Introduction to LIGO & Gravitational Waves
Newton, Einstein and Gravitational Waves
Title page to Newton's Philosophiæ Naturalis Principia
Mathematica was published in 5 July 1687 and contained the first
statement of Universal Gravitation.
 |
Many people are familiar with the
story of "Newton's Apple" - while
sitting under a tree one day, Newton observed an apple falling in the
distance and realized the moon he saw in the sky orbits the Earth
because of the same force that made the apple fall. This force is
gravity, and Newton recognized that gravity acts over distances without
physical contact - after all, nothing was touching that famous
apple to
make it fall. Masses feel gravitational force because every mass
in the universe has its own gravitational field, which adds together
with all of the other fields in the universe. According to
Newton's theory of gravity, when a mass changes position, the
entire
gravitational field throughout the universe changes instantaneously,
and the resultant gravitational forces are instantly changed
accordingly.
But Einstein's Theory of General Relativity - the most
commonly accepted
description of gravity - asserts that no information can travel
faster
than the speed of light, including information on the positions of mass
in the universe, which is communicated through the gravitational
field. General Relativity predicts that a change in gravitational
field will travel through the universe at the speed of light. It
is exactly these changes in gravitational field that are gravitational
waves.
