What is gravity? (Part 1 of 3)

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Aside from mathematical symbolism, what is gravity? Newton made no hypothesis, Einstein saw someone fall off a ladder (or some such) and heard that the victim didn't feel anything on the way down;** then developed general relativity, the mathematics of which all adherents know. Quantum theorists like to think of gravity as an exchange of particles, as with the other forces of nature. But the graviton remains hypothetical. Gravity is different. It is smaller, much smaller, than the other forces, so much so that there is a special name in physics "the hierarchy problem."

Of the grouping in this image, the rightmost represents gravity; gravity is not natural, it doesn't fit with the other forces, it doesn't fit into quantum theory, it just doesn't fit. Gravity is too small, OR TOO BIG. It can't mean that gravity is not as important as the others; everything resides in space and time, or spacetime; so to speak, it's the box everything else fits into.

Something happened about fourteen billion years ago that resulted in this:

which is typical of the large-scale structure representing the Universe. Space is empty of matter not only on the smaller scales, but more so on this scale; note the region labeled "Void." This region, and smaller versions in the picture, appears to be rather full of matter in this two-dimensional representation, but a three dimensional model would indicate an empty, often spherical, void. Such voids are the typical structural element in this sponge-like composite. The "Filament" label is a misnomer in three dimensions; it actually represents a shell about the "Void," as a shell would cover an egg, sometimes thousands of times thinner than the voids; this shell is composed of galactic superclusters. In turn galactic superclusters are composed of "groups or clusters of galaxies," the maximum astronomical unit that is gravitationally stable; the individual galaxies within such groups do not take part in the accelerated Hubble expansion; they move about within the group, but the group stays together, as it accelerates away from other such groups. This entire picture is expanding at a velocity that is increasing, as a common sponge under formation by expanding gas pressure, compressing the material aspects among the voids, making it appear the material aspects are experiencing mutual attraction (not the current consensus view) -- voids being primary, or motivators, and matter being secondary residue guided by the expanding voids.

Acceleration implies gravity, recalling the person falling from the ladder as the basis of general relativity, or, in Newtonian terms,

For small accelerations, as in the acceleration of the Universe,*** general relativity reduces to these Newtonian formulas. But there is still no clue of what gravity is. Or is there? The Universe is observed to be accelerating outward. This can imply that gravity is repulsive, and seated in the large-scale "Voids" of the above image. ^ Then, the Newtonian force arrows would have tails in the centers of the large-scale voids and heads pointing at the surrounding shells of galaxies, with an implicit semblance of the free parameter cosmological constant. Such fundamentally repulsive gravity seems to contradict about four hundred years of "experience." Experience? Experience within the confines of the Solar system. Once galaxies were scientifically observed, an embarrassing amount of mass seemed to be missing. The label given this apparently missing mass is "dark matter." *** Such "matter" seems to reside adjacent to galaxies, or, on the scale of the figure, within the "Filaments" and "Clusters" (better described as the intersection of three or more large-scale voids) as labeled. So called "dark energy" is said to reside in the large-scale Voids. The forces implied in these accelerated expanding voids appear to be compressing the galactic supercluster shells (again, labeled "Filaments" and "Clusters" in the image). Any given galaxy within these shells could be receiving incoming forces from all voids external to "clusters of galaxies," effectively from all directions. It might be that dark matter is dark energy at smaller scales, dark energy is accelerated expanding space, and gravity is ...

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* "Image credit and original caption. "In 1665, Cambridge University was closed because of the Great Plague and Newton returned home to Woolsthorpe, near Grantham, where his studies continued.

Years later he told a story that a falling apple in the orchard had prompted him to think about gravity, eventually published in his 1687 tome Principia."

-- https://www.bbc.com/news/uk-england-leicestershire-43385897

** Equivalence of gravity and acceleration.

*** Letters, Linkedin, Nov 30, 2021 https://www.dhirubhai.net/feed/update/urn:li:activity:6871519119221501954/

^ "Dark energy," or the "cosmological constant," are labels for an unknown, not an explanation of accelerated universal expansion.

Image: large-scale structure https://research.iac.es/proyecto/cosmolss/pages/en/research/cosmic-voids.php