1．The existence of the giant clouds was virtually required for the Big Bang, first put forward in the 1920s, to maintain its reign as the dominant explanation of the cosmos.
　　【译文】巨大的宇宙云的存在，实际上是使二十年代首创的大爆炸论得以保持其宇宙起源论的主导地位所不可缺少的。

　　【析句】本句的主干为The existence of the giant clouds was virtually required for the Big Bang，过去分词短语first put forward in the 1920s在句中作后置定语，修饰前面的the Big Bang。

　　【讲词】Big Bang是天文学的一个名词，应该译成“大爆炸”或“大爆炸理论”。put forward意为“提出”。The Council has put forward valuable concrete proposals on energy conservation.（委员会提出了宝贵而具体的节能意见。）China has put forward three historical sites for UNESCO heritage list.（中国提交三个历史名胜申请成为联合国教科文组织的世界遗产。）
　　UNESCO的全称是the United Nations Educational,Scientific and Cultural Organization。

　　2．Astrophysicists working with ground based detectors at the South Pole and balloon borne instruments are closing in on such structures,and may report their findings soon.
　　【译文】天体物理学家使用南极陆基探测器及球载仪器，正越来越近地观测这些云系，也许不久会报告他们的观测结果。

　　【析句】本句为连词and引导的并列分句，主语为Astrophysicists，现在分词短语（working with ground-based detectors at the South Pole and balloon-borne instruments）是主语的后置定语，两个并列谓语分别为are closing in on such structures和may report their findings soon。

　　【讲词】to close in on意为“接近”或“快要”。AOL is closing in on launching video VoIP.（美国在线很快将推出网络视频电话。）Deadly bird flu virus is closing in on Europe.（致命的禽流感正在接近欧洲。）
　　ground based意为“陆基”，即基于陆地，也可以说land based。以类似方式组成的单词还有web-based（基于网络的；网上的），如web-based email system（网络在线电邮系统）。