Astronauts come home from the space station up to two inches taller than when they left — without gravity compressing it, the human spine slowly stretches out in orbit, and NASA has to allow room to grow in flight suits, though the extra height vanishes within months back on Earth as each vertebra settles into place

The mechanismThe human spine is designed to be compressed. Flight suits — both the pressure suits worn during launch and reentry, and the extravehicular activity suits used during spacewalks — are fitted to specific astronauts before launch. Every seam has to line up with a specific body position. Over the following days and weeks, the astronaut’s height gradually returns to their pre-flight baseline. The specific mechanical shape of an adult human body reflects tens of thousands of years of evolution under one specific set of load conditions.