Crystallography and the world of symmetry / Кристаллография и мир симметрии

Let us begin with the question: What is a pattern? The answer to this question is as much objective as it may be subjective. From the days unknown, the human race have started studying and appreciating the regular periodic features like movement of stars, moon, sun, the beautiful arrangement of petals in flowers, the shining faces of gems, and also the beautiful wings of a butterfly. They have constructed many architectural marvels like tombs, churches, pyramids, and forts having symmetries, which still attract tourists. The regularities observed in nature either in the worlds of plants, animals, or inanimate objects are patterns and people get startled by observing them and thrilled by inspecting them. That may be the beginning of the study of pattern. <...>