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Daniel Jafferis’ team has for the first time conducted an experiment based in current quantum computing to understand wormhole dynamics.

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Quantum computing simulation reveals possible wormhole-like dynamics

Complete understanding of many of the most fundamental forces at play in our world has proven slippery. A new experiment by a group of researchers, including Daniel Jafferis of Harvard’s Department of Physics and peers from Caltech, represents a small step in advancing our view of the relationship between gravity, which shapes the universe, and quantum mechanics, the theoretical framework governing the motion and interaction of subatomic particles.

For more than 100 years, the common description of gravity has stemmed from Albert Einstein’s theory of general relativity — that gravity relates to the curvature of space-time. In the last 25 years scientists have discovered there is an intimate connection between gravity and quantum mechanics. Among these connections are wormholes, also known as bridges or tunnels of space, which Einstein described in 1935 as passages through space-time that could connect two black holes.

Jafferis’ team has for the first time conducted an experiment based in current quantum computing to understand wormhole dynamics. “It is a quantum simulation of an extraordinarily tiny wormhole,” said Jafferis. “Before this, it was not clear with the devices we have now if one could do it at all.” The research was published in Nature .

Einstein’s general relativity theory described wormholes as two black holes whose interiors are joined, where something could jump in each side, meet in the middle, but neither could get out again — the proverbial trap in a black hole.

“It’s a beautiful idea from the 1930s that wormhole interiors are joined, but it has not been known if this concept is an operationally meaningful statement,” Jafferis said. “But now we know that wormhole configuration does indeed have a physical interpretation; it corresponds to the two separate black holes in a highly entangled space.”

In recent years, scientists have built physical devices like quantum computers to create simulations in which they can manipulate the entanglements of quantum states in a controlled way. Jafferis’ team wanted to see whether they could create a simplified model that would emulate the gravitational aspects of a wormhole. Could they make a quantum system where the pattern of space entanglement is structurally of the right sort so that it looks like sending something through a wormhole?

In lab experiments, the researchers introduced a connection between the two sides, making the wormhole traversable. Signals could be sent in one side and come through the other, maybe not quickly, but without getting stuck. In the quantum language this is called “quantum teleportation,” a way of sending quantum information using shared entanglement. “The information is not sent through the direct signal, but in a more subtle way that uses entanglement,” Jafferis added.

The team started with a qubit, the simplest kind of quantum space, in one area of their device. They released other qubits in another fixed entangled space within the computer for a total of nine qubits. The two spaces were then mixed using the gate operations of the quantum computer.

Next, they used data operations that interpreted the evolving system according to certain dynamics. The final step was looking at the qubit once it reached the other side of the computer. “We asked if it was the same as the one we sent in or if it looked different,” said Jafferis. “It was the simplest possible quantum circuit we could create to see if we could simulate wormhole dynamics.”

The team’s ultimate goal is to learn all the details about the gravitational description of quantum systems. “We know how that works through theoretical mathematics in limited cases, but we don’t know all the answers,” said Jafferis. “Using this very small quantum system, we see it as a first step toward making bigger ones where we can discover more.”

This research was funded the U.S. Department of Energy Office of Science.

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New theory unites Einstein's gravity with quantum mechanics

A radical theory that consistently unifies gravity and quantum mechanics while preserving Einstein's classical concept of spacetime is announced today in two papers published simultaneously by UCL (University College London) physicists.

Modern physics is founded upon two pillars: quantum theory on the one hand, which governs the smallest particles in the universe, and Einstein's theory of general relativity on the other, which explains gravity through the bending of spacetime. But these two theories are in contradiction with each other and a reconciliation has remained elusive for over a century.

The prevailing assumptionhas been that Einstein's theory of gravity must be modified, or "quantised," in order to fit within quantum theory. This is the approach of two leading candidates for a quantum theory of gravity, string theory and loop quantum gravity.

But a new theory, developed by Professor Jonathan Oppenheim (UCL Physics & Astronomy) and laid out in a new paper in Physical Review X (PRX), challenges that consensus and takes an alternative approach by suggesting that spacetime may be classical -- that is, not governed by quantum theory at all.

Instead of modifying spacetime, the theory -- dubbed a "postquantum theory of classical gravity" -- modifies quantum theory and predicts an intrinsic breakdown in predictability that is mediated by spacetime itself. This results in random and violent fluctuations in spacetime that are larger than envisaged under quantum theory, rendering the apparent weight of objects unpredictable if measured precisely enough.

A second paper, published simultaneously in Nature Communications and led by Professor Oppenheim's former PhD students,looks atsome of the consequences of the theory, and proposes an experiment to test it: to measure a mass very precisely to see if its weight appears to fluctuate over time.

For example, the International Bureau of Weights and Measures in France routinely weigh a 1kg mass which used to be the 1kg standard. If the fluctuations in measurements of this 1kg mass are smaller than required for mathematical consistency, the theory can be ruled out.

The outcome of the experiment, or other evidence emerging which would confirm the quantum vs classical nature of spacetime, is the subject of a 5000:1 odds bet between Professor Oppenheim and Professor Carlo Rovelli and Dr Geoff Penington -- leading proponents of quantum loop gravity and string theory respectively.

For the past five years, the UCL research group has been stress-testing the theory, and exploring its consequences.

Professor Oppenheim said: "Quantum theory and Einstein's theory of general relativity are mathematically incompatible with each other, so it's important to understand how this contradiction is resolved. Should spacetime be quantised, or should we modify quantum theory, or is it something else entirely? Now that we have a consistent fundamental theory in which spacetime does not get quantised, it's anybody's guess."

Co-author Zach Weller-Davies, who as a PhD student at UCL helped develop the experimental proposal and made key contributions to the theory itself, said: "This discovery challenges our understanding of the fundamental nature of gravity but also offers avenues to probe its potential quantum nature.

"We have shown that if spacetime doesn't have a quantum nature, then there must be random fluctuations in the curvature of spacetime which have a particular signature that can be verified experimentally.

"In both quantum gravity and classical gravity, spacetime must be undergoing violent and random fluctuations all around us, but on a scale which we haven't yet been able to detect. But if spacetime is classical, the fluctuations have to be larger than a certain scale, and this scale can be determined by another experiment where we test how long we can put a heavy atom in superposition* of being in two different locations."

Co-authors Dr Carlo Sparaciari and Dr Barbara Šoda, whose analytical and numerical calculations helped guide the project, expressed hope that these experiments could determine whether the pursuit of a quantum theory of gravity is the right approach.

Dr Šoda (formerly UCL Physics & Astronomy, now at the Perimeter Institute of Theoretical Physics, Canada) said: "Because gravity is made manifest through the bending of space and time, we can think of the question in terms of whether the rate at which time flows has a quantum nature, or classical nature.

"And testing this is almost as simple as testing whether the weight of a mass is constant, or appears to fluctuate in a particular way."

Dr Sparaciari (UCL Physics & Astronomy) said: "While the experimental concept is simple, the weighing of the object needs to be carried out with extreme precision.

"But what I find exciting is that starting from very general assumptions, we can prove a clear relationship between two measurable quantities -- the scale of the spacetime fluctuations, and how long objects like atoms or apples can be put in quantum superposition of two different locations. We can then determine these two quantities experimentally."

Weller-Davies added: "A delicate interplay must exist if quantum particles such as atoms are able to bend classical spacetime. There must be a fundamental trade-off between the wave nature of atoms, and how large the random fluctuations in spacetime need to be."

The proposal to test whether spacetime is classical by looking for random fluctuations in mass is complementary to another experimental proposal which aims to verify the quantum nature of spacetime by looking for something called "gravitationally mediated entanglement."

Professor Sougato Bose (UCL Physics & Astronomy), who was not involved with the announcement today, but was among those to first propose the entanglement experiment, said: "Experiments to test the nature of spacetime will take a large-scale effort, but they're of huge importance from the perspective of understanding the fundamental laws of nature. I believe these experiments are within reach -- these things are difficult to predict, but perhaps we'll know the answer within the next 20 years."

The postquantum theory has implications beyond gravity. The infamous and problematic "measurement postulate" of quantum theory is not needed, since quantum superpositions necessarily localise through their interaction with classical spacetime.

The theory was motivated by Professor Oppenheim's attempt to resolve the black hole information problem. According to standard quantum theory, an object going into a black hole should be radiated back out in some way as information cannot be destroyed, but this violates general relativity, which says you can never know about objects that cross the black hole's event horizon. The new theory allows for information to be destroyed, due to a fundamental breakdown in predictability.

* Background information

Quantum mechanics background : All the matter in the universe obeys the laws of quantum theory, but we only really observe quantum behaviour at the scale of atoms and molecules. Quantum theory tells us that particles obey Heisenberg's uncertainty principle, and we can never know their position or velocity at the same time. In fact, they don't even have a definite position or velocity until we measure them. Particles like electrons can behave more like waves and act almost as if they can be in many places at once (more precisely, physicists describe particles as being in a "superposition" of different locations).

Quantum theory governs everything from semiconductors which are ubiquitous in computer chips, to lasers, to superconductivity to radioactive decay. In contrast, we say that a system behaves classically if it has definite underlying properties. A cat appears to behave classically -- it is either dead or alive, not both, nor in a superposition of being dead and alive. Why do cats behave classically, and small particles quantumly? We don't know, but the postquantum theory doesn't require the measurement postulate, because the classicality of spacetime infects quantum systems and causes them to localise.

