  In these proceedings, we highlight experimental data (published and
preliminary) related to jet quenching and the response of the medium to this
deposited energy. Signatures in two- and three- particle hadron correlations
indicate interesting structures near the trigger particle in azimuth and over a
broad range in pseudo-rapidity, often termed "the ridge", and conical-like
structures separated in azimuth opposite to the trigger particle. We review
numerous theoretical interpretations of the ridge in particular with a critical
eye for the key properties that allow one to discriminate between, or rule out,
certain physical pictures and models (and hopefully learn something in the
process).
