The largest virtual universe ever simulated

June 9, 2017
The Cosmic Web: A section of the virtual universe, a billion light years across, showing how dark matter is distributed in space, with dark matter halos the yellow clumps, interconnected by dark filaments. Cosmic void, shown as the white areas, are the lowest density regions in the universe. Credit: Joachim Stadel, UZH

Researchers from the University of Zurich have simulated the formation of our entire universe with a large supercomputer. A gigantic catalogue of about 25 billion virtual galaxies has been generated from 2 trillion digital particles. This catalogue is being used to calibrate the experiments on board the Euclid satellite, that will be launched in 2020 with the objective of investigating the nature of dark matter and dark energy.

Over a period of three years, a group of astrophysicists from the University of Zurich has developed and optimised a revolutionary code to describe with unprecedented accuracy the dynamics of dark and the formation of large-scale structures in the universe. As Joachim Stadel, Douglas Potter and Romain Teyssier report in their recently published paper, the code (called PKDGRAV3) has been designed to use optimally the available memory and processing power of modern supercomputing architectures, such as the "Piz Daint" supercomputer of the Swiss National Computing Center (CSCS). The code was executed on this world-leading machine for only 80 hours, and generated a virtual universe of two trillion (i.e., two thousand billion or 2 x 1012) macro-particles representing the dark matter fluid, from which a catalogue of 25 billion virtual was extracted.

Studying the composition of the dark universe

Thanks to the high precision of their calculation, featuring a dark matter fluid evolving under its own gravity, the researchers have simulated the formation of small concentration of matter, called , in which we believe galaxies like the Milky Way form. The challenge of this simulation was to model galaxies as small as one tenth of the Milky Way, in a volume as large as our entire observable universe. This was the requirement set by the European Euclid mission, whose main objective is to explore the dark side of the universe.

Measuring subtle distortions

Indeed, about 95 percent of the universe is dark. The cosmos consists of 23 percent of dark matter and 72 percent of dark energy. "The nature of dark energy remains one of the main unsolved puzzles in modern science," says Romain Teyssier, UZH professor for computational astrophysics. A puzzle that can be cracked only through indirect observation: When the Euclid satellite will capture the light of billions of galaxies in large areas of the sky, astronomers will measure very subtle distortions that arise from the deflection of light of these background galaxies by a foreground, invisible distribution of mass – . "That is comparable to the distortion of light by a somewhat uneven glass pane," says Joachim Stadel from the Institute for Computational Science of the UZH.

Optimizing observation strategies of the satellite

This new virtual galaxy catalogue will help optimize the observational strategy of the Euclid experiment and minimize various sources of error, before the satellite embarks on its six-year data collecting mission in 2020. "Euclid will perform a tomographic map of our , tracing back in time more than 10-billion-year of evolution in the cosmos," Stadel says. From the Euclid data, researchers will obtain new information on the nature of this mysterious , but also hope to discover new physics beyond the standard model, such as a modified version of general relativity or a new type of particle.

Explore further: NASA delivers detectors for ESA's Euclid spacecraft

More information: Douglas Potter et al. PKDGRAV3: beyond trillion particle cosmological simulations for the next era of galaxy surveys, Computational Astrophysics and Cosmology (2017). DOI: 10.1186/s40668-017-0021-1

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18 comments

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zave
4.3 / 5 (6) Jun 09, 2017
I would like to know how long it will before this is implemented into a game like no man's sky?
SRDUB2
3.7 / 5 (3) Jun 09, 2017
When will we be introducing gooble boxes to the inhabitants?

geku
5 / 5 (3) Jun 09, 2017
I would like to know how long it will before this is implemented into a game like no man's sky?

probably never, because if you will zoom in - there is really no 'spiral galaxy' or 'black hole' there, just particles that simulate ordinary matter\ dark matter. you need different kind of simulator if you wish to be able to fly\run inside simulated universe.
Molecular hydrogen
2.3 / 5 (6) Jun 09, 2017
Ok so is this a good baises to input existing known elements that could be candidates for dark matter and see which one behaves in the same manner as dark matter ... my money is on molecular Hydrogen which is virtually impossible to detect.
cantdrive85
2.2 / 5 (17) Jun 09, 2017
Another grand exercise in GIGO from the plasma ignoramuses. Just keep in mind that the filamentary and cellular nature of the Universe was predicted by Alfvén way back in the 1930's and his prediction doesn't require any faerie dust whatsoever, just the known properties of plasma and the EM forces that drive it.
Captain Stumpy
4 / 5 (12) Jun 09, 2017
@cd the nazi sympathizing anti-vaxx idiot pseudoscience cult fanatic
from the plasma ignoramuses
so where is your viable theory?
don't have one?

more to the point, why can't you take up the challenge i issued here: https://phys.org/...ers.html

i will tell you why: you're a liar, fraud and a religious fanatic
you keep repeating the same blatantly false lie without any evidence
that is called a "faith" in the real world
that also means you're argument is one from faith, not evidence
that makes you a religious fanatic, not a "science" anything

