Like part of a cosmic Russian doll, our
universe may be perfectly nested inside a black hole that is itself part of a
larger universe. In turn, all the black holes found so far in our universe—from
the microscopic to the supermassive—may be ultimate doorways into alternate
realities.

According to a mind-bending new theory, a
black hole is actually a tunnel between universes—a type of wormhole. The
matter the black hole attracts doesn’t collapse into a single point, as has
been predicted, but rather gushes out a “white hole” at the other end of the
black one, the theory goes.
In a paper published in the journal Physics
Letters B, Indiana University physicist Nikodem Poplawski presents new
mathematical models of the spiraling motion of matter falling into a black
hole. His equations suggest such wormholes are viable alternatives to the
“space-time singularities” that Albert Einstein predicted to be at the centers
of black holes. According to Einstein’s equations for general relativity,
singularities are created whenever matter in a given region gets too dense, as
would happen at the ultra-dense heart of a black hole.

Einstein’s theory suggests singularities take
up no space, are infinitely dense, and are infinitely hot—a concept supported
by numerous lines of indirect evidence but still so outlandish that many
scientists find it hard to accept. If Poplawski is correct, they may no longer
have to. According to the new equations, the matter black holes absorb and
seemingly destroy is actually expelled and becomes the building blocks for
galaxies, stars, and planets in another reality.

The notion of black holes as wormholes could
explain certain mysteries in modern cosmology, Poplawski said. For example, the
big bang theory says the universe started as a singularity. But scientists have
no satisfying explanation for how such a singularity might have formed in the
first place. If our universe was birthed by a white hole instead of a
singularity, Poplawski said:
“It would solve this problem of black hole
singularities and also the big bang singularity.”

Wormholes might also explain gamma ray bursts,
the second most powerful explosions in the universe after the big bang. Gamma
ray bursts occur at the fringes of the known universe. They appear to be
associated with supernovae, or star explosions, in faraway galaxies, but their
exact sources are a mystery.
Poplawski proposes that the bursts may be
discharges of matter from alternate universes. The matter, he says, might be
escaping into our universe through supermassive black holes—wormholes—at the
hearts of those galaxies, though it’s not clear how that would be possible. The
wormhole theory may also help explain why certain features of our universe
deviate from what theory predicts, according to physicists.

“It’s kind of a crazy idea, but who knows?” he
said. There is at least one way to test Poplawski’s theory: Some of our
universe’s black holes rotate, and if our universe was born inside a similarly
revolving black hole, then our universe should have inherited the parent
object’s rotation. If future experiments reveal that our universe appears to
rotate in a preferred direction, it would be indirect evidence supporting his
wormhole theory, Poplawski said.
Based on the standard model of physics, after
the big bang the curvature of the universe should have increased over time so
that now—13.7 billion years later—we should seem to be sitting on the surface
of a closed, spherical universe. But observations show the universe appears
flat in all directions.
What’s more, data on light from the very early
universe show that everything just after the big bang was a fairly uniform
temperature. That would mean that the farthest objects we see on opposite
horizons of the universe were once close enough to interact and come to
equilibrium, like molecules of gas in a sealed chamber.

Again, observations don’t match predictions,
because the objects farthest from each other in the known universe are so far
apart that the time it would take to travel between them at the speed of light
exceeds the age of the universe. Inflation states that shortly after the
universe was created, it experienced a rapid growth spurt during which space
itself expanded at faster-than-light speeds. The expansion stretched the
universe from a size smaller than an atom to astronomical proportions in a
fraction of a second.
The universe therefore appears flat, because
the sphere we’re sitting on is extremely large from our viewpoint—just as the
sphere of Earth seems flat to someone standing in a field. Inflation also
explains how objects so far away from each other might have once been close
enough to interact. But—assuming inflation is real—astronomers have always been
at pains to explain what caused it. That’s where the new wormhole theory comes
in.
According to Poplawski, some theories of
inflation say the event was caused by “exotic matter,” a theoretical substance
that differs from normal matter, in part because it is repelled rather than
attracted by gravity. Based on his equations, Poplawski thinks such exotic
matter might have been created when some of the first massive stars collapsed
and became wormholes.
“There may be some relationship between the
exotic matter that forms wormholes and the exotic matter that triggered
inflation,” he said.
The new model isn’t the first to propose that
other universes exist inside black holes. Damien Easson, a theoretical
physicist at Arizona State University, has made the speculation in previous
studies.
“What is new here is an actual wormhole
solution in general relativity that acts as the passage from the exterior black
hole to the new interior universe.In our paper, we just speculated that such a
solution could exist, but Poplawski has found an actual solution,” said Easson,
referring to Poplawski’s equations (who was not involved in the new study).
Nevertheless, the idea is still very speculative, Easson said in an email.
“Is the idea possible? Yes. Is the scenario
likely? I have no idea. But it is certainly an interesting possibility. Future
work in quantum gravity—the study of gravity at the subatomic level—could refine
the equations and potentially support or disprove Poplawski’s theory”, Easson
said.
Overall, the wormhole theory is interesting,
but not a breakthrough in explaining the origins of our universe, said Andreas
Albrecht, a physicist at the University of California, Davis, who was also not
involved in the new study. By saying our universe was created by a gush of
matter from a parent universe, the theory simply shifts the original creation
event into an alternate reality. In other words, it doesn’t explain how the
parent universe came to be or why it has the properties it has—properties our
universe presumably inherited.
“There’re really some pressing problems we’re
trying to solve, and it’s not clear that any of this is offering a way forward
with that,” he said.
Still, Albrecht doesn’t find the idea of
universe-bridging wormholes any stranger than the idea of black hole
singularities, and he cautions against dismissing the new theory just because
it sounds a little out there.
“Everything people ask in this business is
pretty weird,” he said. “You can’t say the less weird [idea] is going to win,
because that’s not the way it’s been, by any means.”
"Again, observations don’t match predictions, because the objects farthest from each other in the known universe are so far apart that the time it would take to travel between them at the speed of light exceeds the age of the universe" This assumption is based on time being static when we know it is slowed by gravity. Time in a earlier universe could have passed at a much slower rate.
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