Gravitons and Unicorns

Well…Newton never attempted to explain the mechanism of gravitation, and swayed back and forth from the mechanical model as the mood suited him - it wasn't at odds with his formulation, but at the end of the day he was happier to consign the mechanism as one of God's mysterious forces, which man was likely to never understand (nor was supposed to, since God would have designed such mechanisms to be beyond our ken). The first chapter in the Pushing Gravity book gives a nice history of this period. Einstein was the archetypal thinker. He built his whole theory on the basis of one experimental result (The Michelson-Morley experiment ---> light travels at a constant speed in all reference frames) combined with the second postulate that all observers moving at constant speed should observe the same physical laws, plus a whole bucketful of mathematics which dropped out of the former two ideas. I would question the ability of such an approach in completely explaining the nature of the universe - Einstein's model is certainly a good one, in that it has the power to predict, but it does falter when confronted with a number of phenomena which appear to be related to gravity.

To answer your questions -

1. Einstein's general theory does predict some form of gravitational radiation in the universe, and the graviton has been proposed as a possible agent. If the gravitational force is transmitted through the Universe by radiation, there should be a gauge boson to carry it between objects. This quantum of gravity, which we all know and love and term "the graviton", should bear some similarity to the photon, such as the ability to travel near-infinite distances. Physicists have calculated that if the graviton exists, it has an internal spin (angular momentum) of 2, and a minimal or zero rest mass. However, because the gravitational force is so weak except on the largest scales, it is darned difficult to detect the little blighters. So if gravity does have a quantum nature like the other three fundamental forces, it may only be significant in extreme conditions such as the direct aftermath of that accursed Big Bang Nonsense. The detection of gravitational waves in space would be the best indirect evidence for the existence of gravitons. Astronomers are currently searching for evidence of these waves in the aftermath of supernovae and the collision of galaxies - and good luck to 'em.

2. Don't have a problem with this. There is glue and there is glue. On the scale of the universe, the graviton glue is going to be tremendously dense. I might have missed the point of this question, but it doesn't seem at odds with the graviton model, and would be actively supported by the Pico-graviton theory, which predicts total absorption of pico-graviton particles in collisions.

3. Swings and Roundabouts. This is the kid's great "why?" approach…

We're going to the shops today.
Why?
To get some bread.
Why?
Because we need to eat.
Why?
People starve if they don't eat.
Why?
Etc etc etc

The graviton in this particular theory is (and let me say as I always do that this is my own little opinion) a mechanism. It represents a component of gravity as it exists now. Every single process and piece of matter in the Universe can be subjected to the "Yeah but what created that" (= "Why?" scenario) approach ad infinitum. Even the Big Bang cop-out fails when someone says, "But what created the Big Bang?". Accept that the theory explains the current state of the mechanism (a snapshot if you like) and you'll be okay, start trying to unravel what created the graviton and you'll end up back at the Big Bang, but if that's your cup of tea, then fine, but I think your question 3 would apply to absolutely any theory, leading to all sorts of generalised, grand theories of everything, and I don't want to go there until we've actually proved the graviton exists (or not)! As my grandfather used to say, "One thing at a time".

4. Totally disagree. Unless you propose that there's a God who created the graviton and made it incapable of detection or manipulation I don't see the logic of your statement. Or then again, I'll concede, if you follow the curved space model, then gravity screening would be a non-starter, since you're effectively trying restructure localised 4-dimensional space (but give us a few hundred years in this scenario and who knows?), although you seem to suggest this is a more likely approach - a sort of warp drive if I remember the theory, continually contracting the space ahead of the vehicle, although I would have thought the vehicle would have undergone the same contraction. Podkletnov has presented the first experimental evidence for screening gravity. There's a lot of debate about the validity of the results, but it would seem that Boeing is sufficiently interested to fund further research. For once, we're in the hands of the experimenters, and they'll be the ones to tell us if it's possible, not the theorists.

I guess I err on the side of the graviton, but good post Makis, plenty of food for thought.

I certainly appreciate you taking the time to answer my questions in a laymans way.

<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>

Podkletnov has presented the first experimental evidence for screening gravity.

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He has demonstrated a 2% decrease in target mass or weight, very far beyond screening and very far from understanding of what it is really that has has caused the decrease(probably some kind of EM wind). Many think it is a non-rerpoducible experiment. Boing is more interested in the gravity gun he claims to vaporize objects and to put sats into wild spins (gravity torsion beam).

