In their model, the atom's recoil is caused by a light wave that travels backward in time from the atom that eventually absorbs the light...
(the atom's recoil; is caused; by a light wave; T:In their model) (a light wave; travels; backward; T:in time) (the atom; absorbs; the light; T:eventually)
the atom's recoil a light wave the atom
is caused travels absorbs
by a light wave T:In their model
backward T:in time
the light T:eventually