The electromagnetic spectrum is comprised of visible and invisible light. Living in the world of appearance, virtually everything is perceived at the speed of light. But it is a representational reality. Beneath and beyond it all, is the Truth of Being, known directly. ...
Our ears are sufficiently sensitive that they're capable of differentiating between variations in sound equivalent to less than one-billionth of atmospheric pressure, and our brains have the ability to identify and memorize complex aural patterns [sources: GSU, CNRS]. That ability probably evolved ...