Time

The past, present and future depicted in space-time

Madhu Lamichhane
Mechanical Engineering Final Year

“Time is the fourth dimension, one of the seven fundamental physical quantities, or if you want broader definition, it is what goes on – along and to the eternity, binding and taking together everything that exists. You could even say, time is the irreversible sense of being and existence. However there have been many different ideas propounded.”

“Oh, I meant the time on your watch. But thanks!”

Time is an idea popular among philosophy and religion too, but it is science that explains and explores it best. The quest of possible explanation of what’s going on and how everything is moving forward without pausing a bit has always struck human’s mind as impregnable. The days and nights, and seasons were the first answers to where we stand in the course of time. But each fraction of every moment began to become worthwhile and thus started the conquest of ‘time’. In the first days of technological development, time used to be measured taking periodic motions and events as the standards. For example, the apparent motion of the sun, phases of the moon, swinging of the pendulum, beating of the heart, etc. The idea of keeping track of time then came and calendars, the mathematical tool for organising intervals of time and clocks, a physical mechanism that counts the passage of time were invented.
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An hourglass
With more studies in physics and mathematics, the unit of time was felt as a need in making scientific studies more robust and clear. ‘Second’ was introduced as the standard unit by a Persian scholar al-Biruni as (1/86400)th of a mean solar day. Later, it was adopted worldwide by scientists and quantitatively defined as the duration of 9192631770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom. Other units of time like minute and hour were also introduced based on the unit of second.

But since the concept of time doesn’t end in its measuring and keeping records, its scientific delineation is equally important. In the classical mechanics, time has the concept of ‘relative, apparent and common time’. Considering it as a fundamental structure of the universe, as put forward by Isaac Newton (thus comes the term Newtonian time), it is the dimension independent of events. But, this idea encountered problems in the behaviour of electricity and magnetism and thus in modern physics. Later, Albert Einstein put forward his theory of space-time. According to this theory, which results from his two theories of special relativity and general relativity, the concept of time depends upon the spatial reference frame of the observer. This means, in short, for two different bodies travelling with different speed, the relative time is different among each other.

Big bang is another popular theory that explains the expansion of the universe from a singularity, where time is believed to have started with the bang. Time has been continuously running since. Stephen Hawking, a British physicist and cosmologist, says that there is an arrow of time that is directed towards the future, leaving behind the past. Present is a point of just now, yet too hard in explaining its dimension. J.W. Dunne, another British laureate, describes time in two ways; one kind is just one direction in the four-dimensional landscape of space-time, and another kind is needed to explain the moment of ‘now’ which travels across the map in the map-time and which we experience.

To provide a single yet still ambiguous idea, time is the continuous chain that has carried all the past and the ephemeral present and that will craft a basis for all the future. It is a hypothesis that will go on to the eternity, philosophically speaking, and is too unreal to depict. Science has only tried to put a physical worth but its complete understanding lies far ahead of the present scientific revelations.
So, the time is about 15 billion years past the Big Bang.

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