Of Particular Significance

Why Current Wormhole Research is So Important

POSTED BY Matt Strassler

POSTED BY Matt Strassler

ON 12/18/2022

Once we clear away the hype (see the previous posts 1, 2, 3, 4), and realize that no one is doing anything as potentially dangerous as making real wormholes (ones you could actually fall into) in a lab, or studying how to send dogs across the galaxy, we are left with a question. Why bother to do wormhole research at all?

The answer is that it has nothing to do with actually making wormholes… at least, not in the sense of science fiction portals that you and I could use to travel from here to some faraway place across the universe.  It has to do with potentially gaining new insight into the quantum physics of gravity, space and time.

How Do We Study Black Holes, and Why?

Why do scientists do research on black holes?  There are at least two very different reasons.

  1. Large black holes can be observed in nature.  These black holes, which astronomers and gravitational wave experimenters study, are well-described by non-quantum physics — “classical” physics, where the future is (in principle) truly predictable from the past.  
  2. Small black holes are a window into quantum gravity — the unknown quantum physics of spacetime, where space itself is governed by the uncertainty principle, meaning that the very shape of spacetime can’t be precisely specified.  This is relevant for black holes far too small for us to discover using astronomy, yet far too difficult for us to produce experimentally. They are important because they pose conceptual problems and puzzles for quantum gravity. Theoretical physicists think about black holes, and study their math, in hopes of uncovering quantum gravity’s secrets.

To gain more insight into their workings, scientists also simulate black holes on computers, and study analogues to black holes in laboratories.

Why Wormholes?

In contrast to black holes, there may be no wormholes worthy of the name anywhere in our universe. Though recent research clearly shows that there’s no principle that forbids wormholes from existing, it also shows it’s unlikely that large wormholes can be produced or can endure in our universe. While black holes are a generic outcome of the collapse of a huge star, wormholes are relatively delicate, and difficult to create and maintain.

But wormholes may be even more interesting than black holes for the problems of quantum gravity.  This was only appreciated, slowly at first, over the past 10 years. 

It’s hard to define the quantum state of a black hole. [In quantum physics, objects don’t just have locations and motions; roughly speaking, they have “states”, in which they have a combination of many locations and motions all at once.] The basic obstacle is entropy, a measure of missing information. The air in your room has entropy, because although you may know its temperature and pressure, you do not know where every atom of air is; that’s missing information. It turns out that a black hole has entropy too, which means that our usual description of a black hole is intrinsically missing some crucial information. That prevents us from knowing precisely what its state is.

But surprisingly, in some circumstances the quantum state of a wormhole can be sharply defined — in which case its entropy is zero.  (Such a wormhole is not missing any information. But if you take either half of this wormhole and ignore the other half, you find a black hole. That black hole has entropy precisely because you’re ignoring all the information included in the other half of the wormhole!) To obtain and understand such a wormhole involves giving it two apparently different but actually interchangeable descriptions, one in terms of space-time and gravity, where the wormhole’s geometric shape is clear, and one in terms of what one might call a gravity-independent auxiliary quantum system, in which its quantum state is precisely defined.

The Power of Duality: A Rosetta Stone for Quantum Gravity

One physical object, two quantum descriptions — one with gravity, one without; the first with more space dimensions than the latter.  It’s like being able to read the same text in two completely different languages.  It’s an example of what physicists often call “a duality.” (I’ve gone into more detail about this in recent posts here and here.)

This is the message of what goes by the mantra of “ER=EPR”, referring to two famous and apparently unrelated papers from 1935 by Einstein and Rosen, with the second having Podolsky as a co-author.  ER=EPR asserts that two apparently different things,

  • a tangible bridge across curved, extra-dimensional space between two regions, and
  • a less tangible bridge, established with quantum entanglement between objects in the same two regions, without any use of gravity,

are literally the same thing.

An conceptual illustration of the proposal that two perfectly entangled quantum systems (EPR) are equivalent to a wormhole connecting the locations of those systems (ER), and represent two languages for describing exactly the same thing. The wormhole is empty; the slabs shown merely indicate how distances are shrinking as one proceeds to the wormhole’s midpoint. Not shown is that the wormhole changes shape over time; for the situation in this picture, this wormhole is “non-traversable”, because there’s insufficient time to cross from one side of the bridge to the other before it shrinks down to nothing.

