User talk:Jemanuel-h

Statistical paradox is described in a couple of books by Isaac Asimov:

Asimov's Guide to Science Vol 1 The Physical Sciences page 34 mentions the method

The Universe page 83 (or see Hertzsprung in the index) describes the method

So far as I understand it, the technique involves measuring a star's radial velocity from its red or blue shift. Also its proper motion is measured, that is, its angular velocity across the sky. It is assumed that, on average, a star's transvers velocity would equal its radial velocity. Then, Transverse velocity / angular velocity = distance

I think that Ejnar Hertzsprung used a cluster similar to the Pleiades and averaged the distances which the above calc gave for a selection of its stars, comprising or including many Cepheids. This gave the distance to some Cepheids which allowed calibrating the Leavitt curve to obtain a yardstick for astronomy which led to understanding the true vastness of the skies starting with Shapley and globular clusters/Milky Way centre, and culminating in Hubble/Andromeda and recognition that the nebulae were galaxies. Later, Harlow Shapley did this for many Cepheids, and plotted a luminosity/period graph. It came out very smooth, which seemed to validate the statistical parallax method. I don't know the details, not even whether he just selected Cepheids at random or chose ones in a cluster.

Statistical parallax was necessary because the closest Cepheid, Polaris, was, with telescopes of that time, out of range of ordinary stellar parallax determinations and its distance could not be so found.

Hope this helps, please let me know if I'm wrong or not clear.

I love Asimov's books for many other reasons. Douglas R Wilson (talk) 08:11, 22 February 2017 (UTC)