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Study: Our 3D Universe Could Have Originated From a 4D Black Hole
New submitter TaleSlinger sends this quote from Nature:
"Afshordi'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. In our Universe, a black hole is bounded by a spherical surface called an event horizon. Whereas in ordinary three-dimensional space it takes a two-dimensional object (a surface) to create a boundary inside a black hole, in the bulk universe the event horizon of a 4D black hole would be a 3D object — a shape called a hypersphere. When Afshordi's team modeled 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 authors postulate that the 3D universe we live in might be just such a brane — and that we detect the brane's growth as cosmic expansion. 'Astronomers measured that expansion and extrapolated back that the Universe must have begun with a Big Bang — but that is just a mirage,' says Afshordi."
If I understood it correctly they mean that on the other side is a universe with 4 spatial dimensions.
Think of it this way: in a universe with 3 spatial dimensions a black hole has a 2-d surface (shaped roughly like the surface of a sphere) as its event horizon. On the inside of the surface is the black hole. On the outside is the rest of the universe. Generalizing this to a hypothetical universe with 4 spatial dimension, a black hole in such a universe would have a 3-d "surface" surrounding it with the black hole inside of the surface and the rest of the universe outside of it.
By the way, there is already an idea floating around about how the edge of the visible universe seems be a bit like the event horizon of a black hole. Once something has passed the edge of the visible universe it is effectively lost to us, a bit like when something passes the event horizon of a black hole.
What will really cook your noodle is if you calculate the mass of a black hole whos event horizon the size of the visible universe, its within an order of magnitude of the suspected mass of the visible universe (including dark matter.)
A common misconception is that black holes require singularities. Simple thought experiments show it differently.. for example, imagine living in a universe with a mass about that of a black hole that would have an event horizon that is just a little bit smaller than the universe. Now imagine that universe contracting. You can see that as it contracts it will eventually become small enough to form an event horizon without a singularity.
"His name was James Damore."
By the way, there is already an idea floating around about how the edge of the visible universe seems be a bit like the event horizon of a black hole. Once something has passed the edge of the visible universe it is effectively lost to us
Because we can only see things that have sent light back towards us, AND that return light has already reached us. If something is further away from earth, than the distance that light could have possibly travelled back from the object towards earth from the time that the object was at that distance, then by induction: we cannot see the object yet.
Because near the rim of the universe.... the universe is expanding faster than the speed of light; so it's far enough, that light would take longer to travel back to where earth is, than the duration the universe has existed.
Furthemore: since the universe can continue to expand at a rate faster than the speed of light --- the light travelling back towards earth, can never overtake the rate of the universe's expansion, and find its way back to us.
It is kind of like an infinite treadmkill ---- very similar to the concept of a gravitational well that is so deep not even light can escape.
We have an outer rim of our universe expanding so quickly, that not even the very timespace; the spatial dimensions or the passage of time can escape it.