We explain what time is approached from Physics and its formulas. Time in classical mechanics and relativistic mechanics.

## What is time in physics?

In physics, time is called **magnitude that** **serves to measure the duration or separation of one or more events**. This allows them to be ordered in a sequence (past, present, future) and determine whether or not they occur simultaneously.

time **It is represented with the variable t** its unit of measurement in the International System is the second (

*yes*), in a sexagesimal framework (60 units constitute a larger unit) and the device with which it is measured is the clock.

Time can be thought of as the duration of things that are subject to change, and** It is one of the most important physical quantities**. Within physical considerations, it is considered a variable that, combined with others, allows determining the position, movement, speed and many other magnitudes of an object or system.

## Formulas to calculate time

Time is involved in numerous physical calculations and, therefore, there are many possible formulas to calculate it, depending on the other variables we have at hand:

**Speed**The speed is calculated from the formula(Speed equals distance over time). It is measured in units of distance per units of time:*V = d/t**Km/h, m/s*etc. If we solve for time in this formula, we get:**t = d/v****Acceleration**The acceleration (*to*) is the change in time between two speeds and is calculated with the formula:where*a = Δv/Δt**Δv*is*v*and_{initial}–v_{end}*Δt*is*t*. If we take the_{initial}–t_{end}*t*as zero, then we have to:_{initial}*t = (V*_{F}–V_{Yo}) /to

## Time in classical mechanics

In classical physics, time** is considered an absolute value** that is, a magnitude that occurs in the same way for all the phenomena studied. This means that two different observers will always agree regarding the order of events (past, future and simultaneous present).

## Time in relativistic mechanics

In relativistic mechanics, time is a more complex concept, since **It is linked to the position of the observer of the event and its state in motion** that is, in relativistic mechanics time is relative. Two observers who differ in their position and movement will differ in their measurement of the time of an event, so the time will always depend on the observer's reference system.

The duration (*Δt*) of an event measured in a system at rest. The duration (*Δt'*) of that same event, measured from a reference system that moves with constant speed with respect to the one at rest, is given by *Δt' = Δt / √1-v ^{2}/c^{2}.*

This distinction **arose after the formulation of the Theory of Relativity** of Albert Einstein and his profound impact on the field of physics. According to her, there is no single time but it can vary under certain physical conditions.

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