The debate over the speed of our universe’s expansion continues, as new measurements reportedly confirm earlier controversial results indicating a faster rate than theoretical models predict.
The findings lend new weight to the longstanding cosmological quarrel involving what astronomers call the “Hubble tension,” challenging our current understanding of physics and pointing to flaws in models that have long haunted physicists.
At the heart of the debate are the ongoing discrepancies between current physics models and actual observational data about the universe. The new challenging findings, published in The Astrophysical Journal Letters, offer some of the most substantial support for a faster universal expansion rate than our currently accepted framework should allow.
Dan Scolnic, a Duke University associate professor in physics who led the recent research, frames the situation succinctly.
“The tension now turns into a crisis,” he said.
Tense Times for the Hubble Constant
For almost a century, scientists have attempted to confirm the universe’s expansion rate, a phenomenon first revealed by astronomer Edwin Hubble’s groundbreaking discoveries in 1929.
The fact that the universe is expanding seems to point to the idea that it had one point originating from the single, explosive event at the dawn of universal time as we know it, which astrophysicists call the Big Bang.
Although seemingly self-evident, the theory has had its detractors over the decades. This most famously included astronomer Fred Hoyle who, ironically, was the progenitor of its popular name during a BBC Radio interview in which he was the first to refer to this event as a “Big Bang.”
For Scolnic, a physicist all too aware of the controversy surrounding the issue that he now calls a “crisis,” attempting to map the universe’s size and expansion rate is tantamount to assembling a growth chart. In other words, astrophysicists know what size the universe was at the time of the Big Bang—the question is, how did it grow to its current size?
According to Scolnic, the local universe containing the Milky Way and its neighboring galaxies, as they currently appear, does not easily connect with its earliest appearance at the dawn of time using the standard model of cosmology.
Scolnic says that, at least in some sense, “our model of cosmology might be broken.”
Addressing the Hubble Tension Controversy
In addressing this longstanding controversy, Scolnic and his team employed the use of a “cosmic ladder” which drew from separate data collected with help from the Dark Energy Spectroscopic Instrument (DESI).
From its location at Kitt Peak National Observatory, DESI is currently observing more than 100,000 galaxies. “The DESI collaboration did the really hard part,” Scolnic said, though adding that “their ladder was missing the first rung.”
Nonetheless, the data it provided for the measurement effort allowed Scolnic and his research team to gauge more precise distances from Earth to a celestial object with this “ladder” the DESI data helped facilitate—in this case, the Coma Cluster, one of the nearest galactic clusters to Earth.
“I knew that that would give us one of the most precise measurements of the Hubble constant we could get,” Scolnic recently said. “[S]o when their paper came out, I dropped absolutely everything and worked on this non-stop.”
From Here to the Coma Cluster
For their measurement from Earth to the Coma cluster, Scolnic’s team relied on light curves associated with 12 Type Ia supernovae it contains.
These supernovae produce luminosity that can often be reliably predicted and used to accurately determine their distance. Performing their measurements, Scolnic and the research team measured a distance of approximately 320 million light-years, which places the Coma cluster within the center of the range of distances that comprise nearly four decades of past studies.
This essentially provided the team with a very reasonably certain sign of the measurement’s accuracy.
“This measurement isn’t biased by how we think the Hubble tension story will end,” Scolnic explained, adding, “This cluster is in our backyard, it has been measured long before anyone knew how important it was going to be.”
As Scolnic and his team write in their recent paper describing the work, “By extending the Hubble diagram to Coma, a well-studied location in our own backyard whose distance was in good accord well before the Hubble tension, DESI indicates a more pervasive conflict between our knowledge of local distances and cosmological expectations.”
“We expect future programs to refine the distance to Coma and nearer clusters to help illuminate this new local window on the Hubble tension,” the study’s authors add.
Scolnic and his team’s new paper, “The Hubble Tension in Our Own Backyard: DESI and the Nearness of the Coma Cluster,” was published on January 15, 2025, in The Astrophysical Journal Letters.
Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. He can be reached by email at micah@thedebrief.org. Follow his work at micahhanks.com and on X: @MicahHanks.