Retrograde motion
Retrograde is a sign flip of geocentric longitude velocity, not a cause. · 7 min
The definition used here
retrograde = longitudeVelocity < 0 on a geocentric ecliptic longitude. Velocities are a symmetric finite difference (±1 hour by default). The flag is meaningless for the Sun and Moon in the geocentric frame used by the Lab.
Sky at 2020-11-03 00:00 UTC · geocentric, true ecliptic of date. No market claim.
Key points
- A station is where longitude velocity crosses zero. The calendar refines that time by bisection.
- Mercury’s station direct on 2020-11-03 is a fixture in the test suite.
- Apparent retrograde is a line-of-sight effect of relative orbits. It is not evidence about markets until an experiment says so — and even then the language is historical association.
Caveat
Do not treat “Mercury retrograde” as a prediction. The Lab can only ask whether samples tagged with this geometric flag differed from controls on a chosen market window.
References
- astronomy-engine
- Explanatory Supplement to the Astronomical Almanac — Urban S.E. and Seidelmann P.K. (eds.), 3rd ed., 2013