Skip to main content

How our universe grew up

  • Scientists have released a new model of how the universe might have evolved
  • The simulation begins 12 million years after the Big Bang
  • It represents more than 41,000 galaxies
  • Dark matter is the 'backbone of the cosmic web'

(CNN) -- It's hard to describe billions of years of cosmic history. But scientists have used a code to create a model of how the universe as we know it today might have evolved.

A new study in the journal Nature describes a simulation of the universe that is unique because of "how realistically it recreates the galaxies and the universe that we see, which is kind of a first for a simulation like this," said Dylan Nelson, study co-author at the Harvard-Smithsonian Center for Astrophysics.

Nelson and collaborators released several videos this week showcasing highlights of what their numerical simulation, called Illustris, can do.

Running this model "took approximately 16 million CPU (central processing unit) hours," Michael Boylan-Kolchin, astronomer at the University of Maryland, College Park, wrote in an accompanying article in Nature. "The end result, however, is a simulated Universe that looks an awful lot like the real one."

This simulation begins 12 million years after the Big Bang, which is still pretty early considering that the universe is about 13.8 billion years old.

"What it allows -- a statistically robust comparison against observations across all of cosmic time -- is a critical aspect in the development of better and more realistic models, which directly translates into more physical insight which we can extract from such simulations," Nelson said.

A range of galaxy types emerges in this simulation, such as blue spiral and red elliptical galaxies. The content of hydrogen and elements heavier than hydrogen and helium seems consistent with observational data, study authors wrote.

"These observations capture a large variety of galaxy luminosities, sizes, colours, morphologies and evolutionary stages, providing remarkable benchmarks for galaxy formation theories," study authors wrote.

A total of 41,416 galaxies are represented in the simulation. It includes a population of elliptical galaxies that don't form stars, disk galaxies that do form stars, and irregular galaxies.

Our own Milky Way galaxy is a disk galaxy, and simulating how such a galaxy would be formed has been problematic in the past. But the scientists' calculations have overcome this, the study said.

The simulation takes into account that there are phenomena in our universe that we have never detected but that have had huge influence on cosmic evolution. Dark matter accounts for about 24% of the universe, while normal matter -- everything that we can see -- is only 4.6%.

Dark matter "dominates the gravitational pull of everything, especially on large scales," Nelson said. "It's the backbone of the cosmic web."

Over the course of the universe's history, galaxies have formed where dark matter was most concentrated.

But most of the universe is made of dark energy, responsible for the accelerating expansion of the universe.

The universe is expanding, but how quickly?

Obviously, you can't model the entire universe at once, but this simulation does represent a substantial chunk of it: 350 million light years in each dimension, Nelson said. It allows scientists to zoom in to see the structure of individual galaxies, such as spiral arms.

Still, there are shortcomings to the simulation: For instance, the mass of stars in low-mass galaxies gets built up earlier than what has been observed, meaning that populations of stars are shown as two to three times older than in reality.

Joel Primack, professor of physics and director of the High-Performance Astro Computing Center in Santa Cruz, California, takes issue with the idea that this new simulation is better than its predecessors.

"Other groups are doing a much better job of understanding what's going on inside galaxies, including my own group," said Primack, whose team also works on modeling the cosmos.

But the simulation does have strengths on a larger scale -- for instance, in showing how galaxies affect their surrounding environments, and how environments impact galaxies, he said.

The code used in the simulation, Arepo, is not publicly available -- another of Primack's criticisms. But Nelson said that a complete description of its methods has been published, and that anyone with expertise who is motivated could use it to develop a similar code.

Part of complete coverage on
Science news
August 25, 2014 -- Updated 1934 GMT (0334 HKT)
Nichelle Nichols has spent her whole life going where no one has gone before, and at 81 she's still as sassy and straight-talking as you'd expect from an interstellar explorer.
July 22, 2014 -- Updated 1152 GMT (1952 HKT)
The world's largest flying aquatic insect, with huge, nightmarish pincers, has been discovered in China's Sichuan province.
June 23, 2014 -- Updated 1210 GMT (2010 HKT)
As fans of "Grey's Anatomy," "ER" and any other hospital-based show can tell you, emergency-room doctors are fighting against time.
May 29, 2014 -- Updated 1159 GMT (1959 HKT)
Ask 100 robotics scientists why they're inspired to create modern-day automatons and you may get 100 different answers.
June 13, 2014 -- Updated 1635 GMT (0035 HKT)
From the air, the Namibian desert looks like it has a bad case of chicken pox.
May 28, 2014 -- Updated 1643 GMT (0043 HKT)
The trend for nature-inspired designs has spread across industries from crab-style deep-sea vessels to insect-inspired buildings.
May 25, 2014 -- Updated 1222 GMT (2022 HKT)
Consider it the taxonomist's equivalent of a People magazine's Most Beautiful List.
May 9, 2014 -- Updated 1532 GMT (2332 HKT)
For the first time, scientists have shown it is possible to alter the biological alphabet and still have a living organism that passes on the genetic information.
May 5, 2014 -- Updated 1148 GMT (1948 HKT)
Do we really want to go the route of "Jurassic Park"?
May 2, 2014 -- Updated 1244 GMT (2044 HKT)
Catch a train from the sky! Perhaps in the future, the high-rise superstructures could help revolutionize the way we travel.
May 5, 2014 -- Updated 1458 GMT (2258 HKT)
In a nondescript hotel ballroom last month at the South by Southwest Interactive festival, Andras Forgacs offered a rare glimpse at the sci-fi future of food.
March 20, 2014 -- Updated 1412 GMT (2212 HKT)
For a Tyrannosaurus rex looking for a snack, nothing might have tasted quite like the "chicken from hell."
March 14, 2014 -- Updated 2229 GMT (0629 HKT)
Everyone is familiar with Tyrannosaurus rex, but humanity is only now meeting its much smaller Arctic cousin.
March 6, 2014 -- Updated 1712 GMT (0112 HKT)
At about 33 feet long, weighing 4 to 5 tons and baring large blade-shaped teeth, the dinosaur Torvosaurus gurneyi was a formidable creature.
February 21, 2014 -- Updated 1143 GMT (1943 HKT)
This Pachyrhinosaurus can go to the head of its class.
March 27, 2014 -- Updated 1204 GMT (2004 HKT)
Science is still trying to work out how exactly we reason through moral problems, and how we judge others on the morality of their actions. But patterns are emerging.
February 28, 2014 -- Updated 0006 GMT (0806 HKT)
A promising way to stop a deadly disease, or an uncomfortable step toward what one leading ethicist called eugenics?
February 15, 2014 -- Updated 0107 GMT (0907 HKT)
Seattle paleontologists safely removed the largest fossilized mammoth tusk discovered in the region from a construction site.
April 23, 2013 -- Updated 1013 GMT (1813 HKT)
A mysterious, circular structure, with a diameter greater than the length of a Boeing 747 jet, has been discovered submerged about 30 feet underneath the Sea of Galilee in Israel.
January 17, 2014 -- Updated 2225 GMT (0625 HKT)
Every corner of the planet offers some sort of natural peculiarity with an explanation that makes us wish we'd studied harder in junior high Earth science class.
November 14, 2013 -- Updated 1320 GMT (2120 HKT)
Deep in a remote, hot, dry patch of northwestern Australia lies one of the earliest detectable signs of life on the planet, tracing back nearly 3.5 billion years, scientists say.
September 4, 2013 -- Updated 1910 GMT (0310 HKT)
We leave genetic traces of ourselves wherever we go -- in a strand of hair left on the subway or in saliva on the side of a glass at a cafe.