University of Portsmouth scientists attempting to solve the cosmic mystery known as the Hubble Tension suggest that Earth may be located in a massive void in space, which would account for conflicting data related to the universe’s expansion.
The researchers behind the controversial proposal, which involves measuring sound waves created by the Big Bang, suggest that solving this cosmic mystery could impact research into theoretical dark matter and dark energy, in addition to helping confirm the universe’s age.
A Huge Void in Space Could Explain Hubble Tension
Decades after astronomer Edwin Hubble first proposed a formula to express the rate of expansion of the universe, which modern astronomers call the Hubble Constant, newer measurements of distant galaxies made by modern astronomical observatories found the data conflicted with Hubble’s calculations of the local region of space’s expansion. Known as the Hubble tension, these mismatched readings have created a cosmic mystery that scientists are still trying to unravel.
In the newly proposed theory, Dr Indranil Banik of the University of Portsmouth and colleagues suggest that a huge void surrounding the Milky Way and much of local space could cause a gravitational imbalance. Under this scenario, the gravitational pull of the denser matter outside the void on the matter inside the void would look like a different expansion rate in local space.
“A potential solution to this inconsistency is that our galaxy is close to the centre of a large, local void,” Banik explained. “It would cause matter to be pulled by gravity towards the higher density exterior of the void, leading to the void becoming emptier with time.”
According to Banik’s team’s theory, the velocity of objects “away from us” would exceed expected velocities if the void weren’t present. If correct, the difference would give the false appearance of local space expanding faster than distant space.
Still, the team’s theory has particular constraints. For example, the entire solar system, including Earth, would need to be very near the center of the proposed huge void in space. This lower-density region would need to have a radius of roughly one billion light years. Furthermore, the average matter density within the huge void in space would also have to be around 20% below the universe’s average.
The researchers note that “directly counting” the galaxies in this region of space does offer support for their concept, as the density of our local universe is lower than that of nearby space regions. However, the researchers conceded that the mere existence of such a huge void in space would conflict with the standard model of cosmology, which predicts a much more spread-out matter density, resulting in an entirely new cosmic mystery.
New Data on Big Bang Sound Waves Offers New Support
To provide new support for their concept of a huge void in space, Banik and colleagues gathered data from the Planck satellite on baryon acoustic oscillations (BAOs). Described as the “sound of the Big Bang,” BAOs offer a unique window into past events.
“These sound waves traveled for only a short while before becoming frozen in place once the universe cooled enough for neutral atoms to form,” Banik explained. “They act as a standard ruler, whose angular size we can use to chart the cosmic expansion history.”
If the team’s theory is correct and the Earth and much of local space are at the center of a huge void in space, Banik says the evidence could be found in BAOs.
“A local void slightly distorts the relation between the BAO angular scale and the redshift because the velocities induced by a local void and its gravitational effect slightly increase the redshift on top of that due to cosmic expansion,” he explained.
The team examined the last 20 years of BAO measurements from galaxy surveys, analyzed alongside Planck satellite data, looking for such effects. According to their published study, the analysis found overwhelming evidence for a model of local space that included their proposed void.
“By considering all available BAO measurements over the last 20 years, we showed that a void model is about one hundred million times more likely than a void-free model with parameters designed to fit the CMB observations taken by the Planck satellite, the so-called homogeneous Planck cosmology,” Banik said.
Redshift Comparison Could Provide Critical Evidence
Next, the research team plans to support their huge void model with different measurements. One approach involves examining the light spectra of galaxies that have ceased forming stars to determine their star types and proportions. This data allows astronomers to establish the age of a targeted galaxy.
According to the researchers, combining this cosmological chronometer data with galaxy redshift data reveals how much the light has been stretched over the eons before reaching Earth. If their theory is correct, a variance should appear between redshift data distorted by local gravitational effects and other dating methods. Dr. Banik says that although more work is needed, his team’s model offers a viable solution to a decades-old cosmic mystery.
“The Hubble tension is largely a local phenomenon, with little evidence that the expansion rate disagrees with expectations in the standard cosmology further back in time,” Banik said. “So, a local solution like a local void is a promising way to go about solving the problem.”
Christopher Plain is a Science Fiction and Fantasy novelist and Head Science Writer at The Debrief. Follow and connect with him on X, learn about his books at plainfiction.com, or email him directly at christopher@thedebrief.org.