We all remember the advice frequently repeated during the COVID pandemic: maintain six feet of distance from every other human when waiting in a line to avoid transmitting the virus. While reasonable, the advice did not take into account the complicated fluid dynamics governing how the airborne particles actually travel through the air if people are also walking and stopping. Now, a team of researchers led by two undergraduate physics majors at the University of Massachusetts Amherst has modeled how aerosol plumes spread when people are waiting and walking in a line.