The USD 196 million telescope, with a dish area as large as 30 football fields and expected to be ready by next year, is being built in a hollow formed in the mountainous Guizhou Province due to collapse of a karst cave 45 million years ago.
Technicians are assembling the telescope's reflector, which is 500 metres in diameter and made up of 4,450 panels. Each panel is an equilateral triangle with a side length of 11 metres, state-run Xinhua news agency reported.
It will be 10 times more sensitive than the steerable 100-metre telescope near Bonn, Germany, said Zhang Haiyan, deputy director of the general office of the FAST Project.
Engineer Zhu Boqin, who worked on the site selection more than 20 years ago, said the surrounding area has "radio silence" as there are no towns and cities within a radius of 5 km and only one county centre within 25 km.
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For example, they could survey natural hydrogen in distant galaxies, detect faint pulsars, look for the first star shining, or even hear possible signals from other civilisations.
Chen Xuelei, a specialist in dark matter and dark energy research at the National Astronomical Observatories of China, said FAST could do large-scale surveys for HI emissions from galaxies, which would help understand the state of dark energy and the speed of cosmic expansion.
Perhaps, the most exciting goal of FAST is the search for other life. Instead of searching for life per se, scientists are looking for the molecules that constitute life, Xinhua quoted Chinese scientists as saying.
Scientists have found about 180 kinds of molecules in space, including carbonic oxide, ammonia, and methanol.
Li Di - who is a scientist at National Astronomical Observatories, Chinese Academy of Sciences - estimates that in two or three years, scientists could find amino acid, the foundation block of life.