
Stephen Hawking: 'There are no black holes' - mrfusion
http://www.nature.com/news/stephen-hawking-there-are-no-black-holes-1.14583
======
ck2
So basically they took off three words of what he said to make a super
sensationalistic headline?

How scientific.

 _there are no black holes with event horizons_

If you take the mass of a sun and squeeze it into a few miles wide, you are
definitely going to get inescapable gravity no matter what you want to call
it.

~~~
lmm
By that logic neutron stars should be black holes. But they're not.

~~~
ck2
Sorry I didn't mean the sol sun, I mean a sun with enough mass to become a
black hole.

Neutron stars are in a sense "failed" black holes because of not enough mass.
I wonder if they could eat more mass and achieve that status though.

~~~
venomsnake
That is one of the standard candles - type 2 supernova IIRC - when neutron
star in binary system is eating the other star and turns nova very
predictably.

~~~
splat
The standard candles are Type Ia supernova which are when white dwarfs exceed
the Chandrasekhar mass and become neutron stars. It is thought that when
neutron stars exceed the maximum mass of a neutron star (which is not well
known, by the way) they form a gamma-ray burst.

~~~
kevinastone
The TOV Limit for those following at home. It's when the star's gravitational
pressure exceeds neutron degeneracy pressure and collapses into a black hole.

[http://en.wikipedia.org/wiki/Tolman–Oppenheimer–Volkoff_limi...](http://en.wikipedia.org/wiki/Tolman–Oppenheimer–Volkoff_limit)

------
ssivark
I echo my comment from the other Hawking thread on the HN front page:

The article being referred to seems to be a short piece where he summarizes
his points and puts forward a (new?) idea. Maybe it's obvious to researchers
in the field, but I don't see much argument or reasoning supporting his claim.
It seems like he's just introducing a new idea for people to consider
(brainstorming with the community).

So please don't blow this out of proportion.

~~~
Steuard
This seems like a good way to read it to me. Hawking does put forth some
meaningful arguments in there that deserve attention (or else it wouldn't be
worth listening, even if this is Hawking), but he hasn't proven any new
theorems or shown an explicit counterexample to previously accepted physics.

This firewall issue is just _complicated_ , and it has stubbornly resisted
consensus from the physics community despite a year or so of intense interest.
I think we're in the market for crazy new ideas at this point.

------
PaulHoule
The funny thing about black holes is that the classical story of the black
hole never made sense, but the "old men" of the physics community always
suppressed any real criticism of it since it's been almost impossible to get a
job in physics since 1968.

If you right down the equations for a simple black hole you immediately
encounter a singularity at the event horizon, but this is swept under the rug
by making a coordinate change. The trouble is that coordinate change breaks
the warrantee on the space-time continuum because it will stretch a plank
length out to something macroscopic. making quantum phenomena visible.

A simpler paradox which has never been taken seriously is that an outside
observer sees that it takes forever for something falling into a black hole to
hit the event horizon. However, knowing about Hawking radiation, you know the
black hole doesn't last forever, so an outside observer never sees anything
fall into a black hole.

Thus the classical black hole was always a pipe dream. In the 1970s the
information paradox showed that a classical black hole (which makes
information disappear because you can't tell the difference between a black
hole that was made out of gold bars or feathers) makes information disappear,
but information can't disappear in a quantum mechanical universe.

~~~
Steuard
I'm sorry, but comments like this seriously irritate me. Your words here
reflect some basic misunderstandings of the science involved, but rather than
concluding "I don't understand this", you've instead suggested what amounts to
a conspiracy theory. Quite apart from the deep insult this implies toward
generations of physicists, you're baselessly contributing to the erosion of
public confidence in science.

The quickest way to counter your claims of suppression, I think, is to do a
Google Scholar search for a term like "black hole information paradox". No, we
don't entirely understand what's going on there, but figuring it out has been
one of the most active and fruitful areas of research in relativity and high
energy physics for decades.

As for your "breaks the warranty on the space-time continuum" claim, I'd love
to know why you're choosing the "spherical coordinates" coordinate system as
_the_ fundamental one (so that we should judge coordinate stretches as "too
big" relative to its measure). Not that I like the idea of specifying one
reference frame as "preferred" at all, but if I had to, the only natural
choice would be the reference frame of a freely falling observer. And that's
precisely the coordinate system we typically change to in order to show that
there's no essential singularity at the event horizon. So please don't lob
insults at the active physics community based on your own misunderstanding of
the theories that _they_ spend their lives striving to understand.

[Credentials: I'm a professional physicist: a professor specializing in string
theory with a background in general relativity.]

