# Thread: Why do we predict a graviton?

1. ## Why do we predict a graviton?

why do we predict a gravitron and what do we predict about its properties?

2. Originally Posted by tommac
why do we predict a gravitron and what do we predict about its properties?
I don't know anybody who predicts a gravitron. However, a graviton is conjectured because the other three known forces are well explained with these 'force-carrying particles' or bosons. It should be noted all interactions are also well explained with field theories.

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Originally Posted by tommac
why do we predict a gravitron and what do we predict about its properties?
No expert but here's my two cents:

We predict force carriers to be associated with forces and there is a time delay that occurs over distances for a force to be detected. One way that is detected is by measuring the wave fronts of a force and another is by measuring exchange of its exchange particles, the latter which are usually inferred. Exchange particles exist for the other fundamental forces and so it is predicted that the force of gravity has one as well.

Yet, according to Newton 3rd Law, forces must come in pairs and gravity does not come with some associated pair. Dark energy, if validated in the future, is not a real candidate because it does not have the property of weakening with distance by the inverse square law. It is proposed to provide a density that does not change with spatial expansion. So, to many, gravity is not really a force but is a geometry of pathways for inertial masses to float toward other inertial masses.

The properties of the graviton seem unanswered until some unity between quantum gravity and GR is resolved both on paper and in experiment. We can derive some properties by studying how the tidal forces squeeze and stretch inertial bodies but we likely need a better grasp on its quantum behavior of gravity before proceeding.

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You predict a gravitron when you've been watching too much transformers.

A graviton(no R) would be a massless spin 2 boson. The biggest problem is figuring out if it is background dependent or independent. That means does it jive with relativity or not?

One theoretical calculation says a detector the mass of Jupiter around a typical neutron star would be lucky to see a graviton every 10 years. If you ask me, there are no immediate plans to detect a graviton using this method.

If we could prove a particle for gravity, we'd be one step closer to unifying the laws of the cosmos.

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## making a few waves...

Originally Posted by blueshift
SNIPPET...
Yet, according to Newton 3rd Law, forces must come in pairs and gravity does not come with some associated pair. SNIPPET
blueshift. Gravity as modeled in Newton's Law...Fg = G m1m2/ d2, is a mirror force between two objects, with the strength being equal in magnitude and opposite in direction, and as such satisfies Newton's Third, No? No second object, no observed force.

Originally Posted by blueshift
SNIPPET So, to many, gravity is not really a force but is a geometry of pathways for inertial masses to float toward other inertial masses.

The properties of the graviton seem unanswered until some unity between quantum gravity and GR is resolved both on paper and in experiment. SNIPPET
And to some, the geometry of Minkowski space-time that is distorted by the presence of rest/inertial mass is matched topologically by an equal geometrical distortion of the ambient neutrino sea.
The properties of the graviton were first elucidated by George Gamow in the Project Physics Reader,"Gravity"...." an antineutrino/neutrino pair has the correct quantum properties for a graviton", integral spin, travels at c, massless(the putative neutrino mass experiments as yet have provided only upper bounds, Particle Data Group) and the WIKI take has the velocity a tad over c, but c within experimental limits, as does the coincidence data from SN1987a).
The experimental resolution was the SN1987a coincidences with the gravitational waves seen at the Maryland and Rome sapphire bar observatories during in Feb. 1987, and successfully predicted in April 1982 by yours truly. Said coincidences were published ~ 20 times in a variety of peer-reviewed journals by a dozen or so physicists. See also:http://www.bautforum.com/space-astro...d-light-2.html

pete
Last edited by trinitree88; 2009-Jun-15 at 05:49 PM. Reason: double trouble

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Originally Posted by alainprice
One theoretical calculation says a detector the mass of Jupiter around a typical neutron star would be lucky to see a graviton every 10 years. If you ask me, there are no immediate plans to detect a graviton using this method.
If gravitons were so difficult to detect, how could they possibly be so good at mediating gravity?

I mean, wouldn't the fact of this detector's continued stable orbit around the star indicate that it was in some way "detecting" gravitons constantly?

Or is the idea that a single graviton mediates so much gravity that a single interaction will keep a Jupiter-sized mass on its orbital track for at least another ten years?

7. Originally Posted by stutefish
Or is the idea that a single graviton mediates so much gravity that a single interaction will keep a Jupiter-sized mass on its orbital track for at least another ten years?
I believe it's the opposite problem-- the amount of gravity mediated by a single graviton is so tiny that it is hard to see the quanta. Note we can detect a single photon with modern CCDs, so the quantization of the E&M field is experimentally verified, it does better than just explain the photoelectric effect.

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If your orbit is a perfect circle, detection of a graviton is detection of non-circular orbit. It may average a circular orbit, but there would be blips along the way.

