Pitch drop experiment

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Not to be confused with Oil drop experiment. ‹See Tfd›
The University of Queensland pitch drop experiment, demonstrating the viscosity of bitumen.

The pitch drop experiment is a long-term experiment that measures the flow of a piece of pitch over many years. Pitch is the name for any of a number of highly viscous liquids that appear solid, most commonly bitumen. At room temperature, tar pitch flows at a very slow rate, taking several years to form a single drop.

University of Queensland experiment[edit]

The University of Queensland pitch drop experiment, featuring its then-current custodian, Professor John Mainstone (taken in 1990, two years after the seventh drop and 10 years before the eighth drop fell).

The most famous version of the experiment was started in 1927 by Professor Thomas Parnell of the University of Queensland in Brisbane, Australia, to demonstrate to students that some substances that appear to be solid are in fact very-high-viscosity fluids. Parnell poured a heated sample of pitch into a sealed funnel and allowed it to settle for three years. In 1930, the seal at the neck of the funnel was cut, allowing the pitch to start flowing. A glass dome covers the funnel and it is placed on display outside a lecture theatre.[1] Large droplets form and fall over the period of about a decade.

The eighth drop fell on 28 November 2000, allowing experimenters to calculate that the pitch has a viscosity approximately 230 billion (2.3×1011) times that of water.[2]

This is recorded in Guinness World Records as the world's longest continuously running laboratory experiment, and it is expected that there is enough pitch in the funnel to allow it to continue for at least another hundred years. This experiment is predated by two other still-active scientific devices, the Oxford Electric Bell (1840) and the Beverly Clock (1864), but each of these has experienced brief interruptions since 1937.

The experiment was not originally carried out under any special controlled atmospheric conditions, meaning that the viscosity could vary throughout the year with fluctuations in temperature. Some time after the seventh drop fell in 1988, air conditioning was added to the location where the experiment takes place. The temperature stability has lengthened each drop's stretch before it separates from the rest of the pitch in the funnel.

In October 2005, John Mainstone and the late Thomas Parnell were awarded the Ig Nobel Prize in Physics, a parody of the Nobel Prize, for the pitch drop experiment.[3]

Professor Mainstone subsequently commented:

I am sure that Thomas Parnell would have been flattered to know that Mark Henderson considers him worthy to become a recipient of an Ig Nobel prize. Professor Parnell's award citation would of course have to applaud the new record he had thereby established for the longest lead-time between performance of a seminal scientific experiment and the conferral of such an award, be it a Nobel or an Ig Nobel prize.[4]

The experiment is monitored by a webcam but technical problems prevented the November 2000 drop from being recorded.[5] The pitch drop experiment is on public display on Level 2 of Parnell Building in the School of Mathematics and Physics at the St Lucia campus of the University of Queensland. Hundreds of thousands of Internet users check the live stream each year.[1]

Professor John Mainstone died on 23 August 2013 following a stroke. He was 78.[6]

The ninth drop touched the eighth drop on 17 April 2014.[7][8] However, it was still attached to the funnel. On 24 April 2014, Pitch Drop custodian Andrew White decided to replace the beaker holding the previous eight drops before the ninth drop fused to them. While lifting the bell jar, the wooden base wobbled and the ninth drop snapped away from the funnel.[9]

Timeline[edit]

Timeline for the University of Queensland experiment:

Number of months between each drop.
Date Event Duration

(months)

Duration

(years)

1927 Hot pitch poured - -
October 1930 Stem cut 0 0.0
December 1938 1st drop fell 98 8.1
February 1947 2nd drop fell 99 8.2
April 1954 3rd drop fell 86 7.2
May 1962 4th drop fell 97 8.1
August 1970 5th drop fell 99 8.3
April 1979 6th drop fell 104 8.7
July 1988 7th drop fell 111 9.2
November 2000 8th drop fell 148 12.3
17 April 2014 9th drop touched 8th drop (156) (13.4)
24 April 2014 9th drop separated from funnel during beaker change 156 13.4

Trinity College Dublin experiment[edit]

The pitch drop experiment at Trinity College in Dublin, Ireland was started in October 1944 by an unknown colleague of the Nobel prizewinner Ernest Walton while he was in the physics department of Trinity College. This experiment, like the one at Queensland University, was set up to demonstrate the high viscosity of the material pitch, also known as bitumen or asphalt. This physics experiment sat on a shelf in a lecture hall at Trinity College unmonitored for decades as it dripped a number of times from the funnel to the receiving jar below, also gathering layers of dust.[10][11][12]

In April 2013, about a decade after the previous pitch drop, physicists at Trinity College noticed that another drip was forming. They moved the experiment to a table to monitor and record the falling drip with a webcam, allowing all present to watch. The pitch dripped around 5:00pm on 11 July 2013, marking the first time that a pitch drop was successfully recorded on camera.

Based on the results from this experiment, the Trinity College physicists estimated that the viscosity of the pitch is about two million times that of honey, or about 20 billion times the viscosity of water.

See also[edit]


References[edit]

  1. ^ a b Trent Dalton (6 April 2013). "Pitch fever". The Australian (News Limited). Retrieved 9 July 2013. 
  2. ^ Edgeworth, R., Dalton, B.J. & Parnell, T. "The Pitch Drop Experiment". Retrieved 2007-10-15. 
  3. ^ The 2005 Ig Nobel Prize Winners. Improbable Research. Retrieved 6 July 2013.
  4. ^ Mainstone, John. "A Comment from Professor Mainstone". University of Queensland. Retrieved 5 November 2012. 
  5. ^ University of Queensland page on the Pitch Drop experiment
  6. ^ "Professor in charge of famous 'Pitch Drop' experiment for 50 years dies waiting to see it in action". NY Post. Retrieved 27 August 2013. 
  7. ^ "Pitch drop touches down – oh so gently". University of Queensland. Retrieved 19 April 2014. 
  8. ^ By Matt Cantor (18 April 2014). "Big News in World's Longest Experiment, Drop of pitch falls after 13 years of waiting". Newser.com. 
  9. ^ "Pitch Drop Experiment enters an exciting new era". University of Queensland. Retrieved 25 April 2014. 
  10. ^ Johnston, Richard (18 July 2013). "World's slowest-moving drop caught on camera at last". Nature Publishing Group. Retrieved 15 March 2014. 
  11. ^ "Trinity College experiment succeeds after 69 years". RTE News, Ireland. 19 July 2013. Retrieved 19 July 2013. 
  12. ^ Garber, Megan (18 July 2013). "The 3 Most Exciting Words in Science Right Now: 'The Pitch Dropped'". The Atlantic. Retrieved 19 July 2013. 

External links[edit]