Is there a standard, agreed on definition of a Quantum in physics ? Also, I have picked up this information about a quantum on the internet (http://www.peterrussell.com/SG/Ch5.php" [Broken]). Does this correctly describe Plank's constant and its relation to a quantum ? "Although the amount of energy in a photon varies enormously, there is one aspect of the quantum that is fixed. Each and every quantum has a constant amount of action. Mathematicians define action as an object’s momentum multiplied by the distance it travels; or the object’s energy multiplied by the time it is traveling–the two are equivalent. The amount of "action" in a ball thrown across a football field, for example, would be greater than the same ball thrown half the distance. Double the ball’s mass, and you double the action. Or imagine yourself running at a constant rate of energy output. If you run for twice as long, there will be twice the action–which makes intuitive sense. The actual amount of action in a quantum is exceedingly small, about 0.00000000000000000000000000662618 erg.secs (or 6.62618x10-27 erg.secs in mathematical shorthand)–but it is always exactly the same amount. This is called Planck’s constant (after its discoverer). It is the second universal constant to emerge from modern physics. Like the first–the speed of light–it is a constant of light. Light always comes in identical units of action. "