- Did physicists create a wormhole in a lab? No.
- Did physicists create a baby wormhole in a lab? No.
- Did physicists manage to study quantum gravity in a lab? No.
- Did physicists simulate a wormhole in a lab? No.
- Did physicists make a baby step toward simulating a wormhole in a lab? No.
- Did physicists make a itty-bitty baby step toward simulating an analogue of a wormhole — a “toy model” of a wormhole — in a lab? Maybe.
Don’t get me wrong. What they did is pretty cool! I’d be pretty proud of it, too, had I been involved. Congratulations to the authors of this paper; the methods and the results are novel and thought-provoking.
But the hype in the press? Wildly, spectacularly overblown!
I’ll try, if I have time next week, to explain what they actually did; it’s really quite intricate and complicated to explain all the steps, so it may take a while. But at best, what they did is analogous to trying to learn about the origin of life through some nifty computer simulations of simple biochemistry, or to learning about the fundamental origin of consciousness by running a new type of neural network. It’s not the real thing; it’s not even close to the real thing; it’s barely even a simulation of something-not-close-to-the-real-thing.
Could this method lead to a simulation of a real wormhole someday? Maybe in the distant future. Could it lead to making a real wormhole? Never.
I find it hard to understand why physicists sometimes think it is a good idea to claim more than what they’ve actually done. I don’t know anyone who has ever really benefited from that.
160 thoughts on “[Not] A Wormhole in a Laboratory”
A great (and nicely blunt) analysis, thanks!
I waiting your full explanation. Incredible subjetc. Regards
Where do you come down on ER=EPR and quantum gravity?
I’m looking forward to seeing your take on the paper. For myself I enjoy topology and the unknown mathematical nature of 4d. Of course exclusive of time as a dimension.
All evidence is that the ER=EPR relation (i.e. that wormholes are, in the right circumstances, identical to a pair of quantum field theories in a precisely correlated thermal state) is correct. The basic theory that motivated this study is reasonably sound, and what is not yet sound is plausible. But the actual experiment is very, very far from studying wormholes in four dimensions (three of space, one of time.) It’s an approximation of a system which is approximately equivalent to a system which is a very interesting but still quite distant approximation to a wormhole… and the conceptual relationships between what they studied and real wormholes is, as my friend Arkani-Hamed put it, really in the mind of the theorist, not in the actual details.
What if wormholes don’t actually exist in our universe? Are we forgetting that so far the idea that wormholes exist in our universe is entirely theoretical? Good luck to physicists of the future – who happen upon the correct modification of GR to incorporate gravity – explaining to the general public that no actually wormholes don’t exist.
Like *all* of the coverage of this result has neglected to mention that actual wormholes in our universe is a purely theoretical idea and that it is entirely plausible we’ll discover in the future that they cannot exist.
No one is forgetting this except journalists. The physicists in question are doing a simulation of a theory that is somewhat related to wormholes in a universe which doesn’t obey the same equations as ours… so clearly there is no assumption that wormholes are possible in our own universe.
That said, all the evidence of the last ten years or so is that extremely microscopic non-traversable wormholes are probably generic in any theory with gravity and quantum physics. So my guess is that they do exist, for brief moments and/or in extreme conditions. It is much less likely that wormholes that anything can travel through exist, and even less so that macroscopic wormholes exist.
In any case I do not imagine anyone will ever try to make real wormholes, even microscopic ones, in a planetary lab. That would be extremely dangerous.
No, it isn’t just the journalists it is the physicists. The Quanta magazine produced video accompanying the article has numerous quantum gravity theorists going on at length about the “wormhole” created by this experiment without nary a peep that – in fact – ER wormholes for all we know do not exist in our universe. One of the authors claims this experiment is as meaningful as the Higgs discovery…#$(#*($&#! The video is replete with physicists – not journalists – going on at length about wormholes. Someone coming away from that video who wasn’t versed in the bullshit peddled would conclude that it’s been proven that our universe has wormholes. That this isn’t even a question anymore???!.
As for the evidence of the last ten years… sure, if by “evidence” you mean a lot of smart quantum gravity researches fondest wishes is for ER=EPR to actually be true or that AdS/CFT really has something to say about the theory of quantum gravity that our de Sitter universe obeys. I’m not aware of a single observation or experiment that would in the slightest give credence to these fondest wishes. Nor am I aware of a single prediction made by AdS/CFT or ER=EPR that can be tested or observed to find out.
It seems very evident that theorists have run out of ideas much like the string theory program itself. Otherwise why the bullshit hype?? Wishing it were not the case doesn’t make it so and the skeptical takes on this result should state clearly and up front that for all we know ER wormholes don’t exist in our universe. Doing so, upfront, would squash immediately all the talk about whether these so-called “wormholes” created in the experiment are “real”, or “simulations”, or “emergent.” They are mathematical fictions of some theory that for all we know – beyond fondest wishes – have nothing to do with our universes actual physical law of quantum gravity.
