Yes, Virginia, There Are Black Holes

In Black Holes by Brian Koberlein64 Comments

Recent headlines have proclaimed “Black Holes Don’t Exist!” They’re wrong. Black holes absolutely exist. We know this observationally. We know by the orbits of stars in the center of our galaxy that there is a supermassive black hole in its center. We know of binary black hole systems. We’ve found the infrared signatures of more than a million black holes. We know of stellar mass black holes, and intermediate mass black holes. We can even see a gas cloud ripped apart by the intense gravity of a black hole. And we can take images of black holes, such as the one above. Yes, Virginia, there are black holes.

So what’s with the headlines? It seems to start with a link-bait article about a new work concerning the formation of stellar mass black holes. The paper hasn’t been peer reviewed, but it is an extension of an earlier work by the same authors that has been peer reviewed. The focus of both of these papers is on the firewall paradox, specifically how Hawking radiation might affect the gravitational collapse of a star to form a black hole.

The firewall paradox is something that arises when you try to combine black holes with quantum theory. In quantum theory there are limits to what can be known about an object. For example, you cannot know an object’s exact energy. Because of this uncertainty, the energy of a system can fluctuate spontaneously, so long as its average remains constant. In 1974 Stephen Hawking demonstrated is that near the event horizon of a black hole pairs of particles can appear, where one particle becomes trapped within the event horizon (reducing the black holes mass slightly) while the other can escape as radiation (carrying away a bit of the black hole’s energy). These escaping particles have come to be known as Hawking radiation.

According to general relativity, if you were to fall into a black hole, you shouldn’t notice anything strange when you cross the event horizon.  Yes, you might feel strong tidal forces, but you’d feel those outside the black hole as well. But according to quantum theory if all this Hawking radiation is being created near the event horizon, then you should experience a firewall of quantum particles. The solution to this theoretical problem is still a matter of some debate. Some, such as Hawking and the authors of this new paper, feel that the Hawking firewall prevents black hole horizons from forming. Others, such as Sabine Hossenfelder argue that quantum theory doesn’t lead to a Hawking firewall. Just to be clear, I’m personally in the Hossenfelder camp.

In this new paper, the authors show that if the Hawking firewall idea is correct, then as a star starts collapsing at the end of its life, before it collapses into a black hole Hawking radiation starts kicking in, which pushes back against the collapsing star. So instead of collapsing into a solar-mass black hole, the star almost collapses into a black hole, Hawking radiation stops its collapse, and the stellar core then explodes. So the star dies in a supernova explosion, but no black hole is formed from its core.

This is interesting theoretical work, and it raises questions about the formation of stellar-mass black holes. But it doesn’t prove that stellar-mass black holes don’t exist, nor does it say anything about intermediate mass or supermassive black holes, which would form by processes other than stellar collapse. And of course the work depends upon Hawking’s take on firewalls to be correct, which hasn’t been proven. To say that this work proves black holes don’t exist is disingenuous at best.

So don’t buy into the hype. Black holes are real, this work is interesting, and the link-baiters should be ashamed of themselves.

Paper: Laura Mersini-Houghton & Harald P. Pfeiffer. Back-reaction of the Hawking radiation flux on a gravitationally collapsing star II: Fireworks instead of firewalls. arXiv:1409.1837 [hep-th]

Comments

  1. The question that keeps popping in my head is, ok, so what is Mersini-Houghton’s explanation for those things that we have observed that we have called black holes? As you note, they still have all the properties that we attribute to blackholes. Is it fair to say that she is disproving a Hawking conception of a very narrow aspect of blackholery? Kind of like disproving the existence of black swans but not the existence of swans themselves?

    1. Author

      It seems to me that what she’s developing is a possible test for the Hawking firewall. If, for example, we observed sub-solar mass black holes, or saw some signature within supernovae explosions, that might be indication of a backreaction effect.

  2. I am a layman (to say the least) but I find this stuff very interesting. Thanks for the article and thanks for writing it in such a way that an amateur can follow it.

  3. Oh thank you so much for writing this article. I’ve been seeing the “Black holes don’t exist” headline all day today and now I can just link them here.

