A cosmic void could be distorting how we see the universe expand. Sound from the Big Bang may hold the clues.
According to astronomers, Earth and the entire Milky Way galaxy might be located within a vast, low-density region of space—essentially a cosmic void—that causes the universe to expand more rapidly in our area compared to surrounding regions.
This hypothesis offers a possible explanation for the persistent discrepancy known as the ‘Hubble tension’ and could contribute to determining the universe’s actual age, currently estimated at approximately 13.8 billion years.
Presented at the Royal Astronomical Society’s National Astronomy Meeting (NAM) in Durham, recent findings suggest that primordial sound waves—referred to as “essentially the sound of the Big Bang”—lend support to this concept.
Edwin Hubble introduced the Hubble constant in 1929 as a way to describe how quickly the universe is expanding. Scientists calculate it by measuring the distance to celestial bodies and their speed as they move away from us.
The challenge arises when predictions based on early-universe observations, using the standard cosmological model, indicate a slower expansion than what is observed in the nearby, present-day universe. This inconsistency is what defines the Hubble tension.
Explaining faster local expansion
“A potential solution to this inconsistency is that our galaxy is close to the centre of a large, local void,” explained Dr Indranil Banik, of the University of Portsmouth.
“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. As the void is emptying out, the velocity of objects away from us would be larger than if the void were not there. This therefore gives the appearance of a faster local expansion rate.”
He added: “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. So a local solution like a local void is a promising way to go about solving the problem.”
Conditions required for a local void
For this hypothesis to be valid, Earth and the solar system would need to be situated close to the center of a massive cosmic void roughly one billion light-years across, with a matter density around 20 percent lower than the cosmic average.
Observational data, such as galaxy counts, lend some support to this idea, as the density of galaxies in our local region appears to be lower than in adjacent areas of the universe.
Still, the concept of such a vast and pronounced void remains contentious, as it conflicts with the predictions of the standard cosmological model, which holds that matter should be more evenly distributed across the universe at these scales.
Evidence from baryon acoustic oscillations
Despite this, new data presented by Dr Banik at NAM 2025 shows that baryon acoustic oscillations (BAOs) – the “sound of the Big Bang” – support the idea of a local void.
“These sound waves travelled for only a short while before becoming frozen in place once the universe cooled enough for neutral atoms to form,” he explained.
“They act as a standard ruler, whose angular size we can use to chart the cosmic expansion history.”
He continues, “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.”
“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.”
Next steps and cosmic chronometer tests
The next step for researchers is to compare their local void model with other methods to estimate the history of the universe’s expansion, such as cosmic chronometers.
This involves looking at galaxies that are no longer forming stars. By observing their spectra, or light, it is possible to find what kinds of stars they have and in what proportion. Since more massive stars have shorter lives, they are absent in older galaxies, providing a way to establish a galaxy’s age.
Astronomers can then combine this age with the galaxy’s redshift – how much the wavelength of its light has been stretched – which tells us how much the universe has expanded while light from the galaxy was travelling towards us. This sheds light on the universe’s expansion history.
Meeting: National Astronomy Meeting 2025
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12 Comments
Great.Science news are very much salubrious and interesting for curious students,these news incite them and act like an impetus within them as a driving force. Astrophysics is one of the effulgent branches of them
Sort of makes sense, little is left at the centre of any big bang. The question becomes then what happens what happens to stuff as it runs out of push from the initial outward push. Gravity generally wins but from where. Of my ‘o’ level don’t help here.
The ‘center’ of the universe isn’t a ‘where’; it’s a ‘when’.
when You make our day start , just delightful as it can be… thank You much Scitech society…
https://youtu.be/7cPIMsdJiig?t=25
Legend feat. Huun-Huur-Tu…. sound creation at bubble
Can we blame climate change on it then?
I don’t buy in. The standard model is a hunch that helped us make sense of a lot of chaos. The Hubble tension is an indication that the standard model is incorrect. Instead of finding some new explanation for how the standard model is still correct in the face of indicators that it isn’t, we should just toss it out and start from scratch. It’s like string theory all over again. Scientists have a stubborn bias to preserve theories that they’ve spent time familiarizing themself with and contributing to, even when confronted with contradictory evidence.
Been saying that for years.
Ed, you are right – ‘standard model is a hunch’. You are also right in that it ‘makes sense of a lot of chaos.’
You correctly imply that the standard model is in trouble due to Hubble tension.
Any scientist would love to have his or her own theory replacing the standard model. But what will you replace it with? Any replacement will have to do better in making sense of the chaos currently handled by the standard model. It’s easy to say standard model is wrong; it’s very hard to actually come up with a replacement.
I don’t know how the Hubble tension will ultimately be resolved, but history suggests that it might be that the standard model gets reinterpreted and tweaked at the edges. Einstein rewrote the rules of Gravity, and yet Newton’s Laws on that are still used for all ordinary purposes. The phenomena that Newton explained were reinterpreted by Einstein, and the differences between the theories only show up in extreme situations when the gravity is super strong.
What a GYP……
The topography of the universe over time and how it changes nothing but our perceptions of time and distance.
If the dark matter was in its liquid state then baryonic and dark matter would have been much more concentrated. This would have resulted in deeper gravity wells. The time in these gravity wells to us would seem to be moving slower to us. But due to dark matter condensing the baryonic matter would also have been cooled and rushing together.
Once stars were formed and black holes became active the ratio of liquid to gaseous dark matter would have decreased over time thus affecting the evolution of particle masses. And making the gravity wells progressively shallower and larger in diameter over time. Galaxy clusters would have evaporated almost all of their liquid dark matter resulting in the shallowest part of the gravity well being near the canter of the cluster. Also part of redshift is due to the difference depth of the average gravity well at that point in time compared to now. The slope of that line would also have decreased over time. As vaporized dark matter spread further from the gravity wells the slope there would have increased (dark energy).
Light red shifts as it climbs out of a gravity well. Thus the further you go back in time the more light is redshifted. This would leave everything the same with the exception of our perception that the universe is expanding. Also if a big portion of the redshift is from climbing out of a deeper gravity well then we are not looking as far into the past as we think.
Wow. I thought your ad hoc assertions were ridiculous before. Just tell people you never had any clue in the first place… Did you all hire a PR guy to come up with this to try and maintain the illusion of being relevant? That is what it truly feels like. I could see you all in an office trying to figure out how to cover up the fact that you just been totally making everything up this entire time and then your PR guy was like “well, what if, what if, we say that, you know, the pressure is different here and it’s a Time distortion?”. Fact is, you never knew anything in the first place…