~~~
scotty79
>> A simpler paradox which has never been taken seriously is that an outside
observer sees that it takes forever for something falling into a black hole to
hit the event horizon

> [Credentials: I'm a professional physicist: a professor specializing in
> string theory with a background in general relativity.]

That's my one of my biggest problems with physics (other is Copenhagen
interpretation of quantum mechanics). As I understand it in our frame of
reference, nothing ever (before present moment) crossed any event horizon
because of gravitational time dilatation.

When I tried to solicit people on the internet to help me understand it they
said that in general relativity theory you can draw line of simultaneity
arbitrarily and that causes "before" and "after" to not make sense for two
distant points.

I can imagine that's true (although I'm doubtful), after all in classical
theory simultaneity is straight line orthogonal to time, in special relativity
it's straight line but slanted dependent on speed of reference frame. I was
imagining simultaneity line in general relativity theory as a well defined
curve dependent on speed of reference frame and mass distribution but I can
also imagine that it's not defined in unambiguous way at all. I am yet to read
some actual scientific material about defining simultaneity in GRT and how it
relates to gravitational time dilatation that seem pretty well defined to me.

If you could recommend some reading material about simultaneity in GRT (or
some more general concept that gets reduced to simultaneity in universe
without mass) I'd be most grateful.

It doesn't have to be too simple. I was International Physics Olympiad
national level laureate and I'm pretty motivated to understand that as it
costed me some sleepless nights over the last ten years or so.

~~~
Steuard
First, an aside: the OP's comment "which has never been taken seriously" about
this topic is also entirely mistaken. Heck, I've heard that issue come up in
serious conversation within the past year.

I've got to concur with the other people you've heard from: simultaneity in
classical (Galilean) physics is the same for every observer, simultaneity in
Special Relativity is different for observers moving with different
velocities, and simultaneity in General Relativity often isn't even globally
well-defined for one observer at a time. That's not too surprising given other
features of GR. You've no doubt heard about "gravitational lensing", where a
large mass curves space so that "straight" light rays from the same distant
object appear to come from two different directions. Now imagine the same
thing happening to a "line of simultaneity", and you'll start to understand
the issue.

I suspect that one concept that might satisfy a part of what you're looking
for as a "generalization of simultaneity" is a _Cauchy surface_ or _Cauchy
hypersurface_ :
[http://en.wikipedia.org/wiki/Cauchy_surface](http://en.wikipedia.org/wiki/Cauchy_surface)
This idea, essentially, is an arbitrary (possibly curved but everywhere
spacelike) plane that divides time into "future" and "past", and that can
serve as an "initial value surface". Have a look at that article for more
information, and see if it's something like what you're looking for.

[Also: I don't like the Copenhagen interpretation, either. I've become more of
a "many worlds"/Everett person ever since a fantastic and highly mathematical
quantum course in grad school, despite the somewhat uncomfortable
philosophical issues with it.]

~~~
scotty79
Thank you very much for your response.

I guess my struggle now is about how to reconcile the fact that simultaneity
in General Relativity often isn't even globally well-defined for one observer
at a time with the pretty well defined gravitational time dilatation. How can
one say that time flows slower in higher absolute gravitational potential then
somewhere else without being able to unambiguously say what's before and
what's after at those two points.

Cauchy surface at least from wiki description doesn't sound much like a
simultaneity line/surface/subspace. Is it dependent on the speed of the
observer? I'm looking for some concept that in universe without mass reduces
to SRT simultaneity. It might be twisted, branching, looping as in you lensing
example but smoothly transitioning towards SRT simultaneity as mass goes to
zero. Also time distance at two remote points between such surfaces should be
reflect value of gravitational time dilatation between those two points. Is
there something like that?

