Dead and alive at the same time: Black holes have quantum properties

By Tereza Pultarova

quantum black holes.jpeg
Black holes behave like quantum particles a new study has revealed. (Image credit: NightCafe Creator AI)

Black holes have properties characteristic of quantum particles, a new study reveals, suggesting that the puzzling cosmic objects can be at the same time small and big, heavy and light, or dead and alive, just like the legendary Schrödinger's cat.

The new study, based on computer modeling, aimed to find the elusive connection between the mind-boggling time-warping physics of supermassive objects such as black holes and the principles guiding the behavior of the tiniest subatomic particles.

The study team developed a mathematical framework that placed a simulated quantum particle just outside a giant simulated black hole. The simulation revealed that the black hole showed signs of quantum superposition, the ability to exist in multiple states at once — in this case, to be at the same time both massive and not massive at all.

"We wanted to see whether [black holes] could have wildly different masses at the same time, and it turns out they do," study lead author Joshua Foo, a PhD researcher in theoretical physics at the University of Queensland, said in a statement(opens in new tab). "Until now, we haven't deeply investigated whether black holes display some of the weird and wonderful behaviors of quantum physics."

The best known example of quantum superposition is the legendary Schrödinger's cat, a thought experiment designed by early 20th century physicist Erwin Schrödinger to demonstrate some of the key issues with quantum physics. According to quantum theories, subatomic particles exist in multiple states simultaneously until they interact with the external world. This interaction, which could be the simple act of being measured or observed, throws the particle into one of the possible states.

Schrödinger, who won the Nobel Prize in Physics in 1933, intended the experiment to demonstrate the absurdity of quantum theory, as it would suggest that a cat locked in a box can be at the same time dead and alive based on the random behavior of atoms, until an observer breaks the superposition.

However, as it turned out, while a cat in a box could be dead regardless of the observer's actions, a quantum particle may indeed exist in a double state. And the new study indicates that a black hole does as well.

American and Israeli theoretical physicist Jacob Bekenstein* was the first to postulate that black holes may have quantum properties. Since a black hole is defined by its mass, its quantum superposition must mean that this odd gravitational gateway can have multiple masses that fall within certain ratios.

"Our modeling showed that these superposed masses were, in fact, in certain determined bands or ratios — as predicted by Bekenstein," study co-author Magdalena Zych, a physicist at the University of Queensland and a co-supervisor of the research, said in the statement. "We didn't assume any such pattern going in, so the fact we found this evidence was quite surprising."

The new study(opens in new tab) was published online in the journal Physical Review Letters on Friday (Oct. 28).

Follow Tereza Pultarova on Twitter @TerezaPultarova(opens in new tab).


From the new study:

We present a new operational framework for studying “superpositions of spacetimes,” which are of fundamental interest in the development of a theory of quantum gravity. Our approach capitalizes on nonlocal correlations in curved spacetime quantum field theory, allowing us to formulate a metric for spacetime superpositions as well as characterizing the coupling of particle detectors to a quantum field. We apply our approach to analyze the dynamics of a detector (using the Unruh-deWitt model) in a spacetime generated by a Banados-Teitelboim-Zanelli black hole in a superposition of masses. We find that the detector exhibits signatures of quantum-gravitational effects corroborating and extending Bekenstein’s seminal conjecture concerning the quantized mass spectrum of black holes in quantum gravity. Crucially, this result follows directly from our approach, without any additional assumptions about the black hole mass properties.



* The most important discovery of Prof. Bekenstein (born 1947, Mexico, death 2015) is his realization that black holes have a temperature and carry entropy proportional to the area of their event horizon.

This has sparked the creation of an entire field devoted to the study of black hole thermodynamics where the theories of quantum mechanics, general relativity and statistical mechanics are deeply intertwined. This has led to advances in quantum gravity and string theory. He also demonstrated that it is not possible for an observer to measure anything about the black hole except their total mass, angular momentum and electromagnetic charge. This discovery led to the current description of black holes as very simple objects and provides constraints on theories that modify general relativity. These seminal advances have been used by many others and continue to have vast influence in cosmology and theoretical physics.

