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  #21  
Old 03-06-2015, 09:59 PM
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Eratosthenes (Peter)
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Originally Posted by xelasnave View Post
I was more interested in how you would describe the relationship between a marble and a ball, similar to the op, using hypothetical gravitons . How do they act with the ball and the marble. I ask as much for speculation but upon the model gravitons would allow.
I tend to think in terms of fields with particles being tiny local vibrations in the field.

what if you had two magnetic objects? Are there "magnetons" between the two objects imparting information and dictating how the objects behave??

(perhaps Entropy should be dragged into this "information" concept that you raise?)

Last edited by Eratosthenes; 04-06-2015 at 01:01 AM.
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  #22  
Old 04-06-2015, 07:40 AM
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If the Higgs field (particle) is responsible for the property of "mass" in the Universe, can we assume that the Higgs particle is some how intertwined with the Graviton?? (both are supposedly classified as bosons. Although the Higgs field doesnt interact with other fields? Not like the TOP quark, which is a heavier particle than the Higgs Boson but can interact and therefore a little easier to produce and detect)
(1) The Higgs field is responsible for mass not the Higgs boson.
(2) The Higgs particle is only "associated" with bosons having mass such as the W and Z bosons through spontaneous symmetry breaking of the electroweak force. Gravitons are massless.
(3) The Higgs field is only accountable for about one percent of the observable mass in the Universe. While the Higgs field accounts for all the quark mass, it only accounts for about one percent of the mass of protons and neutrons each of which are composed of three quarks. The reason for this discrepancy is that 99% of the proton and neutron mass is taken up by binding energy that holds the quarks together which is not attributed to the Higgs field.
(4) Given the Top quark was the sixth and last quark to be discovered it was certainly not easier to produce and detect.
The larger mass required more powerful particle accelerators to produce the Top quark. Then there was the added complication that the Top quark immediately decayed into a Bottom quark which in turn decayed into a Charm quark which in turn decayed into a Strange quark. The difficult was digging out the signal attributed to the Top quark and not to the decay products.
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  #23  
Old 04-06-2015, 10:13 AM
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Thanks for trying to answer my question Peter.
Unfortunately I am still in the dark.
Irrespective of how the H graviton is describes how does it work between the ball and the marble.
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  #24  
Old 04-06-2015, 10:19 AM
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Originally Posted by xelasnave View Post
Thanks for trying to answer my question Peter.
Unfortunately I am still in the dark.
Irrespective of how the H graviton is describes how does it work between the ball and the marble.
I wouldnt even attempt to answer you question - just posed some questions. I am always in the dark

Of course one can just read accepted current doctrine from the text books and parrot them, or cite some peer reviewed articles to paint a nice safe portrait, but I feel the interesting stuff resides in the unanswered questions and philosophical speculations. Never fear the paid paranoid priests who guard the Temples and worship the plastic scriptures
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  #25  
Old 04-06-2015, 01:33 PM
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Alex,

Let's have a look at your marble/ball example and why gravitons fail miserably to explain the gravitational interaction between the two.
In this case the marble and ball are treated as point masses.

Since gravitons involve a quantum field theory of gravity one needs to look at the initial and final quantum states.
In this case the initial quantum state could simply be the marble and ball before interaction, the final quantum state is the gravitational interaction between the two.
In between the initial and final states are the intermediate quantum states involving the creation of the graviton and it's momentum, plus the momentum of the marble and ball etc.
The exercise is to sum over the various momenta in each state that produces an answer that not only makes sense but agrees with experiment and observation.
Let's keep this idea to the side for the time being.

In the same way we can examine the electromagnetic interaction between two charged particles involving the creation of virtual photons.
Recall in a PM I introduced you to the concept of Compton wavelength as a way to explain the BB singularity.
When two charged particles interact and a photon is emitted, the particles undergo a resonance which smears the particles over space time.
The particles are no longer considered point sizes of zero dimension but are at dimensions comparable to their Compton wavelength.
This is important has it allows energy limits to be imposed much like the case of String Theory using renormalization. By utilizing renormalization and summing over the momenta for all the initial, intermediate and final states a finite value is obtained.