------
codeulike
Black Holes, as originally posited, are quite extreme things to have sitting
around in the universe (infinitely dense singularities etc). Physics seems to
be tying itself in knots to figure out how they would work; alternatively the
idea that they might not be possible in the first place is a much tidier
solution.

This reminds me of a competing theory that states black holes (as currently
understood) can't exist: Instead they are Magnetospheric eternally collapsing
objects
[http://en.wikipedia.org/wiki/Magnetospheric_eternally_collap...](http://en.wikipedia.org/wiki/Magnetospheric_eternally_collapsing_object)

------
vezzy-fnord
Title is misleading. This is simply more research on the very well known black
hole information paradox, proposing that a commonly cited property of black
holes may be wrong.

~~~
codeulike
Not that misleading. Hawking goes on to say there would also be no
singularity. That's quite a big change.

~~~
Pxtl
Yeah. It sounds like his theory is that gravity/spacetime eventually becomes
"turbulent" as the energy level of gravity approaches C (I'm sure I phrased
that wrong). My instinctive analogy is to compare it to how the ideal gas law
or laminar flow equations fall apart in cases where individual particle
interactions screw everything up... to the level that it's impossible for all
the matter to get compressed into a single point.

That's far more interesting to me than the idea that the "event horizon" is
gone.

------
tehwalrus
I never bought that humans could travel through an event horizon[1].

Say that your leg is inside the black hole, but the rest of you isn't. How can
the atoms just outside the horizon detect the quantum forces from the atoms
just inside? Electromagnetic forces are transmitted by photons, which are
forbidden to cross this barrier.

Thus, if you pulled back away from the horizon, you would have an event-
horizon-curvature-shaped hole where your lower leg had just been.

Similarly, for any matter traveling through the black hole, unless two atoms
and all their electrons passed through the horizon simultaneously, no chemical
bond could survive (since from the point of view of one atom, the other
"blinks" out of existence.)

Thus, anything that crosses an event horizon _must_ be fundamental particle
mush, no? Assuming gluons were also forbidden to cross back, even protons and
neutrons would be torn apart.

[1] I mean one around a very massive black hole - so that spaghettification is
yet to occur.

P.S. - This argument takes a very literal interpretation of fundamental
particles; indeed, it would be interesting to test the quantum-ness of matter
to see how this worked - i.e. whether "stuff" really is particles or waves -
since waves could, potentially, exist on both sides of the barrier at once.

~~~
hrjet
IIRC: from the point of view of the human, it takes infinite time to reach the
event horizon, since their speed will approach the speed of light. So the
actual experience of passing through the event horizon never occurs!

~~~
pdonis
_from the point of view of the human, it takes infinite time to reach the
event horizon_

No, it doesn't. The proper time (time by the infalling observer's clock) that
it takes to fall to the horizon is finite.

 _their speed will approach the speed of light_

This isn't correct either. The infaller will see the horizon pass him at the
speed of light, but that's because the _horizon_ is a lightlike surface-- _it_
is moving outward at the speed of light.

------
josu
This is very interesting, because:

>Einstein denied several times that black holes could form. In 1939 he
published a paper that argues that a star collapsing would spin faster and
faster, spinning at the speed of light with infinite energy well before the
point where it is about to collapse into a black hole.

[http://en.wikipedia.org/wiki/Einstein's_unsuccessful_investi...](http://en.wikipedia.org/wiki/Einstein's_unsuccessful_investigations)

~~~
alphaBetaGamma
We have exact solution to spinning black holes (discovered after Einstein's
death) which settles that question.
[http://en.wikipedia.org/wiki/Kerr_metric](http://en.wikipedia.org/wiki/Kerr_metric)

------
Pxtl
Just making sure, the "fire" of the firewall is the Hawking radiation, right?
That is, the event horizon divides matter from antimatter in the energy of
space and spews it outwards. Or are they distinct concepts?

I never understand how Einstein's concept of relativity and his discovery of
an arbitrary maximum speed of the universe can coexist. I mean, how can
everything be relative when there's an absolute maximum velocity? The event
horizon and Hawking radiation/the firewall naturally come out of the speed of
light.

Physics confuses me ever so much.

