Here's why astronauts age slower than the rest of us here on Earth

Time is one of the only constants in the world.

Albert Einstein ruined that for us.

It can be hard to wrap your head around what "time is relative" really means.

The idea of space-time was created by Einstein's Theory of Relativity, which joined space and time.

In space-time, we measure our experience in different ways. Space-time can be warped by matter and energy.

For astronauts on the International Space Station, that means they get to age a little slower than people on Earth.

The time-dilation effects are what made that happen. Time seems to move slower near large objects because of their gravity.

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The phenomenon is called gravity. Time is moving slower as gravity increases.

Time passes more slowly for objects closer to the center of the Earth.

You can't spend your life in a basement just to live longer than the rest of us. It's not noticeable on a small scale. You would only age a fraction of a second slower if you became a basement hermit.

When you start thinking about it, this concept becomes crazy.

• A watch strapped to your ankle will eventually fall behind one strapped to your wrist.
• Your head technically ages more quickly than your feet.
• Time passes faster for people living on a mountain than those living at sea level.

The time gets weirder.

The second factor is called "relative velocity time dilation".

There is a classic example of this. One twin blasts off in a spaceship and the other stays on Earth. When the space-traveling twin returns to Earth, she's only two years older than her sister, but she's shocked to see that she has aged over a decade.

There is evidence that it is real, even though no one has done that in real life. While keeping an identical clock here on Earth, the atomic clock came back running slightly behind the Earth bound clock.

At the same time, time can get even more complicated due to the fact that time can be divided into two parts. The International Space Station is where the astronauts live.

The International Space Station has a crew of seven who live and work every 90 minutes.

The Earth's gravity is weaker than it is at the surface. Time should be quicker for them compared to people on the ground. The space station is moving at a rate of about five miles per second.

Time should be slower for the astronauts relative to people on the surface.

They end up aging slower than people on Earth due to the fact that astronauts have a bigger effect on their velocities than people on Earth.

After six months on the International Space Station, astronauts have aged less than the rest of us.

Scott Kelly was the younger of the two brothers when he returned home in 2016 after a year on the International Space Station.

If you want the weekend to last longer, stay low to the ground and move quickly. You may gain a tiny fraction of a second, but it won't feel like you've lost any time.

Time is not a linear thing.