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Gravity is an essential force on Earth: It keeps the planet in orbit at a safe and comfortable distance from the sun, and even holds our atmosphere in place. It does have a downside, however: It weighs down the human body, making us a tiny bit shorter by the end of the day. From the moment we climb out of bed in the morning, gravitational forces push down on us, applying downward pressure on our joints, compressing our spines, and causing our organs to settle. All that strain adds up, enough to shrink a body by 1 centimeter. Gravity is at work whether we’re sitting or standing, but at bedtime, our bodies get a slight reprieve as lying down redirects the force. Sleeping horizontally gives our spines and joints time to decompress and gain back the height lost during the day, making us once again slightly taller by morning.
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It's a factAt birth, humans tend to have 33 vertebrae — the individual bones that make up the spinal column. By adulthood, many of those bones have completed the normal process of fusing together, leaving the average adult with just 24 vertebrae.
Even though this ebb and flow is a normal process our bodies endure, over time humans tend to shrink in stature. The human body constantly breaks down and replenishes its bones to keep them healthy, though by age 35, that process tends to slow, with bones breaking down faster than they rebuild. The aging process also causes the cushions between our bones to retain less water and deteriorate, which makes the bones settle together. These processes slowly chip away a few millimeters of height at a time, which can eventually add up — on average, men tend to lose an inch of height between 30 and 70 years old, while women can lose up to 2 inches.
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Astronauts get taller in space.
Most people reach their maximum height by early adulthood — unless they’re astronauts. That’s because scientists who rocket into space for extended periods tend to grow about 3% taller during their time off Earth. In astronaut Scott Kelly’s case, a 340-day trip aboard the International Space Station gave him the souvenir of around 2 additional inches of height. NASA research on astronaut bodies shows that while in space, the spine’s vertebrae decompress and relax, giving space explorers the benefit of added height. However, that increase in statute is temporary; once back on Earth, the planet’s gravitational forces are back in play, causing those extra inches to disappear.
Interesting Facts writers have been seen in Popular Mechanics, Mental Floss, A+E Networks, and more. They’re fascinated by history, science, food, culture, and the world around them.
