mean solar day

Thân thiện

A sundial's shadow completes one full circle over the course of a mean solar day.

Definition

1. Noun:
   • A standard unit of time measurement: A "mean solar day" is the average length of a solar day, calculated over a year. It represents the time it takes for the Earth to complete one full rotation on its axis relative to the Sun, averaged to account for small variations throughout the year. It is the basis for the 24-hour day.

Usage

• The term "mean solar day" is used in precise scientific, astronomical, and technical contexts to distinguish the standardized 24-hour period from the actual, slightly variable solar day.
• In everyday language, people typically use the simpler term "day."

Examples

• Noun:
  • The mean solar day is exactly 24 hours long, unlike the actual solar day which varies.
  • Scientists use the mean solar day as a constant unit for timekeeping.
  • The difference between an apparent solar day and a mean solar day is explained by the equation of time.

Advanced Usage

• "Mean solar time": Time based on the mean solar day, as used by civil clocks.
  • Greenwich Mean Time (GMT) was based on mean solar time at the Royal Observatory.

Variants and Related Words

• Solar day (or apparent solar day): The actual time between two successive noons, which varies in length.
• Day: The common term for a 24-hour period, often synonymous with "mean solar day" in general use.
• Sidereal day: The time it takes for the Earth to rotate once relative to distant stars, which is about 4 minutes shorter than a mean solar day.

Synonyms

• Civil day: Another term for the 24-hour day based on mean solar time.
• Twenty-four-hour period: A descriptive synonym.

Học thuật

Noun

1. time for Earth to make a complete rotation on its axis
   • two days later they left
   • they put on two performances every day
   • there are 30,000 passengers per day

Từ đồng nghĩa

• day
• twenty-four hours
• twenty-four hour period
• 24-hour interval
• solar day