For anyone who grows anxious at the sound of a sneeze or a cough these days, Lydia Bourouiba’s research offers little comfort. Bourouiba, a fluid dynamics scientist at MIT, has spent the last few years using high-speed cameras and light to reveal how expulsions from the human body can spread pathogens, such as the novel coronavirus. Slowed to 2,000 frames per second, video and images from her lab show that a fine mist of mucus and saliva can burst from a person’s mouth at nearly a hundred miles an hour and travel as far as 27 feet. When the sternutation is over, a turbulent cloud of droplet-containing gas can remain suspended for several minutes, depending on the size of the droplet.