The recent findings of the Higgs aka the Goddamn particle aka the God particle has thrown into prominence a few fundamental problems of Physics. Whats next is the buzz word. There are a bunch of fundamental problems in Physics that can be thought to bear with this. People are saying in a language of particle-physics which particle next? Graviton or aphotitons/Unlitons? The later is a name for the purported Dark-Matter particles if you care to name them like that. Its one matter that Higgs has not been found as such in terms of formal claim but a Higgs-like. But Hawking has conceded defeat to a bet woth 100$ while thats not a way to think Higgs is confirmed I also stand by it that: Higgs-like is a Higgs-lead or in other words there is hardly anything that I can think now that will debilitate the chances of Higgs or Higgs-somes. As a particle experimentalist its my 6-th sense [one sense per quark] that this is Higgs and this will be confirmed.
But Unlitons is a quite different issue. One can ask if Higgs gives mass to Gravitons? Does Higgs gives mass to Unlitons? These two will perhaps be the same question if you have Quantum Gravity in mind: Ina situation where GUT is a success every particle would necessarily mean Gravitons and Unlitons which will perhaps only be gravitational.
But the important question remains what are Gravitons ?
What are particles? What are Fields? What are waves? What exactly is a Graviton?
OK then lets start from basics.
Lets invite Newton over a dinner and ask him this: Sir Issaac Newton? Whats Gravity?
Heila hypothesis na fingo. A Gravity is an inverse square law Force and an inverse proportional energy. You call this force Gravity and divide that by the mass of the object that experience the force and you get a field. Lets imagine these objects are particles cos “I ain’t talkin” about waves. Huygens would be but he is such a brag. CAn you pass that soup please, up close?
Ok so we learned that there are energy, fields and forces for a particle which experiences these given a position and time for the particle around another huge particle thats producing this force.
How does the particle know where in the world the particle is wrt the Huge central or primary object? Its not like there are signs around this primary object where like a speed limit is written on a highway the energy and field values would be written. The secondary or small particle now has to talk with the primary object to know where its situated wrt the primary. How does it do it?
Newton thought it does so by action-at-a-distance. The effect of the force would be known instantaneously. Galileo did an experiment on speed-of-light and found such a behavior of light. Forces in his days were perhaps thought to transmit to infinite distances with infinite speeds, in other words the fact that you are here and you experience the effect of the primary means the primary has sent the action to your places instantaneously because while you are experiencing the primary you have signed no bonds that you will be stationed there and not relocate. I mean there are so many good things in life to be enjoyed. But you moved slightly and how would you know whats the effect of the primary, you need to know it instantaneously and you do experience the effect. So its only built into such an understanding that forces/fields/energy transmit themselves at infinite [or at the will] speeds. Monsters and epic manga can have such a scheme but we shall not judge Galileo or Newton for they were our only hope in those times to first flinch and then savior modern science from the clutches of a society that was predominantly anti-scientfic as they are now at-least in the way in which philosophical debates are made against ideas of Higgs, a scientific particle because its been named “God-particle”.
Ok so the force transmits at will. But now we know that thats not possible. We actually knew that since much more than a century. Waves of electric and magnetic phenomena travel at tremendous speed but not infinite at will speeds. So the kinds of fields the electric or magnetic phenomena are associated with travel at finite speeds. Those forces are not infinite so Gravity can’t be either.
One thing, when the electric and magnetic phenomena were understood, that came up was they satisfy a set of equations called Maxwell’s equation. These equations can be easily moulded into a form known as wave equations of motion. The objects that are particles such as the ones that experience Gravity as per Newton, satisfy a different kind of equation of motion known as the particle equations of motion.
So there are equations of motion which better be known as particle equations of motion [Newton's 2nd law is one example]. There are wave equations of motion. And the form of these equations of motion are differential equations of motion. When solved with appropriate information regarding a physical system they give us answers that we are often familiar with eg how a tennis ball will fly when you hit it with a bat or how a magnet will produce electricity if its rotated with “much” force.
These wave equations which therefore satisfy the waves known as electromagnetic waves because eg a radio device can send such signals of em waves are in terms of two fields known as Electric Field E or Magnetic Field B. But these equations are ready enough to be treated in the framework in which Einstein wanted to test every physical law. They are Lorentz-invariance ready. The speed of these waves were like for any wave equation [eg sound waves satisfy sound-waves equation of motion and this equation gives the value of speed of sound waves in various medium and vacua]. The Maxwell waves or em waves were found to have a speed equalling to 3×10^8 m/s which is called speed-of-light because light was known to be an undulation of E and B in a way satisfying the Maxwell’s equation. In other words E produces B and B produces E as per validity of these equations.
