SKADI
\nDeep Ice Neutrino Observatory
\n \nA cubic kilometre of glacial ice, drilled, instrumented, and listening for the faintest light in the universe.
\ndepth 0120 m
\nThe clearest solid on Earth
\nAt the surface, snow. A hundred and twenty metres down, the weight of centuries has pressed it into glass. Below 1,400 metres the trapped air is gone, squeezed into the crystal itself, and the ice becomes the clearest solid on Earth: a photon can travel a hundred metres before anything touches it.
\nWe did not pour a detector. We found one, ninety thousand years old, and moved in.
\ndepth 1450 m
\n312 strings. 18,720 eyes.
\nEach string descends through a hot-water borehole and freezes into place carrying 60 optical modules: glass spheres rated to the weight of two and a half kilometres of ice, each able to register a single photon.
\nWhen a neutrino interacts nearby, the charged particle it produces outruns light in the ice and drags a cone of blue Cherenkov radiation behind it. The array reads the cone's arrival nanosecond by nanosecond and reconstructs where it came from, to within half a degree.
\n- \n
- Instrumented volume
- 1.02 km³
- Strings
- 312
- Optical modules
- 18,720
- Depth band
- 1,450 – 2,450 m
- Timing resolution
- 1.7 ns
depth 1950 m
\nLast night, read from below
\nSkadi records around 275 neutrino candidates a day. Most are born in our own atmosphere. A few each month are not, and those are the ones worth the drilling: messengers from blazars, tidal disruptions, and places that do not have names yet.
\n| time | energy | zenith | class |
|---|
depth 2200 m
\nThe only honest messenger
\nLight scatters. Charged particles spiral in magnetic fields and forget where they started. A neutrino crosses the universe in a straight line, through gas, dust, and entire galaxies, and arrives carrying the address of whatever made it.
\nIt also, almost always, leaves without a word. A hundred billion neutrinos pass through your thumbnail every second; the ice catches a handful a day. Skadi exists to be watching when one of them flinches.
\ndepth 2450 m
\nBedrock
\nThe drill stopped here on 14 January 2031. Above this point: ninety thousand years of compressed sky, and the largest telescope ever buried by hand.
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