Time dilation is a phenomenon predicted by Albert Einstein's theory of special relativity, which states that the flow of time can appear to vary for observers in relative motion. It occurs when an object or observer moves at a significant fraction of the speed of light relative to another object or observer.
According to special relativity, time dilation arises due to the constancy of the speed of light in all inertial reference frames. The theory postulates that time is not absolute but is relative to the observer's frame of reference and is influenced by the relative motion between observers.
The fundamental concept to understand time dilation is that the speed of light is always constant in all frames of reference. This means that the measured speed of light will be the same regardless of the motion of the source or the observer. However, since the speed of light is constant, the observed frequency and wavelength of light must change as an observer moves relative to the source of light.
When an observer is in relative motion with respect to another object, the observer will perceive time to be running slower for the moving object compared to their own time. This effect is known as time dilation. The faster an object moves relative to an observer, the more pronounced the time dilation effect becomes.
The mathematical expression that quantifies time dilation is given by the Lorentz factor:
γ = 1 / √(1 - v²/c²)
Where γ is the Lorentz factor, v is the relative velocity between the two observers, and c is the speed of light.
The Lorentz factor tells us how much an observer's time slows down compared to a stationary observer. If the relative velocity (v) is small compared to the speed of light (c), then the Lorentz factor is approximately equal to 1, and time dilation is negligible. However, as v approaches c, the Lorentz factor increases, and time dilation becomes more significant.
To summarize, special relativity predicts that time dilation occurs due to the relative motion between observers. As an object's velocity approaches the speed of light, time dilation becomes more pronounced, leading to a slowing down of time from the perspective of a stationary observer. This effect has been experimentally verified and has important implications for our understanding of space, time, and the nature of the universe.