Astronaut Scott Kelly Grew 2 Inches in Space and Aged Less Than People on Earth

Astronaut Scott Kelly Grew 2 Inches in Space and Aged Less Than People on Earth Image Credit: NASA

Astronaut Scott Kelly Grew 2 Inches in Space and Aged Less Than People on Earth

After 340 days on the International Space Station, Scott Kelly grew 2 inches taller than his twin brother who spent the time on Earth, CNBC reports.

Gaining a couple inches is pretty common among astronauts who spend a significant amount of time in space. That’s because the microgravity environment allows room for their vertebrae to expand.NASA explains it:

NASA’s explaination:

Imagine that the vertebrae in your back form a giant spring. Pushing down on the spring keeps it coiled tightly. When the force is released, the spring stretches out. In the same way, the spine elongates by up to 3% while humans travel in space. There is less gravity pushing down on the vertebrae, so they can stretch out — up to 7.6 centimeters (3 inches).

Once astronauts get back to Earth, their spine eventually shrinks back down to its original length. This phenomenon doesn’t happen anywhere else in the body because no other bones are as stretchable and compressible as the spine, according to NASA scientists.

Kelly landed on Tuesday (in Eastern time), so his spine has likely already compressed back down to its original length. So Kelly’s height change isn’t permanent, but there’s another bizarre change that will be. After 340 days in space, he aged a few milliseconds slower than he would have on Earth.