6 . Many families take their children on vacation. They will usually travel for a few days or weeks during school breaks. But Mr and Mrs Smith have planned a longer vacation with their two children. The Smith family is on a one-year trip around the world, and they planned to visit 30 countries in all. Right now, the four travelers are about halfway through their trip.

Mrs Smith says they are trying to see as much of the world as they can. Mr Smith says one of the most interesting experiences of the trip has been meeting new people. He says people have been extremely friendly, very welcoming and love their kids. Eleven-year-old Tyler says he has enjoyed learning about the people they have met. He says, “I learned in Africa that people have very different lifestyles.” His sister, Kara discovers that she likes Thai food. Mrs Smith says that the trip teaches the children a lot.

The Smiths made good preparations for the trip. They did a lot of research, choosing destinations and arranging accommodations. Mr Smith uses unpaid leave. They carry small bags filled with lightweight clothing and whatever else they need. Mrs Smith says she enjoys being able to carry everything she needs on her back. “What has become important is making unforgettable memories as a family and taking ‘those’ with us instead.” The Smiths will continue to head east for the next six months.

9 . In the Hollywood movie The Martian, actor Matt Damon plays an astronaut who grows food on Mars (火星) to survive alone on the red planet.

After seeing the movie, Washington State University physicist Michael Allen and University of Idaho food scientist Helen Joyner decided to carry out a case study helping students figure out how to farm on Mars. In the case study, students had to imagine they were mining on Mars and decide how to feed themselves there before starting on the journey. They got advice from Allen and Joyner on how to select crops and take the challenges of growing crops over long periods on Mars. Students used a scoring system to select three foods to plant on Mars.

Allen found the results impressive: among 30 students, “no two people have ever gotten the same answer”, he said.

Human travelers to Mars will likely have to make use of resources on the planet rather than take everything they need with them on a spaceship. This means farming their own food on another planet, one that has a very different ecosystem (生态系统) from Earth’s.

One challenge for those who would like to live on Mars is the fact that there can be no farming tools. Like real astronauts, students taking part in the study cannot take farming tools with them. As Joyner put it to his student astronauts, “You are starting with nothing.” Besides, students also have to deal with a very limited choice of diet. “If you had to eat a single food for the rest of your life, could you do it?” Joyner asked.

But Allen believes the case study is about more than farming and eating on the Red Planet. “I’m not teaching about growing food on Mars,” Allen said, “I’m teaching about living with choices. I’m teaching about problem solving.”