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This artist's concept illustrates a supermassive black hole with millions to billions times the mass of our sun. Supermassive black holes are enormously dense objects buried at the hearts of galaxies.

This artist's concept illustrates a supermassive black hole, which are enormously dense objects buried at the hearts of galaxies.

ILLUSTRATION BY NASA/JPL/CALTECH  

Charles Q. Choi

for National Geographic

Published January 27, 2014

Black holes do not exist—at least, not as we know them, says renowned physicist Stephen Hawking, potentially provoking a rethink of one of space's most mysterious objects.

A new study from Hawking also says that black holes may not possess "firewalls," destructive belts of radiation that some researchers have proposed would incinerate anything that passes through them but others scientists deem an impossibility.

(Editor's note: Watch for our feature "The Truth About Black Holes" in the March issue of National Geographic magazine, out February 15.)

The conventional view of black holes posits that their gravitational pull is so powerful that nothing can escape from them—not even light, which is why they're called black holes. The boundary past which there is supposedly no return is known as the event horizon.

In this conception, all information about anything that ventures past a black hole's event horizon is destroyed. On the other hand, quantum physics, the best description so far of how the universe behaves on a subatomic level, suggests that information cannot ever be destroyed, leading to a fundamental conflict in theory.

No Event Horizons

Now Hawking is suggesting a resolution to the paradox: Black holes do not possess event horizons after all, so they do not destroy information.

"The absence of event horizons means that there are no black holes, in the sense of regimes from which light can't escape," Hawking wrote in a paper he posted online on January 22. The paper was based on a talk he gave last August at a workshop at the Kavli Institute for Theoretical Physics in Santa Barbara, California.

Instead, Hawking proposes that black holes possess "apparent horizons" that only temporarily entrap matter and energy that can eventually reemerge as radiation. This outgoing radiation possesses all the original information about what fell into the black hole, although in radically different form. Since the outgoing information is scrambled, Hawking writes, there's no practical way to reconstruct anything that fell in based on what comes out. The scrambling occurs because the apparent horizon is chaotic in nature, kind of like weather on Earth.

We can't reconstruct what an object that fell into a black hole was like based on information leaking from it, Hawking writes, just as "one can't predict the weather more than a few days in advance."

Firewalls Removed

Hawking's reasoning against event horizons also seems to eliminate so-called firewalls, which are searing zones of intense radiation that some scientists recently (and controversially) suggested may exist at or near event horizons.

To grasp the significance of this revision, it helps to know that Hawking revealed decades ago that black holes are not perfectly "black." Instead, they emit radiation just beyond their event horizons, the energy of their gravitational fields causing pairs of particles to pop into existence in the surrounding vacuum.

Over time, generating this so-called Hawking radiation makes black holes lose mass—or even completely evaporate.

According to this theory, the pairs of particles created around black holes should be entangled with each other. This means the behavior of each pair's particles is connected, regardless of distance. One member of each pair falls into the black hole while the other escapes.

But recent analyses suggest that each particle leaving a black hole must also be entangled with every outgoing particle that has already left. This runs head-on into a well-tested principle of quantum physics stating that entanglement is always "monogamous," meaning two particles, and only two, are paired from the time of their creation.

Since no particle can have two kinds of entanglement at the same time—one pairing it with another particle at the time of its origin, and one pairing it with all other particles that have left a black hole—one of those entanglements theoretically must get uncoupled, releasing vast amounts of energy and generating a firewall.

Firewalls obey quantum physics, solving the conundrum black holes pose regarding entanglement. But they pose another problem by contradicting Einstein's well-tested "equivalence principle," which implies that crossing a black hole's event horizon should be an unremarkable event. A hypothetical astronaut passing across an event horizon would not even be aware of the transit. If there were a firewall, however, the astronaut would be instantly incinerated. Since that violates Einstein's principle, Hawking and others have sought to prove that firewalls are impossible.

"It almost sounds like he is replacing the firewall with a chaos-wall," said Kavli Institute physicist Joe Polchinski, who did not participate in Hawking's work.

Open Questions

Although quantum physicist Seth Lloyd of the Massachusetts Institute of Technology felt Hawking's idea was a good way to avoid firewalls, he said it doesn't really address the problems that firewalls raise.

"I would caution against any belief that Hawking has come up with a dramatic new solution answering all questions regarding black holes," said theoretical physicist Sean Carroll at the California Institute of Technology, who did not participate in this study. "These problems are very far from being resolved."