Fleischmann and Pons
No, that’s a different category. Fleischmann and Pons’ experimental claims were actually *wrong.* I don’t have any reason to think this experiment is wrong. Nor does the paper itself over-claim what was actually done. It’s just that some of the physicists are saying unjustified, over-the-top things to the press, making it seem that they did something that they (and we) know perfectly well they did not do.
“why physicists sometimes think it is a good idea to claim more than what they’ve actually done. I don’t know anyone who has ever really benefited from that.”
Obviously, for to claim more grants. For example many benefited from claims they already know what DM is, they just need money to prove it.
Creating hype is known trick.
This is the 21st century. You can’t fool people with false claims; the debunking happens on the internet in real time. Government granting agencies may be wrong sometimes, but they’re not stupid. It’s one thing to say: with this experiment, we show that quantum simulation will be a powerful tool for studying quantum wormholes, so give us more money; that’s an argument and an opinion, but it might be correct, and funders might well accept it. It’s another thing to say: with this experiment, we built a tiny wormhole in a lab; that’s factually false, and funders might well recoil from it.
Is a wormhole analogous to superconductivity? Is it possible, even theoretically possible, for the fields / particles in vacuum to align / polarize to create a “bridge”, channel through which entangled particles can transverse without any interference?
@OakTree Leonard Susskind came up with entanglement-as-wormholes by starting with Einstein-Rosen (ER) bridges. Far from being the gigantic Devil’s, um, Orifices of Marvel Comics fame, the original Einstein-Rosen bridges were tiny wormholes between two parallel universes. They were intended to model fundamental particles such as electrons.
The ER paper wasn’t forgotten so much as it was kindly overlooked by those who did not wish to embarrass the aging Einstein, who was getting a bit desperate for a win with his unified field theory. To write the ER paper, Einstein had to abandon the energy implications of his own General Relativity theory. The paper instead treats spacetime as a sort of magic putty that one can bend into almost infinitely sharp angles without paying any energy or stability price.
The Devil’s Orifice ER bridge of Marvel Comics fame is kinder and more respectful to Einstein’s memory, since it, at least, scales up particle-sized wormholes to sizes that no longer require more energy than exists in the universe just to create one electron.
Leonard Susskind is a brilliant and always-enthusiastic fellow. I continue to hope that some day he will apply his impressive skills to ideas that, unlike superstrings and infinitely pliable “ER” spacetime, take energy balancing more fully into account.
I don’t know about the “stability price”, but there doesn’t need to be a energy implications since the particles in the “bridges” would be stretched, scaled up redshifted, (stretched time?), to maintain energy conservation.
Another very useful application for man made wormholes would be nuclear fusion reactors. Can the hot plasma be contained in a continuous 360 deg wormhole around the chamber?
Regards, retired engineer 😎
Math is uncomfortably like programming. Just because one can write out many terms and attach emotionally impactful words to them, say, in a $10,000 pay-to-play journal article — and yes, sadly, that is a thing these days — it doesn’t mean the result is valid or makes sense.
Valid physics math comes from what folks like Matt Strassler does here: Validate the formal model against experimentally collected data to see whether it does or does not accurately and concisely predict how the experimentally accessible universe responds in well-defined situations.
I have no doubt the folks involved super-small wormhole speculations use words like “redshift” to explain away problems. Alas, such phrases are, at best, tasty word dressing on top of a ghost salad.
On the contrary,Terry, what the ER=EPR paper does is show that Einstein-Rosen bridges make perfect quantum sense, at least in supergravity (and approximate supergravity.) Energy is certainly balanced in these examples.
Matt, thanks. Mostly to avoid WordPress “spaghettification,” I added a technical answer on the main thread, with links to and brief quotes from the relevant 1935 and 2013 papers. It’s not shown up yet. I’ll wait a bit and reply to this subthread if nothing appears.
Meanwhile, here’s a nice Nature press-hype article on the paper:
Nature NEWS, 01 December 2022
Did physicists create a wormhole in a quantum computer?
For anyone interested, here’s the original 1935 ER paper:
A. Einstein and N. Rosen, The Particle Problem in the General Theory of Relativity, Physical Review 48, 1 (1935).
A few relevant quotes are:
“Every field theory, in our opinion, must therefore adhere to the fundamental principle that singularities of the field are to be excluded.”
“To interpret (1) in the framework of this theory
ds^2 = -dx_1^2 – dx_2^2 – dx_3^2 + a^2 x_1^2 dx_4^2. (1)
we must approximate the line element by a slightly different one which avoids the singularity g=O. Accordingly we introduce a small constant σ and let
ds^2 = -dx_1^2 – dx_2^2 – dx_3^2 + (a^2 x_1^2 + σ) dx_4^2. (1a)
the smaller σ(>0) is chosen, the nearer does this gravitational field come to that of (1).”
“The four-dimensional space is described mathematically by two congruent parts or “sheets,” corresponding to u>0 and u<0, which are joined by a hyperplane r=2m or u=0 in which g vanishes.(2) We call such a connection between the two sheets a 'bridge.'
(2) Because of the symmetry about the hypersurface g=0, the sign of g does not change at this hypersurface."
