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(^6) Gravity
Chapter Outline
6.1 Universal Law of Gravity
6.2 GRAVITY ANDSPACEPROBLEMS
Introduction
The Big Idea
Over 2500 years ago Aristotle proposed two laws of physics governing motion. One for ’Earthly bodies’ (objects
on Earth) that states objects naturally go in straight lines and one for ’Heavenly bodies’ (objects in space) that states
objects naturally go in circles. This idea held steady for 2,000 years until Isaac Newton, in a triumph of brilliance,
declared that there is one law of physics that governs motion and he unified “earthly” bodies and “heavenly” bodies
with the The Universal Law of Gravitation. Newton used the universal law of gravity to prove that the moon is
accelerating towards Earth just as a body on Earth is falling towards it. The acceleration of both the moon and
the object on Earth is calculated using the same formula. This theory is so well regarded that it has been used to
hypothesize the existence of black holes and dark matter, later verified by observation. The search to unify the laws
of physics into one theory continues today and is often referred to as the yet undiscovered Grand Unified Theory
(GUT).