Why does foil have a shiny side and a dull side?

your previous post had a sense of absolutism which the facts don’t support.

and my point really was when people say things like, “bundle up, or you’ll get sick” - there’s a why behind it

so while folk wisdom isn’t infallibly right, it’s not infallibly wrong either. im still holding out for future foil science i guess. and i’m basically okay with people deciding their foil side needs to be a certain way

i think the moral of the story though is, don’t bundle up with aluminum foil. unless you do