But their preparedness for Lorentz Invariance is a bit calling for much more attention. Here the E and B cast/map themselves into Einstein’s equation of [particles, waves] motion called Einstein Field equation where the fields are Tensors. So some quantities of Newtonian mechanics [Old Classical Mechanics] cast themselves into what are called 4-vectors and some into Tensors so that these quantities when looked at from another frame of reference would retain some sort of invariance. Or in other words when a transformation of frame of reference is effected lets say energy is the same in two different frame of references if the frames of references differ by speed and thats wrt a passage of time. But this time the Energy is in the sense of a magnitude of a 4-vector which is conserved wrt the passage from one frame to another but only energy is conserved wrt a passage of time. These 4-vectors and Tensors then constitute equations and constraints among themselves which are consistent with old classical mechanics or Newtonian mechanics. Einstein’s special and general theory of relativity can be said to new classical mechanics.
Now Einstein’s equations or New classical mechanics has in it both waves and particles. But nobody is yet alarmed that they will lead to quantum mechanics not even until 1930s when Qmech was not realized when Einstein himself became a vociferous critic of it and later recanted. he wanted to show that he had a tongue in mouth not a damn foot. He was not a fool but a great fella.
But what was recognized was perhaps unification such as space and time as space-time. Energy and momentum into Energy-momentum 4-vector. Which is why Einstein’s Relativity is called a 4-dim theory and our world suddenly became a hotspot for intellectual debate as people thought they might have had been ignorant of such a drastic character in the fabric of the Universe. Actually E and B were also realized to be an unified field. Or for not only particles there are fields but there are also fields for waves. From the wave equation of motion called Maxwell equations in the case fo E, B it was known that speed of such waves is 3×10^8 m/s. Einstein also espoused the idea of ultimate speed limit [speed of em waves] as there were no other forces known in those times that would have traveled so fast. All the Physics was understood by Einstein, hence he did not see any reason why he should not employ such an idea of limitations to relay of transmission of any kind. This might itself be the basis of Quantum Mechanics since something traveling at highest speed must have lowest mass as having mass would only take some amount of energy away. So we have something thats moving at speed of light and must have a mass of zero. Now waves are traveling at this speed but whoever ever has thought of a mass for waves? Einstein equivalenced mass and energy hence waves having energy must have mass. But the frame of references in which the speed of waves would be zero would be a frame where the mass of the waves would be zero. But perhaps nobody thought like that. Everyone was working on the theory and the understanding and many things gradually set into our understanding of it all. Even to this day this trend is going or we wouldn’t be asking numerous questions. Science!! such an affair. It pains you but you get the pleasure of knowing something thats not obvious but thats so immensely useful.
It was later realized that light not only propagates as wave but also as corpuscles. [There is a corpuscles theory of light of Newtonian kind, whats that? ] And this corpuscle called as photon can be said to have mass zero, but I don’t know if they did realize it or not. We are living in times when QMech is the order of the day and understanding of Relativity has been colored by QMech or the advance formalisms.
So here is the idea: Einstein’s framework/formalism of Relativity has in it both wave fields and particle fields in a way they are correlated by some constraints which were not as detailed by anyone’s work as they are now. They were unificated eg through Gauge symmetry [Phi, A fields are an advance way of saying E and B are the manifestation of the same field] But unification is not Quantum Mechanics.
So the Relativity of Einstein has particles of Gravity and waves of E and B etc. The fields of Gravity are particle fields, fields of Electricity and magnetism are wave fields. Being a wave has the advantage that you know the speed by default and there is one speed. They have to travel at a fixed speed. So as far as it goes we know Gravity fields as a particle field.
This then transpires to a very fundamental problem: is there a wave called Gravity wave. The basic properties of a field having a wave nature means extraordinary consequences. First off the particle nature of a field is default. [You have objects around you which experience this force or that force] So when there is wave nature to it it must mean that they together satisfy a wave and particle equation and hence must be a result of wave-particle equation and this is known as Schrödinger’s Equation, or a differential equation in qunatum mechanics in general. Then the field of this particle or wave can be quantized. Or in other words such fields/particles/waves are synonymous with each other. Having a particle automatically means a corresponding wave and vice versa. For a fundamental force this means a force carrier particle called as a Gauge Boson [0, 1, ... spin] which travels at speed of light and a force experiencing or interaction sources/charges/currents that are Fermionic particles [1/2, 3/2 ... spin]. Further a 0 spin Boson or force carrier is a scalar boson and spin 1 is a vector boson and so on. The Fermionic does not have such a special name but the fact that there are many kinds of Fermions. eg electron is a Fermion. Quarks are Fermion, protons are Fermions. But the Bosons are a very few kind, eg about 4 kinds that have been found, 1 purported that has not been and one Boson which is special because its not a carrier of force but gives mass to every other particle just like Your friend John gives beer to everyone who goes to his club.
