In 1901, H.G. Wells, an English writer, wrote a book about a trip to the Moon. When the explorers(探索者) landed on the Moon, they found that the Moon was full of underground cities. They showed their surprise to the "Moon people". The "Moon people" also showed their surprise. "Why are you traveling to outer space when you don't even use your inner space?" They asked.
H. G. Wells could only think of traveling to the Moon. In 1969, human beings did Land on the Moon. People today know that there are no underground cities on the Moon. However, the question that "why are you traveling to outer space when you don't even use your inner space?" is still an interesting one. More and more scientists are thinking about it.
Underground systems(系统) are already here with us. Many cities have underground car parks. In some cities, such as Tokyo, people can find large underground shopping areas. Tunnels(隧道),like the one called Chunnel between England and France, is now in use.
But what about underground cities? A Japanese company is building a kind of underground city, called "Alice Cities". The builders are thinking about using outer space for public parks and using underground space for flats, offices and so on.
Some people say that building down under the ground but not building up in the outer space is a good way to use the Earth's space. We may use outer space for farms, parks and gardens in the future. H.G. Wells's "Moon people" would agree. Would you?
