Anyone who has ever played the game of Tetris (俄罗斯方块) knows the game's surreal ability to spill into real life. After you shut off the game, you still see those Tetris blocks falling in your mind. You're grocery shopping and find yourself thinking about rearranging items on grocery shelves. Your mind continues to play the game, even when you're physically not.

    Robert Stickgold, a Harvard professor, noticed something similar after a day hiking a mountain. That night, he dreamt he was still going through the motions of mountain hiking. Curious about this, he tried something: he got a group of college students of various skill levels to play Tetris and let them sleep in the Harvard sleep lab.

    Over 60% of the students, including those who suffered from amnesia (健忘症), reported dreams of images of Tetris pieces falling, rotating (旋转), and fitting together. Interestingly, half the Tetris expert students reported such Tetris dreams, while 75% of the beginners did.

    A study found that playing Tetris can grow your brain and make it more efficient. Adolescent girls played the game for an average of 1.5 hours a week over three months. The cerebral cortex (大脑皮层) of the girls grew thicker, while brain activity in other areas decreased. Richard Haier, who had found that there was a "Tetris learning effect", in which the brain consumed less energy as mastery of the game rose, concluded, "The brain is learning which areas not to use."

    Haier's study showed that as the girls practiced playing the game, nerve cells made connections, communicating through synapses (a synapse is a connection between two nerve cells). When you learn something, you change those connections. Every time you reactivate(激活) a circuit, synaptic efficiency increases, and connections become more durable and easier to reactivate. Stickgold says sleep plays a role in this memory process.

    So to sum up, whenever you do specific tasks over and over again, they take up less of your brain power over time. And that's pretty amazing.

    A couple from Miami, Bill and Simone Butler, spent sixty-six days in a life raft (救生艇)in the seas of Central America after their boat sank.

    Twenty-one days after they left Panama in their boat, in Simony, they met some whales (鲸). "They started to hit the side of the boat," said Bill, "and then suddenly we heard water." Two minutes later, the boat was sinking. They jumped into the life raft and watched the boat go under the water.

    For twenty days they had tins of food, biscuits, and bottles of water. They also had a fishing line and a machine to make salt water into drinking water—two things which saved their lives. They caught eight to ten fish a day and ate them raw(生的).Then the line broke. "So we had no more fish until something very strange happened. Some sharks(鲨鱼) came to feed, and the fish under the raft were afraid and came to the surface. I caught them with my hands."

    About twenty ships passed them, but no one saw them. After fifty days at sea their life raft was beginning to break up. Then suddenly it was all over. A fishing boat saw them and picked them up. They couldn't stand up. So the captain carried them onto his boat and took them to Costa Rica. Their two months at sea was over.

In the movie, The Day After Tomorrow, many climate changes including an ice age are caused by global warming. Much of the science in the movie has been questioned by people. However, there may be some truth to the idea in the movie that global warming could cause an ice age.

The theory starts with an understanding of why Europe and Scandinavia are not colder already. After all, other places at the same latitude(纬度) are covered with ice. The ocean current called the Gulf Stream brings warm waters from the Caribbean to the UK and Europe. These waters warm the countries around their path. This is why the UK, Europe and Scandinavia have a warmer climate than Alaska. Global warming has nothing to do with this. Global warming is significant. It could slow the Gulf Stream, or even stop it. If this were to happen, the cold waters would stay in the area of Europe, the UK, Scandinavia and the Northeastern US. It could mean an ice age for those regions.

Some weaknesses in the Gulf Stream could happen for different reasons. These days, it could happen due to global warming, caused by human activities, such as the burning of fossil fuels.

If a new ice age happened, it would probably be caused by the melting of the polar ice. This will lead large quantities of cold and fresh water to come into the ocean, which would disrupt the Gulf Stream and cause the cooling of many areas that now have a mild climate.

Scientists have gathered a lot of data from the oceans and the land to try to determine whether an ice age could be caused by global warming. With all this information at hand, it appears that it is indeed possible that global warming could lead to an ice age.

Smoking is harmful.But as soon as you quit the habit, everything will be OK,right?Wrong.

New research has found that even if you give up smoking, the damage it has done to your genes will stay there for a much longer time.In the research, a team of US scientists studied the blood of 16,000 people.Among them, some were smokers, some used to smoke, and the rest were non-smokers.Scientists compared their genes and found that more than 7,000 genes of smokers had changed--a number that is one-third of known human genes.

According to NBC News, both heart disease and cancer are caused by genetic changes.Some people may have had the changes when they were born, but most people get them in their day-to-day lives while doing things like smoking.

When you stop smoking, a lot of these genes will return to normal within five years.

This means your body is trying to heal (治愈) itself of the harmful effects of smoking.But the changes in some of the genes stay for longer.They can stay for as long as 30 years.It's almost like leaving a footprint on wet cement (水泥)—it will always be there,even when you've walked away and when the cement becomes dry.

Although the study results may make people unhappy, there is a bright side:the findings could help scientists invent medicine to treat genetic damage caused by smoking or find ways to tell which people have heart disease or cancer risks.

Young people are spending more time in digital spaces. The Internet allows us to connect with people, share ideas, be creative, have fun and discover new things. Unfortunately, young people also face risks online. Common problems include cyberbullying（网络欺凌）, receiving unwanted messages, seeing images and content you don't want to see, or having your private information or photos shared without your permission.

Safer Internet Day（SID）is organized in the second week of February every year, and over 180 countries take part. The aim is to raise awareness of online issues and make the Internet a safer place. SID invites everyone to be part of a big conversation about online issues. This is particularly important for teenagers because they often experience unpleasant situations online, but they don't always feel they can talk about them.

Cyberbullying is when someone uses the Internet to embarrass, threaten or hurt another person. If you experience cyberbullying, talk to an adult you trust as soon as possible. Don't reply to any messages but save the evidence.

Going online often means spending time alone. When you feel down, social media can make you feel lonelier. Using social media might be related to higher levels of depression. So you need healthy social media use.

Whatever app you use, make sure you know who sees your posts and personal information. Limit what people can see, decide who can comment on your content and thwart other users' comment. It may be illegal to share a photo or video of someone without their permission. The SID's website has advice about what to do if someone shares pictures of you that you feel embarrassed about.

There is still a lot we don't know about how time spent online affects people's well-being. But talking about all the issues helps everyone understand common problems and know how to deal with them.