Wednesday, February 25, 2009

Gravitation and non-progress

Gravitation has and probably always will be my area of interest so I have nothing constructive to say about particle physics. However, there is an analogy between the lack of progress in particle physics in recent years, and gravitation in recent years.

All the major work in general relativity stopped being done in the 60's and 70's, and that is only if you consider the singularity theorems and such by Hawking & Penrose to be part and parcel of the subject. Sure there have been refinements in the past 40 years and the occasional highly interesting bit of work [eg, Teutolsky's black hole bomb: [ hep-th/0404096 ] here and there, but I consider the subject roughly 'done'. That's why MTW - even though it was written near 40 years ago - is still the definitive book on the subject. Or why I

There have been the occasional branchings-out through things like Einstein-Cartan theory which have zero practical hope of experimental testing, and the pointless wandering of the thousand string theories, loop quantum gravity, etc. Nobody has accomplished fuck-all in all this time, even to the point of predicting simple Newtonian gravitation from the constructs.

In the past 40 years, folks have been trying Really Really Hard(tm) to break GR. My lifetime plus a few decades of lunar ranging has put some amazing constraints on alternative theories, and shown us exactly nothing that can't be taken care of by GR. More interesting and useful results like the handful of strong-field tests of GR via binary systems haven't put up anything special despite 30 years of trying [ astro-ph/0407149 ] in one particular example.

More recent fun stuff consists of dark matter, but it looks like GR can take care of that as well - protestations from the peanut gallery notwithstanding.

In fact, I don't see any serious challenge to GR existing right now. Cosmology is more of a challenge to particle physics than it is to GR. Dark matter has confused the bejezus out of the particle physics crowd, and there is that 100-or-so order of magnitude difference on the vacuum energy density [that GR correctly describes].

Sometimes I think gravitation just might not be quantizable and that's the correct way of looking at things. We'll see.

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