Last week Princeton hosted what seems to have been a fascinating conference, celebrating the 50th anniversary of studies of the CMB. Hopefully videos and slides will be posted, but one can get some idea of the highlights of the talks from live tweeting that was going on, that is gathered together here. The third day of the conference featured a panel where sparks flew on the topics of inflation and the multiverse, including the following:
Neil Turok: “even from the beginning, inflation looked like a kluge to me… I rapidly formed the opinion that these guys were just making it up as they went along… Today inflation is the junk food of theoretical physics… Inflation isn’t radical enough – it’s too much a patchwork. It all rests on rare initial conditions… Akin to solving electron stability with springs… all we have is proof of expansion, not that the driving force is inflation… “because the alternatives are bad you must believe it” isn’t an option that I ascribe to, and one that is prevalent now… inflation is pretty but we should encourage young to think about its problems & be creative (not just do designer inflation)
David Spergel: papers on anthropics don’t teach us anything – which is why it isn’t useful.. sometimes we need to surrender (to anthropics) but that time is not yet now.
Slava Mukhanov: inflation is defined as exponential expansion (physics) + non-necessary metaphysics (Boltzmann brains etc)… we should separate inflation from the landscape… exponential inflation is very useful, the rest [of the metaphysical stuff] is not for scientific discussion… In most papers on initial conditions on inflation, people dig a hole, jump in, and then don’t succeed in getting out… unfortunately now we have three new indistinguishable inflation models a day – who cares?
Paul Steinhardt: inflation is a compelling story, it’s just not clear it is right… I’d appreciate that astronomers presented results as what they are (scale invariant etc) rather than ‘inflationary’… Everyone on this panel thinks multiverse is a disaster.
Roger Penrose: inflation isn’t falsifiable, it’s falsified… BICEP did a wonderful service by bringing all the Inflation-ists out of their shell, and giving them a black eye.
Marc Davis: astronomers don’t care about what you guys are speculating about at all (mulitiverses, pre-big bang, etc).
I was encouraged by Steinhardt’s claim that “Everyone on this panel thinks multiverse is a disaster.” (although I think he wasn’t including moderator Brian Greene). Perhaps as time goes on the fact that “the multiverse did it” is empty as science is becoming more and more obvious to everyone.