spherical cow

The phrase comes from a joke that spoofs the simplifying assumptions sometimes used in theoretical physics.{{Cite web|url=https://www.washingtonpost.com/news/wonk/wp/2013/09/04/the-coase-theorem-is-widely-cited-in-economics-ronald-coase-hated-it/|title=The Coase Theorem is widely cited in economics. Ronald Coase hated it.|first=Timothy B.|last=Lee|date=September 4, 2013|newspaper=The Washington Post}}

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| Milk production at a dairy farm was low, so the farmer wrote to the local university, asking for help from academia. A multidisciplinary team of professors was assembled, headed by a theoretical physicist, and two weeks of intensive on-site investigation took place. The scholars then returned to the university, notebooks crammed with data, where the task of writing the report was left to the team leader. Shortly thereafter the physicist returned to the farm, saying to the farmer, "I have the solution, but it works only in the case of spherical cows in a vacuum."

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John Harte, who received his Ph.D. from the University of Wisconsin in 1965,{{cite web|url=https://ourenvironment.berkeley.edu/people/john-harte|title=John Harte |website= ESPM UC Berkeley Rausser College of Natural Resources |accessdate=April 4, 2018}} reported that he first heard the joke as a graduate student.{{cite book | first=John | last=Harte | author-link=John Harte (scientist) | title=Consider a Spherical Cow: A Course in Environmental Problem Solving | chapter=Preface | publisher=William Kaufmann | publication-place=Los Altos | year=1985 | isbn=0-86576-086-1 | chapter-url=https://archive.org/details/considerspherica00hart/page/n13 | page=xiii }} One of the earliest published references is in a 1970 article by Arthur O. Williams Jr. of Brown University, who described it as "a professional joke that circulated among scientists a few years ago".{{cite book | editor-first=R. W. B. | editor-last=Stephens | first=A. O. | last=Williams Jr. | chapter=Normal-mode Methods in Propagation of Underwater Sound | title=Underwater Acoustics | year=1970 | publisher=Wiley-Interscience | isbn=0471822043 | page=25 | chapter-url=https://archive.org/details/underwateracoust0000step/page/25 }}

The story is told in many variants,{{cite web |url=http://www.physics.csbsju.edu/stats/WAPP2_cow.html |title = Spherical Cow: A Simple Model |access-date = 2007-02-19 |last = Kirkman |first=T. W. |year = 1996 |work=Statistics to Use }} including a joke about a physicist who said he could predict the winner of any race provided it involved spherical horses moving through a vacuum.{{cite book |last1=Mager |first1=Birgit |last2=Evenson |first2=Shelley |editor-last1=Hefley |editor-first1=Bill |editor-last2=Murphy |editor-first2=Wendy |chapter=Art of Service: Drawing the Arts to inform Service Design and Specification |title=Service science, management and engineering: education for the 21st century |chapter-url={{GBurl|Z1i2NctCbDEC|pg=PA80}} |doi= 10.1007/978-0-387-76578-5_12 |access-date=28 September 2011 |date=1 February 2008|publisher=Springer |isbn=978-0-387-76577-8|page=80}}{{cite book |last=Birattari |first=Mauro |title=Tuning Metaheuristics: A Machine Learning Perspective |chapter=Some Considerations on the Experimental Methodology |chapter-url={{GBurl|PutOdA2kc0kC|pg=PA183}} |series=Studies in Computational Intelligence |access-date=1 September 2012|date=15 April 2009|volume=197 |publisher=Springer |doi=10.1007/978-3-642-00483-4|isbn=978-3-642-00482-7|pages=183–184}} A 1973 letter to the editor in the journal Science describes the "famous story" about a physicist whose solution to a poultry farm's egg-production problems began with "Postulate a spherical chicken".{{cite journal |last=Stellman |first=Steven D. |title=A Spherical Chicken |journal=Science |date=1973-12-28 |volume=182|issue=4119|page=1296|doi=10.1126/science.182.4119.1296.c |pmid=17733092|s2cid=29103654 |url=https://www.science.org/doi/10.1126/science.182.4119.1296.c |access-date=18 Feb 2017|url-access=subscription }}

File:Spot the cow.gif of a homotopy from a spherical cow to a more typical one]]

File:Approksimoidaan pyöreä lehmä.jpg for "We approximate a spherical cow").]]

