Gravity Mysteries – We May Have Had Fundamental Nature of the Universe Wrong This Whole Time

Gravity Mysteries Chalkboard

Silly questions lead to surprising answers about the fundamental nature of the universe. We might have been getting it wrong this whole time. Credit: Kavli IPMU

Symmetry has been one of the guiding principles in physicists’ search for fundamental laws of nature. What does it mean that laws of nature have symmetry? It means that laws look the same before and after an operation, similar to a mirror reflection, the same but right is now left in the reflection.

Physicists have been looking for laws that explain both the microscopic world of elementary particles and the macroscopic world of the universe and the Big Bang at its beginning, expecting that such fundamental laws should have symmetry in all circumstances. However, last year, two physicists found a theoretical proof that, at the most fundamental level, nature does not respect symmetry.

How did they do it? Gravity and hologram.

There are four fundamental forces in the physical world: electromagnetism, strong force, weak force, and gravity. Gravity is the only force still unexplainable at the quantum level. Its effects on big objects, such as planets or stars, are relatively easy to see, but things get complicated when one tries to understand gravity in the small world of elementary particles.

The researchers showed that symmetry only affects the shaded regions in the diagram, not around the spot in the middle, thus there cannot be global symmetry. Credit: Kavli IPMU

To try to understand gravity on the quantum level, Hirosi Ooguri, the director of the Kavli Institute for the Physics and Mathematics of the Universe in Tokyo, and Daniel Harlow, an assistant professor at the Massachusetts Institute of Technology, started with the holographic principle. This principle explains three-dimensional phenomena influenced by gravity on a two-dimensional flat space that is not influenced by gravity. This is not a real representation of our universe, but it is close enough to help researchers study its basic aspects.

The pair then showed how quantum error correcting codes, which explain how three-dimensional gravitational phenomena pop out from two dimensions, like holograms, are not compatible with any symmetry; meaning such symmetry cannot be possible in quantum gravity.

They published their conclusion in 2019, garnering high praise from journal editors and significant media attention. But how did such an idea come to be?

There are four fundamental forces in the physical world: electromagnetism, strong force, weak force, and gravity. Gravity is the only force still unexplainable at the quantum level.

It started well over four years ago, when Ooguri came across a paper about holography and its relation to quantum error correcting codes by Harlow, who was then a post doc at Harvard University. Soon after, the two met at the Institute for Advanced Study in Princeton when Ooguri was there on sabbatical and Harlow came to give a seminar.

“I went to his seminar prepared with questions,” Ooguri says. “We discussed a lot afterwards, and then we started thinking maybe this idea he had can be used to explain one of the fundamental properties of quantum gravity, about the lack of symmetry.”

New research collaborations and ideas are often born from such conversations, says Ooguri, who is also a professor at the California Institute of Technology in the U.S. Ooguri travels at least once a fortnight to give lectures, attend conferences, workshops, and other events. While some might wonder if all that travel detracts from concentrating on research, Ooguri believes quite the opposite.

“Scientific progress is serendipitous,” he says. “It often happens in a way that you don’t expect. That kind of development is still very hard to achieve by remote exchange.

“Yes, nowadays it’s easier with e-mails and video conferences,” he continues, “but when you write an e-mail you have to have something to write about. When someone is in the same building, I can walk across the hallway and ask silly questions.”

These silly questions are key to progress in fundamental sciences. Unlike other fields, such as applied science where researchers work towards a specific goal, the first question or idea a theoretical physicist comes up with is usually not the right one, Ooguri says. But, through discussion, other researchers ask questions derived from their curiosity, taking the research in a new direction, landing on a very interesting question, which has an even more interesting answer.

Reference: “Constraints on Symmetries from Holography” by Daniel Harlow and Hirosi Ooguri, 17 May 2019, Physical Review Letters.
DOI: 10.1103/PhysRevLett.122.191601


View Comments

  • Science will never find the answer to the physical world by studying the physical world. First, you have to admit there are some things you will never understand; second, you already have all the information you need. Wisdom from the EAST, apparently missed by some researchers, 'all wisdom comes from within'.