As it stands, even in a particle accelerator, the influence of each graviton event is so small that we cannot detect these 'test particle jumps'. It's like saying if a breeze can blow a leaf, why can't we detect each individual air molecule interaction. The answer, the interactions are just too small to measure directly. A stable orbit only reinforces Einstein's theories.

There are experiments which seem to imply that gravity is quantized, as seen with ultra cold atoms on earth. The quantization of their movement is along the earth's 'height'.

9. Regarding a graviton does quantized mean binary? Or a set of possible states?

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Yes, quantum means stepped. Like old volume knobs versus the new digital style. The digital style can only have so many 'levels'(usually about 40 or so), whereby an analog one can have infinite 'levels'(infinite choices).

Classical means it can be analog, like following an arrow in flight. If we start thinking of an arrow as existing in one spot and then jumping to the next spot, no matter how small the jump is, our brains don't like that idea much. It just doesn't make sense for big things. At least it doesn't make sense on the surface of it all.

Quantum is like digital, only certain states are allowed. When an electron goes from one level to another in an atom, we think of it as actually 'jumping' with no in between.

Nowadays, the tendency is to lean towards quantum instead of classical, for everything and anything. Some people like to think that even a photon's wavelength could be quantized. I'll wait until the jury's out.

11. Originally Posted by alainprice
Some people like to think that even a photon's wavelength could be quantized. I'll wait until the jury's out.
I would assume that it would have to be ... otherwise the double slit experiment wouldnt work?

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Then you assume that Einstein is plain wrong.

Special relativity is NOT quantized. The double slit experiment says nothing about a photon's wavelength.

Again, it's too early for me to say if I subscribe to either camp.

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[QUOTE=trinitree88;1509463]
Originally Posted by blueshift
SNIPPET...
Yet, according to Newton 3rd Law, forces must come in pairs and gravity does not come with some associated pair. SNIPPET

blueshift. Gravity as modeled in Newton's Law...Fg = G m1m2/ d2, is a mirror force between two objects, with the strength being equal in magnitude and opposite in direction, and as such satisfies Newton's Third, No? No second object, no observed force.

pete
You have a second object but you have that with all forces. The electrical force comes in pairs because two like charges can repel as well as attract. The nuclear force comes in pairs because there is both fission and fusion of nuclei. We have pushes and pulls in physics but gravity is not paired with a force that has two free floating bodies on a collision course with a planet that are repelled across the planet's shared gravitational field. If there is a force that pairs with gravity then two uncharged bodies moving directly at one another should be seen in the universe that are repelled on the macro-sized world. Something in our labs should be falling "up" and moving away from other masses and it should be done without any forces attached to it, such as a rocket. We should see globular clusters with stars that are separating from one another, forming them into open clusters and we should see galaxies coming apart with stars flying in random directions. We should also see moons such as our own that leave orbits they have been in for centuries without any collisions from third party intervening forces such as a supernova or some very large massive collision with a planet-sized body taking place.

So for forces to exist one needs the act of objects that are pulling together paired with a force that causes their pushing apart from one another. Gravity doesn't cut it.
Last edited by blueshift; 2009-Jun-16 at 02:26 AM. Reason: spelling

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Originally Posted by tommac
Regarding a graviton does quantized mean binary? Or a set of possible states?
Quantized never means "binary". Quantized simply means that things are not infinitely divisible. They come in discreet whole parts or packets or energy called "quanta". How far can you subdivide water? Can you go on infinitely and still call it water? Or is there a limit? Once you reach just one molecule of water can you divide it any further and still call it water and wash with it?

A set of possible states does not define quanta either. It merely points to a characteristic of quantum physics at the quantum level.

15. Originally Posted by alainprice
Then you assume that Einstein is plain wrong.

Special relativity is NOT quantized. The double slit experiment says nothing about a photon's wavelength.

Again, it's too early for me to say if I subscribe to either camp.
Well what happens when wavelengths are smaller than the planck length?

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Originally Posted by tommac
Well what happens when wavelengths are smaller than the planck length?
At distances smaller than the Planck length it becomes impossible to determine which event comes prior to another if both events take place within that Planck length of 10^-33 cm. Take that number and divide it by the speed of light and you get roughly 5 x 10^-44 seconds, the shortest amount of time that is possible to measure at all or even conceive of. The uncertainty principle of quantum mechanics prevents any speculation on times shorter than that. Therefore, no wavelength can be shorter because all wavelengths can be measured for a duration.

17. Originally Posted by blueshift
Quantized never means "binary".
I would say it kind of does for Fermions, like electrons, which are particles for which you can only have either 0 or 1 of them in any given state when the number is actualized by experiment. It is true that this also means you cannot subdivide the 1, it is 1 or 0, but that is binary. Perhaps that will someday be the language of quantum computing.

18. Originally Posted by tommac
Well what happens when wavelengths are smaller than the planck length?
I'd hate to think of the power of such a photon.

