Could Black Holes Be Portals to Other Universes?

SCATTERED THROUGHOUT THE UNIVERSE are ravenous black holes that pull gas, dust, light and even other black holes into their maw, never to be seen again. Like a riptide pulling swimmers out to sea, the gravity inside a black hole pulls matter past a point of no return, called the event horizon, and condenses it so tightly that physics as we know it begins to break down, creating a “singularity.” It’s this singularity, in particular, that troubles physicists because it throws their most important theories about the universe into question.

That’s why theoretical physicist Nikodem Poplawski, Ph.D., asked a big question back in 2010: what if black holes don’t contain a singularity at all? Instead, Poplawski’s theory suggests, the center of a black hole could contain a pathway into another universe. Weirder yet, his theory predicts that this may be how our own universe was created.

A paper describing this work, titled “Radial motion into an Einstein–Rosen bridge,” was published 14 years ago in the journal Physics Letters B. While the theory captured attention at the time, this topic is still rather niche among physicists. Many researchers have either moved on, or have never heard of the idea to begin with.

“It’s not easy to find a specialist on this topic,” says Nick Gorkavyi, Ph.D., a scientist and programmer at NASA who, alongside Nobel laureate John Mather, developed a theory about pulsating universes inside black holes.

A central concept driving Poplawski’s black hole theory is the notion of something called torsion, which behaves similarly to a gravitational force acting upon matter in the universe. Cosmological torsion is not something that science has proven —or, disproven—yet, but it’s a big idea that Poplawski believes is worth chasing because it could transform how we understand physics.

“Torsion [can] remove infinities,” Poplawski says, referring to high-level physics calculations. “Torsion makes physics finite.”

ON ITS FACE, POPLAWSKI’S THEORY seems simple enough. He explains that the “other side” of a black hole does not end in a singularity, but instead is connected via an Einstein-Rosen bridge (otherwise known as a wormhole) to something called a white hole. As its name suggests, a white hole is the opposite of a black hole in many ways; where a black hole swallows all light and matter, a white hole can spill it out.

Physicists originally considered the idea in the 1960s and 1970s, Poplawski says, but they lacked a mechanism to explain it. Enter: torsion. “At extremely large densities, torsion appears like a gravitational, repulsive force,” he explains. “That’s how it can prevent singularities.”

Poplawski believes this cosmic tunnel system could explain the creation of all matter in our universe.

“I think what happened is that when the black hole’s parent universe was collapsing … [because of] torsion, the singularity did not form,” he explains. “Because the matter was already within the event horizon and it wanted to move, it decided to create new space. Which is basically our growing universe.”

This explosion of matter, all at once through the back door of a black hole, is how Poplawski’s theory interprets the Big Bang. Or, as Poplawski and a handful of other cosmologists believe, the Big Bounce. Instead of a single moment of creation, the Big Bounce theorizes a back-and-forth tug between inflation and contraction, which Poplawski believes gave way over time to the expanding universe we know today.

This initial influx of matter into the new universe would have then caused a chain reaction to create a billion times more matter and propel the expansion of our universe. There’s a catch, however: this wormhole journey is a one-way street. Matter (like us) cannot pass back through the wormhole in reverse to revisit our parent universe.

ONE OF THIS THEORY’S biggest problems may also be one of its saving graces: it’s extremely difficult to prove. Dejan Stojkovic, Ph.D., is a professor of cosmology at the University of Buffalo. He says that Poplawski’s theory is logically sound, but it still faces challenges.

“Torsion … is a legitimate prediction of a self-consistent theory, [but] the question is whether our universe is described by such a theory,” Stojkovic says. “So far, we have not encountered any observations that require introduction of torsion. However, torsion might appear in very strong gravity regimes, for example near classical singularities, where we still do not have any observations.”

And while Gorkavyi is not convinced that torsion necessarily explains our universe, he does believe in Poplawski’s ultimate conclusion.

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“A major achievement of Poplawski is that he was one of the first in the 21st century to return to constructing a theoretical model of a universe inside a black hole,” he says. “I believe Poplawski is right, and our universe is inside a black hole hundreds of billions of light-years in size.”

The big question lying ahead for Poplawski and torsion is whether it might be possible to one day find concrete evidence to boost this idea from being simply hypothetical. Luckily, there are a couple ways that could happen, he says. Investigations into whether the universe is closed (meaning if it’s curved without an edge) or into the nature of inflation via the study of cosmic background radiation could offer support to the theory.

“It is an interesting and intriguing possibility,” Stojkovic says.

Sarah is a science and technology journalist based in Boston interested in how innovation and research intersect with our daily lives. She has written for a number of national publications and covers innovation news at Inverse.

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