- The Communist Manifesto (Wikipedia)
The Communist Manifesto (German: Das Kommunistische Manifest), originally the Manifesto of the Communist Party (Manifest der Kommunistischen Partei), is a political pamphlet written by Karl Marx and Friedrich Engels, commissioned by the Communist League and originally published in London in 1848. The text is the first and most systematic attempt by Marx and Engels to codify for widespread consumption the core historical materialist idea that, as stated in the text’s opening words, “the history of all hitherto existing society is the history of class struggles”, in which social classes are defined by the relationship of people to the means of production. Published against the backdrop of the Revolutions of 1848 and their subsequent repression across Europe, the Manifesto remains one of the world’s most influential political documents.
- Calcium (Wikipedia)
Calcium is a chemical element; it has 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 name derives from Latin calx “lime”, which was obtained from heating limestone.