BREMEN — The horizon is the final frontier, what separates the sky from the earth. Below the horizontal line live people, and above it are the gods and the ether, the sun, moon and stars, and the ozone hole and greenhouse gases. As long as the horizon can be seen, the sun disappears behind it in the evening but rises again in the morning on the other side, and the sky is not falling on anyone's head. The sky remains the sky.

The cleverest and most beautiful song about the line between the two elements comes from the Berlin band Knorkator. It is called How Far is it to the Horizon (Pythagore) and happily sings the math to calculate how far the horizon is: "The distance is a / The radius is b / the center to the head is the side c / let's take the theorem of Pythagore: a² + b² = c² / Earth's radius b / Measures approximately 6,378,000 meters / C = 6,378,000 and 1.70 meters / Let's look at the squares / And their difference is/ 21,680,000 / And the square root is / 4,650 meters!"

The horizon is quite close, in other words. And it's for that very reason that historian Georg Skalecki — who heads the Bremen State Office for the Preservation of Monuments — is so concerned these days about horizontverschmutzung, a relatively new terms that translates in English as "horizon pollution."

The horizon is sacred.

Skalecki is particularly opposed to a plan by architect Daniel Libeskind to erect four towers along the edge of Bremen's city center, in the area around the bank. The four towers are supposed to honor the world-famous Town Musicians of Bremen, of the classic Brothers Grimm fairy tale.

The highest building on the city's horizon is the centuries-old, 98-meter-tall cathedral. One of the four new towers should not be quite as tall, but would have a wider top. The architect wants to broaden Bremen's horizon, and is inspired by New York, where he is involved in the renovation of the World Trade Center.

Street in Bremen, Germany — Carlos Ibáñez

In Libeskind's opinion, Bremen should become a global trading metropolis again with office towers and hotels that are taller than wide. But the preservationist Georg Skalecki wants Bremen to remain Bremen, with its narrow but clean horizon.

Horizon pollution has become a common term in German since some huge white wind turbines were erected in the sea, affecting the landscape and the open view. The expression first appeared in written complaint by the mayor of Wangerooge, on the North Sea island of the same, opposed a wind farm that went into operation in 2017, despite being planned for 2008.

Horizon pollution is a more elegant way of saying "spoiling," as in spoiling the landscape. What is meant by the term is not only the disturbing shadows over the meadows, dead songbirds under the masts and the silence following the death of the bees. It means more. Because once it's been blocked from view, the horizon is longer the dominating expanse in Caspar David Friedrich's famous The Monk by the Sea painting, no longer the thing that makes the monk seem so meager.

The horizon is sacred, even when it's not a line, but rather the shape-shifting silhouette of a city. In Berlin, the skyline traces the contours of Prussian history. In Cologne it's marked by the unique Central Mosque. In Bremen, it's characterized by the cathedral towers.

Horizon pollution is a more elegant way of saying "spoiling."

Claude Lévi-Strauss, the well-traveled ethnologist, saw the horizon as an idea shared by all peoples: the horizontal stands for everything earthly and human, the vertical for the supernatural and the divine. Thus the steeples and other towers that men built to assure the longevity of their power.

Horizon pollution caused by wind engines makes people aware that they cannot do otherwise. That they must put the climate above it all so that the sky doesn't fall on their heads. Bu altering the horizon of Bremen, in contrast, would be a purely spiritual choice.

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