    • Science *does* admit there are things we might never understand, your understanding of science is very poor. Science is just the usage of the scientific method, and that method makes no assumption about what can and can not be understood. We just try to understand as much as possible, that's it. I guess it's not surprising you don't understand why we know the earth isn't flat, if you don't understand how science works ...

      "All wisdom comes from within" sounds nice, but I really doubt you can show how that concept is in any way useful in determining the shape of the earth. You can prove me wrong pretty easily if you have good reasons for your position though ...

    • "All wisdom comes from within?" Where else would it come from. But still gotta test your ideas against reality. Get rid of the wrong ones. Build on ones that work. Or you're gonna walk down the path of delusion.

  • I'm not trying to be rude. Presuming gravity exists isn't going to work anymore, in light of facts of perspetive and the law of CURVATURE. If scientistic practitioners are still clinging to the spinning ball theory, no wonder you're still confused. Our horizons are all flat, although our world's depth of crust is very geeat in terms of volcanic cavities, water cavities and empty cavities. You guys still have a long way to go, to explain where we are--standing on what.

    • I'm confused are you a flat Earther that doesn't believe in gravity? If so that certainly is a new one for me

    • There is no such thing as the "law of curvature". You can't just make-up science, that's not how any of this works.
      The horizons we have ( which you might describe as flat with some mental gymnastics ) are in fact compatible with a globe earth. And to believe the earth is flat, you have to ignore sattelites and sattelite imagery, which means going into crazy conspiracy theories that do not have any leg to stand on.

  • That illustration fits all of my definitions of symmetry so I don't see what they're saying. If you say "symmetry" over and over it loses all meaning. I see a huge amount of symmetry in that illustration, no matter how you slice it, it passes their own mirror test! I don't buy the no-symmetry idea on the face of it.

  • OK, of the three comments so far, two seem from Full Canvas Jacket territory, and the third commentator doesn't seem to have read the caption of the photo in question...

  • I know this sounds like "We faked the moon landing" and I know you guys have a whole bunch if time and grant money tied up in this whole gravity thing but hear me out.

    Matter only interacts with matter via electro-magnetism.

    Matter does not interact with other matter via gravity. Mass is not attracted to mass.

    Matter interacts with space via gravity. To space matter looks like a space vacuum. Space is compressing matter and creating the currents and eddies of our universe. We can't measure anything in space via electro-magnetism but we could with gravity.

    I call this my glass of beer theory of the universe. When looking at a glass of beer you see bubbles forming and rising to the top of the glass and occasionally colliding into each other. If we were the little bubbles of CO2 then we would see the beer as a vast nothingness. Then we would say that CO2 bubbles are attracted to each other and that pull of the air above generally controls the movement of us bubbles. It reality it is the beer that is controlling the bubbles and pushing them towards the top of the glass. If you compress the beer enough the bubbles will actually disappear back into the beer.

    So the earth creates a space vacuum that space wants to push the moon towards because the earth is eliminating some space from one side of the moon.

    I believe this is a very week force but there is a really large number of space so it adds up. I have no idea how to start calculating the repulsive force of a cubic millimeter of space so good luck there.

    I think this would help
    The math on the early universe were expansion was slower then sped up
    The existing acceleration of the expanding
    Why gravity isn't a factor in quantum physics
    Dark Matter
    How far from the center of the universe we are
    It might help with
    Explaining the Speed of light
    Black holes
    Hey you got this far down! Thanks for listening!

    • I did you the service to read past the first sentence, but stopped at the second since we know it is dead wrong. So thanks for the warning about spamming nonsense.

    • You're comparing apples to oranges especially when space is already a vacuum and buoyancy is a significant force in your analogy. Have you heard of the General Theory of Relativity? That's a good place to start.

  • There is a saying that goes back to Euclid that goes "from a falsehood, anything follows". We do not live in an AdS universe, and it is an assumption requiring proof that gravity must be quantized. In fact, the results of this paper (which I have read, not just the news article) can be taken as proof that gravity cannot be quantized. My personal opinion, since I studied physics at MIT back in 1964, is that General Relativity is exact and correct in the same way that Statistical Mechanics is correct, mathematically.

