Warning this is a deployement of another weapon of mass education please read carefully.
Yep the Moon, one of the most puzzeling puzzle in our small solar system. The only place outside of our own little Earth were the human hand as set a foot. And yet something we don't really understand, well more like we don't understand as well as we understand some other things in the univers and on Earth. You see there are many thing strange with the Moon, first it is freaking huge. In proporition it is larger then all other moon in the solar systeme (with the exception of Charon Pluto's twin planete/moon), second it as a composition very simillar to earth yet with "strange" exception (notably in the abundance of some heavy elements), it has a remarquably hight angular velocity and circular orbits, and it most have formed amazingly close to the Earth to be at its distance today considering it move farther from the Earth 3 cm each years.
But even more amazing then all these things is how we think it formed (with numerical simulation showing that this is indeed a good way to form a moon with the characteristic ours has.) So here it is for your eyes only the receipe for our Moon: First you take a rock the size of Mars composed of hot rock. Second you need a planete slightly lighter then Earth and still only composed of two things: Hot rock and hotter rock. You slam the two together in a grasing collision and about 1 or 2 day later you have the Moon! Yes you read correctly you slam Mars into primordial Earth and what remains is a bigger Earth and a close by Moon. Up to now that is the only theory that accounts for all we know about the Moon and it's very impressive to think that something the half the size of our planet can strike our planet without completly destroying it is amazing. And it also means that planet destroying weapon of SF are probably impossible thankfully.
The weapon of mass education have been deployed and used, open your mind to new things and search for more information yourself. You'll be amaze how wonderfull, strange and interesting science and learning can be. Have fun and don't forget.