Ask Dr. Notebook

Q: What's all this talk about "international airspace"? Basically, I'm thinking about investing in some home antiaircraft weaponry, but I want to make sure I can legally shoot down any planes flying above my apartment first.

A: In 1944 the Chicago Convention on International Civil Aviation decreed that every country has sovereignty over the airspace above its territory, which includes a bonus 12 miles of adjacent water. Airspace stops short of outer space, which begins at about 55 miles, according to some experts (there's no official definition). And no, you own nothing beyond the 9-ft. ceilings of your apartment.