Discovering that spacetime is related to quantum entanglement, and that ER and EPR involve the same issues, is somewhat like discovering that two poorly understood and partially readable texts in completely different languages are actually two translations of exactly the same document.  It’s a Rosetta stone.  Parts of the document can easily be read in one language, other parts in the second language; and putting them together, we find we can read more and more.

Similarly, the math of a wormhole (ER) looks completely different from the math of two quantum-entangled non-gravitational systems (EPR).  But in particular cases, Juan Maldacena and Lenny Susskind argued, they are two languages describing the same object.  We can combine these two partial views of this single object to learn more and more about it. 

Moreover, because we’re using math, not text, we can go a step further.  Even in regimes where we cannot “read the document” in either language, we can use computers to explore.  Scientists can try to simulate the math of the entangled auxiliary quantum systems on a computer, ideally a quantum computer so that it keeps track of all quantum effects, to learn more about the wormhole’s behavior in regimes where we have no idea how it works — in regions where the quantum uncertainty principle affects space and time.

Even more remarkable would be to actually make — not merely simulate — this entangled pair of auxiliary quantum systems. Then we would be closer to making a wormhole, with laws of nature different from ours and with its own gravity, that connects on to our world. But that’s a long ways off, and not the story for the present.

From ER=EPR to Traversable Wormholes

A further breakthrough, beyond the original ER=EPR idea, came with the work of Gao, Jafferis and Wall (see also here and here) in which it was demonstrated for the first time that “traversable wormholes” — ones that can truly serve as bridges across which objects can be transported — do make physical sense.  Astonishingly, they are related by duality to an important and exciting research area in quantum information, called “quantum teleportation.”  That’s the process by which, using two entangled quantum systems, quantum information can be brought to one of the systems, destroyed in that system, and recreated in that second system some distance away. Again, don’t expect anyone to be teleporting your dog, but simple information and ultra-microscopic objects might be transportable. 

Be warned though; the teleportation only works if additional non-quantum information is traded between the two systems. In the wormhole language, that means you can only get through the wormhole if information is also passed outside the wormhole from the departure region to the arrival region.  This makes it impossible to go someplace that you haven’t already been sending messages to, and to use any such wormhole as a shortcut — i.e., to get to your destination faster than could a near-light-speed spacecraft traveling outside the wormhole. Not only do portals to ultra-distant places remain science fiction, they now seem even more likely to stay that way.

Still, with these caveats, there’s still something amazing here: we can now imagine using the Rosetta stone of duality to simulate a traversable wormhole, and learn how it works in quantum gravity. That would be fantastic!

The Dream of Simulating Quantum Gravity

This is a dream, yet to be fulfilled. Computers are nowhere near being able to handle the questions we’d like to answer about the gravity we live with in our “four-dimensional space-time” (our familiar three space dimensions, plus one more for time). But by simplifying the problem in several steps (see the last figure of this post), we can at least hope to answer some early questions in a much simpler sort of wormhole in a simpler sort of gravity.    This is what I’d prefer to call an artificially-simulated cartoon wormhole — rather than a “baby” wormhole, because unlike a baby, it isn’t a small version of an adult, nor has it any hope of growing into one.  It’s more like a stick figure.  It’s in two-dimensional space-time — one space and one time.  That’s a big simplification — there’s nothing like normal gravity there!  [Worse, we don’t have an exact duality in that case; the auxiliary quantum system we need isn’t really the same “text” as the wormhole. These are two systems, not one, with a limited but useful overlap.]

But cartoons aren’t to be mocked.  Don’t underestimate them; cartoons are a powerful tool for educators everywhere, and subversive political cartoons have helped take down governments. For decades, famous physicists — Schwinger, ‘t Hooft, Gross and Neveu, Kogut and Susskind, and many more — have studied cartoon versions of real physics, especially ones in which our four space-time dimensions are replaced with just two. They’ve often learned interesting lessons from doing so, sometimes even profound ones.

