Astronomers must infer the existence of black holes, which are invisible, from their gravitational influence on the visible bodies surrounding them.

天文学家必须从黑洞对周围可见天体的引力影响推断出不可见的黑洞的存在。

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The poet says there are many visible or invisible walls in the world that have no necessity of existence.

诗人认为，那些有形的或无形的墙，在世界上已经没有必要存在了。

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Therefore, these mysterious matters are invisible, but astronomers know about their existence through the exploration of the gravitational interaction between them and ordinary matters.

因此这些神秘的物质是看不见的，但天文学家通过探测它们和普通物质之间的引力相互作用得知了它们的存在。

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" The killer's rambling letter read, in part: "I am not forgetting revenge for the compulsory education that has produced me as an invisible existence.

CNN: NEWSMAKERS

First and foremost is the question of how the invisible background field tied to the existence of the Higgs came to be and why it has the properties it does.

CNN: Higgs and the holy grail of physics