Put down your graphing calculator and compass and pick up your calendar. These are the six days that the one-of-a-kind Exploratorium at Pier 15 is absolutely, positively free. If you were a science fair kid, you probably want to mark all of them right away. And if not, it's never too late to learn the basic laws that govern our existence!

Sunday, February 1, Groundhog Day: Get a jump on Punxsutawney Phil with an early Groundhog Day party and shadow demonstrations.

Saturday, March 14, Pi Day: Join this annual celebration commemorating the mathematical constant, 3.1415926535 etc.

Sunday, May 10, Mother's Day: For the scientific mother, with bilingual programs (English/Spanish) for the whole family.

Sunday, September 27, Latino Engineering Day/Dia de la Ingenieria: This collaboration between the Exploratorium and the Society of Hispanic Professional Engineers honors prominent Latino engineers and the engineering heritage of Latinos. Many programs are conducted in both English and Spanish.

Sunday, October 11, Founder's Day: Celebrate the Exploratorium's founder, physicist and educator Frank Oppenheimer. That's right, Oppenheimer was responsible for both the Manhattan Project and the Exploratorium

Saturday, December 6, Winter HoliDay: Kick off the next holiday season and even get in some geeky present shopping at The Store.