Kmarinas,<br /><br />I find your efforts at trying to explain a very complex soup of knowns and unknowns very refreshing, compared to the very tired institutionally correct academic answers. <br /> <br />My contention, if it is that, is that galaxies such as andromeda are closer than they appear, because of intergalactic matter. It is the lack to account for the absorption of light which gives us the scale that is off, so andromeda is closer to us than we think.<br /><br />As far as thin matter giving us index, N, that we should account for, the effect is very slight. Even in our atmosphere, much much denser than ‘empty’ space, N is a very small number. Light absorption effects build over distance, whereas refractive properties may or may not.<br /><br />If you are going to account for the effects of a very small value of index , you should try to use the methods of a specialized math that can include many digits for computation.<br /><br />Another way to look at it all is the idea that it has been around far longer than we currently give credit for it, therefore many stars have used up their fuel and have cooled to the level we do not see them except through the infra-red ability we are now beginning to employ.<br /><br />Hope this helps.<br /><br />Alkalin<br />