Question

Is time a straight line?

Answer 1

Time is the progression of events and existence in the forward direction. It is also considered the fourth dimension according to Einstein’s general relativity. It is also used to describe other units and it is debatable whether it is relative in nature or just an illusion of our senses.

Complete answer:
Time is often referred to as the fourth dimension. It is the irreversible progression of events and existence from the past to the present on to the future. Time is also the seven fundamental units accepted in the International system of units or the SI system of units and its unit in SI is seconds (s).
The physical nature of time is described by the general relativity wherein every event is assigned four coordinates to describe its position and time but the values may be different depending on the observer.
Time is also used to describe other physical quantities like rate, power, velocity, acceleration etc.
Just like all the other dimensions, time is also a single line but not merely a single line. It is the entire existence stretched into motion.
Therefore, the time is perceived as a straight line as the existence of everything stretched into motion.

Note:
The SI system is the most common system of units used worldwide. General relativity is the geometric theory of gravitation described by Einstein’s equations. Time is relative in the sense that it slows down when objects move fast and vice versa. Time only moves in the forward direction.