Blackboard ‘chalk’ are produced especially for use with blackboards in white and also in various colours. White chalk sticks are made mainly from calcium carbonate derived from mineral chalk rock or limestone, while colored or pastel chalks are made from calcium sulfate in its dihydrate form, CaSO·2HO, derived from gypsum. Chalk sticks containing calcium carbonate typically contain 40–60% of CaCO (calcite). As compared to whiteboards, blackboards still have a variety of advantages: On the other hand, chalk produces dust, the amount depending on the quality of chalk used. Some people find this uncomfortable or may be allergic to it, and according
What Planet Are You From? What Planet Are You From? What Planet Are You From? is a 2000 American science fiction comedy film directed by Mike Nichols and written by Michael Leeson, Garry Shandling, Ed Solomon, and Peter Tolan based on a story by Leeson and Shandling. The film stars an ensemble cast featuring Shandling, Annette Bening, Greg Kinnear, Ben Kingsley, Linda Fiorentino, and John Goodman. A denizen (Garry Shandling) of a faraway planet occupied only by highly evolved males is ordered by his superior, Graydon (Ben Kingsley), to find a female human, impregnate her and bring the baby back to the planet. The visitor