MOND Unification

10% Error
a₀ = cH₀ / (2π) ≈ 1.08 × 10−10 m/s²
The MOND acceleration scale from cosmology

This is one of Synchronism's strongest results. The MOND acceleration scale a₀ — a number that Milgrom introduced in 1983 as a fundamental constant of nature —emerges from basic cosmological parameters. It is not fundamental. It is derived.

The Significance

In Modified Newtonian Dynamics (MOND), a₀ is the acceleration below which gravity deviates from Newton's law. Milgrom observed it empirically:

a₀obs ≈ 1.20 × 10−10 m/s²
Milgrom's observed value (1983)

For 40 years, the coincidence that a₀ ≈ cH₀ has been noted by many researchers but never explained. It could be a numerical accident. In Synchronism, it is a derivation: the coherence function, applied at cosmological scale, produces this relationship with a factor of 2π that comes from the geometry of the horizon.

The Derivation Chain

Step 1: Critical Density of the Universe

ρcrit = 3H₀² / (8πG)

Standard cosmology. The density at which the universe is flat. This is measured, not assumed.

Step 2: Coherence Transition

At the coherence transition (C ≈ 0.5), the gravitational acceleration from ρcrit over a Hubble-scale volume defines the threshold where dynamics change. The 2π factor arises from the spherical geometry of the causal horizon.

Step 3: The Result

a₀ = cH₀ / (2π)

Plugging in H₀ = 67.4 km/s/Mpc and c = 3 × 108 m/s gives 1.08 × 10−10 m/s². Milgrom's observed value: 1.20 × 10−10. Error: ~10%.

Comparison

MOND (Milgrom 1983)

  • a₀ is a fundamental constant
  • Value determined empirically from galaxy fits
  • No explanation for why a₀ ≈ cH₀
  • Extremely successful at fitting rotation curves

Synchronism

  • a₀ is an emergent scale
  • Value derived from H₀ and c
  • The cH₀ coincidence is explained, not assumed
  • Inherits MOND's empirical success plus adds environment dependence

Sessions and History

Derived in Sessions #87–88 of the autonomous research program. The derivation was independently stress-tested in Session #91, where the same result was obtained from a different starting point (via Freeman's Law). Both derivations agree, providing internal consistency.

Next: Freeman's Law →Try It: MOND Comparator

Prerequisites

Understanding these concepts first will help:

Parameter DerivationsFirst-principles origin of every parameterDark Matter ReframedPatterns interacting indifferently: gravity only, no EM

Related Concepts

Galaxy Rotation CurvesSPARC (175) + ALFALFA-SDSS (14,585 galaxies)Freeman's LawΣ₀ from first principlesMOND-Synchronism ComparatorSide-by-side a₀ derivation vs empirical MOND