Redefining Mercury’s Apparent Ecliptic Speed Using 200 Years of Empirical Astronomical Data (1900–2100)

Author

MINAKAWA Takeshi
Astrogrammar Research, Charapla Inc,
Yokohama, Japan
November 17th, 2025
[日本語版]

Abstract

Traditional astrological classifications of Mercury’s apparent daily speed—Slow, Average, and Fast—have historically been determined by conventional intuition rather than empirical astronomy. This study calculates 73,213 days of Mercury’s geocentric apparent ecliptic longitude speed from 1900 to 2100 using the JPL DE440s ephemeris and the Skyfield computation library. The resulting distribution reveals statistically robust boundaries based on quartiles and physically meaningful structures related to Mercury’s orbital dynamics. We propose a new five-tier classification—Ultra-slow, Slow, Average, Fast, Very-fast—which integrates statistical percentiles and dynamical constraints near retrograde stations. This framework represents fully empirical and reproducible standard for Mercury’s speed in both astronomical and astrological contexts.
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