I would like to start with one, two and three dimensions of space first and then come to time as the 4th dimension. But I am not ignoring the possibilities of any further dimensions for this universe as a whole.
Suppose, there is a very big circular track in a city of the circumference, say 15 kms and a man is asked to run onto this track continuously. The man is not aware of the fact that the track is circular and he keeps running straight until he completes 15 kms. After completing the entire cycle, he observes that he has reached to the same position from where he started and he had no clue until he was shown the entire track from helicopter over that area. So, he always thought that he is moving in a straight line i.e. 1-D space but there was a twist of 2-D space that brought him back to the same starting position. If he would have moved with a bike at 100 kmph, he could have noticed the little effect that he is moving slightly left or right. The same thing happens if an object moves with speed closer the to speed of light.i.e. time dilates and the person remains younger.
So, the question is answered now as time is an invisible dimension to us until we move very fast and comparable to the speed of light. Also, time has capability to make anybody walk into past or future but we lack technology to bring that transformation. Again, moving into future makes sense but traveling back into the past is still dubious as the theory of relativity gives imaginary solutions for a particle moving beyond the speed of light and hence it is considered to be an impossible event.
Authot: Prabhat Kumar
