Editing Sphere packing (section)

===Jammed packings with a low density===
Packings where all spheres are constrained by their neighbours to stay in one location are called rigid or [[Jamming (physics)|jammed]]. The strictly jammed (mechanically stable even as a finite system) regular sphere packing with the lowest known density is a diluted ("tunneled") fcc crystal with a density of only {{math|''π''{{sqrt|2}}/9 ≈ 0.49365}}.<ref>{{Cite journal | last1 = Torquato | first1 = S. | author-link1 = Salvatore Torquato | last2 = Stillinger | first2 = F. H. | title = Toward the jamming threshold of sphere packings: Tunneled crystals | journal = Journal of Applied Physics | volume = 102 | year = 2007 | issue = 9 | pages = 093511–093511–8 | doi = 10.1063/1.2802184 | arxiv = 0707.4263 | bibcode = 2007JAP...102i3511T | s2cid = 5704550 }}
</ref> The loosest known regular jammed packing has a density of approximately 0.0555.<ref>{{cite web | title=Wolfram Math World, Sphere packing | url=http://mathworld.wolfram.com/SpherePacking.html}}</ref>