What Are Gravitons?

In a contest for the least contentious statement a person can make, “What goes up must come down” is surely a strong contender. Of the four known fundamental forces—gravity, the electromagnetic force, and the strong and weak nuclear forces—we have the most intuitive understanding of gravity. From our first experiments dropping Cheerios from our high chair, we spend our lives coming to grips with the limitations that gravity imposes on us.

Credit: Christoph Zurbuchen/Flickr, adapted under a Creative Commons license.

In the late 1600s, Isaac Newton devised the first serious theory of gravity. He described gravity as a field that could reach out across great distances and dictate the path of massive objects like the Earth. Newton’s theory was stunningly effective, yet the nature of the gravitational field remained a mystery. In 1915, Albert Einstein’s theory of general relativity gave theorists their first look “under the hood” of gravity. What we call gravity, Einstein argued, is actually the distortion of space and time. The Earth looks like it’s rounding the Sun in an ellipse, but it’s actually following a straight line through warped spacetime.

Einstein’s theory of gravity is very good at explaining the behavior of large objects. But just a few years later, physicists opened up the world of the ultra-small, revealing that the other fundamental forces are due to the exchange of specialized force-carrying particles: photons convey electromagnetism, the strong nuclear force is transmitted by gluons and the weak nuclear force is imparted by the movement of the W and Z bosons. Is gravity due to the same kind of particle exchange?

We actually don’t know the answer to that question, but we have a name for that hypothetical particle if it does exist: It is called the graviton. And even though we have never observed a graviton, we know a great deal about them, if they are real. First, since the range of the force due to gravity is infinite and the force due to gravity weakens as one over the square of the distance between two objects (i.e. 1/r2), the graviton must have zero mass. We know this because if the photon had mass, it would change the “2” in the exponent and that “2” has been established with incredible precision. Like massless photons, gravitons should travel at the speed of light.

General relativity also gives us some insight into the nature of gravitons. In general relativity, the distribution of mass and energy in the universe is described by a four-by-four matrix that mathematicians call a tensor of rank two. This is important because if the tensor is the source of gravitation, you can show that the graviton must be a particle with a quantum mechanical spin of two. Another nice fallout of this correspondence is that the graviton is the only possible massless, spin two particle. If you observe a massless, spin two particle, you have found the graviton.

So why hasn’t anyone found a graviton yet? The problem with searching for gravitons is that gravity is incredibly weak. For instance, the electromagnetic force between an electron and a proton in a hydrogen atom is 1039 times larger than the gravitational force between the same two particles. Perhaps a more intuitive example is the behavior of a magnet and a paperclip. A magnet will hold a paperclip against the Earth’s gravity. Think about what that means. A little magnet, like the one that held your art to your parent’s refrigerator when you were a kid, pulls the paperclip upwards, while the gravity of an entire planet pulls downward, and the magnet wins.

Individual gravitons interact very feebly, and we are only held to the planet because the Earth emits so many of them. Because a single graviton is so weak, it is impossible for us to directly detect individual classical gravitons.

However, there are new and innovative ideas about gravity in which other forms of gravitons might exist. Some of these exotic gravitons might be detectable, but they require significant modifications to our understanding of our universe. This is where things get a bit mind-bending.

If “what goes up, must come down” might be a catch phrase for Captain Obvious, “we live in three dimensions” could be the rallying cry of his sidekick, Lieutenant Duh. However, some scientists have proposed the idea that gravity might have access to more than three dimensions. In that case, gravity might not actually be as weak as we think it is. It only appears weak because, unlike the other fundamental forces, it has extra dimensions into which it can “spread out.”

On the face of it, this seems silly. The 1/r2 nature of gravity is an incontrovertible sign that gravity operates in three dimensions, and this behavior has been directly verified down to distances smaller than a millimeter. But this leaves open the possibility of extra dimensions smaller than 150 micrometers or so. One can imagine these small dimensions by thinking of a tightrope. To a tightrope walker, who can only walk forward and backward on the rope, the rope is one-dimensional. But to an ant, which can also crawl around the rope’s circumference, the rope seems to be two-dimensional. What appears to be one-dimensional to a large being is two-dimensional to a smaller one. These smaller dimensions are cyclical in that if you travel around the outside of one, you will end up back in the same place.

Quantum mechanics tells us that every particle is also a vibrating wave, and it has been proposed that gravitons could vibrate in these extra dimensions, wrapping around the small dimension like bracelets encircling a slender wrist. However, the cyclical nature of the extra dimension imposes limits on how a graviton can vibrate. Only an integer number of wavelengths can fit evenly in the extra dimension. And this brings us to a couple of interesting consequences. In theories with extra dimensions, more than one type of graviton can exist. One way to see that is to imagine taking a sine wave and wrapping it around a cylinder. In order for it to fit perfectly, you must use one wavelength or two or three or any integer number of wavelengths. Each of these instances is a distinct graviton; the ones with more vibrations can actually have mass. Particles of this kind are called Kaluza-Klein gravitons after physicists Theodor Kaluza and Oskar Klein, who first proposed the idea of additional small spatial dimensions. On tiny scales, Kaluza-Klein gravitons can have mass, but on larger scales, they reduce to the familiar massless gravitons of classical theory.

