EPHEMERIS TIME Meaning and
Definition
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Ephemeris time (ET) is a time scale used in astronomy and geodesy to predict the positions of celestial bodies with high precision. It is a continuous and uniform timescale that is independent of the Earth's irregular rotation and orbital motion.
The term "ephemeris" refers to a table or set of mathematical equations that provide the positions and other relevant data of celestial objects at specific times. "Ephemeris time" is the system that employs these tables or equations to calculate and measure time intervals accurately.
In traditional astronomical timekeeping systems, such as Universal Time (UT), Earth's rotation and revolution are used as references to measure time. However, due to the irregularities in Earth's rotation and orbit, UT is not a consistent timescale. In contrast, ephemeris time is based on the motion of celestial bodies, particularly the Sun, Moon, and major planets, which have more predictable and constant movements.
Ephemeris time is calculated by determining the positions of these celestial objects relative to the Earth and using these positions to define specific timeframes. This time scale is essential in astronomy and space exploration, as it allows for precise calculations of celestial events and navigation of satellites and spacecraft.
Since 1984, ephemeris time has been replaced by the more accurate and uniform system known as "terrestrial time" (TT). Nonetheless, ephemeris time still holds historical significance in the field of astronomical computations and research.
Common Misspellings for EPHEMERIS TIME
- wphemeris time
- sphemeris time
- dphemeris time
- rphemeris time
- 4phemeris time
- 3phemeris time
- eohemeris time
- elhemeris time
- e-hemeris time
- e0hemeris time
- epgemeris time
- epbemeris time
- epnemeris time
- epjemeris time
- epuemeris time
- epyemeris time
- ephwmeris time
- ephsmeris time
- ephdmeris time
Etymology of EPHEMERIS TIME
The word "ephemeris" comes from the Greek word "ephēmeros", which means "daily". In astronomy, an ephemeris refers to a table or almanac that provides the positions and movements of celestial objects over a given period.
The term "ephemeris time" was coined by the International Astronomical Union (IAU) in the mid-20th century. It refers to a uniform time scale based on the revolution of the Earth around the Sun, independent of the irregularities in the Earth's rotation. Ephemeris time was developed to improve the accuracy of astronomical calculations and observations.
Similar spelling words for EPHEMERIS TIME
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