Most of the universe is void, containing not much matter and very few galaxies. |
This is a thin slice through a simulation that calculates the evolution of dark matter particles under gravity as the universe expands. The big, colorful points are void particles, with different colors representing different voids; these are plotted over little black points of wall, filament, and halo particles that represent the collapsed structures in the universe. The voids, instead of collapsing to form stuff (i.e. galaxies form in the dark matter halos), are regions of space that matter flows away from because they are less dense than their surroundings.
It turns out that voids occupy most of the volume of the universe, perhaps around 90%, while only containing perhaps 30% of the mass. These numbers depend on the physics of structure formation, including whether Einstein's general relativity theory is correct on large scales. But they also depend on how you define a void and so could change depending on whom you ask on what day of the week. Researchers in my field are slowly converging on the best ways of defining voids in both simulations of dark matter and observations of galaxies.
So if you are wondering what I do, now you know: I study the large-scale structure of the universe, and I make art.
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