K. Tollefson

Dark matter is like an invisible glue that holds galaxies together. It emits no light, but if its particles collide, gamma rays can flash. Scientists hunted for such flashes in dwarf galaxies — small stellar clusters with lots of dark matter and almost no ordinary matter.

Earth is a closed book for those accustomed to leafing through pages with light. But to neutrinos, the invisible particles born in cosmic rays and barely remembering the prediction of Pauli, our planet is a braille script: each kilometer of depth presses its relief into their…

For almost a century, seismology has been the planet’s chief X-ray, probing the interior through elastic waves. But neutrinos, ghost particles predicted by Wolfgang Pauli, offer a different perspective.

Deep beneath the ice of the South Pole, nearly two and a half kilometers down, an unusual telescope is at work. It is not pointed at the sky but through the Earth. Its quarry: neutrinos, nearly elusive particles that pass through planets and stars without interacting with anything.