Mean solar time

Definition

Mean solar time is a measure of the average passage of time based on the position of the mean sun, an imaginary point that moves uniformly along the celestial equator. This concept helps standardize timekeeping by averaging out the variations caused by Earth's elliptical orbit and axial tilt.

5 Must Know Facts For Your Next Test

1. Mean solar time differs from apparent solar time, which is based on the actual observed position of the sun in the sky.
2. The mean sun is an imaginary construct that moves at a constant rate to simplify timekeeping.
3. Greenwich Mean Time (GMT) is an example of mean solar time, and it serves as a reference for other time zones worldwide.
4. Mean solar day is exactly 24 hours long, while apparent solar days can vary slightly due to Earth's orbital eccentricity and axial tilt.
5. The equation of time quantifies the difference between mean solar time and apparent solar time at any given moment.

Related terms

Apparent Solar Time:

Time measured based on the actual observed position of the sun in the sky.

Greenwich Mean Time (GMT): A standard mean solar time at Greenwich, England, used as a global reference point for coordinating universal time.

Equation of Time: A mathematical expression that quantifies the difference between apparent and mean solar times.