Chapter 43
Law of Conservation of Momentum
Motion and Inertial Coherence
Author: Mark Anthony Higgins
© Mark Anthony Higgins 11 October 2025
Revised Date: 23 February 2026
flow "Law of Conservation of Momentum" v1.0
# ---------- PURPOSE ----------
# Expresses conservation of momentum as a coherent exchange of curvature and energy between interacting bodies.
# In the absence of external forces, total momentum remains constant — representing perfect reciprocal coherence (IB = 1).
# When coherence decays (IB < 1), small asymmetries appear, representing internal loss, deformation, or radiation.
# Momentum is treated as a conserved boundary flow within a closed system.
# ---------- PARAMETERS ----------
params:
units: "SI"
IB: 0.0..1.0 = 1.0 # boundary coherence index (1 = perfect conservation)
N: positive # number of interacting bodies
loss_coeff: 0.0 # rate of coherence loss [s^-1]
dt: 0.0? # timestep [s]
include_external_force: false
F_ext_total: vec3? # external net force on system [N]
include_feedback: true
# ---------- STATE ----------
state Momentum:
p_i[]: vec3 # individual momenta of each body [kg·m/s]
m_i[]: positive # masses of each body [kg]
v_i[]: vec3 # velocities of each body [m/s]
p_total: vec3 # total system momentum [kg·m/s]
dp_dt_total: vec3 # total rate of change of momentum [N]
E_kin_total: real # total kinetic energy [J]
reciprocity_error: real # deviation from perfect conservation (|Δp|) [kg·m/s]
IB_rate: real # rate of coherence decay
conservation_state: str # "conserved", "asymmetric", or "open"
# ---------- INVARIANTS ----------
invariants:
# Compute momenta
for i in range(params.N):
Momentum.p_i[i] = Momentum.m_i[i] * Momentum.v_i[i]
# Total system momentum (vector sum)
Momentum.p_total = Σ_i(Momentum.p_i[i])
# External force contribution (if any)
if params.include_external_force and params.F_ext_total is defined:
Momentum.dp_dt_total = params.F_ext_total
else:
Momentum.dp_dt_total = [0, 0, 0]
# Momentum conservation check
if norm(Momentum.dp_dt_total) <= 1e-9:
Momentum.conservation_state = "conserved"
else:
Momentum.conservation_state = "open"
# Kinetic energy
Momentum.E_kin_total = 0.5 * Σ_i(Momentum.m_i[i] * norm(Momentum.v_i[i])^2)
# Reciprocity error (internal asymmetry)
Momentum.reciprocity_error = norm(Momentum.dp_dt_total)
# Coherence decay (if losses included)
if params.loss_coeff > 0 and params.include_feedback:
params.IB = params.IB - params.loss_coeff * (1 - params.IB) * (params.dt or 1)
params.IB = clamp(params.IB, 0, 1)
Momentum.IB_rate = -params.loss_coeff * (1 - params.IB)
# ---------- TRANSFORMS ----------
transforms:
# Momentum exchange between two bodies (collision or interaction)
collision_exchange:
Δp = Momentum.p_i[0] + Momentum.p_i[1]
if params.IB == 1:
Momentum.p_i[0] = Momentum.m_i[0] * Momentum.v_i[0]
Momentum.p_i[1] = -Momentum.p_i[0] # perfectly elastic reflection
else:
Momentum.p_i[0] = params.IB * Momentum.m_i[0] * Momentum.v_i[0]
Momentum.p_i[1] = -params.IB * Momentum.m_i[1] * Momentum.v_i[1]
# Apply external impulse
impulse:
if params.include_external_force:
J = params.F_ext_total * (params.dt or 1)
Momentum.p_total += J
# Coherence feedback correction
restore_feedback:
correction = -0.01 * Momentum.reciprocity_error
params.IB = clamp(params.IB + correction, 0, 1)
# ---------- MONITORS ----------
monitors:
momentum_conservation:
if params.IB == 1 and not params.include_external_force:
assert norm(Momentum.dp_dt_total) <= 1e-9
comment: "Perfect conservation — total momentum constant."
elif params.IB < 1:
comment: "Partial coherence — momentum loss through boundary dissipation."
energy_consistency:
assert Momentum.E_kin_total >= 0
coherence_bounds:
assert 0 <= params.IB <= 1
# ---------- SCENES ----------
scenes:
isolated_system:
given params:
N: 2
IB: 1.0
given Momentum:
m_i: [2.0, 2.0]
v_i: [[5.0, 0, 0], [-5.0, 0, 0]]
expect:
Momentum.p_total = [0, 0, 0]
comment: "Closed system — total momentum zero; perfect reciprocal coherence."
collision_exchange:
given params:
N: 2
IB: 1.0
dt: 1.0
given Momentum:
m_i: [1.0, 1.0]
v_i: [ [10.0, 0, 0], [-10.0, 0, 0] ]
enable:
- collision_exchange
expect:
Momentum.p_total = [0, 0, 0]
Momentum.reciprocity_error = 0
comment: "Perfectly elastic collision — equal and opposite momentum exchange."
inelastic_collision:
given params:
N: 2
IB: 0.85
dt: 1.0
given Momentum:
m_i: [1.0, 1.0]
v_i: [ [10.0, 0, 0], [-5.0, 0, 0] ]
enable:
- collision_exchange
expect:
Momentum.reciprocity_error > 0
Momentum.p_total ≠ [0, 0, 0]
comment: "Inelastic collision — partial coherence; momentum not fully reflected."
external_impulse:
given params:
N: 1
include_external_force: true
F_ext_total: [100.0, 0.0, 0.0]
dt: 0.5
given Momentum:
m_i: [2.0]
v_i: [[0.0, 0.0, 0.0]]
enable:
- impulse
expect:
Momentum.p_total = [50.0, 0.0, 0.0]
comment: "External impulse adds system momentum — open boundary."