[Note: Stick figure physics also can be a very good description of real stick-figure systems, for example a one-dimensional chain of atoms inside a material.] 

I hasten to caution you that this technique does not always work.  Not all of the lessons learned from stick-figure physics turn out to apply to the corresponding real-world problem. But this method has had enough success that we should take cartoon studies seriously.

This is why exploration of one-dimensional wormholes, and of some sort of auxiliary quantum problem to which they might be approximately related, may be worthwhile.  And this is why it’s important to learn to simulate these auxiliary quantum systems on quantum computers, as was done in the paper that generated all the hype, based on proposals made in this paper and this one.  Even if we can’t hope soon to understand how three-dimensional quantum space emerges from quantum entanglement, we can perhaps hope to learn more about one-dimensional quantum space, using quantum computer simulation. Maybe what we learn there would already teach us a deep and universal truth about quantum gravity, or at least suggest new ways to think about its subtleties.

The experiment done in the recent paper is a baby step in this direction.  Others have attempted something along similar lines, but this is the first experiment that seems to have focused on the truly wormhole-like regime, and found some evidence for what was expected already of wormholes (from direct calculation and from classical computers…I’ll write about those details in a future post.) That seems like a real step forward. But let’s keep things in perspective. No new knowledge was created by this experiment; its achievements were technical and technological.  It’s not a conceptual breakthrough.  (I’m not alone in this view; Lenny Susskind, Dan Harlow and Scott Aaronson all expressed the same opinion in the New York Times and elsewhere.)

But nevertheless, this experiment represents a little arrow that points to a possible big future… not a future of a new Elon Musk, building wormholes for fun and profit, but one of a future Einstein, comprehending the quantum nature of spacetime itself.

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38 Responses

  1. Dear Professor, I hope you take Christmas and New Year’s studying a lot …. while your readers takes it with family (thats a joke…forgive me). Continuing with the Levi’s questions above, I ask: 1-about WH, is there any evidence of temperatures within it, such as millions of degrees in supernova or perhaps in pulsars or BH? I ask tjat I just read about JWST, about a nebula/galaxys that has internal millions of degrees (https://www.nasa.gov/Mission_Pages/chandra/images/the-nduring-stellar-lifecycle-30-30 -doradus.html) and like all the cosmic elements that suffer gravity, says density, which warm up as the nuclear reactor called Sun.

    2-What is atomic term heating, that is: a) How gravity warms up atoms in density, makes them vibrate, but why do they vibrate? Does string theory explain it? An extension: If the density, by the pressure pan, do it hot, like a phosphor stick warms, or how fire burns a paper without density? That is, is it not density but the energy transfers? By atomic level, how does it happens? Perhaps this questions explained to all, from SN, BH, pulsars, nebulas, stars, all cosmic things. I never found answers to all this questions and not even at doctorate’s level, in the hope that ST explain all of them. Sorry for my writing. Thanks.

    1. 🙂

      1. First, there’s no evidence that wormholes exist in the wild. If they do, they’re very sensitive, and large amounts of energy can easily destabilize them. But high temperature is over-rated. There’s a big difference between the part of the Sun’s interior which is at 1 million degrees and the part of the Sun’s corona which is at 1 million degrees; the difference in energy per unit volume is enormous. So you simply can’t answer a question like the one you’re asking; simply stating the temperature isn’t enough information to specify the problem or determine the answer. (Just think how different water is at 200 C compared to iron at 200 C.)

      2. There’s all sorts of different questions buried in here and I don’t really understand what you want to know. I think you’d better start in a simpler place, because you’re mixing things up terribly. I suspect you don’t yet understand, for instance, what “temperature” means in a crystalline solid, like a block of iron. First off, in a crystal, all atoms are approximately locked in place. If you move one out of place, it will vibrate around its preferred location, as though attached to nearby atoms by springs. This is true even at zero temperature. Now add quantum physics; even at zero temperature the atoms will vibrate a little bit, that’s called “zero-point motion”. NOW add heat to raise the temperature; this heat will take the form of a certain amount of randomly distributed energy within the crystal, and that will cause the atoms to jiggle — to vibrate — around their preferred positions. The higher the temperature, the more vibration. This will continue to increase until the temperature becomes so large that the bonds that hold the atoms in place begin to fall apart, at which point the crystal will begin to melt and turn into a liquid. Is that all clear to you? Do you want to study this point in more detail?

