Nearly forgotten results in development of physical cosmology

TL;DR

This paper reviews early and often overlooked historical developments in physical cosmology, highlighting contributions from Einstein, Lemaitre, and others that shaped modern understanding of the universe's evolution.

Contribution

It uncovers neglected historical results and emphasizes their significance in the development of cosmological models and the prediction of cosmic background radiation.

Findings

Lemaitre predicted CMB radiation before its discovery.

Friedmann's non-stationary models were historically undervalued.

Early cosmological models laid groundwork for modern inflation theory.

Abstract

It would be reasonable to recall some critical issues in physical cosmology development. GR was created by A. Einstein in 1915. In 1917 Einstein proposed the first (static) cosmological model. Soon after the A. Eddington proved that the model is unstable therefore it can not be realizable in nature. In 1922 and 1924 A. A. Friedmann found non-stationary solutions for cosmological equations written in the framework of GR. In 1927 G. Lemaitre obtained very similar results and, in addition, he derived the Hubble law (E. Hubble obtained this law from observations). Unfortunately, G. Lemaitre published his paper in not very popular Belgium journal. In 1931 Lemaitre proposed the first version of hot Universe model (he called it hypothesis of the primeval atom). In his book Lemaitre predicted even a background radiation as a signature of his model. One of the important property of the Lemaitre -- Gamow model was a prediction of CMB radiation with a temperature around a few K. It was recalled that the discovery of CMB radiation was done by T. Shmaonov in 1956 and his paper was published in 1957 (several years before Penzias and Wilson). In 1965, 1970 E. B. Gliner proposed vacuum like equation of matter which could correspond to exponential explosion of the Universe which was later called inflation. For decades in USSR, Friedmann's cosmological non-stationary models were treated as purely mathematical results without cosmologocal applications. On September 16, 1925 passed away untimely and it would be reasonable to remind today his great contribution in physical cosmology since the authors of book on Friedmann wrote that "similarly to Copernicus who forced the Earth to move Friedmann forced the Universe to expand".