**The Physical Mechanism of Gravity - The Spatiotemporal Ground-State**

This is an attempt to explain the physical mechanism behind the gravitational interaction and how the knowledge of this mechanism will help understand a wide range of observational data. It will be shown that this mechanism provides the key to many problem in physics, one of which explains why gravitating systems remain stable for time-scales exceeding several billion years, i.e., why objects remain in quasi-stable orbits without collapsing towards the center of mass of the system under consideration, and, why objects tend not to escape the gravitational potential well of the system: the topic of the thread linked below.

Another objective of this study is to initiate quantitative studies on the rather unique features of the cosmological constant that appear to be an extension of Einstein’s general principle of relativity, GR. New to the overall picture here is the exposition of the boundary condition (the local minima) operational in GR, something the function or mechanism of which was missing from both GR and Newtonian gravitation (viz the physical mechanism responsible for gravity) prior to this paper, yet observationally had been present all along, and without the need for fine-tuning (an exact cancelation of gravity with centrifugal force, dark matter or dark energy).

The main intention of this work is to elucidate (to describe) the physical mechanism behind the gravitational interaction. At the same time, the physical mechanism for Einstein’s cosmological constant (lambda: originally identified by Einstein to provide static solutions to the field equations of GR) is also illuminated in physical terms. At the same time, the postulated physical mechanism describes a 4-dimensional surface that induces a natural symmetry (one of the properties of the vacuum state) that enforces the importance of a vanishing gravitational field (in juxtaposition with gravity itself) while remaining consistent with physical laws.

The original role assigned to lambda of allowing static homogeneous solutions to Einstein's field equations in the presence of matter can be preserved. By fixing the value of lambda precisely to zero the fine-tuning problem vanishes, along with the unattractive superfluous nature of the parameterized mathematical term (now embedded in modern cosmology). It will be shown that lambda is can be described a geometric property of spacetime curvature (not a measure of the energy density of the vacuum or negative pressure), a boundary condition, where the cosmological constant describes the properties of a zero curvature (relative 'gravity-free') state of the vacuum.

The boundary proposal for general relativity does not invalidate or contradict Einstein’s general principle, nor does it spawn the break down of GR somewhere behind an unobservable event horizon. The boundary condition is primordial if we are to understand gravity in relation to the other so-called forces of nature, in relation to quantum mechanics. The boundary condition is an extension of GR that needs to be incorporated if resolution is to be made in the understanding of gravity and it’s relation not just to massive bodies but also to empty space as a generator of stability, equilibrium and symmetry (not of the field surrounding bodies but in the relation between curvature and flatness), rather than as a fictitious medium or intermediate state (or even ‘nothing’) halfway between two extremes capable of exponential expansion.

The intention of this thread is to present a working hypothesis in order initiate the understanding of the mechanism involved in the formation of systems and stability generation of systems bounded under the sole influence of gravity (e.g., 2-body systems, 3-body systems, N-body systems such as the solar system, but too, the Galaxy and so on up to superclusters and indeed to the formation, stability and longevity of the entire universe).

Ultimately, too, the understanding of lambda (its value, its properties) in relation to gravity itself (via the physical mechanism proposed here) is central to the unification of general relativity and quantum theory, and thus to the understanding of the ‘origin’ and evolution of the universe (and too, of conscious life itself), as well as many other related aspects of physics.

For an introductory discussion regarding the mechanism responsible for the maintenance of stability (equilibrium) of self-bounded gravitating systems refer to the thread Dynamic Equilibrium of the Universe and Subsystems. There, it was introduced the relation to this concept via a discussion on the gravitational potential energy at Lagrange points (at L1 in particular). Some of those ideas will be recapped here for convenience (at least those dealing with equilibrium), including the change that had to be made regarding the value of potential energy at Lagrange points, whereby it is the value of field curvature (the local minima) which is fundamental, as opposed to the global minima (at infinity).

There, it had been argued by Coldcreation that there is a fine-tuning problem intrinsic in the standard view, in which an exact cancelation between the gravitation tendency to attract ('inward') and a centrifugal force (in an 'outward' direction) is required by the standard model. This problem has been known since (at least) the time of Newton, and has been left unexplained.

It had been argued, too, by Coldcreation, that something else has to be responsible for the observed equilibrium: something intrinsic in nature responsible for the apparent stability. That something is directly related to the physical mechanism of gravity.

Here it will be elaborated upon, how Lagrange points (L1, L2 and possibly L3) possess the same characteristics that describe Einstein's cosmological term, lambda, and are therefor possibly related to the same phenomenon (both have characteristic geometric properties consistent with 'empty' field-free space).

A series of significant and cost-effective tests are proposed (and can also be viewed in the above link) that should offer empirical evidence which will enable us to distinguish between various models. Indeed, that empirical data (in addition to verifying or falsifying the claims made here) will provide the answers to several crucial and profound questions - not least of which is the identification of the physical mechanism for gravity.

I chose the Astronomy and Cosmology section to post, rather than Physics and Mathematics, for the reason that observations needed to test such a description of nature should be carried out in the solar system, and too, because much of the observational data that does not concord with the standard model (e.g., galactic rotation curves) are the domain of astronomy. Finally, I chose not to post this thread in the Alternative Theory section of Hypography, as it is not really an alternative model, but one that explains phenomena that did not, prior to this study, address the issues at stake without the introduction of elements that 'themselves' are at the very fringe of physics, e.g., nonbaryonic cold-dark matter, dark energy, and so on. There is no new physics in this interpretation of observational data.

Key words:

*Cosmology, gravitational mechanism, spacetime curvature, cosmological constant, lambda, celestial mechanics, Lagrange points, quasi-stable equilibrium configurations, the vacuum, Minkowski space, gravitational potential energy*.

CC