  4. “In 1974 Stephen Hawking demonstrated is that near the event horizon of a black hole pairs of particles can appear, where one particle becomes trapped within the event horizon (reducing the black holes mass slightly) while the other can escape as radiation (carrying away a bit of the black hole’s energy). These escaping particles have come to be known as Hawking radiation.”

    That’s how I’ve always understood it.

    However, this then seems to say that for any effects from the Hawking Firewall, you first need to have an event horizon (otherwise, no way to trap the one particle) … by which time you already have a black hole.

    What am I missing here?

    1. Author

      Hawking has argued that you can get the radiation effect from an apparent horizon rather than an event horizon. That’s what this new work is based upon.

      1. still sounds kind of plausible to me… it doesn’t have to actually prevent a black hole from forming or gaining mass… i am thinking in something like a field forming with time, while the black hole gains mass… then there’s alwas to be considered that things do not necessrily form evenly distributed, taking into account the storm of forces and matter that the gravity and movement of things outside are causing, matter would still be able to fall into it through some kind of gaps in that firewall, adding to the mass of the black hole.

        thinking of the massive forces pulling matter in, it still sounds ok if that firewall may be there, just probably not so uniformly distributed and probably not generating enough force through the radiation to counter the incoming mass, compared to the gravitational force of the black hole pulling that mass in…

        dunno… just poking around with thoughts…

    1. It’s an actual image at different wave-lengths than what your eye sees, translated into wavelengths that your eye can see. In other words, it is nothing more than blue-shifted, to make it more comprehensible for human eyes. But there is nothing false about the image.

  5. Seems to me if the firewall hypothesis predicts stellar mass black holes cannot exist and then you look around and see stellar mass black holes, then you have just disproven your hypothesis. That’s science. Are there or are there not stellar mass black holes? If so…reject firewall hypothesis.

  6. There are energy eigenstates in quantum mechanics—this fact is historically significant, since the formalism of quantum mechanics was originally developed by people investigating the discrete energy spectra of atoms. Moreover, the states that are not eigenstates don’t spontaneously fluctuate through different values of energy, about some average. The phrase “quantum fluctuation” refers to fluctuations you’d see in measurement results if you were to perform a measurement (for instance, of energy) many times in identically prepared copies of a system—not to something dynamically going on in an individual system. In non-eigenstates, the system simply does not have a particular energy: it just has different odds of turning out to have a certain energy if you were to measure it.

  7. The world has truly turned upside-down when the “Hype” is to believe that these truly mind-bending objects DON’T exist 🙂 I’m glad that I read your explanation; the world seemed less wondrous for a second, there.

  8. Not sure where you got the idea that we have ever observed a Black Hole. According to NASA’s own website humans cannot observe a black hole with any known technology. We can only infer on how a black hole would work based on observing visible matter interacting with what we assume are “black holes”. Even the picture at the top of your article is not a picture of a black hole. It is an X Ray image of what scientists assume is radiation being emitted from a “black hole”. I am no expert on this at all, just wanted to point out the flaws in your article. It might be a good topic to get the popular Youtubers over at Nottingham University to discuss.

    1. An X-Ray image is a picture. It doesn’t have to be on the visible region of the spectrum to qualify as a “picture”, you know.

      Yes, it’s not a picture of a black hole per se, but a picture of its supposed effect in its surroundings.

    2. What you say is is relatively wrong as well, because how you observe other things in this universe lets say an apple is also about how they effect what is around them. So meaning apple should reflect light for you to understand it is there if you cannot touch it. Likewise bats use sound waves to observe and we use visible spectrum of light for our daily life to observe and if you cannot use any of those things for some reason lets say a black hole eats them all you can use how matter acts around it so is a similar concept in my opinion.

      1. Your reply is nothing more than sophistry. Black holes are theoretical, mathematical objects. They were NOT deduced from empirical observations. In line with this fact, they are also NOT inferred from empirical observations. They are assumed to exist because their existence props of theoretical notions about how certain things work in the cosmos. But when gas clouds move past supposed black holes and nothing predicted happens…well, the scientists are left baffled. They are always baffled, most of the time. Black holes do not exist, and they don’t need to exist in order to explain the phenomena that we see.

