General relativity is one of the greatest ideas in human history. Relativity and quantum mechanics are the cornerstones of modern physics, and they are used from telecommunication to computers and smartphones.
Unfortunately, relativity and quantum mechanics don’t play well together. For that reason, theoretical physicists are searching for a theory that can unify them: the theory of everything. To do so, they test the two theories to their limits, looking for when their fundamental laws are broken, and now a new piece of research has found a very interesting violation of general relativity.
Researchers from Cambridge University and Queen Mary University looked at an interesting scenario in general relativity and discovered that it actually breaks. They used a supercomputer to model a five-dimensional ring-shaped black hole and discovered that the black hole evolved into a naked singularity, which violates relativity. The findings are published in Physics Review Letters.
Singularities such as black holes are objects of infinite density, and according to the laws of physics they are allowed to exist only if they are surrounded by an event horizon, a surface that separates them from the rest of the universe. Mathematically, you cannot have a “naked” singularity (existing outside of an event horizon) in our four-dimensional universe. This is aptly known as the cosmic censorship conjecture.
"As long as singularities stay hidden behind an event horizon, they do not cause trouble and general relativity holds – the 'cosmic censorship conjecture' says that this is always the case,"study coauthor Markus Kunesch, a PhD student at Cambridge's Department of Applied Mathematics and Theoretical Physics (DAMTP), said in a statement.
"As long as the cosmic censorship conjecture is valid, we can safely predict the future outside of black holes. Because ultimately, what we're trying to do in physics is to predict the future given knowledge about the state of the universe now."
The ring black hole as seen in three dimensions. Pau Figueras, Markus Kunesch, and Saran Tunyasuvunakool
Cosmic censorship conjecture is believed to hold for our universe, but the results question what is so special about a universe with three space dimensions and a time dimension. Also, possible theories of everything like quantum gravity and string theories require as many as 11 dimensions so it is important to investigate the limits of our current theories. In this scenario, the fifth dimension is a random extra dimension in space.
"The better we get at simulating Einstein's theory of gravity in higher dimensions, the easier it will be for us to help with advancing new computational techniques – we're pushing the limits of what you can do on a computer when it comes to Einstein's theory," said coauthor Saran Tunyasuvunakool. "But if cosmic censorship doesn't hold in higher dimensions, then maybe we need to look at what's so special about a four-dimensional universe that means it does hold."