J. Rogers, SE Ohio
Abstract
This lesson plan demonstrates that Special Relativity (SR) and General Relativity (GR) are not separate theories but different manifestations of a single geometric principle. By systematically transforming equations between frameworks, we prove that gravitational and kinematic time dilation are identical phenomena. The appearance of "separate effects" arises from treating constrained variables as independent. We show that constants like
and
are merely unit conversion factors, and that all relativistic physics reduces to dimensionless ratios of the form
.
Lesson 1: The Fundamental Identity
Learning Objective
Students will algebraically transform the Schwarzschild metric into the Lorentz factor, proving mathematical identity between GR and SR.
The Schwarzschild Metric (General Relativity)
The time dilation near a mass
at radius
is:
This looks complicated. But let's identify what's hidden inside.
The Escape Velocity
The classical escape velocity at radius
is:
Square both sides and normalize by
:
The Transformation
Step 1: Define the dimensionless escape ratio:
Step 2: Substitute into Schwarzschild metric:
Step 3: Recognize the Lorentz factor:
Result:
What We've Proven
The Schwarzschild metric of General Relativity IS the Lorentz transformation of Special Relativity, where the velocity is the escape velocity at that radius.
Gravitational time dilation is not "like" kinematic time dilation—it IS kinematic time dilation with
.Student Exercise 1
Calculate the time dilation at:
Earth's surface (
m)GPS satellite orbit (
m)Sun's surface (
m)
Using both methods. Verify they give identical results.
Lesson 2: The GPS Paradox - Two Effects or One?
Learning Objective
Students will discover that "gravitational" and "velocity" time dilation in orbits are not independent effects but components of a single unified phenomenon.
The Traditional Approach
Textbooks calculate GPS time dilation by summing two "separate" effects:
1. Gravitational time dilation (GR):
2. Velocity time dilation (SR):
Total:
μs/dayThis suggests two separate physical phenomena. But this is an illusion.
The Hidden Constraint
For a GPS satellite in circular orbit, velocity is not a free parameter. Orbital mechanics requires:
Solving for velocity:
The velocity is determined by the gravitational potential!
The Transformation
Step 1: Substitute
into the SR formula:
The "velocity effect" is now expressed entirely as a gravitational potential term.
Step 2: Add the GR and transformed SR effects:
Step 3: Factor out common terms:
Step 4: Simplify:
The Unified Formula
This single equation replaces both "GR" and "SR" calculations.
What We've Proven
The apparent separation into "gravitational" and "velocity" effects is an artifact of treating
as independent when it's constrained by
.There is only one effect: Time dilation in a gravitational potential, where orbital motion contributes a factor of 3/2 instead of 1.
Student Exercise 2
Calculate GPS time dilation using traditional method (two separate effects)
Calculate using unified formula
Verify they match to within numerical precision
Compare two satellites at different orbital radii using unified formula
Data:
m³/kg·s²
kg
m/s
m
m
Lesson 3: The Mystery of the 3/2 Factor
Learning Objective
Students will understand that the 3/2 coefficient emerges from the low-velocity expansion of the Lorentz factor, connecting the Virial Theorem to special relativity.
The Lorentz Factor Expansion
The relativistic energy is:
Taylor expansion for small
:
Kinetic energy:
The famous 1/2 factor in kinetic energy comes from the first-order Taylor expansion of
!Circular Orbits and the Virial Theorem
For a stable circular orbit:
Centripetal force equals gravitational force:
Orbital velocity:
Kinetic energy:
Potential energy:
The Virial Theorem:
or equivalently:
The Geometric Origin
Why exactly 1/2? Because motion is orthogonal to the potential gradient.
In a circular orbit:
Velocity vector: Tangent to the circle (azimuthal direction)
Gravitational gradient: Radial (pointing inward)
Angle between them: 90°
The kinetic component is the tangential projection of the total energy, which in the low-velocity limit gives the 1/2 factor from γ's expansion.
Connecting to Time Dilation
Gravitational time dilation at radius
:
Kinetic time dilation for orbital velocity
:
Ratio:
Total time dilation for orbiting clock compared to distant clock:
This is the origin of the 3/2 factor:
1 part from gravitational potential
1/2 part from orbital kinetic energy (first-order
expansion)
What We've Proven
The Virial Theorem (
2KE=∣PE∣
) is the weak-field limit of the Lorentz factor.The 1/2 in
and the 1/2 in the orbital time dilation are the same 1/2—both arising from the Taylor expansion of γ.Student Exercise 3
Derive the Taylor expansion of
to third orderShow that
For Earth's orbital velocity around Sun (
km/s), calculate:The exact
factorThe first-order approximation
The second-order approximation
Compare errors
Lesson 4: Gravity as Time Gradient
Learning Objective
Students will derive Newton's law of gravitation from the gradient of the time dilation field, showing that acceleration is the slope of time.
