The mass expands or shortens space-time

Time stretching

April 8, 2017, 9:58 pm

Time stretching is an essential consequence of both the Special (SRT) and the General (GTR) relativity theory. According to the theory of relativity, time passes at different speeds in different frames of reference, since its course is influenced by the movement of the observer and gravity.

According to Einstein's SRT, the flow of time in a stationary reference system runs differently than in a system that moves relative to the observer. The faster it moves, the slower the time in a reference system: Moving clocks tick more slowly than chronometers that are at rest relative to them - for example in a very fast moving spaceship.

This relativistic effect has nothing to do with a mechanical disturbance of clocks, but is a property of time itself, which is called "time dilation" or "time stretching". In the theory of relativity, all inertial systems have equal rights, which is why we always see the clock moving relative to us going slower.

Time stretching affects all natural processes

Time expansion affects all natural processes, including the aging of human cells. A fast-flying astronaut therefore ages more slowly than a person on Earth. Since this time expansion only becomes significant at speeds close to the speed of light (approx. 300,000 km / s), it does not play a role in everyday life, apart from a few exceptions (e.g. with the satellite navigation system GPS).

Nevertheless, time dilation was proven experimentally as early as the 1970s. After several days of flight around the world in a westerly direction, four atomic clocks that were carried along were actually several billionths of a second behind the atomic clocks resting on the ground.

Until the standstill of time

According to the ART, however, gravity also influences the flow of time. The stronger the force of gravity in a reference system, the more slowly clocks tick, i.e. the closer they come to celestial bodies. This time expansion has an effect in the universe above all in the vicinity of very massive cosmic objects. If we could observe an astronaut approaching a black hole, we would notice a steadily increasing time expansion that becomes infinite at the event horizon of the black hole. From our point of view, the astronaut's time would literally stand still there.

But even on earth, the time expansion caused by gravity has an effect, but again only in tiny values. According to the ART, a person's head ages seven seconds faster than their feet in a billion years because they are closer to the ground, where a slightly stronger force of gravity acts. Admittedly, an effect of the theory of relativity that is negligible for practical life, but still real.

The so-called spacetime

In addition to length contraction (moving bodies shrink), time dilation is the most important consequence of SRT. Both relativistic effects are two complementary forms of one and the same physical phenomenon. In the special theory of relativity, time and space are not separate terms, they rather form a four-dimensional unit, the so-called spacetime. In moving systems, time expands by the same factor as space is shortened.

In Newton's classical physics, time was a uniform metronome that assigned the same measure to all processes in nature, an absolute and unalterable quantity in the universe. On the other hand, Einstein's theory of relativity showed that time (and also space) is a variable that depends on the movement of the observer. This gave the term "time" a relative meaning in physics and in the universe.