## With Origins From a Singularity

The most accepted theory of the origin of the universe is still the Big Bang. The theory proposes the universe started from a small singularity (the gravitational kind), then began to expand over the succeeding 13.8 billion years. Although this expansion has its own issues, a bigger question remains: what preceded the Big Bang?

Ethan Siegel, physicist and contributor at *Forbes*, explains the possibility that the universe could have started from a black hole. Physicists Niayesh Afshordi, Razieh Pourhasan, and Robert Mann originally proposed the idea in 2013 — a scenario that's survived the scrutiny of other physicists ever since.

The evidence that supports that theory is the singularity, an occurrence found in only two instances in the universe — the Big Bang and black holes. A gravitational singularity is a one-dimensional point where the laws of physics regarding spacetime breaks down.

In black holes, the singularity exists in the event horizon. This event horizon defies everything that supposedly governs the physics of our universe, both quantum mechanics and general relativity. A black hole's event horizon is supposedly more massive than what the particles in it can hold.

"The fact that black holes in our Universe are much more massive than this isn’t a problem," Siegel explains. He adds, "the laws of physics that we know break down at the singularity we calculate at the center. If we ever want to describe it accurately, it’s going to take a unification of quantum theory with General Relativity."

## Black Hole Birthing

Because our understanding of the universe is still limited, we simply call this point the singularity. Basically, a black hole's event horizon is a one-dimension iteration of our three-dimensional universe. This is what the Perimeter Institute study explores. Is it possible that our universe is a product of a larger, primeval black hole's singularity? Is our universe the three-dimensional wrapper around another universe's event horizon?

"In this scenario, our universe burst into being when a star in a four-dimensional universe collapsed into a black hole," according to a Perimeter Institute press release.

Siegel explains how this is possible:

"As the black hole first formed, the event horizon first came to be, then rapidly expanded and continued to grow as more matter continued to fall in. If you were to put a coordinate grid down on this two-dimensional wrapping, you'd find that it originated where the gridlines were very close together, then expanded rapidly as the black hole formed, and then expanded more and more slowly as matter fell in at a much lower rate. This matches, at least conceptually, what we observe for the expansion rate of our three-dimensional universe."

Would this mean that each time a black hole is formed, a two-dimensional universe spawns? Siegel comments: "As crazy as it sounds, the answer appears to be maybe."

As fascinating as this may be, it's still just theory. We'll need a better understanding of the physics of our universe in order to confirm it.

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