The general theory of relativity, or simply general relativity, has been touted as the biggest scientific breakthrough of the 20th century. Published by Albert Einstein in 1915, the theory changed our understanding of Newtonian gravity as a force between bodies into a warping of the very fabric of space and time – spacetime. But the theory is not entirely foolproof and there are situations, particularly in the world of black holes and quantum physics, where cracks start to appear.
According to the principles of general relativity, black holes ought to be completely inert objects with singularities at their cores where the known laws of physics break down.
Professor Stephen Hawking was the first to put a dent in that model in the early Seventies when he revealed his Hawking radiation theory.
Based on his theoretical calculations, quantum effects near a black hole’s event horizon – the point of no return – allow for thermal radiation to escape into space.
The process is also known as “blackbody radiation” and demonstrates, in essence, that black holes are not entirely black.
Einstein even famously railed against the “topsy turvy” world of quantum physics, believing it was too messy and unprincipled.
Without a way to combine general relativity and quantum mechanics, the Sussex researchers used so-called effective field theory (EFT) to study the black hole singularity.
The theory stipulates gravity at the quantum level is very weak, which allows for some calculations that otherwise fall apart in the face of strong quantum gravity.
Dr Calmet said: “If you consider black holes within only general relativity, one can show that they have a singularity in their centres where the laws of physics as we know them must break down.
“It is hoped that when quantum field theory is incorporated into general relativity, we might be able to find a new description of black holes.”
With the aid of EFT, Dr Calmet and his colleague were able to find mathematical evidence of pressure within a black hole.
According to astrophysicist Paul Sutter, this is the same type of pressure hot air exerts on the inside of a balloon.
However, because the model only works with weak quantum gravity, while neglecting strong gravity, it cannot be used to completely explain black hole behaviour.
Dr Calmet added: “Our work is a step in this direction, and although the pressure exerted by the black hole that we were studying is tiny, the fact that it is present opens up multiple new possibilities, spanning the study of astrophysics, particle physics and quantum physics.”