英语语法分析

Since the early twentieth century, geophysicists have understood that the mantle churns and roils like a thick soup.

自二十世纪初以来，地球物理学家已经了解到地幔像浓汤一样搅动和翻滚。

Clearly, geophysicists who seek to explain and forecast changes in the field must understand what happens in the outer core.

显然，试图解释和预测磁场变化的地球物理学家必须了解外核发生了什么。

Geophysicists have long known that the source of the fluctuating magnetic field lies deep in the center of the earth.

地球物理学家很早就知道，地球磁场变化的原因深藏于地球中心。