Black holes – Into the unknown?

Lost in the abyss, deep endless space, interstellar travel, an enigmatic portal to another dimension… It begins here in science-fiction, but a black hole translates far beyond mere fantasy. With a history of contention, the answer to a debated phenomenon becomes closer and closer: what is a black hole and what occurs within?

By Sarah Marshall

Current Understanding
A black hole is a region in outer space containing a vast amount of matter with an incredibly strong gravitational field, so strong that not even light can escape. A medium-sized black hole may have a mass 20 times that of the sun, yet fit inside a sphere with a diameter of approximately 16 km (roughly the length of the Stockholm tunnelbana red line from Norsborg to Ropsten).

A black hole forms when an object reaches a critical point and collapses under its own gravity. For example, when a large star has exhausted all energy and can no longer sustain itself, it collapses and the gravitational force overwhelms all other forces, creating a black hole. Proposed in 1783 by astronomer John Mitchell, it was not until much later in the 1970s that the first black hole was observed – or at least its impacts on the surrounding environment, given that the darkness cannot be directly observed.

Relativity versus Quantum Theory
So, what actually happens inside a black hole? This is something that physicists have been tackling for decades. Einstein’s Theory of Relativity (published as The Foundation of the General Theory of Relativity in 1916) describes the formation and behaviour of black holes, while quantum theory, which underpins modern physics, states that no information in the Universe can ever be lost. Professor Stephen Hawking from the University of Cambridge applied quantum theory to black holes, and in 1974 found that heat radiation can escape. These small emissions of radiation, appropriately termed Hawking Radiation, could cause the black hole to shrink and ultimately evaporate. The resultant situation is an application of two contradictory but fundamental theories, causing 40 years of ongoing scientific debate.

Leading Physicists Seek Solutions
Over the last 5 years particularly, there have been assertions that in fact not only radiation but also information escapes a black hole. As the thinking became more and more difficult to follow, the search for consensus was needed. In August of this year, physicist Professor Laura Mersini-Houghton from the University of North Carolina coordinated a one-week conference held at KTH Royal Institute of Technology Stockholm bringing together 32 of the world’s leading physicists. Arranged in conjunction with Nordita and the University of Cambridge, the conference provided a unique opportunity to seek a solution to this contentious and paradoxical question among physicists.

Where are we now?
And the result? Hawking proposed that black holes don’t actually envelope and lose physical information. Hawking has suggested that a form of 2D hologram is created, storing the information within the membrane of the black hole. Hawking said, “The information about ingoing particles is returned, but in a chaotic and useless form. This resolves the information paradox. But for all practical purposes, the information is lost.” This theory resonates with that posed by the winner of the 1999 Nobel Prize in Physics, Professor Gerard ‘t Hooft of Utrecht University. Information that enters the black hole is in fact not lost, therefore does not violate the fundamental principle of quantum  theory.

Has science clarified misconceptions among the general public? Perhaps not quite yet, but the leading physicists are continuing to strive for answers and consensus. As Professor Stephen Hawking said during his public lecture in Stockholm prior to the conference, “If you feel you are in a black hole, don’t give up. There’s a way out.” •

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