        1. I wasn’t underlining definition of a black hole and mathematical understanding of a black hole or any of those points are correctly defined/understood or not. I just stated there is something out there and we try to observe it looking at how matter acts around it.

        2. Absence of evidence is NOT evidence of absence. As for your claim that the are not inferred from empirical observations………you’re VERY wrong(as of the year 2013). A black hole cannot be directly observed, but what can be observed is the black hole *shadow* created by the event horizon….The presence of an event horizon can be observed where the measured redshift is infinite. That is, where the electromagnetic frequency drops to zero. Much to your dismay, such a thing has already been observed at Sagittarius A* in the center of the milky way using Very Long Baseline Interferometry courtesy of the Event Horizon Telescope. A project is already underway to construct a comprehensive image of its black hole shadow which should be completed by the year 2020.

  9. I just watched a video presentation by Professor Mersini-Houghton. I didn’t hear her say that there were no black holes. In fact, at the beginning, she described how we observe the gravitational pull of black holes.

    What she said was that collapsing stars do not produce singularities.

    1. Right, exactly. I saw the video as well, she discusses the secondary observational evidence for black holes (there is no primary observational evidence for black holes, because, well, they’re black holes) in brief detail. She isn’t disputing that stars beyond about ten solar masses collapse into a very small object, she is disputing that they collapse into a singularity.

      1. No, she is saying that it is impossible for a black hole to form in our universe, quite clearly. Now, we can play semantics and bate and switch, and we can keep the term black hole. But that isn’t helpful. There are considerable differences between a black hole and a supermassive celestial object, between collapsing stars and singularities, between what mathematics says they can do, and what we observe.

  10. That’s almost exactly what I said on phys.org’s facebook post regarding this ridiculousness, and I’m not even a physicist. *Pats self on back*

  11. Why do you call black holes observable phenomena? They’ve literally never been observed. I agree that they exist, because a lot of other phenomena are existentially dependent on black holes – but perhaps you shouldn’t stretch the truth to fit your argument, lest you taint the credibility of the rest of your article.

  12. The evidence you point to Brian, none of it is necessarily indicative of the illustrious metaphysical object we’ve all come to know as the “black hole”. The G2 gas cloud got ridiculously close to the galactic center…and it’s still intact. You sound like an apologist trying to discourage people from leaving your religion. I think it would be better to address the mathematical proof itself, as it is demonstrated in Virginia’s article, than to sound like the narrator of a PBS special.

    1. The G2 gas cloud is not an actual cloud, it is a binary star system in an apparently stable orbit around Sagittarius A*. That is the best explanation for why it was not devoured by the supermassive black hole Sagittarius A*, which already HAS been observed devouring stars that wander too close.

    2. And furthermore, Bob, there are already some serious flaws in the mathematical “proof” that black holes cannot form. Now regarding the gas cloud G2, you failed to read up on the followup details of the story. The gas cloud actually contains a very dim star whose momentum prevented it from being completely swallowed up by Sagittarius A*. Sagittarius A* is a Kerr black hole whose singularity is a ring of infinitesimal thickness and infinite density but finite circumference. When matter approaching it does so at an azimuthal angle < 90 degrees(above the plane perpendicular to its axis of rotation), the black hole does not completely swallow the infalling matter but "wobbles" until the matter is aligned at an angle of 0 degrees with the singularity ring.

      Llikewise, there have been observations from other galaxies of stars falling into the galactic center, followed by a flare-up of X-ray emissions, and then disappearing into it(and failing to emerge from the object at the galactic center). See this article:

      http://www.space.com/12719-black-hole-swallows-star-nasa-swift.html

  13. Why is your title “Yes, Virginia” instead of “Yes, Laura and Harald ” – the authors of the Black Holes don’t exist paper?

  14. Would it be helpful if they combine multi-universe theory with black hole theory? If the center of a black hole and the universe before the Big Bang are both called “singularity” with the same attributes, could it be the portal that connects two universes (our universe and another that is not necessarily in a parallel space but more likely, in a different time dimension)?

    1. shhh….you’ll ruin my escape plan for the eventual heat death of the Universe! I plan to escape into a new universe via a super massive black hole collision, and set myself up as it’s God!

