Introduction

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Hi everyone! Once again we are going to talk about space and physics. I promise this this the last one.....*crosses fingers. In this article we are going to be researching and talking about the visualization aspects of dark matter and energy. If you haven't read my quantum theory articles or the article on atomic physics I highly recommend you read those before diving into this one. A lot of the concepts are the same, and I think it is great to discuss this subject matter with a good solid understanding of the physics behind it. 

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You can read the quantum theory article HERE, the sequel article HERE, and the atomic physics article HERE. And if you're feeling really enthusiastic you can check out my article on the visualization of theory of randomness HERE. Now...Onto some space stuff. 

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What is Dark Matter?

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Dark matter is somewhat of a mystery. 27% of our universe we cannot directly observe, or capture through observation. This is a bit of a pain for astrophysicists, as we can't fully understand the universe if we can't see all of it.  Scientists have discovered that there is a large chunk of that dark section that emits no light or energy. This section is what they describe as dark matter.

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Everything in the universe moves at a high velocity. But the bigger the object, the harder it is for gravity to keep things together. So what stops a galaxy from collapsing inwards from it's own energy? Astrophysicists suspect that dark matter is the glue or extra matter holding these collections of stars and dust together.  The bigger the mass, the stronger the glue.

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But what exactly is dark matter made of? The best guess that anyone has is that it is made up of unknown exotic particles. As dark matter particles do not interact with light, regular forms of spectrometry don't detect them. Instead, scientists look for indications how this unseen matter is interacting with regular matter with something called weak nuclear force. This nuclear force is one of the four fundamental forces in the universe and helps produce radioactive decay. By observing regular matter and how it reacts to different particles in different conditions, they can rule out which particles dark matter is made of.

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Another technique scientists are using to find dark matter particles is seeing if dark matter is affecting the spins of electrons. With all matter, the higher the temperature, the more active the electrons become. The cooler the temperature, less movement will be apparent. Considering that dark matter makes up 80% of our universe, it must have some interaction with all matter in some way, regardless of temperature. These hypothetical electron moving particles are called Magnons. They fit under a sub-class of particles called quasi-particles. 

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One last way physicists have been trying to measure dark matter is through observation of the polarization and distortion of light in the universe. In this theory, it operates on the idea that dark matter particles exist in super-cold states and are clumped together about the universe. Because he matter is clumped together so tightly, I could possibly change the oscillation of light as it passes through the mass. The bigger the mass, the bigger the polarization of light. 

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Unfortunately for us, most of these studies have come back empty handed. So..Dark matter is currently impossible to detect.

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Visualizing Dark Matter

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There are a few different ways scientists visualize dark matter. Let's talk about them. 

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 Some of the best scientific tools astrophysicists have at their disposal are space telescopes. Such as the Hubble Space Telescope. However, no current one exists in space for studying dark matter. As of 2022 that issue will be solved. The European Space Agency is developing a telescope called Euclid that will be able to view the distortion of light that dark matter creates. It will then visualize those discoveries through infrared detectors. It will help answer some of the greater questions of the universe. Such as: How is the structure in the Universe formed under the influence of gravity? Or: How is all matter distributed in the Universe?

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One thing we can do here on Earth is create simulations of datasets. A few scientists are already creating their own simulations to demonstrate how dark matter fits into the bigger picture.

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Physicist Miguel Angel Aragon-Calvo and his team at John Hopkins University are one of these groups of people.  In early 2012, they created a visualization of the universe and it's interaction with dark matter. In their rendered images they were to show 240 million light years of space from five different vantage points. In this perspective they were able to show the history of matter, and what a galaxy looks like from different atomic levels. Including our favorite dark space glue.

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A group of researchers later in 2012 were the next to use simulations to forward the research of dark matter. Cornell University published a paper that pushes the use of 3D simulation art as the best way to achieve models for astrophysics. Ralf Kaehler, Oliver Hahn, and Tom Abel are pushing for the use of time-dependent particle based simulations. These would help forward the visualization of spatial distributions and kernel interpolation. They propose these simulations would not only calculate particle movements, but handle and create tetrahedral shapes, meshes, and abstract structures like sheets, filaments and halos. All of these structures would be needed to simulate dark matter and its surrounding universe.

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What is Dark Energy?

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Dark energy is the name of the energy that is causing our universe to expand. Our universe constantly grows bigger every second, and it is pushed forward by unseen forces. Dark energy makes up about 68% of the known universe. It is also a huge factor in the affecting forces of visible matter as well.(Visible matter makes up for about 5% of our universe.)

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The confusing aspect of dark energy is that scientists have concluded that at the start of the universe, or The Big Bang; there was hardly any of it. In 1998, the Hubble telescope was able to observe the movement of older galaxies and prove that the universe was moving slower than it is today. So what happened? And what is causing the expansion of our universe to speed up, and more dark energy to be created?

