Reason why you age slower in space as before and after photos of stranded astronauts reveal shocking impact of being stuck for nine months

Butch Wilmore and Suni Williams' time on the International Space Station won't have just had negative affects on their bodies.

After over nine months onboard the ISS, Wilmore and Williams safely landed back on Earth on Tuesday (March 18).

The duo were only meant to be up in space for a few days, but their trip was dramatically extended due to technical difficulties with their Boeing capsule and it was deemed unsafe to carry them home.

But they've now safely landed back on their home planet with the help of SpaceX, and were greeted by an unexpected welcome party when they landed in the ocean off the Gulf Coast — a pod of dolphins.

Now they're back, Williams and Wilmore face 45 days of rehab and are set to undergo health tests before they can return to their respective homes.

Their rehab will reportedly include low-intensity exercise and light physical therapy for around two hours per day.

While being up in space for almost ten months will have had negative impacts on their bodies (for example, decreased muscle mass and bone density), there's a positive that will have come with their unexpectedly long stay at the ISS.

Astronauts in space don't age as fast as their Earth-dwelling counterparts, so Williams and Wilmore will now technically be younger than they would have been had they stayed on Earth.

Butch Wilmore and Suni Williams were stuck at the ISS for over 9 months (Joe Raedle/Getty Images)

The difference is only minor, though.

According to the European Space Agency, six months on the International Space Station (ISS) saves 0.005 seconds of aging. Every little helps, I guess?

As to how it marginally slows down the aging process, it all comes down to how a close person is moving towards the speed of light (186,000 miles per second).

Basically, the less time passes the closer to the speed of light you travel relative to someone who is travelling more slowly, BBC explained.

The best example of this was presented by identical twins Mark and Scott Kelly.

Scott and Mark Kelly have both travelled to the ISS for different lengths of time (James Nielsen/Houston Chronicle via Getty Images)

Both of them are astronauts, but Scott spent about ten times longer in space than his brother.

With him spending more time in space in mind, after Scott returned to Earth, Mark was found to be six minutes and five milliseconds older than his siblings, adding five milliseconds on to their age gap (if you can call it that).

Long story short, if you're wanting to slow down the aging process, you're best taking this specific supplement instead of jetting off to space.