The smoot /ˈsmt/ is a nonstandard, humorous unit of length created as part of an MIT fraternity prank. It is named after Oliver R. Smoot, a fraternity pledge to Lambda Chi Alpha, who in October 1958 lay down repeatedly on the Harvard Bridge (between Boston and Cambridge, Massachusetts) so that his fraternity brothers could use his height to measure the length of the bridge.[1]

2017 Harvard Bridge Smoot measurement, Cambridge, Massachusetts.jpg
"364.4 SMOOTS ± 1 EAR" painted on the Harvard Bridge sidewalk
General information
Named afterOliver R. Smoot
1 smoot in ...... is equal to ...
   imperial/US units   ft 7 in
   SI units   1.702 m


One smoot is equal to Oliver Smoot's height at the time of the prank, 5 feet 7 inches (1.70 m).[2] The bridge's length was measured to be 364.4 smoots (2,035 ft; 620.1 m) "+/− 1 εar" with the "+/−" showing measurement uncertainty and spelt with an epsilon to further indicate possible error in the measurement.[3][4] Over the years the "+/−" portion and "ε" spelling have gone astray in many citations, including some markings at the site itself, but the "+/−" is recorded on a 50th-anniversary plaque at the bridge's end.[5]


Harvard Bridge plaque on the history of the Smoot

Oliver Smoot was selected because he was the pledge deemed shortest and "most scientifically named."[6] To implement his use as a unit of measure, Smoot repeatedly lay down on the bridge, let his companions mark his new position in chalk or paint, and then got up again. Eventually, he got tired from so much exercise and was carried thereafter by the fraternity brothers to each new position.[7][8]

Oliver Smoot graduated from MIT with the class of 1962, became a lawyer, and later became chairman of the American National Standards Institute (ANSI, 2001–02)[9] and then, president of the International Organization for Standardization (ISO, 2003–04).[1][10] He is the cousin of Nobel Prize in Physics winner George Smoot.

Public knowledge and interest in the story began when Holiday investigated the marks on the bridge years later, and published an interview with Smoot.[6] The prank's fiftieth anniversary was commemorated on October 4, 2008 as Smoot Celebration Day at MIT, which Smoot attended.[8]

In 2011, "smoot" was one of the 10,000 new words added to the fifth edition of the American Heritage Dictionary.[11][12]

A 2016 April Fools' Day article by the MIT Alumni Association announced that MIT would recalibrate the smoot to 65.7500 inches and the ear to 2.48031 inches, and bridge would thus be 372 smoots give or take 11 ears.[13]

On May 7, 2016, Oliver Smoot served as Grand Marshal of the alumni parade across the bridge, celebrating the 100th anniversary of MIT's move from Boston to Cambridge.[14]

Practical useEdit

100-smoot mark with the Charles River and Cambridge in the background

The bridge is marked with painted markings indicating how many smoots there are from where the sidewalk begins on the Boston river bank, and with a number every ten smoots.[15] The marks are repainted each semester by the incoming associate member class (similar to pledge class) of Lambda Chi Alpha.[16]

Markings typically appear every 10 smoots, but additional marks appear at other numbers in between. For example, the 70-smoot mark is accompanied by a mark for 69. The 182.2-smoot mark is accompanied by the words "Halfway to Hell" and an arrow pointing towards MIT. In recent years graduating classes have begun to paint a special mark for their graduating year.[citation needed]

The markings are recognized as milestones on the bridge, to the degree that during bridge renovations in the 1980s, the Cambridge police department requested that the markings be restored, as they were routinely used in police reports to identify locations on the bridge. The renovators at the Massachusetts Highway Department went one better, scoring the concrete surface of the sidewalk on the bridge at 5-foot-7-inch (1.70 m) intervals instead of the conventional 6 feet (1.8 m).[17] The Lambda Zeta (MIT) chapter of Lambda Chi Alpha, which created the smoot markings, continues to repaint the markings once or twice per year.[18]

Google Calculator also incorporates smoots, which it reckons at exactly 67 inches (1.7018 meter).[2] Google also offered the smoot as an optional unit of measurement in their Google Earth software and Google Maps distance measurement tool.[19] In 2014, Google introduced a new Maps interface with a measurement tool that gives distances only in miles and feet or kilometers and meters, but kept smoots as an option in Google Earth.