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Energy is considered a fundamental property of the universe. It cannot be created or destroyed, but it has to come from something. Empty space is not nothing.  It is filled with unseen particles that form the dark energy that we know and love. Albert Einstein was first to propose that the expansion of the universe might be caused by a cycle of growth. This growth would be based off the idea that the universe contains a cosmological constant value. The more space equals the more space containing energy, which equals more dark energy and more growth. This constant value would then be multiplied upon again and again; forever. And so on. This is the most agreed upon theory, but it is still unconfirmed.

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Another theory on what dark energy is, is that it might be made of a new kind of dynamical energy fluid or field. This fluid would fill all of space, and has the opposite effect and energy of visible matter and normal energy. Scientists call this fluid Quintessence but they still have yet to prove if it exists and how it interacts with regular matter.

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Visualizing Dark Energy

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Out of the two types of "dark"materials, dark energy seems to be the less loved one of the two. Not much in terms of visualization has been achieved with dark energy. But there are some different ways scientists are trying to display it.

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There is something called The Cosmic Web that astrophysicists use to describe universal connections. As we've mentioned before that space isn't empty. It is filled with interconnecting filaments that form structures that hold galaxies together, or rather the universe. Everything has its place, and these filaments make it so. They are mostly made of dark matter, but they also help matter pull together through gravity and form clusters. These clusters can be stars, galaxies, nebulae, etc. There is an order to their connections as well. Galaxies average a distance of 500 light years from each other, and usually keep this distance because of the dark matter filaments connecting them. 

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This is where dark energy enters in the cosmic web. Because it funds the expansion of the universe, it also scatters these filaments apart, and weakens the force of gravity between material bonds. Fewer and more spread across clumps of dark matter mean a less likely-hood of matter clumping together to form star clusters. Therefore, huge voids were created in the expanding universe and discrepancies in matter densities were created. 

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There is a 3D interactive model of The Cosmic Web you can view HERE. Bruno Coutinho and his team at The National Optical Astronomy Observatory (NOAO), the Radcliffe Institute for Advanced Study and the Institute for Theory and Computation at Harvard University have done an amazing job showcasing the universe. 

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There are other ideas out there that The Higgs Boson might be one of the founding particles of dark energy, and by modeling it's behavior we'll be able to have a better insight into how dark energy works. However, no such answers have been found yet.

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There is also a group called The Dark Energy Survey that is currently using their time and resources to cataloging and visualizing dark energy. They have been using Spectroscopic Instruments to measure amounts of dark energy. These instruments are scattered about the globe at three different locations. Also during this endeavor they are trying to create the largest 3D map of galaxies in the universe. So far they have discovered over 1 billion new galaxies, and completed over three sky surveys.

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Hydrodynamic Visualization

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Hydrodynamics is a branch of physics that deals with the motion of fluids and gases. It is also used to describe the motion of fluids in their environments. Depending on the flow rate, pressure, speed, and other factors; different types of fluid flows can be created. As well as formulas for these flow types. Hydrodynamics and fluid dynamics seems a bit weird to bring up in a quantum physics article, but stick with me. This gets really cool.

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Hydrodynamics is starting to be used to map electron movements and their interactions with other electrons. Electrons carry a spatial structure that can be mapped out through particle fluid movements. Their actions can also be easily replicated through experiments with electrified currents.

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This digs up the question...Can hydrodynamics be used to replicate different particle interactions other than electrons? Yes. They can also replicate particle structures flowing through open surfaces under large amounts of pressure. For example, clouds. If you've ever looked up at the sky on a windy day and seen turbulent fast moving clouds, that would be an example of a hydrodynamic simulation in progress.

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Hydrodynamic visualization is being used in mechanical, hydraulic, and other aerospace industries. More recently it has been used to help map out large scale structures of galaxies, and dark matter.

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Using different fluids, scientists can mimic and create the orbital speeds of galaxies as they would appear in a liquid or a gas. This liquid represents the vacuum of space and it's web. By creating a low scale simulation of a larger object; in this case a galaxy, they can understand the universe better. By even playing with the viscosity of the gases or liquids, scientists can also add factors based on equations into the simulation. Such as the Schrödinger equation which plays a huge part in quantum physics. These equations can help change the results of the flows to create densities inside the liquid which would represent where dark matter or regular matter would form in the universe.

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Application In VFX

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As we've seen, simulations are a huge part in understanding the universe. As well as a key part of observing how dark energy and dark matter affect us. But what more can we do to help this field?

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We could try and replicate hydrodynamic simulations in 3D space. There are plenty of tools out there that can create particle fluids with easily controlled variables. Houdini for example has huge capabilities when it comes to simulating particles and advecting them by volumes, filaments, textures, or collisions. It also can support ocean and flip tank simulations. It also has tabs on solvers to change viscosity, stickiness, separation and particle size.

