b'Brownian motion | Engineer Innovationthis way: "When a sneeze works properly, it resets the environment within nasal passages, so "bad" particles breathed in through the nose can be trapped. The sneeze is accomplished by biochemical signals that regulate the beating of cilia (microscopic hairs) on the cells that line our nasal cavities." The definitive study on the topic is a 2014 Journal of Fluid Mechanics paper from MIT entitled "Violent expiratory events: on coughing and sneezing," which explains how both events depend on a "multiphase turbulent buoyant cloud" erupting from a person\'s mouth, consisting of "hot and moist exhaled air," as well as drops of saliva. According to the study - which involved both numerical simulation and physical experiment, a typical sneeze consists of a cloud of up to 40,000 droplets traveling at peak velocities of over 200 miles an hour, which can project virus-laden mucus up to 25ft (7.5m). These droplets stay suspended in the air for up to 10 minutes!All of which makes you think that wearing face masks in public whenever you are suffering from a cold, as is common in some Asian cultures, it probably a good idea if only to limit the velocity of one\'s mucus cloud. However, given that I\'ve sneezed three times while writing this article, it would mean that my face would also be hidden behind a mask for much of the year. If you knew what I look like, you\'d probably agree that that is a good idea too. n97'