RE:Sorry if I offended you there …No worries Frank, Not much offends me really. Brownian motion. Hmmm. Like aerosol smog suspended in a stable air mass. I do some air dispersion modelling from time to time for my buddy who has a consulting engineering firm in Ontario specializing in air quality. Ontario has this environmental protection regulation where you have to register an EASR if you emit anything into the air. Part of the requirements of the EASR is to do an air dispersion model. I use the AERMOD air dispersion model a lot. Have you noticed how contaminated the air is getting lately especially in Alberta from all of those wild fires? That smoke is fine particles or aerosols. In a stable air mass the motion of the aerosols is Brownian. Anyway it's gonna get a lot worse they say. The wildfires are forcing oil companies to shut in production.