Thufir Wrote:An interesting explanation of Fermi Paradox is in "The dark forest", the second part of Liu Cixin "Three body problem" trilogy.

MASSIVE SPOILERS!!!!

All civilizations try to expand, but the resources in the universe are finite. So sooner or later, there will be an interstellar conflict between civilizations. When you get in touch with an alien civilization, you never know if they are hostile, or not. There is really no way to determine if the alien species will destroy you or not, so the best course is to destroy them before they have a chance to destroy us. Of course they think the same way, so any civilization that announces its existence to the universe gets itself destroyed. So, in the words of Liu Cixin: "The universe is a dark forest. Every civilization is an armed hunter stalking through the trees like a ghost, gently pushing aside branches that block the path and trying to tread without sound. Even breathing is done with care. The hunter has to be careful, because everywhere in the forest are stealthy hunters like him. If he finds another life—another hunter, angel, or a demon, a delicate infant to tottering old man, a fairy or demigod—there’s only one thing he can do: open fire and eliminate them."