NUCLEARPHYSICSSymmetricaltinThnsoo100Snshhavs‘doubymagnuus’hahasanquanumbofoonsandnuons.Isnowfnaysangogvusss,hanksohssnffosofnuahysss.SeeArticlep.341DANIELBAZINOnpage?341ofthisissue,Hinkeet?al.1reporthow,afteryearsofendeavour,theyhaveachievedasignificantleapforwardinthestudyoftheheaviest‘symmetri-caldoublymagic’nucleus—thetinisotope100Sn.Composedof50protonsand50neu-trons,thisnucleusisdrawingtheattentionofnuclearphysicistsaroundtheglobebecauseofitsuniquelocationinthenuclearlandscape.Nucleiarecomplexandchallengingquantumobjects.Incontrasttothestructureofatoms,forwhichthefundamentalinter-actionbetweentheelectronsandthenucleus—theelectromagneticforce—isknownwithgreatprecision,theinteractionbetweentheconstituentsofanucleus,thestrongnuclearforce,isnotsowellknown.Thisisdueinparttothecompositenatureofthenuclearconstituents,ornucleons,andthenatureofthefundamentalforcesthatbindnucleonstogether(quantumchromodynamicsandtheelectroweakforce).Asfarasweknow,nucleiarethesmallestobjectsthatcanbesplitupintotheirconstitu-ents.Theyarethereforethesmallestentitiesinwhichemergentproperties—patternsthatarisefromcomplexity—canbestud-ied.Nuclearscientistsstudytheseemergentphenomenaandareusingthemtodecipherthenatureofthenuclearforce.Magicnum-bersarenumbersofprotonsorneutronsthatformfullshellsinanatomicnucleus,andareperhapstheforemostemergentpropertyofnuclei.ThoughttohavefirstbeencoinedbythephysicistEugeneWigner,thetermreflectstheunexpectedshellstructureofnuclei,asopposedtotheliquid-likebehaviourexpectedforsuchdenselypackedandstronglyinter-actingobjects.Infact,theindependentparticlemodelusedtodescribeatoms,inwhichelectrons(theparticles)areassumedtomoveindependentlyofeachother,alsoworksremarkablywellfornuclei.Themodelhasbeenabletoexplain—atleastforstablenuclei2—theobservedsequenceofmagicnumbers:2,8,20,28,5