A new theory suggests that the birth of the Universe could have happened after a four-dimensional star collapsed into a black hole and ejected debris.
The standard theory is that the Universe grew from an infinitely dense point or singularity. The standard Big Bang model tells us that the Universe exploded out of an infinitely dense point, or singularity. But it is not known what triggered this outburst. Now, it is proposed that the Big Bang was mirage from collapsing higher-dimensional star.
In a paper posted last week, Afshordi (an astrophysicist at the Perimeter Institute for Theoretical Physics) and his colleagues turn their attention to a proposal made in 2000. In that model, our three-dimensional (3D) Universe is a membrane, or brane, that floats through a ‘bulk universe’ that has four spatial dimensions.
Ashfordi’s team realized that if the bulk universe contained its own four-dimensional (4D) stars, some of them could collapse, forming 4D black holes in the same way that massive stars in our Universe do: they explode as supernovae, violently ejecting their outer layers, while their inner layers collapse into a black hole. When Afshordi’s team modelled the death of a 4D star, they found that the ejected material would form a 3D brane surrounding that 3D event horizon, and slowly expand.
The event horizon of a black hole — the point of no return for anything that falls in — is a spherical surface. In a higher-dimensional universe, a black hole could have a three-dimensional event horizon, which could spawn a whole new universe as it forms.
It could be time to bid the Big Bang bye-bye. Cosmologists have speculated that the Universe formed from the debris ejected when a four-dimensional star collapsed into a black hole — a scenario that would help to explain why the cosmos seems to be so uniform in all directions.
The standard Big Bang model tells us that the Universe exploded out of an infinitely dense point, or singularity. But nobody knows what would have triggered this outburst: the known laws of physics cannot tell us what happened at that moment.
It is also difficult to explain how a violent Big Bang would have left behind a Universe that has an almost completely uniform temperature, because there does not seem to have been enough time since the birth of the cosmos for it to have reached temperature equilibrium.
To most cosmologists, the most plausible explanation for that uniformity is that, soon after the beginning of time, some unknown form of energy made the young Universe inflate at a rate that was faster than the speed of light. That way, a small patch with roughly uniform temperature would have stretched into the vast cosmos we see today. But the Big Bang was so chaotic, it’s not clear there would have been even a small homogenous patch for inflation to start working on.
Credit: Zeeya Merali, Nature News
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