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Science in the News: April 18

Carson Kopeke, Science Columnist
April 23, 2014 • 595 views

Do black holes actually exist?

According to the latest theories of renowned theoretical physicist Stephen Hawking, the answer to this question is “sort of, and most of the time.” Let me explain.

Black Holes have received much critical thought over the last century, though they were first hypothesized in the 18th century by an English and a French scientist. A black hole is a region of extremely dense matter which exerts so much gravity on the space around it that it warps space-time. A black hole has enough power to bend and pull even light into its mass.

According to Albert Einstein and his peers, black holes have a boundary called an event horizon, a point of no return. Up to the event horizon, space seems indistinguishable from the rest of the universe. However, if something were to pass this invisible line, it would be sucked into the center of the hole, called the “singularity,” stretching out like spaghetti in the process. These scientists believed that nothing escapes the dense mass, not even light (hence the name “black hole”).

Toward the end of the 20th century, however, Stephen Hawking declared that black holes are not as clingy as they previously seemed and do in fact release small amounts of their contents in the form of radiation (light). His argument revolutionized the study of black holes, since it implies that black holes can evaporate as well as form. They need not be permanent fixtures of the universe. If nothing new were to feed them, they could feasibly dissolve into space.

Since that time, astrophysicists have presented many new theories about event horizons and information theory. Some hypothesize that information, in the form of matter, is conserved in black holes according to the law of the conservation of mass, while others argue that black holes throw their contents into perpetual chaos. An interesting theory newly published in 2013 presents the idea that black holes emit significant radiation up to the point of the event horizon. They have dubbed this radiation a “firewall” because it incinerates anything that crosses the event horizon prior to being sucked into singularity.

This past January, Hawking published another paper that addresses firewalls, the information paradox and event horizons. Primarily, the paper rejects the firewall theory, but Hawking also calls into question the fundamental concept of the event horizon and the preservation of information.

Hawking works from the assumption that the CPT theorem must hold (an exact symmetry of Charge conjugation, Parity transformation and Time reversal that holds for all physical phenomena). In other words, firewalls seem to break important rules of theoretical physics, as do event horizons. In their place, Hawking proposes the existence of an “apparent horizon” which resembles an event horizon but is more flexible and is temporary rather than fixed in space-time. He asserts that black holes should actually be redefined as “metastable bound states of the gravitation field” since they release radiation just as they absorb it. In fact, Hawking believes black holes to be in constant flux between evaporation and condensation.

As for the information paradox, Hawking suggests that black holes take in information, scramble it through chaotic gravitational collapse and release it in scrambled form, resulting in ineffective information loss. He humorously compares the process to weather forecasting (sorry, Paul Douglas). Nevertheless, Hawking has received wide-ranging criticism for his new ideas and his paper has yet to be peer reviewed.

The term “black hole” is a misnomer, since they are neither holes nor black (i.e. invisible). But for now, the concept definitively exists … though it will surely continue to evolve.

 

koepke@stolaf.edu

 
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