So this week, we wondered what might be the opposite of a swan, of a nipple, and of a Wankel rotary engine (no giggling at the back). You'll have to tune in and listen to find out what a Wankel rotary engine is, and indeed, what it's opposite might be.

Are we right? Or are we the opposite of right? Let us know, and join in the fun, because joining in is always fun.