What Is Time? A Simple Explanation - 0 views
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Time is familiar to everyone, yet hard to define and understand. Science, philosophy, religion, and the arts have different definitions of time, but the system of measuring it is relatively consistent. Clocks are based on seconds, minutes, and hours. While the basis for these units has changed throughout history, they trace their roots back to ancient Sumeria. The modern international unit of time, the second, is defined by the electronic transition of the cesium atom. But what, exactly, is time?
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Physics equations work equally well whether time is moving forward into the future (positive time) or backward into the past (negative time). However, time in the natural world has one direction, called the arrow of time. The question of why time is irreversible is one of the biggest unresolved questions in science.
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In classical mechanics, time is the same everywhere. Synchronized clocks remain in agreement. Yet, we know from Einstein's special and general relativity that time is relative. It depends on the frame of reference of an observer. This can result in time dilation, where the time between events becomes longer (dilated) the closer one travels to the speed of light. Moving clocks run more slowly than statio