Gravity background: Newton's theory of gravity, gave way to Einstein's theory of general relativity (GR), which holds that gravity is not a force in the usual sense. Instead, heavy objects such as the sun, bend the fabric of spacetime in such a way that causes the earth to revolve around it. Spacetime is just a mathematical object consisting of the three dimensions of space, and time considered as a fourth dimension. General relativity predicted the formation of black holes and the big bang. It holds that time flows at different rates at different points in space, and the GPS in your smartphone needs to account for this in order to properly determine your location.

Historical context: The framework presented by Oppenheim in PRX, and in a companion paper with Sparaciari, Šoda and Weller-Davies, derives the most general consistent form of dynamics in which a quantum system interacts with a classical system. It then applies this framework to the case of general relativity coupled to quantum fields theory. It builds on earlier work and a community of physicists. An experiment to test the quantum nature of gravity via gravitationally mediated entanglement was proposed by Bose et. al. and by C. Marletto and V. Vadral. Two examples of consistent classical-quantum dynamics were discovered in the 90's by Ph. Blanchard and A. Jadzyk, and by Lajos Diosi, and again by David Poulin around 2017. From a different perspective, in 2014 a model of Newtonian gravity coupled to quantum systems via a "measurement-and-feedback" approach, was presented by Diosi and Antoinne Tilloy in 2016, and by D Kafri, J. Taylor, and G. Milburn, in 2014. The idea that gravity might be somehow related to the collapse of the wavefunction, dates back to F. Karolyhazy (1966), L. Diosi (1987) and R. Penrose (1996). That classical-quantum couplings might explain localistation of the wavefunction has been suggested by others including M. Hall and M. Reginatto, Diosi and Tilloy, and David Poulin. The idea that spacetime might be classical dates back to I. Sato (1950), and C. Moller (1962), but no consistent theory was found until now.

• Black Holes
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• Albert Einstein
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• Holographic Universe
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Materials provided by University College London . Note: Content may be edited for style and length.

Journal Reference :

• Jonathan Oppenheim, Carlo Sparaciari, Barbara Šoda, Zachary Weller-Davies. Gravitationally induced decoherence vs space-time diffusion: testing the quantum nature of gravity . Nature Communications , 2023; 14 (1) DOI: 10.1038/s41467-023-43348-2

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Strange & offbeat.

What is emergent gravity, and will it rewrite physics?

The idea is still new and requires a lot of assumptions in its calculations to make it work. Over the years, experimental results have been mixed.

In 2009, theoretical physicist Erik Verlinde proposed a radical reformulation of gravity. In his theory, gravity is not a fundamental force but rather a manifestation of deeper hidden processes. But in the 15 years since then, there hasn't been much experimental support for the idea. So where do we go next?

Emergence is common throughout physics. The property of temperature, for example, isn't an intrinsic property of gases. Instead, it's the emergent result of countless microscopic collisions. We have the tools to match those microscopic collisions to temperature; indeed, there is an entire branch of physics, known as statistical mechanics, that makes these connections known.

In other areas, the connections between microscopic behaviors and emergent properties aren't so clear. For example, while we understand the simple mechanisms behind superconductivity, we do not know how microscopic interactions lead to the emergence of high-temperature superconductors.

Related: Why Einstein must be wrong: In search of the theory of gravity

Verlinde's theory is based on what Stephen Hawking and Jacob Bekenstein observed in the 1970s: Many properties of black holes can be expressed in terms of the laws of thermodynamics. However, the laws of thermodynamics are themselves emergent from microscopic processes. To Verlinde, this was more than a mere coincidence and indicated that what we perceive as gravity may be emerging from some deeper physical process.

In 2009, he published the first version of his theory . Crucially, we do not need to know what those deeper processes are, since we already have the tool kit — statistical mechanics — for describing emergent properties. So Verlinde applied these techniques to gravity and arrived at an alternate formulation of gravity. And because gravity is also tied to our concepts of motion, inertia, space and time, this means our entire universe is also emergent from those same deeper processes. 

At first, not much came of this; rewriting a known law of physics, while interesting, doesn't necessarily provide deeper insights. But in 2016, Verlinde expanded his theory by discovering that a universe containing dark energy naturally leads to a new emergent property of space, thus allowing it to push inward on itself in regions of low density.

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This discovery led to a flurry of excitement, as it provided an alternative explanation for dark matter . Currently, astronomers believe that dark matter is a mysterious, invisible substance that makes up the bulk of all the mass of every galaxy . While that hypothesis has been able to explain a vast wealth of observations, from the rotation rates of stars within galaxies to the evolution of the largest structures in the cosmos, we have yet to identify the mysterious particle.

In Verlinde's picture of emergent gravity, as soon as you enter low-density regions — basically, anything outside the solar system — gravity behaves differently than we would expect from Einstein's theory of general relativity . At large scales, there is a natural inward pull to space itself, which forces matter to clump up more tightly than it otherwise would.

This idea was exciting because it allowed astronomers to find a way to test this new theory. Observers could take this new theory of gravity and put it in models of galaxy structure and evolution to find differences between it and models of dark matter.

Over the years, however, the experimental results have been mixed. Some early tests favored emergent gravity over dark matter when it came to the rotation rates of stars. But more recent observations haven't found an advantage. And dark matter can also explain much more than galaxy rotation rates; tests within galaxy clusters have found emergent gravity coming up short.

— Is the origin of dark matter gravity itself?

— Why is gravity so weak? The answer may lie in the very nature of space-time

— 'Quantum gravity' could help unite quantum mechanics with general relativity at last  

This isn't the end of emergent gravity. The idea is still new and requires a lot of assumptions in its calculations to make it work. Without a fully realized theory, it's hard to tell if the predictions it makes for the behavior of galaxies and clusters accurately represent what emergent gravity would tell us. And astronomers are still trying to develop more stringent tests, like using data from the cosmic microwave background , to really put the theory through its paces.

Emergent gravity remains an intriguing idea. If it's correct, we would have to radically reshape our understanding of the natural world and see gravity and motion — and even more fundamental concepts, like time and space — through a lens of emergence from deeper, more complicated interactions. But for right now, it remains simply an intriguing idea. Only time and extensive observational testing will tell us if we're on the right track.

Join our Space Forums to keep talking space on the latest missions, night sky and more! And if you have a news tip, correction or comment, let us know at: [email protected].

Paul M. Sutter is an astrophysicist at SUNY Stony Brook and the Flatiron Institute in New York City. Paul received his PhD in Physics from the University of Illinois at Urbana-Champaign in 2011, and spent three years at the Paris Institute of Astrophysics, followed by a research fellowship in Trieste, Italy, His research focuses on many diverse topics, from the emptiest regions of the universe to the earliest moments of the Big Bang to the hunt for the first stars. As an "Agent to the Stars," Paul has passionately engaged the public in science outreach for several years. He is the host of the popular "Ask a Spaceman!" podcast, author of "Your Place in the Universe" and "How to Die in Space" and he frequently appears on TV — including on The Weather Channel, for which he serves as Official Space Specialist.

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• Rod Mack The ideas of Theory Z0 using the density of energy to drive the acceleration seen as gravity have applications to this view. The Z0 Theory is a new idea about gravity, simplifying the complex ideas developed over the last century. Instead of thinking of gravity as a force pulling things together, it suggests a connection to acceleration. This means gravity is linked to electromagnetic energy, not mass, as traditionally believed. At its core, Z0 challenges traditional notions by proposing that gravity is not a force of attraction but rather an 'equivalence' related to acceleration. This unique perspective links gravity to electromagnetic energy, departing from the conventional association with mass, as famously expressed in Einstein's E=mc². Maxwell's equations play a crucial role. The speed of light (c) and the admittance of free space (Y0) are interconnected, revealing that alterations in these parameters impact the rate of energy flow. Changes in the speed of light, representing energy, are then identified as the acceleration attributed to gravity. The gravitational constant in this framework denoted as Gv, where Gv = -Δx/Δ√ε0μ0, is intricately tied to the rate of change in the speed of energy. This theory not only offers a mechanism for gravity compatible with existing mathematical frameworks but also provides explanations for phenomena like black holes, and cosmic microwave background structures, and even postulates the existence of impedance bubbles as barrier structures. Entropy, accounting for energy changes such as redshift and signal delays, becomes a key element in this quantum view of gravity based on energy. Z0 introduces a concept of 'quantum gravity,' emphasizing a connection between the complex admittance of energy into space. Z0 presents a compelling framework where gravity is intricately tied to energy dynamics. This theory, akin to relativity, introduces the idea of a constant time and a variable speed of energy, explaining force as 'equivalent' gravity due to slight changes in energy density. It's a paradigm shift that seeks simplicity in explaining the profound mysteries of our universe. Reply
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• Research update

‘Cavendish-like’ experiment could reveal gravity’s quantum nature

Mathematical physicists in the Netherlands and Germany have proposed a new “Cavendish-like” gravitation experiment that could offer an alternative means of determining whether gravity is a classical or quantum phenomenon. If built, the experiment might bring us closer to understanding whether the theory of gravity can be reconciled with quantum-mechanical descriptions of the other fundamental forces – a long sought-after goal in physics.

Gravity is one of the four known fundamental forces in nature. It is different from the others – the electromagnetic force and the weak and strong nuclear forces – because it describes a curvature in space-time rather than interactions between objects. This may be why we still do not understand whether it is classical (as Albert Einstein described it in his general theory of relativity) or governed by the laws of quantum mechanics and therefore unable to be fully described by a local classical field.

