November 6, 2013
Ice Paths Used To Build Beijing’s Ancient Forbidden City
Brett Smith for redOrbit.com - Your Universe Online
Throughout the history of civilization, societies have constructed massive feats of engineering using only the most basic technology and a lot of ingenuity. Now, a study published in the Proceedings of the National Academy of Sciences revealed new details about one such feat of engineering – Beijing’s Forbidden City palace. Constructed starting in the 15th century, the Forbidden Palace was built with massive stones weighing over 300 tons that were transported to the site with the help of massive ice sleds.
“You go to the Forbidden City and see these massive rocks, and you ask yourself: ‘How in the world did they ever move this rock here?’” study author Howard Stone, a fluid mechanicist at Princeton University told Nature magazine.
After studying historical records and experimenting with the hauling technology of the time, the study researchers from China and the US discovered that workers dug wells every third of a mile to gather water that was sloshed on frigid winter roads, creating a man-made path of ice that eased the course of a work sledge.
Scientists had wondered why the Chinese workers didn’t use wheels to transport the massive rock slabs. Yet according to Stone, wheeled vehicles in China could not withstand loads greater than about 94 tons.
Simply dragging a stone-laden sledge across land would be demanding as well, requiring more than 1,500 men, the study researchers calculated. By comparison, pulling the same vehicle across bare ice or on wet, wooden rails would demand at least 330 men.
However, if a stone-burdened sledge were pulled along an ice road slickened by a film of water, fewer than 50 men would be needed, the researchers found.
"If you didn’t lubricate it with additional water then ... the object would have just frozen to the ground," Stone told NBC News.
This technique allowed one 123-ton rock to be transported from a quarry 43 miles away over the course of 28 days, according to a 500-year-old document translated by study author Jiang Li, a professor of mechanical engineering at the University of Science and Technology in Beijing.
Stone said that the surface "may be similar in a certain sense to finely constructed Roman aqueducts or some of the old Roman roads which were smooth. "The Chinese technique compares to that used by ancient pyramid builders in Egypt, who pushed limestone on roller logs and up ramps to bring them into place on the massive pointed structures.
Stone said it’s unfortunate that "they couldn't freeze" the path for their stones.
The Forbidden City and surrounding area served as the figurative center of the Chinese empire during the Ming and Qing dynasties after Ming emperor Yongle moved his imperial capital from Nanjing to Beijing.
Considered to be one of the great periods of societal stability in human history, the Ming dynasty was marked by a considerable exchange with the Western world – particularly in science and technology. Ironically, some Western technology at the time had origins in ancient China and was reintroduced to the Asian nation during the Ming dynasty.