Conventional thinking has it that the universe and all the matter within it exploded out from a single point, the so-called Big Bang Singularity. But a German theoretical physicists says this never happened. Instead, the universe started empty and cold, slowly emerging from a deep freeze.
This isn't the first time a physicist has challenged the standard Big Bang model of cosmology by positing a Big Freeze sort of explanation. Back in 2012, scientists from the University of Melbourne and RMIT University argued that the early universe went through a dramatic transformation, or phase shift, in a manner similar to how a solid turns to a liquid.
But Heidelberg University's Christof Wetterich's theory is a bit different, and it's one that dovetails nicely off an earlier theory of his — the suggestion that the Universe is not expanding, it's just getting fat.
In his latest paper, Heidelberg says the universe sprung from a very cold and slowly evolving universe. Over the course of cosmic timescales, the masses of elementary particles slowly increased while the gravitational constant decreased. At the same time, Newtonian attraction remained unchanged. The result is what he's dubbing a simple three-parameter "crossover model" without a Big Bang Singularity.
Writing in Science News, Gabriel Popkin explains more:
This logic leads to a cosmic history in which the universe still underwent inflation but did not necessarily continue expanding. And instead of starting with a Big Bang, time before inflation could stretch into the infinite past.
No measurement can prove whether particle masses have stayed constant because it is only possible to measure the ratio between different masses, not masses themselves. For instance, all masses on Earth are ultimately referenced to a standard kilogram sitting in a vault in France. So Wetterich's picture is akin to saying that instead of the universe expanding, the ruler with which we measure it is shrinking, says Niayesh Afshordi, an astrophysicist at the Perimeter Institute of Theoretical Physics in Waterloo, Canada.
If particle masses have been increasing, radiation from the early universe would make it look hotter than it actually was, and distant objects would appear to be receding even if they aren't. This would explain why the universe appears to be expanding. So Wetterich says cosmic origin theories do not need to pack all matter into one point before inflation, avoiding a singularity. The universe could have begun sparse and cold, emerging from this deep freeze only after an unimaginably long time. In this picture, he says, "you can go as far back in the past as you want, and the past is even pretty boring."
Interestingly, Wetterich says that finding non-vanishing early dark energy or the large neutrino lumps of growing neutrino quintessence may offer evidence for his theory.
"A cosmological model with no more free parameters than the [Big Bang cosmological model] is highly predictive," he concludes in his paper (which appears at the pre-print archive arXiv). "It poses a challenge to observers: falsify it, if you can!"
Top image: NASA.