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Originally Posted by Ken G
That depends on how certain we are of the 84, and the 13 Gyr. In the past neither number has been very firm, so conflicts were tolerated. Now we have 72 for H_o at a level that should be much more certain than in the past, so changing it to 84 is kind of a cheat-- that very change would be intolerable because it would mean much of experimental science is unreliable. We'd have to go completely back to the cosmology drawing board, it would go way beyond just the age of the universe.
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I wouldn't say it's a cheat. First and foremost, I was trying to illustrate how numbers can be tweaked when certain observational results are used as constraints. Some people have a problem with tweaking and I thought the example illustrated nicely how tweaking can be scientific.
Second, H0=84 is still plausible. To explain would be beyond the scope of this thread.
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Considering this to be a hypothetical example, or perhaps an example from the history of cosmology where the numbers were less well established, this would not be an intolerable conflict and indeed was not intolerable. But again, that's because it isn't just the nature of the conflict itself that adds to intolerability, it is the reliability of the observations. Observations have statistical and systematic errors, so in effect, they are subject to "tweaking" as well!
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And this is precisely why the subject of an observational value in cosmology is subject to revisitation. For example,
van Leeuwen et al have recently shown that the Cepheid distance scale needs a minor revision that pushes the HKP final H0 from 72 to 76.
Consider also that the Muzzin et al study on the matter density is a newer study that gives nearly the same value as the Carlberg et al study, but the uncertainty now is reduced from +/- 0.05 to +/- 0.02. That makes a difference when one considers the impact if the value of H0 was to be revised upward to 84.
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Indeed, and the fact that H_o is not 84 is then a way to show that modern cosmology is indeed expertly falsifiable (if not naively so), yet is instead supported.
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I'd say that whether H0=84 or not the example I used illustrated that the model is falsifiable.