Unfortunately when it comes to a Quantum field of gravity there is no way we can treat a particle as anything but a point source. Since a point source has a zero radius we find by summing over the momenta we obtain infinite values.
If the particle is treated as a string or a loop which has an infinitesimally small but non zero dimension we have what is known as a renormalizable theory.

Unfortunately a quantum field theory for gravity is non renormalizable.
Until physicists can produce a renormalizable theory one can argue that gravitons don't even exist from a theoretical viewpoint unless one assumes that String or Loop quantum gravity theory is correct which also predicts gravitons.

Steven
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  #26  
Old 04-06-2015, 02:11 PM
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Hi Peter
I just thought you may have had a speculative view on the matter.
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  #27  
Old 04-06-2015, 02:20 PM
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Thanks Steven.
So all we need is a new formula
Can you come up with what they need.
You should at least write a book.
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  #28  
Old 04-06-2015, 02:49 PM
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Originally Posted by Eratosthenes View Post
.... Never fear the paid paranoid priests who guard the Temples and worship the plastic scriptures
I think this is unfair statement.
Until we know all the facts, including the way of thinkng of mainstream "priests", the wild speculatios can make you feel good.. but they will not place you any closer to the reality.

What Alex was always after (we had quite a lot of good discussions in the past on this forum) is simple explanation, mechanic of the gravitation phenomenon.
This way of thinking is natural for all of us humans.. because majority of us want to relate to our everyday experience.

Sometimes this is not possible, simply because our brains are not wired to understand QED (myself included. Feynman said the same to himself.. for completely other reasons I think... )... they are basically wired to keep us fed and away from danger of being eaten by predators.
It is a wonderful and quite accidental byproduct of our brains functionality evolution that we humans are capable of abstract concepts at all (math).. and also sometimes capable of finding appropriate analogies to help the less skilled in abstract thinking to better understand those concepts..
And don't forget, those less capable thinkers are acually majority, so they are those taxpayers who are paying the bills for majority of that small minority of abstract thinkers
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  #29  
Old 04-06-2015, 02:54 PM
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Read up on renormalisation.
I gave up on push gravity as it seemed to me one could only end up with infinite situations when trying to record all the interaction.
Did I get right.
I think I can understand
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  #30  
Old 04-06-2015, 10:43 PM
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I think this is unfair statement......
...its more of a cynical statement bojan. Scientific research today (and for some time) tends to be conservative, boring and lacking in imagination and risk taking. Some areas of research are still vibrant and plowing along but generally the science that is conducted today just doesnt compare with the epochs that spewed out quantum mechanics or general relativity.

I suspect that the current Corpocracy has spread its tentacles to the sphere of science and engineering. In a sense science has been contaminated by corporations and their short term profit making ideology. Where are the dreamers today? What are we doing in the area of Space exploration apart from probes and some space telescopes? In the late 1960s when humans landed on the moon, the feeling in the general population as well as among scientists was that by the year 2000 a lunar base would have been set up and planetary landings planned soon after.

Just to give you an example. In the cancer research area, very little funding is directed towards cancers that dont effect huge numbers of people. Its a business model mentality. Can the Pharmaceutical companies get their money back and how fast?

Almost half the scientists and engineers in the US are directly or indirectly linked to the military industrial complex. In fact the top graduates are head hunted by the military industrial complex and stock market analysts.

Why sweat away in a University trying to carry out fundamental research or pushing the boundaries of knowledge and technology, when you can earn ten times the money working in the stock market developing day trading algorithms or designing cluster bombs for Raytheon?

Look at the Nobel Prizes handed out these days. They generally dont have have the depth and importance when compared to the first 60 years of Nobel prizes. How does one rate a Nobel prize for the invention of a blue LED about a decade ago with Dirac's or Shoredinger's Nobel Prize? Even the Nobel Peace prices have been trivialised and politicised.

Cynicism is generally counter productive, but I think science today deserves all it gets - generally boring riskless profit making ventures. Pathetic really - when science is one of the most magnificent tools of discover uncovered by humans. (and we can thanks Eratosthenes in about 190 BC for kicking off the scientific method in earnest)
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  #31  
Old 05-06-2015, 06:51 AM
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Actually, I couldn't agree more with what you wrote here... A movie "Idiocracy" comes to mind..
But.. all this is a hard reality, unfortunalely - we all have to eat - and the only way to improve this situation is education of people... which is extremely important and sensitive activity (it must be conducted in a right way, with almost individual approach.. because what works for me won't work for Alex and vice versa), and at the same time it is very non-profitable, money-throwing exercise from fiscal and business point of view.

