There IS a line on the horizon

I can't believe I never caught the second pun (I am no Keltic Ken) on the cover of U2's upcoming"No Line on the Horizon"
(the first being that there is a line on the horizon on the photo; the second
is a "visual pun," being that neither of the two lines of the superimposed equals sign are on the horizon, they teasingly straddle it)
until reading Beth's comments on her blog post quoted below.

That same post is hugely helpful:

Theologian Steve Harmon, author of U2: Unexpected Prophets, makes some points about the cover of No Line that I think deserve to be pulled out for everyone to see. I was completely delighted, for exactly the reasoning Harmon articulates so well here, that the Sugimoto image with no line (the photo rumored to be the album cover) turned out to be passed over for an image with a line:

The equals sign, with one bar in the "heaven" portion and one bar in the "earth" portion, suggests something like "your kingdom come, your will be done, on earth as it is in heaven." But in this particular Sugimoto image, there IS still a line on the horizon. Earth is not yet heaven, yet we pray and work for the day when things will fully be on earth as they are in heaven -- when heaven and earth will be indistinguishable, and there will be no line on the horizon. Once again, an "already"/"not yet" eschatology, with the emphasis on the "not yet."

I understood the attraction of the image of the sea blurring into the sky, because I know so much of U2's work is about the longing for and celebration of foretastes of that experience of transcendence. (One of the earliest articles I read about U2 in the 80s, which I have never been able to trace, characterized them with the phrase "blood lust for the infinite," which has always stuck with me.) But it struck me as lacking complete honesty for a U2 image to represent the blending of already/not yet as accomplished. Upon seeing the real cover, I immediately found the image we've ended up with far preferable, and more faithful to the band's consistently eschatologically-shaped vision of reality, and I'm grateful for Steve's putting the reasons why into words here.
-Beth, U2 Sermons

Also, here are the artist's comments on one of the original photos:

Water and air. So very commonplace are these substances, they hardly attract attention―and yet they vouchsafe our very existence. The beginnings of life are shrouded in myth: Let there water and air. Living phenomena spontaneously generated from water and air in the presence of light, though that could just as easily suggest random coincidence as a Deity. Let's just say that there happened to be a planet with water and air in our solar system, and moreover at precisely the right distance from the sun for the temperatures required to coax forth life. While hardly inconceivable that at least one such planet should exist in the vast reaches of universe, we search in vain for another similar example. Mystery of mysteries, water and air are right there before us in the sea. Every time I view the sea, I feel a calming sense of security, as if visiting my ancestral home; I embark on a voyage of seeing. - Hiroshi Sugimoto http://www.sugimotohiroshi.com/seascape.html