Updated: Jan 26
Time dilation is a difference in the elapsed time as measured by two clocks due to a relative velocity between them or to a difference in gravitational potential between their locations. Albert Einstein originally predicted this effect in his 1905 “theory of special relativity”. Time dilation, as defined in the theory of special relativity, the “slowing down” of a clock as determined by an observer who is in relative motion with respect to that clock.
In special relativity, an observer in nonaccelerating motion has a well-defined means of determining which events occur simultaneously with a given event. A second observer, who is in relative motion with respect to the former, however, will disagree with the first observer regarding which events are simultaneous with that given event. The biggest question here is to find the correct observer among these two. Can you guess who is right???
Well, neither observer is wrong in this determination; rather, their disagreement merely reflects the fact that simultaneity is an observer-dependent notion in special relativity. A notion of simultaneity is required in order to make a comparison of the rates of clocks carried by the two observers. If the first observer’s notion of simultaneity is used, it is found that the second observer’s clock runs slower and vice-versa by the same factor. Thus, each inertial observer determines that all clocks in motion relative to that observer run slower than that observer’s own clock.
Physicists have verified this theory with experiments at a particle accelerator in Germany which confirm that time moves slower for a moving clock than for a stationary one. The work is the most stringent test yet of this ‘time-dilation’ effect, which Einstein predicted.
One of the consequences of this effect is that a person travelling in a high-speed rocket would age more slowly than people back on Earth. In physics, this effect is known as “the twin paradox”.
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