Why astronauts age more slowly in space: Here’s how much younger stranded explorers will be when they return to Earth

It’s a whole other kind of space age.

Astronauts Butch Wilmore and Suni Williams are stranded on the International Space Station until at least February because of their faulty Boeing shuttle — but there’s an upside to their extended adventure in orbit.

The pair will return slightly younger than they would have been if they had stayed on Earth.

That’s because the European Space Agency says six months on the International Space Station (ISS) saves 0.005 seconds of aging.

But while the pair may only shave a fraction of a second off their Earth age, the concept is still incredibly intriguing.

As Albert Einstein’s theory of relativity explains, the closer a person gets to the speed of light (about 300 million meters per second), the faster time passes and the slower age passes.

The ISS orbits the Earth at a speed of 27,500 kilometers per hour, according to the BBC.

There is also gravitational time dilation, which is related to Einstein’s theory. It causes slower aging the farther a person is from the Earth’s core due to weaker gravity and the curvature of the planet.

Subtle changes in time due to the denser passage of gravity on Earth’s surface are a major reason why experts are calling for the Moon to be given its own time zone – as even the planet’s best atomic clocks will be out of whack. of a second in time.

Researchers at Texas A&M found that this small delay also affects people on top of buildings and skyscrapers.

Regarding human aging, NASA previously studied the effects of space by researching biological changes in twin astronauts Mark and Scott Kelly.

While they both spent time on the ISS, Scott had spent about ten times as much time in space as his brother Mark, who was born six minutes before Scott.

The study found that Mark was five milliseconds older than his brother due to the extended time Scott had spent in space at higher orbital speeds among other factors.

What does it mean for the human body at home?

While in an astrophysical sense, astronauts could shave milliseconds off their age, space can take years, if not a decade, away from their bone health upon returning to Earth.

“Long periods in space damage bone structure in some cases irreparably and can cause parts of the human skeleton to age prematurely by up to 10 years,” according to a 2022 study from the Gemrany University of Erlangen – Nuremberg.

In a study of 17 astronauts, nine of them had not fully healed a year after their mission and showed “a reduction in bone strength” and a drop of up to 2% in bone mineral density.

“This may not sound like much, but it corresponds to at least a decade of age-related bone loss,” said researcher Anna-Maria Liphardt.

“For those affected, this means they will have to expect a much earlier onset of osteoporosis and susceptibility to fracture.”

In addition, extended stays in space put astronauts at prolonged risk of absorbing radiation doses, putting them at risk of developing cancer, the Japan Aerospace Exploration Agency warns.