Our understanding of black holes, time and the mysterious dark energy
that dominates the universe could be revolutionised, as new University of
Sheffield research helps unravel the mysteries of the cosmos.
Black holes – areas of space where
gravity is so strong that not even light can escape – have long been objects of
fascination, with astrophysicists, theoretical physicists and others dedicating
their lives to revealing their secrets. This fascination with the unknown has
inspired numerous writers and filmmakers, with novels and films such as 2001: A
Space Odyssey, The Martian and Interstellar exploring these enigmatic objects’
hold on our collective imagination.
According to Einstein’s Theory of
General Relativity, anyone trapped inside a black hole would fall towards its
centre and be destroyed by immense gravitational forces. This centre, known as
a singularity, is the point where the matter of a giant star, which is believed
to have collapsed to form the black hole, is crushed down into an
infinitesimally tiny point. At this singularity, our understanding of physics
and time breaks down.
Using the laws of quantum mechanics, a
fundamental theory describing the nature of the universe at the level of atoms
and even smaller particles, the new study proposes a radically different
theoretical standpoint where, rather than a singularity signifying the end, it
could represent a new beginning.
The new paper entitled ‘Black Hole Singularity Resolution in Unimodular Gravity
from Unitarity’, published on
11 March in the scientific journal Physical Review Letters, aims to illustrate
the point where our current grasp of physics and time falters.
While black holes are often described as
sucking everything, including time, into a point of nothingness, in the paper,
white holes are theorised to act in reverse, ejecting matter, energy and time
back into the universe.
The study uses a simplified, theoretical
model of a black hole, known as a planar black hole. Unlike typical black
holes, which have a spherical shape, a planar black hole’s boundary is a flat,
two-dimensional surface. The researchers’ ongoing work suggests that the same
mechanism could also apply to a typical black hole.
“It has long been a question as to
whether quantum mechanics can change our understanding of black holes and give
us insights into their true nature,” said Dr Steffen Gielen, from the University of
Sheffield’s School of Mathematical and Physical Sciences, who co-wrote the
paper with Lucía Menéndez-Pidal from Complutense University of Madrid.
“In quantum mechanics, time as we
understand it cannot end as systems perpetually change and evolve.”
The scientists’ findings demonstrate
how, using the laws of quantum mechanics, the black hole singularity is
replaced by a region of large quantum fluctuations – tiny, temporary changes in
the energy of space – where space and time do not end. Instead, space and time
transition into a new phase called a white hole – a theoretical region of space
thought to function in the opposite way to a black hole. As such, a white hole
could be where time begins.
“While time is, in general, thought to
be relative to the observer, in our research time is derived from the
mysterious dark energy which permeates the entire universe,” Dr Gielen
continued.
“We propose that time is measured by the
dark energy that is everywhere in the Universe, and responsible for its current
expansion. This is the pivotal new idea that allows us to grasp the phenomena
occurring within a black hole.”
Dark energy is a mysterious, theoretical
force that scientists believe drives the accelerating expansion of the
universe. The new study uses dark energy almost as a point of reference, with
energy and time as complementary ideas that can be measured against one
another.
Tantalisingly, the theory that what we
perceive as a singularity is actually a beginning suggests the existence of
something even more enigmatic on the other side of a white hole.
“Hypothetically you could have an
observer – a hypothetical entity – go through the black hole, through what we
think of as a singularity and emerge on the other side of the white hole. It’s
a highly abstract notion of an observer but it could happen, in theory,” Dr
Gielen added.
Beyond such theoretical musings, the
suggestion of a profound connection between the nature of time at the most
fundamental level and the mysterious dark energy that governs the cosmos will
be explored further in the months and years ahead.
The new research also suggests novel
approaches to reconciling gravity and quantum mechanics, potentially paving the
way for groundbreaking new fundamental theories and breakthroughs in our
understanding of the universe.
Journal article: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.134.101501
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