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We could also try and replicate other simulations NASA is using to mimic dark matter. They have released that they have been observing slime mold growth as a way to create universal structures. Based on data and images from these simulations we could replicate them in 3D space. They resemble grey-scott patterns and other forms of growth equations. You can check out the NASA article HERE.

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Lastly, there are a few other simulations that we could try and replicate. The University of Minnesota released the very first simulation of a red giant star just a few years ago. This simulation was able to take controlled glimpses into a red giant from different angles, and simulation the dying process of the star. (HERE) Or we could try and replicate other simulations such as the Caltech Milky Way  simulation from 2016 (HERE). They were able to produce this result on one of their supercomputers which took 700,000 central processing unit (CPU) hours.  By learning how to replicate these simulations we can not only learn how to build these simulations better and faster, but also outsource our skills to something beyond VFX.  If you've ever wanted to work for NASA, this could be your shot. 

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Additional Datasets

 

Here are some additional datasets and values that you can play around with inside Houdini, or your chosen VFX software. Have fun!

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• Dark Matter Data Analysis: Signal & Background Models, and Statistical Inference Data: HERE

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• COMBO-17 galaxy dataset: HERE

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• Shapley galaxy dataset: HERE

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• Hipparcos star dataset: HERE

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• SDSS quasar dataset: HERE

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• Extrasolar planet radial velocities: HERE

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• Galaxy spectra: HERE

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• The Dark Energy Survey Datasets: HERE

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References

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DARK MATTER AND SUPER SYMMETRY: EXPLORING AND EXPLAINING THE UNIVERSE WITH SIMULATIONS AT THE LHC: https://dl.acm.org/doi/epdf/10.5555/3042094.3042102

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Volume Rendering Dark Matter Simulations Using Cell Projection andOrder-Independent Transparency: https://dl.acm.org/doi/epdf/10.1145/3002151.3002163

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Modeling Early Galaxies Using Radiation Hydrodynamics: https://dl.acm.org/doi/epdf/10.1145/2148600.2148674

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Inverted Indices for Particle Tracking  in Petascale Cosmological Simulations: https://dl.acm.org/doi/epdf/10.1145/2484838.2484882

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First-Ever Full Observable Universe Simulation: https://dl.acm.org/doi/epdf/10.5555/2388996.2389096

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Cosmic Simulations: https://dl.acm.org/doi/epdf/10.1145/2240236.2240241

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Astrophysical N-body simulations using hierarchical tree data structures: https://dl.acm.org/doi/epdf/10.5555/147877.148090

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Dark matter: https://home.cern/science/physics/dark-matter

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Dark Energy, Dark Matter: https://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy

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Dark Matter and Dark Energy: https://www.nationalgeographic.com/science/space/dark-matter/

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VISUALIZING DARK MATTER: https://www.darkmatterday.com/visualizing-dark-matter/

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"Dark Matters" - Incredible Simulations of an Invisible Universe: https://www.kavlifoundation.org/science-spotlights/kipac-dark-matters-how-scientists-are-visualizing-invisible#.Xu4NLmhKiUk

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GPU-BASED INTERACTIVE VISUALIZATION OF BILLION POINT COSMOLOGICAL SIMULATIONS: http://tamas-szalay.squarespace.com/dark-matter

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New phase space tracking method to visualize dark matter simulations: http://tomabel.org/Home/Visualization/Pages/Dark_Matter_visualizations.html

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You Don't Need To Modify Gravity To Explain Dark Energy: https://www.forbes.com/sites/startswithabang/2020/01/28/you-dont-need-to-modify-gravity-to-explain-dark-energy/#28e62d7165e1

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This Is Why Dark Energy Is The Biggest Unsolved Problem In The Universe: https://www.forbes.com/sites/startswithabang/2019/11/05/this-is-why-dark-energy-is-the-biggest-unsolved-problem-in-the-universe/#328635c84165

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A Mind-Melting Visualization Of The Universe’s Invisible Forces: https://www.fastcompany.com/1669213/a-mind-melting-visualization-of-the-universe-s-invisible-forces

 

Data visualization could reveal nature of the universe: https://phys.org/news/2019-06-visualization-reveal-nature-universe.html

 

Dark Matter: https://kipac.stanford.edu/research/dark-matter

 

No Dark Energy? No Chance, Cosmologists Contend:https://www.quantamagazine.org/no-dark-energy-no-chance-cosmologists-contend-20191217/

 

Dark matter & dark energy (Part 2) – Understanding the nature of dark matter and dark energy: https://astroedu.iau.org/en/activities/1748/dark-matter-dark-energy-part-2-understanding-the-nature-of-dark-matter-and-dark-energy/

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