# What explains the curvature of space-time

Space-time curvature describes the structure of space and time. It assigns gravity (basic physical force) only the secondary role as a geometric property of curved space-time.

The discovery and description of space-time curvature is the result of Einstein's general theory of relativity. That changed the physical world forever. It describes the structure of space and time and their connection. Masses cause space-time to bend - they stretch time. The general theory of relativity is also about the interaction of gravitation and centrifugal force based on the consideration of accelerated body masses. Let's start with gravity.

Einstein does not describe gravity as a force, but as a property of spacetime. That's a huge difference. To this day, gravity is considered a basic force in physics. If a mass body moves along the shortest path on a straight line through space and enters the sphere of influence of a second, its path is curved and becomes a geodesic. The greater the mass of the influencing body, the greater the curvature. This is the effect of space-time warping. The curved path (geodesy) is the shortest distance that the body can cover within curved space-time. This applies to all of cosmic mechanics. Also on the orbit of the moon around the earth!

This effect has already been proven with atomic clocks. One clock was placed on the ground, the other on a high mountain. What happened? The clock on the ground showed a different time than the one on the mountain: it was lagging behind. Time passed faster on the mountain than on the ground. Heavy clocks are slowing down. Hence, mass influences time. Another derivation from the special theory of relativity. We are dealing here with the same effect that occurs when approaching the speed of light. According to Einstein, gravitation is simply the effect that is derived from the distortion of space-time.

This is illustrated graphically in the picture above. A large mass (in this case the earth) is in space. Due to its mass, it bends time (this is the grid-shaped, dented rubber blanket). Let us assume that a grid represents a certain time unit in the unstretched normal range, for example one second. Near the earth the clocks tick more slowly (grid is stretched apart) - further away they tick faster (even second grid). If a flying object now comes by, its (previously straight) path aligns according to the curved space-time - it is deflected and accelerated around the larger mass body. In the time of the influence (orbit curvature) by the larger mass body, the time for the flying object now passes slightly more slowly than before entering the curvature sector. That explains the change in flight direction. So time and place are mutually dependent.

The second important approach of general relativity relates to the effect of centrifugal force (centrifugal force). Let's take a strongly rotating disk. If you place a clock on its edge - which is exposed to a very high acceleration - it goes slower than the clock, which is arranged near the center of the disc. Why? The effect of centrifugal force and gravity is identical. The clock on the edge experiences the same effect through centrifugal force, we through a correspondingly strong gravity: Fast clocks slow down. This was also proven by measurement. Clocks on the earth's equator run more slowly than clocks on the poles. Of course, the difference is only billionths of a second and not weeks. But the time difference really does exist.