The Quest for the Atomic Force

His father died during his mother?s pregnancy. Rejected by her as a boy,
he was packed off to boarding school when she remarried. He himself never
married, but in middle age he formed an intense relationship with a much
younger man, a relationship that he terminated when he underwent a
psychotic break. Following his early scientific successes, he spent the rest of
his professional life mostly in frustration over his inability to unlock the
secrets of alchemy.
The man being described is Isaac Newton, but not the triumphant
Newton of the standard textbook hagiography. Why dwell on the sad side
of his life? To the modern science educator, Newton?s lifelong obsession
with alchemy may seem an embarrassment, a distraction from his main
achievement, which was the creation the modern science of mechanics. To
Newton, however, his alchemical researches were naturally related to his investigations of force and motion. What was radical about Newton?s
analysis of motion was its universality: it succeeded in describing both the
heavens and the earth with the same equations, whereas previously it had
been assumed that the sun, moon, stars, and planets were fundamentally
different from earthly objects. But Newton realized that if science was to
describe all of nature in a unified way, it was not enough to unite the
human scale with the scale of the universe: he would not be satisfied until
he fit the microscopic universe into the picture as well.
It should not surprise us that Newton failed. Although he was a firm
believer in the existence of atoms, there was no more experimental evidence
for their existence than there had been when the ancient Greeks first posited
them on purely philosophical grounds. Alchemy labored under a tradition
of secrecy and mysticism. Newton had already almost single-handedly
transformed the fuzzyheaded field of ?natural philosophy? into something
we would recognize as the modern science of physics, and it would be
unjust to criticize him for failing to change alchemy into modern chemistry
as well. The time was not ripe. The microscope was a new invention, and it
was cutting-edge science when Newton?s contemporary Hooke discovered
that living things were made out of cells.

Newton?s quest
Nevertheless it will be instructive to pick up Newton?s train of thought
and see where it leads us with the benefit of modern hindsight. In uniting
the human and cosmic scales of existence, he had reimagined both as stages
on which the actors were objects (trees and houses, planets and stars) that
interacted through attractions and repulsions. He was already convinced
that the objects inhabiting the microworld were atoms, so it remained only
to determine what kinds of forces they exerted on each other.
His next insight was no less brilliant for his inability to bring it to
fruition. He realized that the many human-scale forces ? friction, sticky
forces, the normal forces that keep objects from occupying the same space,
and so on ? must all simply be expressions of a more fundamental force
acting between atoms. Tape sticks to paper because the atoms in the tape
attract the atoms in the paper. My house doesn?t fall to the center of the
earth because its atoms repel the atoms of the dirt under it.
Here he got stuck. It was tempting to think that the atomic force was a
form of gravity, which he knew to be universal, fundamental, and mathematically
simple. Gravity, however, is always attractive, so how could he
use it to explain the existence of both attractive and repulsive atomic forces?
The gravitational force between objects of ordinary size is also extremely small, which is why we never notice cars and houses attracting us gravitationally.
It would be hard to understand how gravity could be responsible
for anything as vigorous as the beating of a heart or the explosion of
gunpowder. Newton went on to write a million words of alchemical notes
filled with
speculation about some other force, perhaps a ?divine force? or
?vegetative force? that would for example be carried by the sperm to the
egg.

Source:Newtonian Physics-Benjamin Crowell