“The physical characteristics of the Big Bang resemble the geometric appearance of the interior of a black hole.”

The standard FRW Big Bang models are also different from a white hole. A white hole has an event horizon that is the reverse of a black hole event horizon. Nothing can pass into this horizon, just as nothing can escape from a black hole horizon. The FRW models do not have the same type of event horizon as black or white holes.

A spacetime singularity is a breakdown in spacetime, either in its geometry or in some other basic physical structure. Our current theory of spacetime, general relativity, not only allows for singularities, but tells us that they are unavoidable in some real-world circumstances, including at the center of black holes and at the beginning of the universe (Big Bang).

We propose a new model of the universe where the Big Bang is the result of a gravitational bounce inside a black hole, sharing geometric similarities in the interior region with high curvature and singularity-like behavior, but evolving outward rather than collapsing.

A team of scientists is proposing a bold alternative to the Big Bang theory, suggesting that our universe may have formed inside a colossal black hole residing in a larger, parent universe. This model suggests that gravitational collapse doesn't end in a singularity, but instead bounces and begins expanding again, mimicking the Big Bang.

A new study published in the journal Physical Review D proposes that the Big Bang — the rapid unraveling of an infinitely dense point — actually took place in a black hole, which itself formed inside a larger “parent” universe. The lead author, Enrique Gaztanaga, suggests that the Big Bang was the outcome of a gravitational crunch or collapse that formed a very massive black hole, followed by a bounce inside it. This model aims to resolve issues with the standard cosmological model, such as the nature of the singularity where physics breaks down.

The occurrence of singularities is a failure of general relativity - and a strong indication that the theory is incomplete. Instead, one could describe the earliest universe and the interior of black holes using a theory of quantum gravity. At the singularity, the gravitational field becomes infinitely strong and rips apart spacetime itself.

A controversial theory suggests the observable universe is the result of matter rebounding after the collapse of a black hole in another parent universe. This new “Black Hole Universe” hypothesis, suggests that our universe possibly “bounced” from the formation of larger black hole in another parent universe.

The paper suggests the Big Bang was actually a 'Big Bounce', when matter falling into a giant black hole compressed, then rebounded and expanded outwards to create the Universe. “In other words, our entire observable Universe could be the inside of a black hole formed in a larger Universe,” Gaztañaga told BBC Science Focus.

The mathematics underpinning our understanding of the universe are quite similar to those describing black holes. Both stem from Albert Einstein's theory of general relativity. Coincidentally, the radius of the observable universe happens to be the same as it would for a black hole with the mass of our cosmos. However, many physicists still recognize the conceptual connection between black holes and the universe, stating, “Mathematically, they're very related,” but also, “They are kind of like the opposite of each other.”

A new model, published in Physical Review D, suggests the Big Bang was not the start of everything, but rather the outcome of a gravitational crunch or collapse that formed a very massive black hole – followed by a bounce inside it. This 'black hole universe' idea offers a radically different view of cosmic origins, grounded in known physics and observations, and addresses the problem of the Big Bang singularity where laws of physics break down.

We call both the Big Bang and black holes singularities because they involve infinite density where physics breaks down. Back at the beginning, 13.8 billion years ago, everything in the entire Universe was crushed down into a region of infinite density, and then everything expanded outward.

According to general relativity, a singularity exists inside every black hole, and the starting point of any universe described by a big bang model is a singularity as well. The occurrence of singularities is a failure of general relativity - and a strong indication that the theory is incomplete. Instead, one could describe the earliest universe and the interior of black holes using a theory of quantum gravity.

The main difference between a black hole singularity and the Big Bang singularity is that a black hole singularity is the end of spacetime and pulls matter in, while the Big Bang singularity is the beginning of spacetime where matter and space were created. Both are points of infinite density and curvature where general relativity is believed to cease to hold true.

The Big Bang did not produce a black hole because the event occurred everywhere in space, not at a single point, and the energy was uniformly distributed. This meant the net gravitational potential was near zero, and there was no central point for collapse. Furthermore, the rapid expansion of the early universe prevented a singular collapse.

Astrophysicist Dr. Paul Matt Sutter explains that while both the Big Bang and black holes involve singularities of infinite density, a black hole singularity is a point embedded within the larger universe, whereas the Big Bang singularity *was* the entire universe. He notes that the Big Bang avoided collapsing into a black hole because it was rapidly expanding, and the Schwarzschild limit does not apply to rapidly expanding matter.

In general relativity, the Big Bang is modeled by the FLRW metric, which is homogeneous and isotropic with flat or curved spatial sections, while black hole interiors (Schwarzschild) feature strong radial infall and tidal stretching, lacking the uniformity observed in cosmic microwave background data.

Both exist in mathematical models using General Relativity, and both are successful in describing astrophysical observations up to now. That is where the similarity ends, because the singularity at the beginning in the Big Bang model is mathematically a different singularity than the ones modeling black holes. The data that induced the Big Bang model resemble in the four dimensions of general relativity an explosion, whereas the data of black holes resemble a sink.

The Big Bang singularity lies in the past of all events in the universe, whereas a black hole singularity lies in the future. The Big Bang is more akin to a 'white hole,' the time-reversed version of a black hole. However, the standard Friedmann-Robertson-Walker (FRW) Big Bang models differ from a white hole, particularly in their event horizon characteristics, and the Big Bang's rapid expansion allowed it to avoid collapsing into a black hole.