Deeper question is is it really that a photon can't have a higher wave length or just that within a reference frame anything shorter then that could never be measured.

IE If I accelerate to .99c doesn't isn't my Planck length ~7x shorter then someone at my non-accelerated reference frame?

From my understanding there is no upper or lower bounds to the wavelength of a photon because it is massless and also has an relative wavelength with respect to any given inertial frame.

IE take a photon with a wave length of 1.616252(81)×10^-35 now travel towards the photon at .99c and it should be blue shifted but how can you blue shift something that is at a hypothetical upper limit?

19. Originally Posted by blueshift
At distances smaller than the Planck length it becomes impossible to determine which event comes prior to another if both events take place within that Planck length of 10^-33 cm. Take that number and divide it by the speed of light and you get roughly 5 x 10^-44 seconds, the shortest amount of time that is possible to measure at all or even conceive of. The uncertainty principle of quantum mechanics prevents any speculation on times shorter than that. Therefore, no wavelength can be shorter because all wavelengths can be measured for a duration.
So doesnt that mean that it has to be quantized?

20. Originally Posted by tommac
I would assume that it would have to be ... otherwise the double slit experiment wouldnt work?
Not necessarily. Wave mechanical solutions exist if a medium is assumed. A medium can be held in tension, establishing a field solution for every location. (Think of Bose noise reduction headphones: noise is inverted 180deg and remixed with the source signal. The net energy can actually be higher, but the deflection of the timpanic membrane reduced.)

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You can't measure the wavelength without time. Over time, you can see it repeat. An instant measurement is a classical idea, like taking a photo. So a photon acts like a particle and a wave. One we try to measure instantly, the other we give time.

See the problem here. Fourier discovered the math along time ago. If you take your time measuring something, it's hard to tell where it is at a given instant. If you measure it quickly, you can't see the wavelength.

The act of measurement with photons is flawed.

How am I going to measure skips of time that can't be measured, even in principle, when my apparatus 'lags'?

If you believe that General Relativity holds true, then a photon can be stretched to any wavelength.

If you believe Quantum Mechanics is king, then a photon only has so many wavelengths at any given time (per inertial reference frame) for a certain amount of energy.

I have no problem thinking that space and photon wavelength might be quantized, but I don't want to limit myself to a single untested theory. I'll stick to what I know.

The double slit experiment works in either theory, too.

22. Originally Posted by Jerry
Not necessarily. Wave mechanical solutions exist if a medium is assumed.
Really? Why would it change if we detected one? basically why wouldnt you be able to put detectors in both holes then? Once the photon is detected as going through one hole the other one will never be detected.

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Originally Posted by Cougar
I don't know anybody who predicts a gravitron.
Actually, I predicted the Gravitron.
Admittedly, when I sketched it while I was at school in the 70s, it had a paraboloid inner surface on which people could walk around once it was spun up to speed. Namby-pamby health and safety laws applied to the real Gravitron seem to require people to just lie in their harnesses and pull g's. Dull.

Grant Hutchison

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Originally Posted by grant hutchison
Actually, I predicted the Gravitron.
Admittedly, when I sketched it while I was at school in the 70s, it had a paraboloid inner surface on which people could walk around once it was spun up to speed. Namby-pamby health and safety laws applied to the real Gravitron seem to require people to just lie in their harnesses and pull g's. Dull.

Grant Hutchison
It's ok Grant. A few of us managed to flip ourselves head toward the ground once enough spin was attained. Staying like that while she slows down was not recommended though.

25. All of this some times cleaver stuff about what a graviton might be is of little matter. Good grief did I say that ? deliberately. smaller than a planked length. Just how small is the plank. You can by now see that this subject is going nowhere. We just do not know yet. , But we must speculate and debate. If we want this question answered and we do.
We must continue to attempt to define that what is as yet not known.

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If you're the one walking the plank, it can seem entirely too small.

If you're talking Planck, then it's still too small for my taste.

Yes, this post is just a play on words. I just feel that words are important when you're expressing an idea.

27. Originally Posted by alainprice
Yes, this post is just a play on words. I just feel that words are important when you're expressing an idea.
Nah

28. Nah? words aren't important?

You say Maths isn't important as well.

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Originally Posted by tommac
So doesnt that mean that it has to be quantized?
I don't see what that has to do with the quote I put up. You didn't make things clear. What is it that you are asking that has to be quantized in with this particular
question?

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The question is whether the wavelength of a photon is quantized or not. For myself, answering this question would immediately lead into: is space quantized? Neither one of these issues addresses gravitons, so I'm not going to answer either.

The question should be whether the wavelength of a graviton is quantized, since the thread is not really about photons.

Quoting questions and trying to answer them rarely accomplishes anything with tommac, other than more tangential questions.

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