The most common relative directions are left, right, forward(s), backward(s), up, and down. No absolute direction corresponds to any of the relative directions. This is a consequence of the translational invariance of the laws of physics: nature, loosely speaking, behaves the same no matter what direction one moves. As demonstrated by the Michelson-Morley null result, there is no absolute inertial frame of reference. There are definite relationships between the relative directions, however. Left and right, forward and backward, and up and down are three pairs of complementary directions, each pair orthogonal to both of the others. Relative directions are also known as egocentric coordinates.
Famous quotes containing the words relative and/or direction:
“Are not all finite beings better pleased with motions relative than absolute?”
—Henry David Thoreau (18171862)
“Exaggeration is in the course of things. Nature sends no creature, no man into the world, without adding a small excess of his proper quality. Given the planet, it is still necessary to add the impulse; so, to every creature nature added a little violence of direction in its proper path, a shove to put it on its way; in every instance, a slight generosity, a drop too much.”
—Ralph Waldo Emerson (18031882)