    • Thanks, finally an interesting comment! (But by now I looks like I have spammed practically the whole thread. :-/)

      As you can see from my comment on the article we agree on AdS (and probably on holography).

      That gravity needs to be quantized is an interesting question. The usual take is that quantum field physics is effective since field theories eventually break down, latest at Planck scale. And similarly that general relativity is effective for the same reason. It is also claimed that general relativity is classical, while nature is quantum physical.

      So if you want to combine them - and perhaps derive the test you are asking for - it is now doable.

      First, we can see that quantum field physics is linearized but obey special relativity and has no preference on space curvature - semiclassical physics combine quantum fields and curvature. What this does to classical fields is that the fields that more or less successfully replaced instant "action-at-a-distance" with the concept of field lines are converted to a quantum vacuum with non-resonant fluctuations ("virtual particles") where particles are created and destroyed as resonant, localized ripples and entanglement maximally take back light cone localization and causality from special relativity. The field lines are gone, replaced by an amorphous set of interaction mechanisms (particle collision perturbations modeled by Feynman diagrams and what not).

      Second, if we take a gravity Lagrangian we can make a linearized quantum field theory that breaks down precisely at Planck scale (since gravity is the weakest force). It will fulfill the Lorentz conditions and emulate weak curvature [ ]. Now if we analogously to how we replaced the the useful, apparent classical calculation device of field lines replace the useful classical calculation device of geodesic lines by taking it as apparent, we have gravity on a flat background closing the physics - fulfilling the Lorentz conditions - so we have laws at all.

      Is taking curvature out to be a device of a classical model in the same way that we took field lines out, too much to ask? Maybe not.

      Here is a possible test of an "all-in-quantum-field" physics:

      "It is interesting that the bending angle depends on the type of massless particles. The particles no longer simply follow geodesics. This violates some ways that we talk about the equivalence principle. However it is not a violation in a fundamental sense. It is a manifestation of the fact that in quantum loops, massless particles propagate long distances. The long-distance propagation of massless photons and gravitons is not localized, and consequently can be interpreted as a tidal correction in that the massless particle is no longer describable as a point source. There is then no requirement from the equivalence principle that such non-local effects be independent of the spin of the massless particle. However, it is interesting that quantum effects predict such a difference, without any free parameter, modifying one of the key features of classical general relativity." [ibid]

      • To be even more complete (aka wordy), general relativity breaks down at Planck scales if such energies are approached inside black holes - black holes are taken as the sign that general relativity is effective.

        And I should not say that quantum physics take back causality as much as correlation while still obeying causality. It is in fact relativity which mess with order of events in order to preserve laws [ ]. But it is maximal "take backsies", since you can cram as much entanglement you want into a point since Hilbert space is practically infinite. For me that knife edge balance under constraint is another point for the case that relativity and quantum physics "are made for each other". But your personal mileage may vary.

  • "This is not a real representation of our universe, but it is close enough to help researchers study its basic aspects."

    No, other scientists consider the Holographic Principle a very real representation of our universe, that's why it's a "Principle". It was convenient to immediately identify the author's worldview, though, since this structure to the universe is absurdly improbable in a universe without a God. Therefore, even though it's clearly hard science, it must be dismissed immediately.

    • ? Are you claiming a falsehood? God magic doesn't work, since a flat universe is both all there is (by general relativity) and thermodynamically closed (by zero energy density), we have known this since Planck 2018 cosmology data summary.

      • If I can manipulate quantum phenomena (which would be the ideal "back door" for a God to "install" as part of the design of the universe), I can do absolutely anything. Any miracle whatsoever, as soon as it isn't the (as would be brilliant "universe hacking" cover) random distribution it appears to be. It was claimed that quantum behavior could affect things at a macro scale, but the worldwide constant effects of quantum computing will prove that quite false.

          • Ah, and the co-incidentally Norwegian girlfriend of this American (not "coincidentally", but co-incidentally) suggests I mention...

            "Det er mer mellom himmel og jord enn de fleste andre steder."

            Apparently you'll somewhat understand that. Somewhat.

