12 thoughts on “Big sim’s – visualizing the universe!”

1. Does the universe have a color?

   Looking at the range of electromagnetic radiation, not just the visible spectrum, “the researchers used a color-matching computer program to convert the cosmic spectrum into a single color visible to humans.”

   • Space.com > “What color is the universe?” by Harry Baker (August 25, 2021) – “Cosmic latte” …

   (quote) In 2002, Baldry [Ivan Baldry, a professor at the Liverpool John Moores University Astrophysics Research Institute in the U.K.] and Karl Glazebrook, a distinguished professor at the Centre for Astrophysics and Supercomputing at the Swinburne University of Technology in Australia, co-led a study published in The Astrophysical Journal that measured the light coming from tens of thousands of galaxies and combined it into a singular spectrum that represented the entire universe.

   In 2002, Australia’s 2dF Galaxy Redshift Survey — which was the largest survey of galaxies ever carried out at the time — captured the visible spectra of more than 200,000 galaxies from across the observable universe. By combining the spectra of all these galaxies, Baldry and Glazebrook’s team was able to create a visible light spectrum that accurately represented the entire universe, known as the cosmic spectrum.

   The team determined that the average color of the universe is a beige shade not too far off from white.

2. Seeing vs. realizing …

   Imagine looking out a window at a tree in the back of your yard. Perhaps taking a picture of the scene. At a later time, perhaps after some years, you look again; and the tree is noticeably farther away. A walking tree? Then sometime later, you notice it’s even farther away. So, you go outside; but, like in a strange dream, no matter how fast you try to reach the tree, you cannot do so.

   Such is the cosmos. The scale of the universe is mind-boggling. Even from what we can observe with ground / space telescopes across the electromagnetic spectrum. Distances elude us: original distances, apparent current distances, actual current distances.

   How far way can another galaxy still be observed? The size of the observable universe. What’s the oldest light than can be detected?

   (quote) From our vantage point, we observe up to 46.1 billion light-years away.

   If we can see it, would a light-speed spacecraft be able to reach it?

   (quote) Beyond distances of ~14.5 billion light-years, space’s expansion pushes galaxies away faster than light can travel.

   (quote) The present “reachability limit” has a boundary ~18 billion light-years away.

   How do these approximate light-year numbers arise: 46.1, 14.5, 18 billion?

   • Big Think > “94% of the universe’s galaxies are permanently beyond our reach” by Ethan Siegel (October 18, 2021) – Even if we traveled at the speed of light, we’d never catch up to these galaxies.

   [photo caption] Distant galaxies, like those found in the Hercules galaxy cluster, are not only redshifted and receding away from us, but their apparent recession speed is accelerating. Many of the most distant galaxies in this image are receding from us at speeds that appear to exceed the speed of light. We will never be able to reach any of the ones presently located more than 18 billion light-years away. (Credit: ESO/INAF-VST/OmegaCAM. Acknowledgement: OmegaCen/Astro-WISE/Kapteyn Institute.)

   • The universe is expanding, with every galaxy beyond the Local Group [that is, those not gravitationally bound to our galaxy] speeding away from us.

   • Today, most of the universe’s galaxies are already receding faster than the speed of light.

   • All galaxies currently beyond 18 billion light-years are forever unreachable by us, no matter how much time passes.

   Terms

   • Redshift
   • Light year
   • Big Bang

3. This is an interesting article regarding cosmological models. As well as an example of Sabine Hossenfelder’s work – since I recently finished reading her 2018 book Lost in Math, which explores (among other things) the role of assumptions in astrophysical theories. So, this is an example of research seeking to move beyond a common simplistic model.

   Namely, the Lambda-CDM [cold dark matter] model. And an application of the Mori-Zwanzig formalism – a method of statistical physics used, e.g., in fluid mechanics! For systems which form a Hilbert space.

   • Phys.org > “Studying cosmic expansion using methods from many-body physics” by University of Münster (December 6, 2021)

   It is almost always assumed in cosmological calculations that there is a even distribution of matter in the universe. This is because the calculations would be much too complicated if the position of every single star were to be included.

   “Strictly speaking, it is mathematically wrong to include the mean value of the universe’s energy density in the equations of general relativity,” says Sabine Hossenfelder. … Some experts consider it to be irrelevant, others see in it the solution to the enigma of dark energy, … An uneven distribution of the mass in the universe may have an effect on the speed of cosmic expansion.

