Why did China build such a large telescope and why was it built in Guizhou province?

Lin: The idea was first proposed at a conference of the International Union of Radio Science held in Kyoto, Japan, in 1993. Scientists agreed that a huge radio telescope should be built to explore origin of the universe. Chinese astronomer Nan Rendong attended the meeting and discussed it with other scientists back home, who put forward the idea to build the world's first radio telescope with a diameter of 500 meters. At that time, the largest radio telescope in China is only 25 meters in diameter.

With support of the government, site selection and preliminary research kicked off in 1994, and in 1995 a special team was established for the program. In the late 1990s, the world's largest radio telescope was the 305-meter-diameter Arecibo Telescope of the United States, located in Puerto Rico.

Construction of FAST began in 2011 and finished in September 2016. It was opened to domestic astronomers in April 2019. In December 2020, the Arecibo Telescope collapsed, and FAST, which can receive electromagnetic signal 10 billion light years away, became the only "eye" to see that far into space. FAST was opened to the global science sector in April 2021.

Jiang: Karst is a special landform in which water will permeate into underground soil and not cause sedimentation. So the telescope will not be influenced by rainwater or rotation. In late 1995, about 300 candidate locations were found, and the Dawodang area in Guizhou was selected. The place was deep in the mountains, with only a few villages around.