Precession
How It Works introduced two counter-rotating motions as the foundation of the model. This page traces how their interaction produces the complete precession picture: the 335,317-year Earth Fundamental Cycle and the cascade of precession sub-cycles (axial, inclination, perihelion, obliquity) that derive from it.
The Two Fundamental Motions
| Motion | Direction | Period | What Moves |
|---|---|---|---|
| Axial Precession | Clockwise | ~25,794 years | Earth around its wobble center |
| Inclination Precession | Counter-clockwise | ~111,772 years | Earth’s perihelion point around Sun |
These two motions, running in opposite directions, create all the precession phenomena we observe.
The Earth Fundamental Cycle
When axial and inclination precession interact, they create a complete cycle called the Earth Fundamental Cycle:
- Duration: 335,317 years
- Ratio: 13 axial cycles = 3 inclination cycles
- Pattern: Based on the Fibonacci sequence (3, 5, 8, 13…)
All Precession Cycles Derived
From the Earth Fundamental Cycle of 335,317 years, all other cycles can be calculated:
| Cycle | Formula | Mean Duration |
|---|---|---|
| Earth Fundamental Cycle | 335,317 ÷ 1 | 335,317 years |
| Inclination Precession | 335,317 ÷ 3 | ~111,772 years |
| Ecliptic Precession | 335,317 ÷ 5 | ~67,063 years |
| Obliquity Cycle | 335,317 ÷ 8 | ~41,915 years |
| Axial Precession | 335,317 ÷ 13 | ~25,794 years |
| Perihelion Precession | 335,317 ÷ 16 | ~20,957 years |
The numbers 1, 3, 5, 8, 13 are all Fibonacci numbers. This suggests a balanced, stable system. These same Fibonacci numbers also govern the relationships between planetary eccentricities and inclinations — see Fibonacci Laws for an accessible overview, or Fibonacci Laws Derivation for the full technical treatment.
Obliquity and Ecliptic Precession are covered in detail on the Obliquity & Inclination page.
Axial Precession
Earth’s axis slowly traces a circle in the sky over ~25,794 years. This is why the North Star changes over time:
- Today: Polaris
- ~2900 BC: Thuban
- ~13,700 AD: Vega
In mainstream astronomy this cycle is called the precession of the equinoxes — because the equinox points slowly drift along the ecliptic — and is also known popularly as the Great Year or Platonic Year. In the model, this is caused by Earth orbiting its wobble center in a clockwise direction.
Inclination Precession
Earth’s perihelion point orbits the Sun counter-clockwise in ~111,772 years. This motion:
- Changes Earth’s orbital inclination
- Shifts the calendar date of perihelion
- Contributes one component to the inclination-side family of cycles visible in ice-core climate records (empirical centroid at the Mercury–Mars nodal beat at 107.3 kyr; see Orbital Forcing Formula)
Perihelion Precession
Every ~20,957 years, axial and inclination precession meet:
- The last calculated alignment was in 1246 AD
- December solstice aligned exactly with perihelion
- This marks the start/end of a complete perihelion precession cycle
Connection to Climate
The 335,317-year Earth Fundamental Cycle appears in historic temperature records. The ~100k-year patterns visible in ice cores belong to the inclination-side family of eigenmode beats — empirical centroid at the Mercury–Mars s₁−s₄ nodal beat at 107.3 kyr (a planet-pair orbital-plane coupling). Earth’s intrinsic inclination precession (~111,772 years) is one theoretical pathway within this family; three of these complete one Earth Fundamental Cycle (3 × ~111,772 = 335,317 years). See Orbital Forcing Formula for the empirical record.
Earth’s climate is also affected by solar cycles, volcanic activity, and other factors. Within the orbital-forcing component, the model proposes the inclination-side family — including Earth’s H/3 inclination precession — as the relevant driver of the post-MPT ~100k-year band.
Comparison with Standard Formulas
The longitude of perihelion specifies the angular direction of Earth’s closest approach to the Sun, measured from the vernal equinox. The model’s predictions closely match the polynomial formulas from Meeus (1998) for thousands of years around the present.
Comparison with Meeus shows close agreement near the current epoch: the model predicts 85.764° at 1000 AD versus Meeus’s 85.788° (Δ = 0.025°), and 111.446° at 2500 AD versus 111.546° (Δ = 0.100°). Beyond ~3,000 AD, the two predictions diverge — the model completes 360° in a mean period of ~20,957 years (with a varying rate within each cycle), while Meeus’s polynomial extrapolation deviates increasingly.
Beyond Earth: The Solar System Resonance Cycle
The Earth Fundamental Cycle (H = 335,317 years) is the smallest period in which Earth’s precession sub-periods all complete. The model also identifies a longer Solar System Resonance Cycle of 8H = 2,682,536 years, in which every planet’s cycles return to their starting configuration simultaneously. The per-planet analysis further shows that Earth’s Fundamental Cycle is uniquely shorter than any other planet’s. See Fundamental Cycles for the full treatment, including the System Reset epoch and per-planet breakdown.
Calculate Precession at Any Year
To calculate axial precession, inclination precession, and other cycle durations for any year, see the Formulas page which provides the complete formulas.
Key Takeaways
- Two motions create all precession: axial (clockwise) and inclination (counter-clockwise)
- Fibonacci ratios connect all cycle durations
- 335,317 years is the complete Earth Fundamental Cycle
- ~20,957 years is the perihelion precession cycle (when the two motions meet)
- Cycle durations match mainstream values to within a few percent
Continue to Obliquity & Inclination to learn how axial tilt and orbital inclination interact to create the obliquity cycle.