Theoretical physicist Leonard Susskind at Stanford University in California, who also did not take part in Hawking's research, suggests there may be another solution to the conundrums that black holes pose. For instance, work by Susskind and his colleague Juan Maldacena hint that entanglement might be linked to wormholes: shortcuts that can in theory connect distant points in space and time. This line of thought might serve as the foundation for research that could solve the firewall controversy, Susskind said.

Theoretical physicist Don Page at the University of Alberta in Edmonton, Canada, noted that there will be no way to find evidence to support Hawking's idea in the immediate future. Astronomers will not be able to detect any difference in the behavior of black holes from what they have already observed.

Nevertheless, Hawking's new proposal "might lead to a more complete theory regarding quantum gravity that makes other predictions that are testable," Page said.

Carroll plans to keep an eye on Hawking in the days ahead: "It's very plausible Hawking has a much better argument that he hasn't yet gotten down on paper."

Follow Charles Q. Choi on Twitter and Google+.

73 comments
Achraf Almouloudi
Achraf Almouloudi

In my opinion, we can't deny the existence of the event horizon because if we did, then we'd be left with the "singularity" alone, in the universe, which is the point where, as we believe, the point in space where the mass is infinite.

So, if the mass is infinite, how small or large that "singularity" would be? What's its shape? At which distance it starts to affect other particles? Is the observable universe by itself just a singularity?

Many other questions will arise that are solved by "believing" that each black hole does actually have an event horizon.

Roger Jones
Roger Jones

hi i believe that black holes being as dense as they are, that the immense gravity actually tares or rips space sending matter via subspace (or some unknown region of spacetime) spewing it out from the quasars at near speed of light .since matter and light (which has mass because it is energy. E=mc2) is being consumed faster than light can travel and the ejection at the quasars isnt quite the speed of light it would account for black holes growing since more is being consumed than expelled(...lol i know my theory is probably not right) however please comment

Noel Francis
Noel Francis

When escaping the influence of black holes, does that mean we are to completely deny them... (their existence, or reasonable constitution?) Apparently, they're made outta star stuff right, just like us? 

From my point of view, as the number of such entities increase in size and/or complexity, the number of avenues of escape them go down. That, as simply as I can say it, means the universe is shrinking. At what point are we to realize that there's no escaping that fact, Big Bang II ...the second derivative ?

Andrew Planet
Andrew Planet

Does that mean that a black hole is only a black hole relative to the observable part of the electromagnetic spectrum?  There being such a thing as Hawking radiation, if there is, I mean?

robert cobb
robert cobb

a black hole is like a wood stove, once you start it you have to feed it all the time to get it going, their is never any ashes cause it doesn't have a inside, it just feeds on what is in front of it. like a stove  has a flu pipe to discard un use heat, a black hole would work the same way.

Luis Garcia-Bunuel
Luis Garcia-Bunuel

Among the possibilities, could dark matter be related to inaccessible parallel universes emanating from the black holes of our own Universe?

Joao Pimentel
Joao Pimentel

It is interesting to (re-)read this article in light of some recent ones about Bill Wootter's idea of the u-bit. One of the possible consequences of the u-bit is that entanglement is not limited to two particles at all. That considered, some of the lines of thought presented here would probably have different conclusions.

Luis Garcia-Bunuel
Luis Garcia-Bunuel

@Luis Garcia-Bunuel

I have no backing  for my previous statement.. Just believe that our vision of the Universe is limited, and I think that "our Universe" is a portion of a "Multiverse" beyond our grasp. If one can conceive unknown dimensions, perhaps those unknown universes are created from black holes in our own Universe

Travis Stevens
Travis Stevens

oddly enough, this article got me thinking... stars are giant nuclear fusion events in space in the middle of a solar system... what if black holes are just giant fission events in space out in the middle of the chaotic swirl of more stable energy out-put??...

Luis Garcia-Bunuel
Luis Garcia-Bunuel

I believe there is Multiverse. Each black hole represents a Big Bang generating another universe in another dimension that we cannot perceive nor even conceive.

Luis Garcia-Bunuel
Luis Garcia-Bunuel

I believe there is Multiverse. Each black hole represents a Big Bang generating another universe in another dimension that we cannot perceive or even conceive.

bsrry stanley
bsrry stanley

So there are no black holes - as the Tempo Field Theory of Frank Atkinson predicts.

What will it take for the scientific community to do a critical review of his work?

Barry Stanley

Jorge Almaguer
Jorge Almaguer

Hawking is GOD. Oh wait a minute, he says there is no GOD. Never mind. 

