Section 3: Newton's Law of Universal Gravitation An underlying
theme in science is the idea of unification—the attempt to
explain seemingly disparate phenomena under the umbrella of a
common theoretical framework. The first major unification in
physics was Sir Isaac Newton's realization that the same force
that caused an apple to fall at the Earth's surface—gravity—was
also responsible for holding the Moon in orbit about the Earth.
This universal force would also act between the planets and the
Sun, providing a common explanation for both terrestrial and
astronomical phenomena. Figure 5: Newton's law of universal
gravitation. Source: © Blayne Heckel. More info Newton's law of
universal gravitation states that every two particles attract
one another with a force that is proportional to the product of
their masses and inversely proportional to the square of the
distance between them. The proportionality constant, denoted by
G, is called the universal gravitational constant. We can use it
to calculate the minute