درخت حوزه‌های تخصصی

Climatic events, especially severe droughts, have played a key role in cultural evolution and the challenge of civilizations. Climate change, which affects the natural resources and, consequently, the health and subsistence system of human societies, can lead to increased violence, migration, war, and the spread of epidemics. The main purpose of this study is to investigate the possible effects of climate on important events of the Sassanid era. Extensive regions of the Near East and Central Asia have been more vulnerable to droughts, which often recurred during cooling periods, due to semi-arid to hyper-arid environmental conditions. From the second half of the fifth century AD with the beginning of the cold event of the early Middle Ages, the occurrence of droughts and cold waves caused famines and epidemics. These tensions seem to have triggered many social and political events in the Sassanid realm and neighboring regions. These conditions in the sixth and seventh centuries AD caused the gradual decline and eventual fall of the Sassanid government due to Arab invasions. Historical and paleoclimate studies show that successive wars with Central Asian invaders in dry periods, and the frequent outbreak of plague associated with falling temperatures, especially following the floods of the Tigris and Euphrates rivers in AD 628, were affecting factors in the dynasty’s weakness and collapse. Besides, some civil wars and revolts, such as the Mazdaki movement, can be considered as indirect effects of climate tensions that contributed to the gradual decline of the Sassanid Empire. 

A regular hexagon is one of the shapes introduced in Plane Geometry and refers to a hexagon with equal sides wherein the size of each angle is 120 degrees. This geometric shape, which can be quickly drawn today, was constructed over a long period in the millennia BC In the Late Neolithic period in Mesopotamia, the primary geometric shapes, including triangles, quadrilaterals, arcs, and circles, were additionally painted on the surface of pottery ware. Naturally, these shapes had been initially drawn by hand, and the sides of the polygons were not comprised of straight lines, or the circles had not been drawn perfectly. However, in the Chalcolithic age, geometric shapes moved away from handmade forms and approached standard ones. This standardization was not possible without drawing tools. In the meantime, the role of compasses or other objects with a similar use was of utmost importance because drawing a circle with such tools paved the way for drawing regular polygons. In fact, from the Late Neolithic, handmade triangles and arcs in the Near East, the first regular hexagon in the late second or the early first millennium emerged over several thousand years. Constructing this geometric shape with the help of standard circles and arcs has been well documented in the Near Eastern archaeological evidence. On the other hand, regular hexagons have been attributed to the second half of the first millennium in the history of mathematics. Therefore, this study reflected on the construction process of this geometric shape and dated its drawing hundreds of years back.