Many experiments that aim to resolve this long-standing mystery rely on creating quantum entanglement between two macroscopic objects placed a certain distance from each other. Entanglement is a phenomenon whereby the information contained in an ensemble of particles is encoded in correlations among them, and it is an essential feature of quantum mechanics – one that clearly distinguishes the quantum from the classical world.

The hypothesis, therefore, is that if massive, distant objects (known as delocalized states) can be entangled, then gravity must be quantum.

Revealing gravity’s quantum nature without generating entanglement

The problem is that it is extremely difficult to make large objects behave as quantum particles. In fact, the bigger they get, the more likely they are to lose their quantum-ness and resort to behaving like classical objects.

Ludovico Lami of the University of Amsterdam , together with Martin Plenio and Julen Pedernales of the University of Ulm , have now thought up a new experiment that would reveal gravity’s quantum nature without having to generate entanglement. Their proposal – which is so far only a thought experiment – involves studying the correlations between two torsion pendula placed close to each other as they rotate back and forth with respect to each other, acting as massive harmonic oscillators (see figure).

This set-up is very similar to the one that Henry Cavendish employed in 1797 to measure the strength of the gravitational force, but its purpose is different. The idea, the team say, would be to uncover correlations generated by the whole gravity-driven dynamical process and show that they are not reproducible if one assumes the type of dynamics implied by a local, classical version of gravity. “In quantum information, we call this type of dynamics an ‘LOCC’ (from ‘local operations and classical communication’),” Lami says.

In their work, Lami continues, he and his colleagues “design and prove mathematically some ‘LOCC inequalities’ whose violation, if certified by an experiment, can falsify all LOCC models. It turns out that you can use them to rule out LOCC models also in cases where no entanglement is physically generated.”

An alternative pathway

The researchers, who detail their study in Physical Review X , say they decided to look into this problem because traditional experiments have well-known bottlenecks that are difficult to overcome. Most notably, they require the preparation of large delocalized states.

The new experiment, Lami says, is an alternative way of realizing experiments that can definitively indicate whether gravity is ultimately fully classical, as Einstein taught us, or somehow non-classical – and hence most likely quantum. “While we don’t claim that our method is completely and utterly better than the others, it is quite different and, depending on the experimental platform, may prove easier to practically set up,” he tells Physics World .

Getting closer to measuring quantum gravity

Lami, Plenio and Pedernales are now working to bring their analyses closer to real-world experiments by taking into account other interactions besides gravity. While doing so will complicate the picture and make their analyses more involved, they recognize that it will eventually be necessary for building a “bulletproof” experiment.

Plenio adds that the approach they are taking could also reveal other finer details about the nature of gravity. “In our work we describe how to decide whether gravity can be mimicked by local operations and classical communications or not,” he says. “There might be other models, however – for example, where gravity follows dynamics that do not obey LOCC, but still do not have to create entanglement either. This type of dynamics is called ‘separability preserving’. In principle we can also solve our equations for these.”

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Quantum Gravity Gets a New Test

Gravity might be the most familiar of the four fundamental forces, but it is by far the weakest. This feebleness has prevented researchers from exploring the intrinsic properties of gravity and, in particular, from determining whether the force is classical or quantum in nature. Such a determination is long sought after because it could help physicists reconcile the theory of gravity with the quantum descriptions of the other fundamental forces. That goal might now be one step closer thanks to a radically new experimental strategy devised by Ludovico Lami at the University of Amsterdam and his colleagues [ 1 ].

Previously proposed experiments to test the “quantumness” of gravity have focused on entanglement—a purely quantum effect in which the properties of objects are correlated in a nonclassical way. In those experiments, two widely separated, heavy objects are placed in highly delocalized quantum states, meaning that their wave functions are spread out over a large volume of space. Theorists predict that, if gravity is intrinsically quantum, the mutual gravitational attraction between the two objects could cause them to become entangled (see Synopsis: A Test of Gravity’s Quantum Side ). “The main problem with these previous proposals is that highly delocalized states of heavy objects are very challenging to create,” says Lami, the lead researcher of the new work. Moreover, entanglement is incredibly fragile and can be difficult to detect.

The strategy suggested by Lami and his colleagues avoids these issues because it does not require the production of highly delocalized quantum states or the generation and detection of entanglement. As a concrete example of their approach, the researchers consider an experiment involving two torsion pendulums—wire-suspended rigid bodies that rotate back and forth as their wires twist. These bodies are shaped like dumbbells, with each end weighing less than a gram and constituting one half of an optical cavity—the other half being a fixed mirror. As the pendulums oscillate, they change the size and therefore the resonant wavelength of each cavity. This change can be detected by shining laser light into the cavities and then measuring the intensity of the resulting interference pattern.

The two pendulums are coupled through their mutual gravitational attraction by placing them near each other with their equilibrium orientations in parallel. To ensure that gravity is the dominant force between the pendulums, a shield is positioned in the middle to suppress any potential electromagnetic and optical interactions. Additionally, the distance separating the pendulums is carefully chosen so that their gravitational attraction is always much stronger than the Casimir force between them and the shield.

Using their coupling to the optical cavities, the pendulums are first driven to their ground states, in which they are at rest, and then placed in randomly selected coherent states, in which they oscillate with a well-defined amplitude. Next, they are left to evolve under gravity for a specific time. The expected states of the pendulums at the end of that time are computed, assuming the gravitational interaction is quantum in nature. A tiny nudge that would put those computed states back into the ground states is then given to the pendulums. Finally, after applying that nudge, the pendulums are checked to see if they are indeed in their ground states. This procedure is repeated many times, and the probability of finding the pendulums in their ground states following these steps is determined. If this probability exceeds an upper bound calculated for classical gravity, it indicates that gravity is not classical.

To compute that upper bound, Lami says that his team “brought in and honed some heavy mathematical machinery from quantum information theory” and, in particular, “used tools from the theory of entanglement manipulation.” A key assumption behind this calculation—that also underpins the previous, entanglement-based protocols—is that, for classical gravity, the gravitational interactions between quantum objects can be described by a sequence of local quantum operations assisted by classical communication. However, that assumption is a subject of hot debate. Another potential issue with the new proposal is that the experiment requires long coherence times, torsion pendulums that lose little energy as they oscillate, and an ultracold environment. Nevertheless, the researchers hope their work will open a new experimental avenue in the investigation of the interplay between gravity and quantum physics.

Andrea Mari and David Vitali, two quantum physicists at the University of Camerino, Italy, think that the suggested approach is a promising alternative to the more conventional, entanglement-based protocols and is, in principle, feasible with existing or near-future technology. They stress that, ultimately, experimentalists will decide which scheme is the best and the most convenient.

–Ryan Wilkinson

Ryan Wilkinson is a Corresponding Editor for  Physics Magazine based in Durham, UK.

• L. Lami et al. , “Testing the quantumness of gravity without entanglement,” Phys. Rev. X 14 , 021022 (2024) .

Testing the Quantumness of Gravity without Entanglement

Ludovico Lami, Julen S. Pedernales, and Martin B. Plenio

Phys. Rev. X 14 , 021022 (2024)

Published May 1, 2024

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Quantum physics and Einstein’s theory of general relativity are the two solid pillars that underlie much of modern physics. Understanding how these two well-established theories are related remains a central open question in theoretical physics.  Over the last several decades, efforts in this direction have led to a broad range of new physical ideas and mathematical tools.  In recent years, string theory and quantum field theory have converged in the context of holography, which connects quantum gravity in certain space-times with corresponding (conformal) field theories on a lower-dimensional space-time. These developments and connections have deepened our understanding not only of quantum gravity, cosmology, and particle physics, but also of intermediate scale physics, such as condensed matter systems, the quark-gluon plasma, and disordered systems.  String theory has also led to new insights to problems in many areas of mathematics.

The interface of quantum physics and gravity is currently leading to exciting new areas of progress, and is expected to remain vibrant in the coming decade.  Researchers in the Center for Theoretical Physics (CTP) have been at the forefront of many of the developments in these directions.  CTP faculty members work on string theory foundations, the range of solutions of the theory, general relativity and quantum cosmology, problems relating quantum physics to black holes, and the application of holographic methods to strongly coupled field theories.  The group in the CTP has close connections to condensed matter physicists, astrophysicists, and mathematicians both at MIT and elsewhere.

In recent years a set of new developments has begun to draw unexpected connections between a number of problems relating aspects of gravity, black holes, quantum information, and condensed matter systems. It is becoming clear that quantum entanglement, quantum error correction, and computational complexity play a fundamental role in the emergence of spacetime geometry through holographic duality.  Moreover these tools have led to substantial progress on the famous black hole information problem, giving new avenues for searching for a resolution of the tension between the physics of black holes and quantum mechanics.  CTP faculty members Netta Engelhardt and Daniel Harlow have been at the vanguard of these developments, which also tie into the research activity of several other CTP faculty members, including Aram Harrow , whose primary research focus is on quantum information, and Hong Liu , whose research connects black holes and quantum many-body dynamics.

Holographic dualities give both a new perspective into quantum gravitational phenomena as encoded in quantum field theory, and a way to explore aspects of strongly coupled field theories using the gravitational dual. CTP faculty have played a pioneering role in several applications of holographic duality. Hong Liu and Krishna Rajagopal are at the forefront of efforts that use holography to find new insights into the physics of the quark-gluon plasma. Liu was among the first to point out possible connections between black hole physics and the strange metal phase of high temperature superconductors, and in recent years has been combining insights from effective field theories, holography, and condensed matter physics to address various issues concerning far-from-equilibrium systems including superfluid turbulence, entanglement growth, quantum chaos, thermalization, and a complete formulation of fluctuating hydrodynamics. Gravitational effective field theories play a key role in the interpretation of gravitational wave observations. Mikhail Ivanov works at the intersection of these fields with the aim of testing strong field gravity at a new precision frontier.

