Lots of press releases lately about the expansion of the Universe not accelerating. This doesn't mean there's no dark energy (whatever that may be) continuing to drive the expansion - the expansion rate seems to be more of a constant, whereas without dark energy it should be slowing down.
Or is it ? Maybe not. According to this paper it's accelerating after all. They claim that the previous authors have done a shoddy bit of statistics on the data, ignoring selection effects at different distances and other independent evidence for the acceleration. I'm not going to comment on who's right because I'm nowhere near qualified enough to judge the statistical methods, but they conclude :
Even without external constraints, this work demonstrates that a more accurate model for the supernova analysis greatly increases the significance of acceleration. We conclude that the analysis in N16 is both incorrect in its method and unreasonable in its assumptions, leading the authors to question a result that is quite secure when addressed properly.
So there.
https://arxiv.org/abs/1610.08972
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Wait... who's using which data set and who made the original sin ?
ReplyDeleteCong Ma Lordy, that's complicated.
ReplyDeleteMy knowledge of the acceleration basically starts and ends with, "some people found it by looking at supernovae in the 1990s". So, if I understand you correctly, we have these original groups (let's call them team A, collectively) and then a re-analysis by these JLA people (team B) and now some new people who think teams A and B were wrong (team C), and just to make it worse, some other new people (team D) who think team C are wrong. Teams D and C are slinging mud at each other, but with good reason, because team B (and A ?) might really have done a lousy job, but it's not clear. Is that about the long and short of it ?
But, I assume that team A can't have used any fancy machine learning or modern statistics. So where, in your view, does that leave the claims of C and D ? Is it bonkers to call in to question an established result, or could there have been some fundamental error that's been missed ?
I can explain why there is no dark energy. It begins with a question. How would you measure a speed with a reference speed.
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