Astronauts Grow Up to 3% Taller in Space

Imagine waking up one morning and discovering you're two inches taller. That's exactly what happens to astronauts living aboard the International Space Station. In the weightless environment of space, the human spine gets a chance to really stretch out—literally.

A six-foot-tall astronaut can grow up to 3% taller, gaining nearly 2 inches during their mission. Astronaut Kate Rubins, for example, went from 5'6" to 5'7" while orbiting Earth. It's like getting a free growth spurt, except it comes with some unexpected baggage.

Why Zero Gravity = Extra Height

On Earth, gravity constantly compresses your spine. All day, every day, the weight of your upper body presses down on the intervertebral discs—the squishy cushions between your vertebrae. In space, that constant squeeze disappears.

Without gravity pulling everything downward, those compressed discs absorb fluid and expand like little sponges. The vertebrae spread slightly apart, the natural curves in your spine straighten out a bit, and suddenly you're looking down at crewmates who used to be your height.

NASA researchers have actually measured this using ultrasound, scanning astronauts' spines at different intervals during missions. The elongation happens quickly—within just a few days of reaching orbit.

The Not-So-Fun Part

Before you start dreaming of a space vacation for that height boost, there's a catch. About 70% of astronauts experience back pain shortly after arriving in space, and roughly half deal with discomfort when they return to Earth.

Here's why: while your spine is stretching out, the muscles that normally support it are taking an extended vacation. With no gravity to fight against, these muscles can atrophy by an average of 19% during a mission. Your spine gets longer, but the muscular support system gets weaker—not exactly an ideal combination.

Some astronauts describe the sensation as their spine "unzipping" in space. Others report a strange pulling feeling as their body adjusts to its new, temporarily taller configuration.

Coming Back Down to Earth (Literally)

The extra height doesn't last. Once astronauts return home and gravity reasserts its dominance, the spine gradually compresses back to its normal length. The process takes anywhere from a few days to a few months.

The intervertebral discs release their extra fluid, the vertebrae settle back into their usual positions, and any dreams of reaching items on high shelves fade away. Within weeks, astronauts are back to their pre-flight height, though some report lingering back soreness as their bodies readjust.

It's one of the more peculiar side effects of space travel—a temporary transformation that reminds us just how much our bodies rely on gravity to maintain their shape. The human spine, it turns out, is like a spring that's been compressed for your entire life. Remove the weight, and it naturally expands. Add it back, and everything returns to normal.

So yes, space really does make you taller. Just don't expect to keep those extra inches once you land.