[JohnDuffield (OP)]

IMHO it's an unfortunate convention that gravitational potential is set to zero at infinity and negative at the surface of the Earth. This negative is not a true negative, in that there are no things that exist that are comprised of negative energy. Instead a body has less mass-energy at a lower elevation, hence the mass deficit. It doesn't have the same mass-energy plus some magical mysterious negative potential energy.

Unfortunately some people promote bad physics. The one that I particularly dislike is gravitational energy is negative so the net energy of the universe is zero. This is pseudoscience, particularly since gravitational field energy is positive. See Einstein saying as much here: "the energy of the gravitational field shall act gravitatively in the same way as any other kind of energy". 

[Atomic-S]

I too have been puzzled by the energetics of gravity. As a matter of practical science, we can observe that a mass, on approaching a gravitating body, experiences a force in the direction of its motion, which constitutes work upon the body (as seem by an observer on the gravitating body), and if that work is removed from the system as by friction and thermal radiation, the energy of the system ends up less than what it was before.  Accordingly, we observationally conclude that the energy of the system is less when the bodies are close together, and on that basis, assign to the lower altitudes a lower gravitational potential.  But does that mean we have literally negative energy?  That involves delving into some difficult areas.  One is the quantum equivalent of energy, namely frequency, in which a particle of energy E has a frequency of 2 pi E/h .  There is reason to think that the correct E in this formula is the mass of the particle (special relativity seems to require that).  For a particle to have literally negative energy, the mass would have to be negative, which has the curious consequence that not only must the quantum frequency be negative (resulting in a reversed complex exponential), but its mass must be negative also. But if its mass is  negative, then it creates repulsive rather than attractive gravity. No such thing has ever been seen of ordinary matter; however if we consider the gravitational field itself as having an energy, then it itself may generate additional gravity.  That contradicts Newton's formulation of gravity, but is not necessarily in error because Newton's formulation of gravity is an imperfect approximation valid only in the limit of fairly ordinary circumstances. Does a gravitational field, being of negative energy, generate additional gravity that opposes itself? These are the kinds of questions that can't be answered without digging into the messy details of general relativity.

[Petrochemicals]

This is from a book John


"you have to increase the gpe of the mass to take it into infinity where is gpe is zero it original position must have been one is negative gpe( equals to minus the work you have todo) and therefore negative gravitational potential"


 so it's only negative in relation to You doing work to it, or a mathmatical principle of an equation, not a physics.


The other theory is gravitational field strength, it seems is from the radius of the earth toward the centre  where gravity is reduced owing to  less mass beneath it as you go toward the centre, and more mass attracting you the other direction(negative mathmatics again). Surely thats wrong as on a mountain you weigh less even though theres more mass beneath ?

[zx16]

Is there really such a thing as  true "kinetic energy"?  I mean according to "Relativity Theory", nothing really moves.  It just depends on how you look at it.
For example, when you look at the Sun from a place on Earth, the Sun looks like it's moving across the sky.  That movement must give it kinetic energy.

But when you look at the Solar System from outside, the Sun stays still, and  it's the Earth that's moving, so the Earth must have kinetic energy.

It seems therefore that both the Sun and the Earth have kinetic energy.   But how do  you measure it?

[Colin2B]

Is there really such a thing as  true "kinetic energy"?  I mean according to "Relativity Theory", nothing really moves.  It just depends on how you look at it.
For example, when you look at the Sun from a place on Earth, the Sun looks like it's moving across the sky.  That movement must give it kinetic energy.

But when you look at the Solar System from outside, the Sun stays still, and  it's the Earth that's moving, so the Earth must have kinetic energy.

It seems therefore that both the Sun and the Earth have kinetic energy.   But how do  you measure it?

Excellent. Good to see you really thinking rather than making odd interjections.
What you have realised is that the measurement of energy is relative and depends where you make the measurement from. This is also true of potential energy, if you are at the bottom of hill an object at the top has more PE relative to you than if you were half way up. So you have to be careful to define what scientists call the system when you make your measurements and then energy is conserved within that system.

[PhysBang]

so it's only negative in relation to You doing work to it, or a mathmatical principle of an equation, not a physics.

You have to understand that Mr. Duffield has a book to sell and a pet idea to peddle. He has admitted many times that he doesn't actually do physics problems.

[MichaelMD]

An ether theorist like myself gets quite a different picture of how gravity works.

An atomic/quantum structured body like a planet has an auric energy field composed of elemental etheric energy units, which operate through vibrational resonance between elemental units. (The elemental ether units had originated after a first-causal oscillational world transitioned to a universal, unstructured, vibrational,  ether matrix.) After the formation of this universal ether (containing identical, elemental, units, in intimate proximity, resonating with each other vibrationally, in a smooth, perfectly-linear, mechanism), next, a quantum/atomically-structured world was formed, like the one we are in. Atoms of solid bodies were built up from the elemental units of the ether - thus, these kinds of quantum units still retain the ability to resonate with elemental units, such as those that make up the ether-matrix existing in space. (This is the only way to understand Quantum Entanglement, for example. The so-called "entanglement" of two quantum units occurs because they communicate, through the ether matrix, via perfectly-linear radiated packets of elemental ether units, in the space between them. Elemental ether units are the only actual participants in that phenomenon, with the quantum units "walled off," kinetically, like cool "arms" of a smooth, purring, underlying matrix-mechanism.)  This elemental ether matrix is undetected by our technologies because of the extremely rarified scale of the etheric units making it up.