Professor Bekenstein discovered that a black hole possesses entropy, whose value is proportional to its surface area. Therefore it also has a characteristic temperature. This has led to a new understanding of black holes, but also to an interesting new question, namely, how do these new properties originate? Many research groups are now studying this question, the answer to which will necessitate an understanding of the microscopic structure and dynamics of the black hole.


Prof. Bekenstein


Are we any closer to understanding what is going on inside black holes? Doubtful. But whatever it is, it is probably even more fantastic than we could imagine.
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Here are some thoughts about time leading to a world without time.

First, What time is not: Look into the world and try to detect time. Our environment is full of time-telling, but the thing told is never in evidence.

David Hume’s consequence-laden observation was that we never actually see a cause, only a constant conjunction of events. So also with time: We never observe it, only changes in space. Time is told either by location in space or by counting in…what? Wouldn’t the natural completion of that phrase be “counting in time?” That’s circular, to be sure, though in fundamental thinking circularities are often revealing, because they display ultimate involvements. In this case how we catch something bears on what it is.

Second, then, What time is: Basically time-instruments are in the analogue mode. Timaeus, in the Platonic dialogue* named after him, says that what we call time is “a certain movable image of eternity…an eternal image going according to number.” (37d ff.) Time is an “image of,” or is analogous to, eternity because it is everlasting and has neither beginning nor end. It is a mere image because it appears as change, and so it doesn’t achieve the undifferentiated nowness of eternity; it is movable as traversing circular distances. Its generating and telling instruments are the visible heavenly bodies. In other words, the heavens both are and tell the time of the world; they are both cosmic time that goes on forever and a heavenly clock that needs no rewinding. The watches most of us wear on our wrists are in turn made in the heavens’ image; they are analogues of the circular motion of the sun (as it appears to us) or of the earth (as Copernican theory persuades us). Whether the time-piece is cosmic or miniscule, it tells time by an indicator, sometimes a heavenly body, sometimes “a hand” moving over a portion of a circle’s circumference. So even a little ladies’ watch is an analogue of the cosmos. There are also in our day digital time-pieces that involve counting and will open a can of worms. I will speak of them later. One difference between analogue and digital clocks comes across in a preference for the round watchface as expressed by a friend of mine who said: “I want to know what time it is, but I also like to see what time it isn’t.” Analogue watches tell time in terms of the everlasting revolutions of the heavens together with the conventional divisions of the human day.

Aristotle picks up on the “going” of the image “according to number”—or so it seems, when we read Book 4 (chaps. 10-14) of his Physics** (which contains his account of time) in juxtaposition with the Timaeus. Probably he clued it out himself. In any case, he puts motion together with number to spectacular effect—the first instance I know of in any writing of time being effectively undone as a something. He doesn’t say: “I’m first; this is a conceptual revolution.” He would much rather make his thinking persuasive by presenting it as a tweaking of thoughtful predecessors. Yet, in brief, he has discovered that time is incidental to change. And since he thinks that all change is at bottom locomotion (chap. 7.7), this means that time is attendant on motion from place to place. Moreover, this motion is numerable. For although it is continuous, it is divisible into even measures at any of the points of the trajectory of a mobile object. Every motion, of course, implies a moving object which generates, one might say, a path, whose diagram is an open or closed orbital trajectory. Then time is the counted collection of all the measured linear units: 12 (EST), for example, is the counted number of dial-measures in which the sun reaches high noon, the zenith of its orbit, from a fixed starting point opposite. Or 13 (years) is the number of the sun’s yearly circuits on the ecliptic, the day after which a young Jew is said to be a man. For motion to be thus countable, it needs to have a recognizable “before and after:” here before, here now, here thereafter. Thus Aristotle defines time in this way: “Time is the number of motion with respect to before and after.”
Here, we might think, Aristotle has gotten himself into deep trouble. “Before and after” are, after all, primarily time-words: past and future divided by a non-time, a span-less, point-like “now.” Thus rewritten, “Time is the number of motion counted according to the progress of time” doesn’t sound very helpful. But Aristotle has a perfect defense: For him every motion that is not violently unnatural is a development of potentiality from implicitness to fulfillment. Therefore every motion—sublunar ones that begin and end and heavenly motions that never cease—every single motion has discernible phases even before time is brought in. So “before and after” can indeed be pre-temporal, as are the implicit stages of a development.

