4 December 2023

False: Water in container does not prove Chinese astronauts are not in space

Experts say it is possible for water to remain inside a container in space because of surface tension. It is also possible to fill a container with water in a space station.


A photo posted on Twitter on June 25 showed a transparent container filled with water placed steadily on a table inside what appears to be China’s Tiangong space station.

The image also featured three Chinese astronauts, often called taikonauts, and suggested they are not actually in space because of the water-filled container.

Similar claims with different variations were found all over the internet, with tweets such as this and this, Facebook posts like this and online forum threads on LIHKG and Dcard.

The tweet on June 25 received over 4,400 likes while other posts accumulated over 7,000 engagements as of this writing.

However, this claim is false.

Keyword search led to the video aired by China Global Television Network that shows the same scene as the viral photo.

It was part of the educational live broadcast from the space station called Tiangong Class and its first episode in 2021. In the video, three taikonauts performed science experiments on the Tianhe core module.

It shows the container was held steady on the table using velcro strips that prevented it from floating in the air and causing potential damage to other equipment in the space station.

Annie Lab contacted professors Yan Renbin and Xu Lei from the Physics Department of The Chinese University of Hong Kong. They explained to us that it is possible to have a container filled with water inside a space station.

Xu said water could wet and stick to the walls of the container with or without gravity. Without large-enough velocity, the water would remain static in the cup, according to Newton’s First Law of Motion, he said in an email on June 30.

“If anyone wants to make water fly out of the cup, he or she needs to provide a large enough initial velocity to the water, which can help water to detach from the glass wall of the cup,” he explained.

Yan also said this is a natural behavior of water due to surface tension. The surface of water resists an external force, according to the explanation by the United States Geological Survey, because of the cohesive nature of its molecules.

Both physicists suggested that the container could be filled with water if taikonauts slowly put the water into it. For example, by using a straw or needle, the water would naturally stick to the container.

In 2013, a Canadian astronaut inside the International Space Station performed an experiment in a similar educational video in order to explain how water behaves in space due to the surface tension (video below).

On June 30, China Manned Space posted a video on Weibo that shows behind the scenes of the Tiangong Class.

At 0:11-0:24, it shows Taikonaut Wang Yaping (王亞平) squeezing water droplets from the bag to fill the container with water. She is using a syringe to remove air bubbles inside at 0:37-0:48.

A behind-the-scenes video shows Taikonaut Wang Yaping filling the container with water.

The container of water was prepared for an experiment to show there is no buoyancy in space.

When Wang put a ping pong ball into the container with water, the ball submerged in water, instead of floating on the surface (which is what normally happens on Earth).

The ping pong ball stayed inside the water container.

The video can be deemed as proof that the taikonauts were in a microgravity environment.

“In fact, the rest of the video demonstrated the effect of surface tension of water really well,” Yan said.

In the behind-the-scenes video, water is seen bouncing within the container at 1:16-1:20, which also illustrates the water behavior in space.

Prior to the experiment, Wang also demonstrated how she would drink water in space, by squeezing spherical water droplets from a water bag — a common practice for astronauts living in space.

These water spheres seen in space are also formed due to surface tension, according to NASA. Other experiments conducted in Tiangong Class also illustrated typical science phenomena in space, such as optics of water spheres.

Having completed the six-month space mission, the three taikonauts returned to earth on April 16, 2022.

This exact claim has been fact-checked by the Hong Kong-based organization Factcheck Lab as well. Annie Lab has also debunked other similar claims relevant to taikonauts and Chinese space missions like this and this.

Updated on July 8, 2022: 

Chinese media Our Space also said on June 30 on the question-and-answer platform Zhihu that the water was held steady inside the container thanks to surface tension. It mentioned the Tiangong Class experiment with a ping pong ball that stayed submerged in the water as proof. 

Our Space is an educational media with staff comprised of a team of taikonauts, engineers, doctors and researchers. 

In an interview with China News Service on June 28, a researcher at China Academy of Space Technology, Pang Zhihao, also debunked the false claim and said the water could be transferred into the container with a syringe.