I'm not familiar with all of the laws of the physical universe (and not to belittle your question at all) but we do seem to be psychologically affected by sound waves, light waves, biological matter (matter in general, for that matter) - all three of which (and I'm sure there are more) humans, since they began to notice patterns, have experimented with manipulating, recreating, destroying and creating new ones... sometimes in the name of science, sometimes in the name of art... are we back on that right/left brain theory again?

Jackie - The 2 K sprinter, at the end of his race, doesn't experience fatigue like the feeling I had yesterday of being emotionally drained (a friend died on the anniversary of my fathers death). These two feelings are clearly different, even if I do use the same word "fatigue" to describe them. One mental and one physical.