Even though we understand string theory better than we did in decades past, there is still no clear fundamental description of the theory that works in all situations, and the set of four-dimensional solutions, or string vacua, is still poorly understood.  The work of Washington Taylor and Barton Zwiebach combines physical understanding with modern mathematical methods to address these questions, and has led to new insights into how observed physics fits into the framework of string theory as well as the development of new mathematical results and ideas. Alan Guth ‘s foundational work on inflationary cosmology has led him to focus on basic questions about the physics of the multiverse that arises naturally in the context of the many string theory vacua, and which provides the only current natural explanation for the observed small but positive cosmological constant.

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Astrophysicists present first evidence of gravitational wave ‘background’.

Artist’s interpretation of an array of pulsars being affected by gravitational ripples produced by a supermassive black hole binary in a distant galaxy. (Credit: Aurore Simonnet for the NANOGrav Collaboration)

Researchers have found the first direct evidence of a “background” of gravitational waves in the universe — a sign that gravitational waves from slowly merging pairs of supermassive black holes, or possibly from the early universe, can be detected from Earth in a background field of low-frequency energy.

The discovery, made by the North American Nanohertz Observatory for Gravitational Waves (NANOGrav), helps confirm the accuracy of standard models of galaxy formation and black hole growth.

NANOGrav scientists, including Yale’s Chiara Mingarelli, published the discovery in a quintet of new studies June 29 in The Astrophysical Journal Letters.

“ These are big questions we’re trying to answer about how the universe evolved,” said Mingarelli, an assistant professor of physics in Yale’s Faculty of Arts and Sciences. “I’ve been interested in helping to find these answers since I was a kid. It’s awe-inspiring.”

Gravitational waves are ripples in the fabric of space-time, which can be caused by the merging of two black holes. Albert Einstein predicted the existence of gravitational waves in 1915 as part of his general theory of relativity. A century later, scientists at the Laser Interferometer Gravitational-Wave Observatory (LIGO) announced the first observation of gravitational waves.

LIGO scientists, however, were only able to detect waves from the higher frequency end of the gravitational wave spectrum. In order to look for waves at the lower end of the gravitational wave spectrum — such as more distant and powerful waves from supermassive black hole collisions — a different detection method was necessary.

The NANOGrav project, which began in 2007 and includes more than 170 researchers from more than 70 institutions, spearheaded a detection method centered around pulsars.

Pulsars are rapidly rotating neutron stars — the collapsed cores of massive stars that have exploded. Pulsars send out radio emissions that can be timed to the millisecond, making each one something of an ultra-accurate, cosmic clock.

With help from several ground-based telescopes in the United States and Canada, NANOGrav created a network of precisely timed pulsars, which allows NANOGrav researchers to measure and track previously undetected gravitational waves at low frequencies as they make their way to Earth. Gravitational waves, as they wash over the pulsars, alter the distances between the pulsars in the array and the Earth — meaning the normally-stable pulsar signals reach Earth early and then late.

Gravitational waves leave an indelible but challenging-to-detect signal within pulsar timing signals.

The five new studies elucidate the detection of the gravitational wave background field, the data that NANOGrav collected, a characterization of the data, tests of fundamental physics, and an astrophysical interpretation of the data in terms of supermassive black hole physics, respectively.

The findings “open a tantalizing new window — the gravitational wave window — and offer a first glimpse into the population of supermassive black holes,” said Priyamvada Natarajan, the Joseph S. and Sophia S. Fruton Professor of Astronomy and professor of physics in Yale’s Faculty of Arts and Sciences and chair of the Department of Astronomy, who is a co-author of the detection study.

“ This is really exciting for those of us who have been building models of the growth and evolution of black hole populations that involve mergers as one key mode by which black holes are expected to grow,” added Natarajan, who is a member of the NANOGrav collaboration.

Mingarelli noted that the findings confirm standard models of how the universe works, particularly in terms of supermassive black holes.

“ Up until now all we could see of supermassive black holes have been snapshots in time,” she said. “Directly seeing merging supermassive black holes is almost impossible — their tight orbits mean that they are too close together to see individually, since they are so far away. Now, for the first time, we have evidence that they merge. We don’t need to see them, we can hear them.”

Mingarelli joined the NANOGrav project in 2014 and was previously a member of the European Pulsar Timing Array. Her work has involved simulating gravitational wave backgrounds and interpreting NANOGrav data to understand how gas and stars affect supermassive black hole mergers, in terms of their wave signals. She has also created tools to create maps of the gravitational wave sky, to see where there might be higher concentrations of gravitational wave signals.

Next on NANOGrav’s research agenda, she said, will be to determine whether there are nearby merging supermassive black hole systems that can stand out above the gravitational wave background, and other events in the early universe creating gravitational waves, in addition to black holes.

NANOGrav receives support from the National Science Foundation, the Gordon and Betty Moore Foundation, a National Sciences and Engineering Research Council of Canada (NSERC) Discovery Grant, and the Canadian Institute for Advanced Research.

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In a major discovery, scientists say space-time churns like a choppy sea

The mind-bending finding suggests that everything around us is constantly being roiled by low-frequency gravitational waves

The very fabric of the cosmos is constantly being roiled and rumpled all around us, according to multiple international teams of scientists that have independently found compelling evidence for long-theorized space-time waves.

The claim that telescopes across the planet have seen signs of a “gravitational wave background” has sent a thrill through the astrophysics community, which has been buzzing for days in anticipation of the papers that were unveiled late Wednesday. The discovery seems to affirm an astounding implication of Albert Einstein’s general theory of relativity that until now has been far too subtle to detect.

In Einstein’s reimagined universe , space is not serenely empty, and time does not march smoothly forward. Instead, the powerful gravitational interactions of massive objects — including supermassive black holes — regularly ripple the fabric of space and time. The picture that emerges is a universe that looks like a choppy sea, churned by violent events that happened over the course of the past 13 billion-plus years.

The gravitational wave background, as described by the astrophysicists, does not put any torque on everyday human existence. There is not a weight-loss discovery in here somewhere. A burble of gravitational waves cannot explain why some days you feel out of sorts. But it does offer potential insight into the physical reality we all inhabit.

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“What we measure is the Earth kind of moving in this sea. It’s bobbing around — and it’s not just bobbing up and down, its bobbing in all directions,” said Michael Lam, an astrophysicist at the SETI Institute and a member of the North American Nanohertz Observatory for Gravitational Waves (NANOGrav), a team largely based in North America. The NANOGrav team released the findings in five papers that were published Wednesday in the Astrophysical Journal Letters.

Teams in Europe, India, Australia and China also observed the phenomenon and planned to post their studies at the same time. The simultaneous release of papers from far-flung and competitive teams using similar methodology came only after some scientific diplomacy that ensured no group tried to scoop the rest of the astrophysical community.

“We’ve been on a mission for the last 15 years to find a low-pitch hum of gravitational waves resounding throughout the universe and washing through our galaxy to warp space-time in a measurable way,” NANOGrav chair Stephen Taylor of Vanderbilt University said at a news briefing Tuesday.

“We’re very happy to announce that our hard work has paid off.”

Discovery from dead stars

The feat builds on previous discoveries of things in the universe that are invisible to the naked eye — pulsars . A pulsar is a type of neutron star, the ultradense remnant of a dead star. It is called a pulsar because it spins rapidly, hundreds of revolutions per second, and emits radio waves in a steady pulse. Pulsars were discovered only in the 1960s, not long after the invention of large radio telescopes.

NANOGrav gathered data from 68 pulsars using the Green Bank Telescope in rural West Virginia, the 27 telescopes of the Karl G. Jansky Very Large Array in New Mexico, and the now-defunct Arecibo Observatory in Puerto Rico.

The pulses from these bizarre objects reach telescopes on Earth at such predictable frequencies that they serve as cosmic timepieces, nearly as accurate as today’s most advanced atomic clocks, said Chiara Mingarelli, an astrophysicist at Yale and a member of the NANOGrav team.

Theorists believed that low-frequency gravitational waves could throw off the arrival of pulsar signals. Such low-frequency ripples can have crests separated by years, so the search for subtle swells in the sea of space-time required patience. The deviation in the pulsar data is so slight that it took 15 years of observations to come up with solid evidence of these gravitational waves, Mingarelli said.

The NANOGrav team had previously published reports with preliminary suggestions that the background exists, but had said more time was necessary to boost confidence that the signal was real and not just noise.

“Even devising the experiment was a huge mental leap,” Mingarelli said.

The existence of gravitational waves is not in dispute. In 2016, scientists announced that their ambitious four-decade experiment called LIGO , for Laser Interferometer Gravitational-Wave Observatory, had detected waves from the merger of two black holes. But the newly announced waves are not one-shot wonders, and theorists are noodling the many potential explanations for why the cosmic sea ripples in such a fashion.

Supermassive black holes are the favored explanation.

Most galaxies are home to supermassive black holes in or near their central region. These black holes certainly deserve the “supermassive” label: They typically have the equivalent mass of millions or even billions of suns. By contrast, “stellar mass” black holes are pipsqueaks, with masses akin to 10 or 20 or 30 suns.

