At some point Sunday night, someone flew a small drone onto the grounds of the White House. White House press secretary Josh Earnest told reporters that the drone -- or, to remove the ambiguity of that overly broad term, the small quadcopter -- posed no threat to the building or its inhabitants. The incident raises the question: Could a small unmanned aerial vehicle (UAV) pose such a threat? To answer that, we need to know the answer to three other questions. How far can a UAV fly? How is it controlled? And: What can it carry? Could a larger drone...