What is Minkowski spacetime

Inventor of the four-dimensional space-time

"Oh, Einstein, he always skipped lectures - I wouldn't have thought he could."

A former teacher of Albert Einstein at the Polytechnic in Zurich was the mathematician Hermann Minkowski. Minkowski, the son of a German-Jewish merchant family in Lithuania, studied in Berlin and Königsberg and in 1902 received a professorship in Göttingen, the Mecca of German mathematicians. His main interest was actually the geometry of numbers, but from 1905 he dealt with a new theory - the special theory of relativity. Einstein had just developed this by performing thought experiments. For example, he had wondered what would happen if someone could travel at almost the speed of light. Would his watch still work the same way as that of a resting observer? Claus Kiefer, head of the Institute for Theoretical Physics at the University of Cologne, knows the result of these speculations.

"That is, if you have a watch and you look at that clock and if you are moving at high speed now, the clock will run differently compared to your colleague who is at rest. That is, if you come back and compare your watches , then they will no longer match, even if they originally left the same. That means the time also depends on the state of motion, so also on space, because when you move, you are walking through space. So space and Time are no longer separate things. "

Einstein's considerations sprang from his vast physical imagination. He had put them on paper in algebraic equations such as the famous E = mc². The mathematician Minkowski now recognized that the theory could also be formulated more simply by describing it geometrically. He gave a lecture on this in 1908 in Cologne. Its introductory sentences are among the most cited in the history of science:

"Gentlemen! The ideas about space and time that I would like to develop for you grew up on experimental-physical soil. This is their strength. Their tendency is radical. From that moment on, space for itself and time for itself should be completely in shadow sink and only a kind of union between the two should maintain independence. "

"This lecture is so famous because it practically introduced four-dimensional space-time into physics. Minkowski has recognized that Einstein's equations can be written down and understood particularly beautifully and elegantly if one uses four-dimensional space-time instead of three-dimensional space and one-dimensional time. And that is what he presented in Cologne with his famous lecture in September 1908. "

Minkowski thus provided Einstein's physical speculations with a mathematical basis. He realized that Einstein's equations could also be represented as a diagram with the three spatial coordinates x, y, z and the time coordinate t. To this day, such so-called Minkowski diagrams are a matter of course for every theoretical physicist. Einstein himself was not at all enthusiastic at first, however.

"Since the mathematicians accepted my theory, I no longer understand it myself."

That soon changed, however. Because Einstein realized that Minkowski's concept of spacetime could help him to solve the problem of gravity. Because physicists had known the laws of gravity since Isaac Newton, but were faced with the embarrassing problem that they had no idea what gravity actually was. Only Einstein created a theory in 1915 ...

"... in gravity, as with Newton, there is no longer simply a force between masses, but geometry. In fact, the geometry of a spacetime which, when gravity is present, is quasi curved Minkowski has just introduced that. "

In his general theory of relativity, Einstein claimed that a mass the size of the sun must be able to bend the space-time that surrounds it, and that it is this curvature of space-time that creates what we perceive as gravity. Experimental proof of this claim came four years later when a total solar eclipse was observed off the West African coast. Only then did Albert Einstein become the science superstar we know him to be today. But this is another story. And Hermann Minkowski did not live to see her either, because he died on January 12, 1909, at the age of only 44, of a ruptured appendix.