This theory has recently become one of the biggest contenders for the "Theory of Everything"; it holds more evidence than "String Theory" and fills the "gaps" in the "Big Bang Theory". The Einstein-Cartan-Kibble-Sciama Theory of Gravity could be the explanation to our universe's beginning.
The standard derivation of Einstein-created General Relativity has answered most of universe's biggest mysteries but there is a flaw. As more developments in Quantum Physics are revealed, General Relativity's Theory of Gravity needs an "update". The standard Theory of Gravity takes no account of the intrinsic momentum of spin half particles. The Einstein-Cartan-Kibble-Sciama theory of gravity does.
This theory predicts that particles with half integer spin should interact, generating a tiny repulsive force called torsion. In ordinary circumstances, torsion is too small to have any effect. But when densities become much higher than those in nuclear matter, it becomes significant. Torsion prevents the formation of singularities inside a black hole.
Astrophysicists have long known that our universe is so big that it could not have reached its current size given the rate of expansion we see now. Instead, they believe it grew by many orders of magnitude in a fraction of a second after the Big Bang, the period known as known as inflation.
This theory's approach immediately solves the inflation problem, saying that torsion caused this rapid inflation, which means the universe as we see it today can be explained by a single theory of gravity without any additional assumptions about inflation. This makes it possible for universes to be born inside the event horizons of certain kinds of black hole where torsion prevents the formation of a singularity but allows energy density to build up, which leads to the creation of particles on a massive scale via pair production followed by the expansion of the new universe.
So why can't we see these Big Bangs happening in Black Holes?
For an object entering a black hole it experiences time at a normal rate but time appears very different to the outside observer. If an outside observer saw a spacecraft entering the event horizon (let's assume the craft would not disintegrate) it would appear that the spacecraft slows down as it gets closer to the event horizon until it stops completely before entering. To the outside observer time has utterly and completely stopped before the spacecraft has entered the Black Hole but to the spacecraft, it has entered the Event Horizon.
Nikodem Poplawski, co-creator of this theory has said "Such an expansion is not visible for observers outside the black hole, for whom the horizon's formation and all subsequent processes occur after infinite time." For this reason, he emphasizes, the new universe is a separate branch of space time and evolves accordingly.
This theory could also explain why time seems to flow in only one direction and not backwards.
The theory suggests that our "cosmic arrow" of time, the direction in which time flows, is inherited from its source, the "mother universe", the universe that contains the black hole we might be living in.
How does a black hole make a Big Bang?
This is speculative but famous astronomers like Poplawski himself and Michio Kaku have stated that the math is indicates that black holes can indeed form a Big Bang.
As the following can't either be proven false or true it'll remain theoretical for as long as the human race obeys the laws of physics. The math has shown that matter and energy shouldn't simply "disappear" when it falls past the event horizon. It's speculated that the matter and energy passes through the Black Hole and gets shot out of a "White Hole" on the other side. The Big Bang could be the flipside of a Black Hole.
" If you look at the equation for a black hole and put in the parameters of the universe; the mass of the universe, the size of the universe. Bingo! You find that our universe solves the equations for a black hole! In other words, we could be inside an Event Horizon."
There are billions of black holes in the observable universe and the NASA/ESA satellite SWIFT is discovering at least one black hole every day. Which means there could be an undefined amount of "Daughter Universes". Our place in existence of everything may have just gotten a lot more complex.
Though this seems to be a very logical answer to our existence. Since black holes don't follow the laws of physics and therefore doesn't agree with the physics of our universe, this theory has very few possibilties of being proven correct since it would require someone or something entering a black hole and being able to send back the information proving it right.
The only way this theory can be proven correct is to find a way to detect properties from the mother universe that have been inherited in this one, providing experimental, falsifiable proof of the idea.