Chinese astronauts aboard the country's Tiangong space station opened a science lecture on Thursday afternoon as they traveled with the gigantic spacecraft orbiting the Earth at an altitude of about 400 kilometers.

Major General Zhai Zhigang, Senior Colonel Wang Yaping and Senior Colonel Ye Guangfu, all members of the Shenzhou XIII mission crew, greeted students, teachers and other participants as the lecture began at 3:40 pm. They then showed viewers how they live and work inside the space station, which consists of a core module, a human-rating certified spacecraft and two robotic cargo spaceships.

The astronauts carried out experiments to display interesting physical phenomena in space such as "disappearing buoyancy" and a "water ball". Before the end of the livestreamed activity, they answered questions from students.

Millions of primary and middle school students across China watched the 60-minute televised event hosted by the China Manned Space Agency, the Ministry of Education and other government departments.

Groups of invited students in Beijing, Nanning in the Guangxi Zhuang autonomous region, Wenchuan in Sichuan province, and the Hong Kong and Macao special administrative regions were present at "ground class venues" and took part in video chats with the crew during the lecture.

It was the first lecture of the Tiangong Class, or Heavenly Palace Class, China's first extraterrestrial lecture series to popularize space science.

More lectures will be held based on the country's manned spaceflights and will also be presented by Chinese astronauts, the manned space agency said, adding that such activities are intended to spread knowledge about manned spaceflights and spark enthusiasm for science among young people.

The agency said before the lecture that Chinese astronauts "sincerely invite young viewers to conduct similar experiments along with them to observe the physical disparities between space and land environments to experience the fun of exploration".

It said that as a national space-based laboratory, Tiangong is also tasked with promoting and propagating science and technology knowledge. The orbiting outpost has abundant, unique educational resources and boasts advantages when it comes to encouraging the public, especially young people, to embrace science and space exploration, it said.

The Shenzhou XIII mission was launched on Oct 16 by a Long March 2F carrier rocket that blasted off from the Jiuquan Satellite Launch Center in northwestern China's Gobi Desert, with the crew soon entering the Tiangong station. They are scheduled to spend six months working in the station, making it China's longest manned space mission.