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Albert Einstein came to the rescue of a lecture given by the mathematician Hermann Minkowski in September 1908.

The views on space and time that i would like to develop for you have grown up on experimental physical ground. That is their strength. Their tendency is a radical one. From hour to hour space and time should sink completely to shadow for themselves and only a kind of union of the two should preserve independence. The object of our perception is always only places and times connected. Nobody noticed a place differently than at a time, a time differently than at a place. I want to call a point in space a point, in time a point in the world. We then receive a curve in the world, a world line, as an image for the eternal cycle of a point. The whole world appears dissolved in such world lines. The laws of physics find their perfect expression as interrelations between these worlds.

With the lecture our world had suddenly become four dimensional and space and time were inextricably linked, the four dimensional space-time continuum was created.

The head of the researcher Albert Einstein now bumped into the geometry of the Göttingen mathematician Bernhard Riemann. Around the middle of the nineteenth century, Riemann had mathematically worked out the geometry of curved surfaces and created a measure for the curvature of a space. Thus a stone in the position gravitation was to be described as geometric property as curvature of the four dimensional space-time. The general theory of relativity was born with it and with it a completely new understanding of the phenomenon of gravity, gravitation as the geometric curvature of four dimensional space-time.

When an elevator moves, its movement immediately falls into the geometry of space-time and no force is exerted on the objects in the elevator. Gravitation can therefore be eliminated by choosing a suitable reference system, such as the free-falling lift here. Gravity therefore proves to be an apparent force.

Einstein's equations describe how the bodies have to move in curved spaces and how this curved geometry is related to the mass of the bodies. This is the new idea of gravitation. A satellite moves in a straight line through a curved space.

But how can you imagine the curvature of a four-dimensional space? Let's take a simplified example of a two-dimensional surface. For example a stretched rubber blanket. The mass of a body causes an indentation in our surface. The heavier the body, the deeper it will bend the geometry of our rubber blanket. If a planet orbits a star, it follows the curvature of space time, the gravitational force no longer exists.

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