The effect of gravity i.e. the attraction between two macro physical objects is a fact. On the earth, all free falling objects is due to gravity. Newton characterized gravity as a force and derived his law of gravitation. However, he had reservations wrt how there could be “action at a distance”.
From the wiki on Newton’s law of gravitation
“That one body may act upon another at a distance through a vacuum without the mediation of anything else, by and through which their action and force may be conveyed from one another, is to me so great an absurdity that, I believe, no man who has in philosophic matters a competent faculty of thinking could ever fall into it.”
Einstein came up with a solution:
In general relativity, the gravitational force is a fictitious force due to the curvature of spacetime, because the gravitational acceleration of a body in free fall is due to its world line being a geodesic of spacetime.
However, even though if one can conceive of massive objects like planets or stars doing that, it still remains quite ridiculous for small objects like apples to fall just like that, notwithstanding Einsteinian physics. In that respect, Newton’s gravitational force makes more sense but “action at a distance” is clearly absurd. How about mediating gravitons, the Higgs boson etc. Very esoteric indeed.
OTOH, in describing micro quantum objects, QM do not consider gravity at all.
Apparently, QM is incompatible with general relativity because one intractable issue is gravity.
Does quantum gravity exist or is there no gravity at the quantum scale and if so, why is it so?
What is gravity and why does it do what it does in the macro realm?
According to Erik Verlinde, gravity is an emerging “entropic force” on the macro scale.
From the wiki on entropic gravity
Entropic gravity is a hypothesis in modern physics that describes gravity as an entropic force; not a fundamental interaction mediated by a particle, but a probabilistic consequence of physical systems’ tendency to increase their entropy.
Also, from this article at the
What is gravity?
Forget curved space or the spooky attraction at a distance described by Isaac Newton’s equations well enough to let us navigate the rings of Saturn, the force we call gravity is simply a byproduct of nature’s propensity to maximize disorder.
Einstein’s equations of general relativity are fundamentally about thermodynamics:
In a provocative calculation in 1995, Ted Jacobson, a theorist from the University of Maryland, showed that given a few of these holographic ideas, Einstein’s equations of general relativity are just a another way of stating the laws of thermodynamics.
His concept of gravity is interesting and controversial. Nevertheless, from the wiki HERE
It appears that Verlinde’s approach to explaining gravity leads naturally to the correct observed strength of dark energy. In June 2011, he was awarded the prestigious Spinoza Prize with a 2.5 million euro grant for this work, including his paper.
If gravity is an emerging macro entropic force and is deterministic, the question which arises is, at the micro level where quantum objects interact randomly and indeterministically, is there any quantum gravity at all?