National Geographic Daily News

Charles Q. Choi

for National Geographic

Published January 30, 2014

Black holes are shrouded in mystery, with recent research only deepening scientists' understanding of how strange they must be.

The challenge of nailing down the nature of black holes has returned to the news, with renowned physicist Stephen Hawking saying recently that "there are no black holes"—at least not how we've thought of them.

General Relativity

The conventional view of black holes is that they possess a gravitational pull so powerful that nothing is able to escape, not even light. The boundary past which there is supposedly no return is known as the event horizon.

Now Hawking says there are no event horizons after all. That means that stuff—including light—can indeed escape from black holes. More on that in a minute.

First, let's explain the conventional view of how black holes work. One way to illustrate this is to pretend that a person—say an astronaut—is falling in.

Einstein's theory of general relativity holds that the astronaut would feel nothing in particular while crossing the event horizon. But the extreme gravity inside the black hole would stretch the astronaut's body thinner and thinner, a process whimsically known as "spaghettification." Here's how it would look:

Jason Treat, NG Staff
Source: Avery Broderick, Perimeter Institute for Theoretical Physics, University of Waterloo, Canada

Eventually it would be crushed at the singularity, a point of infinite density at the black hole's center.

Quantum Mechanics

This original picture of black holes holds that they essentially destroy all information about anything that ventures past their event horizons—astronauts included. But quantum physics, the best description so far of how the universe behaves on a subatomic level, includes a principle known as unitarity, which maintains that information cannot be destroyed.

To resolve this conflict, some scientists have recently (and controversially) suggested that black holes have "firewalls" at their event horizons. These are zones of extraordinarily destructive radiation. In this scenario, our astronaut would be instantly incinerated when crossing the event horizon, as would anything else falling into a black hole. The radiation released by the firewall would preserve information about the destroyed objects, astronauts included.

Here's how that would look:

Hawking's Idea

The problem with firewalls is that while they obey quantum physics, they contradict Einstein's well-tested equivalence principle.

This principle basically says that people do not experience their weight while in free fall, so falling through a black hole's event horizon should be an unremarkable event—which is why an astronaut would not even be aware of the transit.

This is where Stephen Hawking comes in. His idea resolves the problem of black holes defying the equivalence principle by doing away with their event horizons.

Instead of an event horizon, he says, black holes have "apparent horizons" that only temporarily entrap matter and energy, which are eventually released as radiation that retains all the original information about what fell into the black hole, albeit in highly scrambled form.

It would look like this:

Not the Last Word

However, many researchers have expressed skepticism that Hawking's idea solves the riddles of black holes.

"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 of the California Institute of Technology, who did not participate in Hawking's study. "These problems are very far from being resolved."

Theoretical physicist Leonard Susskind of 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 Juan Maldacena of the Institute for Advanced Study hint that a phenomenon known as quantum entanglement might link two black holes via a wormhole (a shortcut connecting points distant in space and time). This line of thought might serve as the foundation for research that could settle the firewall controversy, Susskind said.

The bottom line: The mysteries surrounding black holes are far from resolved.

Look for The Truth About Black Holes on the cover of the March issue of National Geographic magazine, on newsstands February 25.

26 comments
Piitaa Bread
Piitaa Bread

would they allow someone to take their space shuttle into the blackhole? has anyone evertried?

Carlos Martin
Carlos Martin

The universe is full of mysteries. Men's theories are only guesses, and no one can be sure 100% that his theory is fool-proof.

Michael Martinez
Michael Martinez

is there no way to make a space shuttle for example like the rover ? With the adequate equipment that can be sent to the so called black hole and track its path,visuals,sounds,smells,texture etc?

Daniel Jeantou
Daniel Jeantou

Interesting yet complicated. I wonder if someday, we'll really understand black holes. CERN astrophysicists recently came up with some new theories which are still being tested.

Elvira Howell
Elvira Howell

I don't agree, I can't believe that we are even close to understanding the Universe.

Astrophysicist or layman. The universe seems to be an immense expanse of mysteries, wonders and most of all surprises.

To be alive in a hundred Years from now. ( providing we don't blow yourself out of existence by then ) What wonder we could be experiencing. If rebirth is a possibility, I hope I come back to see and experience all.

Robert Brinar
Robert Brinar

Very interesting about black holes, especially how ideas and theories are changing as we go forward. The astrophysicist are truly on the cutting edge of our understanding of the universe.

Felix Kwan
Felix Kwan

Like to learn more the discovery from space.

Douglas M.
Douglas M.

What I'v always wondered and like if you agree All matter in the universe( universes) leave an imprint correct? Wrong the only known thing that doesn't leave an imprint is a black hole it literally tears the fabric of space and time so in my mind it basically open a hole in the universe isn't it possible for it to open a Theoretical hole to another dimension or realm of some sorts but the gravity is to strong for any thing to actually survive the travel.

Suzanne Thomadella
Suzanne Thomadella

Edward Fredkin, famed scientist and educator, once postulated that the universe is a computer; not that it BEHAVES like a computer...it IS a computer and it's programmed to give someone an answer. If you care to read the entire article, it's in the April 1988 issue of The Atlantic (fka, The Atlantic Monthly). The idea about black holes devouring information is very much in line with Fredkin's ideas almost 30 years ago. To Fredkin, information is more fundamental than matter. Who knows, perhaps we are all existing inside a computer and a black hole is where the universe erases "the disk"!! 


The universe isn't stranger than we imagine, it's stranger than we CAN imagine. 

Chen Siyuan
Chen Siyuan

Maybe energy entering the black hole is condensed into matter instead.

Thanh Nguyen
Thanh Nguyen

It's not the matter for arguing but for our knowledge and discovery.

Dorairajan Rangadorai
Dorairajan Rangadorai

Quite amazing Black Hole Theory is being riddled in three different latest  theories.



David Millican
David Millican

all matter in the universe is moving.... our solar system revolves around its centre causing gravity ... we in turn revolve around the sun causing gravity.... our moon in turn around us causing yet more gravity..... to think of black holes as anything but a gravational phenomonum would be strange ..... and since that black hole was a former star it should be moving around the centre point of its galaxy ..... and also moving through space away from the starting point of the big bang.... other than that we know nothing

Robert Weeks
Robert Weeks

I believe there are black holes,however I also believe they are stationary as far as movement. Kinda like bath tub drain. Everything works off of gravity. Even our weather systems on earth are caused by gravity, by the spin of our earth. So when it comes to black holes yeah they exist, but do the move I think not.

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?

Beatrice Olsson
Beatrice Olsson

I do not understand why, after Einstein, poeple still aproach black holes the Newton way.

Max Taffey
Max Taffey

@Robert Weeks  so what are your beliefs based on?  Years of extensive research in astrophysics, or just a gut feeling?

Nadir Bengana
Nadir Bengana

@Robert Weeks  oh u shut up thinking u know more than hawking and einstein just go back to facebook or whatever 

kaya lou
kaya lou

@Nadir Bengana @Robert Weeks  believe it or not black hole don't move, earth is lucky enough not to have a black hole near by is system solar, because if there was one coming forwards earth oooh it would eat earth within second and earth wouldn't be here! so luckily black hole don't travels with speed or what so ever don't worry man they ain't coming to get you,lol But believe in what you believe is good man peace...

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