Back to analogies..

When thinking about counter-intuitive concepts of residual and/or "emerging" forces, aerodinamic lift comes to my mind.
I bet that 90% of public do not realise that the force that keeps the aircraft in the air is a result of difference of speeds of airflow below and above the wing.. resulting in difference of static pressures between upper and lower side.. and hence the lift.

This is another interesting read on gravity as emerging force:
http://en.wikipedia.org/wiki/Entropic_gravity
http://arstechnica.com/science/2011/...hermodynamics/

Last edited by bojan; 05-06-2015 at 03:11 PM.
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  #32  
Old 05-06-2015, 08:07 AM
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Back to analogies..

....gravity as emerging force:
http://en.wikipedia.org/wiki/Entropic_gravity

makes sense, in the sense of how you get from the clumping of moleculular particles of dust into a star, then from there to a curvature of space/time.

but that would describe the effect rather than the cause, yes/no?

(its possible the cause is in there, just couldn't weed it out in laymens terms, wasn't it feynman who (also ) said if you can't explain something simply you haven't understood it.)
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  #33  
Old 05-06-2015, 09:16 AM
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...but that would describe the effect rather than the cause, yes/no?...
It seems so..
well, all theories are only more or less accurate descriptions of reality, IMO.

Last edited by bojan; 05-06-2015 at 09:30 AM.
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  #34  
Old 05-06-2015, 09:32 AM
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It seems so..
well, all theories are only descriptions of reality, IMO.
you mean like words can only be symbols (abstractions to a degree)? suppose thats why science likes maths.

but they both point to comprehension, so there's a way to go yet, for me at least in getting a mental grasp of what gravity might be.
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  #35  
Old 05-06-2015, 10:26 AM
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you mean like words can only be symbols (abstractions to a degree)? suppose thats why science likes maths.
Exactly so.
Math is the only language that can consistently describe the reality.
Words are not good enough because in most cases they do not have defined meaninings and defined relationships between themselves ("What poet meant to say with those words" were my favourite expression to describe this situation).
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  #36  
Old 05-06-2015, 11:11 AM
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Since Maths has come up in the discussion it can be used to answer your original question whether space time curvature diagrams of say the solar system is an accurate representation.

Space time curvature flattens out as one moves away from the Sun.
The amount of curvature is of the order 2MG/(r*c)^2.
M is the mass of the Sun, G is the gravitational constant, r is the distance from the Sun, c is the speed of light.

Using Mercury as an example where space time curvature does cause its orbit to vary from the classical Keplerian orbit, the calculated curvature is approximately 0.0000000000000000001.
Even at the surface of the Sun the curvature is around 0.0000000000000009.

Given that totally flat space has a curvature of zero, the measurable effects of space time curvature is extremely small at least when applied to the solar system.
Hence the representation is grossly exaggerated.

The situation is very different however as one gets close to extremely dense objects such as black holes.

Steven
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  #37  
Old 05-06-2015, 12:00 PM
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Since Maths has come up in the discussion it can be used to answer your original question whether space time curvature diagrams of say the solar system is an accurate representation.
Steven
thank you,

i suppose to more accurately reflect the original question, would be to ask how an object curves space time.

i would guess that its isn't by displacement in a body (space time) but through the force that contracted the body pulling spacetime in towards it with it. like a weighted object dropped on a sheet and pulling in the sheet around it, except its not dropped but contracted into itself.

now to say that gravity is the curvature of space time is good for working out how orbits work, but i am not so sure this model would explain how gas clouds collapse/gravitate into stars. Then i suspect you are looking at gravity as an active force.

the emergent idea may make sense here, that gravity works differently at different levels.

a simple view, but i am wondering if it can be explained at these levels.

