Uchuu, the most accurate and complete simulation of the universe that allows you to 'time travel'

An international team of researchers not only created an entire virtual universe. It also made it available free of charge to everyone with internet access.

Uchuu, a term meaning universe in Japanese, is the most realistic simulation of the cosmos ever made.

The project was developed by the National Astronomical Observatory of Japan (NAOJ) in collaboration with the Andaluca Institute of Astrophysics (IAA-CSIC), the Galicia Supercomputacin Center (Cesga) and the academic and academic network. Spanish research RedIRIS.

Other research groups from Japan, USA, Argentina, Australia, Chile, France and Italy are also participating in the initiative.

The simulation will allow us to study the evolution of the universe with an unprecedented level of detail and information, practically from after the Big Bang to the present.

“Uchuu basically aims to recreate how the universe was formed, the whole structure, everything we’ve seen since the universe was just in its infancy and was 400 a thousand years old,” said cosmologist Francisco Prada, professor at the Superior Council of research uisa Cientfica da España from the Andalusian Astrophysics Institute BBC News Mundo.

“We managed, with a supercomputer intensely dedicated to the project, to recreate all the physics involved, basically all the gravity equations of Einstein and the energetic and material components of the universe, as well as all the processes involved numerically.”

The simulation, which is already available in the Cesga cloud, will allow scientists to focus on different moments in the history of the universe and facilitate the understanding of phenomena such as the evolution of galaxies and the formation of black holes.


The simulation was made possible by the ATERUI II supercomputer, the most powerful computer dedicated exclusively to astrophysics, which belongs to the National Astronomical Observatory of Japan.

“Other large computers like the Mare Nostrum in Barcelona may have many more processors. But the advantage is that he is dedicated to few projects in astrophysics” ATERUI, says Prada.

“And this allows you to have exclusive use for a long time to be able to do a simulation like This one, which otherwise would be impossible. We were lucky to use ATERUI for a whole year 48 hours every month exclusively. It’s a huge privilege.”

Tomoaki Ishiyama, from Chiba University in Japan, was responsible for the development and execution of what created the simulation code.

The result “is three petabytes of data, the equivalent of nearly 1 million photos from a megapixel mobile phone,” said Ishiyama, according to agency Efe.

The simulation consists of 2.1 billion particles in a virtual cube 9.6 billion light-years across, a dimension comparable to half the distance that exists between the Earth and the most distant galaxies observed, says the CSIC.

All data for analysis are stored at CESGA, a mixed center of the CSIC and the Junta de Galicia, and may also be downloaded online via the IAA server.

Galaxy Evolution

Uchuu will allow scientists to study in detail different moments and scenarios of the history of the universe, over more than billions of years.

“For the first time we can study in the same simulation both very small objects and huge objects, both galaxies with masses smaller than our Milky Way and clusters of very large galaxies, or even huge voids, maintaining the same resolution. This had not been possible yet in the same simulation.”

” as if in another simulation you could only study cars. But with our simulation we were able to study from a skateboard to an airplane or a supertanker, and we could also see how all these objects are distributed either on a plain or in the Himalayas or in the ocean waters, in very different environments of density of matter.”

“The galaxies of the universe are distributed in what we call a large-scale structure: there are large voids, where there are very few galaxies, there are filaments, there are groups like the Milky Way and Andromeda and then there are large objects that are a thousand times more massive than our own Milky Way. “

The simulation allows us to see, for example, how small galaxies aggregate (merge) throughout history and form larger ones, something called the hierarchical formation of the structure of the universe, explains Prada.

“This is how the Milky Way was formed. It has been ‘eating’ many tiny objects and this is part of the history of the formation of the galaxy.”

The simulation would also allow to study the collision of two galaxies that have very massive black holes that can produce gravitational waves.

“Massive galaxies like the Milky Way have a black hole. It is essential to understand the growth of these structures because it also has to do with the rate of increase in matter of black holes, how they form.”

‘dark matter glasses’

A key feature about the Uchuu is that it embodies not only visible matter, but also the mysterious dark matter and dark energy.

Ordinary matter, composed of atoms, represents less than 5% of the total energy of the universe.

Dark matter, a form of matter that does not interact with light and is only detectable by its gravitational effects, represents about 25%. The rest, 48%, what scientists call dark energy.

In the Uchuu view available on YouTube, for example, you can see dark matter and how it is distributed in a super massive object, such as a large galaxy.

“Our simulation has all the ingredients, all the parameters we know today in the right proportions,” said Prada.