~~~
wlesieutre
The short version of maximum speeds is that velocities don't add how you'd
expect at relativistic scales. If a ship is moving at 0.5c relative to an
observer and it launches a missile forward at 0.5c relative to itself, the
missile is moving at less than 1.0c relative to the same observer.

In fact, the missile could launch a smaller missile forward at 0.5c, and
_that_ missile would still be moving under the speed of light relative to the
observer. If you just added speed up classically, it'd be going 1.5c.

Really it always works like this, but at speeds we consider normal the error
from simplifying to v1+v2=v3 is incomprehensibly small.

~~~
Pxtl
I assume time-dilation accounts for that, since the ship perceives that it's
launching something at 0.5C but its perception is skewed by time dilation...
but that implies the reverse, since time dilation means that the ship
perceives time traveling _slower_ than the outside universe and thus the
outside universe is _faster_ and so the 0.5C missile should actually be moving
_faster_ than the sum of the accelerations... but relativity says that _both_
sides perceive their counterpart as slower, and then you get the to the twin
paradox.

ow, my head.

~~~
Retric
It's not just time that get's distorted, but also distance.

More importantly, there is no privileged viewpoint. As far as a spaceship is
concerned it's everything else that's moving and it's standing still and the
same physics predictions work just fine it's only the measurements that seem
different.

~~~
Pxtl
Oh, right, I forgot the flattening effect. That makes me feel a bit better.

------
TeMPOraL
Ok, how did this happen?

Yesterday black holes were there. Everybody knew about Schwarzschild radius,
about Cygnus X-1, about black holes theorized to be occupying the centers of
galaxies.

And now everyone here is commenting like it was an obvious fact that black
holes were never real and no one considered them seriously.

What happend? What did I miss?

~~~
jerf
That what label we put on things does not affect what they actually are?
Whatever it is out there in the real universe that are these really massive
things, they aren't waiting for little humans a billion light years away to
decide what they are or are not.

~~~
krapp
The map is not the destination.

------
fargolime
"There are no black holes" was shown 8 years ago, much more simply than
Hawking has posited: [http://finbot.wordpress.com/2008/03/05/no-black-
holes/](http://finbot.wordpress.com/2008/03/05/no-black-holes/)

Black holes are a mistake of general relativity (GR), specifically their
absolute event horizon is incompatible with GR's equivalence principle
postulate, as the blog (which is not mine) shows. In software terms, black
holes are a bug in the theory.

Let's remember that Einstein disbelieved in black holes and for many years
tried to prove they couldn't exist. Also there is no definitive evidence that
they actually exist in nature. By their definition, such evidence can't be
detected.

~~~
gjm11
The argument there looks wrong to me; in particular combining the equivalence
principle with the proposition called (K) there seems wrong. EP in the form
given there says that no test _within the small region in question_ can
distinguish it from a similar small region in a gravitation-free universe, but
"seeing whether the small region can be extended to a larger region" is not a
test you can perform within the small region and it isn't an EP violation if
you can do the extension in the gravityless universe but not in the with-
gravity one.

Other articles on that blog claim to solve other major problems in physics, in
every case giving an answer that disagrees with (what I understand to be) the
consensus of working physicists.

So I could trust the author of the blog, Just Because (which doesn't sound
like a great strategy). Or I could trust my own opinion (which is that on the
one point I looked at it looks as if there's a substantial conceptual
mistake). Or I could trust the current mainstream consensus.

I'm having trouble seeing reasons why I should believe what the author of that
blog says. Do you happen to know of any?

~~~
fargolime
I'm not concerned with trust or consensus, those aren't scientific concepts.
If anyone shows a logical inconsistency with GR, then it's invalid regardless.

> but "seeing whether the small region can be extended to a larger region" is
> not a test you can perform within the small region

That law K doesn't apply in a frame falling through a horizon (a logical test
within that frame, which is defined to be an inertial frame) indicates that
physical tests can also show that the laws of physics differ between that
frame and other inertial frames. The picture in the blog is an example of
that. It's impossible to conduct a test where the cloud described there isn't
splitting in two, unlike in some other inertial frame.

