“I have not as yet been able to deduce from phenomena the reason for these properties of gravity, and I do not feign hypotheses. For whatever is not deduced from the phenomena must be called a hypothesis; and hypotheses, whether metaphysical or physical, or based on occult qualities, or mechanical, have no place in experimental philosophy. In this experimental philosophy, propositions are deduced from the phenomena and are made general by induction. The impenetrability, mobility, and impetus of bodies and the laws of motion and law of gravity have been found by this method. And it is enough that gravity should really exist and should act according to the laws that we have set forth and should suffice for all the motions of the heavenly bodies and of our sea.”
— Sir Isaac Newton, Principia
Newton told us how gravity worked mathematically, but he could not tell us what it is or by what mechanism it operated.
“It is enough that gravity should exist and act according to laws,” he wrote.
He could not explain how one heavenly body could be affected by and affect other bodies, yet he did have a way to explain the observations of their motions that worked quite well.
Until Einstein’s proposals, there was no better way to explain the action of gravity than just to say “there it is, and here’s the math that proves it.” Even Einstein was bothered, however, by what he called “spooky action at a distance.”
Gravity is considered the weakest force in Nature, yet it can result in some of the most powerful objects we know of, called black holes.
Physicists today are still searching for a unified theory of gravity.
GRAVITY IN THE MIND OF GOD
”that My weakest force
ironically becomes the strongest.
The meek shall inherit, over due course –
the last become first, the shortest, longest.
“So gravity, most obvious, shall be
the greatest ever unsolved mystery
which, though its effects everyone can see,
can’t be described satisfactorily –
a force that’s both uniform and mundane,
predictable yet able to allude
a simple explanation that sounds sane
of its ever attractive attitude.
“And action at a distance? Let men try
to come to terms with what they most deny.”