Using particle accelerators like the Large Hadron Collider, physicists are already searching for these small extra dimensions, in part by looking for the expected decay products of massive gravitons. They haven’t found anything yet, which means that if extra dimensions exist, they must be a thousand times smaller than a proton, although there are many caveats to how one interprets the data.

Gravity is the one known fundamental force that has resisted study in the quantum realm and finding gravitons of any kind would be a huge step forward in our understanding of the phenomenon. Devising a successful theory of quantum gravity is one of the hottest goals of modern physics and ongoing experimental searches for gravitons will play a central role.

Go Deeper
Our picks for further reading

Nature of Reality: What Is Gravity Made Of?
In this video blog, physicist Greg Kestin describes the 2014 results from the BICEP2 experiment and their implications for gravitons and quantum gravity.

The Physics Teacher: Extra Dimensions of Space
Author Don Lincoln explains what physicists talk about when they talk about extra dimensions.

Poincare Prize Lecture: Is a Graviton Detectable?
In this technical lecture, eminent theorist Freeman Dyson asks whether it will ever be possible to detect gravitons.

Warped Passages: Unraveling the Mysteries of the Universe’s Hidden Dimensions
In this popular book, Harvard physicist Lisa Randall explains why theorists believe extra dimensions may exist, and how we might find them.

Tell us what you think on Twitter, Facebook, or email.


Don Lincoln

    Don Lincoln is a senior experimental particle physicist at Fermi National Accelerator Laboratory and an adjunct professor at the University of Notre Dame. He splits his research time between Fermilab and the CERN laboratory, just outside Geneva, Switzerland. He has coauthored more than 500 scientific papers on subjects from microscopic black holes and extra dimensions to the elusive Higgs boson. When Don isn’t doing physics research, he spends his time sharing the fantastic world of science with anyone who will listen. He has given public lectures on three continents and has authored many magazine articles, YouTube videos and columns in the online periodical Fermilab Today. His most recent book "The Large Hadron Collider: The Extraordinary Story of the Higgs Boson and Other Stuff That Will Blow Your Mind" tells the tale of the Large Hadron Collider, the physics and the technology required to make it all work, and the human stories behind the hunt for the Higgs boson.

    • Scott McKay

      is it possible that gravitons are the gray matter that we search for?

      • Don Lincoln

        No…I believe you mean dark matter, but gravitons don’t have mass and don’t cause gravity…they transmit gravity. Dark matter, if it exists, causes gravity. In some sense it is like ordinary matter, except it doesn’t interact with light. So no go.

        • Scott McKay

          yes thats what I meant. Dark matter. Thank you for correcting that. It was just a thought.

    • john

      so what is the difference between Graviton and the bending of the fabric of space-time?

      • Don Lincoln

        The difference is similar to a water molecule and a wave of water. Both H20 and a surfer’s delight are the same thing, but qualitatively very different.

        Concentrations of energy (i.e. mass) emit many gravitons and, in so doing, distort space.

        Of course, since we aren’t even sure if gravitons exist, there is no reason to be confident of any statements made here. What I am describing is the qualitative features of a theory, not established fact.

    • Kort Beck

      But, if gravitons doesn’t have mass , how does exist? , this article refers to the string theory i think, that theory is true? the vibrating string exist?

      • Don Lincoln

        Well photons don’t have mass and they surely exist.

        String theory is certainly not verified and some would call it pie-in-the-sky speculation. Personally, I like the elegance of the superstring idea, however I do not allow my sense of aesthetics get in the way. Until the idea is proven, superstrings must be relegated to the “not yet proven” category.

        • Alone: bad. Friend: good!

          “Well photons don’t have mass and they surely exist.” — whoooops

    • Aiden

      Faraday first postulated fields. Not Newton

      • Don Lincoln

        True to a degree. However, you have made a historical statement. The gravitational field as we understand it is wholly contained within Newton’s work. We just think of it differently nowadays. Thus I stand by the statement in the article as it hinged on the understanding of gravity rather than the field concept. Essentially the Newton insight was more central to the point that the field one.

    • Anonymous

      Thanks for another great article Dr. Lincoln. The notion of quantized gravity in the spotlight due to the recently published research has me asking questions about how we came to understand any of the forces as quantized. In my head I envision a wall being peppered with pellets like in the double-slit experiment. I’m not quite sure even how to ask the question…but what does it mean to be quantized? What actually separates one particle from another? Empty space? We know now space isnt empty. What does this mean for what is happening in the empty space between particles in a stream? I guess this questions begs more fundamental question…why is anything quantized? Is the quantum nature of reality objectively real or have we imposed this “nature” upon reality because, by definition, to study something you must have a discrete “thing”/particle to study?

      Regarding gravity’s relative weakness in comparison to the other forces, I am reminded that in the singularity prior to the Big Bang the forces were united. If a large portion of gravity’s strength is bound in smaller dimensions could it in fact be appearing or manifesting as, say, the strong nuclear force?

      • Don Lincoln

        Just some brief thoughts.

        If you drop a pebble in water, you’ll see a localized wave pattern travel across the water. This is a quantized wave. This is in contrast to the continuous stream of waves that hits a shoreline. And we certainly know that matter is quantized. We can manipulate individual atoms. Further, we can extract individual electrons, protons or neutrons. It’s harder to see when talking about energy, but not fundamentally different.