Here's the 2013 Maldacena-Susskind paper that introduced the idea of wormholes as entanglement mechanisms:
J. Maldacena and L. Susskind, Cool Horizons for Entangled Black Holes, Fortschritte Der Physik 61, 9 (2013).
The main argument is referential:
"…general relativity allows solutions to the equations of motion that connect far away regions through relatively short "wormholes" or Einstein Rosen bridges " (where  is the 1935 ER paper)
No. General relativity does not allow such solutions unless one performs an ex Machina solution to eliminate the singularity problem, as ER did in their 1935 paper's attempt to create neutrinos out of tiny cross-universe bridges — and as others have noted, these are not the same as in-universe wormholes. Einstein profoundly altered his GR theory by assuming this "small" change — not to mention a parallel universe — to get rid of singularities.
Matt, you also make the interesting point that: "bridges make perfect quantum sense, at least in supergravity (and approximate supergravity)."
That's interesting, but what experimental proof exists that supergravity is more than an incomplete (gravitons) mathematical abstraction?
Also, more broadly, supergravity is just one more of many frameworks — QED is another, to be fair — assume infinite mathematical resolution and information density as givens. The assumption that the _physical_ universe "must" be infinitely differentiable unavoidably makes the same assumption.
The difficulty is that the physical universe doesn't behave that way. Information density in all experiments remains stubbornly finite, though the universe provides powerful options for approaching certain well-defined limits indefinitely closely if you add enough energy (e.g., via the LHC or cosmic ray particles).
Ok, lets shake the basket a bit, given the huge size of the universe and more specifically, the vast “empty voids” filed with nothing but fields of very low quantum oscillations, is it possible that the number of wormholes in these voids are practically infinite. Further, they could be opening and closing that these “bridges”, channels are what causing the quantum oscillations in the first place.
If this wild theory is true, I’m an experiment can be done to prove it. Maybe these wormholes exist in a collimated beam of light, a laser beam?
As a retired engineer with 30+ years in human space flight, I have to congratulate this generation of physicists, you guys are on a roll the last couple of decades, while my profession has been in the lagging for decades. It seems you guys are stealing all the bright grads.
Since short replies work, my best guess is that Akismet is auto-flagging my external links to the Einstein and Susskind and requiring a review by Matt Strassler. Your call, Matt.
Akismet certainly flags large numbers of links, since that is a common technique of crackpots.
“That’s interesting, but what experimental proof exists that supergravity is more than an incomplete (gravitons) mathematical abstraction?” I’m not addressing an experimental question. I’m addressing the theoretical consistency of Maldacena’s conjectured equivalence. As a quantum theory, supergravity makes sense as a low-energy limit of superstring theory, and all evidence is that superstring theory is theoretically consistent. So Einstein-Rosen bridges appear to be quantum consistent if the Maldacena conjecture is correct, as long as the bridge is formulated in string theory or one of its low-energy limits.
That’s a completely separate question as to whether supergravity plays any role in the real world, and could be observed in a real experiment. And it leaves open the question as to whether Einstein-Rosen bridges can exist in the real world.
What Jafferis has done in his theoretical work, however, is show that microscopic traversable wormholes are related to ordinary quantum teleportation, and we know that the latter is possible in the real world — so there is reason to think that some kind of ER-like bridge makes sense in some kind of string theory. Details are far from clear at this point and there is active ongoing research which I haven’t been following closely enough to tell you about yet.
Matt, thanks, nice points!
>… all evidence is that superstring theory is theoretically consistent
I know you and many, many folks — less so these days — say things like that with complete sincerity and confidence. But seriously, what does it even mean?
QED is a theory that makes predictions. GR is a theory that makes predictions. Superstrings were a plausible but incredibly risky (20 orders of magnitude!) S-matrix (“math is reality”) hyper-extension of extremely solid, intensely data-based hadronic string theory. The superstrings hypothesis unfortunately popped up just before folks realized quarks are the balls and flux tubes the strings behind all those lovely vibrating string solutions. Tweak that unfortunate historical sequence just a smidge and “superstrings” either never would have existed, or would have died after about five papers showed strings had been preempted by quarks and flux tubes and that no comparable string-like forces existed at the Planck scale.
Plus, seriously, how can any formal structure so utterly disconnected from experimental constraints that it predicts at least 10^500 vacuums be called a “theory” of anything? That’s like declaring the Roman Alphabet to be the ultimate Theory Of Everything because, somewhere in all of its possible combinations, the actual Theory Of Everything things must surely exist.
I’m sorry, you’re very confused about how theoretical physics is done, and why it is done that way.
In the end, we want to explain and understand the real world. But one of the best tools for doing this is to explore other possible worlds and see how they work. Are you suggesting that ‘t Hooft was wasting his time when he solved the theory of quarks and gluons in 1+1 dimensions? Or that Nambu was wasting his time when he considered what we call the Nambu-Jona-Lasinio model? These were not models that were intended to be compared with experiment; they were models that were intended to help us understand our own tools — namely quantum field theory — better than we did at the time.