The concept is familiar enough that the phrase is sometimes used as shorthand for the entire issue of proper modeling. For example, Consider a Spherical Cow is a 1985 book about problem solving using simplified models. A 2015 paper on the systemic errors introduced by simplifying assumptions about spherical symmetries in galactic dark-matter haloes was titled "Milking the spherical cow – on aspherical dynamics in spherical coordinates".{{cite journal |last1=Pontzen |first1=Andrew |first2=Justin I. |last2=Read |first3=Romain |last3=Teyssier |first4=Fabio |last4=Governato |first5=Alessia |last5=Gualandris |first6=Nina |last6=Roth |first7=Julien |last7=Devriendt |title=Milking the spherical cow – on aspherical dynamics in spherical coordinates |journal=Monthly Notices of the Royal Astronomical Society |date=1 August 2015 |volume=451 |issue=2 |pages=1366–1379 |doi=10.1093/mnras/stv1032 |url=https://academic.oup.com/mnras/article/451/2/1366/987342 |access-date=6 December 2022 |doi-access=free|arxiv=1502.07356 }}

References to the joke appear even outside the field of scientific modeling. "Spherical Cow" was chosen as the code name for the Fedora 18 Linux distribution.{{cite web |url=https://www.phoronix.com/news/MTA5NDk |title=Fedora 18 Is Codenamed The Spherical Cow |first=Michael |last=Larabel |access-date=2023-06-06 |date=2012-05-01 |website=Phoronix}} In the sitcom The Big Bang Theory, a joke is told by Dr. Leonard Hofstadter with the punchline mentioning "spherical chickens in a vacuum", in "The Cooper-Hofstadter Polarization" episode.{{cite news |last=Huva |first=Amy |title=When nerds go viral |work=Earth Matters |publisher=The Vancouver Observer |url=http://www.vancouverobserver.com/blogs/earthmatters/when-nerds-go-viral|archive-url=https://web.archive.org/web/20191205034821/http://www.vancouverobserver.com/blogs/earthmatters/when-nerds-go-viral |archive-date=2019-12-05 |url-status=dead}} In the space gravity simulator educational video game Universe Sandbox, a spherical cow was added as a user-placeable object in March 2023.{{Cite web |date=2023-03-23 |title=A Comet, an Asteroid, and a Planet Walk into the Solar System {{!}} Update 32.2 |url=https://universesandbox.com/blog/2023/03/comet-asteroid-planet-solar-system/ |access-date=2023-03-27 |website=Universe Sandbox}}

• Assume a can opener, a joke about invalid assumptions in economics
• Amorphous globosus, a rare and fatal birth defect in cattle, producing a ball of underdeveloped tissue
• Fermi problem, efforts to produce very broad estimates
• Homo economicus, a hypothetical rational person
• Naïve physics, also called folk physics
• Schwarzschild metric, an exact solution of the Einstein field equations assuming a uniform spherical symmetric nonrotating uncharged mass in a vacuum

{{reflist|30em}}

• [https://web.archive.org/web/20130104054509/http://imagine.gsfc.nasa.gov/docs/features/topics/snr_group/spherical_cow.html NASA:Exploration of the Universe Division – Supernova models as spherical cows]
• [http://heritage.stsci.edu/1999/16/votepplfull.html Hubble Heritage Gallery Page]: related history from Space Telescope Institute

Category:Humour in science

Category:In-jokes

Category:Metaphors referring to cattle

Category:Scientific modelling

Category:Theoretical physics