What Expands in an Expanding Universe?

Abstract

In the present investigation, the possible effects of the expansion of the Universe on systems bonded either by gravitational or electromagnetic forces, are reconsidered. It will be shown that the acceleration (positive or negative) of the expanding background, is the determinant factor affecting planetary orbits and atomic sizes. In the presently accepted cosmology (ΛCDM) all bonded systems are expanding at a decreasing rate that tends to be zero as the universe enters in a de Sitter phase. It is worth mentioning that the estimated expansion rates are rather small and they can be neglected for all practical purposes.

How Fast Is the Distance between Earth and Sun Changing in the Solar System?

“…(1 + 3 ) ( ̈ ) Equation 11 (Pacheco 2015) showed that equation ( 6) shows that the main factor of expansion effects on the local system's orbit is the acceleration of the expansion with agreement from the previous conclusion (Sereno and Jetzer 2007). Pacheco generally agreed that the expansion rates are relatively low and can be neglected for all practical purposes.…”

“…They concluded that planetary orbits are expanding, but the orbital properties' effects depend on the expansion's acceleration rather than on the expansion itself. (Pacheco 2015) re-studied the possible effects of the expansion on bonded systems. Expansion effects are unnoticeable so that they can be neglected in atomic and solar system scales.…”