In the field of physics, space-time gives us a mathematical model that consists of a three-dimensional figure of space and one dimension of time into one 4-dimensional continuum. The diagrams of space-time help in the visualization and the deeper understanding of the relativistic effects like how the different observers perceive the occurrence of events (when and where).

Until the onset of the 20^{th} century, there was the only three-dimensional geometry of the universe which was distinct from the time i.e. the occurrence of events within the time. However, with Einstein’s special theory of relativity, it was proven that the speed of light in an empty space has a constant value and it is not dependent on the motion of the source of light.

Special relativity proves that one person’s interval of the space is another person’s interval of both the time and space and also that one person’s interval of time is another person’s interval of space and time both. This means that space and time are interchangeable in nature and is basically fundamentally the same thing.

##### HOW DID SPACE TIME COME AROUND?

Albert Einstein’s maths professor, Hermann Minkowski, was the one to coin the term ‘Space-time’ for describing the ability to interchange between the four dimensions. He described how the four-dimensional space-time can look different to the two observers present in the three-dimensional space. He said that owing to perspective, the length and width of the object can look different to the two observers despite the fact that the object is one and same in all the three dimensions.

Minkowski’s theory gave rise to the space-time interval that brings together distance and time. Even though the measurements of time and distance between the events are different from the measurements that are made in different reference frames, the spacetime interval is not dependent on the inertial frame of reference in the records. Minkowski’s interpretation helped Einstein to develop his general theory of relativity where he stated that in the presence of mass or energy, the spacetime becomes curved.

The physicists don’t believe in the concept of time as passing or flowing away since time is not a sequence of events that can occur, but time is constant- the past and future are laid out to serve as a part of space-time.

##### THE CURVED SPACETIME

The theory of general relativity denies the existence of action-at-a-distance. The motion of the satellite follows a straight line in its inertial frame. Owing to the curvature of the space-time, the particle’s local frame varies from each and every point.