Have we been living in “The Matrix” this whole time?
This may sound a little wacky, but there is a long-standing theory that our universe is merely a hologram — an image of a two-dimensional universe projected across the cosmological horizon. What this means is that our universe may actually be flat and only appear to be three-dimensional. This theory is called the Holographic Principle.
Some physicists believe that this theory can solve the contradiction between Einstein’s theory of relativity and quantum mechanics — first presented by Stephen Hawking as the “information paradox.” The paradox states that black holes described by relativity appear to absorb information since nothing can escape the immense gravity, but according to the quantum theory, this is impossible.
In 1997, physicist Juan Maldacena proposed that the holographic principle held for a theoretical space called anti-de Sitter space. Anti-de Sitter space is described as negative space or space curved inward like a saddle — meaning any object thrown on a straight line will eventually return. "Our universe, in contrast, is quite flat —and on astronomic distances, it has positive curvature," says Daniel Grumiller from TU Wien.
Within the theoretical anti-de Sitter space, Maldacena showed that the equations of gravitational theory which has three-dimensions, and the equations of quantum theory with only two-dimensions could be mapped perfectly on to each other. This was a surprising connection, named the correspondence principle, which pointed to a holographic nature of anti-de Sitter space.
Grumiller, however, hypothesized that a correspondence principle could be true for our universe. To test this hypothesis, Grumiller had to calculate quantities in both quantum field theory and relativity theory in flat space to see if the results matched. He decided to see whether the intriguing feature of quantum mechanics — quantum entanglement — could be replicated using relativity theory.
To achieve this, Grumiller, along with Arjun Bagchi, Rudranil Basu and Max Riegler from TU (Wien), looked at the “entropy of entanglement” which describes how entangled a quantum system is. They were able to show that the entropy of entanglement was exactly the same when calculated in quantum field theory and relativity theory for spaces that are flat like our universe.
"This calculation affirms our assumption that the holographic principle can also be realized in flat spaces. It is evidence for the validity of this correspondence in our universe," said Riegler.
"The fact that we can even talk about quantum information and entropy of entanglement in a theory of gravity is astounding in itself, and would hardly have been imaginable only a few years back. That we are now able to use this as a tool to test the validity of the holographic principle, and that this test works out, is quite remarkable," said Grumiller.
There is still a lot of work to be done to determine if we indeed are living within a hologram. For example, if our universe was a hologram, there would exist a limit to the universe’s data storage, just like a computer, and that limit would create measureable “holographic noise.” Physicists are studying this as we speak.
Although there is more and more evidence pointing to the validity of this correspondence principle, what does it all mean? Should we care?
According to Grumiller, “This knowledge won’t impact our everyday lives, in the same way that knowing about the Big Bang or other galaxies does not change our everyday lives. But in the same way that knowing that the universe started with a Big Band has profoundly changed our view of the universe, knowing that the universe is like a big hologram is a profound insight.”
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