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How do we know black holes exist?
Light can't escape a black hole--which means technically they are invisible, right? So how do scientists know they exist?

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Asked by Linda Saturday Apr 26th 2008 in Trivia
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a black object does not reflect light back to our eyes (which makes us 'see' an object and know that it exists).... but we know that black object exists. of course, we dont have to have something visible to know it exists... there are laws of physics which can prove the existance of matter.. or antimatter ... or does-not-matter-since-you-asked-this-question almost-4-years-ago-and-probably-have-moved-on.

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Black holes can't be seen directly. But we can see the effects they have on objects and matter around them. When a black hole passes near a star or through a cloud of gas and dust, the matter "falls" into the black hole. As it falls, it heats up and gains energy. Once the matter reaches a certain temperature, it starts to give off X-rays. Because the X-rays are given off before the matter falls into the black hole, it escapes--and it can be detected.

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