A telescope that looks at the earth.
This is probably the coolest astrophysics experiment I’ve come across, a telescope that has all it’s detectors pointed towards the centre of the earth.
The IceCube Neutrino Observatory is an experiment in Antarctica, buried between 1450 and 2450 meters below the surface, in solid optically clear (due to the pressure) ice are over 4000 photon detectors. The detectors are on 80 strings, each of which is lowered down a bore hole (imagine dropping one!) which will then be frozen in place for around 25,000 years. The holes take about 48 hours to ‘drill’ which is done using hot water, and 200,000 gallons of ice are melted for each one! But why?
Well to look for neutrinos of course! It can be burried and the detectors pointing to detect things coming through the earth because the scattering cross section of a neutrino is TINY really TINY so the earth just wont stop that many of them, but once they are stopped what they do is energise an electron to the point that it’s moving faster than the speed of light in ice (which is less than c).
Objects moving faster than the speed of light in a material (again slower than c) radiate, in a process called Čerenkov radiation, the photons which are given out by electrons within the IceCube array are detected, and then using some clever geometry the direction and energy of the electron and then the neutrino can be found. So we have a directional neutrino telescope! Really quite cool!
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May 4th, 2008 at 9:55 pm
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June 9th, 2008 at 6:48 pm
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