ISS Astronauts Age Milliseconds Slower in Orbit as 7.8 km/s Time Dilation Outruns Gravity
Updated
Updated · spacedaily.com · May 17
ISS Astronauts Age Milliseconds Slower in Orbit as 7.8 km/s Time Dilation Outruns Gravity
2 articles · Updated · spacedaily.com · May 17
Astronauts aboard the International Space Station return to Earth slightly younger than if they had stayed on the ground, with the net gap amounting to milliseconds over months in orbit.
At roughly 7.8 kilometers per second and about 400 kilometers above Earth, the station experiences two opposing relativistic effects: weaker gravity speeds clocks up, but orbital velocity slows them more.
Atomic-clock comparisons have repeatedly measured the effect, and NASA’s Scott Kelly came back measurably younger than his twin Mark after nearly a year in space.
GPS shows why the physics matters beyond a curiosity: satellites’ clocks drift by about 38 microseconds a day without relativistic corrections, enough to ruin navigation accuracy within a day.
The report stresses that this does not meaningfully slow biological aging—microgravity, radiation and other spaceflight stresses can instead accelerate some physiological changes even as onboard clocks run slower.
Beyond aging slower, how does altered time flow physically impact astronauts on long missions?
If Einstein's relativity was ignored for a day, how would the GPS failure cascade through our global economy?
As humanity plans for Mars, how will we manage societies operating on fundamentally different timelines?
How NASA’s Twins Study Proved Astronauts Age 0.01 Seconds Slower: The Real-World Science of Time Dilation in Space
Overview
The NASA Twins Study is a real-world demonstration of time dilation, directly supporting Einstein's predictions. In this study, Scott Kelly spent nearly a year on the International Space Station while his identical twin, Mark Kelly, stayed on Earth. The main goal was to carefully observe changes in Scott caused by the space environment and compare them to Mark. After Scott returned, researchers completed a thorough analysis, and a summary paper was released around 2019. This study provided clear evidence that time passes differently in space, confirming the effects of relativity in a human experiment.