We want to explore and try to better understand the world in which we live. Space exploration is one of the ways.Through the exploration of space, we can begin to unravel the mysteries of our universe, and to better know our living environment.

      Space exploration provides us with knowledge about the beginning of our solar system, our own planet and ourselves. It also helps answer the questions that have puzzled us for many years. Solar system exploration is important because it is good for us.

      Space technology has become an important part of our daily lives. Some technology uses satellites to communicate. Satellites are also used to examine the changes in the Earth's climate and seas, for weather report and for military. We also use satellites in food production. Because of the use of space technology in crops, fewer and fewer people will suffer hunger.

        The space program provides a chance for nations to work together. The cooperation(合作) promotes peace and understanding between governments and their people. Many governments have taken part in the space technology, including the United States, Russia, Japan, the European nations and India. In the near future, other nations will take part in it. In fact, the United States remains the leader in new space technology.

    Sheridan is a town in Indiana, USA. There are lots of trees near the public schools in the town. Their leaves turn sunlight into energy（能量）.

    In Sheridan, the sun not just provides energy for plants. It keeps schools running, too. The schools use solar panels（太阳能电池板） to turn sunlight into energy.

    The science behind solar energy is not new. But Sheridan Community Schools is the first school district(学区) in Indiana to be completely solar-powered. The district finished putting in solar panels for all three of its schools in 2016. Some of the panels can turn to follow the sun across the sky.

    In 2008, fewer than 1. 000 schools used solar power. By 2014, there were 3, 727 schools with solar panels in the USA. These numbers come from a report by the Solar Foundation. Roxie Brown, a program director there said that the number of schools with solar panels has continued to go up since 2014.

    Solar energy has some advantages over other energy sources(来源). Sunlight is a renewable source, which means it won't run out. Solar panels don't harm the environment. Also, sunlight is free. So by using solar power, schools can save money on energy costs.

    Brown thinks more schools should run on solar energy. "The sun is Earth s energy source," she says. "We're trying to make it the energy source for our houses cars and schools, too."

    But using solar energy isn't always easy. Solar panels can be expensive to put in. The panels also take up space. But for many schools, going solar is worth it.

    What can 3-D printers*make? They can make lots of things, such as toys and car parts. But what about a house? In the Netherland 3-D printed houses will soon come into life, according to The Guardian

The Netherlands is the first country to have this technology*.

    Scientists plan to build five houses with 3-D printers. The first house will be finished by the end of 2019. It will be a house with three bedrooms. For the first house, only the walls will be 3-D printed. A 3-D printer will print it with a special cement. The printer will print it layer upon layer to build the walls. After that, workers will make the wall stronger.

    By the time they start working on the fifth house, the scientists hope that most parts of the house will be made with 3-D printing. Even the windows can be made with a 3-D printer.

    The 3-D printed houses have many advantages. For example, they use less cement than traditional houses. It can help save a lot of money. Also, 3-D printing can make buildings in almost any shape*. Traditionally-built homes usually come in just a few shapes