      To say it one more way: if you create an object in which atoms cannot move around freely — a solid or a slow liquid like glass — then the addition of a little heat, leading to a bit of random motion within the solid, can *only* be in the form of vibration, because there’s nothing else the atoms can do; they’re not able to move in any other way.

  2. I have some questions:
    1. We always think of wormholes as tunnels, but do they have walls?
    2. If they do have walls what happens when you poke that wall?
    3. If they don’t have wall doesn’t that mean wormholes are universes?
    4. Can wormholes appear in wormholes?
    5. If so does that mean the wormholes go up a dimension (square to cube type of dimension), because of the paper analogy?
    6. What is the age of the youngest reader for this website?
    7. How do I get to your blog, you never link it.
    8.when will you finish the book you said you are writing in one of your posts?

    1. 9. How do you edit posts?
      10. What made you first get interested in this field? (If you don’t want too you don’t have to answer 10)

      1. 9. I use WordPress for all blog and website management.
        10. My parents were friends with an astrophysicist even before I was born, and I learned about stars and astronomy from him, so I was already interested in science before I was four. I started to learn about atomic and subatomic physics around the age of 12, and the mix of math, philosophy and reality was the perfect combination for me.

        May I ask how old you are and why you asked (10)?

    2. 1. No, no walls. They aren’t tunnels in that sense, and indeed there ought to be better language one can use. When we draw a two-dimensional picture of a wormhole connecting two two-dimensional regions, the third dimension (which you’re thinking of as a tunnel) is a fake. In that picture, what’s drawn is a two-dimensional wormhole connecting two two-dimensional external regions. We can’t draw a three-dimensional wormhole connecting two three-dimensional regions.

      2. see (1)
      3. no, just a part of a universe that connects other parts
      4. yes.
      5. no. If anything, a wormhole can go down in dimension, but it can only go up in dimension if that extra dimension was already secretly present (perhaps curled up very small) in the regions that it connects. For instance, take the picture of the two two-dimensional regions connected by a wormhole, and far away wrap up one of the dimensions so that it looks as though the wormhole connects two lines.
      6. Gosh. I have no idea. Roughly twelve, I would guess. I have a few articles that pre-teens can read, but not many. But of course there are always extraordinary kids reading way above their age.
      7. I don’t link it because you can click on the title at the top of the website, or simply go to profmattstrassler.com . Also the search function links both to website articles and to blog posts.
      8. The first book will be out in spring 2024 at the earliest. I’m hard at work on it now.


  3. There is to my limited knowledge no evidence that space is “governed by the uncertainty principle” like quantum fields are, and browsing the series of articles the suggested physics is based on an equally untested conjecture.

    But quantizing general relativity on the approximation of flat space seems to yield results compatible with, and with the same effective range as, the classical theory. Thus far the interested bystander – and late quantum field physicist Steven Weinberg himself for that matter – may hope that is the more familiar way forward. [“On the development of effective field theory”, Steven Weinberg, Eur. Phys. J. H (2021) 46:6]

    1. I should add that I find the notion odd also in the way that complementarity of space and time dependencies play out in making classical quantum mechanics of wavepackets imbued with uncertainty principles for some observation pairs. That space depends on space and time on time, and my 2c, gets me no coffee.

      1. “There is to my limited knowledge no evidence that space is “governed by the uncertainty principle” like quantum fields are,”

        In general relativity, the metric is a field, just like other fields. It fluctuates. Therefore all measurements of space and time (which involve integrating the metric along lines in space-time) fluctuate.

        “quantizing general relativity on the approximation of flat space seems to yield results compatible with, and with the same effective range as, the classical theory.”

