On Earth, adding a tab of Alka-Seltzer to water isn't particularly exciting—it quietly fizzes away. But when you add that same tablet to a blob of water floating in the middle of the International Space Station, it doesn’t just look otherworldly, it can give scientists insights into how water molecules interact.
In this new video from NASA, astronauts add food coloring to a floating blob of water to turn it an emerald green before adding an effervescent tab. The blob of water looks like it comes alive, twitching and squirming while suspended in space, captured in high definition by NASA's new RED Epic Dragon camera.
Though some droplets are ejected from the writhing blob, the mass stays together because water has a very high surface tension. This phenomenon is the reason why bubbles and raindrops are spherical, why some insects can walk on water, and why plants can draw water through their stalks.
Because water molecules are highly attracted to one another, they are constantly shifting around. Molecules at the center of the bubble pull at other water molecules from all directions, while ones on the outside are constantly being pulled inward.
This is why, without other interference, water blobs in microgravity are perfectly spherical, Bec Crew writes for ScienceAlert. But add a tab of Alka-Seltzer and the whole story changes.
Aside from being fun to watch, why do astronauts play with water in space?
NASA’s Lewis Research Center explains: “On Earth, studying surface tension in the midst of gravity related phenomena is like trying to listen to a whisper during a rock concert.” Free from Earth’s gravity, scientists can more easily study the phenomenon, which could lead to new ways of handling fluids on Earth that take advantage of surface tension’s properties.
And of course, surface tension makes for cool space videos. Lots of cool space videos.
Feast your eyes on an earlier video of effervescing water bubbles in space: