Cosmologists created 4,000 universes to solve the mystery of the Big Bang

Using a supercomputer we can peer into the origins of the universe!

A team of cosmologists are trying to rewind time to the first instant after the Big Bang by simulating 4,000 versions of the universe on a massive supercomputer.


The goal is to paint a picture of the immediate aftermath of the Big Bang, when the observable universe suddenly expanded 1 trillion trillion times in size in the smallest strip of a microsecond. By applying the method used for the simulations to actual observations of the current universe, the researchers hope to arrive at an accurate understanding of what this inflationary period was like.


Masato Shirasaki, a cosmologist at the National Astronomical Observatory of Japan (NAOJ), said in a statement:


"We are trying to do something like guess a baby photo of our universe from the last image."


Irregular universe


The current universe shows variations in density, with some areas rich in galaxies and others relatively arid. A promising hypothesis for this uneven distribution of visible matter is that, at the time of the Big Bang, there were already quantum fluctuations, or random temporal changes of energy, in the tiny primordial universe, Shirasaki said.


Diagram of the evolution of the universe from inflation (left) to the present (right). The reconstruction method backs up evolution from right to left in this illustration to reproduce the primordial density fluctuations of the current distribution of galaxies. Image: The Institute of Statistical Mathematics



When the universe expanded, these fluctuations would have expanded as well, with denser points spreading out into regions of higher density than their surroundings. Gravitational forces would have interacted with these stretched filaments, causing galaxies to cluster along them.


But gravitational interactions are complex, so trying to rewind this inflationary period to understand what the universe would have looked like before it is a huge challenge. Cosmologists essentially need to remove gravitational fluctuations from the equation.


A clean start

The researchers developed a reconstruction method to do just that. However, to know if the reconstruction was accurate, they needed some way to test it. So they used NAOJ's ATERUI II supercomputer to create 4,000 versions of the universe, all with slightly different initial density fluctuations.


The researchers allowed these virtual universes to undergo their own virtual inflations and then applied the reconstruction method to them to see if it could return them to their original starting points.


The results, published Jan. 4 in the journal Physical Review D , were promising.


Shirasaki said:


"We found that a reconstruction method can reduce gravitational effects on observed galaxy distributions, allowing us to extract information from the initial conditions of our universe in an efficient way."


The reconstruction has been applied to real-world galaxy data before, he added, but the new study shows that it can also work in the inflationary period of the universe. The next step, Shirasaki said, is to apply the reconstruction to actual observations of the cosmic web . Those observations have already been made by a telescope in New Mexico as part of the Sloan Digital Sky Survey.


The research findings have been published in the journal Physical Review D.


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