But there is a more serious stumbling block. Aristotle emphasizes that time is the counted number, not the counting number. So if I say “twelve o’clock high” I mean the twelve counted path-segments of the sun’s motion, not my counting thereof. But Aristotle is also quite clear about the fact that there can be no counted number without a counting consciousness. (Aristotle, of course, says “soul,” and so should I, though the word is at present proscribed, and “consciousness” is de rigueur, I think principally because it is from Latin and has three syllables and seems less naïve than “soul,” which is from good Old English and has but one.)

So the counted motion, which is time, requires a counting soul. Here is the problem: The counting soul does not just beat with a steady pulse: one, one, one… That’s what the digital watch does, thereby electronically causing a prescribed series of numbers to appear on a spatially moving dial. The soul actually recalls the pulses accumulated. Its numbering is ordinal: first, second, third. It saves bygone pulses in their order and projects future ones, and it is present, here now, at each moment of counting. But if it is counted motion that is time, then the counting soul is pre-temporal. What then is the substrate of its serially ordered activity? Aristotle, in making time external and incidental, something that is found in nature only as a mere measure, has also made human counting an enigma. What name shall we give the psychic development that directs ordered, ordinal, counting?

One reason why Aristotle has effectively reduced time to nothing in itself is that it is in its conceptual structure dramatically unlike its representational analogue, the linear path, the visualizable trace, of a mobile object. The time-line segment before the now, called “the past,” is gone, erased; the future time path is not yet and invisible; the now is analogous to a point which has, as Euclid says, no parts and “in” which nothing can exist. If you cast yourself into time, you’re done for; there is no time span in which to exist—though plenty of spatial extension in which to move.

Here’s an interesting addendum to the Aristotelian difficulty. It is taken up and solved more than two millennia later in his own terms by Kant in his Critique of Pure Reason (1787)***—not the enigma of existence, namely, what span time’s “no-longer” and “not-yet” leave for us to be in—but time’s particular relation to counting. Recall that Kant thinks that all our experiences, whatever appears to us in an eventually apprehensible way, already comes directly formatted temporally and spatially. But this forming frame is, so to speak, amorphous and beneath awareness. It needs to be brought together (in Greek, “synthesized”) with thinking, with the understanding. Kant assigns to the imagination the mysterious work of joining intuition and understanding, distinctionless time and a determinating concept. Kant thinks that this latter is the concept of quantity, and that when intuited time is made determinate by quantity, counting is the result. The way I put it to myself is this: Time makes its appearance in consciousness by a kind of pulsing that is a now-counting: now1, now2, now3…, or one, two, three…. This analysis seems to me true to experience. Sheer temporal awareness seems to be a kind of pure enumeration of beats—it may actually be our heart-beat felt as a pulse, the throbbing of our arteries following the pumping of the heart. What makes a span of time, time lived through, is having laid up that cardinal count in memory, where it becomes ordinal: first beat, second beat, third beat. Thus the mere beating turns into a first, second, third moment of remembered past.

So Kant solves the problem by bringing time totally within the consciousness of a “subject,” that is, a thinking I. Time is not soul-numbered motion entering into the world from outside, but number itself arises as a conceptualizing of intuitional time within the subject. But then, so does everything within the reach of our comprehension arise within me, the subject; this elucidation of time is bought at the price of near-total subjectivity. Moreover, the deep origin of time as a form of our sensibility, though in us as subjects, is not for us as knower: The grounds of the possibility of our experiential knowledge are not within our experience. Thus one might say that for Kant, too, aboriginal time is a non-being, not a knowable something—that inferred ghost which he calls a noumenon.

Third, What time is insofar as it is anything: So I’ll leap back through the ages to Augustine, who seems to me the greatest phenomenologist of time, that is, the finest observer of the internal experience we have of it, and the first analyst of its elements.