        Regarding the gravity moving into extra dimensions being the strong nuclear force…I dunno…probably not, but we don’t have a theory of quantum gravity, so it’s hard to say anything definitively. I guess I think your implied proposal is unlikely, but I’ll hedge with a shrug and a beatstheheckouttame. We’ll have to wait for a clever lad or lass to come up with a good theory of quantum gravity and go from there.

        • Anonymous

          LOL! Sounds like a plan. Re: quanta, thank you, your analogy helped me understand the concept much better. Am I correct though in understanding that the distinction between the causes of these waves, the pebble and the wind respectively, and the waves themselves being particles of water moving in a certain pattern, is where the analogy breaks down?Because, at the subatomic level we’re discussing, in some mysterious way both the particle (localized “center” of the wave) is made of the same ‘stuff’ as the wave itself and they are, in fact, one? Or maybe I should just understand it the way we talk about electromagnetism – the force we care all most familiar with – that with charge comes a field called magnetism that behaves in a wave like way, and that it doesn’t make sense to speak of one without the other? Is this the more accurate way to conceptualize the wave-particle duality?

          • Don Lincoln

            I’m afraid I didn’t understand that well enough to answer.

            • Anonymous

              I was just trying to point out that in the analogy the pebble and the waves it creates are two separate things whereas, at the subatomic level, the particle and wave are the same thing, two sides of the same coin so to speak. And, in fact, that a single particle is also a wave. I’m referencing the paradox in the double-split experiment of how a single photon/particle can produce a wave pattern when, accd to everyday experience, it takes multiple particles to create a wave pattern. As far as I understand it – or think I understand it – the wave is the field (or perhaps put another way, the “range of influence” of the particle) by which the particle interacts with other particles. And that the particle, per your analogy, is at the “center” of the wave pattern. I was just wondering if I am understanding this wave-particle duality correctly, making the concept more difficult than it is or if there is still something I am missing.

            • Don Lincoln

              It is true that the pebble and the ripple are different, but they do not well represent the particle/wave dichotomy. A traditional wave goes on forever and ever…like a sine wave. A particle has a fixed position. A ripple is a localized wave. Thus the ripple has both particle and wave properties. That was the analogy I was trying to make.

            • Anonymous

              Ahhh…that really makes sense. I get it now.

              Thanks so much for your time and continuing engagment with the public in this forum. I appreciate very much that a scientist of your stature is willing to help the public understand the wonders of the universe.

            • Don Lincoln

              Glad it helped. I can’t always answer every question, but it’s nice when I can. Keep learning.

    • hardi sura

      do antigravitons exist or are gravitons their own anti particles like photons?

      • Don Lincoln

        It is expected that gravitons are their own antiparticle.

      • Proton

        Antigravitons do exist but they are expected to attract gravitrons.

        • Don Lincoln

          We don’t know if antigravitons exist, simply because we don’t know if gravitons exist. However gravitons and antigravitons are the same particle, just like photons.

          Particles with energy bend space and thus all particles with mass or just energy end up attracting one another.

    • Lochandubh

      Little square fried pieces of bread you sprinkle on soup n salads ?

    • George Raina
    • Mario

      What goes up… What about escape velocity?

      • Don Lincoln

        Yes, yes…we can all be pedantic. But a little literary flair adds to how interesting a story can be. My advice is to chill and enjoy the vibe. If you’re smart and educated enough to know about escape velocity, you’re smart and educated enough to let it go when it is clear that the author also understands a point and has made a literary choice.

        • Curious

          Since the other 3 forces have carriers, isn’t it likely that there is a graviton?.
          And isn’t a gravitational field more likely than bent space because two different explanations for micro and macro gravity seem inconsistent. I’m trying to understand, not.argue.

          • Alone: bad. Friend: good!

            Get a blackboard and make a diagram of a “force carrier” and think about it (although you already have done that) and you will see the stuff they say is completely impossible.

            The best example is gluons and color charge, I don’t see how anyone can actually believe it…

            They say red, blue and green quarks are shooting anti-green, anti-blue and anti-red gluons at anti-quarks and changing the color charges so that the color charge is conserved. That stuff just has to be correct!



            NOTE: It doesn’t matter how they explain “color charge”. The point is they think there are 3 different things inside a proton (or neutron) and they are held together in a specific arrangement. If you can think about it in depth you will realize that is completely impossible.
            The explanation (they give) is the only way to explain an incorrect model. But the model and the explanation are both impossible.
            And if you have an incorrect model and an incorrect explanation you can call it counterintuitive — that’s a way to allow anything, even magic.

            How do 3 quarks know that is the correct number for a proton / neutron?
            Why do not 4 quarks combine?
            Is there an instruction set / manual at that level specifically for particles?
            No! …everything has to be automatic.
            Think about it, how do quarks know to only combine in groups of three?
            The answer is… they don’t, the mainstream quark model is incorrect

            • Don Lincoln

              I am sorry, but I strongly disagree with you. The proton has three quarks because there are three colors that sum together to make a color neutral object. If we had four quarks, we’d have a colored object and that would cause enough energy that quark/antiquark pairs would spontaneously produce until a connection with another system would remove the net color.

              The effect you criticize is well understood and poses no conceptual difficulties.

            • Alone: bad. Friend: good!

              So, you believe quarks are shooting gluons at other quarks?

            • Don Lincoln

              My unrefined answer is “yes.”

