When was the last time you came across a flat earth'er? Or someone who didn't know how cars work? Or you name it... I came across this often when I used to teach 10-15 yr olds.
It's obvious but, No one person understands everything. Even people in science must have things they do not understand.
What don't you understand in Science?
What clear, concise, killer answer do you give for X (Your favorite pet peeve or part of science)?
My favorite experiment for explaining the spinning of the globe is "Foucault's pendulum." Imagine a pendulum above the north pole. As the pendulum rocks you would notice it draws/cuts out different sections as the earth turns below it. ;)