  15. I don’t believe in singularities I do imagine there are super dense objects at the centre of galaxies that have so much gravity they stop stars flying off into the cosmos.
    I also think these objects spin so fast that they absorb light photons rather than gravity stopping light (which I believe has no mass so how can it be affected by gravity ?) Which is why they cannot be visible.

    1. I’m no expert but I’ve come to know that we can see behind large objects in space thanks to the bending effect their gravity produces in light that passes by. If that is true, then gravity does affect light, maybe on a really low scale, but does…

      1. I’ve read that as well but if that’s true and the object’s are truly massive just to slightly bend light how much more would it take to stop light ?

        Maybe it’s more to do with some kind of gas cloud or heat refraction than gravity but I’m no expert either but I have my own idea’s.

        1. I’m sure there is a formula out there for that lol. The light isn’t really “stopped” ever, even on an event horizon or by gravitational lensing, it just keeps getting “bent” until it’s looping around itself and “disappears” from detection. Whatever objects are causing the gravitational lensing your talking about are also certainly “stopping light” as well, it’s just that it’s only stopping a very small fraction of the over-all image. The closer the light is to the gravitational object the more it’s bent, but that effect drops off rapidly per the inverse square law (inversely proportional to the square of the distance from the source).

          Photons DO have mass, but it’s a “special” mass called “relativistic mass” since they always move at the speed of light they barely “take part” in our Universe but are still effected by gravity as if they had mass. The actual science on photonic “rest mass” (which is the normal mass) being something other than zero is still being tested. It’s PROBABLY zero, but might not be…our experiments so far are not powerful enough to find a measurement!

          1. Photons can’t have mass or they would have infinite gravity if Einstein is correct and why don’t they exert any force if true ?.

            I Still think black holes are solid objects that spin faster than light and the event horizon is where matter that is being whipped in starts to go faster than light and so becomes dark and starts absorbing photons because it can’t emit any due to it’s velocity.

    2. Light is affected by gravity in the same way everything else is–the space through which it travels is curved. All matter creates a four-dimensional gravity well–like a bowling ball in the middle of a (frictionless) trampoline, or the deep funnel around shopping mall wishing wells–if you roll a marble (or a coin) around the mass, its path will curve around the well The coin will spiral, planets will orbit, photons will curve. Mass bends spacetime itself.

      Having mass isn’t a requirement to be affected by gravity. All that’s required is to be movable–just as it’s impossible for a marble to move arrow-straight across a curved surface, it’s impossible for light to travel straight around a deep gravity well. Photons approach a star or black hole, and their path curves around, and if that well is deep enough (if the body massive enough), it spirals inward. Space itself is so warped by the mass of the celestial body that light is drawn inward–No mass is required of the photons.

      The photon is not “pulled”, space itself is warped.

  16. I think she needs to reword this to say Black Holes were not formed the way we previously thought.. and if that’s true, the Big Bang theory may be incorrect as well.

  17. I don’t think she’s disputing the existence of huge masses at the centre of galaxies; only challenging what we think we know about the nature, or state, of the mass.

  18. As “seen” from the outside a collapsing star in an ideal setting with no material in the neighborhood to complicate things would seem to take forever to disappear into its event horizon. This is due to the extreme time dilation very near to the horizon. Someone riding on the surface of the star would find the journey to be over very quickly, on the other hand, and not notice anything at the instant he passed the horizon. Hawking radiation complicates things and perhaps introduces a paradox. An isolated collapsed star would lose energy and probably disappear in an extremely extremely …extremely long time, inconsistent with the idea that to an outside observer it takes forever for the star to cross the horizon. This is where the putative firewall and all that come in, and controversy lives.

    But in ANY case, Laura Mersini-Houghton’s calculations, true or not, have to do with a time so far in the future that they are irrelevant for the astrophysics of “black holes” as they are observed in the universe today. Whether these objects have already collapsed to singularities (they have not, according to general relativity) or are “frozen” at their event horizons makes absolutely no difference to astrophysics. If you want to see what happens “inside” you must take the ride. Mersini-Houghton’s theory will never give rise to effects observable to an outside observer.

    (Personally, I think she has made mistakes beyond her apparent claim that her theory is somehow observationally important.)