JaxGTO
5 / 5 (2) Jun 09, 2017
Is it just me or does that look like a lot of the electron microscope pictures of the brain?
Da Schneib
5 / 5 (1) Jun 10, 2017
Why is it that the position of the Milky Way is only shown in less than half of these images?
IMP-9
5 / 5 (4) Jun 11, 2017
The Milky Way isn't shown because simulations like this aren't trying to reproduce the local universe, there is no Milky Way. Usually they simulate a volume according to standard cosmology using random initial perturbations. They don't intend to reproduce the Universe just a universe which is statistically consistent with observations. You could select things out of the simulation which are comparable in some way to the Milky Way say in a group of 2 large members or near a Virgo cluster analogue but it wouldn't be the same down to the last detail. Secondly this simulation is dark matter only, as dark matter only simulations are far simpler than when you include baryons they can be made much larger. So there aren't really any galaxies at all in the simulation, just dark matter halos.
antialias_physorg
3 / 5 (4) Jun 11, 2017
Is it just me or does that look like a lot of the electron microscope pictures of the brain?

It's a pattern you get anywhere where two forces act on a medium (in the case of the universe gravity and radiation pressure, in the case of the brain surface tension vs.expression of proteins/availability of nutrients)
Dingbone
Jun 12, 2017
This comment has been removed by a moderator.
antialias_physorg
3 / 5 (2) Jun 12, 2017
I would like to know how long it will before this is implemented into a game like no man's sky?

probably never, because if you will zoom in - there is really no 'spiral galaxy' or 'black hole' there, just particles that simulate ordinary matter\ dark matter. you need different kind of simulator if you wish to be able to fly\run inside simulated universe.

At - on average - roughly 1000 particles making up a 'galaxy halo' in this simulation that would be a very coarse setting. Consider that the Milky way has somewhere around 600 billion solar systems - each with planets and whatnot.

If you want something on that scale play "Elite Dangerous". (Zooming through the galaxy map near the center is mind-boggeling. It really drives it home what "600 billion" really means...and how far out in the boonies we really are.)
Bart_A
2.1 / 5 (7) Jun 12, 2017
So let me get this right.

They simulated a virtual universe of dark matter fluid, something that only exists in fantasy today, to try to understand what a real universe and real observations mean.

Are these scientists crazed or what?

Da Schneib
not rated yet Jun 12, 2017
Thanks, @IMP. I guess I should have figured that out a little quicker.
antialias_physorg
5 / 5 (3) Jun 12, 2017
They simulated a virtual universe of dark matter fluid, something that only exists in fantasy today, to try to understand what a real universe and real observations mean.

The point of such a simulation is to find out whether, with our knowledge of how dark matter behaves (as derived from galactic rotational curves and lensing): Would this form structures like the ones we observe?

If no: Then our ideas about dark matter are wrong.
If yes: Then our ideas about dark matter may be correct.

Turns out that it does result in similar structures so this gives some confidence that dark matter is real.

(And why do people balk at the idea of non-interacting matter so much? We know of neutrinos which behave almost the same and no one is all up in arms with cries of: "neutrinos aren't real!")
Kweden
1 / 5 (1) Jun 12, 2017
Leave's me wondering which form of known energy was used as existing first for the algorithms of the program; was it heat, gravity, or light?
You see, they teach, elementarily, that particles were pushed together by light drive, until they come together enough to create gravity, then when there is enough particles stuck together the gravity becomes so great that it explodes causing a star. Where did that light come from that started the particles being driven together?
Or, the entire universe was so hot that nothing could form, but it was only for an instant. Where did that heat come from?
Or, they say gravity pulled all the substance together till it went BANG! Can gravity explode itself according to any current physics?
So, what would cause a hole in space--a spot of gravity so great that it would be so massive that everything would be flung out of it, in one way or another, so that nothing was there--except maybe gravity? Well,if gravity can explode, it can fling itself
Merrit
not rated yet Jun 15, 2017
I think part of the confusion is our understanding of black holes. The mass needed to make it impossible for light to escape is some value simular to the value any phase transition. The mass at the center is going to be very similar to a neutron star that doesn't have enough mass to be a BH, just more massive and more dense. There is no reason to believe BH such as the one at the center of our galaxy is a point mass. It would take an infinite amount of mass to become a point likewise it would take an infinite amount of thrust to accelerate a mass to lightspeed. You can get really close, but you can never reach it. My hypothesis is that a BH with enough mass would eventually become unstable and this is what would lead to the big bang.
Merrit
not rated yet Jun 15, 2017
I would not put much weight behind this simulation. We know virtually nothing about the physical characteristics of DM if it even exists in the first place. The basic assumptions used in the model to create this simulation could be way off. This sounds more religious than significant.

Models and simulations should only be used on something we already understand very well and want to know how some change or modification will affect the whole. This article is basically scientists patting their own backs.

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