Editing Oil drop experiment (section)

==Background==
[[Image:Robert-millikan2.jpg|right|thumb|[[Robert A. Millikan]] in 1891|226x226px]]

Starting in 1908, while a [[professor]] at the [[University of Chicago]], Millikan, with the significant input of Fletcher,<ref>{{cite journal |last=Niaz |first=Mansoor |year=2000 |title=The Oil Drop Experiment: A Rational Reconstruction of the Millikan–Ehrenhaft Controversy and Its Implications for Chemistry Textbook |url=http://www.umich.edu/~chemstu/content_weeks/F_06_Week4/Mullikan_Erenhaft.pdf |journal=Journal of Research in Science Teaching |volume=37 |issue=5 |pages=480–508 |doi=10.1002/(SICI)1098-2736(200005)37:5<480::AID-TEA6>3.0.CO;2-X|bibcode = 2000JRScT..37..480N }}</ref> the "able assistance of Mr. J. Yinbong
Lee", and after improving his setup, published his seminal study in 1913.<ref>{{cite journal |last=Millikan |first=R. A. |author-link=Robert Andrews Millikan |title=On the Elementary Electrical Charge and the Avogadro Constant |journal=[[Physical Review]] |series=Series II |volume=2 |issue=2 |year=1913 |pages=109&ndash;143 |doi=10.1103/PhysRev.2.109|bibcode = 1913PhRv....2..109M |doi-access=free }}</ref>  This remains controversial since papers found after Fletcher's death describe events in which Millikan coerced Fletcher into relinquishing authorship as a condition for receiving his PhD.<ref>{{cite journal |first=Michael F. |last=Perry |date=May 2007 |title=Remembering The Oil Drop Experiment |journal=Physics Today |volume=60 |issue=5 |page=56 |doi=10.1063/1.2743125|bibcode = 2007PhT....60e..56P |s2cid=162256936 }}</ref><ref name="Fletcher1982">{{cite journal |first=Harvey |last=Fletcher |date=June 1982 |title=My Work with Millikan on the Oil-drop Experiment |journal=Physics Today |volume=43 |issue=6 |pages=43–47 |doi=10.1063/1.2915126|bibcode = 1982PhT....35f..43F }}</ref>  In return, Millikan used his influence in support of Fletcher's career at Bell Labs.

Millikan and Fletcher's experiment involved measuring the force on oil droplets in a glass chamber sandwiched between two electrodes, one above and one below.  With the electrical field calculated, they could measure the droplet's charge, the charge on a single electron being ({{val|-1.592|e=-19|u=[[coulomb|C]]}}).  At the time of Millikan and Fletcher's oil drop experiments, the existence of [[subatomic particles]] was not universally accepted. Experimenting with [[cathode ray]]s in 1897, [[J. J. Thomson]] had discovered negatively charged "[[Plum pudding model|corpuscles]]", as he called them, with a mass about 1/1837 that of a [[hydrogen atom]]. Similar results had been found by [[George Francis FitzGerald|George FitzGerald]] and [[Walter Kaufmann (physicist)|Walter Kaufmann]]. Most of what was then known about [[electricity]] and [[magnetism]], however, could be explained on the basis that charge is a continuous variable; in much the same way that many of the properties of [[light]] can be explained by treating it as a continuous wave rather than as a stream of [[photons]].

The [[elementary charge]] ''e'' is one of the fundamental [[physical constant]]s and thus the accuracy of the value is of great importance. In 1923, Millikan won the [[Nobel Prize]] in [[physics]], in part because of this experiment.

[[Thomas Edison]], who had previously thought of charge as a continuous variable, became convinced after working with Millikan and Fletcher's apparatus.<ref name="Bandrawal2009">{{cite book|first=Praveen Kumar|last=Bandrawal|title=Nobel Awards Winner Physics|url=https://books.google.com/books?id=iWyQcso9rskC&pg=PT169|access-date=14 December 2012|date=11 March 2009|publisher=Pinnacle Technology|isbn=978-1-61820-254-3|pages=169–}}{{Dead link|date=October 2023 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> This experiment has since been repeated by generations of physics students, although it is rather expensive and difficult to conduct properly.

From 1995 to 2007, several computer-automated experiments have been conducted at [[SLAC National Accelerator Laboratory|SLAC]] to search for isolated fractionally charged particles, however, no evidence for fractional charge particles has been found after measuring over 100 million drops.<ref name="SLAC">{{cite web|url=http://www.slac.stanford.edu/exp/mps/FCS/FCS_rslt.htm |title=SLAC – Fractional Charge Search – Results|date=January 2007 |publisher=Stanford Linear Accelerator Center |access-date=2023-10-15}}</ref>