The most comprehensive and acute work on time in modernity that I know of, Husserl’s On the Phenomenology of Internal Time-Consciousness (1893-1917)****, is essentially an acknowledged elaboration of Augustine’s own answer in the Confessions# to his famous phrasing of the enigma of time: “What, then, is time? If nobody asks me, I know; if I want to explain it to someone who asks, I don’t know” (10.14). Augustine allows that we all know time as an experience, sometimes an acutely and deliciously painful one: Here’s Shakespeare, Augustine’s rival in time-consciousness:
Being your slave, what should I do but tend
Upon the hours and times of your desire?
I have no precious time at all to spend,
Nor services to do till you require.
Nor dare I chide the world-without-end hour
Whilst I, my sovereign, watch the clock for you,
Nor think the bitterness of absence sour
When you have bid your servant once adieu. (Sonnet 57)
Who among us has not spent a world-without-end hour sitting by the telephone? Who is not acquainted with the swift “time’s up” of dense experience, short in felt duration, long in remembrance, or the dragging “are we done yet?” of bored disengagement, endless as a happening but miniscule in memory? Or the brute standing still of time in pain? Or the relative pace of experienced time that Rosalind describes in Shakespeare’s As You Like It:
Time travels in divers paces with divers persons. I’ll tell you who Time ambles withal, who Time trots withal, who Time gallops withal, and who he stands still withal. (3.2, 299-302).
That’s the experience described—but now to the experience explained. How does it arise? Here is Augustine’s answer, which I’ll frame as a diagram for you to envision.

Imagine a horizontal line of indefinite length. It represents all the world’s simultaneous motions, its goings-on, from the stars’ revolutions to the mosquitos’ dartings. For Augustine, the Christian, the line must have a beginning, Creation, and an end, Judgment Day. In God’s omnisciently comprehensive sight it is all there at once. But human beings experience it as an extension. Imagine a second vertical line, best drawn orthogonal to the world line, and moving along with it. The moving point of crossing is an “origin.” It represents our mind, existing now, in contact with the world and borne along by its motion. So it is not really a mathematical point but a living moment in a moving world. Later writers, beguiled by Aristotle’s analogy of the temporal now to the spatial point of no extent, will see the need to call it the “specious present.” But it is not a specious—that is, pretend—present, at all, but a real psychic event, albeit a mystery.

Where then in this diagram is past and future? The vertical line represents, as I said, the mind. And the mind has, as Augustine puts it, distentio–its lengthening, its existence, its longitude, we might say. Diagrammatically, it extends above and below its origin, its moment of existence, its contact with the world. The part of the vertical below the moment of existence in the present world represents a build-up of memory-moments, deeper and deeper in the soul, lower and lower on the upright.

Next, all the moments of memory are connectible by parallel oblique lines to the world line that the mind has traversed. If we imagine the forward motion of world and human being progressing toward the right, then the world line to the left of the origin represents motions and events left behind in the past, and each of our true memories down on the “distention” of mind connects to, projects on, a receding point to the left part of the world’s motion line. Of course, scrambled connections (crossed projections) and false memories (wandering projections) can occur. That is how we have a past; the past is a stack of nows now in our distended minds—and all one now in God’s collected mind.

Likewise with the future: Think of it as all the plans and expectations, further and further away from the present, rising upward on the upper half of the mind’s line and projectable by parallel-oblique lines onto the future motions of the world.

That there is in fact a past, though for us only partially and only indirectly recoverable and real only in memory, is common belief; whether there is in fact a real future and how our plans and expectations bear on it is a great theological problem—in fact, the problem of free will. But this much Augustine shows clearly and, I think, truly. He says that we must speak of “a present of bygones, a present of presences, a presence of future things,” (11.2) and continues: “For some such there are in the soul, and I do not see them elsewhere. The present of things gone is memory, the present of things present is sight, the present of things future is expectation.” (11.20, 28) In my words, time is entirely the effect of memory and expectation. Insofar as time is anything, it is a so-called epiphenomenon, an idle, ineffective affect supervening on the real operations of memory and expectation.

But no—“idle” is an inadequate word for our potent sense of time, which is to be understood as our sense of our mind’s longitude, its present lengthening into the before and after of the now of our existence—and of course that fact underwrites, overwrites, potently affects our life.