Also your “superstrings hypothesis” history is both totally wrong (as you’ll see in my next post) and completely irrelevant. Superstring theory is an important tool in theoretical physics, and it does not matter when or why it was discovered, nor is its importance diminished if, in fact, it has nothing to do with nature. You’re living in the Brian Greene/Peter Woit hype world, which is also purely theoretical and has very little to do with how superstring theory is actually used by the community these days. A theory can have nothing to do with the real world and still provide powerful technical or conceptual tools for future research.
The purpose of all this wormhole research is *not* to create wormholes in a lab, or predict something that we can measure in an experiment. It is to teach us how wormholes specifically, and quantum gravity in general, really works. It’s not obvious (it never is, in research) how much we’ll learn from this approach. But theoretical physics has many tools and strategies, and they’re not all about “make a prediction for an practical experiment.” There are often many steps along the way.
“Superstring theory is an important tool in theoretical physics, and it does not matter when or why it was discovered, nor is its importance diminished if, in fact, it has nothing to do with nature.”
That makes about as much sense as saying the theory of the Ether was an important tool of theoretical physics! If superstring theory has nothing to do with nature, then it isn’t physics full stop! If that is the case, then superstring theory was a failed thought in theoretical physics. Physics is the study of the natural world and something that has nothing to do with that natural world is not physics.
“A theory can have nothing to do with the real world and still provide powerful technical or conceptual tools for future research.”
Only if that future research has something to do with the real world! If it never collects on your *bet* that it will have something to do with Quantum Gravity – which is the bet you are placing here, let’s be clear and not materials science – then it will have been a wrong avenue just like the Ether.
“It is to teach us how wormholes specifically, and quantum gravity in general, really works.”
Which might not pan out. So far it actually *hasn’t* panned out. People working in the field should be honest about this with themselves and with others. All we have is the *wish* that it will. It might not.
Who is being dishonest here? I have said numerous times that this is a strategy, and not all strategies work for all problems. Please do not accuse me of dishonesty unless you have clear justification for it. And **of course** the research should have something to do with the real world; that goes without saying. Otherwise it’s mathematics.
Now: if you do not understand my point about superstring theory’s usefulness, then this shows ignorance and a lack of imagination. Let me give you an example from last week. I was trying to make a prediction for the Large Hadron Collider as to what would happen experimentally if a certain theory of the Higgs field (called the “Fraternal Twin Higgs”) were true in nature. In order to do this, I needed to know whether the particles that would be created at the LHC would travel a distance larger than a millimeter before annihilating and exploding into a large number of other particles. This makes a big experimental difference in terms of the search strategy. Now, it happens that the particles in question are connected by a flux tube — a sort of string. I need to calculate how long it takes for this flux tube to radiate away its energy, following which the particles connected by this tube will form an atomic-like state and eventually annihilate, because that determines how far they travel. What method do I use? Well, there’s only one. I look up papers like this one: https://arxiv.org/abs/hep-th/0601072 , the “Handbook of String Decay”, which I can use to estimate how long it takes for a flux tube of the particular sort I’m working with to lose its energy. These calculations were done using superstring theory. So — there you have it, I have made a prediction for the LHC using superstring theory… absolutely relevant for the real world, even though the technique I used involved a mathematical tool that may not be. Why does this work? ***Because flux tubes are real, even if superstrings are not*** — and the physics of flux tubes is most easily estimated through the approximation that they act like strings, and whether they’re strings or superstrings doesn’t change the qualitative answer that I need. (In particular, I can easily see from the handbook that either these particles travel far less than a millimeter or the particles to which they will annihilate will unfortunately be undetectable for other reasons.)
So listen and learn, my friend. I have thirty years of experience; you have none.
Let me give you another example. One of the big problems in physics today is the question of why the Higgs boson and other particles are so light compared to the Planck scale. I invented a new way that this could happen, by showing that the standard rules that we’ve always assumed quantum field theories adhere to can be violated in quantum field theories that we hadn’t previously considered: https://arxiv.org/abs/hep-th/0309122 . Why hadn’t we considered them? They were too hard to calculate or simulate, so we simply didn’t know how they behave. How did we discover how they behave? Using superstring theory, through the so-called AdS/CFT or “gauge/string” correspondence of Maldacena.
Data from the LHC now shows that this idea for the Higgs field is not true in nature. But it was a perfectly good idea, and worth looking for at the LHC. We would not have known it was even possible without superstring theory.
In future, new forces may be discovered, and they may behave quite differently from the ones we know. Again phenomena from such forces might include the one that I just described. They might also include a very strange phenomenon typically described these days as “SUEP” (soft unclustered energy patterns) for which searches are underway at the Large Hadron Collider. We would not have known SUEP was possible without superstring theory, as I discussed here. https://profmattstrassler.com/2022/03/20/a-prediction-from-string-theory/
The same general statements can be made about supersymmetric theories more widely. These theories have the disadvantage that they probably aren’t the real world, but the advantage that questions that are extremely difficult in non-supersymmetric theories are sometimes much easier in supersymmetric ones. When you discover a phenomenon in a supersymmetric theory, you can ask if it might occur more generally.
