Beyond Singularity : A Glimpse of Loop quantum gravity !
Our first glimpses into the physics that exist near the center of a black hole are being made possible using “loop quantum gravity”(this a theory of quantum gravity,merging quantum mechanics and general relativity, making it a possible theory, “theory of everything”)—a theory that uses quantum mechanics to extend gravitational physics beyond Einstein’s theory of general relativity. Its goal is to unify gravity in a common framework with other three(no3) fundamental forces of nature. Loop quantum gravity, originated at Penn State and subsequently developed by a large number of scientists worldwide, is opening up a new paradigm in modern physics. The theory has emerged as a leading candidate to analyze extreme cosmological and astrophysical phenomena in parts of the universe, like black holes, where the equations of general relativity cease to be useful.
The best theory of gravity that we have till yet is general relativity, but it has limitations. “For example, general relativity predicts that there are places in the universe where gravity becomes infinite and space-time simply ends. We refer to these places as ‘singularities’. But even Einstein agreed that this limitation of general relativity results from the fact that it ignores quantum mechanics.”
At the center of a black hole the gravity is so strong that, according to general relativity, space-time
becomes so extremely curved that ultimately the curvature becomes infinite. This results in space-time
having a jagged edge, beyond which the distortion of rules of physics begins—the singularity. Another
example of a singularity is the Big Bang. Asking what happened before the Big Bang is a meaningless
question in general relativity, because space-time ends, and there is no before. But modifications in Einstein’s
equations that incorporated quantum mechanics through loop quantum gravity allowed researchers to extend physics beyond the Big Bang and make new predictions
The basis of loop quantum gravity is Einstein’s discovery that the geometry of space-time is not just a stage on which cosmological events are acted out, but it is itself a physical entity that can bent according to the events acted on it. As a physical entity the geometry of space-time is made up of some fundamental units, just as matter is made up of atoms. These units of geometry—called “quantum excitations”—are orders of magnitude smaller than we can detect with today’s technology, but we have precise quantum equations that predict their behavior, and one of the best places to look for their effects is at the center of a black hole. According to general relativity, at the center of a black hole gravity becomes infinite so everything that goes in, including the information needed for physical calculations, is lost. This leads to the ‘information paradox’ that theoretical physicists have been grappling with for over 40 years. However, the quantum corrections
of loop quantum gravity allow for a repulsive force that can overwhelm even the strongest pull of gravity and
therefore physics can continue to exist. This indicates that there is no loss of information at the center of a
blackhole, which the researchers are now pursuing.
Interestingly, even though loop quantum gravity continues to work where general relativity breaks down—black hole’s singularity, the Big Bang—its predictions match those of general relativity quite precisely under less extreme circumstances away from the singularity. “It is highly contradicting to achieve both” Indeed, a number of investigators have explored the quantum nature of the black hole’s singularity over the past decade, but either the singularity prevailed or the mechanisms that resolved it unleashed unnatural effects.
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