Space Time Continuum

A general misunderstanding of common people is that we live in a world that has significantly only three dimensions- length, breadth and height. For a longer time the physicists thought that the universe is in three dimension (3D). It was Einstein who proved that our universe has one more dimension- time. The fourth cannot be represented as an axis on a paper (for better understanding only, in many areas time is represented as an axis). He suggested that our universe is a space time continuum. The dimensions originated for the purpose of defining the state of an object at any instant of time completely.

To understand it in a better way, lets try out a simple exercise. Let us assume that time is not the fourth dimension. Now with three dimensions we will try to define the state of an object at a certain difference of time. Consider a person A who is at point P(x1,y1,z1) at a time say t1. Say at this instant your friend makes a phone call. Now the person moves from point P and reaches point Q(x2,y2,z2) at time say t2. Now if your friend asks you "Where is A ?", you answer him Point Q. Alternatively if he asks "Where was A when I made a phone call ?". The answer will be point P. This shows that if we do not use time as the fourth dimension, the sense of 'when' i.e. the time of occurrence is lost and we would be unable to define the state of an object completely.