So your notion that somehow, if it isn’t exactly the real world, it’s useless, is neither true nor wise. Large-N gauge theories aren’t real, but they taught people to organize their thinking in a 1/N expansion, which has proved hugely useful. The Nambu–Jona-Lasinio model isn’t real, but it taught people how to think about chiral symmetry breaking, which is certainly real. You need to learn more scientific history. The use of “toy models” throughout the subject has a checkered history, but by no means should such methods be downplayed, disregarded, or discarded altogether.
No one accused you of being dishonest. I was just responding to your words and in no way implied dishonesty on your part.
“And **of course** the research should have something to do with the real world; that goes without saying.”
You said otherwise. Perhaps you didn’t mean your words or would state them differently now, but makes little sense to be upset when you said, “Superstring theory is an important tool in theoretical physics, and it does not matter when or why it was discovered, nor is its importance diminished if, in fact, it has nothing to do with nature.”
“I have made a prediction for the LHC using superstring theory… absolutely relevant for the real world, even though the technique I used involved a mathematical tool that may not be.”
Good for you! But this is clearly a case where superstring theory had something to do with nature. You are the one who said it would still be important if it *had nothing to do with nature* not me. Those were YOUR words, not mine.
Regardless, for the purposes of this post and your reply we’re talking about whether or not superstring theory has anything useful to say about *Quantum Gravity* not your flux tubes or materials science. You can try and change the subject, but it has no bearing on your argument.
“So listen and learn, my friend. I have thirty years of experience; you have none.”
Ok, so you get upset about an phantom accusations of dishonesty and now want to be patronizing with your appeal to authority for a non-sequitur of an argument re: whether superstring theory or AdS/CFT has anything to do with the actual theory of quantum gravity. Poor showing.
Sorry that you took offense. I’m not upset at all, just frustrated with ignorance.
You are right that when I said “it has nothing to do with nature” I should have said “it has nothing directly to do with nature.”
As for your statement: “for the purposes of this post and your reply we’re talking about whether or not superstring theory has anything useful to say about *Quantum Gravity*”, that’s not true. That’s what you and Terry were talking about. My whole point is that this is very limiting.
Now, as for whether superstring theory has something to say about quantum gravity : calculations in superstring theory have shown that there are corrections to Hawking’s entropy formula in quantum gravity theories. Also they show that in many cases the Hawking entropy formula can really be interpreted as counting the microstates of a black hole. Aren’t these things worth knowing even if superstring theory itself turns out to be the wrong theory of quantum gravity? Again, if there are things that are true of *all* quantum gravity theories — and there might be many of them, just as there are many things that are true of all quantum field theories — then the fact that string theory is one of them allows us to discover these properties of quantum gravity even if string theory itself is the wrong theory of nature.
Matt, you’re making up non-sequitur arguments to back up your words. The only question here is whether superstring theory or AdS/CFT has anything to do with the actual theory of quantum gravity in our universe.
It’s wonderful if you can user Superstring theory or AdS/CFT to accomplish solutions to *other* physical questions that have nothing to do with quantum gravity. Bully for you! However, this does not say anything about whether it is good for the question before us: Quantum Gravity.
Not once did I poo poo the usage of toy models in physics or belittle the history of such toy models often turning out to be useful in teaching us about theory space. You’re arguing with a phantom not what I’m actually saying.
“So your notion that “if it isn’t exactly the real world, it’s useless” is neither true nor wise.”
When you use quotes to rebut another person’s argument please have the courtesy to use *actual quotes* not made up phantom’s of your own conjuring.
I’m aware of those purely theoretical results. They are good work and might well pan out. But
– crucially – they have not yet. It is *still* the case that we have no idea whether they will or not. In other words, it is *entirely conceivable* that in the actual theory of quantum gravity, those calculations involving superstring theory shed zero light whatsoever. It is an open question to decide whether superstring theory or AdS/CFT have anything to say about the still unknown theory of quantum gravity that undergirds our universe. It could very well turn out that they don’t! I’m just asking for quantum gravity researchers to be up front and open about that fact with the general public. That is entirely something missing in the experiment that motivated this blog post.
The purpose of this blog is to be as up front and open as possible about the science. We are in agreement about the hype.
But in a way, your request is a straw man: of course I agree with it. Among theorists, this goes without saying. Any theoretical result in any theory that has not yet confronted experiment comes with the same asterisk: “caveat emptor until experimentally confirmed.” Everybody in the field knows this is true, which is why they don’t say it over and over; it’s like the fine print on cigarette ads.
Indeed, the problem here is not irresponsible theorists. The big hype in the press about this experiment is coming not from the theorists but ***from the experimenters.*** Daniel Jafferis, a young genius whom I have known for a decade, is a very responsible fellow and would not disagree with you at all. I’m sure his opinion is that these questions of quantum gravity are very general and that his work is probably relevant for the real world in some way. But he’s not the one out front, talking to the public, claiming these are real wormholes.
If your point is that the hype, driven by the experimenters, is outrageous and unacceptable, well… obviously I agree completely.
