24 hours

24 hours is a unit of time that is commonly used in the Gregorian calendar, the most widely used calendar system today. It is equivalent to 1,440 minutes or 86,400 seconds. The concept of a 24-hour day is rooted in ancient civilizations, including the Egyptians and Sumerians, who divided the day into parts related to their astronomical observations.

History

The division of the day into 24 hours is believed to have originated with the ancient Egyptians, who based their concept of time on the movements of the sun. They divided the day into 10 hours of daylight, 12 hours of night, and 2 hours of twilight. The Greeks, Romans, and other ancient civilizations later adopted this system.

Modern usage

In modern times, the 24-hour day is a standard unit of time used worldwide. It is used in various contexts, including work schedules, transportation timetables, and the programming of electronic devices. The 24-hour clock, also known as military time in the United States and Canada, is a timekeeping convention where the day runs from midnight to midnight and is divided into 24 hours. This is indicated by the hours passed since midnight, from 0 to 23.

In science

In science, the 24-hour day is used in various fields. In biology, the term "circadian" comes from the Latin circa diem, meaning "around a day". Many biological processes follow a circadian rhythm, which is roughly a 24-hour cycle. In astronomy, a solar day is the time it takes for the Earth to rotate about its axis so that the Sun appears in the same position in the sky. This is approximately 24 hours, but varies slightly throughout the year.

See also

• Hour
• Day
• Circadian rhythm
• Timekeeping