Uchuu images are equivalent to “putting on special glasses” to visualize dark matter.

“There was a moment in the history of the universe when gravity had to compete with dark energy because, if you had just gravity, all matter collapsing would start to come in.”

“However, there comes a moment in the history of the universe where this dark energy begins to dominate that we don’t know what it is, but we know in practical terms that it’s like a repulsive force, like a pressure against gravity,” explained Prada to BBC News Mundo.

“One of the big challenges for Uchuu is that for having simulated the entire structure of the universe and being able to compare all the statistics we observe, for example, how many large clusters of galaxies we have, how many large voids, such as the galaxies are grouped together , we will be able to better interpret the nature of dark energy and dark matter, which to this day we do not know what .”

“It is understood that dark matter It’s an elementary particle, but we don’t know what it is. And dark energy has no idea of ​​it, it’s understood that the universe is expanding at the later time quickly, but we don’t know what causes this accelerated expansion.”

Francisco Prada explains: “This image shows four moments in the history of the universe, the present is below and the past is above. And the three columns correspond to different regions of the universe.”

“For example, the one on the right is very interesting because it shows the process of formation of a large void.”

“If we go to the present, you will see that the density of galaxies there is very low, there are large regions that have a deficit, a vacuum of galaxies, so we can go back in time and how it was formed see.”

“In the first column you see an object similar to the Milky Way; as if we put glasses up in the sky and saw dark matter.”

“If instead I give you a picture of what can only be seen by the telescope, it would be a beautiful galaxy like Hubble images, but we see all of the dark matter, because in our own galaxy there must be thousands of small objects that are dark matter.”

“And in the middle you see one a cluster of galaxies than an object a thousand times more massive.”

From Argentina and Chile

The scientist Sofa Alejandra Cora, from the Institute of Astrophysics of La Plata, Argentina, is also part of the Uchuu project.

She is an independent researcher at the National Council for Scientific and Technical Research (Conicet) and associate professor from the Faculty of Astronomical and Geophysical Sciences of the National University of La Plata.

“The main objective of my participation in this project is to generate a catalog of galaxies from the data from the Uchuu simulation, which considers only dark matter.”

“To do this, information about the properties of dark matter halos and the way they grow and fuse over time is taken as a basis,” she explained BBC News Mundo.

“It is an applied semi-analytical model of galaxy formation and evolution, taking into account several physical processes that determine the properties of galaxies,” he continued.

“A semi-analytical model consists of a set of simple analytical recipes that model different physical processes that affect the gas and stars that make up a galaxy.”

“The latest version of the model used by our working group in Argentina is described in an article in the Montlhy Notices of the Royal Astronomical Society. This task is under development.”

Cristian Vega Martnez, researcher at the Department of Astronomy and the Institute for Multidisciplinary Research in Science and Technology at the University of La Serena (ULS), in Chile , also participates in the project.

“One of Uchuu’s greatest challenges was to manage and publish the large amount of data that a simulation of this category can produce.”

“This type of simulation can easily generate hundreds of terabytes,” said Vega BBC News Mundo.

“Therefore, we are actively working to design the techniques for manipulate this data, provide a direct way to share it, and provide tools for its use.”

He contributes his experience in the area of ​​galaxy formation and evolution simulations, and his knowledge of high-throughput computing.

“Published data must be provided in a way that can be useful to the community,” he says.

“Simulations of this type, that allow you to model large volumes of the universe , are necessary to be able to contrast our physical theories of the formation of galaxies and the evolution of the universe, with the results of large modern experiments [telescópios]”.

‘Give access to other people’

For Francisco Prada, one of the main reasons for the importance of Uchuu is its free availability.

” As a scientist, I believe in the responsibility of giving access to other scientists who do not have the possibility of doing these simulations so that they can do high-level, state-of-the-art science,” he said.

“We make it public for all scientists in the world, and not just for scientists, but also for all people who have internet.”

“And in Galcia we have it too. data, so people can log in and analyze the data without having to download it at home. That’s why we also make the computer capacity available, because this computer capacity is not normally available to anyone.”

The simulation, analysis and public dissemination of the data were financed by public institutions in Japan and in Spain.

“The cost of this project is very high and there are few groups in the world that can do this project.”

” We are in the Big Data era, where what Uchuu generated much more than the amount of data stored by YouTube, Amazon and Google together.”

“We were really able to make the search available for free cutting edge for society and scientists, which I find very encouraging.”

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