mean sun: meaning, definition, pronunciation and examples
C2Technical/Scientific
Quick answer
What does “mean sun” mean?
A theoretical, uniform-moving sun used as a reference in astronomy and timekeeping, averaging the apparent sun's irregular motion along the ecliptic.
Audio
Pronunciation
Definition
Meaning and Definition
A theoretical, uniform-moving sun used as a reference in astronomy and timekeeping, averaging the apparent sun's irregular motion along the ecliptic.
A mathematical construct representing the average position of the Sun if its apparent annual motion were uniform, essential for defining mean solar time (clock time) as opposed to apparent solar time (sundial time).
Dialectal Variation
British vs American Usage
Differences
No significant lexical differences. The term is standardised in the global scientific community.
Connotations
Purely technical, with no regional connotative differences.
Frequency
Extremely low frequency in general discourse, used identically in specialised UK and US technical contexts.
Grammar
How to Use “mean sun” in a Sentence
The mean sun is used to calculate...The difference between the apparent sun and the mean sun...Mean time is based on the fictitious mean sun.Vocabulary
Collocations
Examples
Examples of “mean sun” in a Sentence
adjective
British English
- The mean-sun position is tabulated in the almanac.
- Mean-sun calculations are fundamental.
American English
- The mean-sun data is essential for the algorithm.
- Mean-sun reference frames are standard.
Usage
Meaning in Context
Business
Not used.
Academic
Used in advanced astronomy, physics, and geodesy papers and textbooks.
Everyday
Virtually never used.
Technical
Core term in celestial mechanics, satellite navigation (GNSS), and time standard definitions (e.g., UTC).
Vocabulary
Synonyms of “mean sun”
Neutral
Weak
Vocabulary
Antonyms of “mean sun”
Watch out
Common Mistakes When Using “mean sun”
- Using 'mean sun' in everyday contexts.
- Confusing it with the actual Sun.
- Misinterpreting 'mean' as implying malice.
FAQ
Frequently Asked Questions
No, it is a theoretical construct, a mathematical point moving uniformly along the celestial equator.
Because the real Sun's apparent motion across the sky varies in speed throughout the year due to Earth's elliptical orbit and axial tilt. The mean sun provides a constant rate for reliable clocks.
Mean solar time is clock time, based on the mean sun. Apparent solar time is sundial time, based on the real Sun's position. They can differ by up to about 16 minutes.
Yes, it signifies an average or intermediate value, not malice.
A theoretical, uniform-moving sun used as a reference in astronomy and timekeeping, averaging the apparent sun's irregular motion along the ecliptic.
Mean sun is usually technical/scientific in register.
Mean sun: in British English it is pronounced /ˌmiːn ˈsʌn/, and in American English it is pronounced /ˌmin ˈsʌn/. Tap the audio buttons above to hear it.
Learning
Memory Aids
Mnemonic
Think of a clock's steady tick (mean sun) vs. a sundial's shifting shadow (apparent sun). 'Mean' here means 'average,' not 'nasty'.
Conceptual Metaphor
TIME IS A REGULAR PATH (The irregular path of the real sun is conceptually smoothed into a perfect, average path for measurement).
Practice
Quiz
What is the primary purpose of the 'mean sun'?