              My refined answer is that in quantum field theory that excitations in the quark field can excite the gluon field, which can subsequently excite other quark fields. It is through the interaction of these intermediary fields that subatomic particles interact.

            • Alone: bad. Friend: good!

              It blows my mind that people actually believe stuff like that.

            • Don Lincoln

              It blows the mind of a subset of humanity that people actually believe in evolution. Yet evolution is clearly real. Having one’s mind blown is not an indictment of a theory that describes phenomena far removed from normal human intuition.
              I respectfully submit that if your mind is blown, then you do not understand the model, nor the data. The degree of testing is huge and the agreement is high. Were there no testing, it would be wise to be skeptical, but that is not the case in this situation. Your skepticism will have to address the agreement and point to places where the existing model and your model disagree. Scientists would then test the two predictions and the data would determine the superior theory.

            • SS

              Don, I am so impressed by your answers. I wish I was so patient with people who think they know everything by simply surfing google.

            • Don Lincoln

              I have teenagers. You learn to talk to people who think they know everything.

            • Alone: bad. Friend: good!

              Coool… how about answering the question about gluons…

              None of that stuff can be true.
              Gluons and quarks will not work like they say.

            • ben

              I have no model for gravitons but do have a deterministic lego-like model for elementary particles including the gluons. See

            • Alone: bad. Friend: good!

              I admire the amount of work you put into that.

              Here is a question: You talk about charge, what is the difference between something that is charged and something that is not charged?

              You can pick anything you like.
              If you charge something what has happened to it?

            • ben

              In my model all elementary particles are made of preons which are made of hexarks. Every hexark has an electric charge. Aggregated bodies have a net charge which is obtained by simple adding of the charges on the hexarks they contain.

            • Alone: bad. Friend: good!

              ok… cool, you pick hexarks.

              If you have one hexark that is charged and one that is not charged, what is the difference?

              If a hexark loses its charge what exactly did it lose… some kind of gas or fluid? What exactly is the charge?

            • ben

              All hexarks are charged. In my model, either -1/48 or +1/48. These are structural properties which don’t change. They can’t lose or gain charge. Aggregate bodies can have a mix of + and -.

            • Alone: bad. Friend: good!

              If they cannot lose or gain they are the equivalent of inert and incapable of doing anything.

              NOTE: you still have absolutely not explained what charge is and now you have positive and negative charges..

            • ben

              Yes, that’s right. They are inert or unchangable. However, they can be arranged into aggregated structures in a lego-like model. So one can do things with them. I can’t explain charge but my vixra paper shows that negative charge is directly related to hexark colour while positive charge is related to hexark anticolour. Quark colours derive from hexark colours but not in a completely straightforward way. Hexark colours are not explainable in terms of other qualites.

            • Alone: bad. Friend: good!

              When they are arranged in a structure how do they hold together?

              EXAMPLE ANSWER FOR LEGO: “Most Lego pieces have two basic components — studs on top and tubes on the inside. A brick’s studs are slightly bigger than the space between the tubes and the walls. When you press the bricks together, the studs push the walls out and the tubes in.”

              How do your structures hold together?

            • Alone: bad. Friend: good!

              Don’t worry if you cannot explain something.
              Mainstream doesn’t have anything actually explained.

            • Alone: bad. Friend: good!

              I did not get the stuff I know from surfing google.
              Most of mainstream physics is incorrect and it is easy for me to see — you don’t get that from google.
              You are a simpleton that mixes things up and has no logic.
              You are part of the problem.

            • Don Lincoln

              I am not a simpleton. My mom had me tested

            • Alone: bad. Friend: good!

              I didn’t call you a simpleton. That was the other guy. See how you mixed that up? Most of mainstream physics is like that.

            • Don Lincoln

              I didn’t say that you did. I was just clarifying that my test came back negative.

              See how you misinterpreted what I said? Most criticism of mainstream science is like that.

            • Alone: bad. Friend: good!

              Sorry good buddy, your test actually came back positive.

              They just didn’t want to hurt your feelings so they told you negative.
              You should have figured that one out a long, long time ago.

              Why did they get you tested in the first place? Because they knew something was wrong.

            • Alone: bad. Friend: good!

              “quark/antiquark pairs would spontaneously produce”

              Spontaneously produce out of what?
              Out of Nothing?
              If so that is a “magic” explanation and it’s impossible to argue with someone that believes in magic.

            • Don Lincoln

              I believe that I have thought about this in depth. The study of this question began with my doctorate in particle physics and the conclusion has not changed over the last 30 years.

              It seems that you are offended by the “something appears from nothing” assertion, but this is seen in more areas that color physics. For instance, photons can spontaneously produce an electron/positron pair. This ias been seen countless times and further studies of things like tha magnetic moment of the electron or muon have been calculated and measured to 12 decimals with excellent agreement. The calculations are predicated on the idea of this spontaneous creation and annihilation. Any time that you can calculate something that accurately (indeed, this is the most accurate calculation ever performed by mankind), means that you are on the right track.

              The way to think of this is to realize that energy exists in the form of (for example) vibrations in a photon field. This vibration excites the electron field, vibrating it in such a way that a electron vibration is set up, and also an antielectron vibration.
              If you point to energy conservation, then I remind you of the Heisenberg uncertainty principle, which postulates that energy non-conservation is allowed if the non-conservation duration is sufficiently short. This seems non-intuitive, but it has been demonstrated many times in many situations. Like it or not, the world works that way.
              You are, of course, free to disagree. However you will then need to demonstrate how hundreds of experts in particle physics are somehow too clueless to agree with your statements.

