Looking Smart

So I caught myself explaining what I know about physics to a friend today, and it struck me that it felt like I was trying very, very hard to look knowledgeable. In the Tao te Ching, Lao Tzu said, "(S)He who speaks of a thing does not truly understand it."

Paradox aside, how can one explain something to someone without looking smart? That is, how do I explain physics to someone who isn't versed in it in such a way that it sounds like anyone could do it, instead of an intellectual elite?

Don't bother explaining, it's a waste of time, unless you plan to spend a lot of time with someone (lol marriage). But then it won't matter how inept you are at it because the hormones flying all around will make it irrelevant.