A completely new geometric form has been demonstrated for the first time, and it can only exist in microgravity. During an experiment aboard the International Space Station, Hungarian astronaut Tibor Kapu helped bring a theoretical shape called a “soft cell” into physical reality, confirming predictions that were previously impossible to test on Earth.
The soft cell is unlike familiar geometric solids such as cubes or prisms. It has no sharp corners or flat faces. Instead, its surfaces curve inward with saddle-like shapes, formed entirely by fluid behavior and surface tension. Gravity on Earth prevents such a structure from stabilizing, which is why it remained purely theoretical until access to microgravity.
The concept was developed by mathematicians working with the University of Oxford and the Budapest University of Technology and Economics. The shape was identified mathematically only last year, but no laboratory on Earth could reproduce it physically.
To test it in orbit, the Axiom-4 mission carried a lightweight skeletal frame of the soft cell to the ISS. Kapu and mission commander Peggy Whitson filled the frame with water and adjusted the setup in real time, as no established procedures existed. In microgravity, surface tension dominated the fluid behavior, allowing the water to naturally form the predicted concave geometry.
The successful result validated the underlying mathematics and highlighted how microgravity reveals fluid dynamics phenomena that cannot appear under Earth’s gravitational pull. The experiment, initially intended as a simple educational demonstration, produced striking visuals and quickly went viral after being shared online.
Researchers described the outcome as a rare case where abstract mathematics, fluid physics, and spaceflight converged. ISS commander Takuya Onishi reportedly referred to the demonstration as “the art of science,” reflecting how the experiment blurred the line between scientific proof and visual elegance.
Beyond its aesthetic appeal, the soft cell confirms new ways surfaces can organize themselves when gravity is removed from the equation. It reinforces the role of space stations as not just platforms for applied research, but as laboratories for testing fundamental ideas in mathematics and physics that are unreachable on Earth.
