With the death of this gifted but contentious astronomer on December 28th, a controversial ideology concerning redshifts and the expansion of the universe has come to a quiet end.A half century ago, astronomers affiliated with Hale Observatories in California were recognized as accomplished, respected members of the community. Halton C. Arp was one such researcher. A staff astronomer at the esteemed institution for 29 years, he excelled as an observer and had frequent access to the 5-m Hale Telescope on Palomar Mountain.
Yet beginning in the mid-1960s, Arp became convinced that the spectral redshifts of all distant galaxies, indicating their rapid movement away from us and thus showing that the universe is expanding, were not what they seemed. He identified many tantalizing pairings, such as galaxies and quasars apparently intertwined in space, with seriously mismatched redshifts. To him, this meant that we just didn't understand redshifts. Others dismissed the couplings as optical illusions or chance alignments.
But "Chip" Arp, a champion fencer in his youth, remained stubbornly convinced. The "redshift debate" heated up in 1966, when he published a compendium of 338 such cosmic oddities in his Atlas of Peculiar Galaxies. Six years later, on December 30, 1972, Arp squared off in an extraordinary live debate with Princeton cosmologist John Bachall, and their extended back-and-forth salvos became the basis of a book, The Redshift Controversy, published the next year.With time, as evidence mounted supporting the Big Bang, Arp's contention was seen as less and less credible. Eventually he was no longer allotted observing time on the world's big telescopes, and he retired from the Hale staff to join the Max Planck Institute for Astrophysics near Munich, Germany. It's in Munich that he died, at age 86, on December 28th.
For more details about Arp's career and his controversial ideas, check out Dennis Overbye's detailed obituary for the New York Times.