Complex Numbers

Cave In

Did my early voting today, so I can spend Election Day doing more important things, like drinking.

Unrelated to that or, well, anything else, really, is this Atlas Obscura article featuring an obscure city in an obscure state:

    The Strange Heat Island Lurking Beneath Minneapolis  
An urban explorer ventured deep below downtown in search of Schieks Cave. What he found changed science.

Greg Brick knew it was there, lurking beneath his city, hidden within the Minneapolis water and sewer system: an enticing geologic anomaly called Schieks Cave.

That sort of thing fascinates me, but I can't be arsed to do all the work or break the laws necessary to explore for myself.

When Brick arrived at the cave, he shined a flashlight into the thick darkness of the city’s underbelly. He found not just the natural void but also concrete walls that previous generations of civil engineers had built to support the natural structure.

If those civil engineers were anything like me, they wrote something like "put a concrete wall here" on a map, and some minimum-wage temps did the actual work.

The water was about 20 degrees hotter than it was supposed to be. It was more like the groundwater of Mississippi than that of Minneapolis. Something was warming the water beneath his city.

Well, clearly, that's because Minneapolis is actually a gateway to Hell.

[The cave's] discovery in 1904 by a city sewer engineer was initially kept secret lest the public fear Minneapolis had been built on unstable ground.

Apparently, it was, else generations of civil engineers wouldn't have specced out concrete support walls in the cave.

He finally had a way to access the cave—but there was another problem. Along the route, the raw sewage poured from shafts overhead, shooting bacteria into the air as it splashed down and creating what’s politely known as “coliform aerosols.” Unsurprisingly, Brick got sick.

Another reason for us civil engineers to stay at our desks.

In 2008, a separate team from the University of Minnesota had predicted that heat from Minneapolis’s urban surface was conducting itself deep underground, heating the groundwater there like a metropolitan microwave.

As the article notes, this turned out to be the correct explanation, not the "gateway to Hell" one. Much to my disappointment.

But it’s not all bad news: Canadian and European researchers recently suggested recycling underground heat and using it as a low-carbon way to heat homes, while also cooling the groundwater back down to normal temps.

I hope their "suggestion" included exactly how to do that.

Now, from the headline, I was expecting some discovery of dark matter or a violation of the Second Law of Thermodynamics or whatever. But no. Still, at least it's not boring.