Ed Lien
Ed Lien

perhaps to have a full view of the topology of the kerr metric observer has to take into consideration of non locality and both past & future state given the position of the event horizon is not locally determined but is a function of the future( or even past?) of the spacetime. 


ion simple words, the information may not be lost but transcended across past-now-future which we only observed the present state as chaotic?


http://arxiv.org/pdf/1401.5761v1.pdf

Shane C.
Shane C.

Here I thought I could use the present theory of black holes, firewall and event horizons to back up a few verses of Biblical scriptures. thrown into outer darkness, the elements would melt away and all memory of these would be no more. Oh well we will have to wait and see.

Jeannette Smart
Jeannette Smart

I know I'm not a learned person, but my question for someone willing to enlighten me is; Are there any Black Holes within possible reach to send a drone or whatever to see if it does "fry" or can enter the "Hole". It  all seems guess work to me without doing a physical test, one can hypothesise all they want, but it's still guess work in the end. Please don't be offended by my simplification of Quantum Physics..... I'm learning only what my brain is capable of, so if you have an answer please keep it simple...., Thankyou

Achlen Daniel-Browne
Achlen Daniel-Browne

I haven't seen anything to clarify what white holes are yet; & the focus of black holes seem to usually be the sucking in of matter, etc. & less about the matter, etc. they blast out.  Could the white hole be what is blasted out?  The black hole doesn't keep what it sucks in forever & the white hole shouldn't be able to blast out from nothing, so do white holes & black holes occur together?

Ibok Jacob
Ibok Jacob

i agree with what professor Don Page says, that there is no way to verify if this new idea is correct.that's kind of the problem with these theories, there isn't a solid way to verify them..YET

Devin Harri
Devin Harri

black hole leads to the Under verse "

Ronston Hillaire
Ronston Hillaire

If there was a means of waste management in the universe.; to collect waste matter and energy and recycling them before redistribution to seed new star nurseries. Would it not be said that Black Holes fit the bill? Maybe black holes have a more simple purpose than being massive teleportation devices for humans! Maybe?

Raul de Vera Jr.
Raul de Vera Jr.

The beauty of science. You can propose new ideas without offending anyone, or their beliefs. I wonder how will future generations will react to this?

Todd Saunders
Todd Saunders

The article says you cannot predict weather more than a few days in advance. Well, I disagree, in three months, in North America, it will be warmer than today.

Vaibhav Potdar
Vaibhav Potdar

Guys go n study sm noatic science.. time trvl is possible n blackhole is just other side of wormhole.. but dont try to chnge the past after travelling back in time.. otherwise u'll b doomed.. trust me..

Ahmet Çolak
Ahmet Çolak

now, you can no longer think of differents.

Kirk Dalgrin
Kirk Dalgrin

air = time, e=mc2, theory and formulas are okay! however when

Science and religion are one in the brain happiness and healthiness prevail.

Noel Francis
Noel Francis

@robert cobb The wood stove concept is apropoe but the ashes would stay in the stove... never leaving, sending out the wavelengths of the matter consumed. What is at issue here is the time constraints we associate with the releases of this type of information.

Einstein said "... if you could see a black hole, your too close to it." maybe you should've been going in the opposite direction a long time ago, you get my drift? ... now that's an event horizon.

Josh B
Josh B

Maybe it is possible that he was completely wrong. Hawking is also the one who came up with the idea of the Big Bang and maybe it was really God. According to Wikipedia when he was at Oxford he " found the academic work 'ridiculously easy.'" and he was "interested in classical music and science fiction." Do you think it is possible somehow he was studying some science fiction with science?

I think there is so much that we just don't know and are just starting to learn. God has a part in much of this, but we also just have to have faith in God and it is best to study His word.

Richmond Platz
Richmond Platz

@Luis Garcia-Bunuel  The singularity could be an endpoint/beginning point of one dimension to another.  It must be a Multi-Verse after all!  I believe it all breaths in an expansion/contraction pattern.  There could be a kind of spillover back into our know dimensional existance, but only a very small amount!  Suskind and friends say appx 25%.  Something to consider.  Perhaps we'll never know, at least not in this physical form we now wear!

thehappydrummer

Eugene OR USA

Spencer Kirkman
Spencer Kirkman

@Luis Garcia-Bunuel  Well black holes have the ability to explode, we're not  sure how but it can happen, now it is possible that the big crunch could take place sucking all the matter in the universe into a single black hole and that could explode making the universe even bigger. But your hypothesis sounds interesting but what's you backing?

