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Distorted Sound of the Early Universe Suggests We Are Living In a Giant Void (phys.org) 42

Posted by BeauHD from the do-you-feel-small-yet dept.
A new study analyzing distorted sound waves from the early universe suggests we may live in a massive cosmic void "with roughly 20% lower than the average density of matter," writes Indranil Banik in an article for The Conversation. "Not every physicist is convinced that this is the case. But our recent paper analyzing distorted sounds from the early universe, published in the Monthly Notices of the Royal Astronomical Society, strongly backs up the idea." Slashdot reader alternative_right shares an excerpt from the report: My colleagues and I previously argued that the Hubble tension might be due to our location within a large void. That's because the sparse amount of matter in the void would be gravitationally attracted to the more dense matter outside it, continuously flowing out of the void. In previous research, we showed that this flow would make it look like the local universe is expanding about 10% faster than expected. That would solve the Hubble tension. But we wanted more evidence. And we know a local void would slightly distort the relation between the BAO angular scale and the redshift due to the faster moving matter in the void and its gravitational effect on light from outside.

So in our new paper, Vasileios Kalaitzidis and I set out to test the predictions of the void model using BAO measurements collected over the last 20 years. We compared our results to models without a void under the same background expansion history. In the void model, the BAO ruler should look larger on the sky at any given redshift. And this excess should become even larger at low redshift (close distance), in line with the Hubble tension. The observations confirm this prediction. Our results suggest that a universe with a local void is about one hundred million times more likely than a cosmos without one, when using BAO measurements and assuming the universe expanded according to the standard model of cosmology informed by the CMB.

Our research shows that the ACDM model without any local void is in "3.8 sigma tension" with the BAO observations. This means the likelihood of a universe without a void fitting these data is equivalent to a fair coin landing heads 13 times in a row. By contrast, the chance of the BAO data looking the way they do in void models is equivalent to a fair coin landing heads just twice in a row. In short, these models fit the data quite well. In the future, it will be crucial to obtain more accurate BAO measurements at low redshift, where the BAO standard ruler looks larger on the sky -- even more so if we are in a void. The average expansion rate so far follows directly from the age of the universe, which we can estimate from the ages of old stars in the Milky Way. A local void would not affect the age of the universe, but some proposals do affect it. These and other probes will shed more light on the Hubble crisis in cosmology.

Distorted Sound of the Early Universe Suggests We Are Living In a Giant Void More | Reply

Distorted Sound of the Early Universe Suggests We Are Living In a Giant Void

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  • when you can parameterize the matter distribution in the universe. That is quite a lot of parameters to add to the model.

  • That's not actually a void, it's just the giant open space under Cowboy Neal's hat.

  • timescape (Score:5, Interesting)

    by spaceman375 ( 780812 ) on Tuesday July 29, 2025 @04:07AM (#65552336)
    Time runs faster in the middle of a void than anywhere else in the universe. I'd like to see a map of how old the universe is based on local density. If we are in a void, we are ahead of the universal average, but how far? I doubt this has much bearing on the Drake Equation, but it's nice to imagine that we are some of the first lifeforms to attain self awareness and technological skills. Either way, a documentary describing the lifetime of a photon as it travels between voids and galactic cores would be fascinating. What does the uninerse look like from each of these places?
    • Spellchecker failure: What's a Uninerse?
    • Imagine looking at a still picture that from your perspective does not seem to change at all. Except over a very long time you start to notice that things seem to look a bit different and the picture seems to have gotten a bit bigger than it was a long time ago, or maybe it's just your imagination. And this is assuming the photon can see distant things in realtime without delay. I imagine this would be pure hell for this hypothetical sentient photon, like being locked into solitary confinement and having n

      • I imagine this would be pure hell for this hypothetical sentient photon, like being locked into solitary confinement and having nothing but a piece of art on the wall that you can't tell if it's actually animating or if you are simply going mad.

        Let me guess - you're a fan of the original Twilight Zone TV series? 8^)

      • Time for it has stopped. Which raises the interesting question of how something suspended in time can interact with anything or even move.

        • Time for it has stopped.

