Extraterrestrials 【1】 Let we suppose that if we were met Aliens once day, it may be the four kinds of situations: The first, high civilization and benevolent; The second, high civilization and evil; The third, low civilization and benevolent; The forth, low civilization and evil. I analyze the forth situation at first. Maybe we would have no any communication with each other, we would just investigate their lives like treating the animals on the earth; The third situation, it would be hard to say. Probably, it would like our history of discovery the new continent of America or like the movie of《Avatar》. We would bring a strong influence to them. Whether it would do good more than harm or reverse, it would be difficult to definite. In relative terms, we should hold the initiative;