A pair of bodies in space are gravitationally attracted toward each other because they each have an auric field, coming from the ether units radiated from the quantum units their atoms are composed of. (The true, formative, forces binding the atoms are these elemental ether units.) Radiated elemental units from the densely packed atoms of two solid bodies resonate with identical elemental units of the ether in the space between them. Thus, the auric space between the two bodies is more etherically resonant than is the ether in the space outside of the auric zone, so the auric zone represents a zone of greater resonance, and gravitational attraction.   

[JohnDuffield (OP)]

You have to understand that Mr. Duffield has a book to sell and a pet idea to peddle. He has admitted many times that he doesn't actually do physics problems.

I don't have a book to sell or a pet idea to peddle. I'm here to educate and inform with reference to robust physics and so oppose the popscience misinformation that is sadly all too common these days. Einstein made it clear that gravitational field energy is positive, and that this energy has a gravitational effect.

[jeffreyH]

John they are going for 51p used on amazon.
https://www.amazon.co.uk/gp/aw/d/0956097804/ref=mp_s_a_1_1?ie=UTF8&qid=1488917147&sr=8-1&pi=AC_SX236_SY340_QL65&keywords=relativity%2B+duffield

[guest39538]

Einstein made it clear that gravitational field energy is positive, and that this energy has a gravitational effect.

An impossibility, positive v positive = expansion not contraction.

[jeffreyH]

Einstein made it clear that gravitational field energy is positive, and that this energy has a gravitational effect.

An impossibility, positive v positive = expansion not contraction.

Exactly!

[JohnDuffield (OP)]

Those used copies are nothing to do with me. I can't stop people selling them on Amazon. No new copies have been on sale for about 5 years now.

[guest39538]

Einstein made it clear that gravitational field energy is positive, and that this energy has a gravitational effect.

An impossibility, positive v positive = expansion not contraction.

Exactly!

It is the negative of any S that holds the positive of that S in situate..

[JohnDuffield (OP)]

An impossibility, positive v positive = expansion not contraction.

It's not an impossibility, it's general relativity. Check out the stress-energy-momentum tensor  that "that describes the density and flux of energy and momentum in spacetime". It's the energy-density gradient that makes light curve and matter fall down. Also see the Einstein digital papers: "the energy of the gravitational field shall act gravitatively in the same way as any other kind of energy".   

[jeffreyH]

Ok John can you list some of the exact solutions to the Einstein field equations that have been found. I can check the answers for you if you like. Seeing as you are such an expert relativist. Oh and not to include the Schwarzschild or Kerr type solutions.

[JohnDuffield (OP)]

Ok John can you list some of the exact solutions to the Einstein field equations that have been found. I can check the answers for you if you like. Seeing as you are such an expert relativist. Oh and not to include the Schwarzschild or Kerr type solutions.

See the scholarpedia article by Malcolm MacCallum. It perhaps gives you what you're looking for:

http://www.scholarpedia.org/article/Exact_solutions_of_Einstein%27s_equations#Some_important_solutions

[guest39538]

An impossibility, positive v positive = expansion not contraction.

It's not an impossibility, it's general relativity. Check out the stress-energy-momentum tensor  that "that describes the density and flux of energy and momentum in spacetime". It's the energy-density gradient that makes light curve and matter fall down. Also see the Einstein digital papers: "the energy of the gravitational field shall act gravitatively in the same way as any other kind of energy".   

Sir have you ever heard the expression , don't always believe what the papers says.!  well I am going to extend on this, don't always believe what the ''papers'' say , try using some common sense and science knowledge.

Likewise polarities repel each other, do you agree with that?

[JohnDuffield (OP)]

Likewise polarities repel each other, do you agree with that?

Yes I do. But two bodies attract one another, in line with F = G m₁m₂ / r˛. The m stands for mass, and the mass of a body is a measure of its energy content, as per Einstein’s E=mc˛ paper. There are no bodies that contain less than zero energy, just as there are no pencils less than zero inches long. Hence there is no gravitational repulsion. Nor is there any  runaway motion comprised of “a push that repels the positive mass from the negative mass, and a pull that attracts the negative mass”.   

[jeffreyH]

Ok John can you list some of the exact solutions to the Einstein field equations that have been found. I can check the answers for you if you like. Seeing as you are such an expert relativist. Oh and not to include the Schwarzschild or Kerr type solutions.

See the scholarpedia article by Malcolm MacCallum. It perhaps gives you what you're looking for:

http://www.scholarpedia.org/article/Exact_solutions_of_Einstein%27s_equations#Some_important_solutions

It took you only ten minutes to google that. That IS impressive.

[MichaelMD]

In my ether model for gravity described in my last post, an auric etheric zone between two solid bodies in space contracts the ether there. -As elemental ether units in the "auric zone" between the bodies resonate, their outward vibrations form more connections, producing an increase in the entrainments among the ether units, which contracts the ether between the bodies, compared to the ether outside the auric zone. -A key to this model is the idea that elemental units in the ether matrix resonate in a perfectly linear way (no spin, vectors, waves, or other non-linear mechanisms involved, only a linear vibrational mechanism between identical elemental matrix units.)

As I said in that post, an ether theorist like myself gets quite a different picture of gravity.