        If you allow the metric to fluctuate, you have made space and time fluctuate. Period. If you don’t, then you’re not doing quantum general relativity. Whether you choose to formulate the question about a fixed background field does not change this. So I don’t understand what you are talking about.

        p.s. By “X fluctuates”, I mean simply that the measurement of X^2 is not equal to (the measurement of X)^2, which would be true of any classical quantity. Strictly speaking the question should be applied to gauge-invariant quantities, such as the curvature scalar.

  4. Why is the speed of light constant?

    Is it constant below Planck’s scale?

    WRT quantum gravity, is the atom a solar system at a smaller scale? Is the universe a fractal?

    I saw an interview with Susskind discussing string theory and he ended it by repeatedly touching his thumb and middle finger while saying “it may be a matter of string opening and closing. Is that string a tiny wormhole?

  5. “…the unknown quantum physics of spacetime, where space itself is governed by the uncertainty principle…” 

    Am I correct in assuming that, Minkowsky’s famous quote about space and time not existing separately is no longer true: “space by itself, and time by itself, are doomed to fade away into mere shadows, and only a kind of union of the two will preserve an independent reality.”

    As per your sentence above you treat time as a separate entity from space. So there is spacetime, and there is time and space, all separate and independent realities.

    1. It’s a little hard to say, and so I’m going to waffle aimlessly. This is one of the main confusions about quantum gravity. On the one hand, I do mean that “spacetime is quantum”. But an uncertainty principle is about something you measure, and measurements take time — so how do we think about this in a clear, unambiguous fashion? Nobody knows.

      A related point is that the Maldacena conjecture can relate string theory to quantum theories for which there is no notion of space — but there is always a notion of time. Perhaps there is a way to get rid of the time too, but we’re not smart enough yet to think about that. In short, we understand pretty well how space can emerge from nothing, but getting time from nothing is more confusing… how can a world where nothing ever happens be equivalent to one in which something does? There have been proposals (for instance, maybe you have *two* worlds where nothing ever happens, and time is a useful but unnecessary device that gives you a continuous way of changing one world into the other.) Too early to say where this will go.

        1. It is possible. But then it is puzzling that space-time has a universally-respected cosmic speed limit, which is a question of how things travel through space over time — where does that come from?

          1. My WAG: it will depend on how space emerges from the BB and the continued expansion due to DE. These suggest to me space must be emergent from something deeper. OTOH, on the premise some physics provides for the BB, it suggests a “before” to me and a more fundamental role for time. That the proper time for every particle is constant at one second per second also suggests something fundamental.

  6. Matt, I agree with you. 1 D toy models, simulations etc. are better than not doing anything!! So I did not like the heavy criticisms of the wormhole simulation project by many bloggers. One might criticize the hype part. But that work should be appreciated as a toy model if northing else!

    1. Yes, it’s important to not throw out the baby cartoon wormhole with the bathwater here! Even if it is a cartoon baby, it may grow up into a cartoon adult, and might teach us something.

  7. Professor, Is there possible for strings theory explain in total perfection the original EP=EPR idea? How? thanks.

    1. I’m not sure I completely understand the question [the English is a little ambiguous, maybe you should try rephrasing it.] To my mind, the only evidence for ER=EPR comes from string theory (really string/M theory), because Maldacena’s conjecture about field theory being equivalent to a gravity theory can only be correct in the wider string theory, not in general relativity by itself. [This isn’t hard to see; if you remove the D-branes and strings from the gravity side of the conjecture, there are all sorts of physical phenomena in the field theory that you cannot reproduce.] Susskind might argue that this relationship has to be true for any quantum gravity theory, but since string theory’s the only complete one we have so far, I don’t think it’s an argument we could settle.

  8. .”….if information is also passed outside the wormhole from the departure region to the arrival region. This makes it impossible to go someplace that you haven’t already been sending messages to, and to use any such wormhole as a shortcut — i.e., to get to your destination faster than could a near-light-speed spacecraft traveling outside the wormhole……”
    The assumption is that the information about the system would have to arrive or track the system to which it relates in some synchronous or time linked way. Could the universe contain information that had become temporally loosened from its system , which was kind of catching up?