Josh B
Josh B

Yeah, God does exist and he did create the universe just like the Bible says, no big bang

Travis Stevens
Travis Stevens

@Jeannette Smart that's why its only theoretical physics.. scientists can only use the basic models and functional tools of quantum physics to theorize what is actually going on... in reality if we humans did try to send a probe to a far off or even a near by black hole it would take so many generations of human life for us to reach it we may not be here it find out what happens... our great grand children's great grand children's great grand children wouldn't be likely to see it in there life times... unless we could develop a form of space travel that folds or moves space-time (the basic fabric of space and time) rather than traveling through space like a car travels down the road... its highly unlikely that movement through our universe will become fast enough in our life times to get to a black hole, see what happens when we do, and then actually figure out what we just saw... therefore physicists theorize based on basic laws and principles of physics what might be going on near black holes... in essence its all a big short cut the whole space travel issue entirely... not say it wouldn't be worth a try to see what would happen just unlikely...:)  

Jorge Almaguer
Jorge Almaguer

@Jeannette Smart No we will never be able to reach a black hole. All this is guess work. I say there could be a Disney World inside a black hole and no one would be able to prove me wrong. 

Joi King
Joi King

@Jeannette SmartI SO agree. It seems to me that the effort should be put into sending some sort of spacecraft into a black hole. Then we can confirm something instead of continuing to theorize.

Tom Og
Tom Og

@Jeannette Smart 


Hi Jeannette, 

you are "smart enough" to ask a question. The idea you have is sound. 


However, making it happen is going to take a real leap in our capabilities. 


At the present, Voyager 1 is traveling at (approx.) 3.6 AUs per year. 


One AU = the distance between Earth and Sun. 


At this speed, it will take Voyager 1, about 74,000 years to reach the nearest star, Proxima Centauri, which is approx. 268,000 AUs distant.


More to your question, the center of our galaxy, is approx. 27,000 LIGHT YEARS in distance. 


One light year is the distance that light can travel in one Earth year, at the speed of 186,00 miles per second. 


That equals 671,000,000 miles per hour. (671 million mile per hour.)


and 16,104,000,000 miles per day (16.1 billion miles per day);


Divide that number by 92,955,807 miles (one AU), and your result is:


173.24 AUs per day.


Now go back up to the top of this answer and you will see that Voyager 1 is traveling at 3.6 AUs per YEAR!


So..... you can see that the speed at which our space vehicle travels is very, very, very small, compared to the distances which are present between objects beyond our immediate solar system.




Bob Joe
Bob Joe

@Jeannette Smart Hello Jeannette, You're correct. The best method to find what would happen is to send something and see what happens. Though it is to far. At every center of a galaxy is a black hole. Our black hole in the Milky Way (our galaxy) is about 55.3 million light years away. Reaching it is very unlikely as it would take us forever. The farthest thing that we ever sent out were the two Voyager Probes back in 1977 and they just reached the outside of our solar system which is nothing compared to the galaxy as a whole.

Hope i helped. :)

Chris Charlton
Chris Charlton

@Todd Saunders that would be climate not weather.  Weather is rain, clouds, wind, sun.  Yes you can say the seasons will change but you still cannot predict weather patterns.

Robert Sokolov
Robert Sokolov

@Kirk Dalgrin Well, we cannot really know is it a ball or a hole. Light can't reach our eyes because it is already sucked by the black hole. It is black because even if it had a color, the light would be sucked again and we can't see it. :)

Luis Garcia-Bunuel
Luis Garcia-Bunuel

@Spencer Kirkman @Luis Garcia-Bunuel 

I have no backing. Just believe that our vision of the Universe is limited, and I think that "our Universe" is a portion of a "Multiverse" beyond our grasp. If one can conceive unknown dimensions, perhaps those unknown universes are created from black holes i our Universee. I don't have the mathematical ability to put it into a formula somewhat similaar to those in the string theory.

Mihai Micoara
Mihai Micoara

@Bob Joe @Jeannette Smart  The closest black hole to Earth is V4641 Sgr, located in the Sagittarius arm of the Milky Way, 1600 light years away. There might be an even undiscovered closest black hole but definitely not within our reach, to be able to travel through the Universe and at least through our own Galaxy we need a more advanced technology, we need to be able to leap in hours thousands of light years.

Brendan Reilly
Brendan Reilly

@Chris Charlton @Todd Saunders Technically yes you can.. we just don't have enough information or computers fast enough to simulate / predict earth's weather patterns -- but there is no theoretical boundary.

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