Double radio sources: Two approaches

The theory of double radio sources is considered from two different points of view: the so called unified models and the slingshot model. First, obser vations and theory are discussed in 11 areas: (1) the dependence or indepen dence of small-scale and large-scale jets from each other; (2) stability an d existence of large-scale jets; (3) radio hot spots inside the lobes of do uble radio sources; (4) the relation of double-lobed quasars to radio galax ies; (5) polarization and other asymmetries between the two lobes and corre lations among them; (6) the speeds of advance of radio lobes; (7) giant rad io sources; (8) one-sided double radio sources; (9) multiple-sided double r adio sources; (10) the origin of the Fanaroff-Riley classes of radio morpho logy; and (11) the origin of distance asymmetries of the radio lobes. Then five steps in building up a double radio source theory are discussed: (1) t heory of galaxy mergers; (2) theory of black hole mergers; (3) theory of bl ack hole interactions and ejections; (4) theory of radio lobe formation and evolution; and (5) radio jet theory. Finally, recent X-ray observations by ROSAT are discussed from the point of view of double radio source theory.