- Time may appear faster or slower to us than to other people in another part of space-time.
- This means that astronauts on the International Space Station age slightly slower than Earthlings.
- According to one study, astronauts on long missions “may be subject to unique stresses that affect human aging.”
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Time seems to be one of the only constants in life: it passes day by day at the same rate.
But Albert Einstein spoiled it for us.
We’ve all heard the phrase “time is relative,” but it can be hard to understand what it means.
This phrase comes from Einstein’s theory of relativity, which connected space and time and created the idea of the fabric that permeates the entire universe: “space-time”.
The relationship between space-time and how astronauts and people on Earth age
We all measure our experience of spacetime differently. This is because space-time is not flat, but rather curved, and can be warped by matter and energy.
Depending on our position and speed, time may seem faster or slower to us than to other people in another place from spacetime.
For astronauts on the International Space Station (ISS), this means that they age slightly more slowly than humans on Earth.
This is due to the effects of time dilation. First, time appears to move slower near massive objects because the object’s gravitational pull warps space-time.
This phenomenon is called Gravitational time dilation. Simply put, this means that time moves slower as gravity increases.
This is why time passes more slowly for near-geocenter objects. There, gravity is stronger.
This does not mean that you can spend your life in a basement to outlive us here on the roof. The effect is not noticeable on such a small scale.
If you were to become a hermit in a basement, you would only age a fraction of a second slower in your entire life than the rest of the people on the roof.
But this concept gets interesting when you start to think about it:
- A watch strapped at the ankle will eventually fall behind one strapped at the wrist.
- Technically, the head ages faster than the feet.
- Time passes faster for people who live on mountains than for those who live at sea level.
But time is weirder.
The second factor is what is called “relative velocity time dilation”, and at what time Slower The faster we move.
The classic example is that of twins. One of them is thrown into a spaceship traveling at nearly the speed of light and the other remains on Earth. When the space traveler returns to Earth, he is only 2 years old, but he is shocked to discover that his brother on Earth is actually 10 years older.
Of course, no one has ever done such an experiment in real life, but there is evidence that it will. When the scientists launched an atomic clock into orbit and set it back, keeping an identical clock on Earth, it moved back a little behind the Earth clock.
Why do astronauts age at different rates?
In this case, time is more complex because gravitational time dilation and relativistic velocity time dilation can occur at the same time. A good way to think about it is to think about how old the astronauts who live on the International Space Station are.
According to NASA, an international crew of seven currently lives and works aboard the International Space Station, orbiting Earth every 90 minutes.
It floats at an altitude of about 419 kilometers, where Earth’s gravity is weaker than at the surface. This means that time must speed up for them as for people on the surface. But the space station is also orbiting Earth at a speed of about eight kilometers per second.
This means that time should also slow down for the astronauts compared to people on the surface.
You might think this is a parody, but it’s actually time dilation for speed It has a greater effect than gravitational time dilation, so astronauts age slower than humans on Earth.
However, the difference is unnoticeable: After spending six months on the International Space Station, astronauts have 0.005 seconds less lifespan than the rest of us.
This means that when NASA astronaut Scott Kelly (now retired) returned home in 2016 from his historic year-long stay on the International Space Station, he was 0.01 seconds younger than his astronaut twin brother – and now US Senator – Mark Kelly. , who remained on Earth.
So the next time you want your weekend to last longer, stay low to the ground and move real fast. It won’t feel like the weekend has dragged on, but technically you might gain a fraction of a second.
Remember that time is relative.
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