<P> Quantum mechanics is a set of principles describing physical reality at the atomic level of matter (molecules and atoms) and the subatomic particles (electrons, protons, and even smaller particles). These descriptions include the simultaneous wave - like and particle - like behavior of both matter and radiation energy as described in the wave--particle duality . </P> <P> In classical mechanics, accurate measurements and predictions of the state of objects can be calculated, such as location and velocity . In the quantum mechanics, due to the Heisenberg uncertainty principle, the complete state of a subatomic particle, such as its location and velocity, cannot be simultaneously determined . </P> <P> In addition to describing the motion of atomic level phenomena, quantum mechanics is useful in understanding some large scale phenomenon such as superfluidity, superconductivity, and biological systems, including the function of smell receptors and the structures of proteins . </P> <P> Humans, like all known things in the universe, are in constant motion, however, aside from obvious movements of the various external body parts and locomotion, humans are in motion in a variety of ways which are more difficult to perceive . Many of these "imperceptible motions" are only perceivable with the help of special tools and careful observation . The larger scales of "imperceptible motions" are difficult for humans to perceive for two reasons: 1) Newton's laws of motion (particularly Inertia) which prevent humans from feeling motions of a mass to which they are connected, and 2) the lack of an obvious frame of reference which would allow individuals to easily see that they are moving . The smaller scales of these motions are too small for humans to sense . </P>

Who studied forces and the motion of objects