The thought of existing in a void probably brings to mind some sort of eternal doom that involves forever hurtling through a lightless chasm haunted by a million silent screams. That’s just your imagination—but we do live in a void.
Cosmic voids are everywhere, and the Milky Way happens to be floating in one. The visible matter that makes up 5 percent of the universe either appears as filaments, or clusters and superclusters of galaxies, and voids, the vacant lots of space with far fewer galaxies and celestial objects. Our galaxy is like one of the lone cars rusting away on that gaping expanse of asphalt. Just forget the dark matter and dark energy that supposedly make up the other 95 percent for now.
Not only are we living and breathing in a spherical void surrounded by galaxies and stars, but with a radius of 1 billion light-years, our void, aka the KBC void, is the most immense abandoned parking lot in space.
While that might sound apocalyptic, the results of a new study from the University of Wisconsin-Madison recently presented at a meeting of the American Astronomical Society have confirmed not only that do we exist in a cosmic void, but that this means less tension over measurements of the Hubble Constant, or the unit that describes the rate at which the universe expands. Astrophysicists have been at odds with each other in the past because of the variance in Hubble Constant measurements arrived at from different techniques. Matter outside a void exerts slightly more gravitational pull, which affects the Hubble Constant value if you get to it using a method involving nearby supernovae, but not if you use the cosmic microwave background (CMB) to arrive at a result.
“No matter what technique you use, you should get the same value for the expansion rate of the universe today,” explained Ben Hoscheit, the Wisconson undergrad whose analysis has backed up past research, proved there are no observational obstacles to confirming we do live in a void, and prevented more potential astrophysical arguments. “Fortunately, living in a void helps resolve this tension.”
Supernovae have been used to measure the Hubble Constant because of their blazing light. Wherever these epic explosions occur, they always do with the same amount of energy, which is why scientists often rely on this method for an accurate measurement. Some, however, prefer to use the CMB because it reveals the homogeneous nature of the embryonic universe. This primordial ocean of photons and subatomic particles was relatively consistent in temperature. It is the tiny inconsistences in the CMB—those dips in temperature that come from areas less saturated with stars and galaxies—that bring the Hubble Constant to light.
Meaning, however sci-fi it sounds, existing in a void that can determine the expansion of the universe is actually kind of mind-blowing.