Definition

1. Noun:
   • Mean solar time is a measurement of time based on the average (mean) motion of the Sun along the celestial equator. It is a uniform time scale that averages out the variations in apparent solar time caused by the Earth's elliptical orbit and axial tilt.

Usage

• Mean solar time is used as a standard time reference in astronomy and was the basis for civil timekeeping before the adoption of Coordinated Universal Time (UTC).
• It is often contrasted with apparent solar time, which is based on the actual observed position of the Sun.

Examples

• Noun:
  • The observatory's clock was set to mean solar time for precise astronomical calculations.
  • Before time zones, each town kept its own local mean solar time.

Advanced Usage

• "Local Mean Time (LMT)": The mean solar time at a specific geographical longitude.
  • The ship's navigator calculated their position using Local Mean Time.

Variants and Related Words

• Apparent solar time (n): Time based on the actual observed position of the Sun, which varies slightly from mean solar time.
• Universal Time (UT1) (n): A modern form of mean solar time measured at the prime meridian (0° longitude), used in astronomy.

Synonyms

• Civil time (in its historical context).
• Mean time.

Related Phrases

• Equation of time: The difference between apparent solar time and mean solar time.
  • The equation of time shows the discrepancy between your sundial and your watch.

Noun

1. (astronomy) time based on the motion of the mean sun (an imaginary sun moving uniformly along the celestial equator)