pitch drop experiment

Image:Pitch drop experiment with John Mainstone.jpg pitch drop experiment, featuring its custodian, John Mainstone (taken in 1990, two years after the seventh drop and 10 years before the eighth drop fell).]]

The best-known version of the experiment was started in 1927 by Thomas Parnell of the University of Queensland in Brisbane, Australia, to demonstrate to students that some substances which appear solid are highly viscous fluids.{{cite journal |title=Feedback |journal=New Scientist |date=15 November 1984 |page=38|issn=0028-6664 |url=https://books.google.com/books?id=siZ1j_5wdqwC&pg=PA38 |access-date=5 May 2023 }} Parnell poured a heated sample of the pitch into a sealed funnel and allowed it to settle for three years.{{cite journal |first1=R |last1=Edgeworth |first2=B J |last2=Dalton |first3=T |last3=Parnell |title=The pitch drop experiment |year=1984 |journal=European Journal of Physics |volume=5 |issue=4 |pages=198–200 |doi=10.1088/0143-0807/5/4/003 |bibcode=1984EJPh....5..198E |s2cid=250769509 |url=https://iopscience.iop.org/article/10.1088/0143-0807/5/4/003 }} 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.{{Cite news|author=Dalton|first=Trent|date=6 April 2013|title=Pitch fever|newspaper=The Australian|url=http://www.theaustralian.com.au/news/features/pitch-fever/story-e6frg8h6-1226613215795|url-status=dead|access-date=9 July 2013|archive-url=https://web.archive.org/web/20130406075404/http://www.theaustralian.com.au/news/features/pitch-fever/story-e6frg8h6-1226613215795|archive-date=6 April 2013}} Each droplet forms and falls over a period of about a decade.

Between 1961 and 2013, the experiment was supervised by John Mainstone {{small|{{bracket|de}}}}.

The seventh drop fell at approximately 4:45 p.m. on 3 July 1988, while the experiment was on display at Brisbane's World Expo 88. However, apparently no one witnessed the drop fall itself;[https://www.newspapers.com/clip/113380954/ Just a drip – but what great timing], Sydney Morning Herald, 16 July 1988, page 3. Mainstone had stepped out to get a drink at the moment it occurred.

The eighth drop fell on 28 November 2000, allowing experimenters to calculate the pitch as having a viscosity of approximately 230 billion times that of water.{{cite web|last1=Edgeworth|first1=R.|last2=Dalton|first2=B.J.|last3=Parnell|first3=T.|title=The Pitch Drop Experiment|url=http://www.physics.uq.edu.au/physics_museum/pitchdrop.shtml|url-status=dead|archive-url=https://web.archive.org/web/20130328064508/http://www.physics.uq.edu.au/physics_museum/pitchdrop.shtml|archive-date=28 March 2013|access-date=15 October 2007|publisher=The University of Queensland Australia}}

This experiment is recorded in Guinness World Records as the "world's longest continuously running laboratory experiment",{{cite web|title=The Pitch Drop Experiment|url=http://smp.uq.edu.au/content/pitch-drop-experiment|url-status=live|archive-url=https://web.archive.org/web/20200615174548/https://smp.uq.edu.au/pitch-drop-experiment|archive-date=15 June 2020|access-date=17 August 2016|website=The University of Queensland Australia: School of Mathematics and Physics|date=6 January 2016}} and it is expected 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 the viscosity could vary throughout the year with fluctuations in temperature. Sometime after the seventh drop fell (1988), air conditioning was added to the location where the experiment takes place. The lower average temperature has lengthened each drop's stretch before it separates from the rest of the pitch in the funnel, and correspondingly the typical interval between drops has increased from eight years to 12–13 years.

In October 2005, Mainstone and Parnell were awarded the Ig Nobel Prize in physics, a parody of the Nobel Prize, for the pitch drop experiment.[http://improbable.com/ig/winners/#ig2005 The 2005 Ig Nobel prize winners]. Improbable Research. Retrieved 6 July 2013. Mainstone subsequently commented:

{{blockquote|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 the performance of a seminal scientific experiment and the conferral of such an award, be it a Nobel or an Ig Nobel prize.{{cite web |url=http://smp.uq.edu.au/content/comment-professor-mainstone |title=A Comment from Professor Mainstone |last=Mainstone |first=John |publisher=University of Queensland |access-date=5 November 2012 |url-status=dead |archive-url=https://web.archive.org/web/20121115170011/http://smp.uq.edu.au/content/comment-professor-mainstone |archive-date=15 November 2012}}}}

The experiment is monitored by a webcam{{Cite web|url=http://www.thetenthwatch.com/|title=The Tenth Watch for the ninth Pitch Drop}} but technical problems prevented the November 2000 drop from being recorded. 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.

