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7 DAY FORECAST
MOON
MERCURY
VENUS
MARS
JUPITER
SATURN
URANUS
NEPTUNE
KP 0
9
SWPC Ovation
SWPC WSA-ENLIL
THE DETECTOR
50,000 tons of ultra-pure water two-thirds of a mile under Mount Ikeno, watched by 11,129 light sensors on its walls. Since 1996; Nobel Prize 2015 for showing neutrinos have mass.
READING THE PICTURE
The big rectangle is the tank's wall unrolled flat, the two circles its top and bottom, the small drawing the outer veto. Each dot is one sensor, coloured by the light it caught: the scale runs along the bottom, in photo-electrons.
WHAT AN EVENT IS
A charged particle crossing the water faster than light does there throws a cone of blue Cherenkov light that lands on the wall as a ring. A cosmic-ray muon from above leaves a bright entry patch and a streak; a neutrino born inside the tank makes a single ring with nothing entering.
THE HEADER
Run and event numbers, the event time in Japan, the triggers that fired (LE / HE / SLE for low, high and super-low energy, OD for the outer veto), and the hits and total light in the inner (ID) and outer (OD) detector.
HOW OFTEN
About 30 atmospheric neutrinos a day against cosmic-ray muons at two a second. This display shows one event every ~20 s, chosen at random, so it is nearly always a muon.
THE SUPERNOVA WATCH
SNEWS, the supernova alarm eight detectors feed (IceCube, China’s new JUNO, KamLAND and SNO+ among them; Super-K raises its own), has never fired since it went automated in 2005. The next galactic supernova's neutrinos arrive hours before its light.
ONE EVENT EVERY 20 SECONDS · A RANDOM SAMPLE OF WHAT THE DETECTOR JUST SAW