Astronomers say we could live at the center of a 2 billion light-year-wide cosmic void that defies the laws of cosmology.

• Evidence suggests that our galaxy lies inside a cosmic void, a vast expanse of relatively empty space.

• However, according to our cosmological laws, this void should not exist.

• New research indicates that such a vacuum could explain unusual behavior in nearby galaxies.

Our home galaxy, the Milky Way, is just one of billions in our universe. So overall we’re not that special. But zoom in on our local cosmic neighborhood and that story begins to change.

According to a growing list of evidence, we live in the crosshairs of a giant cosmic void – the largest ever observed. Astronomers first suggested the existence of such a void in 2013, and evidence for its existence has been accumulating ever since.

But the most interesting thing is that this giant void shouldn’t exist in the first place. If it exists, that means something is probably wrong with our understanding of the cosmos.

We live in a void that shouldn’t exist

According to a fundamental theory of cosmology called the cosmological principle, matter in the universe should be uniformly distributed on very large scales.

The reason this is important is that by assuming uniformity, scientists can apply the same laws of physics to nearby objects as they can to objects on the margins of the early universe. In other words, everything works according to the same universal laws.

It is a simple and straightforward approach to studying and understanding our universe, and it suggests that voids – like the one we live in – should not exist.

However, multiple observations over the past decade suggest that matter in the universe might cluster into regions of high and low densities, meaning it’s not so uniform after all.

“It’s now clear that we’re in significant underdensity,” Indranil Banik, a postdoctoral researcher at the University of St. Andrews, told Business Insider.

“There are a few people who still oppose it to some extent. For example, some people have rightly argued that such a gap should not exist in the Standard Model, which is true. This does not prove unfortunately not that there isn’t any,” he added.

Banik co-authored a paper published late last year in the peer-reviewed journal Monthly Notices of the Royal Astronomical Society, which suggests we might live near the center of this void – called the KBC void – about 2 billion light years away. Large enough to accommodate 20,000 Milky Way galaxies from one end to the other.

The KBC vacuum defies the laws of cosmology

The KBC vacuum is not completely empty. It’s not possible, because we live there. But if Banik and his colleagues’ calculations are correct, the void would be about 20 percent emptier than the space outside its boundaries.

That might not seem like a big deficit, but it’s enough to cause some confusing behavior in our local cosmic neighborhood, according to a recent study.

In particular, nearby stars and galaxies are moving away from us faster than they should be. Cosmologists have a value, called the Hubble constant, that they use to describe how fast the expansion of the universe is accelerating.

The Hubble constant must have the same value wherever you look, whether near or far away. The problem is that galaxies and stars in our neighborhood appear to be moving away from us faster than the Hubble constant predicts, essentially defying our law of cosmology that describes the growth and evolution of the universe.

Astronomers cannot agree on the cause of this discrepancy in the Hubble constant, and this controversy has come to be known as the Hubble tension.

Banik and his colleagues suggest that the vacuum could be a solution, because regions of high density and stronger gravity outside the vacuum could attract galaxies and stars towards them.

Banik says these flows could explain why cosmologists have calculated a higher value for the Hubble constant when examining nearby objects. Things move faster in a vacuum, flying from our empty region into crowded space.

Mystery solved? Not yet.

If a vacuum exists, as the evidence suggests, that may mean we will need to revise some of the physical laws we use to describe the cosmos. After all, Banik’s theory would explain why the Hubble constant is higher in our local cosmic region.

“The hypothesis that a local vacuum could explain the Hubble voltage by inducing large outflows seems sound in principle, especially given the observational data cited in the study,” Brian Keating, cosmologist and professor of physics at the UC San Diego which studies the Hubble constant. said BI in an email.

But there are still questions that need to be answered. On the one hand, how far does the influence of the void extend? » asks Keating.

“If the local vacuum is not representative of the wider cosmos, this may only provide a local solution, not a global one – it will not ‘resolve’ the Hubble tension,” he wrote.

Keating also notes that Banik’s theory has some limitations. The results of the study depend on the type of vacuum model used, he wrote. Different models give different predictions about the effects of vacuum and “mass flux,” or the average speed of galaxies as they move through the cosmos. Furthermore, models can only offer a simplified view of what the vacuum actually is.

All this means is that the void could propose a solution, but “it is not yet definitive ‘proof’ of the resolution of the tension,” Keating wrote.

There are also other solutions to consider, such as early dark energy. This theory proposes a new form of energy that affects the rate of expansion of the early universe, ultimately leading to the Hubble voltage we observe today, Keating wrote.

But Banik notes that the early theory of dark energy conflicts with certain truths about the universe. For example, you would have to change the age of ancient stars for this to work. Otherwise, these stars would have to be older than the universe itself, Banik said.

He therefore sticks to his theory of the void. His next research project will analyze supernova data to determine whether the Hubble constant returns to the value predicted by our standard model of cosmology outside of a vacuum. If his theory is correct, there should be no Hubble voltage outside the vacuum boundaries.

“That’s the main thing that sometimes keeps me up at night: worrying about whether supernovae really show that we’re in a faster-expanding universe and that there’s no sign of an edge void,” Banik said.

Until then, the Hubble tension remains a mystery waiting to be resolved.

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