Facts you didn't know about China Despite its size, China fits into just one time zone. In the Tang dynasty, every educated person was expected to greet as well as say goodbye to another person in poetic verse composed on the spot. Ketchup originated in China as a pickled fish sauce called ke-tsiap. China is widely accredited (by, among others, FIFA President Sepp Blatter) with the invention of football in the 2nd and 3rd centuries BC. Linzi, the capital of the ancient Chinese state of Qi, is said to be the birthplace of "cuju" - "kick ball with foot." There are more Christians in China (an estimated 54 million) than in Italy (47 million) and China is on track to becoming home to the world's largest Christian population. The rate of dog consumption in China is declining: most Chinese people now prefer to keep cats and dogs as pets. But snakes are still fair game. On an average day in China, 1.7 million pigs are consumed. The Hong Kong Chinese get a day off work to sweep their ancestors' graves. During the Ching Ming festival, extra buses are laid on to cope with the exodus from city to hillside graveyards. A 13th floor is often absent from hotels and commercial buildings and vehicle licence plates and phone numbers are often devoid of the number four. Superstition and numerology are prevalant in Chinese culture. Chinese woman traditionally marry in festive red - a lucky colour. White symbolises death. Chinese people are under pressure to down chopsticks in order to save the planet's resources. Some 80 billion sets are produced annually. One in five people in the world are Chinese. A panda's entire mating season lasts only about two or three days. Once they have mated, females chase the males out of their territory and raise their cubs on their own. Until her death in December 2012, Yao Defen, who stood 7ft 8in high, was the tallest woman in the world. Paper was invented in China, with early attempts made from hemp dating back to the Western Han (206 BC - 24 AD). In 105 AD, records show the method was improved by using the crushed bark of a mulberry tree. The mechanical clock was another great Chinese invention, although the earliest model was an enormous 30 feet high. It was created by a monk named Su Sung in 723 AD. Concern about pollution in Chinese cities has inspired the production of canned fresh air, sold for five yuan a can. Varieties include "Pristine Tibet" air, "Revolutionary Yah'an" and Post-Industrial Taiwan." At China's controversial dwarf theme park in Kunming, "little people" overseen by an emperor put on daily shows for tourists. Read more: The world's strangest theme parks