There were too many people involved in the space program to be able to pull of a hoax like this. Too many people would have to remain silent on a coverup that big and there is just no way they could pull it off. For a conspiracy to work, you have to involve as few people as possible, which is something the 9/11 conspiracy nuts never take into account.
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The World is not dangerous because of those who do harm but because of those who look at it without doing anything.