        • Yeah, so you are arguing that 3 or 4 thousand years absence of "miracles" isn't sufficient test on its lonesome? Please lay of such incredulous Bronze Age myth.

          I am referencing modern physics. Religion has been as much shown to be falsehood in this century as astrology was shown in test the last century. ("Horoscope magic" did not work in blind tests 1980ish, "star sign magic" was rejected by astronomy 1930ish.)

          - 2018 Planck cosmology: no "god magic" (see above).
          - 2011-217 LHC standard model - the very "miracle" you asked to test - no "soul magic", no "afterlife magic" possible since the remnant exotic physics is too weak. And it is water proof since quantum field physics perturbations can always be modeled as particle collisions, and we need to know enough to complete the standard model - which we have. What you ask for has been tested as impossible many times over by now! Brian Cox, Sean Carroll and other physicists has made that point since then.
          - 2006 Pew population statistic summary - no "prayer magic". "Intercessory prayer" did not work in test.

          So you may think others don't see religion falsehood as on the level of astrology falsehood. But more and more do, for obvious reasons: it is the way nature is, and it so far we have made it based on observation, we know this now.

          • There's been no absence of miracles. Just absence from your life. But do expand on your psychic capabilities to know all the experiences of everyone -else's- entire life, to review them and verify the absence of miracles.

            "Religion has been as much shown to be falsehood in this century as astrology was shown in test the last century."

            Not in the least. You're simply lying. That's why, we have 2.2 billion religious people, which would not be the case if it was in fact "shown to be falsehood".

            "2018 Planck cosmology: no “god magic”"

            You can't eliminate what is wider than observables in the case of religion any more than you can refute Everett Multiverse by reference to the fact you don't see them in your observations of this one. Nor can you refute things outside of our observable universe by reference to the claim you don't see them in this one.

            Godel's Incompleteness Theorem shows that this never works, even theoretically.

            "What you ask for has been tested as impossible many times over by now!"

            Ah, no, I'm unconvinced by this claim. You don't know what manipulations are possible to a being that has the equivalent of infinite technology, and that we haven't observed it doesn't alter that.

            "“Intercessory prayer” did not work in test."

            And as a "scientist" you miss the essential nature of a Control Group. It is impossible to define a group of participants that "aren't being prayed for". No Control Group, no science.

            "So you may think others don’t see religion falsehood as on the level of astrology falsehood. But more and more do, for obvious reasons: it is the way nature is, and it so far we have made it based on observation, we know this now."

            I think it because it's true, per 2.2 billion data points. You know what nature is, perhaps, though that is constantly changing. You -don't- know what is outside of nature, and you -don't- know there isn't anything outside of it.

  • Other than the fact that this came out last year, I imagine Sabine Hossenfelder (Lost In Math) popping a few champagne bottles.

    Congratulations to Prof. H & the theoreticians above. Very big news. Read her book if you haven't.

    Somebody interview Lee Smolin & Carlo Rovelli, please.

    • I would not read that. All those three are fringe (and mostly known to be wrong, say Smolin's white hole physics and Rovelli's loop physics which has no dynamics).

      Read peer reviewed consensus physics instead, much more factual.

      • Peer reviewed papers have gotten us nowhere for decades. They all mistakenly base everything about gravity on the lambda CDM model. In order to finally understand gravity, we must do what I've heard hundreds of scientists suggest for many years which is find a completely new model to explain the origin of our universe. That's what Edwin Hubble tried to do but was ignored. I explain below.

        • I immediately doubt what you are saying based on your argument from authority. I seriously doubt Hubble would have discovered what he did by listening to people who espoused the "every scientist I ever met" test.
          I smell disinformation.

  • This reads as a public relations effort from the Kavli Institute, based on referencing a year old result.

    That result [ ] seems in itself of ambiguous value, even if it is part of illuminating results on symmetries in physics.

    For one, it is a hypothesis that holography is realized, apart from its usefulness in deriving physics.

    For another, all field theories are known to be effective in some sense or other - they all break down latest at Planck energy scales - so if their internal symmetries (laws of gauge theories) are just approximate "in the [holographic] bulk" the implications seem weak to non-existent.

Kavli Institute for the Physics and Mathematics of the Universe

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