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Glite Dictionary
mean solar day

mean solar day

6.3
Average time for Earth to turn once so the Sun appears in the same place, about 24 hours
  • noun
  • /miːn ˈsoʊlər deɪ/
  • Specialized
translation icon : día solar medio
  • Scientists measure time using a mean solar day, which amounts to approximately 24 hours.

Examples

  • A mean solar day is defined as the average duration it takes the Earth to fully rotate on its axis in relation to the Sun.

  • (We can ignore for the purposes of the present discussion that this is strictly speaking the mean solar day, since the eccentricity of Earth's orbit yields solar days of slightly differing lengths during the course of a year.)

    Academic text (2007)

  • The concept of a mean solar day helps synchronize clocks for everyday use around the world.

Synonyms

day
vsmean solar day
∞ 1.0

A period of 24 hours or the time a planet takes to turn once

is the precise averaged length defined for Earth's rotation relative to the Sun
twenty-four hours
vsmean solar day
64 1.0

A period equal to one full day and night

is the averaged standard of that cycle rather than the single actual rotation
solar day
vsmean solar day
  • Specialized
2 3.8

The time from one noon to the next, about 24 hours

is the averaged length over time rather than a single noon-to-noon measure

Surface Forms

mean solar day singular
mean solar days plural

Morphology

mean + solar + day

The phrase composes straightforwardly: 'mean' = average, 'solar' = relating to the sun, and 'day' = a day, so together they denote the average sun-based day length. Although used in astronomy, this is a transparent, compositional nominal phrase (and has clear equivalents in other languages), so a B1 learner who knows the parts can infer the meaning.

Etymology

Mean solar day explains a simple picture: solar means the Sun, day means the time from the Sun in one spot in the sky until it returns there, and mean means the 'average' of those times. So, because that Sun-time changes a little over the year, people use the 'mean' day — about '24 hours' — as the standard day.