NASA is required by law not to comment on unknowns that it discovers until the military has determined that they are not dangerous. So it remains silent on the wealth of evidence that it releases in the normal course of its operations, limiting itself to pointing out which objects are thought to be space debris and not commenting on the others. This video offers an outstanding compilation of NASA video, and illustrates the importance of changing the law, so that NASA can comment.

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http://www.youtube.com/watch?v=WlLN_Jcg1pc