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Are We Living In the Event Horizon Of A 4D Black Hole?

This article is more than 9 years old.

The Big Bang has a lot of problems. For one, the usual laws of physics break down in a singularity. It’s bizarre and chaotic; anything could happen. Which makes cosmologists wonder why it would evolve into something as well-ordered as the universe we see around us. As Niayesh Afshordi put it in Nature last year: “For all physicists know, dragons could have come flying out of the singularity.”

Not if Afshordi, an astrophysicist at the Perimeter Institute for Theoretic Physics in Waterloo, Canada, has anything to do with it.

He and two of his colleagues, University of Waterloo Professor Robert Mann and PhD candidate Razieh Pourhasan, are proposing to get rid of the Big Bang altogether, replacing it instead with that other sort of singularity, a nice, safe, comforting black hole.

We could be living in the 3D event horizon of a 4D black hole (Credit: Wikipedia)

Perhaps the biggest difference between the Big Bang and black holes is that we are protected from the latter by its event horizon. A black hole’s gravity is so powerful that its escape velocity is faster than the speed of light, and since nothing can travel that quickly, nothing gets out of a black hole. We are protected from the mayhem and the break-down of physical laws that take place there by a process sometimes described as "cosmic censorship". The dragons are trapped inside.

Now swap the Big Bang for a black hole.

As Scientific American puts it in its August cover story, what they’re proposing is “The Black Hole at the Beginning of Time”.

Not just any black hole, though. They’re proposing a four-dimensional black hole, made by the collapse of a four-dimensional star.

Where does our universe come in to this? We are, say the authors, living in the three-dimensional event horizon.

The trio start their explanation by recalling Plato’s allegory about the prisoners who spend their whole lives looking at shadows on a wall, unaware that there are three-dimensional objects casting the illusory images. “Their shackles have prevented them from perceiving the true world, a realm with one additional dimension,” they write. “Plato was on to something.”

Our three-dimensional world is just a "brane" in a much larger four-dimensional universe, they argue, using the terminology of string theory.

Their ideas are “firmly grounded in the mathematics that describe space and time”, including holographic tools that allow them to describe events in one set of dimensions, and then transfer them, accurately, to another.

Also, it would solve other problems that plague the current cosmological model, the Lambda Cold Dark Matter paradigm, such as why the universe is so smooth (The four-dimensional universe had already existed for a long time, allowing it to approach equilibrium.)

But most importantly, for the point of view of theoretical science, their proposal makes predictions that can be tested. One of those is that there should be fluctuations in the cosmic microwave background radiation, the echo of the big bang. They admit, however, that this has not been seen in the latest data from the European Space Agency’s Planck observatory.

If they’re right, and that’s a big if, it would provide us with a much deeper understanding of how our universe came to be. However, as the authors acknowledge, that knowledge would come at the price of a new mystery: how the four-dimensional meta-universe got going.

For those with a physics background who want to explore this idea in more depth, the original paper was published in arXiv.