Well, you must know that when astronaut Scott Kelly was in space, he aged less in reality as compared to his twin brother on Earth. His twin brother who is 6 seconds older than him stayed on Earth and it was observed that in fact, he turned a little more older as compared to Scott owing to relativity. As proposed by Einstein, time moves slower for objects in motion as compared to those at rest. Scott’s brother on Earth, Mark, experienced time at somewhat faster pace than Scott who was orbiting around Earth. Therefore, in short, everyone does not live through time at the same rate.
As per Science Alert, while Scott’s brother was relatively sitting still on Earth, Scott was orbiting Earth in the ISS at around 17,500 mph. This accounted for older twin Mark to live for 5 extra milliseconds when compared to Scott. When born in 1964, they were born 6 seconds apart. Currently, they are 6 seconds and 5 milliseconds apart.
The twins have been under study by NASA because of the fact that one is an astronaut, which offers fascinating opportunities for research. Due to the fact that the two of them are legitimately similar, NASA is mainly looking at any way Space could possibly affect stature or physiology.
When Scott returned from the ISS, Mark stated:
“If 10 years from now, I look like I’m 60 and he looks like he’s 80, you’ll know what happened.”