            • Alone: bad. Friend: good!

              Get a blackboard and make a diagram of quarks and what everyone thinks they are doing then think about it for a couple of months if you have to.

              There are no experts. Everyone is just making guesses and a lot of them are horrible. Some things are almost correct but not many.

              Most things are built upon an incorrect model. It’s no ones fault. There have been a lot of incorrect models from supposed experts… like plum pudding model for example. It’s all just guesses.

              A lot of people have a vested interest in keeping things the way they are now. Even if aliens landed with their physics books that showed the true way things work… the “experts” would still fight and deny it.

              Do you understand… people actually believed the plum pudding model…

            • Don Lincoln

              Scientists also killed the Plum Pudding model. That’s because the data was inconsistent with it.

              For QCD, with which you seem to have some difficulty, the agreement between the conceptual idea, the detailed mathematics and the formidable amount of data is impressive. In the Plum Pudding case, there simply was no data.

              The situation is always thus. When there is no data, many models can exist. However, once relevant data is obtained, some models persist and some die. QCD might be replaced by a better model one day, but the new model will look very much like QCD, with the gluons jumping back and forth. That part is strongly confirmed.

          • Don Lincoln

            Most scientists think that a graviton is probable, however science isn’t a matter of opinion. Until we detect one, we won’t know.

            It is clearly true that in the macro realm that gravity bends space, however a correct theory will work in both the micro and macro realm. In the same way that the quantum probability morphs into the classical determinism, the microgravity will have to morph seemelessly into macrogravity.

    • Andriod Khan

      Can a black hole destroy gravity

      • Don Lincoln


    • science lover

      What if we think that every body releases energy and the energy covers the body.when another body comes to its energy field the energies of the two bodies interact together to form gravity…………….its just my thinking.I may be wrong¤¤¤¤¤

      • Nana

        Sorry, You are wrong.

    • G

      Do gravitons exist outside of galaxies, for example, within intergalactic space or the “voids” between them?

    • G

      Do Gravitons exist outside of galaxies, for example, in intergalactic space or the “voids” in between them?

      • Don Lincoln

        Gravitons are thought to exist whereever there are gravitational fields, thus, to all intents and purposes, gravitons are everywhere.

      • Proton

        In the void there are no particles…

    • AiyaOba

      Don Lincoln, your humility exemplifies the mind of a true giant.-Aiya-Oba (Philosopher).

      • Don Lincoln

        Well thank you.

        • AiyaOba

          I am honored.

    • Kierra Sinclair

      I think we’re looking the wrong way. We should be looking for what pushes an object towards a large object rather than what pulls it.

      • Proton

        The black hole is smaller than an atom of hydrogenium but it can pull a giant planet.
        Think a little before you say something…

        • Snickster

          On the contrary let’s maintain an open discussion free of intellectual bullies seeking to stymie the conversation. If you disagree, say so without being so offensively condescending.

          • MCMisterP

            “We should be looking for…” is a strong statement, not just an inquiry or idea worth mentioning. If Kierra is going to be so suggestive in an incorrect declaration, they should be stymied. Proton is right, original poster should think a little before stating fallacies that might influence comment readers. Some people are more straightforward (Proton) than others, but that doesn’t make them a bully.

    • flamestar

      Gravitons can’t escape from a black hole but changes in space time can, Einstein is right.

    • carlpet

      but how do you twerk

      • Boss Ross

        hobbit this is science go away

      • Don Lincoln

        Very badly.

    • the hobbit

      My milkshake brings all the boys to the yard

      • carlpet

        hobbit this is science go away

    • WXGT

      sir can i ask does photon is anti particle or has anti particle sorry im not good at science

      • Don Lincoln

        Photons are their own antiparticle. It’s analogous to the idea that there is a +/-1 and +/-2, but +/-0 is just 0.

    • Mike P

      one more convienient uni-tasker particle that doesn’t provide a better reason that gravity exists.

    • Atharva T.

      Hi Dr. Lincoln or anyone else who cares to answer my few questions,

      I am just a highschool student so some of your terms confused me as well as some of your ideas so I have a few questions

      What is a spin? I know that different particles have a different spin even electrons and protons have a spin but what is it and what does the phrase a “spin of two” mean especially when compared to the spin of other particles.

      I do not understand why a graviton must exist for if gravity as Einstein said, is just a warp in space in time why do gravitons need to exist for gravity to occur?

      If Gravitons are supposed to travel at the speed of light, and are weightless but contain a bunch of energy wouldn’t that mean that just like photons gravitons are attracted by gravity, but once again would that not be a bit paradoxical?

      I also understand that gravitons might be mostly in other dimensions but why does that affect our measuring ability is it not still in our universe and still affecting us even if it is in another dimension?

      How are gravitons emitted?

      How do gravitons push us toward the thing attracted us?

      any answers will be greatly appreciated!

      • Don Lincoln


        Sorry for the tardy response, but I was giving lectures in a place with no internet access.