~~~
gjm11
I agree that trust and consensus are not scientific concepts (well, except
maybe in psychology or sociology, but that's not relevant here). But they are
things it's reasonable for those of us who aren't expert theoretical
physicists to take into account, when Some Guy On The Internet says all the
professional physicists are wrong and he's found an internal inconsistency in
general relativity.

The "larger region" you need to look at to determine whether K applies is not
small enough for the defining characteristic of the small region -- i.e., that
spacetime curvature is negligible there -- to hold. The equivalence principle
stops applying once you start considering regions large enough for spacetime
curvature to be non-negligible within them.

~~~
fargolime
Go ahead and take that into account, but hinge your conclusion on whether the
logic's valid, if you wish to stay fully scientific.

Frame X, in which law K is tested, is _defined_ to be small enough that the
spacetime curvature is negligible there. So it's definitely small enough. The
test of law K is conducted wholly within frame X.

------
InclinedPlane
My reading of this is that black holes still very much do exist and have
almost exactly the same properties we thought they did before. The only
difference being some slightly different effects on the quantum scale and on
enormous cosmological time scales (well beyond gigayears).

The editorialized headline here is wholly unwarranted and does a disservice to
the process of scientific advancement, Nature magazine should be ashamed. This
is barely one step up from "Hawking says black holes don't exist, the
explanation will shock you."

------
platz
I couldn't find the article, but there's a theory that states something to the
effect that black holes are only 2D and the rest of the universe is a
holographic projection. They back some of this up by noting that the size of
the event horizion of a black hole grows as a function of 2D mathematical
spaces rather than 3D spaces.

------
differentView
Is there a modern day Feynman that can explain this to us not familiar with
this but still interested?

------
JacobAldridge
Does this mean Kip Thorne has to return a year's worth of Penthouse magazines?

------
omphalos
Sadly I suppose this implies the impossibility of Malament-Hogarth
hypercomputers.

------
acconrad
I think it's important to note that this paper has not yet been peer reviewed,
so this is nothing more than an attention-grabbing title from Nature.

~~~
throwaway_yy2Di
The arXiv paper indicates he has no intention of submitting it to a peer-
reviewed journal -- something that's becoming pretty common in some physics
fields. On the contrary, I see the "yet to pass peer review" remark as a crass
editorialization from the _Nature_ journalists¹. This paper has already seen
more, meaningful, peer review that most papers _Nature_ publishes; informal
review from people downloading the (free, open) paper from the arXiv, or
listening to the talk at the Kavli conference. The institute _Nature_ is
defending is becoming an irrelevant middleman: what's the point of reviewers,
if they barely read the papers, and then hide them behind paywalls from anyone
who actually _wants_ to read them, when there's whole social network of
researchers who will read papers _enthusiastically_ , for free, and share what
they think of them?

[http://arxiv.org/abs/1401.5761](http://arxiv.org/abs/1401.5761)

¹ You should question to what extent they're journalists, when their employer
is a for-profit entity existentially threatened by the subject they're
reporting on.

~~~
weichi
"This paper has already seen more, meaningful, peer review that most papers
Nature publishes ..."

I really don't think that this is true. The useful bit of peer review is
changes made to the original paper as part of the peer review process (both
for accuracy and clarity of exposition). No feedback from arXiv readers has
yet been incorporated into this paper; perhaps in a few months there will be
an updated version that includes such feedback. Until then, people will have
to search the net to get a feeling for how the wider field views his ideas.

In terms of feedback from conferences, plenty of results are presented at
conferences prior to publication in Nature and other journals, so I doubt
there is any difference in the review level here.

------
nikbackm
Sad.

The new terms do not sound as cool as "event horizon", "black hole" and
"singularity".

------
niix
I give up.

------
brokenparser
So, how does one poop?

