I was amazed when Draine and Lazarian said this in 1998, because that speed seemed unimaginable. But a great thing about science is we can make models with observable predictions, compare with observations, and reject an idea or not based on statistics rather than gut feelings. So far, the spinning dust model looks good!

By the way, others (e.g. Hirata, Ali-Hamoud, Dickinson, Ysard, Verstraete, Hoang, …) have verified and extended the Draine & Lazarian calculation over the years. A few minor errors were found in the original calculation, but they change the answer little. At this point, microwave emission from spinning dust is well established and widely accepted.

I got the grain size from http://arxiv.org/pdf/1105.2302v3.pdf . It’s interesting they talk about 40 GHz rotation rates, which puts the above BOTE stress estimate right at but not beyond the tensile strength of rock.

Alex: The phone call with Amber prompted me to look into this, but then I spent months working alone on the problem. I am grateful for the suggestion, and acknowledged her in the paper in addition to several other people who had helpful suggestions along the way.

Marshall Eubanks: Yes, “was superseded” is a nice way to say “rejected.” The estimate of the total power requires extrapolating the spectrum far beyond where it is observed, and is therefore quite uncertain. We stuck to an empirical statement about the surface brightness in Hooper et al. (2007).

Yudong: I agree! See the “Fermi jet” paper by Meng Su and myself. http://arxiv.org/abs/1205.5852

Baby Bones: I don’t have a good answer. The Sun does indeed have a charge (electrons get away more easily, so the net charge is slightly positive) as do galaxies and galaxy clusters. Someone has calculated these charges and they are too small to have observable consequences for dynamics. But it is a good idea!

martenvandijk: We actually hope that x-ray data from eRosita can teach us more about the thermal part of the spectrum. The cosmic ray part is non-thermal (no well defined temperature).

Bob and Bobby: I like the other quotes. Francis Bacon would have been especially appropriate, but it was Burr’s quote I saw so many times on the wall.

Thanks, everyone!

You of all people could set me straight on a certain issue. It is this: I have confidence that general relativity works, and is a macroscopic theory, but I see no reason why not a cosmological constant term for an accelerating expansion of the universe must have a mysterious source. Couldn’t such a term simply be an effective contribution from other forces that aren’t reasonably represented as space time curvatures? Why not suppose that inverse Compton scattering of electrons leads to a positive charge accumulating on galaxies and a corresponding but much more diffuse negative charge accumulating in intergalactic space, some of which appears as Fermi Bubbles around every galaxy. In so doing, the positively charged galaxies would be like screened positive charges of condensed matter physics and be pushed away from each other. The source of “dark” energy could then be traced back to the nuclear fusion of stars. After all, the acceleration we see today didn’t seem to appear until after the dark era, and it seems to coincide with stellar formation (or as best as I can tell from looking at illustrations of universal expansion).