On 29/04/2017 09:46, Brian Gaff wrote:
I don't know I guess its habit. Many machines do not have fast revolving
brushes.
I often have thoughts about muck. where does it all come from?
Not all of it can be shed skin, so one must assume its come from outside
and maybe even outer space.

http://en.wikipedia.org/wiki/Cosmic_dust

I don't think a large proportion of household dust is from outer space,
but some micrometeorites do reach ground level, and are collected.

Here's a podcast about the subject:
http://www.bbc.co.uk/programmes/b08mbjqp

--
Max Demian