Can you imagine a sea of sand three times bigger than India? This is the Sahara Desert. It covers 11 countries in North Africa and is over 9 million square kilometers in area. That’s more than 25% of Africa.

In the Sahara, temperatures are very different during the day and at night. During the day, the hottest time is between 2 p.m. and 4 p.m., when temperature rises to 33°C. But it is very cold at night —the coldest time is at 4 a.m., when temperatures fall to -1C. The Sahara is very dry. The average precipitation (降水) in a year is only 70 millimeters.

Because of the extreme temperatures in this desert, it is a very difficult place to survive. Marco Rivera has some tips.

Take warm clothes and a blanket. During the day, cover your body, head and face. Clothes protect you from the sun and keep water in your body. You will also need a warm blanket at night. It can get cold very quickly. When the temperature drops, it can be a shock and make you feel even colder.

You can use your car tires (轮胎) to make a fire. A fire is easy to see. It will help people find you and it will keep you warm at night.

Try to drink some water once every hour. You need your water to last as long as possible. Drink only what you need. When you talk, you lose water from your body. Keep your mouth closed and do not talk.

If you eat, you will get thirsty and drink all of your water more quickly. You can eat a little, but only to stop you from feeling very hungry. Eat very small amounts of food and eat very slowly. You can live for three weeks with no food, but you can only live for three days if there’s no water.

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Do you want to improve your physics and chemistry grades? Well, maybe you should first learn something about the struggles（奋斗）of great scientists.

The American Psychological Association（美国理学会）did an interesting study. More than 400 students in New York City took part in it. The students were divided into three groups. Group 1 read a typical textbook that describes the accomplishments（成就）of great scientists. Group 2 read about those scientists’ personal struggles. For example, as a Jew （犹太人）， Einstein escaped from Nazi Germany to avoid persecution. The last group read about the scientists’ intellectual struggles, like Marie Curie’s failed experiments. These stories about struggles also told students how the scientists dealt with these major obstacles（障碍）.

The students took a science test before the study. After the six-week study, they took another. Scientists found those in Groups 2 and 3 improved their science grades. Students in Group 1 didn’t see a grade increase. Some of them even had lower grades after the study.

The study was led by Xiaodong Lin-Siegler, a professor at Columbia University. According to Xiaodong, kids often think Einstein was born a genius(天才).They believe they will never match him.

Many of them fail to realize that any success requires a long journey. Along the way, there are many failures.

Students who read the struggle stories were more likely to say great scientists were like themselves. The “great minds” also had to overcome obstacles to achieve success .

Xiaodong says today's science textbooks fail to bring science to life. As a result, students hardly treat science as part of their everyday lives. Instead, they just see a long list of facts that they have to remember. Xiaodong thinks textbooks should include more stories about how great scientists had to struggle to succeed. And they should focus(聚焦）more on how these scientists responded(回应）to the obstacles they met along the way.