The phenomenon of astronauts ageing slightly slower in space is a result of time dilation.
India is buzzing with discussions about astronauts and space ever since Prime Minister Narendra Modi revealed the names of four astronauts involved in the country's human space flight mission, Gaganyaan. This has sparked various space-related questions and facts, with one intriguing tidbit being that astronauts age slightly slower in space.
Why do astronauts age slower in space?
The phenomenon of astronauts ageing slightly slower in space is a result of time dilation, which is a consequence of Einstein's theory of relativity.
According to this theory, time is relative, and it can be influenced by factors such as gravity and velocity.
In space, where gravitational forces are weaker than on Earth, and due to the high velocities involved in space travel, time appears to pass at a slightly slower rate for astronauts.
This effect is known as Gravitational time dilation, and it has been experimentally confirmed with highly precise atomic clocks on fast-moving aeroplanes and in strong gravitational fields. While the difference is extremely small and practically negligible for short space missions, the relativistic effects become more noticeable for astronauts travelling at significant fractions of the speed of light or experiencing intense gravitational fields over extended periods.
To sum up, time moves slower as gravity increases, meaning time passes slower for objects closer to the centre of the Earth where gravity is stronger.
While this effect is not noticeable on a small scale, it becomes more apparent when considering factors like relative velocity time dilation. As objects move faster, time moves slower, exemplified in the twin scenario where one twin travels at near-light speed, and upon return, has aged less than the Earth-bound twin.
This concept gets more complex when both gravitational time dilation and relative velocity time dilation occur simultaneously, as observed on the International Space Station (ISS). Astronauts on the ISS experience both weaker gravity and higher velocity, resulting in slightly slower ageing compared to people on Earth.
The European Space Agency (ESA) explained in a tweet that “after spending six months on the ISS, astronauts have aged about 0.005 seconds less than the rest of us.”
So if you ever wish the weekend could stretch a bit, just stick to the ground and run really fast. It won't make your weekend feel longer, but you might technically gain a tiny bit of a second.