Today is **Advent Calendar Day**! This date is so decreed by the supermarket chain Aldi, purveyor of popular advent calendars. Today shoppers can find their best-selling wine, beer, cheese, and chocolate advent calendars on the shelves. Advent calendars aren't just for Aldi shoppers, though. You don't have to get a traditional, edible advent calendar to count down the December days -- you can find something educational and fun that offers a unique treat each day.

For instance, this awesome advent calendar from The Crazy Scientist offers 24 cool science experiments to perform each day leading up to Christmas. The experiments can be performed in just a few minutes, and are suitable for youngsters aged 8 and older, or younger children with help and under supervision. When completed, the boxes from the calendar can be used as a board game, making the fun last even longer than the advent period.

Newton's law of universal gravitation, sometimes called Newton's law of gravity, is a mathematical equation that relates force between objects, mass, and distance. The formula is presented on this t-shirt within an illustrated apple -- alluding to the story that Isaac Newton was inspired in his work...