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solar time

solar time in Science
solar time  
Time based on the rotation of the Earth with respect to the Sun. Solar time units are slightly longer than sidereal units due to the continuous movement of the Earth along its orbital path. For example, by the time the Earth has completed one full rotation on its axis with respect to the fixed stars, it has also moved a short distance in its orbit and is oriented slightly differently to the Sun, so that it must turn slightly more on its axis to complete a full rotation with respect to the Sun. ◇ The time it takes the Earth to rotate fully with respect to the Sun is called a solar day. The length of a solar day varies throughout the year due to variations in the Earth's orbital speed and other factors. ◇ The average value of all solar days in the solar year is called a mean solar day; it is 24 hours long and by convention is measured from midnight to midnight. ◇ A solar year is the period of time required for the Earth to make a complete orbit with respect to the Sun as measured from one vernal equinox to the next; it is equal to 365 days, 5 hours, 48 minutes, 45.51 seconds. A solar year is also called an astronomical year and a tropical year. ◇ A solar month is one twelfth of a solar year, totaling 30 days, 10 hours, 29 minutes, 3.8 seconds. Compare sidereal time.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Historical Examples
  • solar time is the angular distance of the sun past the meridian.

    A Text-Book of Astronomy George C. Comstock
  • The solar time by which our nautical standard is fixed, is that of the meridian of Greenwich.

    Time and Time-Tellers James W. Benson
  • By 1300, solar time, the camp was considered to be on a standard operating basis.

    The Unprotected Species Melvin Sturgis
  • Sidereal time commences when the vernal equinox is on the meridian, just as solar time commences when the sun is on the meridian.

    Letters on Astronomy Denison Olmsted
  • solar time is reckoned by the apparent revolution of the sun from the meridian round to the meridian again.

    Letters on Astronomy Denison Olmsted
  • And with that thought there flashes on his mind an inspiring conception—the idea that solar time is long, indefinitely long.

  • The hour angle of the center of the sun is the measure of apparent or solar time.

    Lectures in Navigation Ernest Gallaudet Draper
  • Apparent or solar time is, as stated before, nothing more than sun time or time by the sun.

    Lectures in Navigation Ernest Gallaudet Draper
  • Hence we distinguish clock time from sun time by calling clock time, mean (or average) time and sun time, apparent or solar time.

    Lectures in Navigation Ernest Gallaudet Draper
  • For the last two days we have been discussing Time - sun time or solar time and star time or sidereal time.

    Lectures in Navigation Ernest Gallaudet Draper

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