In an effort to educate the public about China’s space station building progress, Chinese astronauts returned a scientific lesson to Earth on Thursday.

Using examples from buoyancy, motion of objects, and optics in a weightless environment, I attempted to make a point about physics.

They were greeted by astronauts from five different places, including Beijing and the semi-autonomous city of Hong Kong, who answered questions about life in space. A livestream of the event was also available for those interested in watching.

Wang Yaping, the station’s lone female instructor, was aided by Ye Guangfu and Zhai Zhigang, the station’s commander-in-chief. In 2013, while aboard one of China’s first experimental stations, Wang delivered a similar lecture.

A six-month stay at the station was set up for the arrival of two further modules, dubbed Mengtian and Wentian, in order to complete the Tianhe module by the end of the year.

A spacewalk by Wang and Zhai last month made history as the first time a Chinese woman went outside the station’s module to perform maintenance and tests with the station’s robotic service arm.

China’s Shenzhou-13 mission is the country’s longest since it became only the third country after Russia and the United States to deploy a human into space in 2003.

Upon finished, the permanent station will weigh approximately 66 tons, which is far less than the International Space Station, which launched its first module in 1998 and weighs approximately 450 tons.

The crew of the Tianhe module is also examining living conditions and performing research in space medicine and other areas in preparation for the station’s development.

Chinese spacecraft were denied access to the International Space Station mostly because of the United States’ fears over its close military ties to the country.

Additionally, China has continued to send unmanned missions to the moon, and last week, its Yutu 2 rover beamed back images of what some had labeled as a “mystery hut,” but was likely merely a rock of some sort.

While the Chang’e 5 spacecraft delivered lunar rocks to Earth last December, it was China’s first rover to be deployed on the moon’s little-explored far side. Meanwhile, a Chinese rover is scouring the surface of Mars for signs of life.

The show has also sparked debate. As recently as October, China’s Foreign Ministry said it was simply testing the feasibility of using a new spaceship to launch a hypersonic missile.

In addition, China is said to be developing a highly classified space plane.