There have been many definitions of the hour throughout history based on culture or region, such as the hour being divided into 1/12 of a period daylight or darkness. History/origin: The term "hour" is derived from the Anglo-Norman "houre," which was in use around the 13 th century. In Coordinated Universal Time, a negative or positive leap second may be incorporated to keep the hour within 0.9 seconds of universal time, making an hour either 3,599 or 3,601 seconds in some cases. Hourĭefinition: An hour (symbol: h) is a unit of time conventionally defined as 1/24 of a day and 3,600 seconds. History/origin: The term "minute" is derived from the Latin "pars minuta prima" which means the "first small part." The minute was originally defined as 1/60 of an hour (60 seconds), based on the average period of Earth's rotation relative to the sun, known as a mean solar day.Ĭurrent use: The minute, as a multiple of the second, is used for all manner of measurements of duration, from timing races, measuring cooking or baking times, number of heart beats per minute, to any number of other applications. Under Coordinated Universal Time, a minute can have a leap second, making the minute equal to 61 rather than 60 seconds. 2011.Definition: A minute (symbol: min) is a unit of time based on the second, the base unit of the International System of Units (SI). Wikipedia, The Free Encyclopedia, last visited 26 Jun. " Conversion of units" Wikipedia, The Free Encyclopedia. Lide, David R., Daniel (Editor-in-Chief).ĬRC Handbook of Chemistry and Physics, 89th Edition, New York, NY: CRC Press, p. 1-28, 2008. The NIST Guide for the Use of the International System of Units - Appendix B, subsectionsī.8 Factors for Units Listed Alphabetically andī.9 Factors for units listed by kind of quantity or field of science. The National Institute of Standards and Technology (NIST). How Many? A Dictionary of Units of Measurement. Traditionally, observatories had clocks set to this sidereal cycle, and astronomers still use sidereal time in making telescope settings. The sidereal hour equals 59 minutes 50.17 seconds the sidereal minute equals 59.8362 seconds the sidereal second equals 0.997 270 second. Like the regular day it is divided into 24 sidereal hours, each sidereal hour being divided into 60 sidereal minutes and each sidereal minute into 60 sidereal seconds. The sidereal day equals 23 hours 56 minutes 4.090 54 seconds, or 86 164.090 54 seconds. Thus the sidereal day, the average interval between two successive risings of the same star, is shorter than the mean solar day (see day) by 1/366.242. We only count 365.242 because one rotation is cancelled out for us by our tour around the sun. If we could view the earth from outside the Solar System, we would see that it actually completes 366.242 rotations during one year (one revolution around the sun). Sidereal day: a unit of time used in astronomy, equal to the period of time in which the earth makes one rotation relative to the stars. To convert directly from minutes to hours you multiply by 0.01 6. Simplified, this is the same as multiplying by 60/3600 which is 0.016666667. To convert from minutes to hours multiply the number of minutes by 60 and then divide by 3600. Or you can find the simplified factor by dividing the conversion factor for A by the conversion factor for B. To convert among any units in the left column, say from A to B, you can multiply by the factor for A to convert A into seconds then divide by the factor for B to convert out of seconds.
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