        Spin is an intrinsic angular momentum. You can think of it as ordinary spin, but this is not right when considered in detail. It’s more like a “charge of spin.” In the same way that an electron comes with a certain amount of charge, it comes with a certain amount of angular momentum. The electron comes with the amount hbar/2 (or Planck’s constant (h) divided by 4 pi). We say that an electron thus has a spin of 1/2 (as the unit hbar, or h over 2 pi is the unit of subatomic spin.) Photons and gluons have one units of spin. Gravitons have 2 units of spin.

        Gravitons must exist if gravity has a quantum nature. The idea of bending space is true on large scales (where large is larger than a proton or so). However, at very small scales, general relativity must fail as a quantum world takes over. Accordingly, when the quantum theory of gravity becomes relevant.

        Gravitons are definitely energy and therefore also contribute to the warping of space. Thus gravitons have a basic attraction to other gravitons.

        • Atharva T.

          If it’s true that gravitons effect other gravitons then how is gravity constant at one location?

          Also could you answer these please

          I also understand that gravitons might be mostly in other dimensions but why does that affect our measuring ability is it not still in our universe and still affecting us even if it is in another dimension?

          How are gravitons emitted?

          How do gravitons push us toward the thing attracted us?

          • Don Lincoln

            Any energy causes spatial distortions…even gravitons. However the gravitons are part of the ongoing gravitational field, so this really doesn’t materially change anything.

            Gravitons are emitted essentially just as photons are. Further they don’t push anything, they cause a pull. (Yes, that is a bit tricky to see, but it’s really no different than how photons cause attractive forces.
            Gravitons are most likely only in our familiar three dimensions postulate that other dimensions might exist, this is only a supposition and not one you should take seriously without experimental proof. This has been lacking.

        • sar

          What if gravity doesnt apply to quantum world?
          If mass can bend space time does it ever ocvur to u guys that at certain point too small amount of mass cannot bend spacetime?

        • Punyashil Shahare

          Sir, if graviton and antigraviton particles are the same, then what differentiates them.? How can we say that gravitons have any antiparticles..?? Same for the photons.Please give a response. Thank you.

          • Don Lincoln

            It’s like +0 and -0. They are both zero. Zero is the only number fir which this is true. Photons are loke that. Ditto gravitons.

      • abrogard

        I am totally non-technical and usually floundering in the seas of the explanations the technical give us. Such as the one Don Lincoln has supplied for this question.

        I’d like to insert what I recently saw. It worked for me.

        A talk/web graphics demonstration that when you send a charged particle through a magnetic field it will be moved off course by that field.

        We’re talking an ‘asymmetric’ field here. One deliberately stronger at one pole than the other. Made by clever design of the magnet.

        Start by thinking of sending a stream of tiny bar magnets through the field. Easy way to visualise it. Depending on how the bar magnets are oriented they will be differently moved by the field.

        A completely random stream of tiny magnets will be oriented in completely random fashion so will be ‘moved’ in random ways and will reach the other end of the track and come out of the magnetic field randomly dispersed across the detector plate or whatever.

        So you would expect a random stream of particles to do the same thing.

        But it is found they come out the other end and make only two blobs, two points of landing, two aiming spots or whatever. One ‘up’ the page and the other ‘down’. 50% each.

        Those that go ‘up’ have become known as having ‘spin up’ and those that go down have become known as having ‘spin down’.

        And when they are entangled, two of them, one must be up and one must be down.

        And when two electrons occupy a valence position there must be one up and one down. They can’t both be up or both be down at that energy level.

        Don Lincoln’s explanation is technically precise, detailed and doubtless totally accurate.

        And almost meaningless to me. That above explanation satisfies me as a point to start from so’s I know what I’m talking about and so’s I can then move forward and gather more detailed information about the subject if I wish.

        I hope it proves useful for some others. And I’m sorry I lost the url or I’d provide it.

    • Jeff

      Remember this, Black holes and Dark matter are fillers for when the math in the gravity model fails.

      • Don Lincoln

        That might once have been true, but the two ideas are becoming increasingly plausible.

    • Tommy Elumbaugh

      Photons are said to bend around objects with great mass, such as hypothetical black holes, this would mean that they would have to have some mass to be affected by a virtual field called gravity. So what if gravity is caused by nearly pure mass that generates some energy in the form of a gravitational field, and photons are nearly pure energy that emits some mass? Directionally, photons disperse and gravitons compact or have an inward direction. So in theory they are opposites. According to Einsteins Conservation of mass theory energy can be converted to mass and mass can be converted to energy. Just playing around with ideas.

      • Don Lincoln
        • Hugh

          Wow! That was illuminating. Seriously though, I had not though about Einsteins equation of E=Mc2 in relation to mass being generated Energy of the particles in the Atom. Brilliant!

      • Nana

        The photon bends because the space is bent, not because there is a force “pulling or pushing” it.
        Gravity bends space and the photon travels straight through the bent space.

    • morbas

      One other graviton theory is Aspin Bubbles, short for Anaharmic
      Spin I surmise. This theory “suggests that electrical
      forces among singly charged elementary particles are simply
      mechanical forces coming from a single mechanical interaction between
      anharmonic waves and particle” [“aspin Bubbles” and
      the Force of Gravity: Yoel Lana-Renault; Infinite Energy Vol 20 Issue
      115 2014]. Explains gravity outside of any Time Dimension. Time
      dimension is fundamental to General Relativity (and BB).

