With extremely controlled and strict diets, it's not like astronauts have to worry about gaining too much weight on the space station. But have you ever stopped and wondered how you would actually measure mass in a weightless environment? After all, the entire concept of weight and scales is entirely dependent on gravity.
It turns out you can, you just need a stand-in for the constant force that keeps us all glued to the ground when we're on Earth. And as astronaut Don Pettit demonstrates, a low-tension spring fills that void when gravity isn't strong enough to be felt. But measuring the mass of an object this way isn't as easy as just looking at a number on a scale. In this instance, you need to measure the object's oscillations over time as it swings back and forth and fights against the spring. The faster it moves, the lighter an object is—and with proper calibration and calculations, you should be able to accurately determine if it's time to lay off that freeze-dried astronaut ice cream. [YouTube]