A paper published in The European Physical Journal H provided the first English translation and an analysis of one of Albert Einstein’s little-known papers, “On the cosmological problem of the general theory of relativity.” Published in 1931, it features a forgotten model of the universe, while refuting Einstein’s own earlier static model of 1917. In this paper, Einstein introduces a cosmic model in which the universe undergoes an expansion followed by a contraction. This interpretation contrasts with the monotonically expanding universe of the widely known Einstein-de Sitter model of 1932.
Einstein was keen to investigate whether a relativistic model could account for the new observations, by removing the so-called cosmological constant introduced in his 1917 cosmological model. Einstein sets the constant to zero. He then arrives at a model of a universe that first expands and then contracts. This model is also characterised by singularity-like behaviour at either end.
In this paper, the authors also discuss Einstein’s view of issues such as the curvature of space and the timespan of the expansion, while also uncovering some anomalies in Einstein’s calculations. For example, they highlight a numerical error in the calculation of the present radius and matter density of the universe. They also believe that Einstein’s estimate of the age of the universe is based on a questionable calculation of Friedmann’s analysis of a relativistic universe of spherical curvature and time-varying radius. Finally, they argue that Einstein’s model is not periodic, contrary to what is often claimed.
The image at the top of the page shows Seyfert's Sextet that is actually only four interacting galaxies, though. Near the center of this Hubble Space Telescope picture, the small face-on spiral galaxy lies in the distant background and appears only by chance aligned with the main group. Also, the prominent condensation on the upper left is likely not a separate galaxy at all, but a tidal tail of stars flung out by the galaxies' gravitational interactions. About 190 million light-years away, the interacting galaxies are tightly packed into a region around 100,000 light-years across, comparable to the size of our own Milky Way galaxy, making this one of the densest known galaxy groups. The group may coalesce into a single large galaxy over the next few billion years.
Source: C. O’Raifeartaigh and B. McCann (2014), Einstein’s cosmic model of 1931 revisited, European Physical Journal H, DOI 10.1140/epjh/e2013-40038-x
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Image credit: apod.nasa.gov