“Bridges are thresholds to other realities, archetypal, primal symbols of shifting consciousness. They are passageways, conduits, and connectors that connote transitioning, crossing borders, and changing perspectives. Bridges span liminal (threshold) spaces between worlds, spaces I call nepantla, a Nahuatl word meaning tierra entre medio. Transformations occur in this in-between space, an unstable, unpredictable, precarious, always-in-transition space lacking clear boundaries. Nepantla es tierra desconocida, and living in this liminal zone means being in a constant state of displacement--an uncomfortable, even alarming feeling. Most of us dwell in nepantla so much of the time it’s become a sort of “home.””

Our Final Hour: A Scientist's Warning (2003) <!-- | date = 2003-03-18
Context: Once the threshold is crossed when there is a self-sustaining level of life in space, then life's long-range future will be secure irrespective of any of the risks on Earth (with the single exception of the catastrophic destruction of space itself). Will this happen before our technical civilisation disintegrates, leaving this as a might-have-been? Will the self-sustaining space communities be established before a catastrophe sets back the prospect of any such enterprise, perhaps foreclosing it for ever? We live at what could be a defining moment for the cosmos, not just for our Earth.

Source: 1940's, A New Realism', 1943-1945, p. 18

Source: The Witch Of Portobello

Source: The People of Paper

Henri Lefebvre (1991; original French edition, 1974), as quoted in Fainstein The City Builders (2001), p. 272
Other quotes

As quoted in Turning Numbers into Knowledge: Mastering the Art of Problem Solving (2001) by Jonathan G. Koomey, p. 96; since at least 2010 similar statements are also sometimes attributed to Mozart, and a similar remark, apparently one of Ben Jonson, is quoted in "Notes to Cynthia's Revels, in The Works of Ben Jonson: With Notes Critical and Explanatory, and a Biographical Memoir (1875), edited by William Gifford, Vol. 2, in notes to p. 223, on p. 551: Division, in music, is "the space between the notes of music, or the dividing of the tones."
Unsourced variants:
Music is the silence between the notes.
The music is not in the notes, but in the silence between.
The music is not in the notes, but in the silence between them.
Variant: Music is the space between the notes.

Source: The Long Goodbye

As quoted in Transnational Perspectives on Graphic Narratives https://books.google.com/books?isbn=1441185755 p. 5