Is tangibility, the ability to touch something the only criteria by which we judge whether a phenomenon is a property or characteristic of the physical world?
Is a mountain a tangible thing? Where exactly does the mountain begin and the valley end? When exactly is a mountain a mountain and not a hill?
I also appreciate your use of the word ethereal:
ethereal - adjective ethe·re·al i-ˈthir-ē-əl
1a: of or relating to the regions beyond the earth
b: CELESTIAL, HEAVENLY
c: UNWORLDLY, SPIRITUAL
2a: lacking material substance : IMMATERIAL, INTANGIBLE
b: marked by unusual delicacy or refinement
this smallest, most ethereal, and daintiest of birds-William Beebe
c: suggesting the heavens or heaven
3: relating to, containing, or resembling a chemical ether
I suppose it is meant to suggest that if I can accept the intangible reality of space and time I should be equally open to the intangible spiritual, heavenly, and unworldly.
The difference, however, lies in what can be experienced. Without experience, they simply remain inventions of the mind.