  19. Thanks for writing this rebuttal. The original article I read pertaining to her theory felt in the vein of typical media sensationalism.
    She certainly poses some interesting questions albeit nothing that eliminates the empirical evidence that black holes exist. I greatly abhor sensationalist headlines in this regard, as many people simply hear the tag lines and start repeating them as fact.
    Keep up the good work!

  20. Brian, not to muddle the waters a bit, but is the amount of Hawking virtual half particle radiation about as much as the solar wind that keeps comets away?

  21. Black holes do indeed exist. However Mr Oberlein, I honestly think your blog post really doesn’t go into enough detail about HOW we know that they exist. In order to know that something like a black hole exists, there needs to be direct observational evidence. And the only feature of a black hole that can actually be observed is its event horizon(or “black hole shadow”). What indicates the presence of an event horizon is infinite redshifting. That is, the frequency of electromagnetic waves drops to 0 Hz once the radial distance from the object is less than a certain amount.As it turns out, there is an international network of telescopes that are collaborating as part of something called the Event Horizon Telescope project whose mission is to provide actual photographic images of black hole shadows. The nearest object to Earth for which observational evidence of being a black hole is present is Sagittarius A* in the center of our Galaxy. Proposals have been made that it is not an actual black hole, but an extremely massive object with a very, VERY hard surface. But given the observations of hot plasma flowing in, if it has a surface then because the plasma is accelerating towards the object at relativistic speeds it should impart enormous amounts of heat to the surface due to force of the collision which should give it exuberant luminosity. But recent observations show that the luminosity of Sagittarius A* is far below even the crudest calculations of what its luminosity *should* be if it is a superdense, compact object! The only explanation to explain this low luminosity at the center is the presence of an event horizon which means that it must be a black hole.

    1. Logically speaking, your argument is flawed. It is impossible to directly observe a black hole from here. If light cannot escape a black hole, then there is no way to see it. We can observe what we believe to be a black holes affect on the local area, but that does not mean that a black hole did it. So if the math says a black hole cannot exist, it is quite possible black holes do not exist, and science needs to find the actual cause of what is being seen. (Which is difficult if you can’t see it, since that would require light reflecting off of it.

      1. Author

        We don’t have to observe a black hole directly to know that it’s there. Jets, stellar motion and other effects are perfectly valid methods of verifying black holes.

      2. What “math” are you talking about? It turns out that mathematics, including computer simulations based on mathematical derivations, have shown that Kerr black holes can form from means OTHER than stellar collapse or even pre-existing black holes. Specifically, the math has shown that they can form by 2 colliding neutron stars that form an unstable binary which collapses into a rotating black hole with a Kerr metric. What I also stated is that the actual black hole is not what can be observed, but the presence of an event horizon, the external feature of a black hole, can be DETECTED by means of redshift measurements using VLBI interferometry. And moreover, the math states that the event horizon will create an observable “black hole shadow” when the black hole is actively feeding.

        Direct observational evidence =/= direct observation of the actual black hole.

        1. There has never be a direct observation of a black hole or event horizon. The phenomena stated as indirect observational “proof” does not prove it to be a black hole. When the Event Horizon Telescope project provide’s actual photographic images of black hole shadows then I’ll believe it. Right now, it’s science’s best guess we have, but not fact.

          1. What you choose to believe(or not to believe) is irrelevant. The evidence strongly favors the existence of supermassive black holes at the heart of M87 and Swift J1644+57…And Sagittarius A* here in our galaxy. Images aren’t actually scientific “proof”. It comes from redshift measurements collected via VLBI that can demonstrate the presence of an event horizon of a massive compact object that is sucking in matter and has a luminosity far below its Eddington limit.

            Sagittarius A* appears to be quiescent right now whereas the core of M87 is actively feeding and VLBI studies show even horizon structures the size of the solar system. It is SO damn big and getting bigger and in fact, the entire galaxy of M87 appears to be getting swallowed up by it!

  22. “We know by the orbits of stars in the center of our galaxy that there is a supermassive black hole in its center.”

