阅读下面的短文，然后根据短文内容回答问题。

Members of Shenzhou XIII gave a science lecture (讲座) to millions of students on December 9, 2021 in the Tiangong space station.

The three astronauts Zhai Zhigang, Wang Yaping and Ye Guangfu said hello to students, teachers and other viewers (观众) when the lecture started in the afternoon. They explained their life and work inside the space station.

The astronauts made some interesting scientific experiments (实验) in space, such as a "water ball". They also invited young viewers to do similar experiments along with them. Besides, they answered the questions from students during the lecture.

It was the first lecture of the Tiangong Class and more lectures will be held. Such activities will make young people know more about space and love science.