The Time Field
Define the dimensionless gravitational potential (in natural units where
G=c=1
):
In SI units:
Time dilation at radius
:
(using weak-field approximation for
)The Gradient
Derivative with respect to radius:
The negative sign indicates that time runs slower (higher
) as you go inward.Free-Fall Acceleration
An object following the natural geodesic (free-fall) experiences acceleration equal to the gradient of the time field:
This is Newton's law of gravitation!
Physical Interpretation
What is "falling"?
At radius
: time rate is τ(r)=1−GM/(c2r)
At radius
: time rate is
(slower)The mismatch in time rates creates acceleration toward slower time
Free-fall = following the time gradient
Standing still = resisting the time gradient (requires force)
Mach's Principle Realized
"Motion is the object's time experience moving in a straight line in a universal time gradient. Force is what is felt when you are prevented from following your natural time path."
Free-fall (weightless):
Following natural geodesic in
fieldZero proper acceleration
No force felt
Standing on ground (weight):
Ground prevents natural motion down time gradient
Non-zero proper acceleration
Force =
What We've Proven
Gravitational acceleration is not a mysterious force—it's simply the gradient (slope) of the time dilation field.
Student Exercise 4
Calculate
for a point mass at the originCalculate
for two masses (Earth + Moon) at arbitrary locationFind the point where
(L1 Lagrange point)Verify that this matches the classical calculation
Lesson 5: Force as the Product of Time Fields
Learning Objective
Students will transform Newton's law of gravitation into a product of dimensionless time dilation factors, revealing that force is the interaction of time fields.
Planck Units Review
The original 1899 Planck units are defined by setting
:
The Planck force is the conversion factor between natural units and SI units.
Newton's Law in Natural Units
In natural units (
), the gravitational force between two masses separated by distance r is:
This is a dimensionless number—a pure geometric ratio.
Converting to SI Units
To get force in Newtons, multiply by the Planck force:
But
and
in natural units need to be converted from SI:
And
needs conversion:
The Complete Transformation
Step 1: Write force in terms of dimensionless potentials:
Step 2: Force as product of potentials:
Step 3: Simplify:
✓ Newton's law recovered!
What We've Proven
Gravitational force is the product of two time dilation fields, scaled by the Planck force unit conversion.
Each factor
in natural units
is the dimensionless time dilation field created by that mass.Force = (time field₁) × (time field₂) × (unit conversion)
The Meaning of G
Newton's gravitational constant is not a fundamental property of gravity—it's a unit conversion factor:
It converts between:
SI units (kg, meters, seconds)
Natural dimensionless ratios (
)
In natural units,
doesn't appear. There is no constant—only ratios.Student Exercise 5
Calculate the dimensionless potential
for:Earth at its surface
Sun at its surface
Neutron star at its surface (
, km)
Calculate the force between Earth and Moon using:
Traditional Newton's law:
Product of potentials:
Verify they match
Show explicitly that
Lesson 6: The Event Horizon as β = 1
Learning Objective
Students will understand that the Schwarzschild radius (event horizon) occurs exactly where escape velocity equals the speed of light.
The Schwarzschild Radius
The event horizon of a black hole is at:
This is traditionally derived from the Schwarzschild metric by finding where
.Escape Velocity at the Horizon
At radius
, the escape velocity is:
Substitute
:
At the event horizon, escape velocity equals the speed of light.
Time Dilation at the Horizon
Using our unified framework:
At the horizon where
:
Time stops at the event horizon.
Physical Meaning
The event horizon is not a mysterious surface—it's simply the radius where:
Escape velocity = speed of light
Time dilation becomes infinite
Light emitted exactly at
can't escape (gravitationally redshifted to zero frequency).What We've Proven
The Schwarzschild radius is the natural consequence of the escape velocity formula:
The event horizon occurs exactly where the time dilation formula
predicts time should stop.This is not a coincidence—GR and SR are the same equation.
Student Exercise 6
Calculate the Schwarzschild radius for:
Earth (
kg)Sun (
kg)Sagittarius A* (
)A stellar-mass black hole (
)
For each, calculate
at:The Schwarzschild radius
2× the Schwarzschild radius
10× the Schwarzschild radius
Lesson 7: Multi-Body Superposition
Learning Objective
Students will understand that gravitational fields from multiple masses simply add as
, and that every object exists in nested orbits around all masses simultaneously.The Superposition Principle
For
masses at positions
with masses
, the total gravitational potential at location
is:
In natural units:
This is exact in the weak-field limit and a good approximation for most astronomical scenarios.
Time Dilation from All Masses
The total time dilation at any point is:
Every mass in the universe contributes to your local time rate.
