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About these units
Second (s)
The second is the fundamental SI unit of time and the basis for nearly every modern timing system, from everyday clocks to astronomical calculations and quantum physics. Historically, the second was defined as 1/86,400 of a mean solar day—reflecting Earth's rotation. But because Earth's rotation is not perfectly constant, this definition proved insufficient for scientific precision. Today, the second is defined by the vibration frequency of the cesium-133 atom, specifically 9,192,631,770 oscillations of its hyperfine transition. This atomic definition gives the second extraordinary accuracy and stability, enabling technologies like GPS, satellite communications, deep-space navigation, and particle physics experiments. The second sits at the intersection of human history and cutting-edge physics: once tied to the apparent motion of the Sun, it is now anchored to a universal atomic constant, making it one of the most precisely defined units in science.
Year (y)
A year is the time it takes Earth to complete one orbit around the Sun, approximately 365.2422 days. This value is not exact, which is why leap years exist. The year is the foundation of calendars, agriculture, climate cycles, financial planning, long-term engineering designs, and historical chronology. Its importance spans science, culture, religion, and economics. The modern Gregorian calendar year is an elegant compromise that aligns civil life with astronomical reality, minimizing drift between the calendar and the seasons. Despite its complexity, it remains the global standard for structuring long-term human activity.