Hi Matt, I didn’t come to argue with you and your last post in this thread is eminently reasonable. Only reason I responded in this thread is because what you wrote struck me, but I suspect it wasn’t what you mean. Whatever, I don’t need to belabor the point. For sure though, I wasn’t accusing you of being dishonest. This blog post is a skeptical one and helps to battle the unfounded hype associated with this particular experiment. Who would want to argue with that?
Still. I’m trying to make one point that I think is important. Let me try again… First, I’ll take your word for the fact that the experimentalists are to blame and not your theoretician friend.
The point I’m trying to make is that the *general public* – after years of being inundated with sci-fi stories, theoretical stories of wormholes, etc have most likely forgotten that wormholes are not experimentally or observationally confirmed and in fact are not even a falsifiable prediction of our current best gravitational theories. Then this article comes along with the words “experiment” and “wormholes” and please forgive them if they think wormholes – even with the skeptical pushback seen here and in other blogs/twitter comments – are a confirmed feature of our universe. After all, how can we even have the debate about whether these wormholes are “real” or not if it isn’t the case that *some* real wormholes exist in nature!
That’s all I’m trying to point out. That physicists – even the skeptics like you who are doing god’s work here in debunking this hype – might want to take into account that the general public likely believes that wormholes are an inevitable outcome of our current best theories of physics: GR and the standard model. And if I’m right and the general public thinks this, then the first thing you can say in your pushback in the future is that, in fact, wormholes might not even exist in our world according to all we know and thus short circuit the whole debate whether these “wormholes” are real. That’s all.
I agree that any disagreement here was born from misunderstanding each other’s assumptions and phrasing.
Your general point is one I will keep in mind, but let’s discuss it a bit more. The issue has to be dealt with in stages.
It does seem that wormholes do exist in *some* universes. That is really the message of the recent work. Before ER=EPR, I would have suspected that wormholes don’t exist in any type of universe, but apparently they do; and until the more recent work, I would have suspected that traversable ones don’t exist, but apparently they do.
That does not mean we know for sure they can exist in *our* universe… they’re fun to think about, but hardly guaranteed either practically or conceptually.
Also, if I understand correctly, even in the imaginary universes where it’s been shown they likely exist, nothing could travel through them faster than light sent *outside* the wormholes from one end to the other, because you need a “classical channel” to implement quantum teleportation. Also, nothing macroscopic could travel through, as the extreme perfection required by quantum teleportation requires the system be perfectly isolated. So even in these imaginary universes, these wormholes are hardly those of science fiction.
However, there is a possibility that your point is wrong. Here’s the question: if I made a black-hole/anti-black-hole pair in a high-energy photon-photon collision, as perfectly quantum-entangled as an electron and positron pair created in the same way, would they *automatically* (through the entanglement) act like a wormhole? This question might have nothing to do with the specific requirements of a quantum gravity theory, and might instead be a consistency requirement *imposed by quantum mechanics on semi-classical gravity*. You see, in that case it’s not a quantum gravity question, and so, in this limited sense, your point may actually have been addressed. This is something I’ll try to think about further and discuss with the real experts.
By the way, I addressed some of the fictional aspects of wormholes (though I didn’t quite make the point you’d want) for a completely different reason, in https://profmattstrassler.com/2022/08/17/could-cern-open-a-portal-to-somewhere-anywhere/
Indeed, it’s not the real thing. Of the real thing we know the how and why 🙂
ER = EPR is a conjecture in physics stating that two entangled particles (Einstein–Podolsky–Rosen or EPR pair) are connected by a wormhole (or Einstein–Rosen bridge) and is thought by some to be a basis for unifying general relativity and quantum mechanics into a theory of everything.
The conjecture was proposed by Leonard Susskind and Juan Maldacena in 2013. They proposed that a wormhole (Einstein–Rosen bridge or ER bridge or #PenroseStairs) is equivalent to a pair of maximally entangled black holes. EPR refers to quantum entanglement (EPR paradox).
At 2D, the Dialectical materialism (or towards ‘decrease in entropy’) is a “Pair of quantum field theories in a precisely correlated thermal state”. But the 2D + 2D = 4d, exclusive of time as a dimension, in the original Einstein-Rosen bridges (Penrose stairs?) were tiny wormholes between two parallel universes. They were intended to model fundamental particles such as electrons (electronics, the base of Holographic principle).
Spacetime is not a “magic putty”, but the actual experiment is very, very far from studying wormholes in four dimensions (three of space, one of time or #MindBending, a #Kantian ‘Transcendental idealism’, of course not a #MagicRealism).
In “Gravity’s long-distance connection”, the conjecture (Energy is a form of Space but Space is not the Energy?) leads to that the geometry of space, time and gravity is determined by entanglement.?
The label “science” may encompass lots of activities, from 5 sigma particle accelerator experiments to n=0 thought experiments and mostly BS conjectures. It’s all OK but people need to understand the difference. Natalie is a great journalist but she has been a press conduit for the n=0 BS part of the physics community for a long time and she just got burned for that business decision .
Well, that might be a little harsh. The hype, as I said, is way over the top — but this *is* a nice paper.
So nothing is “science” until it reaches 5 sigma ?
