Often times, modern physics will produce a theory that is both elegant and fascinating. Sometimes though, physics produces a theory that is, by its nature, literally mind-boggling.
Last week, a paper published by Niayesh Afshordi, an astrophysicist at the Perimeter Institute for Theoretical Physics in Waterloo, Canada, and his colleagues seeks to throw out the long-accepted Big Bang model for the origin of the universe. The research was based on a 2000 paper written by the physicist Gia Dvali and others.
One of the most difficult problems presented by the classic Big Bang model is that it fails to explain the surprisingly regular temperature found throughout the universe. Almost all of it displays close to the same average temperature, despite the fact that the universe has been around for only 13.7 billion years. This may seem like a long time, but according to what we know about physics, it isn’t long enough for the cosmos to have reached the equalized temperature we see today. The rapid expansion of the early universe might help to explain this, but it is still a hotly debated point.
Another problem, and perhaps the most significant one, is the issue of the singularity. The Big Bang model proposes that the entire universe originated from a single, infinitely dense point, or a singularity. This is all well and good for the theory, but the nature of singularities makes it impossible to know anything about the exact birth of the universe. Before the explosion of this singularity, physics as we know of it today didn’t exist.
Now however, Afshordi and his team have created an alternative explanation. This idea is rooted heavily in the concepts of string theory, particularly branes. The exact nature of a brane is a little difficult to imagine. For simplicity’s sake, it can be thought of as a basic mathematical object which forms the foundational fabric of the universe. Branes exist in any one of nine dimensions of space. In this new theory, our universe exists on a three-dimensional brane, which in turn makes up a part of a larger, four-dimensional “bulk” universe. It would be the same relationship that a two-dimensional plane has with our three-dimensional world
Afshordi and others theorized that in this four dimensional universe, there could very likely be four dimensional stars. These would in turn eventually die, ejecting much of their mass while their interiors collapse into four-dimensional black holes. Now, in our universe, black holes are separated from the rest of reality by the event horizon, a two-dimensional surface surrounding the black hole beyond which no light can escape. In a four-dimensional universe however, the event horizon would be three-dimensional, an object called a “hypersphere”.
According to models run by the team (and for reasons I’m likely incapable of comprehending), when a four dimensional black hole is formed from the collapse of a four dimensional star, the debris originally expelled from the star settles around the three dimensional event horizon to form a three dimensional brane. The models showed that this brane would then begin to expand. The outward growth of the brane is what cosmologists detect as the expansion of our universe.
The fact that the cosmos may have originated from an even in a higher-dimension universe could explain the temperature problem discussed previously. The “bulk” universe that ours originated from could potentially have existed forever, giving the total temperate plenty of time to even out. Since our universe would be an offspring this large one, we would in a sense “inherit” this quality.
The theory does still have its problems however. It doesn’t adequately explain the temperature fluctuations that do exist. These discrepancies are already explained by the Big Bang model, so this new research may have trouble unseating it. Nevertheless, Afshordi and his team are confident that further research will answer these questions. The group is now working on refining the model to make it more robust and accurate. If correct, this new theory would revolutionize our understanding of cosmology (regardless of how mind-bending the concept is).
This research was originally published in Cornell University’s arXic archive. Original reporting of the development was down by Nature News.