We all are quite familiar with the measurement of time. But, what is time? Why does it flow? And, why does it go forward, not backward?
According to Special Relativity, time is a dimension, but, not like the dimensions of space.
For example, we travel in spatial dimensions everyday. When you are in motion, you are traveling in space. Traveling in spatial dimensions means covering some ‘distance’. It is very simple. But, it is not that simple to travel in time.
For example, if you wanna go backwards in time, you can’t just turn back and start moving!
So, that’s why time is a different type of dimension.
FLOW OF TIME
The other question is why time flows? Moreover, why does it flow in forward direction only?
This question still doesn’t have a widely accepted answer in the scientific community, however, an excellent answer for the flow of time was given by Professor Richard A. Muller (Physicist at the University of California, Berkely) in 2016, in his research paper titled ‘Now, and the Flow of Time’. The paper was co-written by Shaun Maguire (Physicist).
Muller proposed that the flow of time can be easily understood by assuming the expansion of the the universe in all four dimensions of space-time rather than in only three dimensions of space. This means that the universe is also expanding in time.
What does it mean? The paper proposed that space and time are so strongly linked in the theory of relativity that when new space is created, new time is also created.
We know that the universe is expanding. It means that the three-dimensional space is expanding. The space between galaxies is expanding. This means that new space is being created every moment. So, with the creation of new space, new time must be created. This is why time flows. “New time is created every moment”. Now, at this moment also, ‘a’ new time is created!
So, if the universe weren’t expanding, time would not be passing or flowing. Every single object would simply stop as we see in science fiction movies that there is a person with a clock. He presses a button on the clock and everything stops because of the stopping of time. Same would be the case if the universe were static.
We can take another example to prove Muller’s theory . When I came to know about this theory, I was quite fascinated by Muller’s Idea. After thinking more and more about it, I though about the following argument:
If the universe were contracting, it would finally reach point of zero size, that is, a singularity. We also know that the universe began at a singularity. Also, according to Muller’s theory, time would reverse if the universe were contracting and the universe would finally reach the point where it began (at time, t = 0 ), that is, a singularity! Both contraction of space and reversal of time give the same result, that is, the universe becoming a singularity, so both contraction of space and reversal of time should be interlinked. This is also what Muller’s theory predicts.
So, we can say if the Big Bang theory and general relativity are correct, then Muller’s theory is also correct.