According to Penrose’s conformal cyclic cosmology, the universe goes through an infinite series of “aeons,” each of which starts with a phase resembling a big bang, then forming galactic structures as usual, then cooling down as stars die. In the end the only thing that’s left are evaporating black holes and thinly dispersed radiation. Penrose then conjectures a slight change to particle physics that allows him to attach the end of one aeon to the beginning of another, and everything starts anew with the next bang.
This match between one aeon’s end and another’s beginning necessitates the introduction of a new field – the “erebon” – that makes up dark matter, and that decays throughout the coming aeon. We previously met the erobons because Penrose argued their decay should create noise in gravitational wave interferometers. (Not sure what happened to that.)
If Penrose’s CCC hypothesis is correct, we should also be able to see some left-over information from the previous aeon in the cosmic microwave background around us. To that end, Penrose has previously looked for low-variance rings in the CMB, that he argued should be caused by collisions between supermassive black holes in the aeon prior to ours. The search for that, however, turned out to be inconclusive. In a recent paper with Daniel An and Krzysztof Meissner he has now suggested to look instead for a different signal.Sabine Hossenfelder, “Roger Penrose still looks for evidence of universal rebirth” at BackRe(Action)
Hossenfelder, who describes herself in passing as “ just a cranky ex-particle-physicist with an identity crisis,” is not a fan either of inflation or of Penrose’s conformal cyclic cosmology.
Wethinks Hossenfelder is being too hard on herself (a quality most often associated with good traits). She is, after all, looking out on a discipline that used to be associated with figures like Einstein and Bohr and is now increasingly associated with apparent crackpots.
Not that we would consider Dr. Penrose to be such. It’s more that, when crackpots dominate, a philosophical excursus like his, on the wild side, feels riskier than when they don’t.
See also: Sabine Hossenfelder: Free will is compatible with physics
Sabine Hossenfelder: Particle physics now belly up. As it happens, her book is a solid string of 1’s at Amazon
The multiverse is science’s assisted suicide