Introduction: A Week in Microgravity
During the week of November 17–21, 2025, the International Space Station buzzed with activity as the Expedition 73 crew carried out routine science, maintenance, and a practical demonstration that captures the imagination of space enthusiasts worldwide: weighing yourself in space. With gravity in a jointed orbit around Earth and mass being a constant, how do astronauts measure weight when weight as we know it on Earth doesn’t apply? The answer lies in a combination of physics, precise measurement tools, and a dash of astronaut ingenuity.
How Weighing Works in Microgravity
In microgravity, weight as a force is almost negligible, but mass remains constant. Astronauts use balance-like devices and accelerometers to infer mass, relying on the relationship between force, acceleration, and motion to determine how much matter is aboard an EVA suit, a cargo bag, or even a human body. The crew’s demonstration shows that while you don’t “feel” weight in space the way you do on Earth, you can still determine mass by measuring how an object resists acceleration within a controlled environment.
The ISS Demonstration: A Simple, Safe Procedure
The demonstration is designed to be safe, simple, and repeatable. A trained crewmember places the subject (a crew member or a safe surrogate) on a calibration platform connected to a high-precision sensor array. By applying a known, gentle force and recording the resulting motion, technicians calculate mass with a level of precision suitable for scientific experiments and daily health monitoring onboard the station. The method is not about vanity but about tracking body composition changes, fluid shifts, and overall health during extended stays in space.
Why Mass Matters on the ISS
Mass is a fundamental parameter for health and mission planning. Astronauts undergo regular checks to monitor bone density, muscle mass, and fluid balance—all factors that evolve in microgravity. Although the scale isn’t used for Earth-like weight loss programs, knowing how mass changes over time helps researchers understand how spaceflight affects the human body. It also informs adjustments to exercise regimens and nutrition to keep astronauts mission-ready for long-duration flights.
Training and Public Engagement
Beyond the lab, the weigh-in concept serves as an excellent educational tool. NASA and partner agencies often share demonstrations to inspire students and the public to think critically about physics and human physiology in space. The Expedition 73 crew’s week includes orbital observations, maintenance tasks, and outreach activities that highlight the practical realities of life aboard a spaceship circling Earth.
A Look at Expedition 73: Who’s on Board
Expedition 73 represents a multinational crew collaborating in a shared environment. The crew members work together to conduct experiments, repair systems, and ensure the station remains a stable platform for research. The weigh-yourself demonstration is one of several hands-on activities that showcase the day-to-day life of astronauts living in weightless conditions and their methodical approach to science and exploration.
Conclusion: A Small, Big Insight
While the concept of weighing yourself in space might seem minor, it encapsulates the broader ethos of human spaceflight: leveraging simple tools and clear physics to maintain health, advance science, and connect with people back on Earth. The ISS mission continues to blend routine duties with moments that illuminate how science translates into everyday understanding—even when gravity isn’t doing the heavy lifting.
