The universe is expanding and will continue to do so until it is a cold and seemingly empty void. As best as we can tell, this is the destination of all existence—the “where.” But the “why” and the “how” are still somewhat of a mystery to cosmologists, and a new 3D map of the known universe spanning nearly two billion light years could help solve these puzzles.
Edwin Hubble discovered that the universe was expanding in 1929 based on redshift observations of distant stars—the further away a star is, the wavelength of light changes. Holding everything else constant, redshift observations painted a picture of a steadily expanding universe. In the 90s, Hubble’s theory was forwarded by better redshift observations that suggested a universe that was expanding faster and faster.
But the story doesn’t end there. New observations have suggested that the universe isn’t as uniform as we thought, and that it’s expanding more slowly than once calculated. These deviations from the “Hubble flow” are called peculiar velocities, and we’re just beginning to investigate them. To that end, astrophysicists at the University of Waterloo constructed a comprehensive 3D map of the universe using predictions from the 2M++ redshift catalogue.
“The galaxy distribution isn’t uniform and has no pattern,” said Michael Hudson, a professor in the department of physics and astronomy at the University of Waterloo, in a statement. “It has peaks and valleys much like a mountain range.”
Tracking the uneven expansion of celestial bodies will be key for investigating not just peculiar velocities, but also the location and amount of dark matter in the universe. Dark matter is thought to make up 26.8 percent of our universe, and yet we can’t see it. It doesn’t interact with normal matter, and so we can only observe it based on its interactions with other objects that we can detect. A comprehensive model of the universe would allow researchers to better predict where dark matter lies in the void.
But, if you’re not an astrophysicist, you can always just enjoy a peek at what the universe would look like if it was sliced in half like a melon.