# Space & Time: The Last Frontier?

A brief study of 'Time and Space', and the developments in the field of 'Time Travel'.

Anirban Ray Choudhury

Last Updated: Dec 10, 2018

**Time**―an eternal paradox, and in more ways than one can imagine. Forget nostalgia, forget futuristic fiction with its flying cars and intergalactic missiles and what have you―the paradox has now evolved to real problems of physical science.

**space-time continuum**. Or the famous, famous grandfather's paradox. Or the most important question since H G Wells―would it ever be possible to travel back and forth through time?

**space**and

**time**.

The Newtonian Universe

Sir Isaac Newton, revered by many as the father of modern theoretical physics, propounded that time is a constant factor in physics, regardless of the reference frame. In his theories and equations, time was variable which could move only in one direction and at a constant rate, independent of whether the reference frame was static or in motion.

The Einstein Approach

Albert Einstein, a Nobel Laureate physicist of German origin, first put forth a four-dimensional concept of the universe. In 1905, Einstein produced his

**Special Theory of Relativity**, which sought to explain the behavior of light waves in different reference frames.The Current Status

After Einstein and the Lorentz Transformation (an equation developed by mathematician Hendrik Lorentz), the concept of time as an immutable variable slowly faded away, giving rise instead to an entirely new concept, that of the space-time continuum.

**space-time continuum**; the shape being determined by the matter contained in the continuum. A little too complicated to understand?

On Traveling Through Time

So, we have understood gravity, and got a fair idea of what the General theory of relativity is all about. But where does

**time travel**come into the picture? The answer lies in Time Dilation.Wormholes

So, now we know that we can move forward in time, if only theoretically as yet. But that is not the time travel that we are looking for, right? How about a round trip, the one where a person goes to place and 'comes back'? Well, that is not an impossibility, but there are limitations. To understand, let us first study black holes.

Are We Ready Yet?!

There is one limitation to time travel through worm holes. Such a

**'time machine'**could carry you to the past only so far back as the date on which the wormhole was created (or where multiple wormholes are used, to the date when the first wormhole was created). So, it would perhaps be right to bid adieu to the good old days―they are not coming back.