Moving objects in retarded gravitational potentials of an expanding spherical shell/Conclusion

Conclusion

The considerations described above show that retarded gravitational potentials can contribute to the explanation of the accelerated expansion of the visible part of the universe, if the outer spherical black shell of the universe would consist of expanding matter with a huge mass. This would also hold in a steady state universe and even if the black shell would not move at all. In the latter case any moving masses within the black shell would reach the black shell in finite time.

It can also be considered that the effect of the retarded gravitational potentials will accelerate moving objects the more, the faster they move and the closer they are to the black shell. Furthermore, also objects within smaller spherical shells that not only are surrounded by the black shell, but also by other visible objects, will experience the retarded gravitational potentials of these objects, and therefore, they will experience an additional acceleration which is directed outwards. This all leads to an inhomogeneous evolution of the mass density in particular during the early development stages of an inflating universe:

• Evolvement of the mass density in an expanding spherical universe with constant mass
• 
  Evolvement of the universe with instant gravitational potentials in a homogeneous sphere.
• 
  Evolvement of the universe with retarded gravitational potentials. Due to the acceleration of matter in the direction of the outer rim of the universe, a shell is growing with a thickness corresponding to its Schwarzschild distance (bluish). This matter within this shell cannot emit any electromagnetic radiation or send any information back to the centre of the universe, since the strong gravitational forces keep the radiation and all masses within the shell.

The agglomeration of mass in the outer areas of our universe not only leads to a shell with increased mass density, but the high mass density could also be the seed for primordial black holes, which could be a reason for the formation of very early galaxies observed by the James Webb Space Telescope (JWST).

Computing the corresponding and permanently increasing Schwarzschild distances gives three remarkable points:

1. Today we can observe the cosmic microwave background at a cosmic age of 380,000 years, where the Schwarzschild distance was increasing much faster than the mass of the black shell.
2. The most distant known galaxy JADES-GS-z14-0 has a cosmic age of 290 million years, where the increase of the Schwarzschild distance with the mass of the black shell became much smaller.
3. The Schwarzschild distance for the equality of the masses of the visible universe and the black shell is 860 million light-years. This value is rather close to the distances that are computed by the standard ΛCDM model between the particle horizon that expands with speed of light and the visible horizon that can be observed as the cosmic microwave background.

Cosmologists call the period in between the creation of the cosmic microwave background and the first stars as the dark ages, where dark matter is supposed to be transformed into "dark energy". So far, the nature of "dark energy" is unclear, but the increase of the mass of an invisible black shell behind the visible universe could contribute to find explanations.

Due to Newton's third law (actio = reactio) the black shell experiences the same retarded gravitational forces as the moving masses within the shell. These forces will cause a deceleration of the shell which is the stronger the closer the masses within the visible universe are to it.

The high velocity of visible objects in the vincity of the black shell as well as the huge mass of the matter in front of them seem to be the reasons for the extreme redshift of their light that can be observed by us. The observation that this redshift is greater than expected for distant objects led to the assumption that the further away these objects are, the more they are accelerated. Another reason for this could be found in the effects of the retarded gravitational potentials of a massive black shell. Furthermore, the additional gravitational redshift leads to a higher value than expected only by the relativistic Doppler effect. This is in accordance with the observations of very far and young galaxies such as JADES-GS-z14-0 or of the cosmic microwave background (CMB).

However, the computation of the equations of motion based on retarded gravitational forces becomes very expensive, if the black shell is neither homogeneous, nor spherical or symmetrical, or if the concept of spacetime has a structure based on a non-Euclidean geometry. Furthermore, relativistic effects (including the transverse Doppler effect) could cause time dilatation or mass increase that would have to be considered, too. Finally, is would be necessary to consider the loss of mass in the visible universe over the time, since a significant amount of visible matter may have traversed the event horizon that is caused and built by the huge mass in the black shell of the universe.

If matter and antimatter were created in equal parts during the Big Bang, it would be conceivable that the visible universe consists of the remaining matter and the black shell of the remaining antimatter. This could be a reason for the observed baryon asymmetry. Since we cannot obtain any information from the black shell, antimatter would not be observable for us. Furthermore, any electromagnetic radiation from any source including the annihilation of matter and antimatter that leaves the visible universe by passing the limit of the Schwarzschild distance into the black shell cannot return to us.