When we find home base in our minds, we've found a different orienting horizon. In contrast to the horizontal one, this one seems to be vertical. Rather than extending as far as our eyes can see, this alternative horizon crosses that horizontal line.
Our popular culture includes numerous reminders of this other horizon. There's a band "Vertical Horizon". There are those Mountain Dew commercials to "get vertical" that speak to surf, snow and skateboarders pursuit of "grabbing some air" and "getting some hang time". There's the wireless company named with a concatenation of vertical horizon: Verizon. My favorite is Brian Griffin's cover art for Howard Jones 1989 album: cross that line.
The vertical horizon intersects space time rather than orienting those three dimensions of picture planes with depth. The vertical horizon suggests a fourth dimension that encompasses the familiar three. It shows us the orientation toward an endless, timeless moment. The vertical horizon reveals right now to be eternity.