20世纪30年代,德国、日本和意大利军国主义势力在全球范围内日益扩张,整个世界陷入恐怖之中。德国的犹太科学家纷纷逃离家园。1938年从匈牙利逃到美国的科学家西拉德得知原子核可以发生裂变的消息后十分忧虑,他担心德国可能根据这一原理研制出核武器并用之于战争。于是,他一方面呼吁美国的核物理学家们不要轻易发表自己的研究文章,另一方面游说美国政府赶在纳粹德国之前研 In the 1930s, Germany, Japan, and Italy’s militarist forces were expanding globally and the entire world was in terror. Jewish scientists in Germany have fled their homes. The scientist who had fled from Hungary to the United States in 1938, Sirard, was very worried after learning that the atomic nucleus could undergo fission. He feared that Germany might develop nuclear weapons based on this principle and use it for the war. So, on the one hand, he called on the US nuclear physicists not to publish their own research articles easily. On the other hand, he lobbied the U.S. government to study before Nazi Germany.