<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>

For once, we're in the hands of the experimenters, and they'll be the ones to tell us if it's possible, not the theorists.

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Most of them are not even sure of what they are experimenting with. When you are talking about Cosmology, it is one way: Theory creation and verification through experimentation. That's why the main stream Physicists hesitate to accept graviton and picos of; There is really no way to set up a realistic experiment unless it is on Universal scales.

My mind is <i>tabula rasa</i> regarding this matter. I tend to agree with some claiming that when the right theory comes along everybody will scream: "it was obvious!". For now it is not.

But others claim that is is beyond our ability to comprehend it, save experimenting with it.

Well, the LIGO project certainly seems to have a handle on what they're trying to detect - you can't set up an experiment without having some idea of what you're trying to find out (ignoring for the moment kids with their first chemistry sets, and Rutherford-style discoveries!). The guys on that team are looking to organise gravitational wave detection equipment in the form of a number of ground based suspended laser interferometers. The main objective will be to reduce the low frequency detection threshold from the current level of 100 Hz down to a few Hz to enable detection of gravitational waves from potential sources like black holes (ugh!), neutron stars, binary compact star systems, x-ray pulsars and good old supernovae. The latter offers a good opportunity for detection if the collapse is non-spherically symmetric - there's a lot of hoo-hah about the quality of such a signal depending on an efficiency coefficient feeding off the symmetry variable, but it boils down to the messier the supernova, the more chance we have of detecting something. Binary neutron stars seem a better bet - those that orbit in periods of a few days and under can produce stochastic backgrounds in the frequency ~ 10^-2 to 10^-5 Hz, still difficult to detect at the moment, but if such a system undergoes collapse and the two stars coalesce, then theory (sorry!) predicts that the gravitational wave signal may rise to as much as 1 kHz at the point of collapse. Non-symmetrically rotating neutron stars also pulse gravitational waves but for various reasons (orientation, emitting properties etc) we can't see them. It still seems however, that our best chance of measuring this phenomenon is through a burst source, although because of the long term nature of some of the other stuff, we've always got a shot at screening out the noise - current estimates reckon about a year of monitoring should be capable of detecting something. So there is hope - the mathematics supports the endeavour and the whole thing is certainly on a "universal scale" (well, galactic, anyway!).

I'd footnote that mainstream physicists hesitate to accept any theory different to the mainstream (hence sites like this), but I might be accused of being churlish, and that would never do. <img src=icon_smile_big.gif border=0 align=middle>

Whoever is interested may check this out:

go.msn.com/CM/11090/default.asp?target=h....com/%3Fid%3D2072733

[Makis]
"Even with the graviton present, isn’t the case that the search of a mechanism for gravity cause is just transformed to a search for a mechanism of graviton creation? Then, graviton theory supporters cannot claim they have a mechanism for gravity. They still have the effect and an assumed cause. That’s no different, in my view from assuming any cause, or even, no cause at all. (De facto existence)"

I've long leaned toward Petr Beckmann's idea that gravity was a yet undescovered form of magnetism, but I'm willing to consider seriously the idea that gravitons, (of the kind discussed in "Pushing Gravity"), are a logical cause of gravity. The best reason for so leaning, is the problem which vexed Newton. How one object could influence another object at great distances (or any distance for that matter), without some intermediary force, was inconceivable to him.

Just because we don't know the "cause" of these hypothetical gravitons themselves, does not rule them out as a logical model for explaining gravity.

I'll offer one possible cause of gravitons in the spirit of pure speculation, since it should be okay to speculate on a speculation, in this forum. Here it is:
Halton Arp (also) speculates, that as the mass of matter in old galaxies increases with age, it eventually reaches a point where it (the galaxy) simply vaporizes back into the energy field of the universe. This vaporization event could be (in my opinion), the creation of gravitons! Why not? Anyway that's one possible "cause" of gravitons. I'm sure there are others. <img src=icon_smile.gif border=0 align=middle>

Consider the following comparison table:

God Graviton
It is everywhere It is everywhere
Not directly detectable No directly detectable(to date)
Can act in an instant Moves at increadibly high speeds
Rules the Universe Holds the Universe together


It is known that whenever humans stamble it is natural for them to invoke the idea of a God or the Supernatural.

I do not dispute that the graviton may be a real entity and acts the way some believe. I am not prejudice about it. My questioning is on the basic level. Is graviton an attempt to save the day?