This is a fascinating/revealing video:
Is Dust Mostly Dead Skin?
Veritasium is making the usual kind of informative video they make. This one is sponsored by Google, so he talks about how to use Google to search, what kind of information Google will present and how to parse that information.
What I find particularly... cute, is how eventually Veritasium calls up some people with relevant expertise, who point him to a book. Which is where he finds his answer.