New Measurements Confirm That the Universe Is Boring

As citizens of Earth, we don't get much perspective on the universe. For us, the universe is weird (or novel) from every angle. If we were to travel from coordinate to coordinate within even our more far-reaching dreams of deep space exploration, we would find each point quite different in nature. Even if we were to remain at our original point and just look out in different directions, we would find every view quite different.

That's our intuition about space—that it's so large and so incredible as to be essentially unknowable. But it's quite incorrect once applied to the universe as a whole. The universe, all evidence suggests, is a very plain place.

At universal scales, two properties are preserved in the universe: homogeneity and isotropy. The first of those means that the universe is about the same at any point. Isotropy means that if we were to look in different directions from any point, what we'd see would be about the same. No special places, no special directions.

Existence is distinctly not special, at cosmological scales. And this lack of being special is something subject to regular experiment and observation, with the most recent results coming from the University of Colorado's Jeremy Darling, who found that everything contained within everything is indeed flying outward into the True Void (not a technical term) with startling isotropic uniformity.

These properties were proposed by Einstein, or rather by his equations, which, when correctly solved later on by the mathematician Alexander Friedmann, demanded universal expansion. Einstein's solution for a universe that didn't collapse in on itself (thanks to the combined gravity of existence pulling inward, terminally) was a fudge called the cosmological constant, just some number that made things right.

When everything was set straight, with help from Edwin Hubble's red-shift observations, that number turned out to correspond to the field energy needed to keep the universe stable—and stability in the cosmos means expansion. A static universe is one that collapses. A key result of all of this (a couple steps from Einstein himself) is the notion that the universe should be homogeneous and isotropic: boring.

Whether or not this is actually "boring" is a matter of perspective. Isotropy and homogeneity are statistical concepts involving the universe at very large scales, by definition, and something like averaging. In an isotropic universe, galaxies and other very large cosmic structures aren't really spread evenly through space. It's the opposite, in fact: galaxies are clustered in very peculiar ways.

But, we can keep moving outward even further from galaxies and galaxy clusters, to the point where there really isn't a bigger structure possible. It's at this scale that we can see the universe lose its contrasts and become a great big smear of stuff. That smear is what you'd find evenly distributed in an isotropic universe: no center, no real "regions." It's just a droplet of reality expanding into the Real Void—yet here we are, thinking about it.

Everything in cosmology is quite a bit more strange now, what with quantum physics, the effects of dark matter and energy, and the theory of inflation. But the principle should hold, well, in principle.

There are theories, however, to the contrary, that involve alternate notions of dark energy. If dark energy is not spread isotropically, we might imagine universal expansion accelerating more or less in different places, and this would certainly have effects on universal plainness. Some portions of the cosmos would be pulled harder and faster outward more than others, with anisotropic results.

Somewhat conversely, making determinations on the universe's homogeneity and isotropy should give clues as to what exactly the hell is going on with dark energy, the great cosmic blank driving all of this accelerating expansion in the very first place. (Probably.) Finding some irregularity in space would then indicate something new about the ways of dark energy. As an isotropic and homogeneous universe suggests plainness about the "light" universe, it suggests the very same about dark energy as well.

Darling's new data comes from observations of 429 objects traveling through space under the watchful radio-eye(s) of the Very Long Baseline Array, a series of 10 radio observatories spread across the United States and a bit beyond, from Hawaii to the Virgin Islands. The mission of the Array is observing motion among stellar bodies with a very high degree of precision, and that's just what's needed to make these sorts of measurements.

Darling found isotropy "to 7 percent" using this batch of objects, which eliminates models of dark energy involving what are known as broken symmetries. Broken symmetry is a dense concept among dense concepts, but Darling explains it well.

"Instead of thinking about dark energy distributions, think about dark energy as a property of nature or space," he said via email. "Some aspects of nature are nice and symmetric. Liquid water, for example. It has no favored direction. But freeze the water, and crystals form, breaking the symmetry and showing favored directions.

"The simplest form of [dark energy] has symmetry," he continued. "It has no favored direction, so the accelerating expansion of the universe, the acceleration is caused by dark energy, is isotropic. Were [dark energy] to show a broken symmetry, it might drive acceleration more in one direction than another, causing an anisotropic expansion."

So, Darling's confirmation of isotropy, up to 7 percent, means about the same thing for dark energy, albeit in terms of symmetry. Though he cautions that some models for dark energy involve quite small broken symmetries, small enough to slip under the current 7 percent margin.

The next task is narrowing that margin further, eliminating more broken symmetry possibilities and adding yet more support to the old Cosmological Principle. This will be achieved through the Gaia mission, a European Space Agency project tasked with 3D mapping the Milky Way with the highest levels of precision yet achieved, charting the motions of some 500,000 quasars. This, according to Darling's paper, should allow researchers to claim universal isotropy to under 1 percent (or eliminate its opposite, anisotropy, to that degree).