mean solar time: meaning, definition, pronunciation and examples
Very LowFormal, Technical
Quick answer
What does “mean solar time” mean?
Time based on the average length of a solar day, calculated from the Sun's apparent motion as if it moved at a constant rate, ignoring its actual observed position due to the Earth's elliptical orbit and axial tilt.
Audio
Pronunciation
Definition
Meaning and Definition
Time based on the average length of a solar day, calculated from the Sun's apparent motion as if it moved at a constant rate, ignoring its actual observed position due to the Earth's elliptical orbit and axial tilt.
A standardized timekeeping system, historically used as the basis for civil time before the adoption of Coordinated Universal Time (UTC), which smooths out the irregularities in apparent solar time.
Dialectal Variation
British vs American Usage
Differences
No significant difference in meaning or use. The term is equally technical in both dialects.
Connotations
Neutral and technical. In the UK, 'Greenwich Mean Time' (GMT) is a familiar term, which historically was a specific application of mean solar time at the Greenwich meridian.
Frequency
Equally low frequency in both dialects, confined to specialised contexts.
Grammar
How to Use “mean solar time” in a Sentence
[Mean solar time] + [verb: is/was/varies]The [noun: difference/equation] of [mean solar time][Preposition: According to/Using] mean solar timeVocabulary
Collocations
Examples
Examples of “mean solar time” in a Sentence
adjective
British English
- The mean solar day is the fundamental unit.
- He studied the mean solar time calculations.
American English
- The mean solar day is the fundamental unit.
- She referenced the mean solar time system.
Usage
Meaning in Context
Business
Virtually never used.
Academic
Used in astronomy, physics, geography, and history of science courses or papers explaining time measurement.
Everyday
Extremely rare; may appear in detailed explanations of time zones or sundials.
Technical
Core term in astronomy, geodesy, navigation, and precise timekeeping systems. Used to define the 'equation of time'.
Vocabulary
Synonyms of “mean solar time”
Strong
Neutral
Weak
Vocabulary
Antonyms of “mean solar time”
Watch out
Common Mistakes When Using “mean solar time”
- Confusing it with 'apparent solar time' (the actual Sun position).
- Using it in everyday contexts where 'standard time' or 'time zone' is meant.
- Misspelling as 'means solar time'.
FAQ
Frequently Asked Questions
Historically, yes. Modern civil time (like UTC) is now based on atomic clocks, but it is kept within 0.9 seconds of a specific form of mean solar time (UT1) by adding leap seconds.
It is a number, usually in minutes, that you add to or subtract from apparent solar time (sundial time) to get mean solar time. It shows how much the Sun is 'fast' or 'slow' compared to the clock.
Because the Sun's apparent motion varies in speed throughout the year due to Earth's elliptical orbit and axial tilt. This would make days (noon to noon) different lengths, which is impractical for precise schedules and clocks.
Yes, specifically. GMT was originally defined as the mean solar time at the Royal Observatory in Greenwich, London (longitude 0°). While the term GMT is now often used interchangeably with UTC, its original astronomical definition was mean solar time at Greenwich.
Time based on the average length of a solar day, calculated from the Sun's apparent motion as if it moved at a constant rate, ignoring its actual observed position due to the Earth's elliptical orbit and axial tilt.
Mean solar time is usually formal, technical in register.
Mean solar time: in British English it is pronounced /miːn ˈsəʊlə taɪm/, and in American English it is pronounced /min ˈsoʊlɚ taɪm/. Tap the audio buttons above to hear it.
Learning
Memory Aids
Mnemonic
Think of the MEAN (average) SOLAR (Sun) TIME. The Sun's daily schedule seems irregular, so we take its MEAN (average) behaviour to make our clocks run evenly.
Conceptual Metaphor
TIME IS A REGULAR, MEASURABLE PATH (contrasted with the Sun's 'wobbly' apparent path).
Practice
Quiz
What is the primary purpose of mean solar time?