________ refers to the difference between the apparent time and the mean time.

• A. time correction
• B. equation of time
• C. apparent time
• D. mean time

Answer: (B)

The equation of time is the difference between apparent solar time (what a sundial shows, based on the Sun’s actual position) and mean solar time (the uniform clock time politicians aim to keep). The Sun does not move at a perfectly steady pace because Earth’s orbit is elliptical and its axis is tilted, so the Sun’s apparent daily motion speeds up and slows down over the year. A mean Sun is a fictitious, steadily moving reference that makes clock time constant. The equation of time captures how far apart these two times are on any given day and indicates how many minutes you must add to or subtract from one to convert to the other. Time correction is too general, and apparent time or mean time are the times themselves, not the difference between them.