Galaxies rarely collide, but the universe is vast, there are many billions of galaxies, and they have had plenty of time to drift into one another. During a galactic meetup, theorists say, the supermassive black holes at the cores of the two galaxies first will do a gravitational dance. They can orbit each other for millions of years, Lam said. This pairing is known as a supermassive black hole binary.

The swirling dance disturbs the fabric of space-time sufficiently to generate very low-frequency gravitational waves that travel across the universe at the speed of light, scientists believe. Over time, energy leaks from the dance party, as it were, and the supermassive black holes ease closer together, their orbital period shortening to just a few decades. At that point, the wavelengths begin to reach the frequencies detectable by NANOGrav, Lam said.

“So at this point in our measurements, we cannot definitively state what sources are producing the gravitational wave background signal,” NANOGrav team member Luke Kelley, an astrophysicist at the University of California at Berkeley, said at the Tuesday news briefing. However, he said, the data is a compelling match for theoretical predictions.

Theorists are “having fun” coming up with other possible sources for the low-frequency signal, he added. But “if it’s not coming from supermassive black hole binaries, we would need to come up with some explanation of where those supermassive black holes are hiding, and why we’re not seeing their gravitational waves.”

A new astronomical era

No matter the signal’s source, the announcement of a gravitational wave background represents a milestone in the embryonic field of gravitational wave astronomy.

Just as some astronomers use different wavelengths of light to probe the cosmos, they can now look for different types of gravitational waves. The low-frequency waves announced Wednesday wouldn’t be detectable by LIGO, and the opposite is also true: NANOGrav and similar efforts using pulsars could not detect the kind of high-frequency waves from the unimaginably violent stellar-mass black hole mergers seen by LIGO.

Lam said the next goal is to pair specific gravitational waves with potential supermassive black hole binaries detected through more traditional forms of astronomy. In other words, rather than just saying we’re picking up signs of lots of waves, the astronomers could say this particular wave right here came from that place over there.

The announcement carries an echo of another milestone in the history of cosmology. In 1965, two physicists at Bell Labs reported that they had detected the signal of something previously theorized: the cosmic microwave background radiation. That residual glow offered landmark evidence that the universe was created by the big bang .

Maura McLaughlin, co-director of the NANOGrav Physics Frontiers Center, said at the Tuesday briefing that the next step will be for the international teams to combine their independent data into one “uber data set” that should show an even clearer signal of the gravitational wave background — and maybe even the first detection of a supermassive black hole binary.

“We’re opening up a completely new window … on the gravitational wave universe,” she said.

The work, she said, should offer deeper insight into the ways galaxies form and evolve. It might even reveal exotic new physics that would alter our fundamental understanding of the cosmos: “It should be really, really exciting.”

Gravity is the fundamental force best known for keeping things grounded — literally! Live Science guides you through the history of gravity's discovery, keeps you in the loop about new weighty research and answers all your gravity-related questions.

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Whether it’s weird theories of gravity , lost sketches revealing how Da Vinci understood gravity centuries before Einstein , how the tiniest ever gravitational force was measured, or what our universe would look like if gravity just didn't exist , our expert writers and editors keep you down to Earth with the latest gravity news, features and articles 

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Articles on Gravity

Displaying 1 - 20 of 102 articles.

Heavy water: how melting ice sheets and pumped groundwater can lower local sea levels – and boost them elsewhere

Rebecca McGirr , Australian National University ; Anthony Purcell , Australian National University ; Herbert McQueen , Australian National University , and Paul Tregoning

Is dark matter’s main rival theory dead? There’s bad news from the Cassini spacecraft and other recent tests

Indranil Banik , University of St Andrews and Harry Desmond , University of Portsmouth

Earth, the Sun and a bike wheel: why your high-school textbook was wrong about the shape of Earth’s orbit

Stephen Hughes , The University of Queensland

A solar eclipse and a black hole can both bend light

Martin Connors , Athabasca University

How do airplanes fly? An aerospace engineer explains the physics of flight

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Bringing classical physics into the modern world with Galileo’s Leaning Tower of Pisa experiment

Larry M. Silverberg , North Carolina State University

Do we live in a giant void? It could solve the puzzle of the universe’s expansion

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Gravitational distortion of time helps tell modified gravity apart from a dark force

Levon Pogosian , Simon Fraser University and Camille Bonvin , Université de Genève

Antimatter: we cracked how gravity affects it – here’s what it means for our understanding of the universe

William Bertsche , University of Manchester

Why Einstein must be wrong: In search of the theory of gravity

Valerio Faraoni , Bishop's University and Andrea Giusti , Swiss Federal Institute of Technology Zurich

Spending time in space can harm the human body − but scientists are working to mitigate these risks before sending people to Mars

Rachael Seidler , University of Florida

Curious Kids: how do black holes pull in light?

Sara Webb , Swinburne University of Technology

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Robert Nichol , University of Surrey and Tessa Baker , Queen Mary University of London

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New Discovery Indicates an Alternative Gravity Theory

By University of Bonn October 16, 2022

The dwarf galaxy NGC1427A flies through the Fornax galaxy cluster and undergoes disturbances that would not be possible if this galaxy were surrounded by a heavy and extended dark matter halo, as required by standard cosmology. Credit: ESO

Disturbances in the dwarf galaxies of one of Earth’s closest galaxy clusters point to a different gravity theory.

Dwarf galaxies are small, faint galaxies that are often found in or close to bigger galaxies or galaxy clusters. As a result, they could be impacted by their larger companions’ gravitational effects.

“We introduce an innovative way of testing the standard model based on how much dwarf galaxies are disturbed by gravitational tides’ from nearby larger galaxies,” said Elena Asencio, a Ph.D. student at the University of Bonn and the lead author of the story.

Tides occur when gravity from one body pulls on various areas of another body differently. These are comparable to tides on Earth, which form when the moon exerts a stronger pull on the side of the Earth that faces the moon.

The Fornax Cluster is home to a rich population of dwarf galaxies. Recent observations suggest that several of these dwarfs seem distorted as if the cluster environment had perturbed them. “Such perturbations in the Fornax dwarfs are not expected according to the Standard Model,” said Pavel Kroupa, Professor at the University of Bonn and Charles University in Prague. “This is because, according to the standard model, the dark matter halos of these dwarfs should partly shield them from tides raised by the cluster.”

The scientists examined the expected amount of disturbance of the dwarfs, which is determined by their internal properties and distance from the gravitationally powerful cluster center. Large galaxies with low stellar masses, as well as galaxies near the cluster center, are more easily perturbed or destroyed. They matched the findings to the amount of disturbance shown in photos taken by the European Southern Observatory’s VLT Survey Telescope.

“The comparison showed that, if one wants to explain the observations in the standard model” – said Elena Asencio – “the Fornax dwarfs should already be destroyed by gravity from the cluster center even when the tides it raises on a dwarf are sixty-four times weaker than the dwarf’s own self-gravity.” Not only is this counter-intuitive, she said, it also contradicts previous studies, which found that the external force needed to disturb a dwarf galaxy is about the same as the dwarf’s self-gravity.

Contradiction to the standard model

From this, the authors concluded that, in the standard model, it is not possible to explain the observed morphologies of the Fornax dwarfs in a self-consistent way. They repeated the analysis using Milgromian dynamics (MOND). Instead of assuming dark matter halos surrounding galaxies, the MOND theory proposes a correction to Newtonian dynamics by which gravity experiences a boost in the regime of low accelerations.

“We were not sure that the dwarf galaxies would be able to survive the extreme environment of a galaxy cluster in MOND, due to the absence of protective dark matter halos in this model – admitted Dr. Indranil Banik from the University of St. Andrews – “but our results show a remarkable agreement between observations and the MOND expectations for the level of disturbance of the Fornax dwarfs.”

“It is exciting to see that the data we obtained with the VLT survey telescope allowed such a thorough test of cosmological models,” said Aku Venhola from the University of Oulu (Finland) and Steffen Mieske from the European Southern Observatory, co-authors of the study.

This is not the first time that a study testing the effect of dark matter on the dynamics and evolution of galaxies concluded that observations are better explained when they are not surrounded by dark matter. “The number of publications showing incompatibilities between observations and the dark matter paradigm just keeps increasing every year. It is time to start investing more resources into more promising theories,” said Pavel Kroupa, a member of the Transdisciplinary Research Areas “Modelling” and “Matter” at the University of Bonn.

Dr. Hongsheng Zhao from the University of St. Andrews added: “Our results have major implications for fundamental physics. We expect to find more disturbed dwarfs in other clusters, a prediction which other teams should verify.”

Reference: “The distribution and morphologies of Fornax Cluster dwarf galaxies suggest they lack dark matter” by Elena Asencio, Indranil Banik, Steffen Mieske, Aku Venhola, Pavel Kroupa and Hongsheng Zhao, 25 June 2022, Monthly Notices of the Royal Astronomical Society . DOI: 10.1093/mnras/stac1765

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40 comments on "new discovery indicates an alternative gravity theory".

Resuĺts are good to permit in the concerned field of astro-observation,but this is limited. However,caĺculations for obsrvations of dark matter cosmology and MOND astro-observations are always supported by rotation of galaxy,also which gives theory of coevolution of supermassive black hole at the centre of galaxy and stars.

GODBLESS your Gravity is part of Dark matter, which is the HOLY GOD, AN The HOLY SPIRIT of the HOLY GOD, be BLESSED

You speak heresy. Dark Matter is the manifestation of our dark lord, Lucifer, may He be forever triumphant.

