英语时差：飞机如何平稳飞行？（下）

Turbulence is characterized by winds moving at different speeds. If the airborne particles are moving in wildly different directions in one region, but moving in unison in another, the pilot will have a much better sense of exactly where the most severe turbulence is. Another system is needed to detect so-called “clear air” turbulence, or turbulence not associated with storm clouds. Researchers have developed a system that shoots an infrared laser beam ahead of the plane. This works like the radar, bouncing off airborne particles and measuring their motion, but it is sensitive enough to measure the motion of tiny dust particles from miles away. Some particles exist even in the cleanest air, so this system would help detect any kind of turbulence, which might make flying a whole lot smoother.