Photo taken with a fisheye lens on March 29, 2021 shows a worker maintaining China's Five-hundred-meter Aperture Spherical radio Telescope (FAST) in southwest China's Guizhou Province. FAST has identified over 300 pulsars so far. Located in a naturally deep and round karst depression in southwest China's Guizhou Province, it officially began operating on Jan. 11, 2020. (Xinhua/Ou Dongqu)