   “The Mori-Zwanzig formalism is already being successfully used in many fields of research, from biophysics to particle physics,” says Raphael Wittkowski, “so it also offered a promising approach to this astrophysical problem.” The team generalized this formalism so that it could be applied to general relativity and, in doing so, derived a model for cosmic expansion while taking into consideration the uneven distribution of matter in the universe.

4. Perhaps a new computational record for cosmic simulations. Modeling the early universe, including dark matter as “the backbone of the cosmos.” Using the Vlasov equation.

   Neutrinos “have an outsize influence on the evolution of structures” – “to weakly influence the behavior [clumping] of dark matter.”

   • Space.com > “Massive simulation of the universe probes mystery of ghostly neutrinos” by Paul Sutter (12-6-2021) – “the universe is a little smoother than it would be without neutrinos.”

   A team of Japanese scientists has built the largest-ever cosmic simulation to include tiny “ghost” particles called neutrinos. To explore one of physics’ biggest unsolved mysteries, the researchers used a whopping 7 million CPU cores to solve for the evolution of 330 billion particles and a computational grid of 400 trillion units.

   If you change the neutrino mass just a bit in the simulations, it will change how the neutrinos influence the formation of structures over billions of years.

5. The grandest of all estimates of size …

   • Space.com > “How big is the universe?” by Nola Taylor Tillman, Jonathan Gordon (January 28, 2022) – “All we can truly conclude is that the universe is much larger than the volume we can directly observe.”

   Thanks to evolving technology, astronomers are able to look back in time to the moments just after the Big Bang. This might seem to imply that the entire universe lies within our view. But the size of the universe depends on a number of things, including its shape and expansion.

   As a result, while we can make estimates as to the size of the universe scientists can’t put a number on it.

   Instead of taking one measurement method, a team of scientists led by Mihran Vardanyan at the University of Oxford did a statistical analysis of all of the results. By using Bayesian model averaging, which focuses on how likely a model is to be correct given the data, rather than asking how well the model itself fits the data. They found that the universe is at least 250 times larger than the observable universe, or at least 7 trillion light-years across.

   Terms

   European Space Agency’s Planck space observatory (2009 to 2013 re CMB map)

   Observable sphere

   Inflation

   Expansion rate

   Bayesian model averaging

   Cosmic curvature

6. A couple of articles on research using cosmic simulations – galaxies and large-scale mass structures.

   • Phys.org > “Observing more disk galaxies than theory allows” by University of Bonn (February 4, 2022) – “… the exact mechanisms of galaxy growth are not yet fully understood …”

   Prof. Dr. Pavel Kroupa of the Helmholtz Institute for Radiation and Nuclear Physics at the University of Bonn … In the current study, Kroupa’s doctoral student, Moritz Haslbauer, led an international research group to investigate the evolution of the universe using the latest supercomputer simulations. The calculations are based on the Standard Model of Cosmology; they show which galaxies should have formed by today if this theory were correct. The researchers then compared their results with what is currently probably the most accurate observational data of the real Universe visible from Earth.

   The situation is different for an alternative to the Standard Model, which dispenses with dark matter. According to the so-called MOND theory (the acronym stands for “MilgrOmiaN Dynamics), galaxies do not grow by merging with each other. Instead, they are formed from rotating gas clouds that become more and more condensed. In a MOND universe, galaxies also grow by absorbing gas from their surroundings. However, mergers of full-grown galaxies are rare in MOND. “Our research group in Bonn and Prague has uniquely developed the methods to do calculations in this alternative theory,” says Kroupa, who is also a member of the Transdisciplinary Research Units “Modeling” and “Matter” at the University of Bonn. “MOND’s predictions are consistent with what we actually see.”

   • Phys.org > “Astronomers trace galaxy flows across 700 million light years” by University of Hawaii at Manoa (February 3, 2022) – “We are bringing into focus the detailed formation history of large-scale mass structures in the universe by reverse engineering the gravitational interactions that created them …”

   In a major new study, a team of astronomers from the University of Hawaiʻi Institute for Astronomy (IfA), University of Maryland and University of Paris-Saclay has traced [simulated] the movement of 10,000 galaxies and clusters of galaxies, the dominant congregations of matter, within 350 million light-years. Their motions are followed throughout a span of 11.5 billion years – from the galaxies’ origins when the universe was only 1.5 billion-years-old, until today, at an age of more than 13 billion years.

   Using a mathematical technique called numerical action method, the team has computed these paths based on the present brightness and positions of galaxies, and their present motion away from us. … Over the eons of time, galaxies typically deviate from pure Hubble rate expansion by millions of light-years over a billion years. In regions of high density, the galaxy orbits can become quite complicated and involve collisions and mergers.

