Stories about space travel, from which the astronauts return to their grown old friends such as the young, do not excite the creation, many years ago.
However, the passage of time and today the question on the Earth and in the cosmos is not clear to everyone.
Is it possible to return from space young
First, we need to clarify the concepts"Time" and "the rate of aging." As such, the time - a concept invented by man. Counting seconds by an arrow, the days, months and years - all that a person uses for their own convenience. But time itself - an abstract concept. If we talk about the course of time, it is the same everywhere: in space, on Earth or any other planet in the solar system. Likewise, the same would go the aging process of cells and the human body.
Where did the theory that spacepeople do not grow old? It's simple. Referring to the theory of relativity. From the time the location is really independent, but may depend on the speed with which you move. When the vehicle speed exceeding the speed of light, the time it actually slower flow with respect to time, such as on earth. The astronauts themselves will not notice the difference - because their frame of reference is stable: time and space are flowing at the same speed. It's like a train that rushes past the platform: the passengers in the car quietly drinking tea and playing cards, and the people at the station can hardly distinguish their silhouettes - so fast they rush past.
Slowing down time
In the theory of relativity there is another curiousaspect relating to the passage of time on Earth and in space. According to him, the gravity of the planet has some effect on the speed of the flow of time. The gravity is greater, the greater the curvature of space-time at this point, and the slower time flows relative to the observer who is far from a massive body that creates this distortion.
According to this theory, far away from our planetTime will flow a little faster. It may seem that the theory of relativity at this point contradicts itself, but do not jump to conclusions. The fact that the flow rate of time change so little that it can easily be neglected. Most ultra-precise clocks in space a point distant from our planet, because this effect will show with the time difference on the 45900 ns / day faster than a precisely similar clock, set in the world.