Last edited by yusufcam; 05-06-2015 at 01:14 PM.
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  #38  
Old 05-06-2015, 01:31 PM
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thank you,

i suppose but to more accurately reflect the original question, would be to ask how an object curves space time.

i would guess that its isn't by displacement in a body (space time) but through the force that contracted the body pulling spacetime in towards it with it. like an weighted object dropped on a sheet and pulling in the sheet around it.

now to say that gravity is the curvature of space time is good for working out how orbits work, but i am not so sure explains how gas clouds collapses/gravitate into stars. Then i suspect you are looking at gravity as a force.

the emergent idea makes sense here, that gravity works differently at different levels.

a simple view, but i am wondering if it can be explained at these levels.
No one knows how a mass curves space time because General Relativity is only a semi phenomenological theory where the emphasis is to explain the effect rather than the cause. It explains the concept of the Newtonian potential of gravity as a distortion of space time without explaining how space time curves. Newtonian gravity is purely a phenomenological theory as it offers absolutely no reason for the cause behind gravity.

The use of General Relativity for working out orbits has only a very limited application.
Firstly there needs to an enormous difference in mass between the central body and the orbiting body. Mathematically the orbiting body is known as a test mass, a mass which is not large enough not to create its own space time curvature.
Secondly the orbiting body needs to be sufficiently close to the central mass and/or the mass/density of the central body is great enough for space time curvature to be significant.

With the exception of Mercury all other planets are described by Newtonian physics where planets orbit in 3 dimensional flat space and gravity is a force.
Similarly the formation of stars is also based on the Newtonian version of gravity.

While it appears that Newtonian physics and General Relativity are two totally different theories of gravity there is a subtle connection between the two. Newtonian gravity is a first order approximation to General Relativity.
If you took the mathematics behind General Relativity and applied "normal conditions" (low gravity conditions and velocities well below the speed of light) the equations break down to Newton's equations.

Steven
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  #39  
Old 05-06-2015, 02:06 PM
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No one knows how a mass curves space time because General Relativity is only a semi phenomenological theory where the emphasis is to explain the effect rather than the cause. It explains the concept of the Newtonian potential of gravity as a distortion of space time without explaining how space time curves. Newtonian gravity is purely a phenomenological theory as it offers absolutely no reason for the cause behind gravity.

Steven
Excellent explanation.

That said, it's possible to go further than this. The idea that space-time is 'really' 'curved' only arises because we look at the maths of GR and insist on interpreting it in a way that makes intuitive sense to us in the context of the low energy conditions we usually experience.

Personally I find that a very useful way of thinking about it, however it's worth remembering that the physical theory is just a bunch of equations expressing relationships between directly observable quantities, and the actual curvature of space-time is only indirectly observed.

Occasionally it becomes very important to remember that the interpretation attaching to the indirect things is not necessarily real, just useful. A good example of this is the idea of the electromagnetic field. Very important in classical EM, but starts to look distinctly less real in the Feynmann approach (glossing over a lot of technical stuff).

Last edited by Dave2042; 05-06-2015 at 03:07 PM.
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  #40  
Old 05-06-2015, 02:11 PM
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thanks, thats quite informative...

it does open a different door though, is space/time considered a void or an object.

if its a vaccuum how does an object effect it?

its curious stuff.

Quote:
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No one knows how a mass curves space time because General Relativity is only a semi phenomenological theory where the emphasis is to explain the effect rather than the cause. It explains the concept of the Newtonian potential of gravity as a distortion of space time without explaining how space time curves. Newtonian gravity is purely a phenomenological theory as it offers absolutely no reason for the cause behind gravity.

The use of General Relativity for working out orbits has only a very limited application.
Firstly there needs to an enormous difference in mass between the central body and the orbiting body. Mathematically the orbiting body is known as a test mass, a mass which is not large enough not to create its own space time curvature.
Secondly the orbiting body needs to be sufficiently close to the central mass and/or the mass/density of the central body is great enough for space time curvature to be significant.

With the exception of Mercury all other planets are described by Newtonian physics where planets orbit in 3 dimensional flat space and gravity is a force.
Similarly the formation of stars is also based on the Newtonian version of gravity.

While it appears that Newtonian physics and General Relativity are two totally different theories of gravity there is a subtle connection between the two. Newtonian gravity is a first order approximation to General Relativity.
If you took the mathematics behind General Relativity and applied "normal conditions" (low gravity conditions and velocities well below the speed of light) the equations break down to Newton's equations.

Steven
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