## Definition of spacetime

In physics, spacetime is a mathematical model that combines three dimensions of space and one dimension of time in a single four-dimensional freeze sequence. Spacetime diagrams can be used to visualize relative effects, such that its use allows different reviewers to see where and when events occur differently.

## Spacetime concept in the 20th century

By the 20th century, there was the notion that the three-dimensional geometry of the universe (its spatial expression in terms of coordinates, distances, and directions) was one-dimensional time. But in 1905 Albert Einstein based his seminal work on special relativity on two terms and he stated –

- The laws of physics are invariant in all inertial systems (ie non-accelerating frames of reference) (ie are the same).
- The speed of light in the vacuum is the same for all reviewers, regardless of the speed of the light source.

The logical consequence of taking these positions together is inseparable along the four dimensions. Which leads to many counterintuitive results such that, apart from being independent of the speed of the light source, the speed of light has the same speed regardless of the frame of reference in which it is measured; The temporal order of distances and even pairs of events when measured in different inertial frames of reference (this is simultaneous relativity) and the linear additivity of velocities are no longer correct.

### Kinematics (study of moving bodies)

Einstein formulated his theory in the context of kinematics (the study of moving bodies). His theory was a breakthrough advance on Laurentz’s 1904 electromagnetic phenomena and Poincaré’s electrodynamic theory. Although these theories included equations similar to those introduced by Einstein (i.e., Lorentz transformation), they were essentially models proposed to explain the results of various experiments – including the famous Michelson – Morley interferometer experiment – which currently exists It was very difficult to fit.

In 1908 Hermann Minkowski — once one of the young Einstein professors of mathematics in Zürich — presented a geometric interpretation of special relativity, describing three spatial dimensions of time and space in the same four-dimensional continuum as Minkowski’s space. Is known. A key feature of this interpretation is the formal definition of spacetime intervals. Although measurements of distance and time between events differ for measurements taken in different reference frames, the spacetime interval is independent of the inertial frame of reference in which they are recorded.

### Minkowski’s geometric interpretation of relativity

Minkowski’s geometric interpretation of relativity was instrumental to Einstein’s development of his 1915 general theory of relativism, in which he showed how large-scale and energy curves are for this pseudo-Reimanold manifold over this flat lifetime.

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