      Related to the BB I would suggest Hilton Ratcliffe ‘The Static
      Universe’ to any students as an antidote to High School and
      University BB indoctrination. The falsity of the BB is in the total
      absence of any astrophysics supporting the BB. Also, Hubble Red shift
      has been abandoned by BB theory as portraying any Universe Expansion,
      as Hubble claimed as well.

      IMHO Morbas

    • Ran

      “Like massless photons, gravitons should travel at the speed of light. ” Why this assumption? Where did that come from?

      • Nana

        “No mass” means you are traveling at light speed. “Mass” means you are traveling at less than light speed.
        The gravitons should decay very quickly if they are traveling slower than light speed.
        If the graviton has no mass, then light speed it is.

    • Anil

      A magnet will hold a paperclip against the Earth’s gravity.

      “There are other gravitational force which are acting against earth’s gravity (Like moon, sun, other planets and even stars) that is why it appears weak.”

      • Nana

        Sorry, that is wrong.

      • Nana

        Sorry, that is wrong.

    • Nana

      I’m a little late to the party.
      This is a great article. It has given me a new way to think of gravity.
      Thank you Dr.

    • pablo

      I think once you travel at speed of light immediately you reach other dimensions, so it the Gavriton travels the speed of light then gravity is reaching other dimensions, now the question is why? What if gravity is able to carry information, that has to do with our human and planetary reactions towards it, an on off mechanism. Then that would make the world a very strange place. :).

    • Shawn Loney Dahn

      This may seem dumb, when spinning the particle in a collider does it not create gravity. And if you could rid the particle of gravity could it be faster than light?

    • AiyaOba

      Dr. Lincoln, if gravity complements radiation in the singularity of Cosmos, gravity has to be absolute, meaning the non-quantizing aspect of space. -Aiya-Oba (Philosopher).

      • Don Lincoln

        I do not see the consistency of this logic. But, then again, I suspect that you are using words in non-conventional ways.

        Even if gravity complements radiation (without understanding what that means), it has no bearing on the quantum nature of space. After all, if the two phenomena complement one another, they probably originate in a deeper and more inclusive concept.

        • AiyaOba

          Thank you very much, yes, that very ‘deeper and more inclusive logic,’ is the absolute ( new physics ) unity of infinity state of Nature, yet to be explore in cosmology. Gravity complements and contradicts Radiation in the unity of Space, which explains why there seems to be more ordinary matter than anti-matter, as in the numerical relations:
          -122 + 123 = 1.
          123 + 321 = 444.
          1×10^-9 x 9.999999999×10^8 = 1. Again thank you.

          • AiyaOba

            Cosmos (absolute reality) is simultaneously absolute and relative, as absolute oneness of relative pairness, equator of self-contradiction, absolute nonlocality of the relative locality of spacetime.
            Which is how quarks bind strongly together neutron and proton inside the nucleon of an atom, by means of the resultant( gluon) attractive force out of their own relative self-contradiction configurations into Tetraquark (unity of self-contradiction (Pair) of isosceles triangles which forms a square, whose single diagonal is the equator and single-pair base of the isosceles triangle within the square).
            It forms their absolute unity and glue, as atomic nucleus.
            2d + u (neutron) + 2u + d (proton) = 3(d + u) -tetraquark + single -pair diagonal of the square quark.

            where d, is down quark, and u, is up quark.-Aiya-Oba (Philosopher).

    • Alone: bad. Friend: good!


      Everyone has the wrong idea of what energy, forces and fields are.
      Energy is a particle vibration or movement.
      You cannot have energy without a mass, energy is mass vibrating.
      Energy cannot be out on its own. (a supposed mass-less particle is a particle nonetheless, but there are no mass-less particles, so that’s irrelevant)

      Same thing goes for forces.
      A force is a group of particles arranged in a field pulling each other… and all of the particles absolutely have to be physically connected.

      A force (a group of connected particles) can only push very short distances and in rare circumstances like same pole magnets.

      But the point is… a force has to have particles involved.
      A force cannot be out on its own.

      Most of mainstream physics is a misconception.

      There is no such thing as pure energy.
      Again… Energy is a vibration on a particle (or particle movement).

      Can energy be converted into mass?
      Ummm… no, energy already has mass involved, it is a particle vibration or movement. There is no pure energy and you are not going to convert energy into mass.

      Think of a guitar string. If you pluck it… that is the energy. If you remove the guitar string from the scenario… can you still have the energy? No, of course not.

      Can you convert the guitar string vibration into mass? No… that is ridiculous.

      Look at what everything really is…

      Dimensions and units…
      mass = [M] = kilograms
      length = [L] = meters
      time = [T] = seconds
      frequency = [T^-1] = seconds ^-1
      speed = [L] / [T] …… = m/s
      acceleration = [L] / [T^2] …. = m / s^2
      momentum = [M] [L] / [T] … = kg_m / s
      force = [M] [L] / [T^2] . = kg_m / s^2
      energy = [M] [L^2] / [T^2] = kg_m^2 / s^2

      Notice mass [M] is not equal to energy [M] [L^2] / [T^2] …the vibration is missing

      Here is what Einsteins famous equation really looks like…

      [M] [L^2] / [T^2] = [M] [L^2] / [T^2]

      Energy already is a mass times speed^2.

      How would you go about converting a mass times speed^2 into a mass times speed^2.

    • Alone: bad. Friend: good!