So now I can zero in on a sense of time that seems to me both spurious and deleterious. It is time not as an internal enlargement of existence but as an external being or force. Continuous time, thought of as being in the world, may be conceived as a continuous stream bearing things along, an absolutely primal, equable flow (of what? we may ask) that is unaffected by anything else in the world; this is Newton’s absolute time. (Principia [1686], First Scholium)+. You may even hear it, as Shakespeare (once again) makes Hamlet speak of one who “only got the tune of time,” a hum conveying its “most fond and winnowed opinions.” (5.2, 183) You may figure it as a linear, open-ended, unbounded mere going-on, or as a closed, ever-repetitive, bounded cycle. In these metaphors, the laws of motion apply indifferently whether time is run forwards or backwards. Or you may imagine the continuous temporal substrate as directed by a forward arrow, a principle of unidirectional change or development that prohibits reversal. This sort of time is not, one might say, “when-neutral;” you might call it change in the abstract, or the substrate of embodied change. In all these forms, some sort of quasi-event or pseudo-motion is imagined as continuous.

The other metaphor, the second figurative way of imagining time is, on the other hand, continual: The now, the present, continually divides the stream of time into gone-by and not-yet-arrived, into past and future. Thus time breaks into a lost past and a not-yet-gained future around a continually new-event-now. This new-now nullifies the past as living; it leaves the passed-away past, so to speak, set in stone. It is, quixotically, both hard-and-fast and intangible: You can’t change it—or so they say. It is indeed, often literally, set in stone; for instance, epigraphy is the discipline of deciphering inscriptions, often found on marbles. Its watchword is saxa loquuntur, “the stones speak.” But does that really mean you can’t change it?

For consider that these testimonials are not past, not in the past. They are in the present, and we must make of them what we can—or will. This curious circumstance, that the past is real only in the present, might be thought of as the incarnation of the memory that Augustine calls “the present of things gone.” You can see that a thoughtful consideration of the past opens a can of worms. What is memory, the storage house of time-expired presences? How invulnerable to change is the memorial past? What about that secondary, often public, memory that is built up from present testimonials of past events? What is more changeable than the past—perhaps even transformable into the present?

But this can of worms is replaced by a bucket of serpents when it comes to the future. For who would doubt that except for a God-inspired prophet, no one can have the future in mind? The future, by the very meaning we attach to it, cannot provide us with any testimonials; it hasn’t happened. All we have are our hopeful or fearful expectations, dim intimations of blessings or harms to come, and uncertain conjectures, projections of our past experiences embellished with change-vectors, their rates and directions of change, and, above all, an impetenetrability made less or more pliable by our weak or resolute will. The will is the human force whose very name announces future-directedness, by means of which we take hold in our minds of the yet-to-be and try to bring it about in the world to our satisfaction. To be sure, we may make vivid pictures of the future, but closer examinations will show that they are, depending on our mood, imaginary recollections from a golden age, or over-the-top distortions of present trends. But they are not images of originals that reside over there in the future—for there’s no there there.

Fourth, and finally: World without time: You can probably tell from my tone, that my desire to cancel time has much to do with the damage that can be done to us by the notion of a real future. Let me now enumerate three elements of a theory that presents time as unreal in the world, as not thing-like, not force-like—a theory by now surely exposed as part of a program of resistance to certain ways of life. Then I will complete my talk by fleshing out briefly these refusals to cooperate with “time.” So then, my three recalcitrances: (a) to the past as passed away, bygone; (b) to the present as mere passage, transition; (c) to the future as an imperative power.

(a) Insofar as the past is the span of time behind us, if time is something real, those spans are really dead, and their relics are mummies, either to be carefully prepared, with ointments of honey or baths of vinegar, to live the museum life of the embalmed departed, or to be discarded upon that notorious rubbish heap of history as no longer “relevant” to our time, the present. Thus, for those of a venerating temperament, the past becomes a silent tomb near which they sit rigidly in. For others, whose dispositions long for change, the past is a spent force, a deadweight on their innovative energy. To neither party is the past, if it is anything, the time-proof treasury that houses all our inheritance of thought and imagination, once human memory has reluctantly let go of what is too delicate, or cheerfully chucked out what is too trashy, for prolonged life. But how the past is properly present to us is a tricky and timely subject for another day. So much can be said in a sentence: Unless we want to cut ourselves out of humanity’s will and remove ourselves as beneficiaries of its estate, we had better give up thinking of the past as having a date of expiration.