I’m not sure what to say about the vast number of scientists who are surprised to find that they found something new about the universe. I remain in a constant state of knowing that I don’t know it all.

Colliding galaxies can loose most of their dark matter. Bigger galaxies can siphon off the dark matter of smaller galaxies. Dark matter is like gas in a gas tank it can be anywhere from full to empty. My theory of liquid and gaseous dark matter with black holes acting as either a vaporizer or condenser also moves that full or empty gauge.

Many dwarf galaxies lie in a very thin plane extending from the poles of their parent (such as the Milky Way or Andromeda galaxies) in direct contradiction to the accepted idea that a halo of Dark Matter surrounds the parent and that dwarfs should be formed all over. But also reports that many dwarf galaxies without obvious Dark Matter have stars that orbit their cores much faster than expected suggest that a significant modification of the Cold Dark Matter paradigm or new mass profiles may be needed. NAOC research suggests that unusual kinds of Dark Matter (warm, fuzzy) creates those dwarfs. There are also reports that very unexpected supermassive Black Holes have been found in some of these tiny dwarfs. What’s going on?

Specifics on this can be found by searching YouTube for “Dwarf Galaxies – A String Theory Way”

Science is partially trustworthy. I will be aware of what scientists say today and what they will say tomorrow.

Equations that work on one scale often do not work at larger scales. For example, electons do not behave like billiard balls. Similarly, Einstein’s theory of gravity works very well on the scale of a solar system but it seems unjustified to say that it also works on the scale of galaxies. With the appropriate modifications to GR, we may finally be able to get rid of black matter.

There’s a saying in motivation: things fall apart to fall into place (or fall together better). Gravity does this. So maybe the shifting in the centre occurs because atoms arrange themselves more comfortably and stably.

Opposite charges attract but similar charges repel. And the force of attraction or repulsion is relative to their magnitudes.

Did I understand the author to say that there is some kind of inverse relationship between acceleration and the force of gravity?

All the author said was “?”

Dark Matter has always felt like a temporary placeholder until we discover a more robust solution to astrophysics. I have been hopeful for MOND to gain some traction. This is good to hear about more supporting observations for MOND.

It seems almost comical at this point. We all know GR and newtonian gravity do not represent the whole picture, we know the theories are “incomplete” non-renormalizable, why don’t we just sit down and rewrite it all… it has to be done everyone knows we need a new theory we cannot continue to work within a broken mathematical model and expect to get correct results, it needs to be reworked and until that becomes the focus of the group we are stuck in this cycle, it should not fall on an individual to produce a new theory when we all know it needs to be done.

Just assume gravity is speed dependent, G proportional to square of speed, the present G being that of Earth moving at 30Km/s.Galaxies moving at very high speeds have a higher G, and so require only less matter. Available matter is enough, no dark matter is required.

Well there IS that other business of Plasma Cosmology that is patiently waiting around for all of you guys to just decide to dump gravity & admit there is another way to describe what’s out there, and that has so many advantages that don’t need your math equations (which have to be mollycoddled to make them work anyway) to explain the glorious view of what we can see in xray & other normally invisible views – plasma, plasma everywhere & nothing else needed !!!

It seems to me that given the increasing amount of evidence that the standard model is flawed and that ongoing efforts to prove the existence of Dark Matter have all turned up a blank, that it really is time to grasp the nettle and consider that MOND might be a better theory. However the science community can be very reluctant to give up old paradigms – esp in Physics.

It could be possible that these dwarf galaxies might remnants of a larger galaxy that was intersected by another galaxy and spun off. That could have happened recently enough that this particular galaxy hasn’t had a chance to reorganize itself yet.

Spyroe theory is a new concept for quantum gravity. The propeller design based on the theory, theoretically can sync to the universal field to capture its energy.

I don’t where the misconception that MOND stands for “Milgrommian dynamics” came from, but it’s incorrect: it stands for MOdified Newtonian Dynamics. A quick fact-check can confirm.

I have known since I first heard of dark matter that it was not real. Just something made up to make the current math work. Very obvious that the theories are wrong, but instead of admitting that and trying to move forward, they come up with excuses, such as “dark matter” Ok, next….

String Theory suggests a way Dark Matter could be a kind of pseudo-matter. Go to YouTube and look up “Dark Matter – A String Theory Way”

What if there was no Big Bang, but a tear in the Time Warp material allowing such things as an alternate reality?

Seems to me that Dark Matter and Dark Energy are simply a mistake. A flawed fudge seeking to explain the greater gravitational pull which normal matter could account for. But just like the “luminiferous aether” was a flawed fudge seeking to explain how electromagnetic radiation could be transmitted, in time we will realise that it doesn’t exist at all. (Which is why we cannot detect it!) Instead what we are detecting is that our understanding of gravity is incomplete, flawed even. We already know that something is wrong due to the incompatibility between General Relativity and Quantum Mechanics. So it seems to me the direction we should be looking in, is “how do we fix our understanding of gravity” rather than “let’s invent some imaginary material to fix what is clearly wrong”

I suggest that Dark Energy is a mistake, namely a mistake in how we’re measuring the distance to these objects. Go to YouTube and look up “Dark Energy – A String Theory Way”. String Theory also suggests a way Dark Matter could be a kind of pseudo-matter. Go to YouTube and look up “Dark Matter – A String Theory Way”

Based findings, Intriguing implications. Let’s see where this leads us tomorrow.

MOND stands for modified Newtonian dynamics, I’m not sure if the person that wrote this article understood what he/she/it/they ect are even on about’

ALLAH made universes

I had a theory. But I falsified it.

“Due to their low surface brightness, dwarf galaxies are particularly susceptible to tidal forces.” This is the first sentence of the abstract to the Asencio et al. paper. The referee should have caught this, since it is incorrect. Surface brightness does not affect dynamics, projected mass density does. Although the informed reader knows that, it is misleading for the lay reader.

mond is crap theory of gravity.

As I have been addressing. Einstein’s theory of relitivity in gravity is misguided. If mass distorts time/space, then what is the force distorting them? And how much mass is required to distort space/ time? Their has been no real evident to explain what is space/time, how does it pass through matter, or why matter on a smaller scale like on earth is drawn to the center of the earth, not towards mountains. Also why is their no friction in space/time? If it’s distorting then their should be mass of some sort that would induse friction! We still don’t fully comprehend gravity, is it the distortion of the unknown space/time material or a weak force? Either way it has demonstrated that it’s either a force or a distortion of space/time. All we have proven is that light has mass and it can bend around a star.wether it was pulled by gravity or it rolled around a distortion. But we still don’t fully understand gravity.

It needs a Black Hole for more stability maybe?

Mark my words… There is an extremely weak repulsive Force between SpaceTime and matter. It’s the reason why the universe looks like somebody poured oil on water. It’s also the reason why the universe is expanding faster and faster the more that matter is dispersed the more the expansive Force takes over on macro scales… It’s strength is directly proportional to distance / time from The Big bang. The universe is trying to expand to its ultimate state of expansion the only thing slowing it down is matter / gravity trapped in its web

Science and knowledge should lead us to God because He created what we are trying to understand and comprehend. The creature must look unto the creator for all revelations. God bless all that He has created.

Gravity is an effect, not a force. The sooner this is accepted, the sooner we can start moving physics forward, instead of trying to reconcile antiquated theories.

I have long argued that the hypothesis of the existence of so-called dark matter and energy is fantasy. Ask yourself which is more likely – that the universe is filled with a mysterious substance that can’t be directly observed or measured, and the composition and nature of which are completely unknown – or – some of the basic assumptions of cosmology and the standard model are either wrong or only a partial description? It’s just the same kind of paradigm change as when scientists discovered that the sun, rather than the earth, is at the centre of the solar system, and all the absurd complex explanations for apparent planetary retrograde motion could be discarded. We should always expect the simplest explanation, rather than over-complicating or postulating magic!

Here are a couple of simple explanations. I suggest that Dark Energy is a mistake, namely a mistake in how we’re measuring the distance to these objects. Go to YouTube and look up “Dark Energy – A String Theory Way”. String Theory also suggests a way Dark Matter could be a kind of pseudo-matter. Go to YouTube and look up “Dark Matter – A String Theory Way”

Sem soube que a gravidade era fale…

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'A force more powerful than gravity within the Earth': How magnetism locked itself inside our planet

T he image of an atom, with electrons swarming around a central nucleus bulging with protons and neutrons, is as iconic in our perception of science as the DNA helix or the rings of Saturn. But however much we scratch the surface of these scientific fundamentals, we can go even deeper, focusing that microscope further and discovering even more forces that govern our world.

In his new book " CHARGE: Why Does Gravity Rule? ", theoretical physicist Frank Close explores the fundamental forces that govern our world, posing questions along the way that seek to explain how the delicate balance of positive and negative charges paved the way for gravity to shape our universe.

In this except, he explains how magnetism, the most tangible fundamental forces, was discovered, where it comes from and how it got its name.   

The force within

Magnetism is a manifestation of electricity, and vice versa. Electricity and magnetism were imprinted into our surroundings from the beginning. Five billion years ago when the new-born Earth was a hot plasma of swirling electrical currents, these flows created magnetic fields. As the magma cooled to form what is today the world's solid outer crust, magnetism was locked into minerals containing iron, such as magnetite.

