The Volokh Conspiracy
Mostly law professors | Sometimes contrarian | Often libertarian | Always independent
Aerosol researcher and co-author Chang-Yu Wu explained that local humidity and temperature play vital roles in the size of the virus's particles, which can influence its life span in the air. Drier atmospheres in colder regions will induce water evaporation from the particles, shrinking their size and allowing them to float in the air for longer periods. People also tend to seek shelter inside in colder environments and expose themselves to recirculated air that potentially contains the virus.
The air in humid, hotter environments contains more water, which can condense onto the virus particles, make them bigger and theoretically fall to the ground faster. Wu compares the particles to a rock in this case — the more mass, the faster it falls.
Liberman notes that the Wu paper "needless to say, has nothing like the WaPo's 'the more mass, the faster it falls' explanation." (Of course, objects' characteristics can affect the speed at which they fall, for instance because of air resistance, and the behavior of aerosols can be quite complex; but those effects are generally quite slight for "a rock," as our friend from Pisa demonstrated.) Liberman adds:
As often in the interpretation of reported interviews in news articles, the WaPo article leaves us with a problem in abductive reasoning. Did the interviewee really say that? or did the writer (or one of their editors) misunderstand, misremember, or invent it?