The Cosmic Harp

For my final project for Mechanisms and Things that Move and Design Frontiers in Biology and Materiality, I would like to create a Cosmic Harp, as instrument that detects cosmic events and transforms them into music in real time.

High energy cosmic rays originating from the depths of outerspace bombard our planet’s atmosphere, producing particles that cascade to earth at relativistic speeds. One of the most abundant and energetic of such secondary cosmic particles is the muon.  Muons are unstable particles with lifetimes that should be too short to allow them to make it from the upper atmosphere to the Earth’s surface before decay.

However, because a muon originating from a high energy cosmic event travels at a speed approaching that of light as it descends to Earth, the effects of special relativity come into play.

From the viewpoint of the Earth, because of the muon’s speed: time “dialates”, the lifetime of the muon is extended, and the muon is able to reach the surface of the Earth. In fact, about 10,000 muons per a square meter, cascade to Earth every minute.

Muon Detectors

There are many ways to detect muons: cloud chambers, scintillators,… To the left is the muon detector (spectrometer) used to detect the muons created by the high energy proton annihilation for ATLAS at the LHC.

For my Design Frontiers in Biology and Materiality midterm, I investigated ways to make a, comparably, affordable muon detector. The muon detection I am most familiar with, uses a plastic scintillator. When a high energy particle hits the “scintillating” material, light is emitted.  A photomultiplier tube, utilizing the photoelectric effect, detects the photon and transmits a signal. To eliminate noise, two scintillator setups are used and the event is only recorded if there is a simultaneous hit.

Making a scintillator set up affordable requires either scrounging physics department junk or some freakishly good luck on ebay to acquire the most expensive parts: the appropriate and functioning photomultiplier tubes and their bases.  Even if these parts were readily available, the use of such a detector to create a varying or compelling sound output (other than single note percussion) is limited. And, creating more than one of such a set up, would be extraordinarily expensive.

I scratched the scintillator idea and investigated other muon detecting contraptions and have (at least temporarily) decided to use Geiger tubes as they are cheap and easy to acquire. In a Geiger Tube, there is a strong electric field created by a voltage difference between two electrodes on either side of the tube.  The tube is filled with gas that is ionized when a radioactive particle passes through. The result is a pulse that can be detected with monitoring equipment. As in the case of the scintillator set up, in order to make sure the radioactive particle detected is a muon, two Geiger tubes are stacked vertically and a count is only made if there is a coincidence.

Simple One-Stringed “Harp” Mechanism (first iteration)

With the limited amount of time before final presentation time, I thought I’d focus first on completing a simplified version of this concept: connecting a single detector to a single string and testing it’s rate on the ITP floor.