Today, the Earth's liquid core is still a terpsichorean frenzy of electric currents, which generate a magnetic field. This extends into the atmosphere and far beyond, invisible to our normal senses. But in spreading from its source in the molten core to the heavens above, it first permeates the Earth's crust. This is where it leaves a tangible imprint, evidence that there exists a force more powerful than gravity at work within the Earth whose influence extends very far.

Way back in the earliest Precambrian, four billion years ago, as the surface cooled, atomic elements accumulated in the strata. The most stable of these, iron, is today one of the most abundant elements in the crust. Igneous rocks formed from volcanic lava. These rocks have the property that in the presence of a magnetic field, their atoms of iron act like soldiers on parade as they themselves become magnetic. This is exploited in popular demonstrations where the magnetic field of a bar magnet can be made visible.

Small filings of iron are first scattered on the surface of a table and then a magnet is placed carefully among them. Its magnetic field induces magnetism in the iron filings, turning them into thousands of miniature magnets. Each of these duly orients itself in the magnetic field, revealing how the direction of the magnetic force varies from place to place. 

Related: Why do magnets have north and south poles?

The bar magnet is a simple model illustrating what happens for the magnetic Earth itself. Earth's north and south magnetic poles are analogous to those of the bar magnet, our planet's magnetic field extending far into space. There are no iron filings out in space, but there are large amounts of iron ores in the hills, cliffs, and mountains on Earth. In some places, by chance, these magnetic clusters are quite extensive, as on the Isle of Elba and Mount Ida in Asia Minor, where large outcrops retain the magnetic imprint in rocks known historically as lodestone, now named magnetite. 

There are legends how thousands of years ago in ancient Greece, a shepherd wearing leather shoes held in place by iron nails stumbled — literally — across magnetite when the powerful magnetism gripped the nails in his footwear. Whether or not a shepherd named Magnes discovered the eponymous rock, and if so whether it was in Magnesia, north of Athens, or on Mount Ida in Asia Minor, or even another Mount Ida in Crete, it is very likely that such experiences, if less dramatic than in the story, would have happened on various occasions. 

Certainly, the power of magnetism would have been apparent ever since the Iron Age. Lightning is a flash of electric current which generates intense magnetic fields and magnetizes ferrous rocks. Smelting to retrieve the pure iron metal from these sources would have revealed their magnetic attraction. So, the phenomenon has probably been known for some 3,000 years. Like the discovery of fire, that of magnetism probably arose in several places independently, all inspired by the natural magnetization of iron in rocks. 

For magnetic rocks are ubiquitous. By the sixteenth century travellers recorded the best examples, from East India and the Chinese coast: "Very massive and weighty, [the stone] will draw or lift up the just weight of itself in iron or steel" [ Robert Norman, The Newe Attractive, 1581 ]. As knowledge of the phenomenon spread from Greek myth to Latin, and on to English, the names morphed into 'Magnes rock' or 'magnet'. 

© [Oxford University Press]

Extract from CHARGE: Why Does Gravity Rule? by Frank Close, published by Oxford University Press, available in hardback and eBook formats  

CHARGE: Why Does Gravity Rule? By Frank Close — $21.99 on Amazon

If you enjoyed this extract, the rest of the book builds on this brief history of magnetism and delves ever deeper into the subatomic world to explore the fundamental questions of physics. It's complex stuff, but esteemed theoretical physicist Frank Close guides you through the topic with clarity, making for a highly enjoyable read. We especially enjoyed the section about the search for proton decay, which required the filling of an underground pool with 8,000 tonnes of purified water — twice. 

• News Releases

Flow research on the outskirts of space

Experiments in weightlessness isolate classic diffusion phenomenon

Helmholtz-Zentrum Dresden-Rossendorf

A reaction front spreads between two flowing liquids.

Credit: B. Schröder/HZDR

For years, various models have been developed to describe an important class of mixing effects that occur, for example, in the flow in a chemical reactor. Experimental validation, however, has lagged far behind due to the superimposition of gravity effects. A European research team involving the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and partners at the University of Szeged (Hungary) and Université libre de Bruxelles (ULB, Belgium) has now closed this gap with experiments conducted under weightlessness. The researchers recently published their results in the Nature journal npj Microgravity (DOI: 10.1038/s41526-024-00390-8).

So-called reaction-diffusion fronts occur when two chemicals react with one another and at the same time spread out. Scientists can use this effect to model and better understand problems in chemistry and physics as well as in completely different areas like the financial world or linguistics as the underlying mathematical equations have the same characteristics. It gets more complicated when researchers combine these reactions with flows. Processes of this kind are important for technological applications relating to combustion processes, geology, the production of specific materials and storing carbon dioxide. Despite the plethora of applications, essential parts of these systems are not yet fully understood.

“Up to now, experiments to verify models of such processes have been distorted by buoyancy effects caused by density differences between the reaction solutions. In order to isolate this problem, we conducted experiments using weightlessness on board of a sounding rocket. Our partners did parallel numerical simulations to show the importance of the two-dimensional effects that can’t be taken into account in simple one-dimensional models,” says Dr. Karin Schwarzenberger of HZDR’s Institute of Fluid Dynamics, outlining the work of her team.

Rocket take-off at the Arctic Circle

The experiment took place on 1 October 2022 – on board of the sounding rocket TEXUS-57 that was launched from the Esrange Space Center, 40 kilometers east of Kiruna in Sweden. The collaborative project involving Airbus Defense & Space, the European Space Agency ESA and the German Aerospace Center (DLR) transported, among other things, the Schwarzenberger team’s experimental model to the outskirts of space. The module had three reactors of different sizes consisting of glass plates stacked on top of each other at differing proximity. The rocket reached a height of 240 kilometers, achieving a state of almost complete weightlessness for nearly six minutes. During this period, the researchers were able to run their experiments automatically – experiments that resulted from several years of meticulous planning. The reaction was triggered when the weightlessness set in. Three high-resolution cameras filmed the reaction fronts that spread between two flowing liquids. It was these images that were the focus of all the team's efforts: with their help, the researchers can now separate a very specific mixing effect from other flow phenomena.

Flow physics in weightlessness

Flows in liquid channels exhibit uneven velocity distribution due to friction with the walls, which subsequently influences the transport of dissolved substances and diffusing reactants in the liquid. This diffusion effect is known as Taylor-Aris dispersion, named for the two researchers who laid the foundations for understanding it back in the 1950s. In the past, theoretical studies proposed models of varying complexity to describe the interplay of Taylor-Aris dispersion and chemical reactions.

With regard to applications, however, it is important to assess the preconditions under which the various models can be used. This meant conducting experiments to isolate Taylor-Aris dispersion from other flow phenomena. On Earth, Taylor-Aris dispersion is essentially superimposed by buoyancy effects caused by gravity. Up to now, researchers have tried minimizing the buoyancy effects by using shallow reactors – but it never worked completely because a certain range of reactor heights and flow velocities still needed to be covered in order to take in many application fields. But the larger the flow system, the stronger the gravity. The researchers have now been able to overcome these limitations in zero gravity.

A comparison with the reference experiments on the ground revealed that significantly less reaction product was generated at greater reactor heights under weightlessness. Even more important were the image data of the reaction fronts that were not distorted by the buoyancy effects. The Brussels partners were thus able to replicate the development of the front in various theoretical models. Joint evaluation showed that in very shallow reactors with slow flow, simple one-dimensional models can be used. However, in the case of larger reactors or faster flow, two-dimensional models using Taylor-Aris dispersion are required.

Within these validity range the corresponding correlations can now be employed to predict product formation. This can be used to design innovative reactors, for the targeted synthesis of particles and fluid transport in geological layers, but also to supply space stations, where gravitational conditions differ from those on Earth.

Publication: Y. Stergiou, D. M. Escala, P. Papp, D. Horváth, M. J. B. Hauser, F. Brau, A. De Wit, Á. Tóth, K. Eckert, K. Schwarzenberger, Unraveling dispersion and buoyancy dynamics around radial A + B → C reaction fronts: microgravity experiments and numerical simulations, in npj Microgravity, 2024 (DOI: 10.1038/s41526-024-00390-8)

Additional information: Dr. Karin Schwarzenberger | Head of Interface Phenomena Institute of Fluid Dynamics at HZDR Phone: +49 351 463 36 627 | Email: [email protected]

Media contact: Simon Schmitt | Head Communications and Media Relationa at HZDR Phone: +49 351 260 3400 | Mobil: +49 175 874 2865 | Email: [email protected]

The Helmholtz-Zentrum Dresden-Rossendorf (HZDR) performs – as an independent German research center – research in the fields of energy, health, and matter. We focus on answering the following questions:

• How can energy and resources be utilized in an efficient, safe, and sustainable way?
• How can malignant tumors be more precisely visualized, characterized, and more effectively treated?
• How do matter and materials behave under the influence of strong fields and in smallest dimensions?

To help answer these research questions, HZDR operates large-scale facilities, which are also used by visiting researchers: the Ion Beam Center, the Dresden High Magnetic Field Laboratory and the ELBE Center for High-Power Radiation Sources. HZDR is a member of the Helmholtz Association and has six sites (Dresden, Freiberg, Görlitz, Grenoble, Leipzig, Schenefeld near Hamburg) with almost 1,500 members of staff, of whom about 670 are scientists, including 220 Ph.D. candidates.

npj Microgravity

10.1038/s41526-024-00390-8

Method of Research

Experimental study

Subject of Research

Not applicable

Article Title

Unraveling dispersion and buoyancy dynamics around radial A + B → C reaction fronts: microgravity experiments and numerical simulations

Article Publication Date

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As many as 100 billion lifeforms – about the number of people who have ever lived on Earth – can be found in a liter of seawater. These microscopic organisms, known collectively as plankton, are the foundation of a global food chain, producers of about half the oxygen we breathe, and climate change superheroes capable of sequestering massive amounts of atmospheric carbon for thousands of years. They are also scientific mysteries, poorly understood due to high costs and erratic funding for research at sea.

