Hour, a unit for measuring time, defined as either 1/24 of a day or 3600 seconds (60 minutes). Used alone, the word hour refers to clock time, a composite of mean solar time and atomic time. There are other types of hours, such as sidereal hours (9.83 seconds shorter than clock-time hours), but these are primarily of theoretical interest. Scientists, who are most concerned with precise time intervals, tend to use decimal fractions of the various types of days and multiples of seconds instead of hours. (Seconds and days are based on measurable physical phenomena; the hour is derived from seconds and days.)
You Might Also Like
So much of our cosmological history starts with the much-discussed big bang, but what led up to that cataclysmic moment? And did time even exist back then?
The big bang theory is well-known, but there are many misconceptions about it. Like what? Let's start with this one: There was no bang.