An artist's depiction of a black hole – birthplace of our Universe? via
We’re all familiar with the Big Bang theory, the one that states that the universe exploded out of a single, dense point. But there’s a major question tied up in the Big Bang that the known laws of physics can’t explain: what was the nothing that came before everything? Some cosmologists have taken this unknown start to the universe in a different direction and suggested a brand new model for our universe. Instead of a Big Bang, our universe was formed from debris ejected when a four-dimensional star collapsed into a black hole.
The Big Bang, which surfaced in the late 1920s in the work of physicist Georges LeMaître and received a big boost in the 1960s through measurements of the cosmic microwave background, does offer explanations to some of the phenomena we see in the cosmos. Namely the fact that space is expanding. But it leaves other questions unanswered. The Big Bang doesn’t explain why such a violent event could have yielded a universe so uniform in temperature. The most common explanation is that some unknown energy made the young universe expand faster than the speed of light, which would have allowed a small patch with a uniform temperature to stretch out and that’s the cosmos we live in and see.
But the main problem with the Big Bang model is that nothing can explain what happened the moment that single point went bang, which leaves explanations about a uniform temperature largely in the realm of speculation. As Niayesh Afshordi, an astrophysicist at the Perimeter Institute for Theoretical Physics in Waterloo, Canada, puts it, “For all physicists know, dragons could have come flying out of the singularity.”
But an entirely different model might solve all these problems. With this question in mind, Afshordi and his colleagues turned to a 2000 study that states the three-dimensional universe is a membrane that floats through a ‘bulk universe’ made of four spatial dimensions.
The cosmic microwave background, the best evidence supporting the Big Bang model that we have. via
Taking this idea of a four-dimensional bulk universe further, Ashfordi's team realized that if this universe contained four-dimensional stars, they could collapse to form four-dimensional black holes. And much like the three-dimensional black holes in our universe do, these four-dimensional black holes could theoretically collapse and explode as supernovae, violently ejecting their outer layers.
So here’s how a four-dimensional black hole explains our universe. In our universe, a black hole is bounded on all sides by the event horizon, a boundary beyond which light can’t escape a black hole. In three-dimensional space, this boundary is a two-dimensional surface, but in four-dimensional space, this boundary would be a three-dimensional one called a hypersphere. When Afshordi’s team modeled the death of a four-dimensional star, they found that the ejected material would form a three-dimensional membrane surrounding that three-dimensional event horizon. This membrane has slowly expanded. And because the material inside the four dimensional black hole would have had an eternity to even out, the expelled universe is as uniform as what we see in our universe.
So the universe we live in, in short and according to this theory, is the three-dimensional membrane that was ejected from a four-dimensional black hole. And what scientists have long called the Big Bang is really just a mirage.
This model answers some questions, but, like the Big Bang theory, it also has some problems. Scientists mapping temperature fluctuations in the cosmic microwave background have found variations consistent with the Big Bang model that disagree with the Black Hole model.
This Black Hole model an interesting (if hard to grasp) alternative to the Big Bang, but physics textbooks are unlikely to go through a massive rewrite just yet. There are other alternatives floating around out there, like the Big Freeze model that suggests the early universe went through a state change similar to how a liquid turns to a solid. But for the time being, these alternatives lack the same amount of evidence as the Big Bang model, leaving that theory we know and love as the leading cosmological model.