Backscatter
Experiments with a Tenuous Link to Radiation Protection
The Pitch Drop Experiment holds the Guinness World Record for the longestrunning laboratory experiment . It demonstrates the fluidity and high viscosity of pitch , a derivative of coal tar that is the world ' s thickest known fluid .
In 1927 Prof Thomas Parnell , a physicist at the University of Queensland , heated a sample of pitch and poured it into a glass funnel with a sealed stem . He allowed the pitch to cool and settle for three years and then , in 1930 , he cut the funnel ' s stem .
Since then , the pitch has slowly dripped out of the funnel - so slowly that it took eight years for the first drop to fall , and more than 40 years for another five to follow . To date only nine drops have fallen - the last drop being in April 2014 - and the expectation is that the next one will fall sometime in the 2020s .
The experiment was set up as a demonstration and is not kept under special environmental conditions so the rate of flow of the pitch varies with seasonal changes in temperature .
In the 97 years since the pitch has been dripping , various glitches have prevented anyone from seeing a drop fall . If you ' re reading this – it could be you ! See the experiment for yourself at the live videostream .
Tenuous link : although pitch is not radioactive , it is similar to pitchblende ( uranium ore )
The Half-Life of Teaspoons
Objectives To determine the overall rate of loss of workplace teaspoons and whether attrition and displacement are correlated with the relative value of the teaspoons or type of tearoom .
Setting Research institute employing about 140 people .
Subjects 70 discreetly numbered teaspoons placed in tearooms around the institute and observed weekly over five months .
Main outcome measures incidence of teaspoon loss per 100 teaspoon years and teaspoon half-life .
Results 56 ( 80 %) of the 70 teaspoons disappeared during the study . The half-life of the teaspoons was 81 days . The half-life of teaspoons in communal tearooms ( 42 days ) was significantly shorter than for those in rooms associated with particular research groups ( 77 days ). The rate of loss was not influenced by the teaspoons ' value . The incidence of teaspoon loss over the period of observation was 360.62 per 100 teaspoon years . At this rate , an estimated 250 teaspoons would need to be purchased annually to maintain a practical institute-wide population of 70 teaspoons .
Conclusions The loss of workplace teaspoons was rapid , showing that their availability , and hence office culture in general , is constantly threatened .
Published in the British Medical Journal , 2005 ( BMJ2005 ; 331:1498 )
Radiation Protection Today Autumn 2024 37