ER=EPR is a kind of a misnomer: An Einstein – Rosen bridge is the non traversable wormhole that is associated with the spacetime geometry of an eternal black/ white hole solution that is static in the exterior ( r >2Gm) and time dependent for r<2Gm. It " connects" two different asymptotically flat regions.
As far as I know, a "wormhole" in the ER=EPR conjecture is supposed to connect a pair of black holes that originated from collapse of entangled stuff and of course it's not past- eternal. Also the pair is supposed to be in the same spacetime region, not in two different ones. But, anyway, this is an "established" misnomer, so what can we do..
As for the paper, I have the suspicion that the reasoning involves some kind of circularity, but maybe I'm wrong. I'm also looking forward to your elaborated comments on this in some future post.
Perhaps it will address my queries.
In the ER=EPR context, the strict statement of the original paper is that there is an eternal wormhole and that it is precisely equal to two separate but identical quantum field theories in a pefectly entangled thermal state (the “thermofield double state”.)
The modification to make the wormhole traversable is that there should be an appropriately chosen interaction between these two quantum field theories in addition to their entanglement. This is just what one does in quantum teleportation, where some kind of entangled state, plus some classical information, allows something to be absorbed by one quantum system and emitted by the other one.
well professor, you gave us an unequivocal explanation !!
Just a very, very thin one — more a caution than an explanation. I will indeed give you an explanation but I have a lot of review and reading to do as I haven’t been working in this area myself.
Here’s a nice Nature press release on the paper:
The original link that Matt Strassler provided was:
Judging from the articles ( Quanta/ Nature) and the promotional video, I’m not sure that only the experimenters are responsible for all these intentionally ridiculous claims, as you seem to suggest in a previous comment.
It’s hard to believe that others involved do not have ( more or less) any responsibility for this. Moreover, it’s obvious that there was a preparation for this hype “attack” for days. For example, there were some laughable rumours that “scientists created a …mini black hole in the lab”! in some obscure “sources ” that nobody paid any attention before, because they were obviously and blatantly ridiculous.
Even if this whole story is more hilarious than sad, there’s a real worry that concerns many people, especially with all this anti- science propaganda and the like…
Well, judging from (1) the quotes that actually appear in the media articles making the claims, and (2) my own conversation with the leading theorist involved… I maintain my view, for now.
Meanwhile I was visiting the Institute for Advanced Study this week and there was universal scorn expressed by the theorists there. In fact the most famous of them in this subject pointed out this paper https://arxiv.org/abs/2205.14081 which did something very similar, only without the hype.
Hi Matt Strassler,
I gave up and read the paper and even have some positive comments.
First, though, I’m sorry for triggering a subthread that got a bit heated. It was not my intent, and I would not have been offended. Reading it mostly made me smile and say, “ah, oops.”
One question, though: I stand by my assertion that Einstein’s “small” change to GR in the ER paper gutted GR at the nanoscale, allowing him to say things flatly not true in textbook GR. It’s not the same theory, and I strongly suspect folks at that time were aware of that.
I don’t remember you responding to that. Do you agree? You know the math better than me. As best I could tell, Einstein said, “I don’t like the singularities that pop out of my general relativity theory, but hey, if I add a constant in here, they disappear!” Um, ouch. Susskind should make it clear to folks that when he says “ER=EPR,” he is _not_ talking about the General Relativity of textbooks.
You are right to say I don’t understand modern theoretical physics. I’ve studied for years and decades how not to be a theoretical physicist. It takes effort, but I’ve made some progress. For example, I no longer believe in MWI, infinitely dense vacuums, infinite differentiability except as an asymptotic limit in high-mass systems, or casual violation of energy conservation. There’s hope for me!
Back to the paper: I didn’t realize these folks have an experimental result that seems non-trivial. That makes this a lot more interesting. The gravity connection feels like complete hand-waving nonsense to me, like vaporous cotton candy wrapped around the solid core of an authentic quantum experiment. But then, I don’t think like a theoretical physicist.
It sounds significant if the (entirely quantum, not gravitational) negative energy shockwave aspect of their work can be independently verified. Unfortunately, they have, in effect, buried that non-trivial experimental result in all this “wormhole sim” noise.
So let me suggest a less radical interpretation: If the negative energy shockwave signal these folks are detecting can be independently verified in other experiments, what these folks may be detecting is not a simulated gravitational wormhole but an experimentally real quantum time machine.
The authors seem to take the Wheeler-Feynman-ish tact that negative energy is associated with travel backward in time. If our universe is mostly frame-independent empty space with a smattering of positive energy, time moves forward mostly because we’re part of an overall positive energy thermodynamic consensus. The negative energy still exists — I would even suggest it plays a role in driving the forward motion of time — but it’s always and necessarily in the quickly-extinguished minority.
My best reading so far — and I must read their paper more closely — is that this group stretched out the interactions between positive and negative energy fronts enough to make the gap detectable by sending some quantum correlations from the present into a very recent past. In the ER paper, that “recent past” might be equated to Einstein’s very-close parallel universe. There’s no GR involved since all Einstein did in his ER paper was evaporate GR out of existence and relevance at that level. If there’s a trailing universe, it is instead a quantum trace of our recent past, one that self-destructs as we move into the future.