(b) Those who feel the past as a march of obsolescence are in fact consigning their personal present to mere transition. For the life-principle of obsolescence is innovation, and innovation is not the heart-stopping or mind-boggling perpetual newness of an imagination-arousing work or a truth-revealing theory or a potent Newness is ever-fresh and invulnerable to obsolescence, because it is not a mere time-marker, a mere date-stamp, on the work of art or on the discovery of an explanation, or on the invention of a contrivance. Newness is rather inherent to these wonders insofar as they break into the ordinary course of on-going life and enhance or redirect it. Time cannot stale its infinite variety.

Innovation, on the other hand, is systematic, intentional novelty, willful newness. In the innovative mindset (this is a derogatory term: fully alive people don’t have mind-sets), small novel differences often trump great solid worth. People succumb to the persuasion that “we live in a time of change,” giving to time an independent power, as if it were an accelerator that puts life in overdrive without the need of my foot on the figurative pedal—a vehicle racing through each present to the next, a car in need of a factory recall. Otherwise put: People accept that they live in “a time of…” and that it is prudent to “get with it,” to clue out what this time-tyrant commands and to do it—in our case, to treat each moment of life as just a bridge to the next novelty. But there is no such time-potentate. There are only people willing to go along—not, to be sure, with the non-existent times, but with what each person thinks the others think, or whither his or her option-dissipated likes weakly tend. What a humanly actual present—I am tempted to say, a time-less present—might be, what, in short, it means actually to exist, is, once again, worth a long conversation.

(c) So then, finally, the future, the chief and least existent venue of real time. You all know the vocabulary of future-possessed. Some say: “The future is here”—really absurd speech; if it’s here it’s too late. They might have meant: Be proactive! Clue out what is coming and preempt or prevent it. The original meaning of “prevent” was “go before,” as in the Psalm 18, in which David is fearfully imagining: “The sorrows of death compassed me about: the snares of death prevented me.” He means “came before me, confronted, me.” (18, 5) In that sense, the anticipation of the future, in literally “foregoing” it, also “prevents” it; it forecloses the future. Human beings are surely entitled, even required, to prevent the future in the sense that by anticipating their version of it they’ll bring it about or keep it from happening—as long as they understand that they are going towards something, an “it,” that is not there to meet them. How we think about our plans makes a great difference: whether we justify our intentions as accepting, managing, and yes, serving, what is coming at us in the false, even craven, belief that there is a real future; or whether we, believing the Future (capital F) to be a false reification, a confusion between an abstraction and a reality, make ourselves think now, in our present, about what is best and most desirable and also humanly possible—and then do that.
And, once again, there is endlessly more to say about the future. But instead of pursuing it, I will end with this observation: Being future-recalcitrant is the very opposite of being reactionary, for the non-existence of the future—or at least our ineradicable ignorance of it—is the very condition of our practical freedom.

This lecture was delivered at the Symposium on Time held at Belmont University in Nashville, TN on September 23, 2014. It appeared in The St. John’s Review (Volume 57, No. 1, 2015) and is republished here by permission of the author, Eva Brann, December 9th, 2015.


* Plato's Timaeus:

** Aristotle's Physics:

*** Kant's Critique of Pure Reason:

**** Husserl's On the Phenomenology of Internal Time-Consciousness (1893-1917):

# Confessions of St. Augustine:

+ Newton's Principia:

I've fleshed out the ideas a bit more by including sites showing or explaining the works of Plato, Aristotle, Kant, Husserl, St. Augustine, and Newton, to further illustrate time from their perspective.

Einstein also said that being in the presence of gravity can affect our movement through the time dimension, since being in a strong gravitational field is the same as accelerating, so we travel more slowly through the time dimension as a result.

Time is complicated.