This is the universe at present. You’re seeing not the light but the dark — you knew that most of the universe’s matter is dark, right? — and its motions. Not until the far right end are you seeing the light. Go ahead and clickety click all over this; zoom it in and out, drag it around. It’s a computer simulation based on and ending with observed reality. But it doesn’t read from left to right; it’s less the chronology of the universe’s life than a series of its aspects. It’s so beautiful you might faint.
The universe is a foam of blank bubbles surrounded by skins of matter. The matter in the skins is mostly dark. Nobody knows what the dark matter really is – some kind of particle. But dark matter feels gravity and so it’s pulled, and so it moves. This is a simulation of that motion: the gravity of the matter in the skins is pulling the dark particles; they’re streaming away from blank voids, their streamlines meeting other streamlines and forming a running foam, a network of walls. The streamlines and walls look bright but they’re made of dark matter so they’re not shining; think of them instead as fast and dense. It’s a map of gravity and motion.
Within those walls are more filaments of dark matter, also flowing toward and meeting other filaments, on smaller and smaller scales. They feel each others’ gravity, they pile up on top of each other, forming a finer and finer fractal foam. Streaming away from the voids, they make the voids bigger. You see this happening not so well in this picture but better in the picture at the top of the post — in the first five frames that are set below the picture, like a predella below a painting.
The young scientists who are the simulators have taken out the dark matter’s motion. What you see clearly now are the walls and filaments that have pulled the dark matter out of the voids and into themselves. The finer and finer filaments have gotten richer, and the poor voids are poorer. Gravity being what it is — utterly relentless — it has concentrated some of the dark matter into dense ridges and some into little spots, into ridges and peaks of density.
The simulators have put the motions back in, so you can see how the dark matter is emptying out of voids and falling into those ridges and peaks. In fact, those streamlines show the whole history of those particles’ motion, getting redder as they approach the present. I’m not confident that I understand this picture. But you can almost feel the pull into the knots and nodes. And the matter has emptied the voids to such an extent that the universe begins to look divided into nothingness and something.
The simulators have taken the motions back out again. This is the foamy pattern of dark matter that cosmologists call the universe’s structure, the cosmic web: huge, yawning voids; and the fuzz of dark matter still falling into filaments and piling up into ridges of density, into density peaks like cities and small towns. You’d think you were in an airplane looking down, but you’re not, you’re on this planet looking up. This is how the static universe really looks.
But all we see of it is this. This is real data; they’re real superclusters, real clusters, real galaxies. They’re made of regular matter, which is a small trace of all matter and which has all along been traveling with the dark. It has collected into atoms and eventually into stars, so it shines. It looks like bright little islands poised on nets of mountain ranges invisible under the dark water.
It looks lonely. No, it doesn’t. It looks like it’s full of courage and faith in the endless dark mountains that are its foundation.
I first saw the picture — a kind of moving poster — at the top of the post because it won first place in Science magazine’s 2011 International Science & Engineering Visualization Challenge and was on the magazine’s cover. Here’s the journal paper explaining it all.
The picture was made by Miguel Angel Aragón-Calvo, with the help of Julieta Aguilera and Mark SubbaRao of the Adler Planetarium. It is used here with their kind permission. Aragón-Calvo is at Johns Hopkins University as an assistant research scientist. He’s job-hunting. Wish him luck.