      “When there is no data, many models can exist.” — sorry, many models can and do exist even with data. There can even be a completely incorrect model that explains the data correctly (other things would give away the fact the model is ridiculous but they will just be ignored).

      “gluons jumping back and forth is strongly confirmed” — that is nonsense. But if that were actually true you would be able to explain what everything looks like.

      What does a gluon look like?
      (you don’t have to be exact. Just magnify the gluon until it is the size of a beach-ball and explain what it looks like. It cannot be point-like / spherical, a sphere can’t hold stuff together. Quarks also cannot be point-like)

      Yes, math is great but you could have two people with completely opposite / opposing theories. The maths for both (theories) could be peered reviewed and deemed absolutely stinkin’ correct.
      But only one of the theories can be correct so that means one of the theories must be wrong.

      They actually both might be wrong.

      So if you prove something with math you actually DID NOT prove or disprove anything.

      • Don Lincoln

        Gluons, like quarks, are quantized vibrations in the underlying field. The quantization makes apt the use of the word particle. It is a localized vibration. And, yes, they do jump back and forth.

        • Alone: bad. Friend: good!

          What is the underlying field made out of… magic?

          You will never be able to give a straight answer because the model on almost everything is wrong.

          • Don Lincoln

            You are, of course, welcome to your opinion. However, the standard model has excellent, if incomplete, predictive powers. Within its realm of applicability, which includes quarks and gluons, it is a reasonably accurate description of reality.

            The underlying field is not made of magic. We tried that, but the rabbit fur and dove feathers got into everything. And the beautiful assistants kept distracting the graduate students.

        • Alone: bad. Friend: good!

          Vibrations DO NOT hold things together.
          Think about it o.k.?
          Get two things that are vibrating and put them together and see what happens. (you don’t even need to do that, you already know what will happen)

          Mainstream physics is not only wrong… a lot of it is backwards.

          • Don Lincoln

            Nonetheless, electrons are oscillating constructs. We see this in the interference patterns they generate. There is no other known mechanism for generating interference patterns.

    • disqus_S1cyTrMPQ4

      What if Gravitons and photons were the same but just like the neutrinos they can manage to show more of one flavor and less of the other through a different mechanism (more complex)

      • Don Lincoln

        Well, keep in mind that gravitons interact with mass and photons interact with charge. Your hypothesis would inextricably link mass and charge. Since mass and charge seem to be independent, this may falsify your theory.

        • disqus_S1cyTrMPQ4

          Could there be a different oscillation mechanism for the bosons. In that mechanism instead of changing the leptonic charge , the boson changes it ability to interact through mass instead of elec. charge. ?

      • Alone: bad. Friend: good!

        “What if Gravitons and photons were the same?” — yes, they just about are they same. They are both supposed massless particles traveling at the speed of light and they are shooting (or jumping) back and forth between matter.

        The difference is… one would be holding matter together and the other would be holding electrons in their orbitals and also giving us what we call light. That means the massless particles are traveling through space and holding a specific frequency and or wave at the same time.
        So I guess the photon is actually doing both by itself (holding something in place (actually at a specific distance like a star trek tractor beam) and basis for light).

        I like to think of them as computerized magic.

    • anonymous

      Hey guys listen up i have a crazy idea in my mind .This article says that a graviton must move at the speed of light (the only way for it to exit is that it has precisely zero mass and a spin of 2) so we should take an object and displace it from its position such that we are escape the gravitational field exerted buy that object now we should measure the time that object takes to attact body B in its field (i.e the time taken by the object after displacement to exert a force on body B) .Then calculate speed of that force if ut is equal to speed of light then gravitons are for sure real it the force has a speed greater than if slower relative to speed of light then graviton does not exist.

    • Alone: bad. Friend: good!

      The reason they will NOT find a graviton is because it is another ridiculous idea.

      A supposed graviton is a massless particle traveling at the speed of light?
      The massless gravitons are jumping back and forth between the matter they are pulling together? How could anyone believe that?

      Then again, they could find it the same way they found the Higgs — guess the weight, just keep smashing protons until you get shrapnel of the weight you were looking for and that means you found the Higgs.

      They get shrapnel of a certain weight so that means it is what is giving mass to other particles — except if it is photons or gravitons and they are massless… then the Higgs is NOT interacting with them. (you can correctly extrapolate a multitude of properties just from weight)

      Stuff at a basic quantum level “knows” how to do a plethora of functions

    • Alone: bad. Friend: good!

      “A new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die, and a new generation grows up that is familiar with it.” — Max Planck

      Yup… it’s going to take more than a hundred years before the truth is known.
      We will all be long dead.

    • Norman DeLue

      It appears gravitons must emanate from a mass to cause the effect of gravity. If nothing can escape from a black hole, how come they have gravity?

      • Don Lincoln

        Gravitons don’t actually emanate from the point-like source in the center of the black hole. They emanate from the energy of the gravitational field. This is much like virtual photons emanate from a charged object.

        As you get closer to the particle that looks much like a singularity, you find that it is surrounded by a tempest of subatomic particles that originate in a mixture of the gravitational force and quantum mechanics.

        Remember that once you are outside the event horizon of a black hole, it really isn’t different than any other matter. If you took a hypothetical black hole the size of our sun and put it in the sun’s location, the Earth and all the planets would continue to orbit. The only difference is that it would then be dark.