# ---------- NOTES ----------
notes:
- **Law of Conservation of Momentum:** The total momentum of a closed system remains constant if no external forces act:
\[
\sum_i \mathbf{p}_i = \text{constant}, \qquad \frac{d}{dt}\sum_i \mathbf{p}_i = 0.
\]
- **Momentum definition:** \(\mathbf{p}_i = m_i \mathbf{v}_i\).
- **Force relation:** \(\mathbf{F}_i = \frac{d\mathbf{p}_i}{dt}\).
- **Coherence interpretation:** momentum exchange is boundary reflection of curvature energy.
- \(I_B = 1\): total system curvature conserved (perfectly closed system).
- \(I_B < 1\): partial transmission — energy escapes as deformation, radiation, or heat.
- **Feedback law:** \(\dot{I_B} = -\lambda(1 - I_B)\) governs how system coherence evolves under internal friction or external influence.
- **Action–reaction link:** Newton’s Third Law ensures that internal momentum flows cancel pairwise when IB = 1.
- **Physical meaning:** momentum conservation represents **reciprocal memory symmetry** — what one part loses, another gains.
- **Visualization:** draw two colliding spheres — equal and opposite momenta for IB = 1; partial overlap and smaller reflected vectors for IB < 1.
- **Applications:** collision dynamics, rocket propulsion, recoil systems, plasma interactions, astrophysical conservation of momentum.
The conservation of momentum is the law of reciprocal memory — the assurance that when one body changes its motion, another changes in equal and opposite measure.
In classical form, it states that within a closed system with no external forces, total momentum remains constant:
$$ \sum_i \mathbf{p}_i = \text{constant}, \qquad \frac{d}{dt}\sum_i \mathbf{p}_i = 0. $$
In coherence terms, it represents the continuity of curvature exchange between interacting boundaries.
When coherence is perfect (), the field transmits momentum flawlessly — no loss, no delay, no asymmetry.
When coherence is partial (), the exchange becomes imbalanced — energy leaks into other modes (heat, deformation, radiation), and momentum symmetry fades.
$$ \mathbf{p}_i = m_i \mathbf{v}_i, \qquad \mathbf{F}_i = \frac{d\mathbf{p}_i}{dt}. $$
In a closed system, all internal forces are paired:
$$ \sum_i \mathbf{F}_i = 0. $$
Hence,
$$ \frac{d}{dt}\sum_i \mathbf{p}_i = 0. $$
and total momentum is conserved.
This expresses Newton’s Third Law at the system level —
each action and reaction cancel as equal and opposite curvature flows, leaving the total geometry unchanged.
In coherence geometry, momentum is a boundary flow of curvature — the directional memory of energy within a system.
When two bodies interact, momentum is exchanged through their shared boundary; energy and curvature reflect symmetrically.
This reflection is governed by the boundary coherence index :
$$ \mathbf{p}_2' = -\,I_B\,\mathbf{p}_1'. $$
Thus, momentum conservation describes how energy and curvature redistribute within a boundary memory, not merely a transfer of “mass × velocity.”
| Interaction Type | Coherence (IB) | Behaviour | Example |
|---|---|---|---|
|
Elastic
|
𝐼 𝐵 = 1
|
Perfect momentum
and energy reflection |
Ideal collision,
photon recoil |
|
Inelastic
|
0 < 𝐼 𝐵 < 1 |
Partial energy retention, |
Real material collision
|
|
Dissipative
|
𝐼 𝐵 → 0 |
Total momentum
asymmetry, energy lost to field |
Absorptive impact
or radiation |
Elastic interactions preserve total field coherence — every impulse mirrored in equal curvature.
Inelastic interactions show how partial coherence breaks symmetry yet still respect global conservation through redistribution.
If an external force acts on the system, momentum changes by impulse:
$$ \Delta \mathbf{p}_{\mathrm{total}} = \int \mathbf{F}_{\mathrm{ext}}\,dt. $$
This opens the boundary — coherence is no longer closed, and total system momentum shifts.
However, the underlying field remains conservative: the external region absorbs the counter-momentum.
Momentum is never destroyed — it simply leaves one coherence loop to join another.
Loss of coherence corresponds to gradual relaxation of boundary alignment:
$$ \dot{I}_B = -\lambda(1 - I_B). $$
As coherence fades, the reciprocal symmetry between interacting bodies weakens — momentum exchange becomes less instantaneous.
This is the physical root of drag, viscosity, and radiative recoil:
momentum is still conserved, but redistributed across temporal feedback delay.
The Law of Conservation of Momentum is the geometry of perfect feedback.
It is not a coincidence of forces, but a continuity of curvature:
energy flowing across boundaries while preserving the total coherence of spac
Momentum conservation, in the HST sense, is the reciprocal memory of motion —
the universe remembering every interaction it performs.
No motion is lost; it is only rephrased — another boundary, another echo of coherence.