Stephen Hawking says black holes don’t exist

[Buster's Uncle]

Stephen Hawking says black holes don’t exist
The Sideshow
By Eric Pfeiffer  1 hour ago
 


Do black holes exist? Not exactly in the way we think says Stephen Hawking (AFP)


Black holes are the source of endless fascinating and speculation. Do they hold the secrets of the universe and perhaps even the key to time travel itself?

We may never know the answers to those questions because famed theoretical physicist Stephen Hawking says black holes don’t actually exist. At least not in the way we’ve been taught to think about them.

"The absence of event horizons mean that there are no black holes — in the sense of regimes from which light can't escape to infinity," Hawking writes in a new paper entitled, "Information Preservation and Weather Forecasting for Black Holes"

So, what does that mean exactly?

Well, what Hawking is saying is that he doesn’t believe Event Horizons, gravitational traps from which even light cannot escape, actually exist.

It’s a “ mind-bending theory ” as New Scientist puts it, which ensures the debate will continue 40 years after Hawking first brought the concept of black holes to the public.

In his lecture “Into a Black Hole,” Hawking described how an Event Horizon works:

“Falling through the event horizon, is a bit like going over Niagra Falls in a canoe. If you are above the falls, you can get away if you paddle fast enough, but once you are over the edge, you are lost.There's no way back. As you get nearer the falls, the current gets faster. This means it pulls harder on the front of the canoe, than the back. there's a danger that the canoe will be pulled apart. It is the same with black holes.”

But now, Hawking says Event Horizons don’t exist. However, he does say that “Apparent Horizons” could exist, meaning that light technically could escape from the deep gravitational bull of a black hole. Put simply, an Apparent Horizon would only temporarily hold light and information, eventually releasing them back into space.

Though, “eventually” is a pretty relative term when we’re discussing the nature of spacetime.

“The picture Hawking gives sounds reasonable,” Don Page, a physicist and expert on black holes at the University of Alberta in Edmonton, Canada told Nature. “You could say that it is radical to propose there’s no event horizon. But these are highly quantum conditions, and there’s ambiguity about what space-time even is, let alone whether there is a definite region that can be marked as an event horizon.”

Still  , that doesn’t mean astronauts will be lining up to dive into a black hole anytime soon  . As Nature puts it, an Apparent Hoizon wouldn’t burn you to a crisp like an Event Horizon would but it wouldn’t leave you in “good shape” either. Any information or object escaping from a black hole in this scenario would be “pretty scrambled” in Hawking’s own words.



An artist's illustration of what an up-close view of a black hole looks like (AFP)


http://news.yahoo.com/blogs/sideshow/stephen-hawking-says-black-holes-don-t-exist-012107567.html

[Buster's Uncle]

Stephen Hawking: There Are No Black Holes
by Ian O'Neill, Discovery News   |   January 25, 2014 09:02am ET


 
  This annotated image labels several features in the simulation, including the event horizon of the black hole.  Credit: NASA's Goddard Space Flight Center/J. Schnittman, J. Krolik (JHU) and S. Noble (RIT)



On reading a new paper by Stephen Hawking that appeared online this week, you would have been forgiven in thinking the world-renowned British physicist was spoofing us. Hawking's unpublished work — titled "Information Preservation and Weather Forecasting for Black Holes" and uploaded to the arXiv preprint service — declares that "there are no black holes."

Keep in mind that Hawking's bedrock theory of evaporating black holes revolutionized our understanding that the gravitational behemoths are not immortal; through a quantum quirk they leak particles (and therefore mass) via "Hawking radiation" over time. What's more, astronomers are finding new and exciting ways to detect black holes — they are even working on an interferometer network that may, soon, be able to directly image a black hole's event horizon!


 
 Professor Stephen Hawking speaks about "Why We Should Go into Space" for the NASA Lecture Series, April 21, 2008.  Credit: NASA/Paul Alers


Has Hawking changed his mind? Are black holes merely a figment of our collective imaginations? Are all those crank theories about "alternative" theories of the Cosmos true?!

Fortunately not.

Stephen Hawking hasn't changed his mind about the whole black hole thing, but he has thrown a complex physics paradox into the limelight, one that has been gnawing at the heart of theoretical physics for the last 18 months.


 
  Black holes are strange regions where gravity is strong enough to bend light, warp space and distort time.  Credit: Karl Tate, SPACE.com contributor


 Black Hole Fight Club

It all boils down to a conflict between two fundamental ideas in physics that control the very fabric of our Universe; the clash of Einstein's general relativity and quantum dynamics. And it just so happens that the extreme environment in and around a black hole makes for the perfect "fight club" for the two theories to duke it out. But what's the first rule of the black hole fight club? Don't talk about the firewall, lest you get sucked into an argument with a theoretical physicist.

At a California Institute of Technology (Caltech) lecture in April 2013, Hawking and other prominent theoretical physicists had an opportunity to describe the problem at hand. Caltech's Kip Thorne, for example, described the firewall paradox as "a burning issue in theoretical physics."