          At the event horizon. If we are theorising that this bubble is some sort of black hole. Inside our universe bubble, the curvature flattens out again*. Think about the space-time curvature at the center of a large mass.

          It's possible that time reverses direction when crossing the event horizon. But that would be relative to the "forward" flow of time on the other side. Which we can never see.

          *Never mind the conjectures over the singularity of infinite density at the center of a black hole. They are unprovab

    • Not that I claim to understand any of the science here, but wanted to say that your claim about time "running faster in the middle of a void" brought to mind the notion of the "zones of thought" from the fantastic book series A" Fire Upon the Deep", by Vernor Vinge :)

    • Re: (Score:2)

      by HiThere ( 15173 )

      Is the void they're talking about an intra-galactic void or an inter galactic-cluster void? I assumed the latter, in which case the Drake equation would be irrelevant. We *are* living in an intra-galactic void, but the measured density variation isn't enough to meaningfully distort time.

    • For photons, the PoV is that the entire universe is either ahead of them, or behind them. They have a pretty boring PoV, but then again they can't really be observers.

  • Not every physicist is convinced that this is th (Score:2, Interesting)

    by Anonymous Coward

    Understatement of the year... I'd argue that the huge majority (over 95%) of cosmologists - let alone physicists - would not accept the "void" argument. "Swiss cheese" models and other such ideas that break the cosmological principle (homogeneity and isotropy on large scales) have been around for a long time, and never got anywhere.

    This is just another exercise in overfitting: "Most models have X parameters, my model has X+1 and can explain this 1 extra thing! "

    • So far our models haven't done a great job of explaining the situation of the current universe so there's no reason to assume they've got this right either.

    • Re: (Score:2)

      by HiThere ( 15173 )

      Just about all cosmologists assume the basic principle is correct. It's demanded by General Relativity. But doing the calculations is pretty intractable, and depends on data measurements that are of uncertain accuracy. THAT's why these theories have never gotten anywhere.

      These folks are claiming that now we have good enough data and good enough computers to reliably do the calculations. ... Well, most folks haven't even looked at the problem. And it's a change, so they're dubious. And being dubious is

  • Assumptions (Score:4, Interesting)

    by Retired Chemist ( 5039029 ) on Tuesday July 29, 2025 @08:37AM (#65552626)
    The classic assumption is that the universe is homogeneous and isotropic (that is the same in all directions). This is the simplest assumption and makes for the simplest models, but observation of the real universe clearly shows that this is not the case. On every scale, structures are observed. It is not certain that the solar system is in some sort of void, but the idea cannot be ruled out. It would have to be a void on a gigantic scale, however. It is quite clear that we are not in a void on a local scale (Milky Way galaxy, local galaxy group etc.).

    • They're just being a bit charitable with the definition of "void." They don't mean completely—or even mostly—empty; just that the density of matter is lower here than in most other parts of the Universe.

      if I recall correctly, its on the scale of the Local Group that we are in a void. There are only three galaxies of any note nearby: the Milky Way (us), Andromeda, and Triangulum. All the other galaxies in the Local Group are relatively small and insignificant. Most other large galaxies have more

      • It's on a much larger scale than that. They assume the region of low density extends out to 300 Mpc, or just under 1 billion light years. That's 100 times larger than the local group.

  • We don't need to try listening to the distorted sound of the early universe to suggest we are living in a giant void, turning on the TV does the trick.

  • Why would the things in a void rush out of it?

    If you are in a void, then everything around you implodes into you.

    • Re: (Score:2)

      by myrdos2 ( 989497 )

      If they're right, then both are currently happening.

    • Re: (Score:2)

      by pz ( 113803 )

      Thinking of the void as an analogy to a gas is misleading, that's why your supposition doesn't work.

      The universe is expanding, everywhere, as far as we can tell. Without any evidence to the contrary (and a fair bit of evidence supporting it), the expansion is constant, everywhere, and is described by a value called, you guessed it, the Hubble Constant. Most recently, however, a handful of different measurements have suggested two disparate values for the Hubble Constant, resulting in what's known as the H

  • Sure feels like that sometimes

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