Example: Standing on Earth
At Earth's surface, you're simultaneously influenced by:
Earth:
Sun:
Moon:
Milky Way (approximate):
(dominant at large scales!)Total:
Nested Orbits
You are never not in orbit. At any moment, you're in nested orbits around:
Earth (24 hour period if at equator, rotating with planet)
Sun (365.25 day period)
Galactic center (~230 million year period)
Local group center
Virgo cluster
Laniakea supercluster
Your time rate is determined by the sum of all these
in natural units
contributions.What We've Proven
There is no such thing as "empty space." Every location has a time rate determined by:
Gravity is not a local interaction between two bodies—it's your position in the global time gradient field created by all mass in the universe.
This is Mach's principle realized: Your local physics is determined by the distribution of all matter.
Student Exercise 7
Calculate the relative contributions to
Φ
at Earth's surface from:Earth
Sun
Moon
Jupiter (approximate as r ∼ 5 AU)
At what distance from Earth does the Sun's contribution equal Earth's?
Estimate the galactic contribution assuming:
Distance to center:
kpc
Lesson 8: Summary and Philosophical Implications
What We've Accomplished
Through systematic transformation of equations, we've proven:
GR = SR with escape velocity:
GPS "two effects" are one:
The 1/2 factor is gamma: Virial theorem = first Taylor term of Lorentz factor
Acceleration = time gradient:
Force = product of time fields:
Event horizon = β=1: Schwarzschild radius is where
Superposition:
determines local time rate
The Core Insight
There is only one phenomenon: position and motion in the universal time gradient field.
What we've historically called "separate effects" are artifacts of:
Using arbitrary measurement units (kg, meters, seconds instead of dimensionless ratios)
Treating constrained variables as independent (
is determined by
in orbits)Separating "gravitational" from "kinetic" when both are aspects of time geometry
Constants Are Unit Conversions
converts SI units to natural ratios
converts time-delay (space) to time-rate (time)Neither encodes fundamental physics—only our choice of measurement units.
Mach's Principle
Force is what you feel when prevented from following your natural path through the time gradient.
Free-fall: Following
→ no force feltStanding still: Resisting
→ force feltAcceleration: Changing path through
Φ
→ force felt
Unity Through Transformation
The test of a unified theory is not philosophical argument—it's whether equations transform into each other algebraically.
We've shown:
Schwarzschild → Lorentz (exact)
Two GPS effects → One unified formula (exact)
Newton's force → Time field product (exact)
Acceleration → Potential gradient (exact)
These are not analogies. They are mathematical identities.
What Remains
This framework successfully unifies weak-field gravity (the observable universe outside black hole horizons). Open questions:
Strong-field regime: Does
work near event horizons, or do non-linear corrections emerge?Cosmology: How does homogeneous mass distribution affect
? Does expansion emerge naturally?Gravitational waves: Can time-dependent
with retardation reproduce GR's predictions?Quantum regime: How does this framework interface with quantum mechanics at the Planck scale?
These are questions for further research. But for 99.9999% of spacetime (weak-field regime), the unity is proven.
Final Assessment
Problem Set
Problem 1: Transform the following equation from SR to GR form:
Problem 2: A satellite orbits at
km (geostationary orbit).
Calculate its time dilation relative to Earth's surface using:
a) Traditional two-effect method
b) Unified formula
c) Show they matchProblem 3: Derive the Schwarzschild radius by setting
in the escape velocity formula.Problem 4: Calculate the gradient
for the Earth-Moon system at the L1 Lagrange point. Verify it equals zero.Problem 5: Express Newton's law
in terms of dimensionless potentials
and
, showing explicitly how
cancels.Problem 6: Two satellites orbit at different altitudes. Using only the unified formula, predict their relative clock rates.
Problem 7: Show that the Taylor expansion of
gives
Problem 8: Calculate the time dilation at Earth's surface including contributions from Earth, Sun, Moon, and Galaxy. Which dominates?
Conclusion
Physics is not a collection of separate theories connected by coincidence. It is a unified geometric structure expressed in different coordinates.
By treating space as time-delay and velocity as a dimensionless ratio, we've shown that SR and GR are the same equation:
, where
can be either actual velocity or escape velocity.Constants like
and
are not fundamental—they're conversion factors between arbitrary human units and natural dimensionless ratios.The universe computes in ratios. We've just been adding unit labels and then treating them as physics.
This lesson plan teaches unity through transformation—showing that equations which appear different are algebraically identical. That is the signature of true understanding.
References for Further Study
The GPS satellite data for empirical verification
Taylor & Wheeler, "Exploring Black Holes" (for Schwarzschild geometry)
Misner, Thorne & Wheeler, "Gravitation" (for the full GR mathematical machinery)
Natural units and dimensional analysis in physics
Mach's principle and the origin of inertia
Weak-field limit of General Relativity
The student who understands transformation understands unity.
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