Calcium Calcium Calcium is a chemical element with symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to its heavier homologues strontium and barium. It is the fifth most abundant element in Earth's crust and the third most abundant metal, after iron and aluminium. The most common calcium compound on Earth is calcium carbonate, found in limestone and the fossilised remnants of early sea life; gypsum, anhydrite, fluorite, and apatite are also sources of calcium. The
A Scientific Support for Darwinism case, as well as announce the results in a press release. The petition was not completed sufficiently early to submit it as part of an "amicus curae" brief for the Dover case. However, if the case was to go to the US Supreme Court, the petition could have been submitted as an "amicus" brief at that time. R. Joe Brandon emphasized that this "Four Day Petition" did not mean that scientific issues are settled by majority vote. What Brandon maintains is that this is an indication of the level of scientific consensus that accepts evolution as a viable established scientific