The idea that this boundary point between now and the recent past can be stretched out and reinforced sufficiently to permit the formation and transfer of a statistically detectable entanglement into the recent past is… well, intriguing. It could lead to a better understanding of time.
One possible bummer: This might just be an enormously costly way of performing otherwise extremely cheap quantum erasure experiments. Sabrine Hossenfelder has an eloquent video on how such experiments also play with our concept of the past.
Finally, I’m pleased to say that I got through all that part about how I interpret their experiment as involving a quantum past that closely follows the present and then is annihilated by it without once mentioning The Langoliers… oops!
Curvature singularities won’t just “disappear” in GR by simply changing coordinates.
The ER paper is not a “modification” of GR. If you want an accurate picture of the causal structure of a classical ER bridge, you can take a look at a Penrose diagram of the vacuum Schwarzschild solution.
The wormhole that “connects the left and right regions” is time dependent in the interior ( not exactly “unstable” – that’s a term with a different meaning).
This is a consequence of the causal structure of the black hole spacetime: The r= constant hypersurfaces that are timelike outside the horizon become spacelike in the interior ( this is also what’s happening with the time translation “Killing vector”).
Mote intuitively: The tidal forces that , outside the horizon grow as you’re going closer, in the interior ( r<2Gm) , on the contrary, they grow with time. Roughly speaking, the "tidal forces" ( essentially the Weyl curvature) are inversely proportional to r^3, so an infalling object that crosses the horizon will inevitably be destroyed by tidal deformation.
That is the "singularity ": it's not a "point-like", compressed state of matter as it's usually ( and totally incorrectly) "depicted" by uninformed pop science videos( and the like..).
It is the final stage of a time dependent process, that's inextendible to the future. It will happen wherever one tries to go inside.
So, every possible worldline that crosses the horizon will end up inevitably destroyed completely. It's not possible to cross the ER wormhole for fundamental reasons. The " left and right asymptotically flat regions" will remain causally separated.
Another consequence of this "time dependence" is that the "proper length* of the wormhole is constantly growing ( linearly with time). The same happens with the ( generally covariant) "maximal volume" of the interior.
So, the interior of the black hole ( that has the spatial geometry of a 3- cylinder .i e. the product of a 2-sphere times the line) is constantly stretched along any proper radial direction (*) and squeezed perpendicularly to that .
(*) These "radial directions" have a spacelike character ( in the Penrose diagram is , roughly, left to right ) – not to be confused with the r coordinate.
Maybe, since you seem to know your GR, you could remind us if there are any assumptions made in general relativity coupled to matter that, if false, preclude either the existence or the creation of wormholes. I’m not expert enough to remember the rules and regulations about the stress tensor of the matter. The existence of the Einstein-Rosen bridge in the context of AdS/CFT was pretty clear to Susskind in the context where he was working, but I don’t recall the history of what was said about such bridges before he made this observation.
While my previous comment has to do with the vacuum solution, there are also other wormhole spacetimes ( as in K.Thorne and collaborators e.g. ) that allowed in classical GR , but they require violation of specific energy conditions ( ” negative energy”) and they’re also associated with the existence of Cauchy/ chronology horizons and their instability issues.
As for the ER=EPR conjecture, I need to take a closer and more careful look ( now that this is , more than ever, “en Vogue” ). For what I know so far, these “wormholes” , although they have their origin in the classical theory, have also “quantum properties” that I admit that they seem to me quite vague, at least in some aspects. But I suspect that this impression that I have has to do with my limited knowledge about the conjecture, so I need to learn more.
There are also deviations from the original ER=EPR in subsequent lectures etc. about the subject that I’m aware of.
One thing that I haven’t seen being addressed is what happens with these Cauchy horizons issues ( blueshift instability etc.). If someone knows some relevant papers, let me know.
Dimitris Papadimitriou (and Matt Strassler),
Thank you for the in-depth assessment of ER paper interpretations of GR.
The line quoted in my earlier December 2, 2022, 3:42 PM comment  that concerns me most is:
“… we must approximate the line element by a *slightly different one* which avoids the singularity g=0.”
Oddly, I don’t disagree with Einstein’s two-sheet concept. However, I reinterpret it as a noisy (GR is irrelevant) and overly smooth description of Higgs field dynamics, with weak-aware chirality fermions in the leading sheet and weak-unaware fermions in the trailing one. I switched to emergent spacetime many months ago, so the concept of curved space at this low level doesn’t “compute.” There’s not enough mass-energy resolution.
Professor, I have a great doubt about this search on Google’s quantum computer: As I am an engineer and programmer, also physicist, I ask you that, how they built the computer programs that simulates this Wormhole? What properties did they use? But mainly, how do they know about it operation, properties of an wormhole that never was discovered, that is, without knowing anything about it? For me to makes an engineering or physics programs, if there an error in an minimal fraction or a tiny fundamental properties, even if an undermost thing, my programs becomes unuseful. Thanks.
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