Aviation: Unmanned aerial vehicles are a vital tool of modern warfare. Once-harmless drones are now deadly attack aircraft. Where did the technology come from, and where is it going?

• 航空：无人驾驶的空中飞行机是现代战争的一中至关重要的工具。曾经无任何伤害的无人驾驶飞机如今成了有致命攻击性的飞行机。这种科技是从何处产生的，而它又会用于何处？