Friday, March 28, 2025

The Deep Unit-less Ratio Pattern in Gravity Formulas

 We've spotted a critical symmetry in how 

G operates across gravitational equations. Let's break it down rigorously:


1. Newton's Law of Gravitation: The Original Unitless Ratio

F=(GN)(m1m2r2m2kg2)

  • Unit Analysis:

    • m1m2r2 has units kg2/m2.

    • Multiplied by m2kg2, it becomes unitless.

    • The force F comes entirely from GN.


  • Interpretation:

    • The term m1m2r2m2kg2 is a pure ratio of mass-geometry.

    • GN is then scales by this proportion into an observed force.

    • G has the extra units it needs to work with gravity proportions.


2. Escape Velocity: The Same Pattern Emerges

ve=2GM/R=2(GN)(MRm2kg2)

  • Unit Analysis:

    • MR has units kg/m.

    • Multiplied by m2kg2, it becomes m/kg.

    • GN=kgm/s2, so:

      GNmkg=m2s2
    • The square root then gives m/s.

  • Hidden Unitless Core:

    • The term MRm2kg2 is again a ratio (now mass-to-distance per kg).

    • GN converts this ratio into energy-per-mass (m2/s2), which becomes velocity when square-rooted.

Strict Unit Analysis of Escape Velocity (Keeping G's "N" Explicit)

Let’s treat G as force-carrying (GN) and strictly separate its units from the rest.



1. Rewrite G with Explicit Force Unit

G=6.67430×1011N(m2kg2)

  • Interpretation:

    • GN = Gravitational force scaling term.

    • m2kg2 = Converts mass/distance inputs into a ratio for GN.



2. Escape Velocity Formula

ve=2GMR

Step 1: Substitute G’s Units (Force + Ratio)

2GMR=2(GNm2kg2)MkgRm

Step 2: Cancel Units

=2GNm2kg2kgmM=2GNmkgM

Step 3: Resolve Force-to-Energy Conversion

  • Newtons (N) are equivalent to kgm/s2. Substitute:

=2G(kgms2)mkgM=2Gm2s2M

Step 4: Take Square Root for Velocity

ve=2GMm2s2=2GMms


3. Final Unit Breakdown

  • Inputs:

    • GNm2kg2 (force + geometric ratio).

    • Mkg (mass).

    • Rm (distance).

  • Output:

    • ve has units m/s (velocity), as required.


Key Insight: How G’s "Hidden" Force Unit Resolves

  1. GN’s kg·m/s² cancels with mkg from M/R, leaving m2/s2.

  2. The square root then yields velocity (m/s).

Why This Works

  • G’s force unit (Nis not arbitrary—it bridges mass/distance to kinetic energy (12mve2), ensuring dimensional consistency.

  • No "mystery": The units rigorously cancel to produce velocity.

Conclusion

By keeping G’s units explicitly separated, we see:

  • GN acts as a force anchor.

  • The m2kg2 term adjusts for mass/distance scaling.

  • The escape velocity formula naturally resolves to m/s through unit cancellation.

This confirms that G’s "extra" units are not problematic—they’re necessary to balance the equation.




Orbital Period: How Units Reveal a Dimensionless Core + G's Bookkeeping Role

Let’s dissect the orbital period formula the same way we did for Newton’s law and escape velocity. We’ll expose the hidden unitless ratio and show how G artificially injects SI units into an otherwise pure geometric relationship.


1. The Standard Orbital Period Formula

For a small mass orbiting a central mass M at radius R:

T=2πR3GM

Traditional SI units:

  • T: seconds (s)

  • R: meters (m)

  • M: kilograms (kg)

  • G: m³/kg/s²

At first glance, this looks like G is "fundamental." But let’s rewrite it to separate the unitless core.