The very basis of this burning issue is the thing that makes black holes black — the event horizon. In its most basic form, the event horizon of a black hole is the point at which even light cannot escape the gravitational clutches of the massive black hole singularity. If light cannot escape, it stands to reason that it will appear as a black sphere in space. It is a cosmic one-way street: everything goes in, nothing comes out.


 An Unlucky Astronaut

In the general relativity universe, for an astronaut who had the misfortune to fall toward a black hole, he or she wouldn't notice anything untoward as they passed across the event horizon. It would be a fairly peaceful event, no drama. "Although later on you're doomed and you’ll encounter very strong gravitational forces that will pull you apart," noted Caltech physicist John Preskill at the 2013 Caltech event. [The Strangest Black Holes in the Universe]

However, the quantum universe contradicts this "no drama" event horizon idea as predicted by general relativity.

In 2012, a group of physicists headed by Joseph Polchinski of the University of California in Santa Barbara revealed their finding that if black holes truly do not destroy information — a standpoint that Hawking himself reluctantly advocates — and that information can escape from the black hole through Hawking radiation, there must be a raging inferno just inside the event horizon they dub the "firewall."

In this case, rather than falling into a "no drama" event horizon, our unlucky astronaut gets burnt to a crisp before getting ripped apart by tidal shear. This is the very antithesis of "no drama" and, therefore, a paradox.

This apparent conflict between what general relativity predicts and what quantum dynamics predicts — two very established fields in physics — is precisely what theoretical physicists are trying to understand. This appears to be yet another situation where gravity and quantum dynamics don’t play nice, the solution of which may transform the way we view the Universe.


 Apparent Horizons

So, when Hawking, one of the key players in the great firewall debate, writes a short paper on the topic (regardless of whether or not it has been published) the world takes note.

Hawking’s solution to the paradox removes the black hole’s event horizon, thereby removing the paradox; no event horizon, no firewall. But we're told all black holes have event horizons — the line you cannot cross or be forever lost inside the black hole — what gives?

Hawking thinks that the idea behind the event horizon needs to be reworked. Rather than the event horizon being a definite line beyond which even light cannot escape, Hawking invokes an "apparent horizon" that changes shape according to quantum fluctuations inside the black hole — it's almost like a "grey area" for extreme physics. An apparent horizon wouldn't violate either general relativity or quantum dynamics if the region just beyond the apparent horizon is a tangled, chaotic mess of information.

"Thus, like weather forecasting on Earth, information will effectively be lost, although there would be no loss of unitarity," writes Hawking. This basically means that although the information can escape from the black hole, its chaotic nature ensures it cannot be interpreted, sidestepping the firewall paradox all together.

Needless to say, this paper has done little to convince Polchinski. "It almost sounds like (Hawking) is replacing the firewall with a chaos-wall, which could be the same thing," he told New Scientist.

Much of the theoretical debate is hard to fathom and the result of calculations of physical events that we cannot possibly experience in our day to day lives. But don't mistake this particular debate as solely a high-brow argument in the theoretical physics community. Its foundations are rooted in the growing discomfort we are feeling with the mismatch of general relativity and quantum dynamics (particularly what role gravity plays in the quantum world), a problem that cannot be solved with our current understanding of the universe.

It is, after all, these science problems that we build multi-billion dollar particle accelerators for.


http://www.space.com/24418-stephen-hawking-no-black-holes.html

[Buster's Uncle]

Black holes should be redefined, says Stephen Hawking in new paper
By Adrianne Jeffries on January 25, 2014 03:34 pm






Black holes don't actually exist in the way we traditionally think of them, renowned physicist Stephen Hawking has proposed in a short but potentially revolutionary paper.

Classical theory holds that no energy or information can ever escape a black hole, but the principles of quantum physics suggest it can. This contradiction has been the subject of debate among physicists for years. In the paper, "Information Preservation and Weather Forecasting for Black Holes," Dr. Hawking proposes a solution to this paradox: instead of devouring information and energy permanently, black holes release it back into the universe in a garbled, unrecognizable form.

Traditionally, black holes were thought to contain an "event horizon," a sharp boundary beyond which even light cannot escape the gravitational pull of the black hole's infinitely dense core. Now Dr. Hawking proposes a shifting boundary, the "apparent" horizon, which fluctuates according to quantum effects.

"There are no black holes," the paper concludes

Among other implications, this new theory would have consequences for any astronaut who happened to fall into a black hole. According to quantum physics, the unlucky astronaut would immediately burn up in a "firewall" of intense radiation. Relativity, however, holds that the astronaut would be gradually pulled and stretched like pasta until being crushed at the black hole's core. Hawking's theory dispenses with the paradox because without an event horizon, there would be no firewall.

"There are no black holes," the paper concludes, "in the sense of regimes from which light can't escape to infinity."

Other physicists are already challenging Hawking's theory, which has not been peer-reviewed yet. "The idea that there are no points from which you cannot escape a black hole is in some ways an even more radical and problematic suggestion than the existence of firewalls," says Raphael Bousso, a theoretical physicist at Berkeley.


http://www.theverge.com/2014/1/25/5344544/stephen-hawking-says-there-are-no-black-holes