How do Gravitons work? as compared to photons

Question

Photons are to Electrons as Gravitons are to ... what?

What is it that 'emits' a graviton? And what 'absorbs' it?

I've been looking for a good layman's description of how gravitons interact with ... things ... and have been unable to find one. The closest I've got is this boat and brick example. Which is good, as far as it goes. But has obvious flaws (negative momentum particle? the layman was following along great, to that point).

I'm hoping for something more like:

"When an electron in a higher-than-normal orbit falls back to its normal orbit, it emits a photon, a packet of energy, which carries that energy through space at the speed of light until it encounters another electron which absorbs it, causing the electron to move to a higher-than-normal orbit"

But for Gravitons:

"When a ____[electron substitute for gravitons] is in a ____ [state or action replacing the orbit change of electrons], it emits a Graviton, a packet of ____ [would it still be energy, or something else?], which carries that Gravity(?) through space at the speed of light until it encounters another _____[?] which absorbs it..."

How does an individual graviton work, in this type of description?

Answer 1

As long as you appreciate these are all deeply flawed "lies to children" mental pictures, and need not "represent" a consistent "story"...

Nothing of these things happen, or even remotely so, any more than a snake biting its tail represents cyclic organic compounds (another celebrated dream metaphor).

The brick thrown from boat to boat metaphor asks you to suspend your disbelief when the brick traveling from boat to boat sucks momentum from the recipient (absorber) boat and pulls it towards the emitter boat. This does not happen in conventional mechanics that you have build intuition for, but in quantum mechanics, a deeply counterintuitive theory, where you mostly follow the math.

Such pictures, including terms like photons or gravitons, are cartoon mnemonics for well-understood and applied calculational recipes: they are shorthand for mathematical expressions in perturbation theory, a calculational technique that yields good answers. Highly perceptive people have often been led astray by them.

In electromagnetism, two magnets emit and absorb gazillions of low energy virtual photons at and from each other, resulting in a mutual attraction (if they are aligned properly).

In quantum gravity, a speculative/hypothetical type of theory, an apple and the earth emit and absorb gagillions of "soft" gravitons at and from each other, creating a mutual attraction, classically understood as gravitational field attraction. Repulsion is not possible here.

In electromagnetism, (quantum) atomic transitions are described by photons than by emissions and absorption of classical electromagnetic waves.

In gravity, microscopic quantum phenomena are not observable directly (or have been observed), so you observe gravitational classical fields from and to everything that has energy (including light, and photons) or mass; or classical gravitational waves from fast-moving massive black hole or neutron star binaries, etc.

Because (in some highly technical way outranging our scope here) gravity is "weak", in comparison, it is freakishly hard/impossible to observe the type of quantum microscopic transition you are envisioning. So your pre-fab paragraph needs heavy deconstructive revision,

• When a mass or clump of energy is in any state, it emits an indefinite number of real or virtual gravitons, packets of energy and momentum which thus carry that Gravity through space at the speed of light until it encounters another clump, spaceship, nebula, or photon which absorbs it, picking up the energy and momentum transferred.

however, I'm not quite sure what you were going to do with that picture. Unlike real photons which are routinely observable in the lab by several gadgets and techniques, single gravitons are not even remotely observable; F Dyson is famous for having doggedly sought a proof for this.

When theorists yap breathlessly about gravitons, they involve them in elaborate quantum calculations which might contribute to indirect shifts of recondite quantities possibly providing "smoking guns" for their (the gravitons') existence.

But it is quite hard to develop intuition on something unobserved and arguably disconnected from observable phenomena.

Answer 2

In the analogy between photons and gravitons, (real) photons make up electromagnetic waves such as light and radio waves; and (real) gravitons make up gravitational waves such as are detected at LIGO. Just as photons are emitted by accelerating charges, gravitons are emitted by accelerating masses, at least in principle. In practice we do not have a complete quantum theory of gravity, so the details of which masses emit gravitons and under which circumstances are still somewhat hazy. But clearly if gravitons exist, large masses like neutron stars and black holes can emit them -- we can directly detect gravitational waves from such objects.

Answer 3

I have come up with a rather speculative theory that explains what you are looking for in a slightly different way.

Under Newton, gravity was an attraction between bodies (say planets), so there was a search for a particle emitted by one planet that attracted another planet. But this idea changed under General Relativity where we now say that gravity is caused by the warping of spacetime. You could say that gravity IS the warping of spacetime. Because a single planet can cause the warping of spacetime, gravity does not require two planets, just one. So the question becomes, what is it inside a planet that would cause the warping of spacetime?

We know that this warping is caused by "mass". But what is mass? A planet made of tin has less gravity than a planet made of lead, even if they both have the same size and same number of atoms inside. So we must look deeper into what is inside those atoms. We have protons, neutrons and electrons. And the protons and neutrons are made up of quarks and gluons. A planet made of lead has more quarks, gluons and electrons than a planet made of tin. So we are left with the choice of quarks, gluons and electrons as potential sources for this warping.

Scientists have told us that in the first fraction of a second after the big bang, there was only quarks, gluons and gravity; that's it. There were no electrons, so I think they can be eliminated from contention.

We know that a simple bar magnet works because the spin of the electrons inside that magnet generates a magnetic field outside of the magnet. I contend that gravity works in a similar way, but it is the spin of gluons inside the planet that generates this field surrounding the planet.

Now comes the interesting part. There is a theory known as Loop Quantum Gravity. In this theory, space itself is particulate. Scientists have told us that energy causes a warping or distortion of these tiny particles of space. My theory holds that energy, as in the energy of the excited gluon field surrounding a planet, actually causes a dilation (or swelling) of this particulate space. We could call this the warping of space.

As a further step, I believe that it is this particulate space that defines the speed of time. That is, light must travel between these particles. Therefore, if these particles are dilated then light, and thus time, travels more slowly. So the dilation of these particles is in fact a warping of space and time, or spacetime.

So in the end, the particles that you are thinking are called gravitons are actually gluons, which we know exist. It is the spin of these gluons that leads to gravity.

You can read my paper here. All of the references are inside. I believe that this answers your questions about the behavior of gravitons (i.e. gluons) to create gravity. Have fun.