   The technical article [in the Astrophysical Journal] is accompanied by four videos and four interactive models.

   Terms

   … “the Great Attractor,” … the core of the Laniakea Supercluster

   … the adjacent Perseus-Pisces filament of galaxies

7. Another new radio astronomy sky survey – cosmic scale map and computational physics.

   • Phys.org > “Scientists reveal 4.4 million galaxies in a new map” by Durham University (February 25, 2022)

   Durham University astronomer collaborating with a team of international scientists have mapped more than a quarter of the northern sky using the Low Frequency Array (LOFAR), a pan-European radio telescope.

   To produce the map, scientists deployed state-of-the-art data processing algorithms on high performance computers all over Europe to process 3,500 hours of observations that occupy 8 petabytes of disk space – the equivalent to roughly 20,000 laptops.

   This data release, which is by far the largest from the LOFAR Two-metre Sky Survey, presents about a million objects that have never been seen before with any telescope and almost four million objects that are new discoveries at radio wavelengths.

8. This article sketches the basics of cosmic evolution and highlights the interplay of computational physics and observations from current land & space based instruments. Predictions & observational reality. Big science stuff.

   • Scientific American > “New Record-Breaking Simulation Sheds Light on ‘Cosmic Dawn’” by Charles Q. Choi (May 10, 2022) – A computer model of the universe’s first billion years is helping set expectations for observations from NASA’s James Webb Space Telescope.

   Image caption: Evolution of simulated properties in the main Thesan run. Time progresses from left to right. The dark matter (top panel) collapse in the cosmic web structure, composed of clumps (haloes) connected by filaments, and the gas (second panel from the top) follows, collapsing to create galaxies. These produce ionizing photons that drive cosmic reionization (third panel from the top), heating up the gas in the process (bottom panel). Credit: Courtesy of THESAN Simulations [named after the Etruscan goddess of the dawn] (CC BY-NC-ND 3.0)

   THESAN is designed to simulate the early universe to an unprecedented extent. Some cosmological simulations, such as the Cosmic Dawn (CoDa) simulations and the Cosmic Reionization on Computers (CROC) project, have modeled large volumes at relatively low resolutions, while others, such as the Renaissance and SPHINX simulations, are more detailed but do not span great distances. In contrast, THESAN “combines high resolution with large simulated volumes,” Kannan says.

   THESAN can track the birth and evolution of hundreds of thousands of galaxies within a cubic volume spanning more than 300 million light-years across. Starting from circa 400,000 years after the big bang—before the first stars are thought to have emerged—the simulation extrapolates out through the first billion years of cosmic history.

   One drawback of THESAN … is that it uses a relatively simplistic model for the cold dense gas in galaxies … [which will be upgraded in a follow-on project].

   The scientists are currently planning to scale up the simulation to a volume 64 times larger … .

   “… even though THESAN is quite high-resolution, it’s still low-resolution, compared to the physical processes actually happening,” Wechsler [Risa Wechsler, cosmologist, Stanford University and director of the Kavli Institute for Particle Astrophysics and Cosmology] says.

   Terms

   The Big Bang

   cosmic fog
   plasma
   era of recombination
   neutral hydrogen
   epoch of reionization (ionizing photons)
   cosmic dawn
   cosmic dust

   Related posts

   • The physics, the math – evolution of computational physics

   

9. Here’s a visualization of how galactic clusters form.

   • NASA > APOD > “Simulation TNG50: A Galaxy Cluster Forms” (May 29, 2022)

   [Description]

   Video Credit: IllustrisTNG Project; Visualization: Dylan Nelson (Max Planck Institute for Astrophysics) et al.

   Music: Symphony No. 5 (Ludwig van Beethoven), via YouTube Audio Library

   Explanation: How do clusters of galaxies form? Since our universe moves too slowly to watch, faster-moving computer simulations are created to help find out.

   A recent effort is TNG50 from IllustrisTNG, an upgrade of the famous Illustris Simulation.

   The first part of the featured video tracks cosmic gas (mostly hydrogen) as it evolves into galaxies and galaxy clusters from the early universe to today, with brighter colors marking faster moving gas.

   As the universe matures, gas falls into gravitational wells, galaxies forms, galaxies spin, galaxies collide and merge, all while black holes form in galaxy centers and expel surrounding gas at high speeds.

   The second half of the video switches to tracking stars, showing a galaxy cluster coming together complete with tidal tails and stellar streams.

