Harvard, Bonn Researchers Discover Potential Discrepancies in Assumption of Isotropy

Researchers at Harvard and the University of Bonn published a study April 7 casting possible doubt upon the longstanding assumption that the universe is isotropic.

Isotropy is the principle that the universe has the same structure and is growing evenly in all directions; it forms the basis for many theories regarding the properties of the universe.

Gerrit Schellenberger, a researcher at the Harvard-Smithsonian Center for Astrophysics and co-author of the study, wrote in an email that his team’s work focused on attempting to verify this principle using new technologies.

“We always have to keep in mind what fundamental assumptions we rely on in cosmology,” Schellenberger wrote. “New observatories, methods and discoveries are a good moment to take a step back and perform tests to ensure whether we can still safely rely on these assumptions.”

The study compared direct measurements of the luminosity of galaxy clusters to calculations of their luminosity from the clusters’ gas temperatures. The luminosity of a cluster is linked to how far away the cluster is.

Schellenberger wrote that inconsistencies in the two different measurements of luminosity suggest possible anti-isotropic behaviors — though interference by other materials in the universe may also have provided incorrect distance and luminosity calculations.

“For a specific region in the sky, clusters seem to have on average a higher luminosity than predicted from their temperature, and for another region a lower one,” Schellenberger wrote. “The discrepancy cannot be explained by statistical fluctuation. One possible explanation for this discrepancy is that toward those two regions the universe expands differently than with respect to the average cosmic expansion across the sky.”

Konstantinos Migkas, a researcher at the Argelander Institute for Astronomy and another co-author of the study, said in a press release that disproving isotropy could lead to new discoveries about dark energy, a mysterious phenomenon known to accelerate the expansion of the universe.

"If we succeed in developing such a theory, it could greatly accelerate the search for the exact nature of this form of energy," Migkas said.

Schellenberger wrote that expounding upon this study to discover new information about dark energy would lend scientists an increased overall understanding of the properties of the universe.

“If we can confirm this finding with further studies, and also exclude all other explanations, this would have a big impact on our understanding of the universe,” Schellenberger wrote. “Dark energy was established as the driving force for the accelerated expansion of the universe. However, we still have little knowledge about the nature of this form of energy.”

—Staff writer Ethan Lee can be reached at ethan.lee@thecrimson.com.