward the sun. In those months the Northern Hemisphere(半球) gets more hours of sunlight than the Southern Hemisphere. Days are longer than nights. South of the equator nights are longer than days. For the other six months the North Pole is tilted away from the sun. Then the Southern Hemisphere gets more sunlight. Days are longer than night. North of the equator nights are longer than days. Winter is the season of long nights. Summer is the season of long days.

      What's going to happen in the future? Will robots control our planet? Will computers become smarter than us? Not likely. But here are some things that scientists say are most likely to happen in 10 to 0 years from now, according to the BBC.

 Digital money      

      We used to pay with cash(现金) for everything we bought. Now when we use a credit card(信用卡) to shop online, money is spent without us seeing it. That means we are already using digital(电子的) money. Using a card is much easier than searching our pockets for change. It is also safer than carrying a lot of cash.    

When ATM cards were first introduced, they were not accepted everywhere. But now it's hard to live without them. It's reported that people in Sweden completely stopped using cash last year, and the US might be next.

Bionic(仿生的) eye    

It's no longer something only in a science fiction movie. People who are blind may have a chance to get their sight back—by wearing bionic eyes.

      A blind eye can no longer sense light, but a bionic eye can use a camera to “see” the environment and send data(数据) to the mind. Now the bionic eye only allows patients to see lights and unclear shapes. A high resolution(高清的) image could be just a few years away. 

Self-driving cars     

      Unlike a human driver, a self-driving car won't get distracted(分神) by a phone call, the radio or something outside the window. Sensors (探测器) and cameras on the car would allow it to stick strictly (严格地遵守)to the rules of the road and keep a safe distance from other cars. This would greatly reduce（减少） the number of road accidents. You could even take a nap while the car drives itself. In the future, driverless cars would be widely accepted.

      CHICAGO- Have you ever worked on your laptop computer with it sitting on your lap, heating up your legs? If so, you might want to rethink that habit from now on. Doing it a lot can lead to “toasted skin syndrome (症状)”, an unusual-looking spotted skin condition caused by long-term heat exposure (暴露), according to medical reports.

       In one recent case, a 12-year-old boy from California developed a skin discoloration on his left lap after playing computer games a few hours every day for several months. “He recognized that the laptop got hot on the left side; however, he did not change its position,” Swiss researches reported in an article published Monday in the journal Pediatrics.

      Another similar case is a Virginia law student who needed treatment for the spotted darkening on her leg. Dr. Kimberley Salkey, who treated the young woman, learned the student spent about six hours a day working with her computer placed on her lap. As Dr. Salkey later learnt, the temperature under the laptop could reach 51 degrees. That case, from 2007, is one of 10 laptop-related cases reported in medical journals in the past six years.

The condition can also be caused by overuse of heating pads (垫子) and other heat sources that usually aren't hot enough to cause burns. It's generally harmless but can also cause such permanent (永久的) skin darkening. In very rare cases, it can cause damage leading to skin cancers, said the Swiss researchers, Drs. Andreas Arnold and Peter Itin from University Hospital Basel. They do not mention any skin cancer cases linked to laptop use, but suggest, to be safe, placing a carrying case under the laptop if you have to hold it on your lap.

      Dr. Kimberley Salkey said that under the microscope, the affected skin is similar to skin damaged by long-term sun exposure.

      Major producers including Apple and Dell warn against placing laptops on laps or exposed skin for long periods of time because of the risks for burns. In the past, “toasted skin syndrome” has happened to workers whose jobs require being close to a heat source, including bakers and glass blowers, and in people who gathered near hot stoves to stay warm.

Dr. Anthony J. Mancini, chief at Children's Memorial Hospital in Chicago, said that it's unlikely that computer use would lead to cancer since it's so easy to avoid close skin contact (接触) with laptops.

    “Without music, life would be a mistake,” famous German philosopher(哲学家) Friendrich Nietzsche said over a century ago. Music is a big part of our lives. But in recent years, some US schools have cut music classes to control budgets(预算).

    For example, Chicago public schools hurt arts education when it fired(解雇)over 1,000 teachers. Among them, 10 percent of the teachers taught art or music, according to The Washington Times. In fact, this is not just a problem in the US. In other countries, such as China and the UK, music classes are not thought to be as important as ones like science, math and history. That's partly because music is not seen as a very important life skill, and it isn't tested. Many students are busy with schoolwork, so parents and students choose to focus on subjects that are tested more often.

    However, learning music is beneficial(有益的)in many ways.

    When playing music, you need different abilities to work together. It is not as simple as it looks, according to Kenneth Guilmartin of Music Together, an early childhood music development program. For example, when playing the piano, people see music notes and decode(解码)them in their brains. They also use their fingers to make sounds. You need to deal with all these things at the same time.

    Music has a special connection with science as well. You can see that many scientists are good at playing music: Einstein played the violin, and German physicist Max Planck was talented in playing the piano.

Why Do People Blink (眨眼) Their Eyes?

    People blink their eyes tens of thousands of times every day. Scientists have long believed blinking was an involuntary movement and served mainly to keep the eyeballs wet. But a new study suggests it has a more important purpose.

    An international team of scientists from the University of California at Berkeley studied the blinking of human eyelids. The journal Current Biology published their findings. The team said they found that blinking "repositions our eyeballs so we can stay focused" on what we are seeing. They said that when we blink our eyelids, the eyes roll back into their sockets—the bony area that surrounds and protects the eyes. However, the researchers found the eyes don't always return to the same position (位置). They said this causes the brain to tell the eye muscles (肌肉) to reorganize our eyesight.

    Gerrit Maus is the lead writer of the report. He serves as an assistant professor of psychology at Nanyang Technological University in Singapore. Maus said, "Our eye muscles are quite sluggish (迟缓的) and imprecise (不精确的), so the brain needs to constantly adapt (改编) its motor signals to make sure our eyes are pointing where they should be. Our findings suggested that the brain measures the difference in what we see before and after a blink, and orders the eye muscles to make the needed corrections." The researchers said that without such corrections our surroundings would appear unclear and even jumpy. They said the movement acts "like a steadicam (摄影稳定器) of the mind."

    The researchers said they asked volunteers to sit in a dark room while storing at a small dot on a flat surface. They used special cameras to follow the volunteer's blinks and eye movements. After each blink, the dot was moved one centimeter to the right. The volunteers did not notice this, but the brain did. It followed the movement and directed the eye muscles to refocus on the dot. After the dot was moved in this way 30 times, the volunteers' eyes changed their focus to the place where they predicted it would be.

    Professor Maus said. "Even though the volunteers did not consciously register that the dot had moved, their brains did, and adjusted (调整)with the corrective eye movements. These findings add to our understanding of how the brain constantly adapts to (适应) changes directing our eye muscles to correct for errors in our bodies' own hardware."