A couple of things to start with. I'm going to put forward some questions I need help understanding surrounding VSL. I'm not anti-LCDM or against inflation/etc. I'm just interested in the mechanisms of setting up a 'new' theory (I'm aware Einstein delved into VSL, and subsequently disregarded, whilst formulating GR). I'm also a finishing undergraduate student. Whilst I have some questions of my own, I would greatly appreciate input of any kind - questions of your own (not necessarily things you don't know, just things about the theory I should look up on my own - problems/inconsistancies etc.) or even just reasons you would disregard the possibility. My purpose isn't to find out whether VSL is correct or not, I'm more interested in why there seems to be such a mass popularity for LCDM (I know the definition of standard theory would be one that is accepted by most people) and if the reasons for the rejection of alternatives like VSL is purely scientific or holds some tranditional bias as well. -------- I'll start off with the possibility of a varying-fine-structure constant (alpha). I don't know what the current stance is, and I'm trying to catch up on years of papers but from what I've seen: - There are four main methods to investigate a changing alpha. - Three of these methods have yeilded 100%+ error bars, so are inconclusive. The fourth (J.D. Barrow) looks for small changes in the absorption of quasar light by gas clouds between us and the subject. The separation of different lines is analysed, allowing any combination of lines to be investigated meaning there should be a good chance for accuracy and precision. (The main advantage seems to be that we can predict where the spectral lines should be if alpha is varying, so if we find the lines in these new, adjusted positions then...) I would like to know if there has been any recent papers on this subject, or anything anyone feels is particularly noteworthy about this method. Secondly, VSL interprets the possibility of a varying alpha as a varying of the inverse of the square of the speed of light. Lorentz invariance and covariance is broken - which I assume means there is a preferred frame for the formulation of physical laws? Is this valid? and if so, what physical meaning does it have? Also, Inflation seems to violate the strong energy condition - and VSL violates Lorentz invariance. Is there any reason either of these two violations would be preferable? ---- There are a couple of problems with VSL I'd like to discuss also: There is a well known issue with conservation of energy (I assume this is still present, I've managed to only digest a handful of papers on the subject and am grateful of any guidance) since it depends on the speed of light. Is, quite simply, conservation of energy violated? or is there another mechanism to avoid this? In fact, is there any reason to even assume that conservation of energy should apply to the whole Universe over vast periods of time? And, just quickly, there's a small part in (J.D Barrow; Physical review D, Vol 59, 043515) about a problem with black holes. The issue lies with the raduis of a black hole - which depends on the speed of light. Differentiating R to find a rate of change when including a varying C shows that if c is falling (as required to solve the horizon, flatness etc) then the radius of blackholes will increase significantly as the Universe ages. I am grateful for any input on this subject, be it problems that I might not be considering or general thoughts.