Makes sure that you say so, " cial, " social.

确保你说是cial，社会。

This is called the “lookback time”, and it's a cru cial tool for cosmology: by observing very distant objects, we can see the Universe when it was young!

这叫做“回溯时间”，是宇宙学一个重要工具：通过观察非常遥远，看到宇宙年轻时样子！

In July, a fire at Iran's most important nuclear-fuel-enrichment site, which offi cials blamed on a bomb planted by Israel, inflicted enough damage to delay Iran's nuclear program by months.

今年7月，伊朗最重要核燃料浓缩设施发生火灾，造成破坏足使伊朗核计划推迟数月。官员将火灾归咎于色列安置炸弹。