Astronaut Scott Kelly Grew 2 Inches in Space After Year-Long Trip Aboard ISS

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 | March 14, 2016 | By Margo Gothelf

After setting a record for his 340-day stay on the International Space Station, astronaut Scott Kelly returned to Earth 2-inches taller.

According to CNBC, Kelly returned to Earth and is now two inches taller than his identical twin brother, Mark. Growing a little is a common sight among astronauts who spend a substantial amount of time in space. Because of the microgravity they are living in, it allows for room in the vertebrae to expand causing a shift in height. NASA explained the phenomena further:

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“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).”

However, once the astronauts return to Earth, their spine shrinks back to its original size. The stretching can only happen in the vertebrae due to the stretchability and compression of the spine, explained a NASA scientist.

Not only did Kelly return taller, but he also aged slower than he would have on Earth. This happens thanks to a process called time dilation. Time dilation means “time moves slower as gravity increases and time moves slower for objects that approach the speed of light. So more gravity and more speed means time passes slower,” explained Mic.

Welcome back to Earth, Scott Kelly. After a year in orbit, Relativity says you’re 1/100 sec younger than you’d otherwise be.

— Neil deGrasse Tyson (@neiltyson) March 2, 2016

Kelly, who was born about 6 minutes after his twin brother, is now about 6 minutes and 10 milliseconds younger than him.

Kelly also announced that he will be hanging up his space suit since returning from his almost year-long mission in space and retiring.

“My career with the Navy and NASA gave me an incredible chance to showcase public service to which I am dedicated, and what we can accomplish on the big challenges of our day,” Kelly shared with NASA. “I am humbled and excited by new opportunities for me to support and share the amazing work NASA is doing to help us travel farther into the solar system and work with the next generation of science and technology leaders.”