The South Pole neutrino detector that spans a cubic kilometer of Antarctic ice has observed high-energy neutrinos from outside our solar system. That spectacular announcement came from the IceCube team last year, based on three years of observation. “We still don’t know what we are seeing,” says principal investigator Francis Halzen of the University of Wisconsin–Madison. “The thing to do is get more events and figure out where they come from and what generates them.”

To that end, the IceCube team wants to increase the detector’s volume 5- to 10-fold to widen the net for spotting high-energy cosmic neutrinos. The main goal is to collect several hundred of the 1015-eV neutrinos per year. An expanded detector would also observe

a handful of 1018-eV neutrinos each year, says Halzen. “That’s not a large number, but they point to the source.”

IceCube’s sensitivity at higher energies would be...

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