The most widely accepted theory of the universe is based on the notion that the world started with a big bang, and has been expanding ever since. But, in a radical counter view, the Universe in not expanding according to a Christof Wetterich, a theoretical physicist at the University of Heidelberg in Germany who has devised a different cosmology in which the Universe is not expanding but posits that the mass of everything has been increasing. His theory could help physicists to understand problematic issues such as the so-called singularity present at the Big Bang.

In his 2013 paper: A Universe Without Expansion, Wettrich discusses a cosmological model "where the universe shrinks rather than expands during the radiation and matter dominated periods". In his abstract of his paper published on the arXiv preprint server, he writes: "Only dimensionless ratios as the distance between galaxies divided by the atom radius are observable. The cosmological increase of this ratio can also be attributed to shrinking atoms."

Cosmologists envisage the Universe as expanding, says Niayesh Afshordi, an astrophysicist at the Perimeter Institute in Waterloo, Canada, only because it is the most convenient interpretation of galaxies' redshift. The extremely distant galaxy A1689-zD1 shown above appears on this picture as the elongated reddish object; its light has been magnified by a factor of more than 9 by the massive gravitational lensing effect of the galaxy cluster Abell 1689. Astronomers were surprised to discover a far more evolved system than expected. It had a fraction of dust similar to a very mature galaxy, such as the Milky Way, which dust is vital to life, because it helps form planets, complex molecules and normal stars. (J. Richard / ESO).

In the 1920s, astronomers including Georges Lemaître and Edwin Hubble analysed the light emitted or absorbed by atoms, which appeared in a spectrum of characteristic colours, or frequencies. When matter moved away, they discovered that galaxies exhibited a shift to the red, lower frequency part of the spectrum. After observing that most galaxies exhibit a red shift that became greater for more distant galaxies, they theorized that the universe was expanding. The Hubble image at the top of the page shows a gravitationally lensed image of the highest known redshift galaxy.

However, Wetterich highlights that this light emitted by atoms is also determined by masses of the elementary particles, and in particular, their electrons.If the mass of an atom increases, it emits more energetic photons. If the particles were to become lighter, frequencies would become redshifted.

In Nature News, Jon Cartwright explains: “Because the speed of light is finite, when we look at distant galaxies we are looking backwards in time — seeing them as they would have been when they emitted the light that we observe. If all masses were once lower, and had been constantly increasing, the colors of old galaxies would look redshifted in comparison to current frequencies, and the amount of redshift would be proportionate to their distances from Earth. Thus, the redshift would make galaxies seem to be receding even if they were not.”

In Wetterich's alternative interpretation of redshift all of cosmology looks very different: The Universe still expands rapidly during a short-lived period known as inflation. But prior to inflation the Big Bang no longer contains a 'singularity' where the density of the Universe would be infinite. Instead, the Big Bang stretches out in the past over an essentially infinite period of time. “The current cosmos could be static or even beginning to contract,” he adds.