Editing Casimir effect (section)

== Physical properties ==
The typical example is of two [[electric charge|uncharged]] conductive plates in a [[vacuum]], placed a few nanometers apart. In a [[classical electromagnetism|classical]] description, the lack of an external field means that no field exists between the plates, and no force connects them.<ref>{{cite journal|last1=Genet|first1=C.|last2=Intravaia|first2=F.|last3=Lambrecht|first3=A.|last4=Reynaud|first4=S.|date=2004|title=Electromagnetic vacuum fluctuations, Casimir and Van der Waals forces|url=http://aflb.ensmp.fr/AFLB-291/aflb291p227.pdf |archive-url=https://web.archive.org/web/20161003065907/http://aflb.ensmp.fr/AFLB-291/aflb291p227.pdf |archive-date=2016-10-03 |url-status=live|journal=[[Annales de la Fondation Louis de Broglie]]|volume=29|issue=1–2|pages=311–328|arxiv=quant-ph/0302072|bibcode=2003quant.ph..2072G}}</ref> When this field is instead studied using the [[QED vacuum|quantum electrodynamic vacuum]], it is seen that the plates do affect the [[virtual particle|virtual photons]] that constitute the field, and generate a net force<ref>[http://focus.aps.org/story/v2/st28 The Force of Empty Space], ''[[Physical Review Focus]]'', 3 December 1998</ref> – either an attraction or a repulsion depending on the plates' specific arrangement. Although the Casimir effect can be expressed in terms of virtual particles interacting with the objects, it is best described and more easily calculated in terms of the [[zero-point energy]] of a [[Quantum field theory|quantized field]] in the intervening space between the objects. This force has been measured and is a striking example of an effect captured formally by [[second quantization]].<ref name="Physics World">{{Cite web|url=https://physicsworld.com/a/the-casimir-effect-a-force-from-nothing/|title=The Casimir effect: a force from nothing|date=1 September 2002|work=[[Physics World]]|access-date=17 July 2009|first1=A.|last1= Lambrecht}}</ref><ref>{{cite web| url = http://www.aip.org/pnu/1996/split/pnu300-3.htm| title = American Institute of Physics News Note 1996| access-date = 28 February 2008| archive-date = 29 January 2008| archive-url = https://web.archive.org/web/20080129093425/http://www.aip.org/pnu/1996/split/pnu300-3.htm| url-status = dead}}</ref>

The treatment of boundary conditions in these calculations is controversial. In fact, "Casimir's original goal was to compute the [[van der Waals force]] between [[dipolar polarization|polarizable molecules]]" of the conductive plates. Thus it can be interpreted without any reference to the zero-point energy (vacuum energy) of quantum fields.<ref name=":0">{{cite journal|last1=Jaffe|first1=R.|author-link=Robert Jaffe (physicist)|year=2005|title=Casimir effect and the quantum vacuum|journal=[[Physical Review D]]|volume=72|issue=2|pages=021301|arxiv=hep-th/0503158|bibcode=2005PhRvD..72b1301J|doi=10.1103/PhysRevD.72.021301|s2cid=13171179}}</ref>

Because the strength of the force falls off rapidly with distance, it is measurable only when the distance between the objects is small. This force becomes so strong that it becomes the dominant force between uncharged conductors at submicron scales. In fact, at separations of 10&nbsp;nm – about 100&nbsp;times the typical size of an atom – the Casimir effect produces the equivalent of about 1&nbsp;[[atmosphere (unit)|atmosphere of pressure]] (the precise value depends on surface geometry and other factors).<ref name="Physics World"/>