Why Astronauts Grow Taller In Space? Science Behind ‘Space Height’ And How The Body Changes

Scientists have long known that space travel affects the human body in many unusual ways. From DNA changes to vision problems, astronauts experience several physical transformations while living in space. Most of these changes happen because of microgravity, a condition where the pull of gravity is extremely weak compared to Earth.

Without Earth’s gravity, the human body begins to behave differently. Astronauts start to lose bone density, and their muscles slowly shrink because they are not being used the same way as on Earth. Their weight, immune system, cardiovascular health and even their DNA can be affected. Some astronauts also suffer from coordination issues, poor balance and reduced motor control, which increases the chances of injury.

One of the most surprising changes, however, is that astronauts actually become taller in space. NASA says astronauts can grow up to 3 per cent in height while living in microgravity. For example, astronaut Kate Rubins grew from 5 feet 6 inches to a “space height” of 5 feet 7 inches during her mission.

The reason behind this increase is the effect of microgravity on the spine. On Earth, gravity constantly compresses the spine, keeping it slightly pressed together. In space, without this pressure, the spine relaxes and stretches out. The vertebrae move apart a little, causing astronauts to become temporarily taller. NASA explains that these spinal changes can also alter body measurements like sitting height, eye height and the way spacesuits fit.

Along with growing taller, astronauts experience a shift in bodily fluids. Fluids move upward toward the head, which results in a “puffy head”, while the legs appear thinner, a condition often called “chicken legs”.

But this extra height does not last long. Experts say the growth is temporary, and astronauts return to their normal height a few months after landing back on Earth. Once gravity starts working on the spine again, it compresses naturally, reversing the space-induced growth.