sidereal day
noun
plural sidereal days
: the interval between two successive transits of a point on the celestial sphere (such as the vernal equinox) over the upper meridian of a place : 23 hours, 56 minutes, 4.1 seconds of mean time
In recent experiments, the frequency … was found to vary by not more than 100 μHz over a sidereal day as the rotation of the earth changed the orientation of the ions (fixed by the laboratory magnetic field) with respect to the external universe.—
David Golden
David GoldenExamples of sidereal day in a Sentence
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That extra 4 minutes (really 3 m 56 s) is the difference between a solar and sidereal day.
—Phil Plait, Discover Magazine, 1 Jan. 2012
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Phil Plait, Discover Magazine, 1 Jan. 2012
Cite this Entry
“Sidereal day.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/sidereal%20day. Accessed 4 May. 2025.
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