Osteoarthritis (OA) . OA is the wear-and-tear arthritis that usually occurs with aging or after injury. With OA, there's a wearing down of the cartilage that cushions the ends of the bones. OA causes joint swelling in those joints that bear weight over a lifetime, such as knees, hips, feet, and spine.
During the Zhou dynasty, the Chinese developed irrigation and flood- control systems. As a result, farmers could grow more crops than ever before. Because more food could support more people, the population increased. During the late Zhou dynasty, China's population had expanded to about 50 million people. Zhou people also learned to use iron, which was cheaper and stronger than bronze. Iron weapons, the catapult and China's first cavalry (military on horseback) were some of the Zhou achievements that helped strengthen the army.
Science and Technology in Ancient China. The history of science and technology in China is both long and rich with many contributions to science and technology. In antiquity, independently of Greek philosophers and other civilizations, ancient Chinese philosophers made significant advances in science, technology, mathematics, and astronomy. The first recorded observations of comets, solar eclipses, and supernovae were made in China.