In principle, both circle-centre shapes can now be inserted into the frame of reference. This requires an explanation:

In order to be able to insert circle-centre shape A, i.e. the uniform translation of a uniformly rotating Earth on the circle with respect to a stationary Sun in the centre, the Earth has to become central while the Sun is moved to the circle. In this theoretical case, this inversion is allowed by relativity resulting in a uniformly moving Sun on the circle with respect to a stationary, uniformly rotating Earth in the centre.

 
Dual function of the arc of the sun does not seem to be consistent

In the frame of reference, this path of the Sun converges with the earlier arc of the Sun on the vertical circle. But note: This time the arc is not wobbling for the stationary observer in the centre of the earth's surface, as is the case with the arc of the days (see 2.2.), but for a rotating Earth in the lower part of the frame as in the adjoining image. Notice that the uniformly moving Sun with respect to a rotating Earth is not consistent with concluding that the Sun is moving accelerated in this case. This error will be corrected later.

In order to be able to insert the circle-centre shape of the infinite number of seasonal slices on the circle with regard to an infinite number of S '- Sun slices in the centre' (B), one should realize that this circle-centre shape is in fact square with the previous circle-centre shape. This so-called 'circle of seasons' coincides with the earth's horizon in the frame of reference, with spring and summer in the south (see image). Centre S', obviously, will become the centre of the earth's surface, where the Sphere Observer is sitting.

The latter is consistent again with the fact that the seasons exist because of the wobbling of the arc of the Sun with respect to the surface of the Earth. Relativistic, it is allowed to inverse this to a wobbling surface of the earth with respect to the arc of the Sun.

In this way, the reference frame of the Sphere Observer is becoming what is called an inertial frame of reference in the west.



Continue to: 3.2. Reference frame as an eastern inertial frame of reference 2