quarks do exist but we cant really do anything with them. right now all we can do is observe them at great technical and electrical expense. keep in mind that a "quark" isnt just one thing. quarks are a class of subatomic particle. keep in mind that when dealing with subatomic particles, mass (not size) is the determining factor in how easy a particle is to detect. this can be seen in the case of quarks. they are one of the smallest particles theorized but its mass is high enough to be detectable.
the thing about gravitons is that if the theory is true, they never cross into our universe so there is no way of using them. the current theory basically suggests that gravitons exist in another dimension right next to ours. in that dimension they are one of the strongest forces, so strong that their presense can be felt in our dimension and is represented in our universe as gravity. it also suggests that there exist complimentary versions of matter in our universe in other dimensions and that the mass in these other dimensions affect our universe in the form of gravity. therefore gravity is the effect of particles that we can never reach, touch or manipulate because they exist outside of our universe.
imagine a blanket stretched between 4 chairs. put a softball in the middle. from the underside, we can see the effect of the presence of the ball, but not the ball itself. we have been looking for the "ball" in our universe and have failed. some scientists think its simply a matter of making more sensitive detectors, but it may be as simple as the blanket and ball analogy. we cant find them because they dont exist here. gravity is the affect of the presence of particles in a neighboring dimension.
if these dimensions didnt exist there would be no gravity in ours because there would be no exotic material to create gravitons. perhaps in these other dimensions gravitons are the principle particle that all matter is made up of, we dont know because theres no way to know if the theory is true. if it is, this means we would need a device that manipulates matter and enery in another dimension, not ours. i have no idea how that could be feasible.
also keep in mind that most theories dealing with gravity were mostly invented in order to keep a particular theorists mathematical proof valid. a stop gap measure inserted into a theory that keeps the rest of it working. string theory is one of the most popular out there, but to date not one part of it has been proven and yet most physicists accept it almost as fact. bear that in mind when you read abou extra dimensions and hyperspace; its mostly all bunk.
the difficult part about making sense of all this is in order for me to explain one unproven theory, i must reference another equally unproven theory. the skill in being a scientist and physicist (at least today) is being able to take the little pearls of fact found in these theories and being comfortable ignoring the rest even though most of your peers (or your betters) whole-heartedly bet their careers on them. backing up theories with other theories that have yet to be proven makes them all so wide open to interpretation that it is very likely that the discussion i have made here today is completely false when approached by someone with a different take on the same ideas.
in other words, dont take any ones word for it. if you read an article (or even in an encyclopedia) that theory X has been proven by Y and Z, it is probable that they are the result of someones unique INTERPRETATION of the problem, not necessarily because it has been abolutely proven.
Read this, this and this.
