However just the anisotropy of the cosmic microwave background was found in 1977, the scientists have understood that fact that our inertial reference frame
, connected to the Earth, moves with a velocity of about 360 km/sec with respect to a "preferred" inertial reference frame
, where the microwave background radiation is mostly isotropic so that the common momentum of all space masses of our Universe is zero.
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.
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.
We initially calculate the energy density D' in the inertial reference frame
S' in which the material particle is at rest.
The situations of the two twins A and B are reported in comparison with an inertial reference frame