It is hard to explain what is important about something that most people never will understand.
对人们无法理解的事物，向他们解释这种事物的重要性，是一件极为困难的事。
Observations of a distant galaxy cluster collision reveal a core of invisible matter devoid of glittering galaxies-something that is hard to explain by current theories.
对遥远的星系团碰撞进行观察后，发现了一个不可见物质的核心，然而其中没有星光闪烁的星系，这用目前的理论是难以解释的。
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