**Ask a monkey a physics question thread**

[Poopadoop]

@poop: I concede that neither of us is definitively correct on the question of "what is dust?"

Don't concede anything on my behalf lol.

A) There are a ton of conflicting sources, and even the quotes I can find by "experts" on dust lack any links to their studies and data.

B) Dust is a definition of particulate size. Any object or substance which is of that physical size is considered dust.
Therefore, the composition of dust varies widely from location to location.
(Dust at a smelter is going to be dramatically different than dust in a house.)

C) Dust from textiles and hair tends to be fluffy, or lower density than skin dust. Dust from human skin cells and the dust mites that eat them tend to be compact, and have a higher density.
The ratio of what is most prevalent will be different if you're comparing amounts by volume or amounts by mass.
The sources I've found do not state which metric they've used to draw their conclusions.

One thing that seems clear is that there isn't sufficient volume or mass of shed skin cells to make up the majority of house dust. An empty house collects dust, for example, though there's obviously no human skin cells being shed in it. I'm inclined to think house dust is mostly mineral matter (i.e., dirt) and plant matter (e.g., pollen), with animal matter coming in a distant third behind those two.