Abstract

Astrophysics is a spectator science. The practitioner cannot go to his laboratory and do astrophysics experiments. He can only sit as a groundling in a vast audience, watching the show that Nature has staged in the heavens. Fortunately that show is sufficiently rich and varied that the scientific cycle of making hypotheses and testing them moves as rapidly in astrophysics as in sciences where laboratory experiments are possible. The universe is a large and wondrous laboratory bench on which billion year-old "experiments" are there for the observation, and new lessons are being learned every day. The most recent example of this is the recent discovery of "cosmic arcs"