The universe appears "old", but it is still less than 10,000 years old

[Optimistic Mysanthrope]

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You are viewing a very narrow description of the problem of assessing isotropy of speed of light. It is true we can't directly measure one way speed of light when the light is aimed directly at us without clock synchronization. But we do have overwhelming evidence that one way speed of light is isotopic when the light is shining out from a cosmic event in every direction except pointed directly at us. This comes from observation of type II supernova. In the hundreds of thousands of years before going bang the supernova's progenitor star usually shed substantial amount of its outer layers in a series of minor cataclysms. This results in a Russian doll like layered expanding spherical shells of gas surrounding the progenitor star that we can observe in the form of planetary nebula. When the star does go supernova the massive pulse of light from the supernovae would reach out from the epicenter in all directions at speed of light, and successively hit each shell, heat them, and cause them to glow intensely. We can use just our own clock to see exactly how long after the instant of supernova explosion the outward racing light from the nova hits each point in each shell surrounding the supernova. And you know what, each point on each in the cross section of the spherical shell light up at almost the same time, to within the difference fully accountable by the know minor deviation from perfect sphericality of the gas shells. The different shells light up in succession precisely according to the shell's radius and this distance from the origin of supernova light at its center. You know what, the results show the successive shells become excited by the light from supernova at precisely the times predicted if light from supernova moves out in every direction at exactly the know universal speed of light C.

So this tells us with certainty without any spectacular special pleading assumption that light emanating from cosmic sources travels isotropically at C without requiring any special, tailored synchronization between the clocks at each point on each shell. Only one master clock at the observer is necessary.

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Cool, that's really interesting. Cheers for posting that

I'm not sure exactly how positional time dilation (I can't be arsed to keep typing that so I'll just refer to it as PTD from now on) would apply in this situation off the top of my head, but I think it works against ASC (for reasons that I mentioned briefly earlier).

You can explain the phenomena using ASC quite easily, though I think you can only do it if you abandon the idea of a universe that is < 10,000 years old. This is because in order to invoke PTD, it also has to be factored in for the distance between the phenomena and the point of observation (i.e. Earth). Now this would result in a transit time relative to us that is substantially longer than 10,000 years.

Now like I said, this is just off the top of my head. Statler has mentioned that Lisle has used a "time-zone" analogy to explain some if this. I've been unable to find Lisle's explanation myself, so I'm unable to comment on it. Lisle may well be able to adequately explain away such discrepancies. I suspect that such an explanation would involve a reduced PTD in interstellar space, which would raise problems of it's own, but until I know more I really can't say.

Hopefully Statler can provide me with a bit more info on it (hint hint )

I'd like to move on to discussing other aspects of YEC, but I'm enjoying this topic far too much to cut it short