A Two-Dimensional Boundary
New research suggests that the universe may have been a hologram at one point in time, specifically a few hundred thousand years after the Big Bang. The study, published in the journal Physical Review Letters, is the latest research on the "holographic principle," which suggests that the laws of physics can apply to the universe as a two-dimensional plane.
“We are proposing using this holographic universe, which is a very different model of the Big Bang than the popularly accepted one that relies on gravity and inflation,” said lead author Niayesh Afshordi, professor of physics and astronomy at the University of Waterloo and Perimeter Institute. “Each of these models makes distinct predictions that we can test as we refine our data and improve our theoretical understanding – all within the next five years.”
The theory suggests that the volume of space appears three-dimensional, but is actually encoded on a two-dimensional boundary or an observer-dependent horizon that requires one less dimension than it appears. In short, we see it as three-dimensional, but it is projected from a two-dimensional source, similar to how a hologram screen works.
"The idea is similar to that of ordinary holograms, where a three-dimensional image is encoded in a two-dimensional surface, such as in the hologram on a credit card," explained researcher Kostas Skenderis from the University of Southampton. "However, this time, the entire universe is encoded."
Making Sense of Cosmic Inflation
The researchers arrived at this conclusion after observing irregularities in the cosmic microwave background — the Big Bang's remnant. The team used a model with one time and two space dimensions. Actual data from the universe, including cosmic microwave background observations, were then plugged into the model. The researchers saw that the two fit perfectly, but only if the universe is no more than 10 degrees wide.
"I would say you don’t live in a hologram, but you could have come out of a hologram," Afshordi told Gizmodo. "[In 2017], there are definitely three dimensions."
While many accept the cosmic inflation that came after the Big Bang, our understanding of physics – including current general relativity and quantum mechanics theories – doesn't work with what we observe. The fundamental laws of physics are incapable of explaining how the universe as we know it, with all its contents, could've fit in a small package that exponentially expanded.
This is where Afshordi's research and the holographic model come in. These could lead to new theories about the Big Bang and a functioning theory of quantum gravity — a theory that meshes quantum mechanics with Einstein's theory of gravity. “The key to understanding quantum gravity is understanding field theory in one lower dimension,” Afshordi says. “Holography is like a Rosetta Stone, translating between known theories of quantum fields without gravity and the uncharted territory of quantum gravity itself.”
The question remains, though: how did the universe transition from 2D to 3D? Further study is needed to explain this.