    1. It doesn’t have to be synchronous. But the teleported information cannot be extracted until both the classical information outside the wormhole, and the effects of quantum entanglement inside the wormhole, have both arrived at the destination. Since the classical information clearly can’t exceed the cosmic speed limit for travel from source to destination, neither can the teleported information.

  9. While I’m interested in understanding Quantum Gravity, the mathematical concept of a unseen 4th spacial dimension is to my mind the thing that physics need to grapple with. Subspace as a means of basic communication via entanglement. It’s been a while since I had suggested a physics experiment that might help prove the existence of this dimension of space using the Casimir effect and Van der Waals force with a Cs133 isotope and optical tweezers. FTL communication is possible! This will be one of the greatest discoveries in physics up there with GR and radio communications.

    Thanks for letting me chime in.
    William G Russell

  10. This article is, IMHO, your best that I have read for so many reason, predominately because it gives a path, a more precise scientific method, on how to analyze something as complex as QM and more specifically quantum gravity.

    I still can’t get my head around the duality, there only way I can visualize it is the wave, and it cannot be a “particle(s), will refract over and around barriers, spaces with different index of refraction, and “flow” over to higher potential. Is this what you mean by quantum gravity? Is quantum gravity synonymous to refraction/reflection?

    Thank you for this excellent article, looking forward for the next one on quantum gravity.

    BTW; I wish I knew this stuff 2,500 years ago, lol.

    1. Newtonian mechanics treats objects as having trajectories; quantum mechanics introduces uncertainty and tells us that these trajectories are imprecise — we cannot say precisely where a particle is and where it is going at the same time. Consequence: atoms don’t collapse.

      Newtonian field theory treats fields (such as the magnetic field or the Higgs field) as having definite values at any location and at any time; quantum field theory introduces uncertainties and tells us that these values can never be precisely known. Consequence: the strong nuclear force becomes stronger than you’d expect in Newtonian field theory, traps quarks, and forms the protons and neutrons out of which we are made.

      Einstein’s gravity treats space-time as having a definite shape, and views gravity as a consequence of its curvature; quantum gravity introduces uncertainties and tells us that the shape of space-time (and thus the strength of gravity) cannot be precisely known. Consequence: unknown, but at a minimum it sure makes black holes and wormholes confusing… hence the ongoing research.

      1. “atoms don’t collapse” …
        “the strong nuclear force becomes stronger than you’d expect in Newtonian field theory, traps quarks”, (trapped quarks) …
        “quantum gravity introduces uncertainties and tells us that the shape of space-time (and thus the strength of gravity) cannot be precisely known.”

        I’m sorry, maybe it my engineering background, but every time I have tried to visualize this, i.e. construct a free-body diagram, I keep ending up with the Maxwell–Boltzmann statistics plot.

        Here’s what I mean, your above summary suggests there is definitely a force, quantum gravity, that “traps the quarks”, hence these are the fundamental building blocks in nature. If you assume infinities cannot exist then one path to constructing a free-body diagram is with a superfluid. The angular velocities must be increasing as you go closer the center of the atom, hence creating a force towards the center. So, to achieve “thermal equilibrium”, i.e. the conservation of energy and momentum, there must be six (6) vortices, 6 particles, 3 sets of quark/antiquarks to balance the atom. I left out the neutrons because both the protons and neutron can exist on their own, the neutrons would only make the strong force stronger, but not required to keep the quarks trapped.

        Again going back the Maxwell-Boltzmann statistics, the different sets of Ni are depended on N/Z where Z is the partition function, (index of refraction?), and notice the temperature (energy) goes up as the speeds increase, but the particle count goes down as well, which could suggests there is a void in the center of the atom, (a black hole?) that gives these six (6) forces direction.


