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 new 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 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."
“The field of cosmology these days is converging on a standard model, centred around inflation and the Big Bang,” says physicist Arjun Berera at the University of Edinburgh, UK. “This is why it’s as important as ever, before we get too comfortable, to see if there are alternative explanations consistent with all known observation.”
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.
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.nAfter observing that most galaxies exhibit a red shift that became greater for more distant galaxies, they theorised 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 colours 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.
But, reports Nature.com, the one huge problem wih Wetterich's theory is that it can't be tested. Mass is what’s known as a dimensional quantity, and can be measured only relative to something else. For instance, every mass on Earth is ultimately determined relative to a kilogram standard that sits in a vault on the outskirts of Paris, at the International Bureau of Weights and Measures. If the mass of everything — including the official kilogramme — has been growing proportionally over time, there could be no way to find out.
Wetterich says that his interpretation could be useful for thinking about different cosmological models, in the same way that physicists use different interpretations of quantum mechanics that are all mathematically consistent. In particular, Wetterich says, the lack of a Big Bang singularity is a major advantage.