MIT's student-run college radio station, WMBR, broadcasts at a wavelength of 2 smoots (88.1 MHz).[20]

See alsoEdit


  1. ^ a b Curran, Susan. "Spotlight: A salute to Smoot". Massachusetts Institute of Technology. Archived from the original on June 20, 2015. Retrieved August 13, 2015.
  2. ^ a b Google: "1 smoot in inches"
  3. ^ Durant, Elizabeth (June 23, 2008). "Smoot's Legacy". MIT Technology Review. Massachusetts Institute of Technology. ... so they added the plus or minus, and wrote the e in ear as an epsilon. "The epsilon referred in a cutesy way to this error measurement," [Smoot] says. And therein lies another detail that has evolved over time: the epsilon has been lost from written accounts of the story, Smoot says, and the minus sign is often omitted as well.
  4. ^ Tavernor, Robert (2007). "Preface". Smoot's Ear: The Measure of Humanity. Yale University Press. pp. xi–xvi. ISBN 978-0-300-12492-7.
  5. ^ "Smoot in Stone". MIT News. Cambridge, Massachusetts: Massachusetts Institute of Technology. June 4, 2009. Retrieved July 20, 2010. Specifically noting the bridge's length of 364.4 Smoots (+/− 1 ear), the plaque, a gift of the MIT Class of 1962, honors the prank's 50th anniversary.
  6. ^ a b Gillooly, Patrick (September 24, 2008), Smoot reflects on his measurement feat as 50th anniversary nears, Massachusetts Institute of Technology News Office, retrieved July 10, 2020
  7. ^ Kostoulas, Andy (October 12, 1999). "This Month In MIT History". The Tech. Retrieved April 18, 2009.
  8. ^ a b MIT Celebrates 50th Smoot-aversary with Party, Volunteerism, & Plaque. Oct. 4, 2008
  9. ^ Speakers Bureau: Oliver R. Smoot, American National Standards Institute, retrieved July 10, 2020
  10. ^ ANSI Reception Honoring Oliver R. Smoot as ISO President (PDF), February 26, 2003
  11. ^ Cornish, Audie (November 13, 2011). "Looking Up Words In A Book Not So Strange Yet". National Public Radio. Retrieved December 10, 2012.
  12. ^ "American Heritage Dictionary entry". American Heritage Dictionary. Houghton Mifflin Harcourt Publishing Company. Retrieved December 10, 2012.
  13. ^ London, Jay (April 1, 2016), "MIT to Recalibrate the Smoot", Slice of MIT, MIT Alumni Association, retrieved July 10, 2020
  14. ^ Fleming, Nicole (May 7, 2016). "By land and by water, MIT celebrates 100 years in Cambridge". Boston Globe. Retrieved May 9, 2016.
  15. ^ MIT Trivia: Harvard Bridge, MIT Museum, archived from the original on August 6, 1997, retrieved July 10, 2020
  16. ^ Historic American Engineering Record (HAER) (1987). Harvard Bridge, Spanning Charles River at Massachusetts Avenue, Boston, Suffolk County, MA. Philadelphia: Department of the Interior. p. 5. Retrieved May 12, 2009.
  17. ^ Fahrenthold, David A. "The Measure of This Man Is in the Smoot". The Washington Post. Retrieved May 23, 2010.
  18. ^ Keyser describes his top five hacks - MIT News Office
  19. ^ Google Maps distance measurement tool
  20. ^ Wolfram|Alpha Can't [@wacnt] (June 13, 2017). "W|A can: WMBR frequency * smoot / speed of light" (Tweet) – via Twitter.

External linksEdit