Things I'd like to learn about when I have time -
Phlegm - it makes so much of my life miserable. What is it? Does it have a positive use?
The water system - I have no clue about how the water in my home/city works and I have a hunch I probably have some very strange and laughable ideas about it.
And in the time it took me to write this, I probably could have hit wikipedia and gotten everything straightened out.