A pitch drop experiment is a

long-term experiment A long-term experiment is an experimental procedure that runs through a long period of time, in order to test a hypothesis or observe a phenomenon that takes place at an extremely slow rate. What duration is considered "long" depends on the acad ...

which measures the flow of a piece of pitch over many years. 'Pitch' is the name for any of a number of highly

viscous The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water. Viscosity quantifies the in ...

liquids which appear solid, most commonly

bitumen Asphalt, also known as bitumen (, ), is a sticky, black, highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term a ...

, also known as asphalt. At room temperature, tar pitch flows at a very low rate, taking several years to form a single drop.

University of Queensland experiment

The best-known version of the

experiment An experiment is a procedure carried out to support or refute a hypothesis, or determine the efficacy or likelihood of something previously untried. Experiments provide insight into cause-and-effect by demonstrating what outcome occurs whe ...

was started in 1927 by Professor Thomas Parnell of the

University of Queensland , mottoeng = By means of knowledge and hard work , established = , endowment = A$224.3 million , budget = A$2.1 billion , type = Public research university , chancellor = Peter Varghese , vice_chancellor = Deborah Terry , city = B ...

Brisbane Brisbane ( ) is the capital and most populous city of the Australian state of Queensland, and the third-most populous city in Australia and Oceania, with a population of approximately 2.6 million. Brisbane lies at the centre of the South ...

, Australia, to demonstrate to students that some substances which appear solid are highly viscous fluids. Parnell poured a heated sample of the pitch into a sealed

funnel A funnel is a tube or pipe that is wide at the top and narrow at the bottom, used for guiding liquid or powder into a small opening. Funnels are usually made of stainless steel, aluminium, glass, or plastic. The material used in its construct ...

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. Large droplets form and fall over a period of about a

decade A decade () is a period of ten years. Decades may describe any ten-year period, such as those of a person's life, or refer to specific groupings of calendar years. Usage Any period of ten years is a "decade". For example, the statement that "du ...

. 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 World Expo 88, also known as Expo 88, was a specialised Expo held in Brisbane, the state capital of Queensland, Australia, during a six-month period between Saturday, 30 April 1988 and Sunday, 30 October 1988, inclusive. The theme of the Expo wa ...

. However, apparently no one witnessed the drop fall itself; Professor 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 The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water. Viscosity quantifies the int ...

of approximately 230 billion times that of

water Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as ...

. This experiment is recorded in

Guinness World Records ''Guinness World Records'', known from its inception in 1955 until 1999 as ''The Guinness Book of Records'' and in previous United States editions as ''The Guinness Book of World Records'', is a reference book published annually, listing world ...

as the 'world's longest continuously running laboratory experiment', 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 The Beverly Clock is a clock in the 3rd-floor lift foyer of the Department of Physics at the University of Otago, Dunedin, New Zealand. The clock is still running despite never having been manually wound since its construction in 1864 by Arth ...

(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 Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied o ...

. 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, John Mainstone and the late Thomas Parnell were awarded the Ig Nobel Prize in physics, a parody of the

Nobel Prize The Nobel Prizes ( ; sv, Nobelpriset ; no, Nobelprisen ) are five separate prizes that, according to Alfred Nobel's will of 1895, are awarded to "those who, during the preceding year, have conferred the greatest benefit to humankind." Alfr ...

, for the pitch drop experiment.The 2005 Ig Nobel prize winners
Improbable Research. Retrieved 6 July 2013. Mainstone subsequently commented: The experiment is monitored by a

webcam A webcam is a video camera which is designed to record or stream to a computer or computer network. They are primarily used in videotelephony, livestreaming and social media, and security. Webcams can be built-in computer hardware or peripher ...

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

. Hundreds of thousands of Internet users check the live stream each year. Professor John Mainstone died on 23 August 2013, aged 78, following a

stroke A stroke is a disease, medical condition in which poor cerebral circulation, blood flow to the brain causes cell death. There are two main types of stroke: brain ischemia, ischemic, due to lack of blood flow, and intracranial hemorrhage, hemorr ...

. Custodianship then passed to Professor Andrew White. The ninth drop touched the eighth drop on 17 April 2014; 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. In mid-March 2018, the live feed was interrupted due to technical problems in the experiment's webpage. Since mid-October 2020, the live feed is back online on the experiment's webpage.

Timeline

Timeline for the University of Queensland experiment: : After the 7th drop, air conditioning was installed, lowering the average temperature. : 12 April 2014: 9th drop touched 8th drop; 24 April 2014: 9th drop separated from funnel during beaker change.

Trinity College Dublin experiment

The pitch drop experiment at

Trinity College Dublin , name_Latin = Collegium Sanctae et Individuae Trinitatis Reginae Elizabethae juxta Dublin , motto = ''Perpetuis futuris temporibus duraturam'' (Latin) , motto_lang = la , motto_English = It will last i ...

in Ireland was started in October 1944 by an unknown colleague of the Nobel Prize winner

Ernest Walton Ernest Thomas Sinton Walton (6 October 1903 – 25 June 1995) was an Irish physicist and Nobel laureate. He is best known for his work with John Cockcroft to construct one of the earliest types of particle accelerator, the Cockcroft–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. 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 Ist or IST may refer to: Information Science and Technology * Bachelor's or Master's degree in Information Science and Technology * Graduate School / Faculty of Information Science and Technology, Hokkaido University, Japan * Graduate School ...

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.

University of St. Andrews experiment

A pitch drop experiment was begun in the same year as the Queensland experiment at the University of St. Andrews. 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.

Aberystwyth University experiment

In 2014, media reported that a pitch drop experiment had been recently rediscovered at

Aberystwyth University , mottoeng = A world without knowledge is no world at all , established = 1872 (as ''The University College of Wales'') , former_names = University of Wales, Aberystwyth , type = Public , endowment = ...

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.

Demonstrations of Lord Kelvin

In the Hunterian Museum at the

University of Glasgow , image = UofG Coat of Arms.png , image_size = 150px , caption = Coat of arms Flag , latin_name = Universitas Glasguensis , motto = la, Via, Veritas, Vita , ...

are two pitch-based demonstrations by Lord Kelvin from the 19th century. Kelvin placed some bullets on top of a dish of pitch, and

cork Cork or CORK may refer to: Materials * Cork (material), an impermeable buoyant plant product ** Cork (plug), a cylindrical or conical object used to seal a container ***Wine cork Places Ireland * Cork (city) ** Metropolitan Cork, also known as G ...

s at the bottom: over time, the bullets sank and the corks floated. Lord Kelvin also showed that the pitch flows like

glacier A glacier (; ) is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires distinguishing features, such a ...

s, with a

mahogany Mahogany is a straight- grained, reddish-brown timber of three tropical hardwood species of the genus '' Swietenia'', indigenous to the AmericasBridgewater, Samuel (2012). ''A Natural History of Belize: Inside the Maya Forest''. Austin: U ...

ramp that allowed it to slide slowly downward and form shapes and patterns similar to glaciers in the

Alps The Alps () ; german: Alpen ; it, Alpi ; rm, Alps ; sl, Alpe . are the highest and most extensive mountain range system that lies entirely in Europe, stretching approximately across seven Alpine countries (from west to east): France, Sw ...

References

External links

* * ** * {{cite web , url= https://physics.tcd.ie/tar-experiment/ , title= Trinity College Dublin Pitch Tar Drop page , publisher=

Fluid dynamics Physics experiments University of Queensland