I read the Bad Astronomy blog, mainly because it's fun to know the correct thing about something. Like the fact that our planet (Earth, in case you were wondering) is not the only planet to experience solar eclipses. Saturn does, too, by virtue of being so far away, that its moons appear bigger than the sun.
So I trip over this clock today at BAB, and it fascinates me. I vaguely remember having some fun with math back in my school days, and the number 9 has some interesting properties. The clock shown on BAB displays (!) quite a few.
Now, this had the advantage of making me try out some software on my new iMac. I bought iWork and fired up its spreadsheet so I could play with the formulas and see how they resulted in the whole numbers a clock face usually has. And, in so doing, I finally learned what ! means in mathematical notation.