John Mainstone died on 13 August 2013, aged 78, following a stroke.{{cite web|last=Helsel|first=Phil|date=27 August 2013|title=Professor in charge of famous 'Pitch Drop' experiment for 50 years dies waiting to see it in action|url=http://www.nypost.com/p/news/international/professor_never_charge_event_famous_AKmMGqJi1lfJ0J3xbxW8fJ|url-status=live|archive-url=https://web.archive.org/web/20200615174812/https://nypost.com/2013/08/27/professor-in-charge-of-famous-pitch-drop-experiment-for-50-years-dies-waiting-to-see-it-in-action/|archive-date=15 June 2020|access-date=27 August 2013|work=New York Post}} Custodianship then passed to Andrew White.{{Cite web|last=Calligeros|first=Marissa|date=27 August 2013|title=Pitch drop has new custodian after physicist's death|url=https://www.brisbanetimes.com.au/national/queensland/pitch-drop-has-new-custodian-after-physicists-death-20130827-2sne4.html|url-status=live|archive-url=https://web.archive.org/web/20200615174951/https://www.brisbanetimes.com.au/national/queensland/pitch-drop-has-new-custodian-after-physicists-death-20130827-2sne4.html|archive-date=15 June 2020|access-date=15 June 2020|website=Brisbane Times|language=en}}

The ninth drop touched the eighth drop on 12 April 2014;{{cite web|date=17 April 2014|title=Pitch drop touches down – oh so gently|url=http://www.uq.edu.au/news/article/2014/04/pitch-drop-touches-down-%E2%80%93-oh-so-gently|url-status=live|archive-url=https://web.archive.org/web/20200615175106/http://www.uq.edu.au/news/article/2014/04/pitch-drop-touches-down-%E2%80%93-oh-so-gently|archive-date=15 June 2020|access-date=19 April 2014|publisher=The University of Queensland Australia}}{{cite news|author=Cantor|first=Matt|date=18 April 2014|title=Big News in World's Longest Experiment, Drop of pitch falls after 13 years of waiting|work=Newser|publisher=Newser.com|url=http://www.newser.com/story/185539/big-news-in-worlds-longest-experiment.html|url-status=dead|access-date=18 April 2014|archive-url=https://web.archive.org/web/20140418191701/http://www.newser.com/story/185539/big-news-in-worlds-longest-experiment.html|archive-date=18 April 2014}}{{cite web|date=10 November 2014|title=Explainer: the pitch drop experiment|url=https://theconversation.com/explainer-the-pitch-drop-experiment-33734|url-status=live|archive-url=https://web.archive.org/web/20141213123150/https://theconversation.com/explainer-the-pitch-drop-experiment-33734|archive-date=13 December 2014|publisher=The Conversation}} however, it was still attached to the funnel. On 24 April, Professor White decided to replace the beaker holding the previous eight drops before the ninth drop fused to them (which would have permanently affected the ability of further drops to form). While the bell jar was being lifted, the wooden base wobbled and the ninth drop snapped away from the funnel.{{cite news|last1=White|first1=Andrew|last2=Baglot|first2=Julie|date=24 April 2014|title=Pitch Drop Experiment enters an exciting new era|publisher=The University of Queensland Australia|url=http://www.uq.edu.au/news/article/2014/04/pitch-drop-experiment-enters-exciting-new-era|url-status=live|access-date=25 April 2014|archive-url=https://web.archive.org/web/20200615175538/http://www.uq.edu.au/news/article/2014/04/pitch-drop-experiment-enters-exciting-new-era|archive-date=15 June 2020}}

Timeline for the University of Queensland experiment:

{{notelist-ua}}

The pitch drop experiment at Trinity College Dublin in Ireland was started in October 1944 by an unknown colleague of the Nobel Prize winner Ernest Walton while he was in the physics department of Trinity College. This experiment, like the one at University of Queensland, was set up to demonstrate the high viscosity of pitch. 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.{{cite journal | last = Johnston | first = Richard | title = World's slowest-moving drop caught on camera at last | journal = Nature | publisher = Nature Publishing Group | date = 18 July 2013 | doi = 10.1038/nature.2013.13418 | s2cid = 139012227 | url = http://www.nature.com/news/world-s-slowest-moving-drop-caught-on-camera-at-last-1.13418 | access-date = 15 March 2014}}{{cite web | title = Trinity College experiment succeeds after 69 years | publisher = RTÉ News | date = 19 July 2013 | url = http://www.rte.ie/news/2013/0717/463097-trinity-college-dublin-pitch-experiment/ | access-date = 19 July 2013}}{{cite web | last = Garber | first = Megan | title = The 3 Most Exciting Words in Science Right Now: 'The Pitch Dropped' | work = The Atlantic | date = 18 July 2013 | url = https://www.theatlantic.com/technology/archive/2013/07/the-3-most-exciting-words-in-science-right-now-the-pitch-dropped/277919/ | access-date = 19 July 2013}}

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 17:00 IST 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.