   The outflow from black holes in TNG50 is surprisingly complex, and details are being compared with our real universe.

   Studying how gas coalesced in the early universe helps humanity better understand how our Earth, Sun, and Solar System originally formed.

   • YouTube > APOD Videos > “Simulation TNG50: A Galaxy Cluster Forms”

   

10. Here’s an article on a cosmic simulation (which required 100,000 hours of computation) from the Institute of Astrophysics of the Canary Islands (IAC).

    • Space.com > “New simulation charts how the early universe developed within seconds of the Big Bang” by Elizabeth Howell (June 6, 2022) – A new simulation maps the first few seconds after the Big Bang, focusing on what scientists call the intergalactic medium, or the gas and dust between galaxies.

    [Image caption] A simulation of a galaxy cluster forming and evolving. (Image credit: Claudio Dalla Vecchia)

    This new work allowed researchers to chart phenomena including dark matter, energized gas, neutral hydrogen and other cosmic ingredients that are essential to understanding the structure of our universe, IAC representatives said in a May 20 statement.

    

11. 

    So, as portrayed in the movie “Cowboys and aliens,” gold is indeed rare in the Milky Way [1]; and new galactic simulations conclude that “most gold-rich stars formed in small progenitor galaxies of the Milky Way over 10 billion years ago.”

    • Phys.org > “Research unveils birthplace of gold-rich stars” by Royal Astronomical Society (November 14, 2022) – A new simulation analyzed the formation of gold-rich stars in our Milky Way for the first time.

    The simulation was produced over several months using the ATERUI II supercomputer in the Center for Computational Science at the National Astronomical Observatory of Japan.

    The simulation data revealed that some of the progenitor galaxies … contained large amounts of the heaviest elements. Each event of neutron star merger – a confirmed site of heavy element nucleosynthesis – increased the abundance of the heaviest elements in these small galaxies. The gold-rich stars formed in these [dwarf] galaxies, and their predicted abundances can be compared with the observations of the stars today.

    The research appears as “Neutron star mergers as the astrophysical site of the r-process in the Milky Way and its satellite galaxies,” published in Monthly Notices of the Royal Astronomical Society.

    Notes

    [1] The aliens are mining gold in 1873 New Mexico Territory …

    • Scripts.com > Cowboys and Aliens

    What are they [the aliens] doing here?
    They want gold.
    Well, that’s just ridiculous.
    What are they gonna do,
    buy something?
    It’s as rare to them as it is to you.

    Related posts (and comments)

    • The Milky Way’s shape – regarding, in particular, ‘fossil’ records of galactic evolution, Gaia mission data, …

12. 
    [video thumbnail caption] Dome master down-sampled to 2k, 180 degree view, monoscopic. Meant to be viewed in a full-dome digital planetarium. … Shows the evolution of the universe from shortly after the Big Bang to the present day, in gas temperature (blue: cold, green/orange: warm, red/white: hot). Credit: Illustris Collaboration.

    As noted in my June 8, 2022, comment above, this recent APOD cites the famous Illustris Simulation, which exhausted 20 million CPU hours in 2014.

    • APOD > “Illustris: A Simulation of the Universe” (Dec 31, 2023) > YouTube > Illustris Simulation (May 11, 2014)

    (caption)
    Illustris: A Simulation of the Universe

    Video Credit: Illustris Collaboration, NASA, PRACE, XSEDE, MIT, Harvard CfA

    Music: The Poisoned Princess (Media Right Productions)

    Explanation: How did we get here? Click play, sit back, and watch.

    A computer simulation of the evolution of the universe provides insight into how galaxies formed and perspectives into humanity’s place in the universe.

    The Illustris project exhausted 20 million CPU hours in 2014 following 12 billion resolution elements spanning a cube 35 million light years on a side as it evolved over 13 billion years.

    The simulation tracks matter into the formation of a wide variety of galaxy types. As the virtual universe evolves, some of the matter expanding with the universe soon gravitationally condenses to form filaments, galaxies, and clusters of galaxies.

    The featured video takes the perspective of a virtual camera circling part of this changing universe, first showing the evolution of dark matter, then hydrogen gas coded by temperature (0:45), then heavy elements such as helium and carbon (1:30), and then back to dark matter (2:07).

    On the lower left the time since the Big Bang is listed, while on the lower right the type of matter being shown is listed.

    Explosions (0:50) depict galaxy-center supermassive black holes expelling bubbles of hot gas.

    Interesting discrepancies between Illustris and the real universe have been studied, including why the simulation produced an overabundance of old stars.

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