ephemerides
Definition
- Noun (plural form of ephemeris):
- Astronomical tables: "ephemerides" refers to tables or data sets that predict the positions of celestial bodies (such as planets, moons, asteroids, and comets) at specific times over a given period.
- Historical usage: In ancient and early modern contexts, "ephemerides" also referred to almanacs or calendars that recorded daily astronomical events, including the rising and setting of stars.
Usage Examples
- (Tables predicting planetary positions.)
- (Historical astronomical almanacs.)
Advanced Usage
- "to compute ephemerides": to calculate the positions of celestial bodies using mathematical models.
- Modern ephemerides are generated by computers using gravitational models of the solar system. (Calculations based on physics.)
- "ephemerides in navigation": used historically for maritime navigation to determine longitude at sea.
- Sailors relied on printed ephemerides to find their position using the stars. (Navigation aids.)
Variants and Related Words
- Ephemeris (n, singular): a single table or data set for a specific celestial body or time period.
- The ephemeris for the Moon shows its phases for each day of the year. (Singular form.)
- Ephemeral (adj): lasting for a very short time (etymologically related to "ephemerides," meaning "lasting only a day").
- The beauty of the cherry blossoms is ephemeral. (Short-lived.)
Synonyms
- Astronomical tables: data sets listing positions of celestial objects.
- Almanac: a calendar containing astronomical data and other information (broader term).
- Celestial calendar: a schedule of celestial events.
Related Idioms
- "as fleeting as an ephemeris": poetic expression meaning something changes rapidly, like the daily positions in an ephemeris.
- Her interest in astronomy was as fleeting as an ephemeris — intense but brief. (Short-lived enthusiasm.)
Notes on Usage
- Plural form: "ephemerides" is the standard plural of "ephemeris." It is used in technical and academic contexts, especially in astronomy, astrophysics, and space science.
- Pronunciation: The singular "ephemeris" is pronounced /ɪˈfɛmərɪs/; the plural "ephemerides" is pronounced /ˌɛfɪˈmɛrɪdiːz/.
- Etymology: From Greek (ἐφημερίς) meaning "diary, daily account," from ("on") + ("day"). This reflects the original use of daily astronomical tables.