The Fourth Dimension

Although now we know to measure time accurately, have we come any nearer to answering the basic question ‘What is time?’

I’ve been thinking about this for quite some time now. Yesterday I saw my sister reading a book called ‘The Time Traveller’s Wife’ (a science fiction, as the name suggests and now even a movie, which I haven’t watched), which provided me the momentum to write this article.
Ever since my childhood, I’d always been fascinated by the idea of time travelling. I'd wonder what if someone enters the past, changes it slightly so as to change the present! The present would simply not exist.

For instance, photons and electrons show both wave and particle nature but never exhibit both the characteristics at the same time. Are we – all human beings like these photons and electrons, who can have more than one existence -in many different worlds, times and spaces? Is everything in this universe preordained? Or is there infinite number of universes? Uh-oh! These intricate thoughts make me completely lost.

In Classical Mechanics, time is considered as a universal constant, whereas according to the theory of relativity, time is not independent of the three dimensional space. The rate at which time passes depends on an object’s velocity relative to the speed of light and also on the strength of intense gravitational fields, which can slow down the passage of time. Therefore, Einstein had put forth the theory of spacetime in which he brought space and time together in a four dimensional arrangement.

However, no one knows how many dimensions the universe is made up of, because the effect of these dimensions can only be felt during very energetic processes such as inside a black hole! (A black hole is a region of space from where nothing can pass through not even light. This is because there the escape velocity increases and becomes more than the velocity of light).

It is said that time becomes a dimension, the fourth dimension inside a black hole. Some physicists say that time can be altered inside black hole just like space in the three dimensional world we live in and few interpretations show the possibility of time travel – at least in theory. They also say that one way of looking at the quantum world suggest that if we travel back in time and change history we launch ourselves into a new future – a parallel universe!