    No we do not. We know the orbits of the stars and how they are reacting, but it does not mean there is a black hole in its center. Effect does not show cause. It is always cause then effect. Effect does not come first. You seem to look at the effect and say, well since this is the effect we see, this must be the cause. There are other things that can cause this to happen (as you have shown one in your article), which goes to show there could be others.

    1. Author

      We know by their motion what the gravitational force on them is. It’s relatively straight forward to look at stellar dynamics to calculate the central mass. In this case effect does show cause.

    2. In the case of the milky way galaxy, the object at the galactic center, Sagittarius A*, shows strong evidence of radiatively inefficient accretion flow. If it is not a black hole, but a supermassive compact object made of matter with a surface, then it is violating conservation of energy. There are examples of other compact, non-luminous objects made of matter which emit intense bursts of radiation due to friction(caused by the Electromagnetic “Coulomb force”)when infalling matter strikes the surface. Like neutron stars for example. The observational evidence now gathered shows no indication that Sagittarius A* has a surface, but instead it shows the telltale signs of an event horizon.

  23. So, we may not know the composition of dark matter, but we surely have calculated its distribution of density. That means we must know the density of dark matter surrounding some prominent black holes. And even though dark matter does not interact except through gravity, that surely must mean that dark matter entering a black hole cannot subsequently escape (unless dark matter is not constrained by relativity). Thus, we should be able to calculate the rate of mass change in some black holes due to the influx of dark matter. At some point, I venture to guess, that rate of change will become a measurable factor. I guess we are still not too clear about the quantity of normal matter entering any particular black hole, but I imagine the quantity of dark matter would be easier to determine because there is no accretion disk for dark matter to expel a fraction that is falling in.

    1. I thought as far as observers on the outside are concerned, matter never finishes crossing the event horizon (they get stuck on the horizon forever)? In that case, could we ever measure the change in mass of a black hole?

      Or is that “teachers lying to us” again, and the mathematical truth more subtle?

      1. Yes, as seen from outside, all the material that forms the black hole is “frozen” at the horizon, because of the infinite time dilation there. So the structure is like a very thin and very dense shell asymptotically approaching the horizon.

        You might wonder if this would appear or behave any different than the usual “black hole” where everything is at the singularity. It doesn’t! The external gravitational field is *exactly* the same in both cases (a consequence of Gauss’s Law for gravity). This means that you can observe the black hole’s mass increase as it accretes more material. The shell gets bigger, more massive, and the gravitational pull on its surroundings grows stronger, and it does so in exactly the same way as if all the matter was instead at the singularity.

        I want to emphasize that it is not possible to actually see this shell of matter frozen on the horizon, because it is redshifted extremely quickly. Within just a few seconds of the collapse to form the black hole, it is completely black. You might consider falling in yourself, to see if the material is really there. You’ll find that you pass through the horizon without encountering anything there at all. This is because in the frame of the material falling in, the time it takes to collapse to singularity is finite. If you wait too long after the collapse to fall in yourself, then you cannot catch up to that material before hitting the singularity yourself.

        So what’s really going on here is that the thin shell description and the classic black hole with singularity description are actually consistent descriptions of the same object. They both make the same predictions for the same observers. It’s just that different observers conclude very different things about where the material that falls into the black hole ends up.

  24. There was an even more ridiculous instance of a person stating black holes don’t exist. I was listening to a TV news cast once, where they were discussing a theory somebody on the internet put out, about the earth being destroyed by a black hole. And at the conclusion of the news story, as if in an attempt to put the internet rumor down for good, somebody said “black holes don’t exist”.

    I wish I remembered exactly when this news cast was, so I could link to it, and maybe have you guys cover that story, but I can’t remember that at this moment. I’ll scour the net and see if I can find it.

    1. If you search the internet, you’ll find plenty of websites containing claims that black holes do not (or cannot) exist. And many of them are, when examined side-by-side, inconsistent.

      I’ve found a few (less than ten?) which back up their claims with what looks like quantitative analyses and/or some mathematics. However, none – that I know of – stand up to close scrutiny.

  25. More importantly, gravitational radiation from 2 black holes has now been CONFIRMED. So there is a brand new piece of evidence for their existence! A lot of black hole deniers argued that gravitational radiation was nonexistent and that LIGO was a waste of money…..And now they gotta eat their words.

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