Second

From AoPSWiki

The second is the SI unit for time. It used to be defined as the time in which light travels approximately 299792458 meters, or about 299792 kilometers. The current definition of a second is the time it takes for a cesium 133's radiation to oscillate for 9192631770 periods. This is assuming that the cesium atom is at 0 K. There are 60 seconds in a minute, 3600 seconds in an hour, and 86400 seconds in a day.

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