What is Time?

It is a tool to measure existence.

  

Time is the apparent irreversible progression of existence and events from the past to the present to the future. It is a component quantity of various measurements used to sequence events, compare the duration of events or the intervals between them, and quantify rates of change of quantities in material reality or consciousness. Along with the three spatial dimensions, time is frequently referred to as a fourth dimension.

Time has long been a topic of discussion in religion, philosophy, and science, but scholars have struggled to define it in a way that is universally applicable and avoids circularity. Nonetheless, various fields such as business, industry, sports, the sciences, and the performing arts all use some form of time in their measurement systems.

 

Time is operationally defined in physics as "what a clock reads."

With respect to events in space-time, general relativity addresses the physical nature of time. The collision of two particles, the explosion of a supernova, or the arrival of a rocket ship are all examples of events. Each event can be given four numbers that represent its time and location (coordinates).

The numerical values, on the other hand, differ depending on the observer. The question of what time it is now only has meaning in general relativity in relation to a single observer. As Michelson and Morley first publicly demonstrated, distance and time are inextricably linked, and the time required for light to travel a specific distance is the same for all observers. For extremely small intervals where quantum mechanics holds, general relativity does not address the nature of time. There is currently no widely accepted quantum general relativity theory.