        Sorry, I am just a old retired engineer. lol

  11. Dr.Strassler:
    Once again, I enjoyed your write up. Whenever I see an article on a “breakthrough” I always wait for your write up to to clarify the importance, without the hype. On another note, and I hope this is not too off topic, I would like to ask a question about the black hole information paradox. I understand the fact that if I had an apple, I could smash the apple to bits, and in principle, if I gather up all the molecules of the smashed apple, I could reconstruct it….in principle (it may be impossible from a practical standpoint). When an electron & positron come together, they annihilate, their energy goes into two photons, conserving momentum & energy. Now, I assume in principle, you could reconstruct those two particles if you account for all the radiation? When a black hole evaporates, it emits radiation, is the information of the “ingested” stuff not able to be reconstructed from the emitted radiation? Is that why there is “lost information”?

    1. The paradox is that on the one hand it seems reasonable that one ought to be able to reconstruct the apple from the radiation emitted by the evaporating black hole, and we even have some evidence for this from the duality I described — but we still cannot understand in detail how this occurs, and when we try, we hit paradoxes concerning where the information is stored. I wrote about this here: https://profmattstrassler.com/articles-and-posts/relativity-space-astronomy-and-cosmology/black-holes/black-hole-information-paradox-an-introduction/ (though you can skip the last paragraphs about a radical idea of Hawking’s that no one else believed then or believes now.) Maybe try reading it first, and then come back to me with further questions?

  12. I would like to set the record straight concerning “teleportation” Asher Peres with his colleague Bill Wooters defined this term [see “Quantum Theory: Concepts and Methods” by Asher Peres.]
    2. You don’t go into entropy loss;
    actually in Wolf-Reyet stars, one can see entropy restored. Of course you can’t go into everything in one post. Just mentioning what I happen to know.

  13. I’m sorry Matt, but spacetime doesn’t have a quantum nature. Light does, wherein the h in E=hf is Planck’s constant of action. See Leonard Susskind talking about it in the YouTube video “demystifying the Higgs boson”. At 2 minutes 50 seconds he rolls his whiteboard marker round saying the angular momentum is quantized. Since we make matter out of light in gamma-gamma pair production, the quantum nature of light also applies to matter. Hence it applies to QED. But it doesn’t apply to the curvature of light in a gravitational field. So it doesn’t apply to spacetime, or more properly space, and it doesn’t apply to gravity. See my previous comment on your dog/wormhole article where I referred to Einstein talking about Huygen’s principle and “the refraction of light rays by the gravitational field”. Newton thought of gravity the same way. See Opticks query 20: “Doth not this aethereal medium in passing out of water, glass, crystal, and other compact and dense bodies in empty spaces, grow denser and denser by degrees, and by that means refract the rays of light not in a point, but by bending them gradually in curve lines?”

    1. I’m glad you watched Susskind’s video. I went to Stanford and learned quantum field theory and string theory directly from Susskind… and have had many discussions with him about black holes, string theory, and quantum spacetime. So… maybe you didn’t understand what he meant.

      1. I did, Matt. The thing is, once you’ve read what Einstein said about light curving due to a kind of refraction, and once you’ve read “What is Spin?” by Hans Ohanian, you understand how gravity works. Then you understand why quantum gravity is a fool’s errand, and why some concepts in gravitational physics are pseudoscience that one day will embarrass you. See the article I’ve linked to in my details. I wrote it. No problem if you’d prefer not to show this comment, please feel free to email me to talk in confidence.

          1. It’s confidence in the original papers Matt. I would urge you to read them, it will put you ahead of the game. For example Einstein said repeatedly that the speed of light varies with gravitational potential, see the link in my details. The NIST optical clocks provide us with direct evidence of that. Einstein also said that the speed of light at the event horizon is zero. But this just doesn’t feature in what you might call modern studies. As far as I can tell it’s because the Einstein digital papers were not available in the “golden years” of general relativity.

            1. You know, Einstein also got confused and thought that there are no physical gravitational waves. Not all original papers are correct. Meanwhile, there are several hundred people who have been working on this subject full time and who cross-check each other’s work and understanding. These include several Nobel Prize winners and Breakthrough Prize winners. I myself have done quantum gravity calculations to check certain aspects of quantum field theory. So you are indeed showing a level of confidence which has nothing to do with the original papers.

              1. It’s has everything to do with the supporting evidence. I’ve said my piece Matt. Over and out.

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