So to have a force carrier or messenger for the Gravity particle-field so that the 2ndary or Gravity-force experiencing particle knows exactly where it is located wrt the source of the Gravity one must have a wave as well of this field. You either have a particle field a wave field or both and it has so happened that the 4 forces of fundamental nature that we know so far 3 have this characteristic: they have both wave and particle nature for their fields. They have therefore been quantized from a single equation of motion called the wave-particle field’s equation of motion.
But one of the remaining force-field the Gravity force/field/energy has not been known to have a wave and particle character. The erroneous understanding that General Theory predicts Gravity waves is well: erroneous. The fact as I just explained above to have a wave nature of something is to by default meet by a particle-wave nature and hence quantization since particle nature is a must. This is so if you consider something a fundamental force. And Gravity is considered a fundamental force.
So there are two approaches to face this problem
1. Consider Gravity alone and let it have just wave nature, we already have its particle nature hence it must lead to quantization a la Quantum Field Theory [a way to let the forces or fields or energy to be quantized and satisfy the equations of motion for both particles and fields and have the properties of Quantum Mechanical systems] Then unify this resulting quantum-field with other fundamental forces which are Weak Force, Strong Force and Electromagnetic Force. Note that all these forces were dual Field forces [particle and wave] and they are unified. Unified means in the greater framework of a theory one could define just one variable which would give the different forces under different physical situations. Its an equivalence!! just like E and B were unified and is a same field in the greater frameworks. USA is a unification of 52 states. They are all equivalent wrt a certain privilege if the “Federation” makes it so. But its not unified with Mexico although Mexico has its internal equivalence which are not same as that of US. But given the definition of United Nations policy/pacts Mexico and USA are unified.
2. To unify the 3 forces described in 1 with Gravity and then look for clues to quantize Gravity. To say “quantize” is to mean an acronym for having both wave and particle nature of a variable such as Force, Field or Energy.
Its not necessary that any of the above two will be satisfied. But then how could we understand that a particle experiencing the force of gravity knows where it is present in the gravity field? We can’t allow the relay of information to surpass that of speed of light. That will invalidate everything else we know which have worked so well. This is a Physics problem and this does not come with a priori solutions or insights or ideas or answers.
One can only see deeper and deeper.
But what has been done so far as I understand is the wave nature has been imposed on Gravity Fields by considering such an equation of motion and then letting it quantize [which it must since now it satisfies such a differential equation]. This is called as an attempt at GUT, the vision of Einsteinian Era. But the whole idea of letting fields have both particle and wave nature is the most fundamental and central formalism and nature of Quantum Mechnaics [which is called Quantum Field Theory, since Force/Field are involved]. This is therefore called a Supersymmetry Theory since it has superseded all expectations of trying to stop loseends and find a happy marriage of what we know and what ought to be there and what its forms shall look like [eg missing particles: supersymmetry]. Its a 3some marriage.
So there are two ways of looking at the Gravity Force the GUT vision and the elegant formalism of QFT [call it Quantum Force Theory for once no !!] and GUT can’t necessitate a wave by its own nature without leading to QFT-supersymmetry. Supersymmetry can’t dictate terms to what we must or must not find as long as we don’t. eg Higgs was found as a characteristics of this central tenet of QFT hence people have started talking about supersymmetry GoldRush now. But its not clear whether General Relativity actually predicts Gravity waves. If it does you immediately quantize this wave-field and get the character of the particle called Graviton. No Classical theory has an apriori property of predicting if there must be a wave nature to an inherent field without first observing such a wave. You observe electro-magnetic field hence you can right away write some sort of equations that satisfy wave-motion. To predict such one must have a wave equation by default not by imposition. The imposition is necessitated as I explained to avoid action-at-a-distance which is a catastrophe as also explained. But we have not observed such Gravity waves, the there are experiments that are set up to circumvent this problem to bring some credit of observation to teh Physical problem. Any kind of observation helps in the type of physical problems that have no clue. But particle nature is by default.
The basic difference is a Gravity Force/Field is experienced by huge objects which are not operating in the quantum scales and for a unification with all other 3 forces which are quantum-scale forces one must be in such a scale. How can you have a quantum-particle communicate information to large objects such as a ball or a satellite or an earth?
And Gravity is not observed for quantum-particles, they have mass which is energy and their energy is satisfied for other forces so we do not know Gravity is a quantum-force or not that is, present at that scale as a smaller or larger value wrt the other forces. May be we can just live without unification and mind it without quantization.
Only finding something by observation can change such knowledge.