ISS astronaut Norishige Kanai (first from right) grew 9 cm taller in only 3 months in space. Credit: NASA.

Free from the pressure of gravity, the spine can relax and temporarily expand almost like an unwinded coiled spring. This is why all astronauts stationed at the International Space Station grow taller during their stint there. But the case of Japanese astronaut Norishige Kanai, who arrived at the station on Dec. 19, 2017, was extreme by all accounts, though. In the three weeks since he arrived at the ISS, Kanai claimed he had grown a staggering 3½ inches (9 centimeters) — the most he’s “grown in 3 weeks since junior high school,” the astronaut tweeted.

Typically, a normal stint at the International Space Station will see people grow about two inches taller. But every human body is different and sometimes you get these freak occurrences at the high end of the bracket.

“Good morning, everybody,” Kanai wrote on twitter. “I have a major announcement today. We had our bodies measured after reaching space, and wow, wow, wow, I had actually grown by as much as 9cm!”

みなさま、おはようございます。今日は重大なご報告があります。

実は、宇宙に着いてからの身体計測があったのですが、な、な、なんと、身長が9センチも伸びていたんです！
たった3週間でニョキニョキと。こんなの中高生のとき以来です。

帰りのソユーズの座席に体が収まるか、ちょっと心配です。

— 金井 宣茂 (@Astro_Kanai) January 8, 2018

“I am a little worried I won’t fit in my seat on the return trip on Soyuz,” Kanai said more jokingly than serious.

Each seat on the Russian Soyuz TMA spacecraft actually molds to the body of each astronaut to ensure a tight fit during atmospheric re-entry which can be quite the bumpy ride. You can’t be taller than 6 feet 3″ to hitch a ride, which is why anyone around that limit isn’t allowed to the ISS.

After receiving so much media coverage, Kanai’s captain questioned the astronaut about his height and the two performed a new measurement. Turns out Kanai’s initial measurement was WAY off. Apparently, the 41-year-old Japanese astronaut had stretched only 2 cm from his Earth-bound height.

Kanai tweeted: “This mis-measurement appears to have become a big deal, so I must apologize for this terrible fake news … It appears I can fit on the Soyuz, so I‘m relieved.”

Kanai didn’t explain how he arrived at this ‘mis-measurement’ but it sure is weird  After all, he is an astronaut — a person who is trained in avionics and space engineering, which should entail being able to tell an inch from three inches.

The real talk

If growing a couple inches taller might sound appealing to some of you, know that it’s only temporary since astronauts slip back to their normal height once they touch down on Earth. Actually, growing taller can only mean trouble in space where every cubic inch counts.

Growing tall on the ISS is a fleeting experience but there are really far more concerning effects zero gravity has on the human body. Scientists are only beginning to understand what long-term weightlessness is doing to human biology but already we know some things aren’t good at all. For instance, astronauts hurt their vision since the retina gets pushed forward, arteries can become clogged due to plaque buildup, and thousands of genes switch on and off. 

If humanity ever becomes a space-faring species, we shall have to confront the effects of weightlessness and conquer them. In the meantime, stints made by brave astronauts on the ISS will teach us many valuable lessons.