A pitch drop experiment was begun at the University of St Andrews in 1927, the same year as the Queensland experiment. No evidence has emerged of any contact between Parnell and the instigator or instigators of the St. Andrews experiment. The pitch in the St. Andrews experiment flows in a largely steady, but extremely slow, stream.{{cite web |url=https://www.uq.edu.au/news/article/1999/02/experiment-reaches-delicate-pitch |title=Experiment reaches delicate pitch |access-date=15 July 2022 }} At some stage (likely in 1984) St. Andrews professor John Allen modified the St. Andrews experiment to bring its setup closer to that of the University of Queensland experiment.{{cite journal |title=Feedback |journal=New Scientist |date=13 December 1984 |page=32 |issn=0028-6664 |url=https://books.google.com/books?id=74PgZAHPw38C&pg=PA32 |access-date=5 May 2023 }}

In 2014, media reported that a pitch drop experiment had been recently rediscovered at Aberystwyth University in Wales. Dating from 1914, it predates the Queensland experiment by 13 years. But as the pitch is more viscous (or the average temperature lower) this experiment has not yet produced its first drop and is not expected to for over 1,000 years.{{cite web|last1=Webb|first1=Jonathan|date=26 July 2014|title=Tedium, tragedy and tar: The slowest drops in science|url=https://www.bbc.co.uk/news/science-environment-28402709|url-status=live|archive-url=https://web.archive.org/web/20200615173707/https://www.bbc.com/news/science-environment-28402709|archive-date=15 June 2020|access-date=26 July 2014|website=BBC News|publisher=BBC}}{{cite web|last1=Shane D Bergin|last2=Stefan Hutzler|last3=Denis Weaire|title=The drop heard round the world|date=May 2014|url=http://physicsworld.com/cws/article/indepth/2014/may/01/the-drop-heard-round-the-world|access-date=26 July 2014}}

Another pitch-in-funnel demonstration was begun in 1902 by the Royal Scottish Museum in Edinburgh and is in Edinburgh at the Royal Scottish Museum's successor institution the National Museum of Scotland.{{cite web|url=https://www.nms.ac.uk/explore-our-collections/collection-search-results/?item_id=205915|title=Apparatus / fluidity / pitch|website=National Museums Scotland|access-date=May 5, 2023}} The known records of its behaviour are incomplete: it is known to have dripped once at some time between 4 and 6 June 2016 and on at least one occasion in the past, but the time and number of the previous drip or drips is unknown. Furthermore, the June 2016 drip happened shortly after the experiment was taken out of museum storage, and the physical movement may have caused it to drip at that time.{{cite web|url=https://www.nms.ac.uk/explore-our-collections/stories/science-and-technology/made-in-scotland-changing-the-world/scottish-science-innovations/pitch-drop-demonstration/|title=Pitch drop demonstration|website=National Museums Scotland|access-date=May 5, 2023}}

File:Kelvin pitch glacier.JPG

In the Hunterian Museum at the University of Glasgow are two pitch-based demonstrations by Lord Kelvin from the 19th century. Kelvin placed some bullets on top of a dish of pitch, and corks at the bottom: over time, the bullets sank and the corks floated.

Lord Kelvin also showed that the pitch flows like glaciers, with a mahogany ramp that allowed it to slide slowly downward and form shapes and patterns similar to glaciers in the Alps. This model was considered as an inspiration for the expected properties of luminiferous aether.{{cite journal | doi = 10.1007/s00016-006-0310-6 | title = The Physical Tourist Physics in Glasgow: A Heritage Tour | author = Johnston, S.F. | journal = Physics in Perspective | volume = 8 | pages=451–465 | year=2006| issue = 4 | bibcode = 2006PhP.....8..451J }}{{cite book | chapter-url = https://archive.org/details/scientificpapers0030unse/page/276/mode/2up?q=pitch | author = Baron Kelvin of Largs | title = Scientific Papers: physics, chemistry, astronomy, geology, with introductions, notes and illustrations - Volume XXX | year = 1910 | chapter = The Wave Theory of Light}}

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• {{cite web |url= http://smp.uq.edu.au/content/pitch-drop-experiment |title= Pitch Drop Experiment |date= 6 January 2016 |publisher= University of Queensland }}
• {{cite web |url= http://www.thetenthwatch.com/ |title= The Tenth Watch Live Webcam Feed |publisher= University of Queensland }}
• {{cite web |url= http://www.physics.uq.edu.au/physics_museum/pitch2.gif |title= Picture of the sixth drop shortly after falling in 1979 |url-status= unfit |year= 1979 |archive-date= Sep 17, 2000 |archive-url= https://web.archive.org/web/20000917202556/http://www.physics.uq.edu.au/physics_museum/pitch2.gif }}
• {{cite web |url= https://www.tcd.ie/physics/300/pitch-tar/ |title= Welcome to the National Pitch Drop |publisher= Trinity College Dublin }}

Category:Fluid dynamics

Category:Physics experiments

Category:University of Queensland