Homestake mine in Lead, SD.
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I stopped by Homestake Gold Mine in Lead, South Dakota on my 1991 bike trip across USA. 

Said to be deepest mine in North America. 

The thing that interested me most was the neutrino telescope, buried deep in the mine.

The telescope is no longer in service, but more have taken it's place in other parts of the world.  It was a pioneer.

Why put the telescope down in a mine?  Aren't telescopes supposed to look up to the stars?

Neutrinos are tiny particles that can pass through matter with ease.  They are part of a shower of cosmic particles that bombard Earth from space. 

To see the neutrino, it is a good idea to filter out the other particles.  Filter them out so that only neutrinos are "in the room" so to speak.  Neutrinos are the only particle that can travel through all those layers of rock to the bottom of the mine.

With the other particles are filtered out, it is easier to detect the neutrino.  This is sort of like filtering out the static on your radio to hear a faint signal. 

We can learn many things about the Sun, stars and the universe if we can study the hard to detect neutrinos.  

In 2001, the Lead Gold Mine was closed.  It basically ran out of gold.

Update.
New use:  Looking for Dark Matter.  See this great 2015 video from NPR Science Friday. 

Now there are plans to develop an underground science lab. 

Looking for dark matter at Homestake Mine means the town of Lead can sort of become a "science town."   This could revitalize the mine for a new use.

A neighboring town, named Deadwood, SD., has already found it's "post mining" future in gambling and tourism.  Maybe Lead will develop an economy based on science?  It's more interesting than gambling as far as I'm concerned.

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