CAMBRIDGE - The artificial origin of the stones of the pyramids is a theory that gives indigestion to conventional archaeologists. That is, some of the immense blocks of the Great Pyramids of Egypt could have been cast with synthetic material - the world's first concrete - not just cut whole in quarries and dragged into place by armies of workers. This innovation would have saved millions of man-hours of cutting and transporting the 2-ton stones in the construction of the enigmatic buildings

En 貌ptica, un cercle de confusi贸 茅s una taca 貌ptica causada per un con de raigs de llum d'una lent que no arriba a un enfocament perfecte a l'hora d'imaginar una font puntual. Tamb茅 es coneix com a disc de confusi贸, cercle d'indistinci贸, cercle de desenfocament o punt de desenfocament. En fotografia, el cercle de confusi贸 (CoC) s'utilitza per determinar la profunditat de camp, la part d'una imatge que 茅s acceptablement n铆tida. Sovint s'associa un valor est脿ndard de CoC a cada