We now know that masks have an effect on slowing the spread of COVID-19. Masks protect the wearer and the people around them, a two -way protection. We are going to explain in this article that widespread mask-wearing is a powerful way to extinguish an epidemic. (with some little math). When a person exhales they spray out saliva particles mixed with viral particles. This virus-laden saliva spray is the main way that COVID-19 spreads...