A woman takes a photo at the exhibition "Secrets of the Celestial Empire" in Moscow, Russia, on Oct 12, 2017. The exhibition, held from October 12 to November 5, displays such exhibits as paper, silk and the seismoscope invented by Chinese inventor Zhang Heng (AD 78-139). [Photo/Xinhua]

A woman takes a photo at the exhibition "Secrets of the Celestial Empire" in Moscow, Russia, on Oct 12, 2017.[Photo/Xinhua] People look at the exhibits during the exhibition "Secrets of the Celestial Empire" in Moscow, Russia, on Oct 12, 2017. [Photo/Xinhua] A woman looks at a seismography during the exhibition "Secrets of the Celestial Empire" in Moscow, Russia, on Oct 12, 2017. [Photo/Xinhua]