Two reference frames,

inertial reference frame and body reference frame, are required to obtain the model.

In other words, the generalized photon carries intrinsic angular momentum even in the

inertial reference frame in which the material particle is at rest.

We again emphasize that the proper current density entering into the definitions (36a)-(36b) is the divergence-free in any

inertial reference frame.

It is then well known--see, for example, Lawden (1962)--that if the voyage from Earth to Trantor appears to take n years to observers in the Earth-Trantor

inertial reference frame, it will appear to take [bar.

Instead of using

inertial reference frame, the virtual skyhook vibration isolator uses a secondary tuned spring-mass-damper system.

To describe the motion of a particle relative to a body that is rotating with respect to an

inertial reference frame is clearly a complicated matter.

Given a local (moving)

inertial reference frame, the clocks of which are synchronized to the "preferred" (resting) intertial reference frame assigned to the Universe as a whole ((double dagger]), an observer located in this local (moving) reference frame, should register an inverse (1 + | cos 0) effect on the physically observed velocity of the light signals (photons) assigned to his (moving) reference frame, while the world-invariant of the velocity of light remains unchanged.

As a result of these, Tangherlini had deduced the so-called the Tangherlini transformations, which are a sort of the transformations of the spatial coordinates and time being moved from one

inertial reference frame into another one.