I do not believe that things get heavier as they accelerate, after all, there is no reason to believe why movement of mass would beget more mass.
Instead, forces seem to become less effective as objects become faster, as is evidenced by the fact that particle accelerators achieve diminishing returns as the speed of light is approached.
A potential model for this is as follows:

* There is no universal absolute or relative speed limit.
  This assumption is derived from the classical assumptions of physics.
* Force fields are emitted with a relative speed of *c* from their sources in all directions.
  This assumption is derived from what we know about electromagnetism.
  This means that forces expand with *c* in concentric spheres centered around the object that emits them.
  Of course, if the source changes its velocity or direction, those spheres are not longer concentric.
* The number of force "spheres" crossed per time determines the rate at which a force is applied to an object.
  This assumption is derived from the intuition that the force fields themselves, whatever they're made of, are exerting the force, and a denser field would exert more force.
  Forces are thus subject to the Doppler effect, with a stationary source.
  Thus, an object moving away from the force field's source at exactly *c* will never cross any force lines, and is therefore unaffected by it.
  Conversely, an object moving towards a force field's source is affected by a factor *>1*, as it experiences more force spheres per time.
* Forces always try to accelerate an affected object towards *±c* relative to the field emitter at the time of emission and the polarity of the force and object.
  An object faster than *c* would thus be decelerated towards *c* when crossing field lines.
  This assumption is derived from the observation that you cannot push something that is faster than yourself, and force fields travel at *c*.

A force now consists of three things:

1. The initial force field magnitude/density *F⁰*.
2. The perceived density of the force field, measured by the frequency of force field fronts passed per time.
  Since there is no medium restricting the maximum velocity something can travel at, we say that the force field source is a stationary emitter for simplicity.
  The velocity *v* of the affected object is its relative velocity to the source.
  With an initial frequency of *1*, the Doppler formular thus yields:

		f = (c±v)/(c±0)·1
		f = (1-v/c)

3. The effectiveness of the applied force due to the speed of the affected object.
  While the force field itself travels at a certain speed, the force it applies also acts at a certain speed (pushing vs pulling forces).
  This speed is assumed to be *±c* with respect to the source of the force field.
  The formula is inspired by the collision of moving objects (force field front and the actual object, assumed to have the same mass for simplicity).
  The less the velocity difference between both objects, the less energy is transferred.

		e = (±c-v)/c = ±1-v/c

The following formula would result:

	F = F⁰·f·e = F⁰·(1-v/c)·(±1-v/c)
	F⁺ = F⁰·(1-v/c)²
	F⁻ = F⁰·((v/c)²-1)

The first result *F+* is for pushing forces, while *F-* is for forces that pull towards the force emitter.

## Observations

We can easily see that objects moving at speeds close to *0* (with respect to *c*) have a force of *F = ±F⁰*, while objects moving at *c* receive no force, as they cross no field lines.
This fulfils the bare minimum requirement to fit observations.
Pulling and pushing forces are unbalanced for speeds around *c/2*, which is curious.
Pulling forces have no effect for objects at *-c*, while pushing forces have 4 times the effect when slowing down objects moving at *-c* (an object moving towards the field at *c* receives 4 times the counter push).
This might be an inaccurate interpretation of how force fields work.


**Todo**: Look into ether interpretation (force fields are ether clouds, intensity of fields = density of ether, force fields move ether (push or pull), wind resistance formula for force application).