Stanford bioengineer Manu Prakash dreams of revealing the secret lives of plankton, and harnessing their outsized powers. He leads an international team of researchers developing innovative, low-cost tools, such as a rotating microscope and an easy-to-use plankton sampling process , that empower citizen scientists to contribute to our understanding of ocean health and biodiversity.

“The ocean is a life-saving technology – Earth’s heart and lungs – but our perception of what it does is so primitive,” said Prakash, an associate professor of bioengineering , which is a shared department in the Stanford School of Engineering and Stanford School of Medicine . “You cannot fix what you don’t understand. Observation is the most fundamental tool scientists have for understanding.”

Tiny plankton play a huge role in regulating natural systems, but they remain poorly understood. | Madison Pobis, Rob Jordan, and Alexandra May Smith

For Prakash, who grew up in India and first saw the ocean at age 25, the effort is powered by a sense of wonder and existential imperative. His first time on a boat, about eight years ago, Prakash and his fellow researchers came upon a swath of bioluminescent plankton glowing in the silent darkness of the open ocean. “You kind of realize how small you are compared to this planet,” Prakash said. “Completely untethered, and far away from any other civilization – in that loneliness is beauty. It was a spark that made me think this is the next challenge. I really have to understand this.”

To realize Prakash’s visions for new observation tools, he has brought into his lab researchers that span disciplines, such as machine learning, computer science, fluid mechanics, cell biology, biochemistry, architecture, optics, physics, oceanography, and even visual arts and traditional tool making. The aim is to build long-term data sets of plankton migrations, and map future behavior based on predicted ocean conditions. This, in turn, could help us understand what organisms are present where in a dynamic ocean. Perhaps most importantly, it could unveil these organisms’ behaviors in current ocean conditions and their potential behaviors in altered ocean conditions of the future.

In the years and many observations since Prakash’s first ocean expedition, his sense of our wonder has only grown. “I've seen organisms that are smaller than one-tenth the size of a grain of rice chase each other, like the whole African savannah play out in a tiny little drop of water,” he said. “When you multiply that by the size of the ocean, you start realizing we don't have methodologies to understand the complexity at these scales.”

A plankton world

Little is known about plankton’s distribution and variation. At the same time, about 40 percent of people on Earth live on or near a coastline, and many make their living or find recreation on the sea. Prakash and a team of scientists, engineers, makers, and sailors from France, the U.S., and New Zealand – wondered how to harness this human capital. So they created Planktoscope , an international initiative to engage people in designing and deploying low-cost instruments to study plankton, and put their findings in public databases.

In partnership with PlanktonPlanet, another gathering of plankton enthusiasts, the team tested simple, low-cost sampling process, including a net to gather plankton, and a manual pump to transfer them onto a filter. Citizen scientists then dry out the membranes in their boats’ gas-cookers, and mail them to a lab for analysis. Using this protocol, 20 crews of citizen sailors – “planktonauts,” as the researchers called them – were able to build a “planetary dataset of plankton biodiversity” showing scientists which organisms are where.

The researchers acknowledge that planktonauts will not be able to gather the sort of comprehensive data that oceanographic vessels routinely collect, and frame the citizen science effort as a complement to, not a substitute for intensive expert research. Deployment of the first kits on key navigation loops and routes started in 2023, and an ongoing citizen science survey of global surface plankton is set to launch by the end of this year, according to Prakash.

The PlanktoScope

Rather than send samples to a lab for analysis, citizen scientists could do it themselves, Prakash reasoned. So, together with participants from around the world, his lab developed an open source imaging platform that matches the quality of much larger and more expensive commercial instruments. Called the PlanktoScope , it is portable and easy to operate from any Wi-Fi-enabled device. Its components are off the shelf, easy to find, and the necessary materials cost less than $800 in total. The designs use a laser-cut framework, and can be made with materials ranging from acrylic and recycled plastic to wood, metal, and fiberboard. An open-source single board computer controls the electronics and processes the images.

Over the course of more than 20 oceanic voyages in a short period of time, the PlanktoScope has demonstrated its capacity to analyze plankton in field conditions. During a 45-day scientific expedition to the Arctic , the Planktoscope collected data from more than 200 field stations and continuously monitored plankton in open waters and under ice cover. On a two-month ocean journey from France to Chile, the device brought back results that matched up with previous observations showing that surface plankton compositions are essentially controlled by nutrient limitations. Prakash’s passion for making scientific observation accessible led him to post detailed Planktoscope manufacturing instructions on the project’s website . Hundreds of people around the world have built and replicated the tool since then.

Prakash and researchers in his lab have distributed more than 150 Planktoscopes for citizen science applications ranging from monitoring coastal aquaculture in California to finding harmful algal blooms in Indonesia. Thibaut Pollina, a former researcher in Prakash’s lab and co-inventor of the Planktoscope, currently manufactures the device for sale to people who don’t want to build it themselves.

“It’s a joy to see this tool in the hands of people I have never met,” Prakash said.

The ‘gravity machine’

Perhaps the most revolutionary of Prakash’s plankton-observation tools is something he jokingly calls the “gravity machine.” Because plankton’s daily migration between the ocean depths and surface can span tens of thousands of feet and many days, there is no effective way to watch it unfold. To capture this journey, Prakash and researchers in  his lab developed a vertical tracking microscope based on what they call a “hydrodynamic treadmill.” The idea involves a simple yet elegant insight: a circular geometry provides an infinite water column ring that can be used to simulate ocean depths. Organisms injected into this fluid-filled circular chamber move about freely as the device tracks them and rotates to accommodate their motion. A camera feeds full-resolution color images of the plankton and other microscopic marine critters into a computer for closed-loop feedback control.

Stanford researchers Manu Prakash and Deepak Krishnamurthy use a rotating microscope that they developed to observe a single-cell diatom, a type of plankton, as it changes its density to move through water. (Image credit: Hongquan Li)

With funding from the Big Ideas for Oceans program of the Stanford Doerr School of Sustainability’s Oceans Department and the  Stanford Woods Institute for the Environment , Prakash is developing ways for the rotating microscope to recreate changing ocean characteristics, such as light intensity, pressure, and water temperature, creating what the researchers call a “virtual reality environment” for single cells.

Read about the funded project:  Simulating plankton migrations on a tabletop

“We will create and emulate every single parameter that plankton can perceive,” Prakash said. “That's really the magic of technology. I could program the machine to be emulating the Mediterranean or Chukchi Sea.”

Perpetual innovation

Prakash and his fellow researchers in the lab envision making versions of all of their tools that are autonomous and portable, able to take measurements onboard any boat, and available – via satellite – so students and others around the world can control them and analyze resulting data. The researchers are expanding a library of parts that allows people to reconfigure the instruments in many different ways. They are also putting together an online data set of plankton behavior video footage for more than a thousand different species, the largest behavioral data set for aquatic species.

“There’s a lot of anxiety around the collapse of ecosystems," Prakash said. “Every time I’m depressed I think about the aesthetic and the beauty of the microscopic world. It brings me out every single time. It’s brutal. It’s very unorthodox. It’s very non-intuitive. But there’s a lot of hope because you just see the abundance, you see how powerful these tiny creatures really are."

This project was funded by the  Big Ideas for Oceans program of the  Stanford Doerr School of Sustainability’s Oceans Department and the  Stanford Woods Institute for the Environment . Get more news about Woods-sponsored research on our  In Focus page, or by signing up for our newsletter and seed grant announcements .

Prakash is also an associate professor (by courtesy) of biology at the Stanford School of Humanities and Sciences ; an associate professor (by courtesy) of oceans at the Stanford Doerr School of Sustainability ; a senior fellow at the  Stanford Woods Institute for the Environment ; a member of  Bio-X , the  Maternal & Child Health Research Institute, and the  Wu Tsai Neurosciences Institute ; a faculty fellow at the Howard Hughes Medical Institute; and an investigator at the Chan Zuckerberg Biohub.

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Gravitation

Gravitation is a natural phenomenon by which objects with mass attract one another. In everyday life, gravitation is most commonly thought of as the agency which lends weight to objects with mass. Gravitation compels dispersed matter to coalesce, thus accounting for the existence of the Earth, the Sun, and most of the macroscopic objects in the universe. It is responsible for keeping the Earth and the other planets in their orbits around the Sun; for keeping the Moon in its orbit around the Earth; for the formation of tides; for convection, by which fluid flow occurs under the influence of a temperature gradient and gravity; for heating the interiors of forming stars and planets to very high temperatures; and for various other phenomena observed on Earth. Modern physics describes gravitation using the general theory of relativity, in which gravitation is a consequence of the curvature of spacetime which governs the motion of inertial objects. The simpler Newton's law of universal gravitation provides an accurate approximation for most calculations.

The terms gravitation and gravity are mostly interchangeable in everyday use, but a distinction is made in scientific circles. "Gravitation" is a general term describing the phenomenon by which bodies with mass are attracted to one another, while "gravity" refers specifically to the net force exerted by the Earth on objects in its vicinity as well as by other factors, such as the Earth's rotation.

This text uses material from Wikipedia , licensed under CC BY-SA

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