Saturday, 31 May 2014

Theory vs. Observations, by Jean-Claude Pecker

A cartoon by the famous French astronomer Jean-Claude Pecker (published in the Proceedings of the 3rd European Solar Meeting, "Solar activity, April 13-15 1981, Oxford", ed. C. Jordan; a non-ADS volume).


No matter how much we pushed the frontier of the science and how much our theoretical machinery, diagnostic tools and large and expensive gadgets evolve, this is still in a way very actual. It is important not to forget that even the most sophisticated realistic 3D models of the sun are still mammals, pardon, models. On the other hand, the results of the observations should not be consider  as the real "elephant" either. They are pictures of the elephant made with imperfect instruments!


Well, it has to be said that these pictures are indeed extremely advanced as they extend with high resolution in the observational 2D plane, but also in the time and in the energy of the incoming radiation and more and more often they even come in the four flavors of the polarization! These super 5D movies - observed and synthesized from the realistic simulations - are exactly where we are looking to get the good match between our theories and the real Sun.

Continuing the analogy with the hierarchy of the biological classification, we are certainly beyond the stage where we get a good match of the observed and the theoretical "class" (as the cartoon suggests) for the Sun. The life is obviously the Universe. The domain are the stars. The kingdom corresponds to the stars of the main sequence, the normal stars. The phylum of the Sun would be G2K spectral type. The class is the magnetically active star. Further classification would be too ambiguous. In any case with the realistic 3D models we certainly get an unprecedentedly detailed knowledge of the fine details of the skin, the hair and the internal organs of our Sun-mammal. Still we need further improvements in both the models and the observations to understand fully its nature, its activity cycles and how does it influence the Earth.


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