Three-jet event, evidence of gluons, in the JADE detector at DESY, the German particle physics laboratory in Hamburg. An electron and positron, accelerated in DESY's PETRA collider, annihilate at the centre of the cylindrical detector (seen end-on, outlined in white). Their energy rematerialises as a quark and an antiquark, one of which radiates a gluon, the carrier particle of the strong nuclear force. The quark, antiquark, & gluon instantly give rise to the three jets of particles that spray out through the detector. Events like this at DESY in 1979 gave the first visual evidence of the radiation of gluons, as predicted by the theory of the strong force.