According to the theory of relativity, time is indeed relative and not absolute. This is a fundamental concept in both special relativity and general relativity. The idea of time being relative means that the passage of time can vary depending on the relative motion between observers and the strength of gravitational fields they experience.
Special relativity, formulated by Albert Einstein in 1905, introduced the concept of spacetime, where time and space are interconnected. One of the key principles of special relativity is that the speed of light in a vacuum is constant and the same for all observers, regardless of their relative motion. This constant speed of light is denoted by "c" and serves as a fundamental constant in the theory.
The constancy of the speed of light leads to some profound consequences. One of them is time dilation, which means that time can appear to flow differently for observers moving at different velocities relative to each other. When objects move at high speeds relative to each other, time dilation occurs, and the moving object's clock appears to run slower compared to a stationary observer's clock. This effect has been experimentally confirmed numerous times.
General relativity, developed by Einstein in 1915, extends the concept of relative time to include the effects of gravity. In the presence of a gravitational field, clocks in stronger gravitational fields run slower compared to clocks in weaker fields. This gravitational time dilation has also been observed and confirmed through experiments, such as with atomic clocks on satellites.
So, in the framework of relativity, time is not considered absolute but rather depends on the observer's motion and the gravitational field they experience. The constancy of the speed of light plays a crucial role in establishing the relative nature of time. It's important to note that this does not mean time is arbitrary or ill-defined, but rather that its measurement is influenced by the conditions of the observer.
Regarding your mention of temperature and absolute zero, it is a different concept altogether. Temperature and the absolute zero refer to the behavior of particles and their thermal energy. Absolute zero is the lowest temperature possible, at which particles have minimal thermal energy and theoretically come to a complete stop. Temperature and time are distinct quantities, and the relativity of time does not imply the existence of an absolute measure for other variables like temperature.