An insight developed by physicists at the University of Auckland has helped shed light on a very early stage in the development of the Universe, providing a missing piece in the understanding of what happened after the Big Bang.

The work, by researchers PhD student Nathan Musoke, research fellow Shaun Hotchkiss, and Professor Richard Easther, looked at the stage sometimes called the primordial dark age.

"We got this moment of insight into how we could work our way through it," Easther said. It was a missing piece in our understanding of what happened after the Big Bang. "We were able to figure out how to describe that process for the first time," he said.

"I have been thinking about this for ages. But once we realised what was going on it took us probably most of a year to fully implement it," Easther said.

READ MORE:

* Scientists are baffled: What's up with the universe?

* New image of the universe by Hubble captures ancient galaxies

* Brilliant blue at universe dawn

"This is one of those nice times when you have a very clearly expressible idea that does actually work."

UNIVERSITY OF AUCKLAND The picture shows the output of one of the Auckland researchers' simulations, showing density variations. Information from the simulations can be used to understand particle processes in the early Universe.

At the start of the primordial dark age, the Universe was about the size of something a person could hold in their hand - although exceedingly heavy.

It was devoid of light and all presently known subatomic particles. As the primordial dark age started, the Universe was filled with a mirror-smooth, cold, ultra-dense quantum condensate.

The stage is thought to have lasted just a trillionth of a second, and during it the Universe grew up to 100 trillion times larger.

The rules governing the Universe during the primordial dark age were not understood, Easther said in a blog post. The quantum condensate at the start of the phase must fragment into familiar particles and radiation, "reheating" the Universe to produce a viable cosmology.

The three researchers showed, in work published in Physical Review Letters, that the process was governed by something called the Schrödinger-Poisson equation, which described the interaction between quantum matter and its own gravitational field, Easther said.

NASA, ESA/Hubble, M. Kornmesser Astronomers have revised their estimate of the number of galaxies in the universe

Using that insight, the researchers performed the first numerical simulations of the collapse of the quantum condensate.

The work should allow cosmologists to better predict the properties of the "ripples" in the early Universe that eventually grew into galaxies, and improve the ability to test theories of the Big Bang.

The primordial dark age is thought to have come after an even briefer period, known as the inflationary phase, which followed the Big Bang.

"The Big Bang is the moment that the Universe begins. What that really means is that's the point at which we can't see back further than," Easther said.

"Time starts and before that there was no time and no space. Whatever there was is anyone's guess. We know there is this singular moment. Everything we can see today came into existence at that moment."

UNIVERSITY OF AUCKLAND Professor Richard Easther

The Universe has grown a trillion trillion trillion trillion trillion times bigger in the 13.8 billion years since the Big Bang. "Everything we can see in the sky today would have been in this tiny dot."

The inflationary stage thought to follow the Big Bang was still hypothetical. "Inflation wipes away whatever was in the Universe to begin with. We know how the early Universe has to look in order to turn into the Universe we see today. Inflation guarantees it looks like that," Easther said.

The inflationary phase maybe lasted a millionth of a trillionth of a trillionth of a second.

Commentary on the Auckland work in the American Physical Society magazine Physics said the results shed light on structure formation in the first stages after inflation.

Inflation produced an extremely homogeneous Universe, but there were fluctuations in density from place to place. Those fluctuations become the seeds of the large-scale structure of today's Universe, the commentary said.

But it was hard to explain the extent of the growth of the initial fluctuations that led to present density variations. The Auckland researchers were able to predict the evolution of small initial quantum fluctuations, and track the evolution of those fluctuations within a self-consistent computation.

"They predict the development of complicated structures with density contrasts that are orders-of-magnitude larger than the initial fluctuations."