Alien Invasion (Space)
Further Info: Just started this one, and it's full of black pills, fucko.
If an Alien Invasion came from outer space, you wouldn't know about it. You would be dead approximately .005 nanoseconds after it began.
Why?
Well, there are a huge number of reasons. This isn't like "Independence Day," "The War of the Worlds," "Star Trek," or some other fantasy you have cooked up in your mind. This is a species that is capable of intergalactic travel. This means they are, more than likely, vastly more advanced than beings from Earth.
Just like you are (arguably) more intelligent than a chimp, an invading alien force would be orders of magnitude more evolved than human beings are.
There won't be a need for them to use lasers, nukes, nerve gas, or anything like that. They might not even need to be in the same solar system as the Earth is. Think about it. If they are able to cross the vast emptiness of interstellar space, they probably can fire an armada of microscopic nanobots that are set to kill while they are passing us by on the way to a restaurant in Andromeda. We wouldn't even see it. We would just be removed.
They might be so more advanced than us, that once they discover our dumb asses, they could just think us out of existence.
We Should Shut Up
Since the invention of radio, we have been sending signals all over the place. These signals reach deep space, although they are quite weak by then. But does this matter? An advanced race may be able to hear them no matter how dim and feeble those signals are.
On top of that, earthlings have been sending junk up into space since the 1950s, and a couple of those bits of space junk have almost reached the edge of interstellar space. All of this stuff floating around out there act like beacons that just point a huge, glowing finger at our Big Blue Marble, saying "HEY GUYS, WE ARE HERE, COME CHECK US OUT."
Hell, we even tried to give directions to our planet on the outside of the Voyager I and Voyager II probes. Thank the Lord we screwed that one up by being stupid.[1] When we made those golden records, we had very little understanding of how many Pulsars there were in Milky Way galaxy. Back then, we thought there were only a few of them, but now we understand that there may be a billion of them pulsing around out there. Bullet dodged.
But that won't keep us from continually trying to contact other life forms out there. We are too proud to realize that we are a crying baby in the Dark Forest.
The Dark Forest
There once was an infant lost in the woods, crying its heart out, wondering why no one answered, drawing down the wolves. 
We've been sitting in our tree chirping like foolish birds for over a century now, wondering why no other birds answered. The galactic skies are full of hawks, that's why. Planetisms that don't know enough to keep quiet, get eaten.
Both of these quotes are from a book called "The Forge of God" by author Greg Bear. They pretty much best illustrate why the hell we should shut up and keep our heads down if there really is life out there in the universe that is capable of interstellar travel.