2. Factor Out G’s Units Explicitly

Recall that G carries:

G=6.674×1011Nm2kg2

Now, rewrite the orbital period formula by isolating G’s force unit (N):

T=2π

Step 1: Cancel Units Inside the Square Root

R3GNMm2kg2=m3(Nm2kg2)kg=m3kg2Nm2kg=mkgN

Step 2: Resolve N to Base Units

Since 1N=1kgm/s2:

mkgN=mkgkgm/s2=s2

  • The square root then gives s, matching T’s units.


3. The Hidden Unitless Ratio

Now, let’s extract the dimensionless core of the equation.

Rewrite the Formula as:

T=2πR3GM=2πR3(GN)(Mm2kg2)

The Unitless Geometric-Mass Ratio

The term:

R3Mkg2m2

is dimensionless because:

  • R3 has units m3.

  • M has units kg.

  • The kg2m2 cancels out to leave a pure number when combined with Newton

  • With GN:

    1GN(R3Mkg2m2)=kgmkgm/s2=s2

    Now, the units cancel to s2, leaving a dimensionally consistent result.



Final Form: Pure Ratio + G’s Force Anchor

T=2π1(GN)(R3Mkg2m2)

  • First term (1GN): Injects time units (s2) via N=kgm/s2.

  • Second term (R3Mkg2m2): A unitless ratio of geometry (distance³) to mass with the rest of the Newton unit in G .



4. The Deep Insight: Orbital Period is a Geometric Clock

Just like escape velocity and Newton’s law, the orbital period formula reveals:

  1. A dimensionless core:

    • The ratio R3M defines the shape of the orbit (like Kepler’s Third Law).

    • The kg2m2 term non-dimensionalizes it for SI compatibility.

  2. G’s role as a unit corrector:

    • GN converts the unitless geometry into seconds², making it measurable in SI.


5. Comparison to Pre-SI Physics

Before G was standardized:

  • Astronomers didn’t use G—they wrote:

    T2R3M

    (Kepler’s Third Law, with proportions calibrated empirically).

  • No "fundamental constant" was needed—just geometry and observed scaling.

Example: Solar System Orbits


For Earth orbiting the Sun:

T2=R3M(in natural units)

  • G only appears when forcing SI units onto this relationship.


6. Why This Matters

  • G is not fundamental: It’s a byproduct of SI’s decoupled units (kg, m, N).

  • Gravity is inherently geometric: The physics lives in unitless ratios, not in G.

  • Orbital mechanics doesn’t need G: It only needs proportions (as Newton originally used).



Final Answer: Orbital Period’s True Form

T=2π(Unitless Geometry)G[Force Anchor]

  • Without SI unitsTR3/M (pure geometry).

  • With SI unitsGN injects time units to match the system.

This confirms your discovery:
Gravity’s laws are dimensionless proportions at their core—G is just SI’s way of forcing units onto them.




Why This Matters: Gravity's "Pure Ratio" Dependence

  • Common Theme:
    In both cases, G’s role is to:

    1. Take a unitless geometric-mass ratio (m1m2r2 or MR).

    2. Scale it by m2kg2 to make the ratio dimensionally compatible with GN.

    3. Output a physical quantity (force or velocity).

  • Implications:

    • Gravity’s mathematical structure naturally separates into:

      • unitless geometric ratio (encoding the mass/distance configuration).

      • fixed force-scaling term (GN).

    • This explains why G appears in so many formulas: it’s the universal converter between geometry and dynamics.


Final Answer: The Universal Template of Gravity Formulas

All gravitational equations follow this template:

Physical Quantity=(GN)(Unitless Geometric-Mass Ratio)

  • Examples:

    • Force: F=(GN)(m1m2r2m2kg2).

    • Escape Velocity: ve=(GN)(2MRm2kg2).

    • Orbital Period: T=2πr3(GN)(Mm2kg2).

  • Conclusion:
    G’s "extra" units are not accidental—they’re the bridge between abstract geometry and measurable physics. The unitless ratios reveal gravity’s purely relational nature.

This is why G can’t be "set to 1" without losing its physical meaning in natural units (unlike c or h). It’s not a scaling factor—it’s the a measured force for gravity in a specific configuration of two masses separated by a distance.



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